METHOD FOR DETECTING THE SPIN OF A BALL IN MOTION, VIRTUAL GOLF DEVICE AND VIRTUAL GOLF SYSTEM USING THE SAME

Abstract

Disclosed in a method for detecting the spin of a ball in motion, a virtual golf device and a virtual golf system using the same. The method for detecting the spin of the ball in motion comprises an image acquisition step of acquiring a first image of the ball at a first time and acquiring a second image of the ball at a second time, the ball being in motion with spin and having an identifier, an identification information acquisition step of acquiring first identification information of the identifier from the first image and acquiring second identification information of the identifier from the second image, and a spin detection step of determining an estimated spin by using cumulative spin data, and applying the estimated spin to the first and second identifier information to detect the spin of the ball in motion.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Korean Patent Application Nos. 10-2023-0098905, 10-2023-0098913 and 10-2023-0098917 filed on Jul. 28, 2023, and all the benefits accruing therefrom under 35 U.S.C. § 119, the contents of which in its entirety are herein incorporated by reference.

BACKGROUND

1. Field

The present invention relates to a method for detecting the spin of a ball in motion and a virtual golf device and a virtual golf system using the same.

2. Description of the Related Art

Recently, as the golf population has increased, screen golf, which allows users to play golf using a virtual golf device, has become popular. In screen golf images of a golf course are displayed through a screen. Therefore, it can give the feeling of playing a real golf game outside, and time and money can be saved in comparison with the play at an outdoor field. As a result, screen golf is very popular among busy modern people who have difficulty in playing a real outdoor golf due to time or economic reasons, etc.

When comparing screen golf with real golf, screen golf is played in an indoor closed space and can provide users with technical services that are impossible for real golf played in an outdoor open space. For example, in real golf, when a user hits a golf ball, it is impossible to detect the physical state of the golf ball such as the speed or launch angle of the hit golf ball, but in screen golf, it is possible to detect the physical state of the hit golf ball by using a plurality of sensing means and provide the same to the user. The physical state of the golf ball to which the user pays the most attention is the ‘spin’ of the golf ball. The spin represents the rotational state of the golf ball that rotates in a 3-dimensional space, and to detect the spin, expensive sensor is needed. However, because it is economically inefficient to use expensive equipment to detect the spin, there is a need for development of technology to accurately detect the spin at a low cost.

SUMMARY

In order to solve the above-mentioned problems, the present invention provides a method for detecting the spin of a ball in motion in a simple and straightforward way without expensive equipment.

The present invention provides a virtual golf device for detecting the spin of a golf ball hit by a user in a simple and straightforward way without expensive equipment.

The present invention provides a virtual golf system for detecting the spin of a golf ball hit by a user in a simple and straightforward way without expensive equipment.

The other objects of the present invention will be clearly understood with reference to the following detailed description and the accompanying drawings.

In order to achieve the above-mentioned objects, a method for detecting the spin of a ball in motion according to an embodiment of the present invention comprises an image acquisition step of acquiring a first image of the ball at a first time and acquiring a second image of the ball at a second time, the ball being in motion with spin and having an identifier, an identification information acquisition step of acquiring first identification information of the identifier from the first image and acquiring second identification information of the identifier from the second image, and a spin detection step of determining an estimated spin by using cumulative spin data, and applying the estimated spin to the first and second identifier information to detect the spin of the ball in motion.

In the method for detecting the spin of the ball in motion, the ball is a golf ball, and as a user hits the golf ball with a golf club, the golf ball moves with spin, and the cumulative spin data is formed using information associated with the spin of the golf ball when the user who hits the golf ball of which the spin is currently to be detected and other users having a same golf skill level as the corresponding user have played golf in the past.

In the method for detecting the spin of the ball in motion, the ball is a golf ball, and as a user hits the golf ball with a golf club, the golf ball moves with spin, the method further comprises detecting a state change by the motion of the golf ball between the first time and the second time, and after spin data corresponding to the state change of the golf ball is determined, the cumulative spin data is formed using the determined spin data.

In the method for detecting the spin of the ball in motion, in the spin detection step, a result of applying the estimated spin to the first identification information is compared with the second identification information, and according to a result of comparing with the second identification information, the estimated spin is determined as the spin of the ball in motion or a new estimated spin is determined and the spin detection step is performed again.

In the method for detecting the spin of the ball in motion, the cumulative spin data exhibits a Gaussian distribution, and the estimated spin includes a plurality of estimated spins determined by extracting a plurality of random spins differently located in the Gaussian distribution.

In the method for detecting the spin of the ball in motion, the cumulative spin data exhibits a Gaussian distribution, and the estimated spin is initially determined in a range between a minus (−) standard deviation and a plus (+) standard deviation with respect to a mean in the Gaussian distribution.

In the method for detecting the spin of the ball in motion, the new estimated spin is determined such that with an increasing value of the result of comparing the result of applying the estimated spin to the first identification information with the second identification information, a difference between the estimated spin and the new estimated spin increases.

The method for detecting the spin of the ball in motion further comprises performing additional steps including a step of acquiring a third image of the ball at a third time, a step of acquiring third identification information of the identifier from the third image, and a step of verifying the detected spin by using the third identification information.

In the method for detecting the spin of the ball in motion, the spin detected in the spin detection step includes a plurality of spins, and the result of applying the plurality of spins to the first identification information or the second identification information is compared with the third identification information, and according to a result of comparing with the third identification information, any one of the plurality of spins is definitely determined as the spin of the ball in motion or a new estimated spin is determined and the spin detection step and the additional steps are performed again.

A virtual golf device according to an embodiment of the present invention comprises a calculation unit to perform a calculation process of calculating a motion of a virtual golf ball corresponding to a real golf ball when a user hits the real golf ball, and a display unit to display a virtual golf course and the virtual golf ball moving in the virtual golf course as calculated in the calculation process, wherein the virtual golf device detects the spin of the real golf ball after the user hits the real golf ball by a method for detecting the spin of a ball in motion including an image acquisition step of acquiring a first image of the ball at a first time and acquiring a second image of the ball at a second time, the ball being in motion with spin and having an identifier, an identification information acquisition step of acquiring first identification information of the identifier from the first image and acquiring second identification information of the identifier from the second image, and a spin detection step of determining an estimated spin by using cumulative spin data, and applying the estimated spin to the first and second identifier information to detect the spin of the ball in motion.

In the virtual golf device, the calculation process reflects a result of detecting the spin of the real golf ball.

A virtual golf system according to an embodiment of the present invention comprises a service device and at least one virtual golf device connected to the service device via communication, wherein the virtual golf device includes a calculation unit to perform a calculation process of calculating a motion of a virtual golf ball corresponding to a real golf ball when a user hits the real golf ball, and a display unit to display a virtual golf course and the virtual golf ball moving in the virtual golf course as calculated in the calculation process, and wherein the virtual golf device detects the spin of the real golf ball after the user hit the real golf ball by a method for detecting the spin of a ball in motion including an image acquisition step of acquiring a first image of the ball at a first time and acquiring a second image of the ball at a second time, the ball being in motion with spin and having an identifier, an identification information acquisition step of acquiring first identification information of the identifier from the first image and acquiring second identification information of the identifier from the second image, and a spin detection step of determining an estimated spin by using cumulative spin data, and applying the estimated spin to the first and second identifier information to detect the spin of the ball in motion.

In the virtual golf system, the service device includes a storage unit to store user information, and the user information is used to form the cumulative spin data during the detection of the spin of the real golf ball.

According to the present invention, it is possible to accurately detect the spin of a ball in motion in a simple and straightforward way without expensive equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a workflow diagram of a method for detecting the spin of a ball in motion according to an embodiment of the present invention.

