Patent Application
20220240774
The present invention relates to a binocular visual function measurement method, a binocular visual function measurement program, an eyeglass lens designing method, an eyeglass lens manufacturing method, and a binocular visual function measurement system.
Eyeglass wearers may be subjected to binocular visual function examinations to measure convergence and divergence ranges, for example. There are individual differences in convergence and divergence ranges, and it is very important to measure the convergence and divergence ranges in order to understand the functions of the eyes in near vision in designing of eyeglass lenses.
With regard to the binocular visual functions represented by the convergence and divergence ranges and the like, Patent Document 1 discloses that the binocular visual function is measured by presenting left and right parallax images using a stationary three-dimensional compatible video monitor, moving the positions where they are presented, relative to each other, and detecting the timing at which images cannot be fused, for example.
Patent Document 1: JP-2012-95693A
In the binocular visual function measurement method disclosed in Patent Document 1, the binocular visual function is measured using a stationary three-dimensional compatible video monitor. Thus, the position of the head of a measurement subject is not fixed with respect to left and right parallax images, and thus there is a risk that an error may occur in the median plane depending on the orientation of the head during measurement. Furthermore, by placing the stationary three-dimensional compatible video monitor in a real environment, in addition to parallax information to be displayed, the measurement subject simultaneously acquires information (real space information) that gives a sense of depth and perspective from the outside world, which may result in the convergence and divergence that occur together with normal accommodation. Furthermore, because the stationary three-dimensional compatible video monitor is used, the size of the required system configuration is increased, and thus it cannot be said that the binocular visual function can be easily measured.
The present invention aims to provide a technique by which the binocular visual function of a measurement subject can be very easily measured with high accuracy.
The present invention was made to achieve the above-described aim.
A first aspect of the present invention is directed to a binocular visual function measurement method, the method including:
a visual target presentation step of presenting a right eye image to be viewed by the right eye of a measurement subject and a left eye image to be viewed by the left eye of the measurement subject to the subject in a space where real space information is blocked out;
a presentation control step of changing positions where the right eye image and the left eye image are presented, relative to each other;
a timing detection step of detecting a timing at which the measurement subject is unable to fuse the right eye image and the left eye image when the presentation positions are changed; and
a parameter value calculation step of calculating a predetermined parameter value regarding a binocular visual function of the measurement subject based on a relationship between the relative positions of the right eye image and the left eye image when the timing is detected.
A second aspect of the present invention is directed to the binocular visual function measurement method according to the first aspect,
in which the right eye image and the left eye image are presented using a head mounted display to be worn by the measurement subject.
A third aspect of the present invention is directed to the binocular visual function measurement method according to the first or second aspect,
in which the predetermined parameter value is a value for specifying a convergence range of the measurement subject.
A fourth aspect of the present invention is directed to the binocular visual function measurement method according to any one of the first to third aspects, the method including
a tracking ability determination step of determining a level of the ability of an eye of the measurement subject to track a change in positions of the presented images,
in which, in the presentation control step, the speed of a change in relative positions of the right eye image and the left eye image is determined based on a result of the determination performed in the tracking ability determination step.
A fifth aspect of the present invention is directed to the binocular visual function measurement method according to any one of the first to fourth aspects,
in which the right eye image and the left eye image are constituted by figures having the same shape and the same size.
A sixth aspect of the present invention is directed to the binocular visual function measurement method according to any one of the first to fifth aspects, the method including
a visual range setting step of setting a visual range of the measurement subject with respect to the right eye image and the left eye image.
A seventh aspect of the present invention is directed to a binocular visual function measurement program for causing a computer to execute the binocular visual function measurement method according to any one of the first to sixth aspects.
An eighth aspect of the present invention is directed to an eyeglass lens designing method, the method including:
a step of measuring the binocular visual function of the measurement subject using the binocular visual function measurement method according to any one of the first to sixth aspects; and
a step of determining an optical design value of the eyeglass lens based on a result of the measurement of the binocular visual function.
A ninth aspect of the present invention is directed to an eyeglass lens manufacturing method, the method including:
a step of designing an eyeglass lens using the eyeglass lens designing method according to the eighth aspect; and
a step of manufacturing the eyeglass lens according to a result of designing the eyeglass lens.
