Position measurement system and lighting condition optimization system

Abstract

To reduce variation in measurement value of a relative position to a form element even when the position relation between an imaging device and a work changes.SOLUTION: The present invention relates to a position measurement system which measures the relative position of a form element of a three-dimensional object that a work comprises targeting form elements of the work and three-dimensional object, and the position measurement system comprises: an imaging device which images the work; a lighting device which is used as a light source for the imaging by the imaging device, and can have lighting conditions on the work changed; an imaging processing part which uses an image of the work to find the relative position; a lighting condition specification part which specifies suitable lighting conditions of the lighting device under which change in relative position found by the image processing part due to change in position relation between the imaging device and work in the imaging of the work becomes small; and a measurement control part which allows the imaging device to image the work under the suitable lighting conditions and uses the obtained image of the work to let the image processing part find the relative position.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] This invention relates to a position measurement system and a lighting condition optimization system. [Background technology]

[0002] When mounting LED elements onto a circuit board, the LED elements must be mounted in the correct position on the board to ensure positional accuracy between the LED and the lens that receives the light emitted from the LED. Therefore, an inspection of the LED mounting position is performed.

[0003] Patent Document 1 describes a method for detecting the position of a representative mark formed on a carrier and the mounting position of the LED element on the carrier, by optically recognizing a carrier holding a substrate on which an LED element has been mounted, and determining the relative position of the mounting position with respect to the representative mark. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2014-179186 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, for rounded three-dimensional objects such as LED elements, fluctuations in the direction of light illuminating the object for imaging can change the state of shading on the object's surface, potentially causing fluctuations in positional measurements. In situations where substrates are transported on a conveyor belt while imaging occurs, variations in the positional relationship between the imaging device, lighting device, and substrate during imaging can occur, causing fluctuations in the direction of light illuminating the three-dimensional objects on the substrate, which can also lead to fluctuations in positional measurements. Conventional methods, such as those described in Patent Document 1, assumed that there would be no variation in the positional relationship between the imaging device, the illumination device, and the substrate during imaging. Therefore, the possibility of the above-mentioned fluctuations in measurement values ​​was not recognized.

[0006] The present invention aims to reduce fluctuations in the measured relative position of a three-dimensional morphological element, such as an LED element, attached to a workpiece such as a substrate, even when the positional relationship between the imaging device and the workpiece changes. [Means for solving the problem]

[0007] A position measurement system according to one embodiment of the present invention is a position measurement system for measuring the relative position of a morphological element with respect to a workpiece, with respect to a workpiece and a three-dimensional morphological element provided on the workpiece, comprising: an imaging device for imaging the workpiece; an illumination device used as a light source for imaging by the imaging device and capable of changing the illumination conditions for the workpiece; an image processing unit for determining the relative position using an image of the workpiece; an illumination condition identification unit for identifying suitable illumination conditions for the illumination device that reduce the fluctuation of the relative position determined by the image processing unit, which occurs due to fluctuations in the positional relationship between the imaging device and the workpiece when an image of the workpiece is captured; and a measurement control unit that causes the imaging device to image the workpiece under the suitable illumination conditions and causes the image processing unit to determine the relative position using the captured image of the workpiece.

[0008] According to the above configuration, when measuring the relative position of three-dimensional morphological elements attached to a workpiece with respect to the workpiece, even if the positional relationship between the imaging device and the workpiece changes, the fluctuation in the measured value of the relative position of the morphological elements with respect to the workpiece can be reduced.

[0009] Furthermore, the morphological element may be a one-dimensional morphological element, and the image processing unit may determine the relative position by taking the intersection point of the search line and the one-dimensional morphological element as the position of the morphological element.

[0010] Also, the morphological element is a two-dimensional morphological element, and the image processing unit may obtain the relative position by using the representative position of the two-dimensional morphological element specified in the search area as the position of the morphological element.

[0011] Also, the morphological element is a plurality of one-dimensional morphological elements, and the image processing unit obtains the positions of intersections between one search line among the plurality of search lines and one morphological element among the plurality of one-dimensional morphological elements for a plurality of pairs of the one search line and the one morphological element, and obtains the relative position by using the representative position obtained based on the obtained positions of the plurality of intersections as the positions of the plurality of one-dimensional morphological elements.

[0012] Also, the suitable illumination condition specified by the illumination condition specifying unit is such that the images used for specifying the suitable illumination condition are images of a plurality of the workpieces, and include a plurality of images in which the positional relationships between the imaging device and the workpiece for one workpiece are different from each other. Further, when values regarded as the true values of the relative positions for each workpiece are available, the illumination condition can be set such that the total of the variations in the relative positions for each workpiece among the plurality of workpieces becomes small.

[0013] Also, the suitable illumination condition specified by the illumination condition specifying unit is such that the images used for specifying the suitable illumination condition are images of a plurality of the workpieces, and include a plurality of images in which the positional relationships between the imaging device and the workpiece for one workpiece are different from each other. In this case, the illumination condition can be set such that the total of the variations in the relative positions for each workpiece among the plurality of workpieces becomes small.

[0014] Furthermore, the lighting condition identification unit may, when the workpiece is provided with a plurality of three-dimensional morphological elements, identify the preferred lighting conditions for each three-dimensional morphological element, and the image processing unit may determine the relative position for each of the plurality of three-dimensional morphological elements provided on the workpiece using an image of the workpiece captured under the preferred lighting conditions corresponding to the three-dimensional morphological element to be processed.

[0015] Furthermore, the system may include a virtual image generation unit that generates a virtual image of the workpiece based on images of the workpiece taken under multiple lighting conditions, which would be obtained if the workpiece were photographed under lighting conditions different from those used for the original photograph. The image processing unit may determine the relative position even when the image of the workpiece is a virtual image, and the lighting condition identification unit may identify the preferred lighting conditions that minimize the variation in the relative position determined for the virtual image, or for the captured image of the workpiece and the virtual image.

[0016] Furthermore, the system may also include a determination unit that determines the amount of deviation of the relative position, which is determined by the image processing unit, from a reference position, and determines whether the relative position is good or bad based on the amount of deviation.

[0017] A lighting condition optimization system according to one embodiment of the present invention is a lighting condition optimization system that optimizes the lighting conditions for illumination during imaging to measure the relative position of a morphic element with respect to a workpiece, with respect to a workpiece and a three-dimensional morphic element provided on the workpiece, comprising: an imaging device for imaging the workpiece; a lighting device used as a light source for imaging by the imaging device and capable of changing the lighting conditions for the workpiece; an image processing unit for determining the relative position using an image of the workpiece; and a lighting condition specification unit for specifying suitable lighting conditions for the lighting device such that the fluctuation of the relative position determined by the image processing unit, which occurs due to fluctuations in the positional relationship between the imaging device and the workpiece when an image of the workpiece is captured, becomes small.