FIGS. 2 to 7 are diagrams showing each step of the method for detecting the spin of the ball in motion of FIG. 1.

FIG. 8 is a workflow diagram of a method for detecting the spin of a ball in motion according to another embodiment of the present invention.

FIGS. 9 to 13 are diagrams showing each step of the method for detecting the spin of the ball in motion of FIG. 8.

FIG. 14 is a workflow diagram of a method for detecting the spin of a ball in motion according to another embodiment of the present invention.

FIGS. 15 to 18 are diagrams illustrating methods for forming cumulative spin data used in the method for detecting the spin of the ball in motion of FIG. 14.

FIG. 19 is a workflow diagram of a method for detecting the spin of a ball in motion according to another embodiment of the present invention.

FIG. 20 is a diagram showing a schematic structure of a virtual golf device according to an embodiment of the present invention.

FIG. 21 is a diagram showing an example of a method for calculating a motion of a golf ball in the virtual golf device of FIG. 20.

FIG. 22 is a diagram showing an example of a screen display providing golf play information in the virtual golf device of FIG. 20.

FIG. 23 is a diagram showing a schematic structure of a virtual golf device according to another embodiment of the present invention.

FIG. 24 is a diagram showing a schematic structure of a virtual golf system according to an embodiment of the present invention.

DETAILED DESCRIPTION

Hereinafter, a detailed description will be given of the present invention with reference to the following embodiments. The purposes, features, and advantages of the present invention will be easily understood through the following embodiments. The present invention is not limited to such embodiments but may be modified in other forms. The embodiments to be described below are nothing but the ones provided to bring the disclosure of the present invention to perfection and assist those skilled in the art to completely understand the present invention. Therefore, the following embodiments are not to be construed as limiting the present invention.

It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present therebetween.

The size of the element or the relative sizes between elements in the drawings may be shown to be exaggerated for more clear understanding of the present invention.

In addition, the shape of the elements shown in the drawings may be somewhat changed by variation of the manufacturing process or the like. Accordingly, the embodiments disclosed herein are not to be limited to the shapes shown in the drawings unless otherwise stated, and it is to be understood to include a certain amount of variation.

FIG. 1 is a workflow diagram of a method for detecting the spin of a ball in motion according to an embodiment of the present invention, and FIGS. 2 to 7 are diagrams showing each step of the method for detecting the spin of the ball in motion of FIG. 1.

Referring to FIG. 1, the process for detecting the spin of the ball includes first to fourth steps S11-S14. In the first step S11, an image of the ball in motion is acquired, in the second step S12, information is acquired from the image, in the third step S13, an estimated spin is determined, and in the fourth step S14, the estimated spin is applied to the information acquired in the second step S12 to detect the spin of the ball in motion.

Referring to FIG. 2, when the ball in motion moves in about 2 o'clock direction while rotating with spin, in the first step S11, the ball is captured at a first time T1 to acquire a first image I1 and the ball is captured at a second time T2 after the first time T1 to acquire a second image I2. The ball may include various types of balls used in different sports (for example, a golf ball, a baseball, a table tennis ball, etc.), and the ball has an identifier A on the surface. The identifier A may be a mark that is formed on the surface of the ball and used to detect the rotational state of the ball. For example, a baseball has a plurality of seams to allow pitchers to throw various types of balls, and the spin of the baseball may be detected by checking a state change of the seams in the baseball in motion, and the seams of the baseball may act as the identifier A. In addition, manufacturer name or brand is formed on the surface of the most of sports balls, and the spin can be detected through a state change of the manufacturer name or brand so that it can act as the identifier A.

Referring to FIG. 3, in the second step S12, first information associated with the identifier A is acquired from the first image I1 and second information associated with the identifier A is acquired from the second image I2. There may be many methods for acquiring the ball information from the ball image. As an example, the first image I1 may include other parts (for example, the spot where the ball moves may be included as the background of the ball) except the ball and the information associated with the identifier A may be acquired by image processing to remove other parts except the ball and extract only the ball and the identifier A on the surface of the ball, and analysis of a relationship between the ball and the identifier A, and the same method may be applied to the second image I2. Here, the information associated with the identifier A, i.e., identification information (simply referred to as ‘information’ for convenience) may be position information of the identifier A in the ball. In the case of a ball having a spherical shape, each point on the surface of the ball may have different position information from the center of the sphere. Accordingly, the identifier A on the surface of the ball may also have specific position information from the center of the ball having the spherical shape, and the position information of the identifier A may be detected by extracting the images of the ball and the identifier A and analyzing the positional relationship between the center of the ball and the identifier A.

The first and second identification information of the identifier A may be indicated by A1(i1, j1, k1) and A2(i2, j2, k2), respectively. Here, each of A1(i1, j1, k1) and A2(i2, j2, k2) may be position information for a single point or may be position information for a plurality of points. That is, in the case of the identifier A consisting of a single point, A1(i1, j1, k1) and A2(i2, j2, k2) are position information for the single point, and in the case of the identifier A consisting of a plurality of points, A1(i1, j1, k1) and A2(i2, j2, k2) are position information for the plurality of points. Generally, the identifier A consists of a plurality of points rather than a single point.

Because the ball and the identifier A exist in a 3-dimensional space (3D space), the position information of the identifier A may be indicated by three independent components representing the 3 dimensions, and i, j, k denote the three independent components. For example, i, j, k may denote x component, y component and z component in a rectangular coordinate system. Alternatively, i, j, k may denote r component, φ component and θ component in a spherical coordinate system. To detect the 3D position information of the identifier A from the image of the ball, a stereo camera or a depth camera may be used to capture the ball, or a plurality of cameras that can acquire 3D information may be used. Alternatively, instead of a stereo camera or a depth camera, a camera that commonly generates a 2D image may be used, and 2D position information of the identifier A is acquired from the image captured by the commonly used camera. Even though 2D position information is acquired so that position information for only i and j components among the i, j and k components in the identifier A is acquired, if the ball moves under a specific requirement (for example, when a spin value of the ball related to the k component is zero or almost negligible), the spin of the ball can be detected using only the 2D position information.

Referring to FIG. 4, it is assumed that the ball rotates with spin around a specific axis in the 3D space made up of i axis, j axis and k axis. Here, the spin may be defined by an axis of rotation of the ball and an amount of rotation of the ball. For example, when the spin of the ball is ‘S’, the spin Si of the i axis component, the spin Sj of the j axis component and the spin Sk of the k axis component may be written as:

$S=\mathrm{Sii}+\mathrm{Sjj}+\mathrm{Skk}$

(i, j and k denote the basic unit vector of the i axis, the j axis and the k axis, respectively)

In this instance, the rotation amount S1 and the rotation axis S2 of the spin S may be calculated by Si, Sj, Sk as follows.

$S1=\sqrt{{\mathrm{Si}}^2+{\mathrm{Sj}}^2+{\mathrm{Sk}}^2}$ $S2=\left(\frac{\mathrm{Si}}{S1},\frac{\mathrm{Sj}}{S1},\frac{\mathrm{Sk}}{S1}\right)$

When the spin of the ball in motion is referred to as a target spin S*, the identifier A is located at a first position in the ball at the first time T1, and by the target spin S*, the identifier A is located at a second position in the ball at the second time T2. That is, the target spin S* plays a role in changing the position of the identifier A in the ball. When the rotation amount S1* and the rotation axis S2* of the target spin S* are known, a displacement factor by the target spin S* may be mathematically deduced in the form of a matrix. Meanwhile, when the identifier A is expressed by a plurality of points (pixels), each of the first and second information (A1(i1, j1, k1), (A2(i2, j2, k2)) may be a set of position information for the plurality of points. When they are referred to as A1set and A2set and the displacement matrix by the target spin S* of the ball is referred to as Sm*, the following Equation (1) holds:

$\begin{array}{cc}\left[S{m}^{\star }\right]\left[A1\mathrm{set}\right]=\left[A2\mathrm{set}\right]& \mathrm{Equation}\left(l\right)\end{array}$

According to Equation (1), when the displacement factor [Sm*] by the target spin S* is applied to the first identification information [A1set] of the identifier A, the second identification information [A2set] may be acquired. The first and second identification information [A1set], [A2set] is known and the target spin S* is unknown at the present time, according to an embodiment of the present invention, the spin of the ball that is currently in motion can be found by using Equation (1). In this embodiment, a random spin is assumed and the displacement factor by the random spin is applied to Equation (1) to check if Equation (1) is satisfied, then when Equation (1) is satisfied, the random spin is determined as the target spin S* and when Equation (1) is not satisfied, a new random spin is assumed repeatedly until Equation (1) is satisfied.