A tenth aspect of the present invention is directed to a binocular visual function measurement system, the system including:
a visual target presentation unit configured to present a right eye image to be viewed by the right eye of a measurement subject and a left eye image to be viewed by the left eye of the measurement subject to the subject in a space where real space information is blocked out;
a presentation control unit configured to change positions where the right eye image and the left eye image are presented, relative to each other;
a timing detection unit configured to detect a timing at which the measurement subject is unable to fuse the right eye image and the left eye image when the presentation positions are changed; and
a parameter value calculation unit configured to calculate a predetermined parameter value regarding a binocular visual function of the measurement subject based on a relationship between the relative positions of the right eye image and the left eye image when the timing is detected.
An eleventh aspect of the present invention is directed to the binocular visual function measurement system according to the tenth aspect,
in which the visual target presentation unit is configured using a head mounted display to be worn by the measurement subject.
According to the present invention, the binocular visual function of a measurement subject can be very easily measured with high accuracy.
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, an overview of this embodiment will be described.
In the present embodiment, a head mounted display (abbreviated as “HMD” hereinafter) to be worn by a measurement subject is used, and a pair of images with parallax are respectively presented to the left and right eyes of the measurement subject. The binocular visual function of the measurement subject is measured by determining whether the images are fused (identified) when the given parallax is changed. The binocular visual function is measured by calculating a predetermined parameter value for the binocular visual function.
Examples of the predetermined parameter value include values for specifying a convergence range of the measurement subject. A “convergence range” herein refers to the difference in angle between the convergence limit and the divergence limit. In the following description, a case where the convergence range is measured will mainly be described as an example. The predetermined parameter value is not limited to the values in the convergence range, and may be another parameter value such as the left-right eye vertical divergence allowable value, the first unequal magnification allowable value, the second unequal magnification allowable value, or the left-right eye rotation parallax allowable value, which will be described later.
In the present embodiment, because the HMD worn by the measurement subject is used in measurement of the binocular visual function thereof, the parallax images can be presented to the measurement subject in a space where real space information is blocked out. That is, the parallax images are presented in front of the eyes of the measurement subject in a state where the outside world is screened out, and thus, the measurement subject does not acquire information (real space information) that gives a sense of depth and perspective from the outside world, in addition to the presented parallax images.
Furthermore, by mounting an HMD on the measurement subject, the parallax images can be accurately positioned regardless of the direction of the face of the measurement subject.
Also, the visual range to the parallax images (the physical distance between the images and the subject who sees the images) is also kept constant, and thus it is possible to measure the binocular visual function while keeping the accommodation function (focusing function) of the eyes of the measurement subject constant.
Therefore, according to the present embodiment, it is possible to perform composite measurements in the same measurement environment without taking the posture and the position of the measurement subject into consideration. Also, by presenting only a pair of parallax images using the HMD, it is possible to measure the capability relating to a pure convergence range without giving a sense of depth, and to reduce the influence of accommodative convergence. “Accommodative convergence” here refers to convergence (convergence and divergence movement) that occurs simultaneously with accommodation in the near triad that occurs when looking at a near position.
That is, according to the present embodiment, it is possible to very easily measure the convergence range while eliminating three-dimensional perception by the measurement subject. If the convergence range of the measurement subject can be very easily measured with high accuracy in this manner, an eyeglass lens suitable for the measurement subject can be provided by using the results of measurements as one of the parameters for designing the eyeglass lens.
For example, a measurement subject who has been found to have weak motor fusion based on the results of measurements is likely to complain of diplopia in which images are unlikely to fuse under strong binocular separation. Therefore, it is possible to provide an eyeglass lens with a lens design that compensates for weak motor fusion by inserting a prism to the extent where motor fusion is achieved. Furthermore, with regard to the measurement subject who was found to have strong motor fusion based on the results of measurement, the Panum's fusional area may be wide, and thus it is possible to provide an eyeglass lens provided with a lens design that can reduce inset without affecting fusion of images and reduce the maximum aberration on the nasal side, for example. Note that “motor fusion” refers to fusion with eyeball movements performed to maintain single vision.
<Example of System Configuration>
Next, a specific content of the present embodiment will be described.
(Configuration of Eyeglass Lens Manufacturing System)
The PC 30 includes a CPU (Central Processing Unit) 32, an HDD (Hard Disk Drive) 34, and a RAM (Random Access Memory) 36. A processing control program for controlling the processing device 50 is installed in the HDD 34. The CPU 32 loads the processing control program onto the RAM 36, and starts the program. When the processing control program is started, a GUI (Graphical User Interface) for issuing an instruction to design and manufacture an eyeglass lens is displayed on a display screen of the display 40. The processing control program selects a semi-finished lens based on specification data and measurement data, performs surface shape optimization calculation, and determines optical design values.
