TECHNICAL FIELD
The present technology is generally related to the field of coin discrimination.
BACKGROUND
Various embodiments of consumer-operated coin counting kiosks are disclosed in, for example: U.S. Pat. Nos. 5,620,079, 6,494,776, 7,520,374, 7,584,869, 7,653,599, 7,748,619, 7,815,071, and 7,865,432; and U.S. patent application Ser. Nos. 12/758,677, 12/806,531, 61/364,360, 61/409,050, and 13/489,043; each of which is incorporated herein in its entirety by reference.
Many consumer-operated kiosks, vending machines, and other commercial sales/service/rental machines discriminate between different coin denominations based on the size, weight and/or electromagnetic properties of metal alloys in the coin. With some known technologies, a coin can be routed through an oscillating electromagnetic field that interacts with the coin. As the coin passes through the electromagnetic field, coin properties are sensed, such as changes in inductance (from which the diameter of the coin can be derived) or the quality factor related to the amount of energy dissipated (from which conductivity/metallurgy of the coin can be obtained). The results of the interaction can be collected and compared against a list of sizes and electromagnetic properties of known coins to determine the denomination of the coin. In other known technologies, a coin can be rolled along a predetermined path and the velocity of the coin or the time to reach a certain point along the path can be measured. By comparing the measured time or velocity against the corresponding values for known coins, the denomination of the coin can be determined.
However, many coins may have similar size, mass, metallurgy, and/or spectral properties. This is especially the case in markets which are proximate to multiple countries having different coin denominations. As a result, coin counting mistakes may occur due to the coin similarities, resulting in possible losses for consumer coin counting kiosk operators. Accordingly, it would be advantageous to provide robust coin discrimination systems and methods that would work reliably for coins having similar size, mass, metallurgy, and/or spectral properties.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a front isometric view of a consumer-operated coin counting kiosk suitable for implementing embodiments of the present technology.
FIG. 1B is a front isometric view of the consumer-operated coin counting kiosk of FIG. 1A with a front door opened to illustrate a portion of the kiosk interior.
FIG. 2 is an enlarged front isometric view of a coin counting system of the kiosk of FIGS. 1A and 1B.
FIG. 3 is a schematic view of a digital image acquisition system configured in accordance with an embodiment of the present technology.
FIG. 4A is a sample image of a coin acquired in accordance with an embodiment of the present technology.
FIG. 4B is a sample coin image of FIG. 4A after implementing edge detection in accordance with an embodiment of the present technology.
FIG. 5 illustrates several coin aspects in a log-polar coin image of the coin from FIGS. 4A and 4B.
FIGS. 6A and 6B illustrate results of a spectral analysis performed in accordance with an embodiment of the present technology on the coin image from FIG. 5.
FIG. 7 is a sample one-dollar coin image having several coin identification aspects in accordance with embodiments of the present technology.
FIGS. 8A and 8B are sample one-Euro coin images having several coin identification aspects in accordance with embodiments of the present technology.
DETAILED DESCRIPTION
The following disclosure describes various embodiments of systems and associated methods for discriminating coin denominations based on optical properties of the coins. In some embodiments of the present technology, a consumer-operated kiosk (e.g., a consumer coin counting machine, prepaid card dispensing/reloading machine, etc.) includes one or more digital cameras that can acquire digital images of a coin when the coin enters the viewfield of the cameras. The face, back side, and lateral edge of a typical coin includes numerous optical aspects that can be detected from the images and mapped to a suitable coordinate system (e.g., polar or rectangular coordinate system having an origin at a center of the coin). Some examples of the optical aspects are alphanumerical characters, embossed images or parts of the images, dots around the edge, intersecting lines, flat areas, and/or colors/shades of the coin. In some embodiments, the locations of the optical aspects of a coin can be compared to corresponding tabulated values for known coins in a relevant market to discriminate the coin. In some embodiments, angles between selected lines on the coin image can be used to discriminate the coins. Furthermore, distances between the optical aspects of the coin (e.g., tip of George Washington's nose to letter “R” in the word “TRUST”) can be determined and used to discriminate the coins. In some embodiments, the embossed alphanumerical characters can be interpreted using computer implemented optical character recognition (OCR) to obtain true denomination of the coin. Additionally, a spectral analysis of the digital image of the coin can be performed to generate further discriminating aspects of the coins. For example, spectral analysis can be performed along different areas of the coin (e.g., at a given distance from a center of the coin). The obtained spectral peak can be compared to tabulated spectral values for the relevant coins in the market. Since a rectangular domain is generally better suited for spectral analysis than a round domain, the digital image of a round coin can be first mapped into a rectangular domain using, for example, a log-polar transform. The outline edge of the coin can be detected using line detection algorithms including, for example, Canny edge detection. Once the outline of the coin is determined, the diameter and the width of the coin can be calculated and used to discriminate the coins. Based on the discrimination results, the coin can be properly credited or rejected by the consumer-operated kiosk.