As mentioned above, according to this embodiment, it is necessary to assume the random spin to use Equation (1), and in relation to this, in the third step S3, the estimated spin that may be the target spin S* is determined. Referring to FIG. 5, in determining the estimated spin, cumulative spin data for the spin is used. The cumulative spin data may be a collection of data for all spins recorded in the past when users have moved balls with spin by their play. For example, when it is assumed that the ball in motion is a golf ball used in virtual golf play such as screen golf, a screen golf facility may be equipped with a sensing means such as a laser sensor to measure the spin, and using the sensing means, each time all users who play screen golf hit golf balls, the spin of each golf ball may be measured. The measured spin may be stored in a storage device such as a memory or a hard disk in the screen golf facility. In the case of a plurality of screen golf facilities, when the plurality of screen golf facilities is managed by a central server, the measured spin may be stored in the central server's storage device. In this way, if the spin by the corresponding stroke is stored each time the user hits the golf ball, the stored data may be accumulated to form the cumulative spin data for all the golf balls hit by all the users. When a sufficient amount of data are accumulated, the cumulative spin data may have a shape of a Gaussian distribution curve. As shown in FIG. 5, the Gaussian distribution curve is bilaterally (left-right) symmetrical with respect to the mean (m) and most of data is intensively distributed in a range of m-σ (σ is the standard deviation) and m+σ with respect to the mean. In the third step S13, the random spin is determined as the estimated spin (indicated by ES in FIG. 5) in the Gaussian distribution of the cumulative spin data, and for example, the initial estimated spin may be determined at or near the mean (m). Because the mean (m) indicates the highest frequency that the corresponding spin will happen in cumulative statistics, when the estimated spin is determined near the mean (m), there is a high likelihood that the determined estimated spin will be determined as the spin (the target spin S*) of the golf ball in motion.

In the fourth step S14, the estimated spin is applied to the first and second identification information for the identifier A to detect the spin of the ball in motion. Specifically, first, the estimated spin is applied to the above Equation (1) as follows.

$\begin{array}{cc}\left[{\mathrm{ESm}}^{\star }\right]\left[A1\mathrm{set}\right]=\left[\mathrm{EA}2\mathrm{set}\right]& \mathrm{Equation}\left(2\right)\end{array}$

Here, [ESm] denotes the displacement matrix by the estimated spin, [A1set] denotes the first identification information associated with the identifier A at the first time, and [EA2set] (referred to as ‘preliminary information’ for convenience) denotes the result obtained by applying the estimated spin to the first identification information. When the preliminary information is acquired by Equation (2), the preliminary information is compared with the second identification information. As a result of comparing the preliminary information with the second information, when there is a difference between the preliminary information and the second information, this represents that the estimated spin is not a correct spin (the target spin S*) and a new spin is determined. Here, the difference between the preliminary information and the second information represents that there is a difference between the shape of the identifier A under the assumption that the estimated spin is applied to the identifier A at the first time T1 and the actual shape of the identifier A at the second time T2 as shown in FIG. 6. When the estimated spin is decided as an incorrect spin, a new estimated spin is determined, the displacement factor by the new estimated spin is applied to the first information to calculate new preliminary information, and the new preliminary information is compared with the second information to decide whether the new estimated spin is a correct spin. When the preliminary information and the second information are identical or very similar, the determined spin is definitely determined as the target spin of the ball that is currently in motion. Here, the preliminary information and the second information being very similar means that there is a very small difference between [EA2set] and [A2set] that is equal to or less than a predetermined value (the position information may be plus (+) or minus (−), and here, the small difference represents that the absolute value is small).

Even when the estimated spin determined for the first time is determined as an incorrect spin, the cumulative spin data is continuously used to determine the new estimated spin. Referring to FIG. 7, for convenience, when the estimated spin determined for the first time is referred to as an initial estimated spin ES and the estimated spin determined next time is referred to as a second estimated spin ES′, ES″, the initial estimated spin ES and the second estimated spin ES′, ES″ may be determined according to a constant rule.

For example, the initial estimated spin ES may be determined at or near the mean (m). Because the mean (m) indicates the highest frequency that the corresponding spin will happen in cumulative statistics, when the estimated spin ES is determined near the mean (m), there is a high likelihood that the determined estimated spin ES will be determined as the spin of the golf ball in motion. When the initial estimated spin ES is not a correct spin, the second estimated spin ES′, ES″ may be determined. When the second estimated spin ES′, ES″ is determined, the second estimated spin ES' having a first difference A1 from the initial estimated spin ES or the second estimated spin ES″ having a second difference A2 from the initial estimated spin ES may be determined. As described above, when the initial estimated spin ES is applied to the first information for the identifier A, the ‘preliminary information’ for the identifier A at the second time T2 is acquired. As a result of comparing the ‘preliminary information’ with the second information for the identifier A, when there is a small difference between them, this represents that the initial estimated spin ES is not so much different from a correct spin, and thus it is desirable to determine the second estimated spin ES' in a range in which the difference with the initial estimated spin ES is comparatively small. In addition, as a result of comparing the ‘preliminary information’ with the second information for the identifier A, when there is a big difference between them, this represents that the initial estimated spin ES is greatly different from a correct spin, and thus it is desirable to determine the second estimated spin ES″ in a range in which the difference with the initial estimated spin ES is comparatively large.

FIG. 8 is a workflow diagram of a method for detecting the spin of a ball in motion according to another embodiment of the present invention, and FIGS. 9 to 13 are diagrams showing each step of the method for detecting the spin of the ball in motion of FIG. 8.

Referring to FIG. 8, the process for detecting the spin of the ball includes first to fifth steps S21-S25. In the first step S21, an image of the ball in motion is acquired, in the second step S22, information is acquired from the image, in the third step S23, an estimated spin is determined, in the fourth step S24, the estimated spin is applied to the information acquired in the second step S22 to detect the spin of the ball in motion, and in the fifth step S25, the detected spin is verified.

Referring to FIG. 9, when the ball in motion moves in a predetermined direction while rotating with spin, in the first step S21, the ball is captured at a first time T1 to acquire a first image I1, the ball is captured at a second time T2 after the first time T1 to acquire a second image I2, and the ball is captured at a third time T3 after the second time T2 to acquire a third image I3. The ball may include various types of balls used in different sports, for example, a golf ball, a baseball, a table tennis ball, etc., and the ball has an identifier A on the surface. The identifier A may be a mark that can be identified from the outside.

Referring to FIG. 10, in the second step S22, first information associated with the identifier A is acquired from the first image I1, second information associated with the identifier A is acquired from the second image I2 and third information associated with the identifier A is acquired from the third image I3. Ball information may be acquired by removing other parts except the ball from the image and extracting only the ball and the identifier A on the surface of the ball, and analyzing a relationship between the ball and the identifier A. Here, the information associated with the identifier A may be position information of the identifier A in the ball, and specifically, the first to third information may be indicated by A1(i1, j1, k1), A2(i2, j2, k2), A3 (i3, j3, k3), respectively. Here, each of A1(i1, j1, k1), A2(i2, j2, k2), A3 (i3, j3, k3) may be position information for a single point or position information for a plurality of points.