[0018] According to the above configuration, when measuring the relative position of three-dimensional morphic elements provided on a workpiece with respect to the workpiece, it is possible to provide illumination conditions that can reduce fluctuations in the measured value of the relative position of the morphic elements with respect to the workpiece, even if the positional relationship between the imaging device and the workpiece changes.

[0019] A position measurement system according to one embodiment of the present invention is a position measurement system for measuring the relative position of a morphic element with respect to a workpiece, with respect to a workpiece and a three-dimensional morphic element provided on the workpiece, comprising: an imaging device for imaging the workpiece; an illumination device used as a light source for imaging by the imaging device and capable of changing the illumination conditions for the workpiece; an image processing unit for determining the relative position using an image of the workpiece; an illumination condition identification unit for acquiring predetermined preferred illumination conditions for the illumination device that reduce the fluctuation of the relative position determined by the image processing unit, which occurs due to fluctuations in the positional relationship between the imaging device and the workpiece when an image of the workpiece is captured; and a measurement control unit that causes the imaging device to image the workpiece under the preferred illumination conditions and causes the image processing unit to determine the relative position using the captured image of the workpiece.

[0020] According to the above configuration, when measuring the relative position of three-dimensional morphological elements provided on a workpiece with respect to the workpiece, by utilizing specified suitable illumination conditions, it is possible to reduce fluctuations in the measured value of the relative position of the morphological elements with respect to the workpiece even if the positional relationship between the imaging device and the workpiece changes. [Effects of the Invention]

[0021] According to the present invention, when measuring the relative position of a three-dimensional morphological element provided on a workpiece with respect to the workpiece, even if the positional relationship between the imaging device and the workpiece changes, the fluctuation in the measured value of the relative position of the morphological element with respect to the workpiece can be reduced. [Brief explanation of the drawing]

[0022] [Figure 1] A schematic diagram showing an example of a position measurement system 1 according to an embodiment of the present invention. [Figure 2] A schematic diagram of an illumination device LS integrated with a camera 102 according to an embodiment of the present invention. [Figure 3] A diagram showing the XZ cross-section of the lighting device LS according to an embodiment of the present invention. [Figure 4] A bottom view of the lighting device LS according to an embodiment of the present invention. [Figure 5] A schematic diagram showing the hardware configuration of a control device included in a position measurement system 1 according to an embodiment of the present invention. [Figure 6] A schematic diagram showing an example of the functional configuration of a position measurement system 1 according to an embodiment of the present invention. [Figure 7] A diagram showing the operation stages of the position measurement system 1 according to an embodiment of the present invention. [Figure 8] A diagram showing a circuit board on which components are mounted, which is the object to be measured in an embodiment of the present invention. [Figure 9] A diagram illustrating the variation in the shadow region occurring in a component according to an embodiment of the present invention. [Figure 10] A diagram illustrating the position measurement of a one-dimensional marker according to an embodiment of the present invention. [Figure 11] A diagram illustrating the position measurement of a two-dimensional marker according to an embodiment of the present invention. [Figure 12] A diagram illustrating the measurement of a position determined from a plurality of one-dimensional markers according to an embodiment of the present invention. [Figure 13] A figure showing an example of a base emission pattern according to an embodiment of the present invention. [Modes for carrying out the invention]

[0023] Hereinafter, embodiments relating to one aspect of the present invention (hereinafter also referred to as "this embodiment") will be described based on the drawings. However, the embodiments described below are merely illustrative examples of the present invention in all respects. Needless to say, various improvements and modifications can be made without departing from the scope of the present invention. In other words, when implementing the present invention, specific configurations according to the embodiments may be appropriately adopted.

[0024] Figure 1 is a schematic diagram showing an example of a position measurement system 1 according to the present invention. The position measurement system 1 measures the relative position of three-dimensional morphological elements on the workpiece 4 with respect to the workpiece by performing image processing on an input image obtained by capturing an image of the workpiece 4 being transported on a belt conveyor 2. The workpiece 4 is, for example, a circuit board on which LED elements are mounted. The LED elements are an example of three-dimensional morphological elements on the workpiece 4.

[0025] A camera 102, which functions as an imaging device with an integrated lighting device LS, is positioned above the belt conveyor 2, and the imaging field 6 of the camera 102 is configured to include a predetermined area of ​​the belt conveyor 2. Here, the lighting device LS can be a multi-channel lighting device such as an MDMC (Multi Direction Multi Color) lighting device, and more specifically, the lighting device described in Japanese Patent Application No. 2018-031747 by the present applicant can be given as an example.

[0026] Figure 2 is a schematic diagram of the illumination device LS integrated with the camera 102. As shown in Figure 2, the direction from which light is emitted from the illumination device LS is the Z-axis, the left-right direction of the paper is the X-axis, and the axis perpendicular to the X and Z axes is the Y-axis. The side from which light is emitted is considered the bottom, and when facing the illumination device LS from the position labeled "Front" in Figure 2, the right side is the right, the left side is the left, the front side is the front, and the back side is the rear. The illumination device LS is controlled by the processing unit 10 via the camera 102. An opening 46 is provided at the top of the illumination device LS so that the camera 102 can image the object W from above the illumination device LS.

[0027] Figure 3 shows the XZ cross-section of the illumination device LS (the XZ cross-section viewed from the position indicated as "Front" in Figure 2), and Figure 4 is a bottom view of the illumination device LS. As shown in Figures 3 and 4, the illumination device LS, as a multi-channel illumination device, has multiple channel illumination units LSi. More specifically, as shown in Figure 4, the illumination device LS has one circular channel illumination unit LSiC in the center in a plan view, and 12 fan-shaped channel illumination units LSi arranged concentrically around it. The light emitted from the central channel illumination unit LSiC hits the reflector 47, as shown in Figure 3, and is reflected downwards. In this case, the illumination device LS is composed of a total of 13 channel illumination units LSi, and if each channel illumination unit LSi emits three colors, the number of default monochromatic and monochannel illumination emission patterns is 13 × 3 = 39 patterns. Furthermore, the image data generated by the camera 102 is transmitted to the processing unit 100. Image capture by the camera 102 is performed periodically or event-wise.

[0028] Furthermore, the lighting device LS may be a multi-channel lighting device or a movable lighting device. A movable lighting device is a lighting device in which the lighting unit is separated from the camera 102, and the lighting direction relative to the workpiece 4 can be changed by mechanically moving the position of the lighting unit. The lighting direction when using a movable lighting device is also an example of a lighting condition.

[0029] Illumination conditions include, for example, (1) the spatial distribution of luminescence intensity and / or luminescence color within the lighting device, or (2) the luminescence position determined by the position of the lighting device in a movable lighting device. Conditions combining (1) and (2) are also acceptable.

