Measurement system and imaging unit

Abstract

This measurement system comprises: a light source unit that irradiates a subject with slit light; an imaging unit that, on the basis of a difference image showing the difference between when the light source unit is off and when the light source unit is on, detects the center position of the slit light in the short direction at each position in the longitudinal direction of the slit light projected onto the subject; and a processing unit that measures the subject on the basis of the center positions of the slit light detected by the imaging unit.

Description

Measurement system and imaging unit

[0001] The present disclosure relates to a measurement system and an imaging unit.

[0002] 2. Description of the Related Art There is known a technique for irradiating a subject with a slit of light and measuring the three-dimensional shape of the subject based on an image obtained when the slit of light is projected onto the subject.

[0003] JP 2002-366930 A JP 2012-021909 A JP 2012-122975 A

[0004] Improving measurement performance is an important issue, and there is still room for improvement in various areas, such as increasing precision, speed, and robustness.

[0005] One aspect of the present disclosure provides improved metrology performance.

[0006] A measurement system according to one aspect of the present disclosure includes a light source unit that irradiates a subject with slit light, an imaging unit that detects the center position of the slit light in the short direction at each position in the long direction of the slit light projected onto the subject based on a differential image that shows the difference between when the light source unit is off and when it is on, and a processing unit that measures the subject based on the center position of the slit light detected by the imaging unit.

[0007] An imaging unit according to one aspect of the present disclosure is an imaging unit used together with a light source unit that irradiates a subject with slit light, and includes a detection unit that detects the center position in the short direction of the slit light at each position in the long direction of the slit light projected onto the subject based on a differential image that shows the difference between when the light source unit is off and when it is on.

[0008] 1 is a diagram showing an example of a schematic configuration of a measurement system 1 according to an embodiment. FIG. 1 is a block diagram showing an example of a schematic configuration of the measurement system 1. FIG. 2 is a diagram showing an example of a difference image 330. FIG. 3 is a diagram showing an example of movement of the subject 9 between frames. FIG. 4 is a diagram showing an example of detection of the center position 20c of the slit beam 20. FIG. 5 is a diagram showing an example of detection of the center position 20c of the slit beam 20. FIG. 6 is a diagram showing an example of detection of the center position 20c of the slit beam 20. FIG. 7 is a diagram showing an example of detection of an outlier. FIG. 8 is a diagram showing an example of the measurement principle. FIG. 9 is a diagram showing an example of a distance image 420. FIG. 10 is a diagram showing an example of processing (measurement method) executed in the measurement system 1. FIG. 11 is a diagram showing a comparison between the presence and absence of a difference image. FIG. 12 is a diagram showing a comparison between the presence and absence of a mask. FIG. 13 is a flowchart showing an example of processing when a second method is used. FIG. 14 is a diagram showing an example of a schematic configuration of an image sensor 32 and a control unit 33. FIG. 15 is a diagram showing an example of a pixel circuit. FIG. 16 is a timing chart showing an example of the operation of the image sensor 32 and the control unit 33. FIG. 17 is a diagram showing a modified example.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following embodiments, the same elements are designated by the same reference numerals, and redundant description will be omitted.

[0010] The present disclosure will be described in the following order: 0. Introduction 1. Embodiment 2. Modification 3. Conclusion

[0011] 0. Introduction Three-dimensional shape measurement using light-section technology is desired to achieve high accuracy, speed, and robustness. For example, Patent Document 1 (Patent Document 1) realizes a high-speed measurement system by detecting the center of gravity of a slit beam and calculating distance within an image sensor (solid-state imaging device). However, this method detects the center of gravity of the slit beam using a binarization method, which does not guarantee high-precision measurement. Furthermore, the center of gravity of the slit beam does not necessarily coincide with the center position, leaving issues with robustness. When a non-target object, such as a non-target object, is brighter than the slit beam projected onto the target object in the same pixel column, erroneous detection of the center position of the slit beam may occur, further posing issues with robustness. The threshold required for binarization processing must also be manually set by the user for each target object, placing a heavy burden on the user.

[0012] In Patent Document 2, a high level of robustness is achieved by calculating the feature values ​​of the subject and determining whether the subject is good or bad. However, with this method, the amount of data output from the image sensor is large, and the measurement processing speed is limited by the IF (interface) with the downstream processing unit. In addition, data communication between the frame memory and the signal processing unit in the downstream unit occurs multiple times, making it difficult to ensure high-speed measurement.

[0013] In Patent Document 3, the difference between an image when light is projected onto the subject and an image when light is not projected is calculated, and background light is removed to improve the robustness of the measurement. However, the method in Patent Document 3 involves calculating autocorrelation in blocks consisting of multiple pixels when creating table data, which means that the correlation results are affected by sensor noise, making it difficult to ensure high-precision measurement, which is a problem similar to that of Patent Document 2.

[0014] With conventional technologies, it is difficult to achieve high accuracy, high speed, and high robustness. At least some of these challenges are addressed by the disclosed technology. As will be described in detail later, the center position of the slit light projected onto the subject is detected based on a difference image showing the difference between when the light source unit is off and when it is on. High-accuracy detection is possible because the effects of ambient light are eliminated, etc. In one embodiment, the generation of the difference image is accelerated by effectively utilizing the charge storage unit within the pixel, AZ adjustment in AD conversion, etc. No frame memory is required (frame memory-less).

[0015] In one embodiment, the center position of the slit beam is calculated based on the max pixel with the greatest amount of incident light in the pixel row (column) corresponding to the width of the slit beam, its neighboring pixels, and the positions (e.g., addresses) of those pixels. Since there is no need to reduce the amount of information as in the binarization method, the accuracy of detecting the center position of the slit beam is improved.