In the third step S23, the estimated spin is randomly determined. Referring to FIG. 11, in the same way as the previous embodiment, cumulative spin data for the spin may be used to determine the estimated spin. The cumulative spin data may be formed by accumulating the past records for a plurality of spins, and when a sufficient amount of data is accumulated, the cumulative spin data may have a shape of a Gaussian distribution curve. As shown in FIG. 11, the Gaussian distribution is bilaterally (left-right) symmetrical with respect to the mean (m) and most of data is intensively distributed in a range of m-σ (σ is the standard deviation) and m+σ with respect to the mean. In the third step S23, one or more random spins are determined in the Gaussian distribution of the cumulative spin data. In the case of one random spin, the subsequent step (fourth and fifth steps S24, S25) is performed on one estimated spin, and in the case of the plurality of estimated spins, the subsequent step (fourth and fifth steps S24, S25) is performed on the plurality of estimated spins at a time. If third to fourth steps S23-S25 are performed many times until a correct spin is found, it is desirable to determine the plurality of estimated spins and perform the subsequent step at a time for the purpose of efficient procedure. In determining the plurality of estimated spins (ES1, ES2, ES3), they may be determined at random positions, or when determining them for the first time, they may be determined near the mean (m) or the standard deviation (o). Because the mean (m) or the standard deviation (o) indicates a relatively high frequency that the corresponding spin will happen in cumulative statistics, when the estimated spins ES1, ES2, ES3 are determined near the mean (m) or the standard deviation (o), there is a high likelihood that any of the determined estimated spins ES1, ES2, ES3 will be the real spin of the ball in motion.

In the fourth step S24, the estimated spins ES1, ES2, ES3 are applied to the first and second information for the identifier A to detect the spin of the ball in motion. To this end, first, the estimated spins ES1, ES2, ES3 are applied to the following Equations (3-1), (3-2), (3-3).

$\begin{array}{cc}\left[\mathrm{ES}1m\right]\left[A1\mathrm{set}\right]=\left[E1A2\mathrm{set}\right]& \mathrm{Equation}\left(3-1\right)\end{array}$ $\begin{array}{cc}\left[\mathrm{ES}2m\right]\left[A1\mathrm{set}\right]=\left[E2A2\mathrm{set}\right]& \mathrm{Equation}\left(3-2\right)\end{array}$ $\begin{array}{cc}\left[\mathrm{ES}3m\right]\left[A1\mathrm{set}\right]=\left[E3A2\mathrm{set}\right]& \mathrm{Equation}\left(3-3\right)\end{array}$

For convenience of description, the estimated spins ES1, ES2, ES3 are referred to as a first estimated spin ES1, a second estimated spin ES2 and a third estimated spin ES3, respectively. In the above Equations, [A1set] denotes the position information (‘first information’) of the identifier A at the first time T1, [ESm1], [ESm2], [ESm3] denote displacement factors by the first to third estimated spins ES1, ES2, ES3, respectively, [E1A2set] is preliminary information (referred to as ‘first preliminary information’) acquired by applying the first estimated spin ES1 to the first information, [E2A2set] is preliminary information (referred to as ‘second preliminary information’) acquired by applying the second estimated spin ES2 to the first information, and [E3A2set] is preliminary information (referred to as ‘third preliminary information’) acquired by applying the third estimated spin ES3 to the first information. When the first to third preliminary information is acquired, they are compared with the second information. As a result of comparing the first to third preliminary information with the second information, when there is a difference between the first to third preliminary information and the second information, all the first to third estimated spins ES1, ES2, ES3 cannot be a correct spin and the third step S23 is performed again. That is, in the third step S23, a plurality of estimated spins is determined again, and in this instance, estimated spins that are different from the previously determined first to third estimated spins ES1, ES2, ES3 are determined.

As shown in FIG. 12, when the first and second preliminary information formed by the first and second estimated spins ES1, ES2 is significantly different from the identifier information at the second time T2 (the second information [A2set]) and the third preliminary information formed by the third estimated spin ES3 is identical/similar to the identifier information at the second time T2 (the second information [A2set]), the third estimated spin ES3 is determined as the spin of the ball in motion.

In the fifth step S25, the spin detected in the fourth step S24 is verified by using the third information. As shown in FIG. 13, in the fifth step S25, the third estimated spin ES3 is applied to the second information for the identifier A (or the third estimated spin ES3 may be applied to the first information). To this end, the third estimated spin ES3 is applied to the following Equation (4).

$\begin{array}{cc}\left[\mathrm{ES}3m\right]\left[A2\mathrm{set}\right]=\left[E3A2\mathrm{set}\right]& \mathrm{Equation}\left(4\right)\end{array}$

In the above Equation (4), [ESm3] denotes the displacement factor by the third estimated spin ES3, [A2set] denotes the position information of the identifier A at the second time T2, and [E3A3set] is the result obtained by applying the third estimated spin ES3 to the second information (referred to as ‘verification information’). When the verification information is acquired, the verification information is compared with the third information [A3set]. As a result of comparing the verification information with the third information, when there is a difference between the verification information and the third information, the third estimated spin cannot be a correct spin and the process returns to the third step S23 to perform the step of determining the estimated spin again. As a result of comparing the verification information with the third information, when the verification information and the third information are identical or very similar, the third estimated spin is determined as the spin of the ball in motion and the entire process of detecting the spin ends. Here, the verification information and the third information being very similar means that there is a very small difference between [E3A3set] and [A3set] that is equal to or less than a predetermined value. The reason why the verification step is added is because the spin that changes the identifier A from the state at the first time (the state represented by the first information) to the state at the second time (the state represented by the second information) may include a plurality of spins (for convenience of description, as a simple example in 2D, it is assumed that the identifier A is located at 9 o'clock position of the ball at the first time and is located at 12 o'clock position of the ball at the second time. A state change between the first and second times can happen by two spins that are a plurality of spins: the spin rotating the ball by 90° in the clockwise direction and the spin rotating the ball by 270° in the counterclockwise direction), and through the verification step, the spin of the ball in motion may be accurately identified among the plurality of spins.

FIG. 14 is a workflow diagram of a method for detecting the spin of a ball in motion according to another embodiment of the present invention, and FIGS. 15 to 18 are diagrams illustrating methods for forming cumulative spin data used in the method for detecting the spin of the ball in motion of FIG. 14.

Referring to FIG. 14, the process for detecting the spin of the ball includes first to fifth steps S31-S35. In the first step S31, an image of the ball being in motion and having an identifier on the surface is acquired, in the second step S32, identification information of the identifier is acquired from the image, in the third step S33, any one of a plurality of cumulative spin distribution data is selected, in the fourth step S34, an estimated spin is determined by using the selected spin distribution data, and in the fifth step S35, the spin of the ball in motion is detected by using the determined estimated spin.

Each of the first to fifth steps S31-S35 is described in detail. In the first step S31, the ball having the identifier on the surface is captured at a first time to acquire a first image, and the ball is captured at a second time after the first time to acquire a second image. In the second step S32, first information associated with the identifier is acquired from the first image and second information associated with the identifier is acquired from the second image. The first and second information may be position information of a point (or points) at which the identifier is located in the ball. In the third step S33, a selection step of selecting any one of the plurality of spin distribution data is performed and it will be described below. In the fourth step S34, the estimated spin is randomly determined by using the spin distribution data selected in the third step S33. Here, one or more estimated spins may be determined. In the fifth step S35, one or more estimated spins determined in the fourth step S34 are applied to the first information to acquire preliminary information and the preliminary information is compared with the second information. As a result of comparing the preliminary information with the second information, when there is a difference between the preliminary information and the second information, the estimated spin cannot be a correct spin, and the process returns to the fourth step S34 and the fourth and fifth steps S34, S35 are performed again. Among the first to fifth steps S31-S35 of this embodiment, the first, second, fourth and fifth steps S31, S32, S34, S35 correspond to the first to fourth steps S11, S12, S13, S14 in the first embodiment (described with reference to FIGS. 1 to 7) and their detailed description is omitted.