[0030] The processing unit 100 outputs a lighting command value to the lighting device LS and causes the lighting device LS to emit light in a light emission pattern corresponding to the lighting command value.

[0031] The processing unit 100 instructs the camera 102 to perform imaging and inputs the captured images. The timing for instructing the camera to perform imaging may be the timing when a sensor (not shown) detects that the workpiece 4 has arrived at a position suitable for imaging. Alternatively, the processing unit 100 may sequentially input images captured by the camera 102 at regular time intervals without instructing the camera to perform imaging, and the processing unit 100 may select the image to be used from the input images.

[0032] The processing unit 100 may be connected to a display 104 as an output unit for displaying the processing status, measurement results, etc., and to input units such as a keyboard 106 and a mouse 108 for accepting user operations. The processing unit 100 is connected to a network 8 and can communicate with other devices via the network 8.

[0033] (1. Hardware Configuration) Next, an example of the hardware configuration of the processing unit 100 included in the position measurement system 1 according to one embodiment of the present disclosure will be described using Figure 5. Figure 5 is a schematic diagram showing the hardware configuration of the processing unit 100.

[0034] The processing unit 100 may, for example, be implemented using a general-purpose computer configured according to a general-purpose computer architecture. The processing unit 100 includes a processor 110, main memory 112, camera interface 114, input interface 116, display interface 118, communication interface 120, and storage 130. These components are typically connected to each other in a communicative manner via an internal bus 122.

[0035] The processor 110 performs the functions and processes described later by loading various programs stored in the storage 130 into the main memory 112 and executing them. The main memory 112 is composed of volatile memory and functions as work memory necessary for program execution by the processor 110.

[0036] The camera interface 114 is connected to the camera 102 and acquires the image 138 captured by the camera 102. The camera interface 114 may also instruct the camera 102 on the timing of image capture, etc.

[0037] The input interface 116 is connected to input devices such as the keyboard 106 and mouse 108, and receives commands indicating user operations on these input devices.

[0038] The display interface 118 outputs various processing results generated by the execution of a program by the processor 110 to the display 104.

[0039] The communication interface 120 is responsible for processing communication with other devices via the network 8.

[0040] Storage 130 stores programs that enable the computer to function as a processing unit 100, such as the OS (Operating System) and measurement programs 132. Storage 130 may also store lighting parameters 134 and multiple images 138. The lighting parameters 134 are parameters that represent lighting conditions. Lighting command values ​​are generated based on the lighting parameters 134.

[0041] The measurement program 132 stored in the storage 130 may be installed on the processing unit 100 via an optical recording medium such as a DVD (Digital Versatile Disc) or a semiconductor recording medium such as a USB (Universal Serial Bus) memory. Alternatively, the measurement program 132 may be downloaded from a server device on a network.

[0042] When implemented using a general-purpose computer in this manner, some of the functions according to this embodiment may be realized by calling and processing the necessary software modules from among the software modules provided by the OS in a predetermined order and / or timing. In other words, the measurement program 132 according to this embodiment does not include all the software modules necessary to realize the functions according to this embodiment, and the necessary functions may be provided in cooperation with the OS.

[0043] Furthermore, the measurement program 132 may be provided as part of another program. In that case, the measurement program 132 itself does not contain any modules included in the other program that it is combined with, and it performs processing in cooperation with the other program. Thus, the measurement program 132 according to this embodiment may be in a form that is incorporated into another program.

[0044] Figure 5 shows an example of implementing the processing unit 100 using a general-purpose computer, but it is not limited to this, and all or part of its functions may be implemented using dedicated circuits (for example, ASICs (Application Specific Integrated Circuits) or FPGAs (Field-Programmable Gate Arrays)). Furthermore, some of the processing may be handled by external devices connected to a network.

[0045] (2. Functional Configuration) Next, an example of the functional configuration of the position measurement system 1 according to the embodiment of this disclosure will be described using Figure 6. Figure 6 is a schematic diagram showing an example of the functional configuration of the position measurement system 1 according to the embodiment of this disclosure. The processing unit 100 of the position measurement system 1 may include an image processing unit 141, an illumination condition identification unit 142, a measurement control unit 143, a storage unit 144, a determination unit 145, and a virtual image generation unit 146.

[0046] The image processing unit 141, illumination condition identification unit 142, measurement control unit 143, determination unit 145, and virtual image generation unit 146 in the processing unit 100 are realized by the processor 110 executing the measurement program 132. The processor 110 is a general-purpose processor. All or part of the functions of the processor 110 may be realized using dedicated circuits (for example, ASIC (Application Specific Integrated Circuit) or FPGA (Field-Programmable Gate Array)). Furthermore, some processing may be handled by external devices connected to a network.

[0047] The image processing unit 141 uses the image of the workpiece 4 to determine the relative position of the three-dimensional morphological elements provided on the workpiece 4 with respect to the workpiece 4.

[0048] The lighting condition identification unit 142 identifies suitable lighting conditions for the lighting device LS that minimize the relative position fluctuations determined by the image processing unit 141, which occur due to fluctuations in the positional relationship between the camera 102 and the workpiece 4 when capturing an image of the workpiece 4.

[0049] The measurement control unit 143 causes the camera 102 to image the workpiece 4 under suitable lighting conditions, and uses the image of the workpiece 4 to cause the image processing unit 141 to determine the relative position of the three-dimensional morphological elements provided on the workpiece 4 with respect to the workpiece.

[0050] The storage unit 144 stores images processed by the image processing unit 141. The storage unit 144 also stores illumination parameters representing the preferred illumination conditions identified by the illumination condition identification unit 142. The storage unit 144 is implemented by the aforementioned storage 130, which stores programs or data necessary for the operation of the position measurement system 1. Note that the processing unit 100 does not necessarily include the storage unit 144; instead, external (device) storage may be used.

[0051] The determination unit 145 determines the amount of deviation of the relative position obtained by the image processing unit 141 from the reference position, and determines whether the relative position is good or bad based on the amount of deviation. If the position measurement system 1 determines the relative position but does not perform a determination of whether the relative position is good or bad, it does not need to include the determination unit 145.

[0052] The virtual image generation unit 146 generates a virtual image of the workpiece that would have been obtained if it had been photographed under different lighting conditions than those used for actual photography, based on images of the workpiece taken under multiple lighting conditions. The virtual image can be used to optimize the lighting conditions. If the position measurement system 1 optimizes the lighting conditions based only on the actual images of the workpiece, it does not need to include the virtual image generation unit 146.

[0053] The position measurement system 1 can also be used as a lighting condition optimization system to identify optimal lighting conditions. In this case, it does not need to include the measurement control unit 143.