An operator sets the selected semi-finished lens in the processing device 50, operates the GUI, and inputs an instruction to start processing. The processing control program reads the determined optical design values and controls driving of the processing device 50. The processing device 50 grinds the surface of the semi-finished lens according to the execution of the processing control program so as to manufacture an eyeglass lens. Note that a specific method for designing an eyeglass lens using measurement data regarding the binocular visual function is described in a pamphlet in WO 2010/090144 filed by the applicant, for example.
(Configuration of Binocular Visual Function Measurement System)
As shown in
That is, the HMD 110 functions as a “visual target presentation unit” to present the right eye image and the left eye image to the measurement subject 2 in a space where real space information is blocked out. In other words, the visual target presentation unit is constituted using the HMD 110 to be worn by the measurement subject 2.
When such an HMD 110 is worn, only the right eye image is visible to the right eye 2R of the measurement subject 2, and only the left eye image is visible to the left eye 2L of the measurement subject 2. As a result, the measurement subject 2 can three-dimensionally perceive the parallax images on the right eye image display panel 111R and the left eye image display panel 111L, the parallax images being formed at non-corresponding points on the retina within the Panum's fusional area.
Note that the HMD 110 may have the function of being able to vary the settings of the visual range of the measurement subject 2 with respect to the right eye image and the left eye image. Specifically, in order to achieve a variable visual range, the HMD 110 may have display optical systems 112R and 112L that include eyepieces and the like, for example. Furthermore, a configuration may be adopted in which a plurality of spacers (frame members) are prepared, and the visual range of the HMD 110 can be varied by selectively installing any of the plurality of spacers, for example.
A PC 130 is connected to the HMD 110 configured as described above via a wired or wireless communication line. A display 140 is connected to the PC 130.
The PC 130 includes a CPU 132, an HDD 134, a RAM 136, and an input device 138 (a keyboard, a mouse, a game controller, and the like). A binocular visual function measurement program for measuring a binocular visual function is installed in the HDD 134. The CPU 132 loads the binocular visual function measurement program onto the RAM 136, and starts the program. When the binocular visual function measurement program is started, the CPU 132 functions as a presentation control unit 132a, a timing detection unit 132b, and a parameter value calculation unit 132c.
The presentation control unit 132a controls image display operations of the right eye image display panel 111R and the left eye image display panel 111L of the HMD 110. Specifically, the presentation control unit 132a instructs the right eye image display panel 111R to present a right eye image and instructs the left eye image display panel 111L to present a left eye image, and the presentation control unit 132a changes positions where the right eye image and the left eye image are presented, relative to each other. A specific mode in which the presentation positions are changed relative to each other will be described later in detail.
The right eye image and the left eye image presented by the presentation control unit 132a function as parallax images, and thus it is presumed that they are formed using figures having the same shape and the same size. Note that specific examples of the figures constituting parallax images will be described later in detail.
When the presentation positions of the right eye image and the left eye image are changed relative to each other, the timing detection unit 132b detects the timing at which the measurement subject 2 cannot fuse the right eye image and the left eye image. Such timing may be detected based on the content of an operation made by the measurement subject 2 on the input device 138.
When the parameter value calculation unit 132c detects the timing at which the timing detection unit 132b detects that images cannot be fused, the parameter value calculation unit 132c calculates a predetermined parameter value for the binocular visual function of the measurement subject 2 based on the relationship between the relative positions of the right eye image and the left eye image. Specific examples of the predetermined parameter value will be described later in detail.
In addition to these functions, the CPU 132 may function as a tracking ability determination unit 132d and a speed determination unit 132e in response to the start of the binocular visual function measurement program.
