Abstract
Devices and methods for counting planar substrates stacked on a first plane are disclosed. Image capturing sensors are arranged collinearly in a manner substantially perpendicular to the first plane. The image capturing sensors are configured to capture images of portions of counting sides of the stacked planar substrates. The image capturing sensors are configured so that the images captured by every two consecutive image capturing sensors comprise an overlapping portion of the stacked planar substrates.
Claims
1. A device for counting planar substrates stacked on a first plane, comprising: image capturing sensors arranged collinearly, substantially perpendicularly to the first plane, each image capturing sensor being configured to capture an image of a portion of a counting side of the stacked planar substrates, the image capturing sensors being coupled to a preprocessing module for preprocessing the captured images and to identify errors in the counting of the stacked planar substrates, wherein the image capturing sensors are configured so that images captured by every two consecutive image capturing sensors comprise an overlapping portion of the stacked planar substrates.
2. The device according to claim 1, wherein the image capturing sensors are arranged along a frame, the frame being arranged perpendicularly to the first plane.
3.-6. (canceled)
7. The device according to claim 1, wherein each image capturing sensor comprises one or more lens elements and an electronic sensor, wherein the one or more lens elements are configured to capture light from the portion of the counting side of the stacked planar substrates and bring the light to a focus on the electronic sensor.
8. (canceled)
9. The device according to claim 1, further comprising one or more marking elements configured to indicate the overlapping portion on the captured images.
10.-21. (canceled)
22. The device according to claim 1, further comprising an alignment detector configured to indicate an alignment of the stacked planar substrates.
23.-29. (canceled)
30. The device according to claim 1, wherein the preprocessing module is configured to receive the images and apply image recognition algorithms to the images to recognize each substrate of the stack.
31. The device according to claim 1, further comprising a counting processing system for receiving the preprocessed images and counting the stacked planar substrates based on the preprocessed images.
32. The device according to claim 31, wherein the preprocessing module is configured to receive the images and apply image recognition algorithms to the images to recognize each substrate of the stack, and wherein the counting processing system is configured to implement counting algorithms to count the recognized substrates.
33.-34. (canceled)
35. The device according to claim 1, wherein the stacked planar substrates are stacks of security documents, stacks of sheets of security documents or stacks of substrate sheets used in the production of security documents.
36.-40. (canceled)
41. A method of counting planar substrates stacked on a first plane, comprising: capturing multiple images of the stacked planar substrates, the multiple images containing a complete counting side of the stacked planar substrates, wherein each image contains a portion of the complete counting side, wherein any two consecutive images captured comprise an overlapping part of the complete counting side; preprocessing the captured images; identifying the overlapping parts of each of the two consecutive captured images; identifying each individual substrate; counting the identified individual substrates; and identifying errors in the counting of the identified individual substrates.
42. The method according to claim 41, further comprising identifying each individual substrate in each captured image and counting each substrate only once based on the identification of the overlapping parts.
43.-45. (canceled)
46. The method according to claim 41, further comprising identifying errors in a placement of the stack.
47. (canceled)
48. The method according to claim 41, wherein the identifying each individual substrate comprises identifying each substrate with a certainty above a predetermined threshold.
49.-50. (canceled)
51. Non-transitory computer readable medium storing a program that causes a computer to: capture multiple images of stacked planar substrates, the multiple images containing a complete counting side of the stacked planar substrates, wherein each image contains a portion of the counting side, and wherein any two consecutive images captured comprise an overlapping part of the counting side of the stacked planar substrates; preprocess the captured images; identify the overlapping parts of the two consecutive captured images; identify each individual substrate of the stacked planar substrates; count the identified individual substrates; and identify errors in the counting of the identified individual substrates.
52. The method according to claim 41, further comprising using a marking element to indicate the overlapping portion on the captured images.