The following disclosure describes various embodiments of coin counting systems and associated methods of manufacture and use. Certain details are set forth in the following description and FIGS. 1A-8B to provide a thorough understanding of various embodiments of the disclosure. Other details describing well-known structures and systems often associated with coin counting machines, however, are not set forth below to avoid unnecessarily obscuring the description of the various embodiments of the disclosure. Many of the details and aspects shown in the Figures are merely illustrative of particular embodiments of the disclosure. Accordingly, other embodiments can have other details and features without departing from the spirit and scope of the present disclosure. In addition, those of ordinary skill in the art will understand that further embodiments can be practiced without several of the details described below. Furthermore, various embodiments of the disclosure can include structures other than those illustrated in the Figures and are expressly not limited to the structures shown in the Figures. Moreover, the various elements and aspects illustrated in the Figures may not be drawn to scale.
FIG. 1A is an isometric view of a consumer coin counting machine 100 having a coin discrimination system configured in accordance with an embodiment of the present disclosure. In the illustrated embodiment, the coin counting machine 100 includes a coin input region or tray 102 and a coin return 104. The tray 102 includes a lift handle 113 for moving the coins into the machine 100 through an opening 115. The machine 100 further includes various user-interface devices, such as a keypad 106, user-selection buttons 108, a speaker 110, a display screen 112, a touch screen 114, and a voucher outlet 116. In other embodiments, the machine 100 can have other features in other arrangements including, for example, a card reader, a card dispenser, etc. Additionally, the machine 100 can include various indicia, signs, displays, advertisements and the like on its external surfaces. The machine 100 and various portions, aspects and features thereof can be at least generally similar in structure and function to one or more of the machines described in U.S. Pat. No. 7,520,374, U.S. Pat. No. 7,865,432, U.S. Pat. No. 7,874,478, U.S. patent application Ser. No. 13/489,043, U.S. patent application Ser. No. 13/691,047, and/or U.S. patent application Ser. No. 13/793,827 each of which is incorporated herein by reference in its entirety.
FIG. 1B is a partially cutaway isometric view of an interior portion of the machine 100. The machine 100 includes a door 137 that can rotate to an open position as shown. In the open position, most or all of the components of the machine 100 are accessible for cleaning and/or maintenance. In the illustrated embodiment, the machine 100 includes a coin cleaning portion (e.g., a rotating drum on trommel 140) and a coin counting portion 142. As described in more detail below, coins that are deposited into the tray 102 are directed through the trommel 140, and then to the coin counting portion 142. The coin counting portion 142 can include a coin rail 148 that receives coins from a coin hopper 144 via a coin pickup assembly 141. A power cord 158 can provide facility power to the machine 100.
In operation of this embodiment, a user places a batch of coins, typically of a plurality of denominations (and potentially accompanied by dirt or other non-coin objects and/or foreign or otherwise non-acceptable coins) in the input tray 102. The user is prompted by instructions on the display screen 112 to push a button indicating that the user wishes to have the batch of coins discriminated. An input gate (not shown) opens and a signal prompts the user to begin feeding coins into the machine by lifting the handle 113 to pivot the tray 102, and/or manually feeding coins through the opening 115. Instructions on the screen 112 may be used to tell the user to continue or discontinue feeding coins, to relay the status of the machine 100, the amount of coins counted thus far, and/or to provide encouragement, advertising, or other messages.