In relation to the third step S33, referring to FIG. 15, the cumulative spin data may be stored in a predetermined storage device. For example, when it is assumed that the ball in motion is a golf ball used in virtual golf paly such as screen golf, a screen golf facility may be equipped with a sensing means such as a laser sensor to measure the spin, and using the sensing means, each time all users playing screen golf hit golf balls, the spin of each golf ball can be measured. The measured spin may be stored in the storage device such as a memory or a hard disk of a computer in the screen golf facility. Alternatively, in the case of a plurality of screen golf facilities, the plurality of screen golf facilities is managed by a central server, and the measured spin may be stored in the central server's storage device. When the spin by the corresponding stroke is stored each time the user hits the golf ball, the stored data may be accumulated to form the cumulative spin data for all golf balls hit by the user. Here, the cumulative spin data stored in the storage device may include a plurality of cumulative spin data classified according to the user's golf skill level. For example, the cumulative spin data may be classified into cumulative spin data for ALL User formed based on spin information of golf balls hit by all users who played golf in the screen golf facility, cumulative spin data for 1 Level User formed based on spin information of golf balls hit by users having first golf skill level who played golf in the screen golf facility, cumulative spin data for 2 Level User formed based on spin information of golf balls hit by users having second golf skill level who played golf in the screen golf facility, and cumulative spin data for 3 Level User formed based on spin information of golf balls hit by users having third golf skill level who played golf in the screen golf facility. The cumulative spin data for ALL User, the cumulative spin data for 1 Level User, the cumulative spin data for 2 Level User and the cumulative spin data for 3 Level User may show different Gaussian distribution curves. When the cumulative spin data is classified according to the user's golf skill level, the cumulative spin data for ALL User may be used to determine the estimated spin as described in the above-described embodiment. Alternatively, when the user who hit the golf ball of which the spin is currently to be detected has second golf skill level, the estimated spin may be determined by using the Gaussian distribution curve based on data (the cumulative spin data for 2 Level User) of users having the same golf skill level as the corresponding user. When the cumulative spin data includes the plurality of cumulative spin data classified according to the user's golf skill level, and the cumulative spin data of users having the golf skill level identical or similar to the golf skill level of the user who hit the golf ball is used to detect the spin of the golf ball in motion, it can reduce the time required to detect the spin.

The golf skill level is determined according to many factors. As one example of many factors, there is shot accuracy. When a golf ball is accurately hit, the golf ball moves straight toward a target, but otherwise, hook or slice occurs, that is to say, the golf ball goes left or right of target. A golf ball with hook or slice has a higher side spin than a golf ball without it. Accordingly, when users having high skill level and high shot accuracy hit golf balls, the corresponding golf balls usually move forward due to low side spin, and in contrast, when users having low golf skill level and low shot accuracy hit golf balls, hook or slice usually happens due to high left side spin or high right side spin of the corresponding golf balls. In addition to shot accuracy, there may be many other factors that determine the golf skill level such as driving distance or putting, and low golf skill level may not be the only cause of hook or slice, but lots of accumulated data from a lot of users reveal that the distribution of spin data differs to some extent depending on the golf skill level. When it is assumed that the spin of all users has a range of (Sa, Sb) and the spin of specific level users has a range of (Sa′, Sb′) within the range of (Sa, Sb), if the cumulative spin data for ALL User is used to detect the spin of a golf ball hit by a specific level user, the spin falling within the range of (Sa, Sb) but outside of the range of (Sa′, Sb′) may be determined as the estimated spin and there is a high likelihood that the estimated spin will not be a correct spin. In this case, due to the time required to perform the fourth and fifth steps S34, S35 on the corresponding estimated spin, the time required for the entire operation may increase. In contrast, if the spin data of the specific level user is used to detect the spin of the golf ball hit by the specific level user instead of the cumulative spin data for ALL User, the spin in the range of (Sa′, Sb′) may be determined as the estimated spin and the estimated spin is more likely to be a correct spin than the spin outside of the range (Sa′, Sb′). Therefore, the time required for the entire operation can be reduced compared to when the cumulative spin data for ALL User is used.

The process of selecting the specific cumulative spin data among all the cumulative spin data in the third step S33 has been as above described, and in the embodiment described with reference to FIG. 15 a criterion for selecting specific data among all the data is ‘user's golf skill level’. By applying the same principle, in the third step S33, specific data may be selected among all the data according to other ‘criterion’ than ‘user's golf skill level’. As an example of the other ‘criterion’, there is motion characteristics of the ball. It is assumed that the ball in motion is a golf ball used in virtual golf play such as screen golf, and each time the user hits the golf ball in virtual golf play, the spin by the corresponding stroke is stored in a storage device and the stored data is accumulated to form cumulative spin data of all golf balls hit by the user. Here, the cumulative spin data stored in the storage device may include a plurality of cumulative spin data classified according to the motion characteristics of the golf ball after impact occurring when the user hits the golf ball. For example, referring to FIG. 16, the cumulative spin data may be classified into ALL cumulative spin data based on spin information of all golf balls hit by all users playing in the screen golf facility, cumulative spin data for No Side Spin based on spin information of golf balls having the motion characteristics of moving forward with little or no side spin after the impact, cumulative spin data for Left Side Spin based on spin information of golf balls having the motion characteristics of curving to the left by the left side spin after the impact, and cumulative spin data for Right Side Spin based on spin information of golf balls having the motion characteristics of curving to the right by the right side spin after the impact (Here, the cumulative spin data for No Side Spin/the cumulative spin data for Left Side Spin/the cumulative spin data for Right Side Spin may be sub-classified into a plurality of items according to the size of the side spin. For example, the cumulative spin data for Left Side Spin may be classified into a larger number of items such as a first range of cumulative spin data for Left Side Spin, a second range of cumulative spin data for Left Side Spin, etc.). As shown in FIG. 16, the cumulative spin data for No Side Spin/the cumulative spin data for Left Side Spin/the cumulative spin data for Right Side Spin may exhibit different Gaussian distribution curves. When the cumulative spin data is classified according to the motion characteristics of the golf ball after the impact, the ALL cumulative spin data may be used to determine the estimated spin as described in the above-described embodiment. Alternatively, a state change of the golf ball of which the spin is currently to be detected is detected, and as a result of detection, when the golf ball shows the motion characteristics of curving to the right in flight, the estimated spin may be determined by using the Gaussian distribution curve based on the data (the cumulative spin data for Right Side Spin) corresponding to the motion characteristics. When the cumulative spin data includes the plurality of cumulative spin data classified according to the motion characteristics of the golf ball and the cumulative spin data corresponding to the motion characteristics of the golf ball is used to detect the spin of the corresponding golf ball in motion, it can reduce the time required for the operation of detecting the spin, and the reason is similar to that described in case of the use of the cumulative spin data classified according to the user's golf skill level (see the description related to FIG. 15).