53. A device for counting planar substrates stacked on a first plane, comprising: one or more image capturing sensors arranged substantially perpendicularly to the first plane, the one or more image capturing sensors being configured to capture images of a counting side of the stacked planar substrates, a preprocessing module coupled to the one or more image capturing sensors, the preprocessing module being configured to receive and preprocess the captured images and to identify individual substrates in the counting of the stacked planar substrates.
54. The device according to claim 53, the preprocessing module further being configured to identify errors in a placement of the substrates.
55. The device according to claim 53, further comprising a counting processing system configured to implement counting algorithms to count the identified individual substrates.
56. The device according to claim 55, the counting processing system further being configured to implement counting algorithms to identify errors in the counting of the stacked planar substrates.
57. The device according to claim 53, further comprising one or more marking elements configured to indicate an overlapping portion on the captured images.
Description
BRIEF DESCRIPTION
[0041] FIGS. 1a and 1b illustrate image capturing sensors arranged collinearly along the same plane, according to example implementations.
[0042] FIG. 1c, illustrates image capturing sensors arranged in parallel columns, according to an example implementation;
[0043] FIG. 1d illustrates image capturing sensors arranged in an array on the same plane, according to an example implementation;
[0044] FIG. 2 schematically illustrates an image capturing phase of a device for counting planar substrates according to an example;
[0045] FIGS. 2a to 2d schematically illustrate an image matching phase of a device for counting planar substrates according to an example;
[0046] FIG. 3a illustrates a part of device for counting planar substrates with a laser line beamer, according to an example;
[0047] FIGS. 3b and 3c schematically illustrate a line beam on misaligned stacked planar substrates;
[0048] FIG. 4a illustrates a set of image capturing sensor modules, according to an example.
[0049] FIG. 4b-4d illustrate a multi-lens arrangement for a laser marking element, according to an example;
[0050] FIGS. 5a and 5b illustrate front and back views of a device for counting planar substrates, according to an example;
[0051] FIG. 5c illustrates an exploded view of a device for counting planar substrates, according to an example;
[0052] FIG. 5d illustrates a device for counting planar substrates with protective transparent flat element, according to an example;
[0053] FIGS. 6a and 6b illustrate front and side views of a device for counting planar substrates with a moveable lid in stand-by position;
[0054] FIGS. 6c and 6d illustrate front and side views of a device for counting planar substrates with a moveable lid pressing against the stacked planar substrates;
[0055] FIG. 7 illustrates an arrangement of multiple devices for counting planar substrates according to an example;
[0056] FIG. 8 illustrates another arrangement of multiple devices for counting planar substrates according to another example;
[0057] FIG. 9a illustrates an example device for counting planar substrates wherein a counting processing system is integrated in the device;
[0058] FIG. 9b illustrates an example wherein a counting processing system is distributed between a device for counting planar substrates and an external processing device;
[0059] FIG. 9c illustrates an example wherein a counting processing system is external to an arrangement for counting planar substrate;
[0060] FIG. 10 is a flow chart of a method of counting stacked planar substrates, according to an example.
DETAILED DESCRIPTION
[0061] FIGS. 1a and 1b illustrate image capturing sensors arranged collinearly along the same plane, according to example implementations. FIG. 1a illustrates a device 100A having multiple image capturing sensors (10-1 to 10-n) arranged collinearly on a frame 20. Each image capturing sensor comprises a light-sensitive element, such as an electronic sensor or a photographic film, and a lens element (11-1 to 11-n) to focus the image on the corresponding light-sensitive element. The lens element may be a single lens or a plurality of lenses arranges consecutively to enhance the focus of the image. FIG. 1b illustrates a device 100B having multiple frames 20-1 to 20-n arranged collinearly along the same plane. Each frame comprises an image capturing sensor. The frames 20-1 to 20-n may be arranged so that the image capturing sensors are substantially collinear with each other. Each image capturing sensor may capture an image that includes a portion of a stack of planar substrates. Any two images captured by consecutive sensors, e.g. 10-1 and 10-2, may comprise a common portion, i.e. a portion of the stack that appears in both images. By merging the images it is possible to reconstruct the whole stack with an adequate level of analysis to identify the single substrates and count the whole stack.