The tracking ability determination unit 132d determines the level of the tracking ability of an eye of the measurement subject 2 with respect to a change in the position of a presented image. Specifically, the tracking ability determination unit 132d presents a visual target that successively moves to the right eye image display panel 111R or the left eye image display panel 111L before measuring the binocular visual function of the measurement subject 2, for example. Then, based on the content of an operation made by the measurement subject 2 who has seen the visual target on the input device 138, it is determined which level the tracking ability of the eye of the measurement subject 2 corresponds to out of multiple preset levels. However, the determination method is not limited to such a method, and the tracking ability determination unit 132d may be configured to determine the tracking ability of an eye using another method. Because HMD devices having a line-of-sight tracking function are available as products, for example, when the HMD 110 has a line-of-sight tracking function, a configuration may be adopted in which the level of the trackability of the left and right eyes of the measurement subject 2 is determined by tracking the line-of-sight of the eyes of the measurement subject 2 using the line-of-sight tracking function.
The speed determination unit 132e determines the speed of a change in the relative positions of the right eye image and the left eye image when measuring the binocular visual function of the measurement subject 2, based on the results of the determination made by the tracking ability determination unit 132d. Specifically, when the tracking ability of the eyes of the measurement subject 2 is of a high level, the speed determination unit 132e determines the speed of a change in the relative positions of the right eye image and the left eye image as a high speed, whereas, when the tracking ability of the eyes of the measurement subject 2 is of a low level, the speed determination unit 132e determines the speed of a change in the relative positions of the right eye image and the left eye image as a low speed. The speed determination unit 132e instructs the presentation control unit 132a to control image display operations according to the results of the determination therefor.
Note that, in the system configuration described above, if all of the constituent elements of the eyeglass lens manufacturing system 1 are installed at the same location, the PC 30 shown in
<Procedure for Measuring Binocular Visual Function>
Next, specific content of a procedure for measuring a binocular visual function using the binocular visual function measurement system 10 configured as described above, that is, the binocular visual function measurement method according to the present embodiment, will be described.
If a binocular visual function is to be measured, the binocular visual function measurement program is started in the PC 130, and the GUI for giving various instructions for measuring the binocular visual function is displayed on the display screen of the display 140. Also, when the operator operates the GUI, the binocular visual function measurement program generates measurement data in accordance with the GUI operation and outputs the data to the HMD 110. The HMD 110 processes measurement data received from the PC 130, generates the right eye image and the left eye image for measuring the binocular visual function, and displays the images on the right eye image display panel 111R or the left eye image display panel 111L. This starts the measurement of the binocular visual function.
The binocular visual function measurement program supports various measurement items relating to the binocular visual function, and outputs the parameter values for the various measurement items as the results of the measurement. Examples of the supported parameter values include the convergence range, the left-right eye vertical divergence allowable value, the first unequal magnification allowable value, the second unequal magnification allowable value, and the left-right eye rotation parallax allowable value. When the operator measures the binocular visual function, the operator selects any one of the measurement items on the GUI.
Furthermore, the operator inputs the age, visual range, and the like as measurement conditions. The input measurement conditions are stored in the HDD 134. Note that, with regard to the visual range, the visual range may be changed using an eyepiece or the like as needed if the HMD 110 has the function of being able to vary the visual range settings.
The following describes processing executed by the binocular visual function measurement program when each of the above-listed measurement items is selected.
(If “Convergence Range” is Selected)
The binocular visual function measurement program transitions to the convergence range measurement mode in which the convergence range of the measurement subject 2 is measured. The “convergence range” herein refers to convergence without accommodation. Here, as indicated by a known Donders diagram, the convergence (or divergence) of eyeballs and accommodation originally occur together. Therefore, it is not easy to measure convergence separately from accommodation. Note that the Donders diagram is described in a document “written by Shinobu Ishihara and revised by Shinichi Shikano, “Little Pupil Science” 17th revised version, Kanehara & Co. Ltd., (1925) p50”, a document “written by Toyohiko Hatada, “Depth Information and Characteristics of Vision”, Visual Information Research Group, Apr. 23, 1974, p12”, and WO 2010/090144 pamphlet filed by the applicant, and the like. In the Donders diagram, a straight line passing through the origin and having a slope 1 (angle of 45 degrees) is the Donders line. The Donders line represents cooperation between convergence and accommodation when a measurement subject who does not have strabismus or heterophoria is looking at an object with naked eyes. A Donders curve indicating the limit of the convergence (or the divergence) is plotted on the left and right sides of the Donders line. Values from one point on the Donders line to the right Donders curve (the side where the convergence angle is large) are classified into negative relative convergence, and values from one point thereon to the left Donders curve (the side where the convergence angle is small) are classified into positive relative convergence.