One or more chutes (not shown) direct the deposited coins and/or foreign objects from the tray 102 to the trommel 140. The trommel 140 in the depicted embodiment is a rotatably mounted container having a perforated-wall. A motor (not shown) rotates the trommel 140 about its longitudinal axis. As the trommel rotates, one or more vanes protruding into the interior of the trommel 140 assist in moving the coins in a direction towards an output region. An output chute (not shown) directs the (at least partially) cleaned coins exiting the trommel 140 toward the coin hopper 144. Trajectory of the coins through coin tubes 154a-b and return chute 156 is described in more detail with reference to FIG. 2 below.
FIG. 2 is an enlarged isometric view of the coin counting portion 142 of the coin counting machine 100 of FIG. 1B illustrating certain features in more detail. Certain components of the coin counting portion 142 can be at least generally similar in structure and function to the corresponding components described in U.S. Pat. No. 7,520,374. The coin counting portion 142 includes a base plate 203 mounted on a chassis 204. The base plate 203 can be disposed at an angle A with respect to a vertical line V from about 0° to about 15°. A circuit board 210 for controlling operation of various coin counting components can be mounted on the chassis 204.
The illustrated embodiment of the coin counting portion 142 further includes a coin pickup assembly 241 having a rotating disk 237 disposed in the hopper 266 and a plurality of paddles 234a-234d. The coin rail 248 extends outwardly from the disk 237, past a sensor assembly having a source of light 274 and a detector 270, a digital camera 272, and further toward a chute inlet 229. A bypass chute 220 includes a deflector plane 222 configured to deliver oversized coins to the return chute 256. A diverting door 252 is disposed proximate the chute entrance 229 and is configured to selectively direct discriminated coins toward coin tubes 254a-b. A flapper 230 is operable between a first position 232a and a second position 232b to selectively direct coins to the first delivery tube 254a or the second delivery tube 254b, respectively.
In operation of the coin counting portion 142, the rotating disk 237 rotates in the direction of arrow 235, causing the paddles 234 to lift individual coins 236 from the hopper 266 and place them on the rail 248. The angle A encourages coins 236 to lay flat against the rail, such that the face of a given coin is generally parallel with the base plate 203. The coins 236 travel along the rail and pass the digital camera 272. Coins that are larger than a preselected size parameter (e.g., a certain diameter) are directed to the deflector plane 222, into a trough 224, and then to the return chute 256. Coins within the acceptable size parameters pass through the digital image acquisition system described below with reference to FIG. 3. The associated software determines if the coin is one of a group of acceptable coins and, if so, the coin denomination is counted.
The majority of undesirable foreign objects (dirt, non-coin objects, etc.) are separated from the coin counting process by the trommel 140 or the deflector plane 222. However, coins or foreign objects of similar characteristics to desired coins are not separated and can pass through the coin sensor (described below with reference to FIG. 3). The coin sensor and the diverting door 252 operate to prevent unacceptable coins (e.g., foreign coins, fraudulent coins, etc.), blanks, or other similar objects from entering the coin tubes 254 and being kept in the machine 100. Specifically, in the illustrated embodiment, the coin sensor determines if an object passing through the sensor is a desired coin, and if so, the desired coin is “kicked” by the diverting door 252 toward the chute inlet 229. The flapper 230 is positioned to direct the kicked coin to one of the coin chutes 254. Coins that are not of a desired denomination, or are foreign or fraudulent coins, continue past the coin sensor to the return chute 256.
FIG. 3 is a partially schematic isometric view of a digital image acquisition system 300 configured in accordance with an embodiment of the present technology. In the illustrated embodiment, coins 336a and 336b can be placed on a rail 348 by a mechanism similar to the coin pickup assembly 241 described above in reference to FIG. 2. A radiation source 374 can direct electromagnetic radiation, for example visible or infrared light, toward a detector 370. The detector 370 can be a photo-detector that is sensitive to electromagnetic waves emitted by the radiation source 374. When the electromagnetic radiation from the radiation source 374 reaches the detector 370, a first value of output is sent to a controller 384. When a coin that rolls down the rail 348 interrupts the electromagnetic radiation received by the detector 370, the detector 370 transmits a second value of output to the controller 384 which, in turn, triggers a signal T to digital cameras 372 and/or 373. Upon receiving the trigger signal T, the digital cameras 372, 373 acquire digital images of the coin rolling on the rail 348. Images can have different pixel resolutions including, for example, 480×640 pixel resolution. In other embodiments, other triggering mechanisms may be used, for example electrical switches positioned in or proximate to the path of a rolling coin. In at least some embodiments, a series of images of the same coin can be obtained using a high speed digital camera. In some embodiments, the triggering mechanism may not be needed. Instead, the camera can be configured to run at certain frame acquisition rate. Some of the acquired frames can be selected for further processing by a software algorithm capable of determining that a coin image is in the frame.