[0062] FIG. 1c illustrates image capturing sensors arranged in parallel columns, according to an example implementation. Device 100C may comprise a frame 30. A first set of image capturing sensors 100-11 to 100-n1 may be arranged in a first column and a second set of image capturing sensors 100-12 to 100-n2 may be arranged in a second column, respectively. The second column may be on the same plane as the first column or on another plane. Each set may capture images along a different line of a stack of planar substrates. The substrates may be identified separately for each set of images. It is thus possible to identify errors, e.g. folded or misaligned substrates, that may appear only in one of the sets of images. Accordingly, a counting process may take place for each set of images. By comparing the results of each counting process it may be possible to increase the accuracy of the counting process.
[0063] FIG. 1d illustrates image capturing sensors arranged in an array on the same plane, according to an example implementation. Image capturing sensors 100-11 to 100-nm are arranged in collinear columns and rows on a frame 120. Each column of sensors may be arranged to capture images along a different line of the same stack of planar elements. Then the images may be merged to form a single extended image. The planar substrates may subsequently be identified and counted from the single merged image. By generating a single extended image a wider area of the stack may be inspected. Consequently it may be easier to identify errors during the substrate identification process or during the counting process and thus achieve a counting result with a higher degree of certainty. The errors may be partially or fully folded substrates or an incorrect placement or misalignment of a substrate in the stack.
[0064] FIG. 2 schematically illustrates an image capturing phase of a device for counting planar substrates according to an example. A stack of planar substrates 290 may be placed in front of the image capturing sensors 210 of device 200. The image capturing sensors 210 may be arranged on a frame 204. The stack may have a height H. The stack 290 and the lens elements 214 of the image capturing sensors 210 may define a first distance d1. Two centers of consecutive image capturing sensors may define a second distance d2. The focused part of the captured image of each image capturing sensor may be defined as d3. The overlapping portion of two consecutive images may define a distance d4.
[0065] The required detail level of the image may be given by the minimum thickness of individual substrates in the stack and the minimum thickness of gaps (the space) between two adjacent substrates, which need to be greater or equal to the pixel size of the image in order to distinguish between two adjacent substrates and the gaps between them in the captured image. Therefore, the thinner the substrates, the higher the required detail level. A higher detail level may be obtained by decreasing the distance d1.
[0066] Moreover, the following relations can be established: [0067] (i) d2<d3, i.e. the focused part of the image needs to be wider than the size of d2 which is the sensor or frame size plus the space between the consecutive sensors or frames, so that an overlapping area may exist. [0068] (ii) d4>0, i.e. the overlapping area needs to be defined in the focused part of the image)
[0069] If an increased detail level is required, the distance d1 may need to decrease. As a result d3 may decrease and consequently d2 may need to decrease too in order to have a non-negative overlapping distance d4. Reducing d2 may imply having a smaller gap between the sensors or frames, or, if further size decrement is required, smaller sensors or frames.
[0070] The device 200 may further comprise a base 202 and a moveable lid 260. The moveable lid may be coupled to the frame 204. It may be used to press against the top substrate of the stack 290. This may allow a more uniform distribution of the substrates to facilitate their identification. Furthermore, it may reduce the ambient light that reaches the image capturing sensors that may hinder the substrate identification process. The interior of the moveable lid 260 may be colored or patterned so that the topmost substrate may be easily defined. Accordingly, the base 202 may be colored or patterned so that the bottommost substrate may be easily defined.
[0071] s FIGS. 2a to 2d schematically illustrate an image matching phase of a device for counting planar substrates according to an example.
[0072] In order to join two adjacent images accurately some reference projected or marked on the stack may be required. Any reference that is not marked on the stack may make the image merging precision to decrease significantly, as it may be highly susceptible to different perspectives of the image due to errors in positioning or alignment between the image capturing sensors and the stack of planar substrates.