As shown in
Furthermore, the measurement subject 2 is instructed to press a predetermined operation key of the input device 138 when the measurement subject 2 sees two images. An instruction is displayed on at least one of the right eye image display panel 111R and the left eye image display panel 111L, for example. Also, an operator may give an instruction directly to the measurement subject 2. The same instruction is issued even when measurement items other than the convergence range are measured.
As shown in
The period of time during which separating images are presented is, for example, about one second at the most, with the burden on the measurement subject 2 taken into consideration. Note that the presentation period of time can be changed by the operator as needed.
In the processing of S5 in
In the processing of S8 in
When the positive relative convergence and the negative relative convergence that are obtained in the processing of S8 in
When measurement is performed in the convergence range measurement mode while changing the visual range, the positive relative convergence and the negative relative convergence obtained when different accommodation occurs are measured. As the measurement of the convergence range at different visual ranges is repeated, the number of pieces of collected sample data for predicting the Donders curves increases. Therefore, the relationship regarding cooperation between the convergence and the accommodation of measurement subject 2 can be obtained more accurately.
If the separation speed between the left eye image 200L and the right eye image 200R is low, it is presumed that the measurement subject 2 will move the muscles around his/her eyeballs more strongly than in daily life to forcibly fuse the images. At this time, the fusional area expands beyond the range assumed considering the natural eyeball movement, and thus measurement accuracy decreases. In view of this, the separation speed is set relatively high such that the measurement subject 2 can see the left eye image 200L and the right eye image 200R in a relaxed state, which is similar to that in daily life. From a similar viewpoint, the speed of the relative changes (movement, rotation, scaling, and the like) between the left eye image 200L and the right eye image 200R is set relatively high when measuring measurement items other than the convergence range.
The operator can set and change the speed of relative changes as appropriate. However, it is desirable that the speed of a relative change that can be set and changed is within a predetermined range of speed. The upper limit of the speed of a relative change is set to a value such that an error caused by a time lag between the timing at which the measurement subject cannot fuse images and the timing at which the predetermined operation key of the input device 138 is pressed is within a predetermined allowable value range. On the other hand, the lower limit may be set to a value such that the display of the images changes before the fusional area expands beyond the range assumed considering the natural eyeball movement due to fusion of images being facilitated, for example. Specific examples of the set upper and lower limits are determined after performing experiments and the like, for example.
Note that, if the binocular visual function measurement program realizes the function of the tracking ability determination unit 132d and the speed determination unit 132e, the level of the tracking ability of the eyes of the measurement subject 2 with respect to a change in the positions of the presented images may be determined and the speed of a change in the relative positions of the left eye image 200L and the right eye image 200R may be determined based on the results of the determination. Doing this makes it possible to reflect the level of the tracking ability of the eyes of the measurement subject 2 on the moving speeds of the left eye image 200L and the right eye image 200R, and thus the measurement subject 2 can move his/her eyeballs without difficulty, and as a result, it is possible to accurately measure the binocular visual function of the measurement subject 2.
The left eye image 200L and the right eye image 200R may be separated from each other multiple times in order to measure the convergence range quickly and accurately. At the first measurement (hereinafter referred to as “pre-measurement” for convenience of description), for example, the left eye image 200L and the right eye image 200R are separated from each other at a high speed so as to specify the approximate position of the fusional limit. In the second measurement (hereinafter referred to as “main measurement” for convenience of description), the left eye image 200L and the right eye image 200R are separated from each other at a low speed (note that, a speed at which fusion is not strong) near the approximate position specified in the pre-measurement. In the main measurement, the separation speed is low, and thus an error caused by a time lag between the timing at which the measurement subject 2 cannot fuse images and the timing at which the predetermined operation key of the input device 138 is pressed is suppressed, and measurement accuracy is improved. Furthermore, the measurement interval in the main measurement is limited to the vicinity of the approximate position of the fusional limit specified in the pre-measurement. Thus, the convergence range can be measured quickly even if pre-measurement and main measurement are performed. Measurement items other than the convergence range are quickly measured with high accuracy, and thus pre-measurement and main measurement may be performed.
The parameter values of the convergence range of the measurement subject 2 are obtained from the positive relative convergence and the negative relative convergence that are measured in the convergence range measurement mode. The potential shift (esotropia or exotropia) of the measurement subject 2 is estimated based on such parameter values, for example. Parameter values can be estimated for measurement items other than the convergence range in a similar manner.