[0054] The position measurement system 1 can also be used as a position measurement system that measures under optimal lighting conditions acquired from an external source, with some modifications to its configuration. In this case, instead of the lighting condition identification unit 142, it is equipped with a lighting condition identification unit that acquires pre-specified optimal lighting conditions for the lighting device LS that reduce the fluctuation in the relative position determined by the image processing unit 141, which is caused by fluctuations in the positional relationship between the camera 102 and the workpiece 4 when capturing an image of the workpiece.

[0055] (3. Example of operation) In the following explanation of the operation examples, the meaning of each symbol used in the mathematical formulas is as shown in Tables 1-3. Bold lowercase letters indicate vectors, and bold uppercase letters indicate matrices (they are shown in non-bold form in the text). All other symbols are scalars. Also, ||| represents the L2 norm for a vector.

[0056] [Table 1]

[0057] [Table 2]

[0058] [Table 3]

[0059] (Lighting condition identification stage and measurement stage) Figure 7 shows the operation stages of the position measurement system 1. As shown in Figure 7, the operation of the position measurement system 1 is divided into a lighting condition identification stage and a measurement stage. During the lighting condition determination stage, the position measurement system 1 operates as follows: The image processing unit 141 determines the relative position of the three-dimensional morphological elements provided on the workpiece 4 with respect to the workpiece 4 for each image of the workpiece 4 captured under multiple lighting conditions.

[0060] The lighting condition identification unit 142 identifies suitable lighting conditions for the lighting device LS that minimize the relative position fluctuations determined by the image processing unit 141, which occur due to fluctuations in the positional relationship between the camera 102 and the workpiece 4 when capturing an image of the workpiece 4.

[0061] The setting of lighting conditions for the lighting device LS and the control of imaging for the camera 102 during the lighting condition specification stage may be performed manually or by automatic operation programmed into the processing unit 100.

[0062] During the measurement phase, the position measurement system 1 operates as follows: The measurement control unit 143 causes the camera 102 to image the workpiece 4 under suitable lighting conditions, and uses the image of the workpiece 4 to cause the image processing unit 141 to determine the relative position of the three-dimensional morphological elements provided on the workpiece 4 with respect to the workpiece.

[0063] When determining whether the relative position is good or bad, the determination unit 145 calculates the amount of deviation of the relative position obtained by the image processing unit from the reference position, and determines whether the relative position is good or bad based on the amount of deviation. Here, the reference position may be a design reference position, or it may be a statistical value (e.g., the average value) of multiple measured relative positions.

[0064] (Factors causing fluctuations in positional measurements) Figure 8 shows a circuit board with components mounted on it. The components are examples of three-dimensional morphological elements, and the circuit board is an example of workpiece 4. The circuit board has circuit board position reference marks A, B, and C printed on it. Circuit board position reference mark A is the origin r of the circuit board coordinate system. m (0) This shows that the direction connecting board position reference mark A and board position reference mark B is the X direction in the board coordinate system. The direction connecting board position reference mark A and board position reference mark C is the Y direction in the board coordinate system. On the captured image, the intersection point between the left edge of the component and the search line set by the position measurement system 1 is the measurement position r m (1) It is said that...

[0065] Figure 9 illustrates the variation in the shadowed area of ​​a component. Figure 9 shows the component portion shown in Figure 8, viewed from the Y direction of the substrate. Due to variations in the substrate transport position at the time of imaging, the position of the component during the first imaging is the position of the component shown as the component at the first transport position, and the position of the component during the second imaging is the position of the component shown as the component at the second transport position. Due to variations in transport position, the direction of the light rays hitting the rounded corner on the left side of the component changes as shown. Consequently, the boundary position between the illuminated area and the shadowed area also changes. This boundary position of the shadowed area is recognized as the edge representing the left side of the component in the image. Therefore, the measured value of the edge position fluctuates due to variations in transport position. It is expected that this fluctuation in the measured value will be mitigated if light is irradiated from the upper left direction in Figure 9 onto the left side of the component being measured, so that no shadow is cast on the part being measured. Fluctuations in the measured edge position, caused by variations in the positional relationship between the lighting device LS and camera 102 and the substrate, occur not only due to variations in the substrate's position in the transport direction, but also due to changes in the inclination of the substrate's surface. Furthermore, the extent to which the measured value fluctuates depends on the component's condition, including its shape, whether it is light-transmitting, whether its surface is specularly reflective, and the relationship between the component's color and the color of the illumination light.

[0066] (marker) In the following, the morphological elements of a three-dimensional object whose position we want to measure on an image will be referred to as markers, and the position of the measurement target point corresponding to the morphological element of the three-dimensional object will be referred to as the marker position.

[0067] There are two types of markers: one-dimensional markers and two-dimensional markers. One-dimensional markers are edges. An edge is a linearly distributed area in an image where the attributes of a pixel, such as its density or color, change abruptly compared to its surroundings. A search line is used to pinpoint the location of a one-dimensional marker. The location of a one-dimensional marker is the position of an edge on a search line that intersects with that edge.

[0068] A 2D marker is a geometric shape. The position of a 2D marker is the position of a specific feature point of that shape. Feature points of a shape include, for example, the centroid of a closed curve, the center of a circle or arc, the intersection of two lines, the corner of a polyline, and the endpoint of a line segment. The position of a 2D marker is measured for a selected type of feature point.

[0069] In the following explanation, for the sake of consistency with the mathematical formulas, terms such as "optimization" of lighting conditions and "minimization" of the variance of measured values ​​will be used. However, in reality, it is sufficient if the lighting conditions are determined within a suitable range that does not cause practical problems, even if they are not optimal, or if the variance of measured values ​​is reduced. Achieving "optimization," which means only the single best point, is not the intent of the invention.

[0070] This section describes a general procedure for measuring the position of a marker by referring to an image g, which is either captured or created as a virtual image. Consider a scenario where the coordinates r of the marker are determined from image g. In this position measurement problem, it is assumed that the positional relationship between the workpiece and the camera varies with each transport; therefore, measurements must be taken in the workpiece coordinate system, not the camera coordinate system. For example, the workpiece position in the camera coordinate system.

number

number

number

[0071] The marker position is determined by using the entirety or a part of image g as the search region E, and maximizing a predetermined marker likelihood function L within the search region E (or, in a predetermined coordinate search order, the position where the likelihood first exceeds the threshold).

number

[0072] Here, θ is a parameter vector for marker detection. The parameter vector may include values ​​used in the algorithm for calculating the likelihood function L, as well as values ​​that specify the algorithm for calculating the likelihood function L itself. For example, it may include a parameter that specifies an algorithm that sets a threshold for image density on the search line and defines either the position where the image density exceeds the threshold from below to above as an edge position, or the position where the threshold exceeds it from above to below as an edge position.