[0073] In one implementation, a laser module may project a reference mark directly on the stack. In the example of FIG. 2a point lasers are used. In this example, the number of lasers is n1 and the number of image capturing sensors is n arranged on a frame 204 of device 200. This is because n images may be captured along a line of stacked planar substrates and between the n images there may be n1 overlapping portions. Therefore, the marking elements may only indicate the n1 overlapping portions. For that reason, each marking element may be placed so that its center, i.e. the pointing direction of the laser beam, lies substantially on a plane coinciding with a plane passing at the border between two image capturing sensors. However, in other implementations, the capturing modules may be placed at other positions provided that the laser beam is pointing at the overlapping portion of the stacked planar substrates.
[0074] The image capturing sensor 210-i may capture an image Ci and the image capturing sensor 210-(i+1) may capture an image C-(i+1), respectively, of a portion of the stack 290. The overlap region Z indicated in the image may form part of both images. The i-th marking element may indicate the zone in both images with a beam projecting a mark at the overlapping zone of the stack. It may thus be possible to merge the two images into one by matching the overlap region with the help of the marking point of the beam on the substrates.
[0075] FIGS. 2b, 2c and 2d illustrate how the images captured by the image capturing sensors 210-(i) and 210-(i+1) would be used to form the merged image C-{i, i+1}. FIG. 2b shows the image Ci captured by i-th sensor. The marking point of the laser pointer may be seen at the upper part of the image. FIG. 2c shows the image C-(i+1) captured by (i+1)-th sensor. The marking point of the laser pointer may be seen at the lower part of the image. As both images contain the marking point it may be assumed that there is an overlapping zone Z between the images. By using the help of the marking point of the beam on the substrates, it may be possible to merge the two images into one by matching the overlap region. This is shown in FIG. 2d.
[0076] FIG. 3a illustrates a part of a device for counting planar substrates with a laser line beamer, according to an example. The device 300 may comprise collinear image capturing sensors 310 and a laser line beamer 370 arranged in parallel to the image capturing sensors 310. The laser line beamer may project a line beam towards the stack of planar substrates. The laser line beamer may be placed at a distance d5 from the image capturing sensors in order to project the line at an angle. The purpose of the laser line beamer is to indicate a misaligned stack of substrates that could generate errors during the counting process. A misaligned stack may be defined as a stack where the horizontal distance (d1 in FIG. 2) of its substrates from the sensors may not be constant for all the substrates.
[0077] FIG. 3b schematically illustrates a line beam on misaligned stacked planar substrates. FIG. 3b corresponds to the image as would be taken by the image capturing sensors. Without the line beam, it may not be possible to distinguish between aligned and misaligned substrates. However, the line laser may project a line perpendicularly to the substrates and at a certain angle. A local deviation may be seen around the middle of the stack. FIG. 3c shows the stack from a side where the misalignment may be identified and corrected before the counting process may begin. The stack is shown placed against a partition 304 of the device 300. Some substrates are misaligned with respect to the rest and with respect to the partition 304. It is noted that the misalignment may also be detected with the use of an image capturing sensor viewing the stack from the point of view of FIG. 3c, i.e. from a side perpendicular to where the image capturing sensors are used to capture the counting side of the stack. Alternatively or additionally, 3D or stereoscopic cameras may be used in place of the line laser to generate a 3D representation of the stack where any misalignment may then be identified. In case of 3D or stereoscopic cameras, they may be placed either on the same plane as the image capturing sensors 310 or on another plane.
[0078] FIG. 4a illustrates an example implementation of image capturing sensor modules arranged along the same plane. Each image capturing sensor module 405 comprises a rectangular frame. The rectangular frame may host an image capturing sensor 410, a power supply port 402 and a processing element 401. The module's 405 size and shape allows for the image capturing sensor 410 and any other electronic elements to be mounted on it and also allows for various modules to be collocated on the same plane so that the image capturing sensors 410 to be collinearly aligned. Each image capturing sensor may comprise a light-sensitive element 412 and a lens element 414. In the example of FIG. 4a, the lens element 414 comprises a single lens. However, in other implementations the lens element may comprise a plurality of lenses arranged consecutively to enhance the captured image.