(If “Left-Right Eye Vertical Divergence Allowable Value” is Selected)
The binocular visual function measurement program transitions to the left-right eye vertical divergence allowable value measurement mode in which the left-right eye vertical divergence allowable value of the measurement subject 2 is measured. The left-right eye vertical divergence allowable value is the allowable value of vertical divergence of the left and right eyes that can realize/enable stereoscopic vision.
When the binocular visual function measurement program transitions to the left-right eye vertical divergence allowable value measurement mode and images are displayed (S1 in
In the processing of S15 in
In the processing of S18 in
(If “First Unequal Magnification Allowable Value” is Selected)
The first unequal magnification allowable value is the allowable value of unequal magnification of the left and right eyes that can enable stereoscopic vision. In general, whether or not to prepare a prescription of eyeglass lenses with respect to the unequal magnification is determined in a pattern-like manner in accordance with whether the eyesight difference between the left and right eyes is larger than or equal to 2 diopters. However, there are individual differences between patients, and thus, it may be difficult for a patient to achieve fusion of images even if the eyesight difference between the left and right eyes is less than 2 diopters. Also, in contrast to this, even if the eyesight difference between the left and right eyes is larger than or equal to 2 diopters, there are also cases where it may not be difficult for a patient to achieve fusion of images. In the first unequal magnification allowable value measurement mode described later, whether or not it is possible to fuse images is measured considering the eyesight difference between the left and right eyes. Thus, when the results of measurement obtained in the first unequal magnification allowable value measurement mode are used, it is possible to prepare a prescription optimal for unequal magnification with individual differences taken into consideration.
The binocular visual function measurement program transitions to the first unequal magnification allowable value measurement mode in which the first unequal magnification allowable value of the measurement subject 2 is measured.
When the binocular visual function measurement program transitions to the first unequal magnification allowable value measurement mode, as shown in
As shown in
As shown in
In the processing of S28 in
(If “Second Unequal Magnification Allowable Value” is Selected)
The binocular visual function measurement program transitions to the second unequal magnification allowable value measurement mode in which the second unequal magnification allowable value of the measurement subject 2 is measured. The second unequal magnification allowable value is the allowable value of unequal magnification of the left and right eyes that can enable stereoscopic vision limited to a specific direction.
When the binocular visual function measurement program transitions to the second unequal magnification allowable value measurement mode and images are displayed (S21 in
In the processing of S35 in
In the processing of S38 in
(If “Left-Right Eye Rotation Parallax Allowable Value” is Selected)
Fusional rotation may occur when the line-of-sight directions such as convergence are not parallel with each other. The rotation of an eyeball in the distance vision is based on Listing's law. Listing's law is a law defining the posture of an eyeball when the eyeball faces in a given direction in a space. The posture of the eyeball indicates the orientation of the eyeball in the lateral direction and the longitudinal direction. If the posture of the eyeball is not defined, upward, downward, left, and right directions of a retinal image are not defined. The posture of the eyeball is not defined uniquely by only the line-of-sight direction, that is, the direction of an optical axis of the eyeball. The posture of the eyeball can take all of the directions defined in regard to rotation about the line of sight serving as an axis even when the line-of-sight direction is defined.
Listing's law defines the posture of an eyeball facing an infinitely distant point in a given line-of-sight direction. With regard to Listing's law, “it is conceivable that any rotation of a single eye may occur about an axis in one plane (Listing's plane)” is described in “Handbook of Visual Information Processing” p. 405, for example.
The aforementioned Listing's law will be described using a coordinate system shown in
The posture after rotation of an eyeball in a given direction is the same as rotation about a straight line serving as an axis in the Listing's plane including the point R. In
Listing's law is appropriate in regard to a case where a single eye defines the posture of an eyeball with respect to an object at an infinite distance. Also, if a subject leans his/her body while looking at an object at an infinite distance, for example, the eyeballs of the left eye and the right eye have the same posture and the same rotation. In contrast, if a subject looks at an object that is not at an infinite distance with his/her eyes, the eyeballs of the left eye and the right eye may have different postures.
On the other hand, as shown in
Regarding the eyeball rotation based on Listing's law, the posture of the eyeball after rotation, that is, each of the direction vectors of the Y-axis and the Z-axis after rotation, depends on the visual direction vector indicated by the equation (1). If the visual direction vectors of the left eye and the right eye are different from each other, the direction vectors of the Y-axis and the Z-axis after rotation are different between the left and right eyes. Therefore, a rotational shift occurs in the retinal images. In order to cancel the rotational shift of the retinal images, rotation about the line of sight is required for the left and right eyes. Such rotation about this line of sight is fusional rotation.