FIG. 4A is a sample digital image 401 of a coin 410. The digital image 401 can be obtained using, for example, the digital image acquisition system shown in FIG. 3. In the embodiment shown in FIG. 4A, the background of the coin 410 is much darker than the coin itself, but other backgrounds are also possible. Background subtraction may be used to depict arbitrary background features. The sample digital image 401 may be a gray image, or a color image which may be converted to a gray image before further processing. The digital image 410 has several aspects that can be used for coin discrimination including, for example, dots 411 around the edge of the coin. For example, the size of the dots 411, their mutual separation, and their distance from the outer edge of the coin 410 vary among coin denominations, and can be used to discriminate the coin 410. Furthermore, lettering 412 and numbers 413 also vary for different coin denominations. Additionally, a centrally located image 414 (of, e.g., a lion) may include several aspects that are useful for coin discrimination, as explained in more detail below. Another aspect for discriminating the coin 410 may be the diameter of the coin. While it is possible to determine a diameter of the coin 410 directly from the digital image, a more robust or accurate diameter determination can be achieved using computer implemented edge detection algorithms known in the art. Such edge detection methods include, for example, Canny, Hough, Marr-Hildreth, Deriche, and Phase Congruency edge detection methods, as explained in more detail below with reference to FIG. 4B.
FIG. 4B shows an image 402 that was generated by executing a Canny edge detection algorithm on the digital image 401 of FIG. 4A. The Canny edge detection method of this embodiment calculates intensity gradients between the neighboring pixels in the image. Large intensity gradients are more likely to correspond to edges than small intensity gradients. In most cases, it is difficult to specify a threshold a-priori at which a given intensity gradient corresponds to an edge. Therefore, the Canny edge detection method makes an assumption that important edges should align along continuous curves in the image. This assumption promotes constructions of a continuous line, while discarding noisy pixels that produce large gradients but do not constitute the continuous line. Other refinements of the basic Canny edge detection method are known in the art. For example, a second or a third derivative of the neighboring pixel intensities can be used to improve the detection results.
In some embodiments, the digital image 402 can be pre-processed by artificially introducing a broad band noise (i.e., a Gaussian noise) to the image which, in turn, reduces the occurrence of the false-positive edge detections. The detected edges can be represented in a binary image, for example the image 402, where each pixel in the image has an intensity of either an edge pixel (e.g., high) or a non-edge pixel (e.g., low). Therefore, the detected edges can be represented as lines having high pixel intensity against a background at low pixel intensity. Various suitable computer programs that perform Canny edge detection methods are available in the public domain. For example, cv::Canny algorithm in the OpenCV computer vision library can be used. Once the edges on the coin surface are determined using a suitable edge detection algorithm, different aspects of the coin can be located more precisely.