[0073] The problem setting for position measurement is to ensure that when measuring the same workpiece, the measured relative position of the three-dimensional morphological elements does not vary even if there is variation in the position of the workpiece relative to the camera (transport variation). M workpiece images g are captured under conditions of transport variation for the same workpiece. m For (1≦m≦M), the lighting conditions are determined such that the variance J of the measured values ​​at the positions defined below is minimized. At the same time, the marker detection parameter θ may also be determined, or the marker detection parameter θ may be a fixed value.

number

[0074] (Variations in the problem setting for measurement) The variance J of the measured values ​​may be one of those shown in Table 4. [Table 4] Table 4 shows position and orientation separately, but in general, in this specification, the position of a marker (a three-dimensional morphological element) includes the orientation of the marker, and the position of a workpiece includes the orientation of the workpiece.

[0075] (Optimization of lighting conditions) Let's consider a problem setting where we select the most suitable lighting condition from among several candidate lighting conditions. The candidate lighting conditions are given, for example, as follows: • If the lighting system is a multi-channel lighting system, only Z patterns of light emission levels are available for each lighting channel, and the pattern suitable for measurement is selected from among them. • If the lighting device is a movable light (i.e., the position or orientation of the lighting device can be controlled), and there are z possible positions or orientations for the lighting device, the position or orientation suitable for measurement is selected from among them.

[0076] In this embodiment, under each selectable lighting condition, multiple images are taken with the workpiece in a different position relative to the camera to simulate transport variations, and the lighting condition that minimizes the variation in the position measurement results obtained from each resulting image is selected.

[0077] Specifically, in the actual inspection environment, the same workpiece is transported under one lighting condition while M images are captured, and this process is repeated for each of the Z lighting conditions. One of the ZM images captured in this way is then selected as g z,m This is how it is written.

[0078] The optimal lighting conditions to seek z opt This is determined as follows, minimizing the variation J in the measurement position.

number

[0079] Optimal marker detection parameter θ optIt may also be required simultaneously. The optimization problem of illumination conditions and marker detection parameters can be expressed as follows.

Number

[0080] In the illumination condition identification stage, the user may be allowed to specify in advance the area containing the marker. By doing so, the possibility of mistakenly measuring unintended image features as measurement targets is reduced. Hereafter, this area will be referred to as the search area E (p) and is called.

[0081] For a 1D marker, the search line of the edge can be regarded as the search area E (p) Alternatively, the search area E (p) can be set to include the measurement target position on the edge, and the search line of the edge can be automatically set within the search area E (p) The search area E (p) for a 2D marker is set to include the figure that is the 2D marker.

[0082] (Example 1) Obtaining the position on the 1D coordinate axis from 1D edge information FIG. 10 is a diagram for explaining the position measurement of a 1D marker. Hereinafter, an example of specifically defining the marker likelihood function will be described. As the simplest example, consider the problem of finding the position of a marker on a search line defined on an image. This corresponds to the case where the marker search region is a line segment. The marker must have a structure that has a spatial frequency (a gradient that is not zero) in the direction of the search line. For example, this corresponds to a sudden change in brightness or color. If the profile function of the image on the search line is φ(t), then given this, the marker position can be determined. The profile function is an aggregate of surrounding image information as values ​​on the search line. For example, for each point on the search line, the average value or median value for noise reduction is taken from the set of pixel values ​​passing through that point and perpendicular to the search line. Post-processing such as differentiation or frequency filtering may be applied as needed.

[0083] In this case, the marker likelihood function can be categorized into variations shown in the table below. Here, the position r in the marker likelihood function corresponds one-to-one with the position t on the profile. [Table 5]

[0084] (Example 2) Determining the position on the 2D coordinate axis from a 2D marker Figure 11 illustrates the measurement of the position of a 2D marker. Examples of 2D markers include any given shape (e.g., a circle or rectangle). The shape may be a subimage identified by some local feature. However, spatial frequencies must exist in the direction of the dimension of all coordinates to be measured; that is, the Hessian matrix must not be degenerate. Position r is a representative position of the shape determined by some method, and is expressed, for example, in xy coordinates. Figure 11 shows the case where the shape is a square and the representative position is the center of the square. Examples of marker likelihood functions in this case include the variations shown in the table below.

[0085] [Table 6] Any previously proposed local feature vectors such as SIFT, SURF, HoG, and Haar-Like can be used as features to identify marker coordinates. Search region E (p) The process of determining marker coordinates is similar to keypoint search in feature analysis methods such as SIFT, SURF, and HoG.

[0086] (Example 3) Determining the position on the 2D coordinate axis from multiple 1D edge information Figure 12 illustrates the measurement of a position determined from multiple one-dimensional markers. In the case of (Example 1), the marker coordinates were determined on a predetermined search line on the image. However, as shown in Figure 12(A), if the directions of two non-parallel linear edges are determined, it is possible to identify the coordinates of the intersection point of the edges. In practice, it is common to integrate information from many one-dimensional marker coordinates to ensure robustness against noise.

[0087] For example, in applications where the location of a round hole or a square component on a circuit board is to be determined, search lines are placed at fine intervals perpendicular to the edge direction on the circumference of a circle (as shown in Figure 12(B)) or on the sides of a rectangle (as shown in Figure 12(C)). Edge coordinates (=1D marker coordinates) are detected on each search line, and outlier removal and least-squares fitting are performed on this edge position information to determine the position of the object to be measured. When using such a method, it is best to specify the search area as the shape of the interval between double lines that enclose the contour of the shape to be detected, and to set search lines, which are line segments with each of the double lines as their endpoint, between the double lines.

[0088] (Example 4) Optimization when individual variations are included In addition to variations in workpiece transport, individual variations may also be considered to optimize the lighting conditions. Here, it is assumed that the value considered to be the true value of individual variations (hereinafter simply referred to as "true value") can be measured by another measurement means. A set of M workpiece samples is compared with a set of Q samples of transport variations for each individual workpiece. qDivided into sections, the true value of the measurement for each individual workpiece

number

number

[0089] As described above, the optimization process is performed to bring the values ​​as close as possible to the true values, even when individual variations in the workpieces are included.

[0090] (Example 5) Optimization when the true value of individual variation is unknown When measurement variability is defined as the variance across all work samples, including both individual and transport variability of the workpieces, if the true value of the dimension to be measured also includes individual variability, then the criteria for minimizing the overall variability would result in lighting conditions and inspection parameters that would actually obscure the individual variability of the true value of the dimension. To avoid this, we have a set of M work samples, and a set of Q samples C representing the transport variability for each individual work. q Alternatively, the work can be divided into sections, the variance can be evaluated individually for each work, and finally, the sum of the individually calculated variances for all work can be defined as the variance to be minimized. In this case, the evaluation criterion J to be minimized is defined as follows.

number

[0091] As described above, even when the measured true value varies due to individual variations in the workpiece, only the transport variation can be minimized.