[0079] FIGS. 4b to 4d illustrate a multi-lens arrangement for a laser marking element, according to an example. The laser marking element 420 may comprise a laser module 421, a secondary focusing lens 424 and a jacket element 426. The laser module 421 may comprise a body, housing the laser beam generating electronics, and a primary focusing lens 422 placed at the firing hole of the laser module 421. The jacket element 426 may comprise a jacket and a window 427. FIG. 4b is an exploded view of the parts of the multi-lens laser marking element. FIG. 4c illustrates the secondary focusing lens 424 placed on top of the primary focusing lens 422. FIG. 4d illustrates the jacket element 426 housing the laser module 421 so that the two focusing lenses 422 and 424 may form a composite lens element to enhance the beam generated by the laser module 421.
[0080] FIGS. 5a and 5b illustrate front and back views of a device for counting planar substrates, according to an example. FIG. 5c illustrates an exploded view of the device. The device 400 may comprise a casing 430. The casing may be fixed on a base 435 and may comprise a wall 432, perpendicular to the base and partitions 430a-430c, extending vertically from one side (front side) of the wall. In the example of FIGS. 5a and 5b, the casing comprises 3 partitions, 430a, 430b and 430c. Image capturing sensor modules 405 may be fixed on the other side of the wall (back side). The casing may comprise sensor openings so that the image capturing sensors 410 of the image capturing sensor modules 405 may protrude from the sensor openings of the casing to capture images from the front side of the wall. In the example of FIGS. 5a and 5b, the image capturing sensors 410 form two sets of image capturing sensors. Each set of image capturing sensors may be arranged collinearly to capture images along a line. The casing may further host marking elements 420. Between partitions 430a and 430b, the casing may host a first set of image capturing sensors 410 and a first set of marking elements 420. Accordingly, between partitions 430b and 430c the casing may host a second set of image capturing sensors 410 and a second set of marking elements 420. The image capturing sensor modules 405 may be fixed on the back side of the wall 432 with screws 434. The image capturing sensors 410 may be fixed from the front side of the wall with flanges 436 that may be screwed to the wall with screws 438. The flanges 436 may comprise an opening for allowing light to reach the light-sensitive elements of the image capturing sensors 410. The flanges may further serve as fixtures for additional focusing lenses 414 for the lens element of the image capturing sensors 410. This is better illustrated in FIG. 4c. Now, the marking elements 420 may be laser marking elements. Each marking element 420 may be fixed to the casing with screws so that the marking beam, e.g. the laser beam, may point at the stacked planar substrates at an angle in order to not distort the captured image. The marking elements may be fixed partly on the wall and partly on a partition in order to point at an angle. In the example illustrated, a first set of marking elements may be fixed between partition 430b and the part of the wall 432 that extends between partition 430a and 430b and a second set of marking elements may be fixed between partition 430b and the part of the wall 432 that extends between partition 430b and 430c. The first set of marking elements 420 may point at an angle towards the opening between partitions 430a and 430b. The second set of marking elements 420 may point at an angle towards the opening between partitions 430b and 430c. Each marking element may comprise a laser module 421, a secondary focusing lens 424 and a jacket element 426. The casing 430 may comprise sockets 439 to host the laser modules 420 and to provide power to the laser modules 420.
[0081] In the example of FIGS. 5a, 5b and 5c each set of image capturing sensor modules comprises four image capturing sensor modules. Furthermore, there are three marking elements 420 for each set of four image capturing sensor modules.