Although an example of the cumulative spin data including the plurality of cumulative spin data classified according to the characteristics of the path along which the golf ball moves after the impact occurring when the user hits the golf ball has been hereinabove described, there may be any other criterion than the motion characteristics. For example, the cumulative spin data may be classified into a plurality of cumulative spin data according to the speed or launch angle of the golf ball hit by the user. Additionally, the cumulative spin data may include a plurality of cumulative spin data based on only one of the variables such as the motion characteristics, speed or launch angle, or the cumulative spin data may include a plurality of cumulative spin data based on at least two of the variables. When two or more compound variables are applied, two or more compound variables of the golf ball at impact may be detected, the cumulative spin data related to the applied two or more compound variables may be selected, and the estimated spin may be determined from the selected cumulative spin data.

In the embodiment described with reference to FIGS. 15 and 16, the cumulative spin data includes the plurality of cumulative spin data classified according to the specific criterion, but it is not necessary to separately prepare each of the plurality of cumulative spin data beforehand. The cumulative spin data that meets the ‘specific criterion’ used when determining the estimated spin may be generated immediately before determining the estimated spin, and it will be described with reference to FIGS. 17 and 18.

Like the previous embodiment, it is assumed that the ball is a golf ball used in virtual golf play such as screen golf and the user's record in screen golf play is stored in a computer's storage device such as a memory or a hard disk in the screen golf device. Alternatively, when there are a plurality of screen golf facilities and a central server manages the plurality of screen golf facilities, the user's play record may be stored in the central server's storage device. Referring to FIG. 17, the storage device may be divided into a plurality of storage areas and the play records of different users may be stored in each of the plurality of storage areas. The storage area may store the user's play score, information associated with the state of the golf ball such as the spin or driving distance when the user hits the golf ball, and the user's personal record such as scoring average, average driving distance, fairway landing ratio. In addition, the storage area may store information associated with the user's golf skill level. Here, the user's golf skill level may be determined by using a lot of play information when the user has played in the past, and for example, the user's golf skill level may be determined by using the ‘scoring average’. The scoring average refers to, in a golf course usually having 18 holes, an average of the total of strokes when the 18-hole play is completed. In golf the regulation figure for 18 holes is 72 strokes, and the fewer the number of strokes in 18-hole play is, the higher the golf skill level is. Professional golfers have the scoring average in the late 60s or early 70s and ordinary people having the scoring average in the late 70s and early 80s may be acknowledged as having advanced skill level, and the scoring average of about 100 strokes may be a criterion in determining the beginner level or non-beginner level. As described above, the scoring average may be an example of an indicator showing the user's golf skill level, and users having the same scoring average or slight differences in scoring average by approximately some strokes may be determined to have the same golf skill level.

It is assumed that the process of detecting the spin of a ball hit by a user is performed when the user is playing golf and has second skill level. According to the embodiment previously described with reference to FIGS. 14 and 15, a Gaussian distribution curve made from spin distribution data for users having the same golf skill level as the user who is playing golf among the plurality of spin distribution data may be selected and an estimated spin may be determined in the selected Gaussian distribution curve. However, according to this embodiment, there is no Gaussian distribution curve for users having the same golf skill level as the user who is playing golf. If the user who is currently playing golf is User 1 and User 3/User 4 have the same golf skill level as User 1, as shown in FIG. 17, spin information S1, S3, S4 of users (User 1, User 3, User 4) may be extracted from the storage area of the play record of the users, and cumulative spin data having a Gaussian distribution curve may be generated based on the extracted spin information. In this way, cumulative spin data of users having the specific golf skill level can be generated immediately before the step of determining the estimated spin, and in this case, there is no need to form beforehand and separately store the plurality of cumulative spin data according to the user's golf skill level.

When extracting the data that meets the ‘specific criterion’, collecting the data, generating the cumulative spin data and determining the estimated spin, the ‘specific criterion’ may include any other criterion than the user's golf skill level described above. For example, there may be motion characteristics of the ball. Like the previous embodiment, it is assumed that the ball is a golf ball used in virtual golf play such as screen golf and the user's record in screen golf play is stored in the screen golf device or the storage device of the central server that manages the plurality of screen golf facilities. Referring to FIG. 18, the storage device may be divided into a plurality of storage areas, and the record of physical state of the golf ball after impact occurring when the user hits the golf ball may be stored in each of the plurality of storage areas. Specifically, when users hit golf balls, information associated with the state of the golf ball such as the movement speed, movement direction, spin and/or launch angle of the golf ball at or after the impact may be stored in the storage area and the information may be dividedly stored according to the motion characteristics of the golf ball. Some information corresponding to the motion characteristics of the golf ball in motion may be extracted from the information stored in the storage device, and the cumulative spin data for determining the estimated spin may be formed based on the extracted information. For example, as shown in FIG. 18, it is assumed that the physical state of the golf balls hit by users is stored in the storage area that is divided into the plurality of storage areas, and each of the plurality of storage areas stores the motion characteristics of the golf ball (for example, the golf ball moves forward without curving, the golf ball slightly curves to the right in flight, the golf ball sharply curves to the right in flight, etc.) and the spin when the golf ball has the corresponding motion characteristics. Additionally, it is assumed that the golf ball hit by the user has motion characteristics of curving to the right in flight. In the storage device, when Motion 1, Motion 2 and Motion 5 are cases representing the motion characteristics of the golf ball curving to the right and Motion 3 and Motion 4 are cases irrelevant to the motion characteristics of the golf ball curving to the right, spin information (S1, S2, S5) corresponding to the motion characteristics of Motion 1, Motion 2 and Motion 5 may be extracted and cumulative spin data having a Gaussian distribution curve based on the extracted spin information may be generated. In this way, the cumulative spin data of the case representing the specific motion characteristics may be generated immediately before the step of determining the estimated spin, and in this case, there is no need to prepare beforehand and separately store each cumulative spin data according to the motion characteristics of the golf ball.

FIG. 19 is a workflow diagram of a method for detecting the spin of a ball in motion according to another embodiment of the present invention.

Referring to FIG. 19, the process for detecting the spin of the ball includes first to sixth steps S41-S46. In the first step S41, an image of the ball in motion is acquired, in the second step S42, identification information is acquired from the image, in the third step S43, any one of a plurality of spin distribution data is selected, in the fourth step S44, an estimated spin is determined by using the selected spin distribution data, in the fifth step S45, the estimated spin is applied to the information acquired in the second step S42 to detect the spin of the ball in motion, and in the sixth step S46, the detected spin is verified.

When comparing this embodiment with the embodiment described with reference to FIGS. 14 to 18, this embodiment is different in that one more image and one more identifier information is acquired in the first and second steps and the sixth step S46 of verifying the spin is added. That is, this embodiment is different from the previous embodiment in that a third image is further acquired and used to verify the spin, and this correspond to the first, second and fifth steps S21, S22, S25 in the embodiment described with reference to FIGS. 8 to 13. As a result, this embodiment is a combination of the embodiment described with reference to FIGS. 8 to 13 and the embodiment described with reference to FIGS. 14 to 18, and each step in this embodiment can be sufficiently understood from the description of the corresponding steps in the previous embodiments and thus its detailed description is omitted.

Also in this embodiment, cumulative spin data that meets the specific requirement related to the golf ball in motion such as the golf skill level of the user and/or the motion characteristics of the golf ball may be selected by using the stored information shown in FIGS. 15 and 16 and the estimated spin may be determined by using the cumulative spin data. Alternatively, also in this embodiment, spin data of the case meeting the specific requirement such as the golf skill level of the user and/or the motion characteristics of the golf ball may be extracted by using the stored information shown in FIGS. 17 and 18, cumulative spin data may be generated by using the extracted data, and the estimated spin may be determined by using the generated cumulative spin data.

Various methods for detecting the spin of the ball in motion have been hereinabove described, and the above-described method for detecting the spin may be used in various devices. The spin detection is necessary in sports devices such as golf, baseball, soccer, etc., and in particular, there is a growing need when the user plays virtual sports indoors. Hereinafter, a virtual golf device as an example of the sports device using spin detection operation will be described.