[0092] (Example 6) Test to measure multiple markers simultaneously Up to this point, we have dealt with problem settings where it is necessary to determine the position of a single marker in order to obtain a measurement. However, in general, there are cases where it is necessary to measure the positions of multiple markers in order to obtain a single measurement. For example, when the measurement quantity is defined as the distance between markers.

[0093] A specific example of measuring the distance between two markers whose position measurement is affected by lighting conditions is when measuring the relative position of an LED element mounted on a substrate, which is a workpiece, and the feature used as a reference for the position of the substrate is a three-dimensional object (marker) that is affected by lighting conditions, such as a hole with a rounded cross-sectional shape at its edge. Another specific example is when two LED elements are mounted on a substrate, and it is more important to stably measure the distance between the two LED elements than the relative position of each LED element with respect to the substrate. This situation arises when two LED elements are inserted into two holes provided at a predetermined distance apart in another component. In this case, the invention can be applied by considering the position of one LED element as the reference for the position of the substrate, which is the workpiece, and the position of the other LED element as the position of the three-dimensional morphological element. Alternatively, one of the LED elements itself may be considered as the workpiece. In this case, the other LED element, which is the three-dimensional morphological element, is considered to be indirectly provided on the first LED element, which is the workpiece, via the substrate.

[0094] Furthermore, when measuring the positions of multiple markers, the illumination conditions may be optimized for each marker, and when imaging a specific marker, it may be illuminated with the illumination conditions optimized for that marker.

[0095] From the image g, which was captured or created as a virtual image, the coordinates r of P markers (p) Let's consider the situation for identifying the markers. Assume that the work coordinate system is set in image g. For each marker, a predetermined search area E (p)Therefore, each marker coordinate is determined by maximizing a predetermined marker likelihood function L (or by being the first to exceed the threshold likelihood in the default coordinate search order).

number

[0096] Here, θ (p) is a parameter for detecting the p-th marker. M workpiece images g are captured under conditions of workpiece transport variation. m For (1 ≤ m ≤ M), the lighting conditions are determined such that the variance J of the measured values, as defined in Table 7, is minimized. At the same time, the marker detection parameters may also be determined, or the marker detection parameters may be fixed values.

[0097] [Table 7] As an example, let's consider the problem of measuring the distance between markers. Since measuring distance requires at least two markers, we will proceed assuming P=2 below. Using the marker position coordinates obtained in the same way as in position measurement, the measurement quantity of the dimension is |r (2) -r (1) This is obtained as |. If the object whose dimensions you want to measure (for example, points A and B) does not fit within the camera's field of view, an alignment mark is introduced, and in the first image, point A (p=1) and the alignment mark (position r (3) To ensure that point B (p=2) and the alignment mark (position r) are visible in the second image, take the second image. (4) Make sure that ) is visible. If there is no rotational misalignment, the measurement amount of the dimension is |(r (2) -r (4) )-(r (1) -r (3) )| is obtained as.

[0098] M workpiece images g acquired under conditions of varying workpiece transport. mFor (1 ≤ m ≤ M), the lighting conditions are determined such that the variance J of the measured values ​​of the dimensions defined below is minimized. At the same time, the marker detection parameter θ may also be determined, or the marker detection parameter θ may be a fixed value.

number

[0099] (Example 7) Determination of optimal lighting conditions for position inspection by lighting simulation This section describes a method for optimizing lighting conditions when the number of lighting conditions is too large to cover and capture images of all conditions in advance. The optimization process is automated by utilizing the fact that images captured under varying lighting conditions can be accurately estimated through lighting simulations.

[0100] We assume that the sensor linearity (linearity between brightness and pixel value) is established in the imaging system. This means that linearity is established in the system including all signal processing such as demosaicing of color filters, gamma correction, and imaging corrections such as dark current offset correction. To avoid nonlinearity due to pixel saturation, HDR (High Dynamic Range) synthesis may be used for image acquisition. In this case, we consider a situation in which a workpiece illuminated by K multi-channel illumination is imaged, and the emission intensity of each illumination is represented as the following vector.

[0101] u=(u1,u2,…,u k ) T , u k ≥0

[0102] At this time, u i =1,u j f = 0 (j≠i) is a column vector created by illuminating only the i-th light source at a predetermined intensity and turning off the others, and arranging the captured images in this way. i Therefore, the captured image g under any lighting condition u can be modeled by image superposition as follows.

number

[0103] Here, f' is a multi-channel image (a large single column vector) formed by arranging K images vertically as defined below.

number

number

number

[0104] Thus, optimizing multi-channel illumination involves generating a feature vector g from the original image f' using an inner product operation, i.e., a projection matrix.

number

[0105] In the following, we consider a scenario where K lights are installed, and the optimal illumination is determined by varying the illumination emission pattern for a single workpiece and taking N patterns of images.

[0106] The emission pattern in the nth (1≦n≦N) image is defined as follows. A specific example of this emission pattern is shown in Figure 13.

[0107]

number

[0108] By imaging the workpiece with these light emission patterns, it becomes possible to reconstruct the captured image of the workpiece when illuminated with an arbitrary light emission pattern. In order to obtain all the degrees of freedom of this system matrix, it is desirable to determine the light emission patterns so that rankH = min(N, K), that is, they are linearly independent. In order to utilize all K degrees of freedom of illumination without leaving any, at least N = K, and at that time H must be full rank.

[0109] On the other hand, if N < K, the degrees of freedom of the number of illuminations cannot be fully utilized, but it is an effective method for shortening the imaging time of the workpiece. Various methods can be considered as methods for realizing this, and a typical method is a method of performing LT (Light Transport) matrix estimation using Compressed Sensing.

[0110] Also, the case of N > K can be considered. This is unnecessary in terms of fully utilizing the degrees of freedom of illumination and results in a wasteful number of imaging shots, but it can be selected for other purposes such as improving the SN ratio or dynamic range.

[0111] Let f be the arrangement of the images captured with these light emission patterns as column vectors i Then, a multi-CH image vector obtained by arranging these vertically for another N images is defined as follows.

Equation

[0112] In the above equation [[ID=u]]

Equation

Equation

Equation

[0113] Here, inequalities for vectors and matrices are assumed to be inequalities over all elements. When H=I, that is, when K (=N) images are taken with each light source turned on one by one, u and w are equivalent. Below, we deal with the problem of finding the optimal illumination u by finding the optimal image superposition weight w.

[0114] By using lighting simulations, it becomes possible to record the actual variations in workpiece transport as images in advance, and then optimize the lighting conditions for those samples to minimize the variation in measurement results through a computer-based process.