[0082] The device 400 may further comprise light emitting modules 440 to illuminate the stacked planar substrates. A first light emitting module may be arranged along the edge of partition 430a in a direction perpendicular to the base 435. A second light emitting module may be arranged along the edge of partition 430b, accordingly. Each light emitting module may comprise a number of light emitting elements, e.g. LEDs, fluorescent illumination, or any other type of illumination.
[0083] During a counting process, a stack of planar substrates, e.g. a stack of banknotes, may be placed in front of the device 400, i.e. against the edges of the partitions 430a-430c. The plane of the substrates may be perpendicular to the wall 432 and to the partitions 430a-430c.
[0084] The device 400 is configured to capture two sets of images of two areas of the stack. In other implementations, the device may comprise only one set of image capturing sensors and capture only one set of images. In yet other implementations 3 or more sets of image capturing modules may be used to capture 3 or more sets of images. Furthermore, although four image capturing sensors are illustrated, other implementations with less or more image capturing sensors are possible. The selection of the number of sensor may depend on the thickness of the substrates, the thickness (size) of the stack and/or the number of substrates in the stack. The device may further be extensible. That is, the casing may be expandable so that more image capturing sensor modules to be connectable to the casing. For example, in one implementation two or more casings may be connectable one on top of the other to provide the expandability.
[0085] FIG. 5d illustrates a device for counting planar substrates with a protective transparent element 455, according to an example. The partitions may each comprise a slot, parallel to the edge of the partitions and next to the light emitting modules. The slots may receive the protective transparent elements 455. The purpose of the protective transparent elements 455 is to protect the sensitive elements of the device, e.g. the image capturing sensors or the marking elements, from coming in contact with the stacked planar substrates while at the same time it may permit the images to be captured and the marking beams to be pointing at the overlapping portions of the substrates. The protective transparent elements 455 may be removable so they can be easily cleaned or replaced, if required.
[0086] FIGS. 6a and 6b illustrate front and side views of a device for counting planar substrates with a moveable lid 460 in repose stand-by position. FIGS. 6c and 6d illustrate front and side views of a device for counting planar substrates with the moveable lid 460 pressing against stacked planar substrates 490. The device, in its other characteristics, may be similar to the devices discussed above. The lid may be moveable between a stand-by position and a pressing position. A rotation mechanism 480 may be coupled to the moveable lid to rotate the lid between the repose position and the pressing position. The rotation mechanism 480 may comprise an arm 477, fixedly attached to the lid at one end, and a rotatable element, such as a disc 478, fixedly attached to the other end of the arm 477. An actuator 479, either manual or electric, may rotate the rotatable element and consequently the lid between the two positions. The rotation mechanism may be attached to the casing or it may be attached to the base 435 of the device.
[0087] FIG. 7 illustrates an arrangement of multiple devices for counting planar substrates according to an example. A first device D1 may be placed at a first corner of a stack of planar substrates S. It may comprise two sets of image capturing sensors. A first set of image capturing sensors 310-1a may capture images along a first plane of the stack. A second set of image capturing sensors 310-1b may capture images along a second plane of the stack. A second device D2 may be placed at a second corner of the stack of planar substrates. It may also comprise two sets of image capturing sensors. A third set of image capturing sensors 310-2a may capture images along the first plane of the stack. A fourth set of image capturing sensors 310-2b (not visible) may capture images along a third plane of the stack, parallel to the second plane.
[0088] FIG. 8 illustrates another arrangement of multiple devices for counting planar substrates according to another example. Devices D10-D15 are arranged around the stack of planar substrates S. Devices D10 and D11 may capture images along a first plane of the stack, devices D12 and D13 may capture images along a second plane of the stack, device D14 may capture images along a third plane of the stack, parallel to the first plane, and, finally, device D15 may capture images along a fourth plane of the stack, parallel to the second plane.
[0089] In the examples arrangements of FIGS. 7 and 8, the stack of planar substrates may be manually or automatically placed in a counting position. Alternatively, the devices may be moveable, manually or automatically in order to be placed against the corners or sides of the stack S.