[0016] Due to factors such as the angle of the emission line and occlusion, an outlier may occur at the center position of the detected slit light. To reduce false detections, a mask for removing outliers may also be generated simultaneously. This can contribute to improving the accuracy of distance calculations required for shape measurement. Distance calculations may be performed in a processing unit downstream of the imaging unit, or may be performed within the imaging unit. This may be selectable by mode selection, etc. If processing is performed within the imaging unit, the amount of data output from the imaging unit to the downstream processing unit can be reduced, thereby increasing the possibility of addressing the speed limitations of the IF section. This reduces the burden on the downstream processing unit, leading to an increase in the speed of the entire system. Furthermore, since there is no need to manually set the threshold, as described above, the burden on the user is also reduced.

[0017] 1. Embodiment Fig. 1 is a diagram showing an example of the schematic configuration of a measurement system 1 according to an embodiment. The measurement system 1 includes a light source unit 2, an imaging unit 3, a processing unit 4, and a transport unit 5. In Fig. 1A, the light source unit 2 is off, and in Fig. 1B, the light source unit 2 is on.

[0018] The object of measurement by the measurement system 1 is illustrated as an object 9. The measurement system 1 measures the three-dimensional shape of the object 9. An XYZ coordinate system is also illustrated. The X-axis direction and Y-axis direction (XY plane direction) correspond to the horizontal direction, and the Z-axis direction corresponds to the vertical direction.

[0019] The light source unit 2 outputs slit light 20 and irradiates it onto the subject 9 and the transport unit 5. The cross section of the slit light 20 has a linear (rectangular) shape. The longitudinal direction (length direction) and lateral direction (width direction) of the cross section are referred to as the longitudinal direction and lateral direction of the slit light 20. As shown in FIG. 1B , the X-axis direction corresponds to the longitudinal direction of the slit light 20, and the Y-axis direction corresponds to the lateral direction of the slit light 20.

[0020] When the light source unit 2 is off, as shown in Fig. 1A, the light source unit 2 does not output the slit light 20. When the light source unit 2 is on, as shown in Fig. 1B, the light source unit 2 outputs the slit light 20. The slit light 20 from the light source unit 2 is irradiated onto the subject 9 and the transport unit 5.

[0021] The imaging unit 3 detects light within the imaging range 30. When the subject 9 is located within the imaging range 30, the light from the subject 9 and the transport unit 5 is detected by the imaging unit 3, thereby allowing the subject 9 and the transport unit 5 to be imaged. When the light source unit 2 is off, the subject 9 and the transport unit 5 that are not illuminated by the slit light 20 from the light source unit 2 can be imaged. When the light source unit 2 is on, the light from the subject 9 and the transport unit 5 that are illuminated by the slit light 20 from the light source unit 2 is detected by the imaging unit 3, thereby allowing the subject 9 and the transport unit 5 to be imaged.

[0022] The processing unit 4 controls the light source unit 2 and the imaging unit 3, and processes data from the imaging unit 3. The processing unit 4 can also be called a unit provided after the light source unit 2 and the imaging unit 3 (a subsequent unit).

[0023] The transport unit 5 transports the subject 9. In this example, the subject 9 is placed on the transport unit 5 (on the surface on the positive side of the Z axis). The transport unit 5 moves in the negative direction of the Y axis, and the subject 9 also moves in the negative direction of the Y axis. As a result, the slit light 20 emitted from the light source unit 2 is irradiated onto the subject 9 in the positive direction of the Y axis. An example of the transport unit 5 is a belt conveyor.

[0024] Further details of the measurement system 1 will be described with reference to FIG.

[0025] 2 is a block diagram showing an example of a schematic configuration of the measurement system 1. The block configuration of the light source unit 2, the imaging unit 3, and the processing unit 4 described above is shown as an example.

[0026] The light source unit 2 includes a laser element 21, a control unit 22, and a register 23. An example of the laser element 21 is a semiconductor laser. By directly modulating the on / off state of the current of the semiconductor laser, it is possible to quickly switch the laser light output (the light source unit 2) on and off. The control unit 22 controls the laser element 21 according to the setting of the register 23. The register 23 can be set by the processing unit 4, and the light source unit 2 is controlled by the processing unit 4.

[0027] The imaging unit 3 includes an image sensor 31 and an IF section 39. The image sensor 31 is a solid-state imaging device such as a CMOS image sensor. The IF section 39 is an interface section for communicating with external devices of the imaging unit 3, and transmits data obtained by the image sensor 31 to the processing unit 4, for example.

[0028] The image sensor 31 includes an imaging element 32 , a control unit 33 , a register 34 , and a signal processing unit 35 .

[0029] The image sensor 32 includes a plurality of pixels arranged in a two-dimensional array. Each pixel includes a photoelectric conversion unit (e.g., a photodiode) that generates an electric charge according to the amount of incident light, and also includes circuit elements for generating and outputting a signal (voltage signal) according to the amount of incident light.

[0030] The control unit 33 controls the image pickup element 32 in accordance with the setting of the register 34. The register 34 can be set by the processing unit 4, and the image pickup unit 3 is controlled by the processing unit 4.

[0031] The control unit 33 also generates an image showing the difference between when the light source unit 2 is off and when the light source unit 2 is on. This image is referred to as a difference image 330. The description will also refer to FIG. 3.

[0032] FIG. 3 is a diagram showing an example of a difference image 330. In this example, the difference image 330 is described as an image showing the difference between an image 330a and an image 330b. The image 330a is an image that would be obtained when the light source unit 2 is off. The image 330b is an image that would be obtained when the light source unit 2 is on. The difference image 330 is an image based on a signal value (difference value) obtained by subtracting the signal of the image 330a from the signal of the image 330b. The image 330b can also be said to be an image that includes only the slit light 20 irradiated onto the transport unit 5 and the subject 9. Note that the images 330a and 330b do not necessarily have to be actually generated.

[0033] 2, in order to generate the difference image 330 as described above, the control unit 33 exposes the pixels of the image sensor 32 so as to obtain a signal for the image 330a, and also exposes the pixels of the image sensor 32 so as to obtain a signal for the image 330b. In other words, the image sensor 32 is controlled so as to perform exposure for these two frames.