For various coin denominations, the dots along the coin edge, lettering, numbering, and images (see, e.g., 411, 412, 413 and 414 respectively; FIG. 4A) stamped on the coins can also contain distinct aspects. However, the processing of a generally round object within a rectangular digital image can be difficult. Therefore, in at least some embodiments of the present technology, a round digital image of the coin 410 can be transformed to a rectangular image, which is better suited for the subsequent processing leading to determining coin denomination. FIG. 5, for example, illustrates an embodiment of a transformed image 500 of the coin 410 as shown in FIG. 4A. The transformed image 500 can be generated by, for example, a computer implementation of a log-polar transform as in Equation 1 below:
where x and y are the locations of the pixels relative to the center of the coin in the digital image shown in FIG. 4. By applying Equation 1, the pixels from the image in FIG. 4A are rearranged into the rectangular image 500 shown in FIG. 5. The horizontal axis of the image 500 corresponds to different θ values on the coin, ranging from 0° to 360° (0 to 2π). Thus, the range from the minimum)(θ=0° to the maximum)(θ=360° on the horizontal axis θ of FIG. 5 corresponds to the full circumference of the coin. The vertical axis R is a logarithm of the distance in mm from the center of the coin. For example, the words “TEN PENCE,” which are at a same radial distance from the center of the coin 410 in FIG. 4A, appear at the same vertical axis R (i.e., R4) in the R-θ graph of FIG. 5. In some embodiments, a generally horizontal orientation of the alphanumerical characters makes the optical character recognition (OCR) easier and/or faster. A computer implemented OCR algorithm can recognize the text “TEN PENCE” in the transformed image 500, and the text can be compared to tabulated values for known coins in a relevant market. In some embodiments, a location of the text “TEN PENCE” can also be used as a criteria for coin discrimination, in addition to or in lieu of the text itself. Other alphanumerical aspects, for example number “10,” can be recognized by an OCR algorithm and used to discriminate coins.
Furthermore, locations of and distance among coin aspects and features can be determined using the transformed image 500 in FIG. 5. For example, in the image 414 of the lion shown in FIG. 4A, the locations of the lion's feet can be determined by identifying the lines that encompass relatively small areas that, in turn, are connected to a larger object (e.g., the body of the lion). Once the locations of the lion's feet are known (e.g., (R3, θ3) and (R1, θ4)), a distance between the feet can be determined using computer implemented image processing algorithms known to a person of ordinary skill in the art. Accordingly, the location of the physical coin features of interest and/or their distances from one another can be used for coin discrimination.
Additionally, the overall richness of the aspects of the coin image 500 in FIG. 5 is generally different at different locations of the image. Therefore, a spectral analysis of the rectangular image 500 of FIG. 5 produces generally different results per different pixel rows or columns. The spectral analysis can be performed using, for example, a Fourier transform, which maps the pixel values at a given row R (or a group of rows R) into a 2D space having a 1/θ as one dimension and Amplitude in decibels (dB) or linear scale as the second dimension. The Fourier transform can be implemented using digital or analog computers. Other types of suitable spectral transforms known to a person skilled in the art can also be used including, for example, Z-transforms and wavelet transforms.
FIGS. 6A and 6B illustrate results of a spectral analysis performed in accordance with embodiments of the present technology on the coin image 500 from FIG. 5. In the graphs shown in FIGS. 6A and 6B, the horizontal axis represents 1/θ and the vertical axis corresponds to the value of spectral amplitude A for the corresponding value of 1/θ. The log-polar transform in Equation 1 discussed above maps the circumferentially located dots 411 in FIG. 4A to a constant R location in FIG. 5 (i.e., R3). FIG. 6A illustrates the spectrum of the coin image along the dots. Because of relatively high regularity of the dots along the row, the corresponding spectral peak (A1*) in the graph in FIG. 6A is localized at a relatively distinct 1/θ (e.g., θ1*) value. Additionally, due to the high differences in the pixel intensity values between the dots and their surroundings, the spectral peak is also relatively high (e.g., A1*).
FIG. 6B illustrates the spectrum of the coin image 500 along a representative location R=R1 in the rectangular image of FIG. 5. At location R1, the size of the coin aspects and their mutual distances are not as uniform as they are along the dots at the edge of the coin. Therefore, the spectral peak A2*in the graph of FIG. 6B is lower and broader (i.e., encompasses more 1/θ values) in comparison to the spectral graph of FIG. 6A. Furthermore, relatively larger distances between the dominant coin aspects at R=R1 shifts the spectral peak (A2*) toward smaller 1/θ values of the horizontal axis. Since the intensity and/or location of the spectral peaks in the graphs corresponds to the coin aspects for particular locations in the rectangular image of FIG. 5, the graphs in FIGS. 6A and 6B can be used as additional aspects for coin discrimination in accordance with embodiment of the present technology.