[0090] Once the images are captured, they may be processed so that any counting algorithms to be performed on the processed images. The processing may be local to the image capturing device, remote or distributed. FIG. 9a illustrates an example device for counting planar substrates wherein a counting processing system is integrated in the device P1. The image capturing device may contain a processing unit integrated in the device. The processing unit may be programmed to configure the parameters of the image capturing device and also the information received from the image capturing sensors, i.e. merge the images and perform counting algorithms. The result of the processing may be the number of substrates in a stack of planar substrates S.
[0091] FIG. 9b illustrates an example wherein a counting processing system is distributed between a device P2a for counting planar substrates and an external processing device P2b. The image capturing device P2a may be connected with a cable or wirelessly to the external processing device. For example, the image capturing device P2a may be programmed to capture the images and transmit them to the external processing device P2b. The external processing device P2b may be programmed to receive the images and perform the image merging and the counting algorithms. Alternatively, the image capturing device after performing the image capturing may perform part or all of the rest of the processes required, e.g. image combining, counting, error identification and the external processing device may perform the rest and/or validate the result.
[0092] FIG. 9c illustrates an example wherein a counting processing system is external to an arrangement for counting planar substrate. The arrangement may comprise image capturing devices P3a1 and P3a2. Each device may transmit the raw images or the merged processed images to the external processing system P3b. The external processing system P3b may then perform the merging and counting algorithms, as required, based on the information received from the various image capturing devices.
[0093] In the above mentioned example arrangements, a master-slave implementation may also be possible. That is, an image capturing device may act as a server (master) that may collect the images or the results from the other image capturing devices (slaves or clients) and perform counting algorithms or validation algorithms, i.e. algorithms for comparing the results the acquired by the client devices.
[0094] FIG. 10 illustrates a method of counting stacked planar substrates according to an example. In a first step 505, multiple images of the stacked planar substrates may be captured along a plane. The step may comprise capturing sets of multiple images at different areas of the stack on the same plane or at different planes. Then, in step 510, the overlapping parts of consecutive captured images may be identified. In some cases, marking spots, e.g. laser spots on consecutive (adjacent) images may be used as points of reference to identify the overlapping parts. In other cases, e.g. when the size of the laser spots coincides with more than one piece of analyzed substrates, the coordinates of the centers of the laser spots detected on adjacent images may be used to select the position of larger areas of the image, which may be utilized as templates to match the overlapping areas. A template matching algorithm may then be applied in order to find the position of best correlation between the two areas. This position may be used to calculate a frontier substrate. In step 515, the individual substrates may be identified. During the identification step it may be possible to digitally process the images, e.g. perform edge enhancement filters, to facilitate the identification of individual substrates and detect errors. If an error is identified in 517, then the process may be restarted in 505. In step 520 the identified substrates may be counted. Again, if an error is detected after counting then the process may need to be restarted. The identification may be implemented on the individual captured images and, taking into consideration the identified overlapping part, make sure that each substrate is counted only once. Alternatively, the captured images may be combined to generate a composite image and each substrate may be identified on the composite image. Counting algorithms may thus be applied either to the individual images or to the output composite image. Finally, in step 525, the results may be validated. For example, if various counts are performed, e.g. at different areas of the stack, then the results may be compared. If they coincide the count may be validated. Otherwise, a majority vote may determine the correct result or the process may need to be repeated.
[0095] Although only a number of particular embodiments and examples have been disclosed herein, it will be understood by those skilled in the art that other alternative embodiments and/or uses and obvious modifications and equivalents thereof are possible. Furthermore, the disclosure covers all possible combinations of the particular embodiments described. Thus, the scope of the disclosure should not be limited by particular embodiments.
[0096] Further, although the examples described with reference to the drawings comprise computing apparatus/systems and processes performed in computing apparatus/systems, the disclosure also extends to computer programs, particularly computer programs on or in a carrier, adapted for putting the system into practice.