[0034] However, if the subject 9 moves significantly between the exposure of the first frame and the exposure of the second frame, it becomes difficult to obtain an appropriate difference image 330. This will be described with reference to FIG.

[0035] 4A and 4B are diagrams showing an example of movement of the subject 9 between frames. The diagram shows the positional relationship between the subject 9 and the imaging range 30 when viewed from above (when viewed in the negative Z-axis direction). (A) of Fig. 4 shows the state during exposure of the first frame, i.e., exposure for obtaining image 330a. (B) of Fig. 4 shows the state during exposure of the second frame, i.e., exposure for obtaining image 330b.

[0036] The position of the subject 9 in the imaging range 30 is shifted by the amount of movement of the subject 9 between the first and second frames. This amount of shift is the same as the distance that the subject 9 moved from the time the first frame was exposed to the time the second frame was exposed, and is referred to as the amount of movement ΔL.

[0037] If the amount of movement ΔL is large, a change in brightness near the edge of the subject 9 where the slit light 20 is not projected may appear in the difference image 330, which may cause erroneous detection. To address this, for example, a filter process may be performed on the difference image 330 to leave only the slit light 20. Examples of the main processor of this process include the control unit 33 or a pre-processing unit 36 ​​described below. Alternatively, the frame rate may be increased (the frame interval may be shortened) so that the amount of movement ΔL becomes negligibly small. An example of a method for increasing the frame rate will be described later with reference to FIGS. 16 to 19.

[0038] 2, the difference image 330 generated by the image sensor 32 and the control unit 33 is sent to the signal processing unit 35. The signal processing unit 35 includes a preprocessing unit 36, a detection unit 37, and a mask generation unit 38.

[0039] The preprocessing unit 36 ​​performs preprocessing on the difference image 330. One example of the preprocessing is noise removal. For example, as described above with reference to FIG. 4 , a filter process is performed on the difference image 330 to leave only the slit light 20. This is not a limitation, and various known noise removal techniques may be used. For convenience, the difference image 330 after preprocessing will continue to be referred to as the difference image 330.

[0040] Based on the difference image 330, the detector 37 detects the center position of the slit light 20 projected onto the subject 9. This center position of the slit light 20 is also referred to as the center position 20c. Hereinafter, the center position of the slit light 20 projected onto the subject 9 is also simply referred to as the center position 20c of the slit light 20.

[0041] More specifically, the center positions 20c of the slit beam 20 detected by the detection unit 37 are the center positions 20c in the width direction (Y-axis direction) of the slit beam 20 at each position in the length direction (X-axis direction) of the slit beam 20. For example, of the pixels detecting the slit beam 20, the same number of center positions 20c as the number of pixels aligned in the length direction of the slit beam 20 are detected. A specific detection method will be described with reference to FIGS. 5 to 8.

[0042] 5 to 8 are diagrams showing examples of detecting the center position 20c of the slit light 20. FIG. 5 schematically shows the relationship between the image sensor 32 and the slit light 20 when viewed in a plan view. The pixels included in the image sensor 32 are referred to as pixels 321 and are shown in the figures. As described above, multiple pixels 321 are arranged in a two-dimensional array. In this example, the X-axis direction corresponds to the row direction of the array, and the Y-axis direction corresponds to the column direction of the array. The rows and columns of the pixels 321 are also referred to as pixel rows and pixel columns. The pixel columns in the two-dimensional array correspond to the short-side direction (Y-axis direction) of the slit light 20.

[0043] Fig. 6 shows an enlarged view of a portion of the pixel row surrounded by the thick line VI in Fig. 5. A white circle within a pixel 321 schematically indicates the center position of that pixel 321.

[0044] Of the pixels 321 that detect the slit beam 20, the pixel 321 that detects the light at the center position 20c of the slit beam 20 receives the greatest amount of light. The pixel with the greatest amount of incident light is also referred to as the max pixel. The pixel 321 adjacent to the max pixel is also referred to as the adjacent pixel.

[0045] Specifically, in the example shown in Figure 6, three pixels 321 detect the slit light 20. The max pixel is referred to as max pixel 321_n0 and illustrated. The adjacent pixels are referred to as adjacent pixel 321_n-1 and adjacent pixel 321_n+1 and illustrated. In the positive direction of the Y axis, adjacent pixel 321_n-1, max pixel 321_n0, and adjacent pixel 321_n+1 are located in this order. When there is no particular distinction between these, they are simply referred to as pixels 321.

[0046] FIG. 7 shows an example of the relationship between the position of each pixel 321 and the amount of incident light. The horizontal axis of the graph indicates the position in the pixel column in the Y-axis direction. Plots showing the center positions of adjacent pixel 321_n-1, max pixel 321_n0, and adjacent pixel 321_n+1 are shown with solid lines. These positions are identified, for example, by an address (y address) set for the pixel array. A plot showing the virtual center position 20c of the slit light 20, which is the detection target, is shown with a dashed line. The vertical axis of the graph indicates the amount of incident light I, which is expressed as a function of y. The amount of incident light I corresponds to the magnitude of the signal from each pixel 321 and can also be called a signal value, pixel value, brightness value, etc.

[0047] Based on the central position and incident light amount I of the max pixel 321_n0 and the central positions and incident light amounts I of the adjacent pixels 321_n-1 and 321_n+1, the position in the max pixel 321_n0 where the incident light amount is greatest is calculated (estimated, etc.). For example, the following equation (1) is used. In the equation, 321_n-1, 321_n0, and 321_n+1 indicate their central positions in the Y-axis direction.

[0048] 8 shows the detection result of the center position 20c of the slit beam 20 in the pixel row. In terms of pixel size, the position of max pixel 321_n0 is detected as the center position 20c of the slit beam 20. More specifically, using the above-mentioned calculation method, the center position 20c of the slit beam 20 in max pixel 321_n0 is calculated to be an order of magnitude smaller than the size of max pixel 321_n0. In other words, the center position 20c of the slit beam 20 is detected on the sub-pixel order.