FIG. 20 is a diagram showing a schematic structure of the virtual golf device according to an embodiment of the present invention, FIG. 21 is a diagram showing an example of a method for calculating a trajectory of a golf ball in the virtual golf device of FIG. 20, and FIG. 22 is a diagram showing an example of a screen display providing golf play information in the virtual golf device of FIG. 20.

Referring to FIG. 20, the virtual golf device according to an embodiment of the present invention includes a hitting plate 10, a control unit 20, a sensing unit 30, an input unit 40, a sound unit 50 and a display unit 60.

The hitting plate 10 is an area where a user is positioned to hit a golf ball. The hitting plate 10 may be a plate-shaped object or may not be a separate object but simply an area where the user is located on the bottom surface of the place where the virtual golf device is installed. Although not shown in the drawings, the hitting plate 10 is equipped with a hitting mat on which a golf ball is placed and an auto tee that can move up and down is installed on the hitting mat. A golf ball to be hit can be automatically provided to the user through the auto tee.

The control unit 20 controls the overall operation between the components of the virtual golf device. For example, the control unit 20 can control the auto tee in order that the auto tee automatically provides the golf ball to the user at the time of hitting the golf ball, and specifically, immediately after the user hits the golf ball on the hitting mat, the control unit 20 can detect the stroke and enable the auto-tee to provide the golf ball for the next shot. The control unit 20 includes a calculation unit 21, a spin calculation unit 22 and a storage unit 23. The calculation unit 21 performs a calculation process to calculate a trajectory of the golf ball when it is assumed that the golf ball moves on a real golf course with the physical state formed when the user hit the golf ball. The spin calculation unit 22 plays a role in calculating the spin of the golf ball hit by the user, and the spin calculation process may use the method described with reference to FIGS. 1 to 19. The spin calculation unit 22 may be separate from the calculation unit 21 that calculates the trajectory of the golf ball, but the calculation unit 21 may be configured to play a role in calculating the spin as well as the trajectory without the separate spin calculation unit 22 shown in FIG. 20. The storage unit 23 includes a storage device such as a memory or a hard disk and stores a variety of programs or data necessary for the operation of the control unit 20, the calculation unit 21 and the spin calculation unit 22. The user's play record and/or the cumulative spin data used to calculate the spin may be stored in the storage unit 23 or a storage means of the spin calculation unit 22 itself.

The sensing unit 30 is used to detect the movement of the golf club and/or the movement of the golf ball hit by the user to obtain the information necessary for the calculation process. As the sensing unit 30, a sensing means such as cameras capable of photographing the movement of the golf club and/or the movement of the golf ball or sensors may be used. Various sensing methods such as image sensing, light emission/light reception sensing, laser sensing and so on may be applied to the sensing means, and information on the state of the golf club used by the user and/or the golf ball hit by the user can be obtained through those sensing methods. The camera or the sensor may be used alone or used together, and only one sensing device may be used or several sensing devices may be used if circumstances need. The information detected by the sensing unit 30 is transmitted to the control unit 20 and is used for the calculation process. In addition, in order for the spin calculation unit 22 to calculate the spin of the golf ball hit by the user, an image of the golf ball at a specific time is needed, and when a camera is used as the sensing unit 30, the image may be generated by the sensing unit 30. In this case, the sensing unit 30 performs an operation of acquiring the information for trajectory calculation and an operation of acquiring the information for spin calculation together. Here, the operation of acquiring the information for spin calculation may include an operation of detecting the motion characteristics of the golf ball such as translational motion of the golf ball or the movement path of the golf ball. The operation of detecting the motion characteristics of the golf ball is needed to detect the spin by applying the method by the embodiment described with reference to FIG. 16 or 18. If the sensing unit cannot perform the operation of acquiring the information for spin calculation, a separate camera may be equipped for the purpose of this use.

The input unit 40 is needed for the user to input various information. As the input unit 40, a keyboard, a mouse or a touch screen may be used. In the screen golf, the information input by the user is needed for various cases. For example, when the user inputs ID or password for login or selects a golf course or a play difficulty level, the user needs to input the related information. The input unit 40 is used for this object.

The sound unit 50 may include audio apparatus such as a speaker and serves to inform the user of the information about the progress of the golf play and reproduce various sound effects according to the progress of the golf play.

The display unit 60 may include apparatus for display operations such as a projector, screen, etc. The projector gives the golf-related image showing the golf ball and/or the golf course to the screen, and the screen displays the given image to provide it to the user. Although not shown in the drawings, the display unit 60 may further include display apparatus such as a kiosk that serves as an auxiliary display in addition to the screen.

Hereinafter, some objects displayed on the screen may be expressed by using the term ‘virtual’. This means that it does not exist in the real world and is displayed on the screen. For example, ‘virtual golf course’ means a golf course displayed on the screen and ‘virtual golf ball’ means a golf ball displayed on the screen.

By using the virtual golf device, the user can play screen golf. When the user plays screen golf, the virtual golf device operates as follows. When the user hits a golf ball the sensing unit 30 detects the physical state such as the movement of the golf club and/or the moving speed or direction of the golf ball hit by the user. The information sensed by the sensing unit 30 is delivered to the control unit 20. The calculation unit 21 of the control unit 20 performs the calculation process for computing the trajectory of the golf ball based on the delivered information. After that, the image of the virtual golf ball moving along the computed trajectory is displayed in the screen. The virtual golf ball in the screen lands at one location in the virtual golf course, and the user redoes the screen golf play from the location where the virtual golf ball landed by hitting the golf ball.

When the calculation unit 21 performs the calculation process of calculating the trajectory of the golf ball, many methods may be used in the calculation process, and one of the methods may include detecting a parameter value representing the physical state of the golf ball after the user hits the golf ball and calculating the trajectory from the parameter value. Referring to FIG. 21, the parameter may include the speed V of the golf ball, the left/right face angle φ representing a direction of the golf ball flying by the shot on the horizontal plane, the launch angle θ representing the angle of inclination of the golf ball relative to the horizontal plane, and the spin S representing the rotational state of the golf ball. The trajectory of the golf ball may be calculated by applying a calculation model using the physical law based on the parameters such as the speed V, the face angle q, the launch angle θ, the spin S, etc. Among the physical parameters, the spin S may be detected by analysis of a plurality of golf ball images captured while the golf ball is flying after the user hits the golf ball by the spin calculation unit 22, and the process of calculating the trajectory of the golf ball may be performed by reflecting the detected spin after the spin is detected. Although not shown in the drawings, not only the physical state of the golf ball but also the movement of the golf club when the user hits the golf ball may be detected and the trajectory of the golf ball may be calculated by further using the detected information of the golf club.

After the user hit the golf ball, the detected information of the physical state of the golf ball hit by the user may be displayed on the screen. Referring to FIG. 22, while the user plays golf, the golf course in which the user is playing golf may be displayed on the screen, and the detected information of the physical state of the golf ball hit by the user may be displayed at an edge of the screen. For example, the detected information of the speed, the spin and the launch angle of the golf ball hit by the user may be displayed on the screen. In relation to the spin, the user takes an interest in the side spin and the backspin that affect the trajectory of the golf ball, and the side spin and the backspin may be separately displayed on the screen. The side spin represents approximately the left/right spin component with respect to a direction in which the golf ball flies, and the side spin may affect the flight path of the golf ball. Additionally, the backspin represents approximately the spin component in a direction opposite to the flight direction of the golf ball, and the backspin may affect the flight distance of the golf ball.

FIG. 23 is a diagram showing a schematic structure of a virtual golf device according to another embodiment of the present invention.