FIG. 7 is an image 700 of a sample one-dollar coin having several coin features or aspects in accordance with embodiments of the present technology. In some embodiments, the coin image 700 can be transformed to a line image using, for example, a Canny edge detection method as explained above in reference to FIG. 4B, and then the line image can be used for further processing. In some embodiments of the present technology, flat areas 720, 721, and/or 722 can be used for coin discrimination. The flat areas can be detected by, for example, using a digital computer to identify the areas of the coin that are relatively free of lines and/or other features. The shape of the outline or periphery of one or more of the flat areas can be compared to tabulated shapes for known coins to discriminate the coin. In some embodiments, the location, shape and/or mutual distances of the stars 731 can also be identified and compared with tabulated values for known coins in the relevant market. Other relatively well defined aspects of the coin image can be used to discriminate a coin, for example, the locations and mutual distances among the tips 710 of the wing. In some embodiments, coin discrimination based on these coin aspects can be combined with the spectral analysis described with respect to FIGS. 6A and 6B.
FIGS. 8A and 8B are sample images of a one-Euro coin 800, 890 having several coin identification aspects in accordance with embodiments of the present technology. A coin image 800 in FIG. 8A includes a first area 810 (e.g., a central area) having a first color and/or reflective property, and a second area 820 (e.g., an annular area at a periphery of the coin) having a second color and/or reflective property. In some embodiments of the present technology, differences in color and reflectivity of the areas in the image of the coin can be detected by, for example, computer implemented pixel value thresholding algorithm that assigns a predetermined color to the pixels when the range of pixel intensities falls within a prescribed range. The sensitivity of the pixel value thesholding can be tuned by adjusting the acceptable range of pixel intensities. The color and/or reflective properties of the areas 810 and 820 can be compared to tabulated values for known coins to discriminate the coins in accordance with the preset technology.
FIG. 8B shows a plan view 890 and a side view 891 of the sample one-Euro coin 802. The views 890 and 891 may be obtained using, for example, the digital cameras 372 and 373 described in detail above with reference to FIG. 3, and then transformed to line images using, for example, the Canny edge detection algorithm described above with reference to FIG. 4B. The line image in the plan view 890 can be digitally rotated (e.g., through a computer implemented routine) such that lines 880 extend through features 882 in a desired orientation, for example, in a generally vertical orientation. In some embodiments of the present technology, a line 850 can be added to the view 890. For example, the line 850 can be constructed such that it passes through a center of the view 890 at an angle β with respect to the lines 880. The line 850 may intersect selected features of the view 890. For instance, the illustrated line 850 intersects a long axis of the number “1” at an angle α. A person skilled in the art would know techniques such as using MatLab algorithms for measuring the angle between the line 850 and the long axis of the number “1”. In some embodiments of the present technology, the angle α between the illustrated line 850 and the long axis of the number “1” can be feature or aspect used to discriminate the coin 802. Furthermore, distances between the edges in the line image can be calculated including, for example distance X between a foot of number “1” and the nearest point in an outline of the EU membership states (or some other predetermined point). Other aspects in the view 890, for example, a center 871 of the letter “O” in the word EURO and/or a center 870 of the number “1” can also be used to discriminate the coin, either alone or in conjunction with other coin aspects.
The line image of the coin 802 shown in the side view 891 shows two groups of serration lines 860 that are separated by a distance L. In some embodiments, the number of the serration lines can be determined by a computer and used as an aspect to discriminate the coin. Furthermore, a diameter D and a thickness T can also be used as aspects to discriminate the coin. In some embodiments, the coin aspects can be combined and a voting scheme can be established to discriminate the coin against known coins in the market.
From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the various embodiments of the invention. Many of the embodiments of the invention can be implemented using, inter alia, a general purpose digital computer having a processor or an industrial controller having a processor. Additionally, the methods explained with reference to FIGS. 1A-8B above can be combined with the prior art methods based on the mass and metallurgy of the coin. Further, while various advantages and features associated with certain embodiments of the disclosure have been described above in the context of those embodiments, other embodiments may also exhibit such advantages and/or features, and not all embodiments need necessarily exhibit such advantages and/or features to fall within the scope of the disclosure. Accordingly, the disclosure is not limited, except as by the appended claims.
Patent Application
20160364934