[0049] 2 , for example, in the manner described above, the detector 37 detects the center position 20c of the slit light 20 projected onto the subject 9. From one difference image 330, multiple center positions 20c corresponding to respective positions in the longitudinal direction of the slit light 20 are detected.

[0050] As described above, the slit light 20 is scanned onto the subject 9, and multiple difference images 330 corresponding to each position of the subject 9 in the Y-axis direction are generated. Based on the multiple difference images 330 thus obtained, the detection unit 37 detects the center positions 20c of the multiple slit light beams 20 projected onto different positions on the subject 9.

[0051] The mask generating unit 38 generates a mask for removing outliers from the plurality of center positions 20c of the detected slit beam 20. The outliers will be described with reference to FIG.

[0052] Fig. 9 is a diagram showing an example of an outlier. As shown in the lower part of Fig. 9, light from the subject 9 onto which the slit light 20 is projected is detected by the image sensor 32. Using the method described above, the center position 20c of the slit light 20 is detected, as shown in the upper part of Fig. 9. In this example, the detection results of the center position 20c at each position in the longitudinal direction (X-axis direction) of the slit light 20 are illustrated superimposed on the image sensor 32.

[0053] As indicated by arrow AR1, an accurate center position 20c is detected in the central portion of the subject 9. On the other hand, as indicated by arrow AR2, values ​​far from the accurate center position 20c, i.e., outliers, are detected in the edge portions of the subject 9. The detection of such outliers can occur due to bright line angle, occlusion, and the like. For example, the larger the bright line angle, the larger the difference value between the center positions 20c of adjacent pixel columns can become.

[0054] The mask generation unit 38 ( FIG. 2 ) generates a mask for removing outliers. To do this, the outliers are first identified. For example, the mask generation unit 38 compares the center positions 20c detected by the detection unit 37 for each adjacent pixel column. The mask generation unit 38 calculates the difference between the center position 20c of one pixel column and the center position 20c of the adjacent pixel column. For example, the following equation (2) is used. tan θ in the equation corresponds to the difference value. x and x+1 indicate positions in the X-axis direction and are identified, for example, by the address (x address) of pixel 321. 20c(x) and 20c(x+1) indicate the center positions 20c in the pixel columns x and x+1.

[0055] For example, based on the difference value calculated as described above, the mask generation unit 38 determines whether the center position 20c of the pixel row (pixel row x or x+1) is an outlier. A threshold determination may be used, in which case, if the difference value is greater than a threshold, the center position 20c is determined to be an outlier. The threshold is set in, for example, the register 34.

[0056] The mask generation unit 38 generates a mask for removing outliers. For example, a mask is generated that removes only center positions 20c that correspond to outliers from among the detected center positions 20c. The mask may be realized using various formats such as a map, a table, or a mathematical formula.

[0057] If there are no outliers, a mask need not be generated, or a mask that passes the detection result of the detection unit 37 as is may be generated.

[0058] Returning to FIG. 2 , the IF unit 39 is an interface unit for transmitting and receiving data to and from devices external to the imaging unit 3. In this example, the IF unit 39 transmits data on the center position 20c of the slit beam 20 detected by the detection unit 37 and data on the mask generated by the mask generation unit 38 to the processing unit 4. For example, the amount of data transmitted is significantly reduced (e.g., by approximately 99.9%) compared to transmitting the data of the difference image 330 as is. This increases the likelihood of avoiding limitations on the processing speed due to data transmission from the IF unit 39 to the processing unit 4.

[0059] To reiterate, the slit light 20 is irradiated onto the subject 9 and scanned in the Y-axis direction. While the position of the slit light 20 projected onto the subject 9 is gradually changed (scanned), multiple difference images 330 corresponding to each position on the subject 9 are generated. For each of the multiple difference images 330, the detection unit 37 detects the center position 20c of the slit light 20, and the mask generation unit 38 generates a mask. This data is transmitted from the IF unit 39 to the processing unit 4.

[0060] The processing unit 4 controls the light source unit 2 and the imaging unit 3, and processes data from the imaging unit 3. The processing unit 4 includes a register control unit 41 and an image processing unit .

[0061] The register control unit 41 sets the register 23 of the light source unit 2 and the register 34 of the imaging unit 3, thereby controlling the light source unit 2 and the imaging unit 3. One example of control is synchronous control of the on / off of the light source unit 2 and the exposure of each pixel 321 of the imaging element 32 of the imaging unit 3. The light source unit 2 and the imaging unit 3 may be controlled by a method other than register setting, and in that case the register control unit 41 may also be simply referred to as a control unit.

[0062] The image processing unit 42 processes the data from the imaging unit 3. Specifically, the mask generated by the mask generation unit 38 is used to remove outliers from the center positions 20c of the slit light 20 detected by the detection unit 37 of the imaging unit 3. Based on the remaining center positions 20c, the object 9 is measured, and an image of the object 9 is generated. The measurement of the object 9 includes measurement of the three-dimensional shape of the object 9. An example of an image of the object 9 is a distance image, which will be referred to as distance image 420.

[0063] Unless otherwise specified, the center position 20c of the slit light 20 handled by the processing unit 4 is the center position 20c after the outliers have been removed.

[0064] The image processing unit 42 includes a distance measurement unit 43 , a shape synthesis unit 44 , and a memory control unit 45 .

[0065] Distance measurement unit 43 measures the distance to subject 9 based on center position 20c of slit light 20. One example of the distance reference is transport unit 5 on which subject 9 is placed, and in this case, the distance from the upper surface (the surface on the positive Z-axis direction side) of transport unit 5 to slit light 20 projected onto subject 9 is measured as the height (length in the Z-axis direction) of subject 9 at that position. The measurement principle will be described with reference to FIG. 10 .