[0115] To obtain images captured under conditions of varying workpiece transport, a base image set consisting of M images for illumination simulation is obtained by capturing images of the same workpiece while transporting it under a single illumination condition in the actual inspection environment. Hereafter, the M base image set will be referred to as f' using the notation described above. m This is denoted as (1≦m≦M).

[0116] When the image overlay weight according to the lighting conditions is w, the captured image g m (1≦m≦M) Lighting simulation

number

number

[0117] If we also optimize the P marker detection parameters simultaneously, this can be expressed as follows:

number

[0118] While camera exposure and gain are adjustable parameters, the settings for exposure and gain do not affect the deviation in the measurement results of the relative position of the three-dimensional morphological elements relative to the workpiece, in accordance with the workpiece's position (transport variation). Exposure and gain are determined during the illumination condition specification stage and the measurement stage to ensure that the captured image is neither too bright nor too dark.

[0119] Although embodiments of the present invention have been described in detail above, the above description is merely illustrative in all respects of the present invention. Needless to say, various improvements and modifications can be made without departing from the scope of the present invention. Furthermore, some or all of the above embodiments may also be described as follows, but are not limited thereto. (Note 1) A position measurement system (1) that measures the relative position of a morphological element with respect to the workpiece (4) and the morphological elements provided on the workpiece (4), An imaging device (102) for imaging the workpiece (4), The imaging device (102) is used as a light source for imaging, and the illumination device (LS) can change the illumination conditions for the workpiece (4), An image processing unit (141) that determines the relative position using the image of the workpiece (4), A lighting condition identification unit (142) identifies suitable lighting conditions for the lighting device (LS) such that the fluctuation in the relative position determined by the image processing unit (141), which occurs due to fluctuations in the positional relationship between the imaging device (102) and the workpiece (4) when an image of the workpiece (4) is captured, is reduced. Under the aforementioned preferred illumination conditions, the imaging device (102) is instructed to image the workpiece (4), and the measurement control unit (143) is instructed to use the image processing unit (141) to determine the relative position using the image of the workpiece (4) captured. A position measurement system (1) equipped with the following:

[0120] (Note 2) The aforementioned morphological element is a one-dimensional morphological element, The image processing unit (141) determines the relative position by taking the intersection point of the search line and the one-dimensional morphological element as the position of the morphological element. The position measurement system (1) described in Appendix 1.

[0121] (Note 3) The aforementioned morphological element is a two-dimensional morphological element, The image processing unit (141) determines the relative position by using the representative position of the two-dimensional morphological element identified within the search area as the position of the morphological element. The position measurement system (1) described in Appendix 1.

[0122] (Note 4) The aforementioned morphological elements are a plurality of one-dimensional morphological elements, The image processing unit (141) determines the position of the intersection point between one of the plurality of search lines and one of the plurality of one-dimensional morphological elements for multiple pairs of the one search line and the one morphological element, and uses the representative position determined based on the positions of the multiple intersection points to determine the relative position of the plurality of one-dimensional morphological elements. The position measurement system (1) described in Appendix 1.

[0123] (Note 5) The preferred lighting conditions identified by the lighting condition identification unit (142) are lighting conditions in which, when the image used to identify the preferred lighting conditions is an image of a plurality of workpieces (4), and the positional relationship between the imaging device (102) and the workpiece (4) is different for each workpiece (4), and when a value considered to be the true value of the relative position is available for each workpiece (4), the sum of the variations in the relative position from the value considered to be the true value for each workpiece (4) for the plurality of workpieces (4) is small. The position measurement system (1) described in Appendix 1.

[0124] (Note 6) The preferred lighting conditions identified by the lighting condition identification unit (142) are lighting conditions that, when the image used to identify the preferred lighting conditions is an image of a plurality of workpieces (4), and when the positional relationship between the imaging device (102) and the workpiece (4) for one workpiece (4) is different for each of the plurality of images, the sum of the relative positional variations for each workpiece (4) across the plurality of workpieces is small. The position measurement system (1) described in Appendix 1.

[0125] (Note 7) The lighting condition specification unit (142) specifies the preferred lighting conditions for each of the three-dimensional morphological elements when the workpiece (4) is provided with a plurality of three-dimensional morphological elements. The image processing unit (141) determines the relative position for each of the plurality of three-dimensional morphological elements provided on the workpiece (4) using an image of the workpiece (4) captured under the preferred illumination conditions corresponding to the three-dimensional morphological element to be processed. The position measurement system (1) described in Appendix 1.

[0126] (Note 8) Furthermore, the system includes a virtual image generation unit (146) that generates a virtual image of the workpiece (4) that would be obtained if it were imaged under different lighting conditions than those used for imaging, based on images of the workpiece (4) taken under multiple lighting conditions. The image processing unit (141) also determines the relative position when the image of the workpiece (4) is a virtual image. The illumination condition specification unit (142) specifies the preferred illumination conditions such that the variation in the relative position obtained for the virtual image, or for the image of the captured workpiece and the virtual image, becomes small. A position measurement system (1) as described in any one of the items 1 to 7 of the appendix.

[0127] (Note 9) Furthermore, the position measurement system (1) described in Appendix 8 includes a determination unit (145) that determines the amount of deviation of the relative position obtained by the image processing unit (141) from a reference position, and determines whether the relative position is good or bad based on the amount of deviation.

[0128] (Note 10) Furthermore, the position measurement system (1) according to any one of the appendices 1 to 7, comprising a determination unit (145) that determines the amount of deviation of the relative position obtained by the image processing unit (141) from a reference position, and determines whether the relative position is good or bad based on the amount of deviation.

[0129] (Note 11) A lighting condition optimization system (1) for optimizing the lighting conditions for imaging to measure the relative position of a morphological element with respect to the workpiece (4) and a three-dimensional morphological element provided on the workpiece (4), An imaging device (102) for imaging the workpiece (4), The imaging device (102) is used as a light source for imaging, and the illumination device (LS) can change the illumination conditions for the workpiece (4), An image processing unit (141) that determines the relative position using the image of the workpiece (4), A lighting condition identification unit (142) identifies suitable lighting conditions for the lighting device (LS) such that the fluctuation in the relative position determined by the image processing unit (141), which occurs due to fluctuations in the positional relationship between the imaging device (102) and the workpiece (4) when an image of the workpiece (4) is captured, is reduced. A lighting condition optimization system (1) equipped with the following.