When fusional rotation occurs, rotation parallax arises between the left and right eyes. In the binocular visual function measurement program, it is possible to measure a left-right eye rotation parallax allowable value, which is an allowable value of rotation parallax of the left and right eyes that can enable stereoscopic vision. When the measurement item “left-right eye rotation parallax allowable value” is selected, the binocular visual function measurement program transitions to the left-right eye rotation parallax allowable value measurement mode in which the left-right eye rotation parallax allowable value of the measurement subject 2 is measured.
As shown in
As shown in
In the processing of S48 in
(Other Measurements)
It is also possible to measure stereoscopic vision using the binocular visual function measurement system 10. In the measurement for stereoscopic vision, two types of parallax images having different shapes are displayed on the right eye image display panel 111R and the left eye image display panel 111L, for example. It is desirable that a parallax image has a simple geometrical shape such as a circle or a triangle such that the measurement subject 2 can focus on measurement. In the present embodiment, the two types of parallax images are a circle image and a triangle image. The circle image has a larger degree of parallax than the triangle image has. Therefore, the measurement subject 2 sees the circle image on the near side, and sees the triangle image on the far side. Then, the parallax of at least one of the circle image and the triangle image can be changed continuously or incrementally. The measurement subject 2 presses the predetermined operation key of the input device 138, for example, when the measurement subject 2 feels that neither of the circle image and the triangle image has depth or when the measurement subject 2 sees two images. The parallax of images obtained when the predetermined operation key is pressed is stored in the HDD 134. The CPU 132 calculates the limit to which the measurement subject 2 is able to perform stereoscopic viewing based on the stored parallax of images and visual range.
(Composite Measurements of Measurement Items)
In each of the above-described various measurement modes, one measurement item is measured. In another measurement mode, a composite measurement may be performed in which composite measurement items (e.g., at least two of the convergence range, left-right eye vertical divergence allowable value, first unequal magnification allowable value, second unequal magnification allowable value, and left-right eye rotation parallax allowable value) are measured simultaneously. In particular, if a plurality of measurement items that are closely related to each other are measured simultaneously, the results of a measurement that cannot be recognized by the result of measurement of a single measurement item may be obtained. The operator can select any measurement items to be measured simultaneously. Some combinations of the measurement items may be prepared in advance. The following describes three examples of composite measurement.
(Composite Measurement of Convergence Range—Left-Right Eye Vertical Divergence Allowable Value)
The convergence range and the vertical divergence have strong mutual interaction, for example. In view of this, in the first composite measurement mode, the convergence range and the left-right eye vertical divergence allowable value are measured simultaneously by moving, continuously or incrementally, at least one of the left eye image 200L and the right eye image 200R in an oblique direction on the screen. Here, the “oblique direction on the screen” refers to all of the directions other than the horizontal direction on the screen or the vertical direction on the screen, and include a horizontal direction component on the screen and a vertical direction component on the screen. That is, a change of the display (hereinafter referred to as a “composite change” for convenience of description) obtained by combining change patterns (movement in the horizontal direction on the screen and movement in the vertical direction on the screen) in the convergence range measurement mode and in the left-right eye vertical divergence allowable value measurement mode is given to the left eye image 200L or the right eye image 200R. The angle of the oblique direction on the screen may be set by the operator or predetermined by the binocular visual function measurement program.
(Composite measurement of convergence range—left-right eye vertical divergence allowable value—second unequal magnification allowable value (or first unequal magnification allowable value))
The convergence range, the vertical divergence, and unequal magnification of the left and right eyes have strong mutual interaction, for example. In view of this, in the second composite measurement mode, at least one of the left eye image 200L and the right eye image 200R is moved in the oblique direction on the screen continuously or incrementally, and is displayed in an enlarged or reduced size. If enlargement or reduction of an image is limited to a specific direction, the second unequal magnification allowable value is measured, whereas, if an image is enlarged or reduced in a fixed aspect ratio, the first unequal magnification allowable value is measured. A composite change, which is obtained by combining the changing patterns (movement in the horizontal direction on the screen, movement in the vertical direction on the screen, a change in display magnification) in the convergence range measurement mode, left-right eye vertical divergence allowable value measurement mode, or second unequal magnification allowable value (or first unequal magnification allowable value) measurement mode, is given to the left eye image 200L or the right eye image 200R. The ratio at which each change pattern is given may be set by the operator or may be predetermined by the binocular visual function measurement program.