[0066] Fig. 10 is a diagram showing an example of the measurement principle. The optical center of the image sensor 32 is referred to as the optical center 32c. In Fig. 10, the position of the center position 20c at the same height (position in the Z-axis direction) as the optical center 32c is indicated by a white circle as the center position 20c. The distance from the upper surface (the surface on the positive Z-axis direction side) of the transport unit 5 to the center position 20c is referred to as the height g.

[0067] The distance from the optical center 32c to the central position 20c is referred to as the base length L (L). The focal length of the lens included in the imaging unit 3 is referred to as f. Two different positions in the Y-axis direction are indicated as y1 and yn. y1 is the central position 20c when there is no subject 9 and is set as the reference position. yn indicates the central position 20c of the same pixel row as y1 in the nth frame. The distance (length in the Z-axis direction) from the top surface (the surface on the positive Z-axis side) of the transport unit 5 to the slit light 20 projected onto the subject 9 is referred to as the distance Zn. The distance from there to the central position 20c is referred to as the height h.

[0068] From the similarity relationship between the two triangles in FIG. 10, the height h is calculated as in the following equation (3).

[0069] The same applies to the height g. Therefore, the distance Zn to the subject 9 is calculated as in the following equation (4).

[0070] For example, as described above, the distance from the transport unit 5 to the slit light 20 projected onto the subject 9 is calculated (measured) as the distance Zn. From the calculated distance Zn, the cross-sectional shape of the subject 9 at the portion onto which the slit light 20 is projected (the cross-sectional shape as viewed in the Y-axis direction) is determined.

[0071] The distance Zn of each position on the subject 9 in the Y-axis direction is measured in accordance with the scanning of the irradiation of the slit light 20. For example, the three-dimensional shape of the subject 9 is measured by integrating the distance Zn of each position in the time direction.

[0072] Returning to Fig. 2, the shape synthesis unit 44 synthesizes the distances Zn of each position of the subject 9 measured by the distance measurement unit 43, in other words, the cross-sectional shape of the subject 9. This allows the overall shape of the subject 9, i.e., the three-dimensional shape, to be grasped. For example, a distance image 420 of the subject 9 is generated. This will be described with reference to Fig. 11 as well.

[0073] Fig. 11 is a diagram showing an example of a distance image 420. In the illustrated distance image 420, each position of the subject 9 is represented by a different color according to the distance. Note that the example of Fig. 11 is not limiting, and various types of distance images 420 may be generated, and images other than distance images may also be generated.

[0074] 2, the memory control unit 45 accesses the memory (not shown) of the processing unit 4 to read and write data. Various types of data used by the processing unit 4 are handled. One example of the data is the center position 20c and mask data transmitted from the imaging unit 3. The amount of this data is small compared to the amount of image data itself, which makes memory access by the memory control unit 45 more efficient.

[0075] The functions of each part of the processing unit 4 described above may be realized by hardware design, by software design, or by both hardware and software design.

[0076] 12 is a diagram showing an example of a process (measurement method) executed in the measurement system 1. Description of content that overlaps with the above will be omitted where appropriate.

[0077] In step S1, the light source unit 2 and the imaging unit 3 are controlled. This control is for acquiring signals necessary for generating the difference image 330 from the imaging element 32. The register control unit 41 of the processing unit 4 sets the register 23 of the light source unit 2 and the register 34 of the imaging unit 3 so that exposure, signal generation, readout, etc. of each pixel 321 of the imaging element 32 are performed in accordance with the turning on and off of the light source unit 2.

[0078] In step S2, a difference image 330 is generated based on the signal from the image sensor 32 obtained by controlling the light source unit 2 and the image capturing unit 3 in the previous step S1.

[0079] As a specific method for the above-described steps S1 and S2 for generating the difference image 330, two types of methods may be selectively used.

[0080] <First Method> In the first method, first, exposure is performed to obtain a first frame image, for example, image 330a shown in FIG. 3 described above, and the resulting signal (value) is stored in a frame memory. Next, exposure is performed to obtain a second frame image, for example, image 330b shown in FIG. 3 described above, and the difference value between the resulting signal and the signal stored in the frame memory is calculated. This difference value becomes the signal value of difference image 330, and thus difference image 330 is generated.

[0081] <Second Method> In the second method, the charge storage unit in the pixel 321, AZ (auto-zero) adjustment during AD conversion, and the like are effectively utilized. This allows for frame memoryless operation and also increases the frame rate. Details of the second method will be described later with reference to FIGS. 16 to 19.

[0082] In step S3, noise is removed. As an example of preprocessing, the preprocessing unit 36 ​​of the signal processing unit 35 of the imaging unit 3 performs noise removal processing on the difference image 330 generated in the previous step S2.

[0083] In step S4, the max pixel and adjacent pixels are identified. As described above with reference to Fig. 6, the detection unit 37 of the signal processing unit 35 of the imaging unit 3 identifies the max pixel 321_n0 having the largest amount of incident light, and the adjacent pixels 321_n-1 and 321_n+1 adjacent to the max pixel 321_n0.

[0084] In step S5, the center position 20c of the slit beam 20 is detected. As previously described with reference to Figures 7 and 8, the detection section 37 of the signal processing section 35 of the imaging unit 3 detects the center position 20c of the slit beam 20 based on the positions and incident light amounts of the max pixel 321_n0, the adjacent pixel 321_n-1, and the adjacent pixel 321_n+1. The center position 20c is detected with accuracy on the order of subpixels.

[0085] In step S6, a mask is generated. The mask generation section 38 of the signal processing section 35 of the imaging unit 3 generates a mask for removing outliers from the center position 20c detected by the detection section 37.

[0086] As explained above, the slit light 20 is scanned onto the subject 9, and a plurality of difference images 330 corresponding to each position on the subject 9 are generated. For each of the plurality of difference images 330, the detection unit 37 detects the center position 20c of the slit light 20, and the mask generation unit 38 generates a mask.