[0130] (Note 12) A position measurement system (1) that measures the relative position of a morphological element with respect to the workpiece (4) and the morphological elements provided on the workpiece (4), An imaging device (102) for imaging the workpiece (4), The imaging device (102) is used as a light source for imaging, and the illumination device (LS) can change the illumination conditions for the workpiece (4), An image processing unit (141) that determines the relative position using the image of the workpiece (4), A lighting condition identification unit (142) acquires predetermined preferred lighting conditions for the lighting device (LS) such that the fluctuation in the relative position determined by the image processing unit (141), which occurs due to fluctuations in the positional relationship between the imaging device (102) and the workpiece (4) when an image of the workpiece (4) is captured, is reduced. Under the aforementioned preferred illumination conditions, the imaging device (102) is instructed to image the workpiece (4), and the measurement control unit (143) is instructed to use the image processing unit (141) to determine the relative position using the image of the workpiece (4) captured. A position measurement system equipped with the following features. [Explanation of symbols]

[0131] 1…Position measurement system, 2…Belt conveyor, 4…Workpiece, 6…Imaging field of view, 8…Higher-level network, 10…PLC, 12…Database device, 100…Processing device, 102…Camera, 104…Display, 106…Keyboard, 108…Mouse, 110…Processor, 112…Main memory, 114…Camera interface, 116…Input interface, 118…Display interface, 120…Communication interface, 122…Internal bus, 130…Storage, 132…Measurement program, 134…Illumination parameters, 138…Image, 141…Image processing unit, 142…Illumination condition identification unit, 143…Measurement control unit, 144…Storage unit, 145…Determination unit, 146…Virtual image generation unit, LS…Illumination device, LSi…Channel illumination unit

Claims

1. A position measurement system for measuring the relative position of a morphological element with respect to a workpiece and a three-dimensional morphological element provided on the workpiece, An imaging device for imaging the aforementioned workpiece, The aforementioned imaging device is used as a light source for imaging, and is an illumination device capable of changing the illumination conditions for the workpiece, An image processing unit that determines the relative position using the image of the workpiece, A lighting condition identification unit identifies suitable lighting conditions for the lighting device such that the fluctuation in the relative position determined by the image processing unit, which occurs due to fluctuations in the positional relationship between the imaging device and the workpiece when an image of the workpiece is captured, becomes smaller. A measurement control unit which causes the imaging device to image the workpiece under the aforementioned preferred lighting conditions, and causes the image processing unit to determine the relative position using the image of the workpiece captured; A position measurement system equipped with the following features.

2. The aforementioned morphological element is a one-dimensional morphological element, The image processing unit determines the relative position by taking the intersection point of the search line and the one-dimensional morphological element as the position of the morphological element. The position measurement system according to claim 1.

3. The aforementioned morphological element is a two-dimensional morphological element, The image processing unit determines the relative position by using the representative position of the two-dimensional morphological element identified within the search area as the position of the morphological element. The position measurement system according to claim 1.

4. The aforementioned morphological elements are a plurality of one-dimensional morphological elements, The image processing unit determines the position of the intersection point between one of the plurality of search lines and one of the plurality of one-dimensional morphological elements for multiple pairs of the one search line and the one morphological element, and uses the representative position determined based on the positions of the multiple intersection points to determine the relative position of the plurality of one-dimensional morphological elements. The position measurement system according to claim 1.

5. The preferred lighting conditions identified by the lighting condition identification unit are lighting conditions in which, when the image used to identify the preferred lighting conditions is an image of a plurality of workpieces, and the image includes a plurality of images in which the positional relationship between the imaging device and the workpiece is different for each workpiece, and further, when a value considered to be the true value of the relative position is available for each of the workpieces, the sum of the variations in the relative position from the value considered to be the true value for each of the workpieces is small for the plurality of workpieces. The position measurement system according to claim 1.

6. The preferred lighting conditions identified by the lighting condition identification unit are lighting conditions that, when the image used to identify the preferred lighting conditions is an image of a plurality of workpieces, and when the positional relationship between the imaging device and the workpiece is different for one workpiece, the sum of the relative positional variations for each of the plurality of workpieces is small. The position measurement system according to claim 1.

7. The lighting condition specification unit, when the workpiece is provided with a plurality of three-dimensional morphological elements, specifies the preferred lighting conditions for each of the three-dimensional morphological elements. The image processing unit determines the relative position for each of the plurality of three-dimensional morphological elements provided on the workpiece, using an image of the workpiece captured under the preferred illumination conditions corresponding to the three-dimensional morphological element to be processed. The position measurement system according to claim 1.

8. Furthermore, the system includes a virtual image generation unit that generates a virtual image of the workpiece that would have been obtained if it had been imaged under different lighting conditions than those used for imaging, based on images of the workpiece taken under multiple lighting conditions. The image processing unit determines the relative position even when the image of the workpiece is a virtual image. The illumination condition identification unit identifies the preferred illumination conditions such that the variation in the relative position obtained for the virtual image, or for the image of the captured workpiece and the virtual image, becomes small. A position measurement system according to any one of claims 1 to 7.

9. Furthermore, the position measurement system according to claim 8, further comprising a determination unit that determines the amount of deviation of the relative position obtained by the image processing unit from a reference position, and determines whether the relative position is good or bad based on the amount of deviation.

10. Furthermore, the position measurement system according to any one of claims 1 to 7, further comprising a determination unit that determines the amount of deviation of the relative position obtained by the image processing unit from a reference position, and determines whether the relative position is good or bad based on the amount of deviation.

11. A lighting condition optimization system for optimizing the lighting conditions for imaging to measure the relative position of a morphological element with respect to a workpiece and a three-dimensional morphological element provided on the workpiece, An imaging device for imaging the aforementioned workpiece, The aforementioned imaging device is used as a light source for imaging, and is an illumination device capable of changing the illumination conditions for the workpiece, An image processing unit that determines the relative position using the image of the workpiece, A lighting condition identification unit that identifies suitable lighting conditions for the lighting device, which reduces the fluctuation in the relative position determined by the image processing unit, caused by fluctuations in the positional relationship between the imaging device and the workpiece when an image of the workpiece is captured. A lighting condition optimization system equipped with the following features.

12. A position measurement system for measuring the relative position of a morphological element with respect to a workpiece and a three-dimensional morphological element provided on the workpiece, An imaging device for imaging the aforementioned workpiece, The aforementioned imaging device is used as a light source for imaging, and is an illumination device capable of changing the illumination conditions for the workpiece, An image processing unit that determines the relative position using the image of the workpiece, A lighting condition determination unit that acquires predetermined preferred lighting conditions for the lighting device such that the fluctuation in the relative position determined by the image processing unit, which occurs due to fluctuations in the positional relationship between the imaging device and the workpiece when an image of the workpiece is captured, becomes smaller. A measurement control unit which causes the imaging device to image the workpiece under the aforementioned preferred lighting conditions, and causes the image processing unit to determine the relative position using the image of the workpiece captured; A position measurement system equipped with the following features.

Images