(Composite measurement of convergence range—left-right eye rotation parallax allowable value) As described above, fusional rotation occurs accompanying convergence. In view of this, in the third composite measurement mode, at least one of the left eye image 200L and the right eye image 200R is moved in the horizontal direction on the screen continuously or incrementally, and is rotated clockwise or counterclockwise. That is, a composite change obtained by combining change patterns (movement in the horizontal direction on the screen and rotation about the center of mass of the image) in the convergence range measurement mode and in the left-right eye rotation parallax allowable value measurement mode is given to the left eye image 200L or the right eye image 200R. The ratio at which each change pattern is given may be set by the operator or may be predetermined by the binocular visual function measurement program.
(Measurement in Consideration of Lateral View)
In each of the above-described measurement modes, the left eye image 200L and the right eye image 200R are displayed in the center portion of the display screen. Therefore, this measurement only provides the results of measurement performed in a state where the measurement subject 2 faces forward. In view of this, after measurement in the state where the measurement subject 2 faces forward in each measurement mode is complete, as shown in
According to the present embodiment, one or more effects described below can be obtained.
(a) In the present embodiment, when the binocular visual function of the measurement subject 2 is measured, a right eye image and a left eye image (i.e., parallax images) are presented to the measurement subject 2 in a space where real space information is blocked out. Thus, the measurement subject 2 does not acquire information (real space information) that gives a sense of depth and perspective from the outside world, in addition to the presented parallax images. Also, the parallax images can be accurately positioned regardless of the direction of the face of the measurement subject 2, and there is no risk that an error will occur in the median plane. Therefore, according to the present embodiment, it is possible to precisely measure the capability relating to a pure binocular visual function without giving a sense of depth to the measurement subject 2. Furthermore, it is possible to very easily measure a binocular visual function without requiring a large-scale system configuration such as a stationary three-dimensional compatible video monitor. That is, according to the present embodiment, the binocular visual function of the measurement subject 2 can be very easily measured with high accuracy.
(b) In the present embodiment, the binocular visual function of a measurement subject is measured using the HMD 110 worn by the measurement subject 2. Thus, it is possible to easily and reliably present parallax images in a space where real space information is blocked out, thus suppressing installation costs therefor. Therefore, the realization of the presentation of parallax images thereon is preferable in order to very easily measure the binocular visual function with high accuracy.
(c) As described in the present embodiment, if values for specifying the convergence range of the measurement subject 2 are calculated as predetermined parameter values for the binocular visual function of the measurement subject 2, it is possible to very easily measure the convergence range of the measurement subject 2 with high accuracy. Also, by using the results of the above measurement as one of the parameters for designing an eyeglass lens, it is possible to provide an eyeglass lens suitable for the measurement subject 2.
(d) As described in the present embodiment, if the level of the ability of an eye of the measurement subject 2 to track a change in positions of the presented images is determined and the speed of a change in the positions of the presented images is then determined based on the results of the determination, the level of the tracking ability of the eye of the measurement subject 2 reflects on the speed of a change in the position of an image presented on the left side, and thus the measurement subject 2 can move his/her eyeballs without difficulty. As a result, it is possible to measure the binocular visual function of the measurement subject 2 with high accuracy.
<Variations and the Like>
Although the embodiment of the present invention was described above, the disclosed content described above illustrates exemplary embodiments of the present invention. That is to say, the technical scope of the present invention is not limited to the above-described exemplary aspects, and various modifications can be made without departing from the gist thereof.
Although the case where the parallax images are presented using the HMD 110 worn by the measurement subject 2 in a space where real space information is blocked out has been described as an example in the above-described embodiment, the present invention is not limited to this, and a configuration may be adopted in which parallax images are presented using another means in a space where real space information is blocked out.
Also, the above-described embodiment was described on the premise that the moving speed, rotation speed, and scaling speed of the left eye image 200L or the right eye image 200R are kept constant, for example. However, the present invention is not limited to this, and movement, rotation, or scaling of the left eye image 200L or the right eye image 200R may be accelerated.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-180310 | Sep 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/028743 | 7/27/2020 | WO | 00 |