[0087] In step S7, the subject 9 is measured. The distance measurement unit 43 of the image processing unit 42 of the processing unit 4 measures the distance from the upper surface of the transport unit 5 to the center position 20c of the slit beam 20 detected in the previous step S5 and the mask generated in the previous step S6. This measurement corresponds to, for example, the calculation of the distance Zn in FIG. 10 described above. The shape synthesis unit 44 synthesizes the distances Zn of each position of the subject 9 measured by the distance measurement unit 43, i.e., the cross-sectional shape of the subject 9. For example, a distance image 420 such as that shown in FIG. 11 described above is generated.

[0088] The measurement system 1 described above can improve the measurement performance of the subject 9 in various aspects, such as higher accuracy, higher speed, and higher robustness. For example, by using the difference image 330, the center position 20c of the slit beam 20 can be detected more accurately than when the difference image 330 is not used. Furthermore, compared to detecting the center position of the slit beam, as described above, robustness can be improved. Generating a mask to remove outliers from the center position 20c also improves robustness. Instead of transmitting image data directly from the imaging unit 3 to the processing unit 4, data on the center position 20c of the slit beam 20 and the mask obtained by processing by the imaging unit 3 are transmitted. Because the amount of data is reduced, rate-limiting problems due to the IF unit 39 are less likely to occur. The processing load on the processing unit 4 is also reduced, resulting in faster overall processing by the measurement system 1.

[0089] The improvement in robustness and accuracy will be explained using a comparative example.

[0090] <Increasing Robustness> Fig. 13 is a diagram comparing the presence and absence of a difference image. The results of detection of the slit light 20 in the image sensor 32 are shown. (A1) and (A2) of Fig. 13 show the results of detection of the center position 20c of the slit light 20 when using the difference image 330. The x address and y address indicate the positions of each pixel 321 in the image sensor 32 in the X-axis direction and Y-axis direction. The center position 20c of the slit light 20 in the Y-axis direction is detected and specified by the y address. (A2) of Fig. 13 shows the error. The error is expressed as a value converted into the size of one pixel 321 (in pixels).

[0091] 13 (E1) and (E2) show a comparative example. In this comparative example, the difference image 330 is not used, and the center position 20c of the slit light 20 is detected based only on the image of the subject 9 onto which the slit light 20 is projected. The image may include not only the slit light 20 but also ambient light and the like.

[0092] 13, by using the difference image 330, the influence of ambient light and the like is eliminated, and the variation in the detection error of the center position 20c of the slit beam 20 is significantly reduced, thereby achieving high robustness.

[0093] Fig. 14 shows a comparison between the presence and absence of a mask. (A1), (A2), and (A3) of Fig. 14 show the detection results of the center position 20c of the slit beam 20 when outliers are removed using a mask. (A3) shows an enlarged vertical axis of (A2). (E1) and (E2) of Fig. 14 show comparative examples. In the comparative examples, outliers are not removed using a mask.

[0094] 14, by using the mask, the center position 20c of the slit light 20, which is clearly erroneously detected, is removed, thereby achieving high robustness.

[0095] <High Accuracy> Fig. 15 shows an example of high accuracy. Fig. 15A shows the detection result of the center position 20c of the slit beam 20 when using the difference image 330 and mask as described above, more specifically, the error. Fig. 15E shows a comparative example. In this comparative example, the center of gravity of the slit beam is detected using a binarization method.

[0096] 15, by detecting the center position 20c of the slit light 20 using the differential image 330 and the mask, the amount of information is not lost and detection accuracy is improved compared to when the center position is detected by a binarization method.

[0097] 12, the first method and the second method are selectively used as specific methods for generating the difference image 330. The second method will be described in further detail below.

[0098] 16 is a flowchart showing an example of processing when the second technique is used. The illustrated processing corresponds to one specific example of steps S1 and S2 in FIG. 12 described above.

[0099] The processing of step S1 is exemplified by the processing of steps S11 to S13. As will be described in detail later, in step S11, the signal of the first frame is held. In step S12, auto-zero (AZ) adjustment is performed based on the signal of the first frame. In step S13, the signal of the second frame is AD converted. The signal value thus obtained corresponds to the difference value between the signal of the first frame and the signal of the second frame. In step S2, a difference image 330 is generated based on the obtained signal value. The configurations and operations of the image sensor 32 and control unit 33 related to these processes will be described with reference to FIGS. 17 to 19.

[0100] 17 is a diagram showing an example of a schematic configuration of the image sensor 32 and the control unit 33. The image sensor 32 is shown as a pixel array unit including a plurality of pixels 321. Also, some peripheral circuits and signal lines are shown with reference numerals.

[0101] The peripheral circuits are indicated by reference numerals, and include a control circuit 331, a vertical drive circuit 332, a DAC circuit 333, a column signal processing circuit 334, a horizontal drive circuit 335, and an output circuit 336. The wirings are indicated by reference numerals, and include a signal line HSL1, a signal line VSL1, and a signal line 339.

[0102] The pixel 321 includes a photoelectric conversion unit. The photoelectric conversion unit generates an electric charge according to the amount of incident light. An example of the photoelectric conversion unit is a photodiode (PD). A circuit is also provided that generates and outputs a voltage signal (pixel signal) according to the amount of electric charge generated in the photoelectric conversion unit. The pixel 321 may be interpreted as including such a circuit, and may also be called a pixel circuit.

[0103] The control circuit 331 receives data instructing an input clock, an operation mode, etc., and outputs data such as internal information of the photodetector device 100. The control circuit 331 generates clock signals and control signals that serve as references for the operations of the vertical drive circuit 332, the DAC circuit 333, the column signal processing circuit 334, the horizontal drive circuit 335, etc., based on a vertical synchronization signal, a horizontal synchronization signal, and a master clock. The control circuit 331 supplies these generated signals to the vertical drive circuit 332, the DAC circuit 333, the column signal processing circuit 334, the horizontal drive circuit 335, etc.