Referring to FIG. 23, the virtual golf device according to the present embodiment includes a plurality of booths 101, 102, 103. Each booth has the same structure. For example, the first booth 101 includes a hitting plate 101a, a computer apparatus 101b that is equipped with a small display such as a kiosk and can act as the above-described control unit, a screen 101c, etc., and the other booths 102 and 103 also include the same components. Although not shown in the drawings, each of the booths 101, 102, 103 may further include other components. For example, each of the booths 101, 102, 103 has a camera for detecting the movement of a golf ball and/or a golf club. In each of the booths 101, 102, 103, a plurality of users can take turns playing golf. Alternatively, in each of the booths 101, 102, 103, one user can play golf while being separated from users of other booths. The virtual golf device according to this embodiment may include the spin calculation unit in the above-described embodiment, and the spin calculation unit may detect the spin of the golf ball hit by the user by using the method described with reference to FIGS. 1 to 19.

FIG. 24 is a diagram showing a schematic structure of a virtual golf system according to an embodiment of the present invention.

Referring to FIG. 24, the virtual golf system includes a virtual golf device 100 and a service device 200. As the virtual golf device 100, a virtual golf device such as those shown in FIGS. 20 to 23 may be used. The virtual golf device 100 may be installed in a house or a facility operated by a service provider. If there are multiple houses and/or facilities, the virtual golf device 100 is installed at each place of multiple houses and/or facilities and thus there may be a plurality of virtual golf devices in total. The virtual golf device 100 may include the spin calculation unit in the above-described embodiment, and the spin calculation unit may detect the spin of the golf ball hit by the user by using the method described with reference to FIGS. 1 to 19.

The virtual golf device 100 is connected to the service device 200 through a wired/wireless communication network or the like. The service device 200 may include a central server prepared by a service provider providing screen golf service using the virtual golf device(s) 100 to manage the virtual golf device(s) 100. If a log-in process is applied, a user needs to log in in order to receive the screen golf service. When a user logs in, the service device 200 checks the user's identity and determines whether to approve the login. The service device 200 includes a storage unit 210 that stores information necessary for checking the identity of the user. Additionally, the storage unit 210 may store not only ‘the information for user identification’ but also ‘the user's play record information’ and/or ‘cumulative spin data used to calculate the spin or information for forming the cumulative spin data’ (for example, the storage unit 210 may include the storage device shown in FIGS. 15 to 18). Since the storage unit 210 stores various user information and/or the spin information, the virtual golf device(s) 100 connected to the service device 200 by wire and/or wireless communication network can use the information stored in the storage unit 210 and there is no need to separately store user information and/or the spin information in the virtual golf device(s) 100.

Although the embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that the present invention may be embodied in other specific ways without changing the technical spirit or essential features thereof. Therefore, the embodiments disclosed in the present invention are not restrictive but are illustrative. The scope of the present invention is given by the claims, rather than the specification, and also contains all modifications within the meaning and range equivalent to the claims.

Claims

1. A method for detecting the spin of a ball in motion, comprising: an image acquisition step of acquiring a first image of a ball at a first time and acquiring a second image of the ball at a second time, the ball being in motion with spin and having an identifier;an identification information acquisition step of acquiring first identification information of the identifier from the first image and acquiring second identification information of the identifier from the second image; anda spin detection step of determining an estimated spin by using cumulative spin data, and applying the estimated spin to the first and second identifier information to detect the spin of the ball in motion.

2. The method for detecting the spin of the ball in motion according to claim 1, wherein the ball is a golf ball, and as a user hits the golf ball with a golf club, the golf ball moves with spin, and wherein the cumulative spin data is formed using information associated with the spin of the golf ball when the user who hits the golf ball of which the spin is currently to be detected and other users having a same golf skill level as the corresponding user have played golf in the past.

3. The method for detecting the spin of the ball in motion according to claim 1, wherein the ball is a golf ball, and as a user hits the golf ball with a golf club, the golf ball moves with spin, wherein the method further comprises detecting a state change by the motion of the golf ball between the first time and the second time, andwherein after spin data corresponding to the state change of the golf ball is determined, the cumulative spin data is formed using the determined spin data.

4. The method for detecting the spin of the ball in motion according to claim 1, wherein in the spin detection step, a result of applying the estimated spin to the first identification information is compared with the second identification information, and according to a result of comparing with the second identification information, the estimated spin is determined as the spin of the ball in motion or a new estimated spin is determined and the spin detection step is performed again.

5. The method for detecting the spin of the ball in motion according to claim 4, wherein the cumulative spin data exhibits a Gaussian distribution, and the estimated spin includes a plurality of estimated spins determined by extracting a plurality of random spins differently located in the Gaussian distribution.

6. The method for detecting the spin of the ball in motion according to claim 4, wherein the cumulative spin data exhibits a Gaussian distribution, and the estimated spin is initially determined in a range between a minus (−) standard deviation and a plus (+) standard deviation with respect to a mean in the Gaussian distribution.

7. The method for detecting the spin of the ball in motion according to claim 4, wherein the new estimated spin is determined such that with an increasing value of the result of comparing the result of applying the estimated spin to the first identification information with the second identification information, a difference between the estimated spin and the new estimated spin increases.

8. The method for detecting the spin of the ball in motion claim 1, further comprising: performing additional steps including a step of acquiring a third image of the ball at a third time, a step of acquiring third identification information of the identifier from the third image, and a step of verifying the detected spin by using the third identification information.

9. The method for detecting the spin of the ball in motion according to claim 8, wherein the spin detected in the spin detection step includes a plurality of spins, and wherein the result of applying the plurality of spins to the first identification information or the second identification information is compared with the third identification information, and according to a result of comparing with the third identification information, any one of the plurality of spins is definitely determined as the spin of the ball in motion or a new estimated spin is determined and the spin detection step and the additional steps are performed again.

10. A virtual golf device comprising: a calculation unit to perform a calculation process of calculating a motion of a virtual golf ball corresponding to a real golf ball when a user hits the real golf ball; anda display unit to display a virtual golf course and the virtual golf ball moving in the virtual golf course as calculated in the calculation process,wherein the virtual golf device detects the spin of the real golf ball after the user hits the real golf ball by a method for detecting the spin of a ball in motion including an image acquisition step of acquiring a first image of the ball at a first time and acquiring a second image of the ball at a second time, the ball being in motion with spin and having an identifier, an identification information acquisition step of acquiring first identification information of the identifier from the first image and acquiring second identification information of the identifier from the second image, and a spin detection step of determining an estimated spin by using cumulative spin data, and applying the estimated spin to the first and second identifier information to detect the spin of the ball in motion.

11. The virtual golf device according to claim 10, wherein the calculation process reflects a result of detecting the spin of the real golf ball.

12. A virtual golf system comprising: a service device; andat least one virtual golf device connected to the service device via communication,wherein the virtual golf device includes a calculation unit to perform a calculation process of calculating a motion of a virtual golf ball corresponding to a real golf ball when a user hits the real golf ball, and a display unit to display a virtual golf course and the virtual golf ball moving in the virtual golf course as calculated in the calculation process, andwherein the virtual golf device detects the spin of the real golf ball after the user hit the real golf ball by a method for detecting the spin of a ball in motion including an image acquisition step of acquiring a first image of the ball at a first time and acquiring a second image of the ball at a second time, the ball being in motion with spin and having an identifier, an identification information acquisition step of acquiring first identification information of the identifier from the first image and acquiring second identification information of the identifier from the second image, and a spin detection step of determining an estimated spin by using cumulative spin data, and applying the estimated spin to the first and second identifier information to detect the spin of the ball in motion.

13. The virtual golf system according to claim 12, wherein the service device includes a storage unit to store user information, and wherein the user information is used to form the cumulative spin data during the detection of the spin of the real golf ball.