[0104] The vertical drive circuit 332 includes, for example, a shift register. The vertical drive circuit 332 is connected to the image sensor 32 (pixel array section) via a plurality of signal lines HSL1 (horizontal signal lines) extending in the row direction of the pixels 321. Each signal line HSL1 extends, for example, for each pixel row, and each signal line HSL1 may include a plurality of signal lines. The vertical drive circuit 332 supplies a drive signal (for example, a pulse signal) for driving the pixels 321 to a selected signal line HSL1.

[0105] Driving of the pixels 321 by the vertical drive circuit 332 includes driving of transistors ( FIG. 18 ) described below. The transistors are driven to output voltage signals (pixel signals) corresponding to the amount of charge generated in the photoelectric conversion units in the pixels 321 to corresponding signal lines VSL1 among a plurality of signal lines VSL1 (vertical signal lines) extending in the column direction of the pixels 321.

[0106] The DAC circuit 333 generates a RAMP signal by DA (Digital to Analog) conversion and supplies the generated RAMP signal to the column signal processing circuit 334.

[0107] The column signal processing circuit 334 is connected to the light source unit 2 (pixel array section) via a signal line VSL1. Each signal line VSL1 may include a plurality of signal lines. The column signal processing circuit 334 is arranged, for example, for each pixel column, and performs signal processing such as noise removal for each pixel column on pixel signals from one row of pixels 321. The column signal processing circuit 334 performs signal processing such as CDS (Correlated Double Sampling) for removing fixed pattern noise specific to the pixels 321, signal amplification, and AD (Analog to Digital) conversion.

[0108] The horizontal drive circuit 335 includes, for example, a shift register. The horizontal drive circuit 335 sequentially outputs horizontal scanning pulses to select each of the column signal processing circuits 334 in turn, and causes each of the column signal processing circuits 334 to output a pixel signal to a signal line 339.

[0109] The output circuit 336 performs signal processing on the pixel signals sequentially supplied from each of the column signal processing circuits 334 via a signal line 339, and outputs the processed signals. For example, buffering, black level adjustment, column variation correction, various digital signal processing, etc. are performed on the pixel signals.

[0110] The control circuit 331, vertical drive circuit 332, DAC circuit 333, column signal processing circuit 334, horizontal drive circuit 335, and output circuit 336 are included in the control unit 33 (FIG. 2) described above, for example.

[0111] 18 is a diagram showing an example of a pixel circuit. The photoelectric conversion unit included in pixel 321 is shown as photoelectric conversion unit PD1. As mentioned above, photoelectric conversion unit PD1 generates electric charges according to the amount of incident light. In FIG. 2, photoelectric conversion unit PD1 is shown as a photodiode with an anode connected to GND (ground).

[0112] Examples of circuit elements provided around the photoelectric conversion unit PD1 include a transistor TR1, a charge storage unit FD1, a transistor TR2, a transistor TR3, and a transistor TR4. In the following description, when a transistor is connected between two elements, it means that one of the source and drain of the transistor is connected to one element, and the other of the source and drain is connected to the other element.

[0113] The transistor TR1 is connected between the photoelectric conversion unit PD1 and the charge storage unit FD1, and transfers the charges generated in the photoelectric conversion unit PD1 and stored in the photoelectric conversion unit PD1 to the charge storage unit FD1. The transistor TR1 can also be called a transfer transistor.

[0114] The gate electrode of the transistor TR1 is connected to a corresponding signal line HSL1. The on / off (conduction / non-conduction) of the transistor TR1 is controlled by a control signal from the signal line HSL1. When the transistor TR1 is on, the charge of the photoelectric conversion unit PD1 is transferred to the charge storage unit FD1 via the transistor TR1.

[0115] The charge storage unit FD1 stores the charge of the photoelectric conversion unit PD1 transferred via the transistor TR1 and generates a voltage according to the stored charge. The charge storage unit FD1 is configured to include, for example, a floating diffusion.

[0116] The transistor TR2 is connected between the charge storage unit FD1 and the power supply node VDD, and discharges the charge stored in the charge storage unit FD1 to the power supply node VDD. The transistor TR2 can also be called a reset transistor. The letters RST representing this are also shown in the figure.

[0117] The gate electrode of transistor TR2 is connected to a corresponding signal line HSL1. The on / off state of transistor TR2 is controlled by a control signal from signal line HSL1. When transistor TR2 is on, the charge in charge storage unit FD1 is discharged to the power supply node VDD via transistor TR2. When transistor TR1 is on, the charge in photoelectric conversion unit PD1 is also discharged.

[0118] The transistor TR3 is connected between the power supply node VDD and the transistor TR4. The gate of the transistor TR3 is connected to the charge storage unit FD1. The transistor TR3 amplifies and outputs the voltage generated in the charge storage unit FD1. The transistor TR3 can also be called an amplifying transistor.

[0119] The transistor TR4 is connected between the transistor TR3 and the signal line VSL1. The transistor TR4 selectively outputs the output voltage of the transistor TR3 to the signal line VSL1. The transistor TR4 can also be called a selection transistor. The letters SEL representing this are also shown in the figure.

[0120] The gate electrode of transistor TR4 is connected to the corresponding signal line HSL1. The on / off state of transistor TR4 is controlled by a control signal from the signal line HSL1. When transistor TR4 is on, the output voltage of transistor TR3 is output to signal line VSL1 via transistor TR4. This signal is supplied to the column signal processing circuit 334 described above via signal line VSL1 and processed.

[0121] For example, by using an image sensor 32 and a control unit 33 (FIG. 2) having the configurations shown in FIGS. 17 and 18 above, it is possible to obtain signals for the first and second frames at high speed, i.e., to increase the frame rate.

[0122] 19 is a timing chart showing an example of the operation of the image sensor 32 and the control unit 33. SEL indicates the on / off state of transistor TR4 (selection transistor). RST indicates the on / off state of transistor TR2 (reset transistor). TRG indicates the trigger for starting counting by the counter circuit for AD conversion. AZ indicates auto-zero adjustment. FD1 indicates the amount of charge in the charge storage unit FD1. VSL1 indicates the potential of the signal line VSL1. DAC indicates the RAMP signal output by the DAC circuit 333. CN indicates the count value (digital value) of the counter circuit.

[0123] It is assumed that the first frame exposure has been performed and the resulting charge has been accumulated in the charge accumulation unit FD1. That is, the charge corresponding to the amount of incident light when the light source unit 2 is off is accumulated in the charge accumulation unit FD1 of each pixel 321. This accumulation corresponds to the processing of step S11 in FIG. 16 described above.

[0124] At time t1, the transistor TR4 (SEL) is turned on, and a signal corresponding to the amount of charge stored in the charge storage unit FD1 is read out.

[0125] Between time t2 and time t3, AZ adjustment is performed based on the signals read out at time t1, i.e., the signals from the plurality of pixels 321 obtained when the light source unit 2 was off. The potential of the signal line VSL1 and the potential of the RAMP signal of the DAC circuit 333 are made uniform. This adjustment corresponds to the processing of step S12 in FIG. 16 described above.

[0126] Between time t4 and time t5, the transistor TR2 is turned on, and the charge in the charge storage unit FD1 is discharged. After that, the second exposure is performed while the light source unit 2 is on, and a signal corresponding to the amount of exposure light is read out.

[0127] At time t6, after the previous AZ adjustment, signals from the multiple pixels 321 obtained when the light source unit was on are AD converted. Specifically, the start of counting the counter circuit is triggered, and counting continues until time t7. This count value becomes the difference value between the signal corresponding to the exposure light amount of the first frame and the signal corresponding to the exposure light amount of the second frame. This count corresponds to the processing of step S13 in FIG. 16 described above.

[0128] The obtained difference values ​​correspond to the signal values ​​of the difference image 330 described above, and therefore the difference image 330 is generated based on the difference values. This generation corresponds to the processing in step S2 in FIG. 16 described above.

[0129] According to the second technique described above, the difference image 330 can be generated without using a frame memory. Furthermore, by effectively utilizing the charge storage unit F1 in the pixel 321, AZ (auto-zero) adjustment during AD conversion in the column signal processing circuit 334, and the like, the difference values ​​that form the basis of the difference image 330 can be obtained quickly. In other words, the frame rate can be increased. For example, the movement amount ΔL of the subject 9 between frames, which was previously described with reference to FIG. 4, can be reduced.

[0130] 2. Modifications The disclosed technology is not limited to the above embodiment. For example, some of the functions of the processing unit 4 described above may be incorporated into the imaging unit 3. This will be described with reference to FIG. 20 .

[0131] Fig. 20 is a diagram showing a modified example. The measurement system 1 shown in Fig. 20 differs from the previously described Fig. 2 in that the imaging unit 3 includes a distance measurement unit 43, rather than the processing unit 4.

[0132] In this example, the signal processing unit 35 of the image sensor 31 of the imaging unit 3 includes a distance measurement unit 43. The distance measurement unit 43 measures the distance to the subject 9 based on the center position 20c of the slit light 20 detected by the detection unit 37 and the mask generated by the mask generation unit 38. The IF unit 39 transmits data on the measurement results of the distance measurement unit 43 to the processing unit 4. Based on this data, the shape synthesis unit 44 of the image processing unit 42 of the processing unit 4 synthesizes a cross-sectional shape of the subject 9. For example, a distance image 420 is generated.

[0133] According to the above modification, the processing of the distance measurement section 43 is completed within the imaging unit 3, and therefore the processing load on the processing unit 4 can be reduced accordingly.

[0134] 20 and the previously described configuration of FIG. 2 are also possible. That is, both the imaging unit 3 and the processing unit 4 may include a distance measurement unit 43. Which distance measurement unit 43 to use may be selectable by mode selection or the like.

[0135] Any function of the processing unit 4 may be incorporated into the imaging unit 3, not limited to the distance measurement unit 43.

[0136] 3. Summary The techniques described above can be specified, for example, as follows. One of the techniques disclosed is a measurement system 1. As described with reference to FIGS. 1 to 3 and 5 to 20 , the measurement system 1 includes a light source unit 2 that irradiates a subject 9 with a slit beam of light 20, an imaging unit 3 that detects a center position 20c in the lateral direction (Y-axis direction) of the slit beam of light 20 projected onto the subject 9 at each position in the longitudinal direction (X-axis direction) of the slit beam of light 20 projected onto the subject 9, based on a difference image 330 that indicates a difference between when the light source unit 2 is off and when it is on, and a processing unit 4 that measures the subject 9 based on the center position 20c of the slit beam of light 20 detected by the imaging unit 3.

[0137] According to the measurement system 1 described above, by using the difference image 330, the center position 20c of the slit beam 20 can be detected more accurately than when the difference image 330 is not used. Furthermore, compared to detecting the center position of the slit beam, robustness can be improved. Furthermore, image data is not sent directly from the imaging unit 3 to the processing unit 4; instead, data on the center position 20c of the slit beam 20 and the mask are sent. Because the amount of data is reduced, the problem of IF rate limitation is less likely to occur. The processing load on the processing unit 4 is also reduced, resulting in faster overall processing in the measurement system 1. These various aspects contribute to improved measurement performance.

[0138] 5 to 8 , the imaging unit 3 includes a plurality of pixels 321 arranged in a two-dimensional array, a pixel row in the two-dimensional array corresponding to the short-side direction (Y-axis direction) of the slit light 20, each of the plurality of pixels 321 outputting a signal according to the amount of incident light, and the imaging unit 3 may detect the position of max pixel 321_n0, among the pixels 321 in the pixel row, which has the greatest amount of incident light, as the center position 20c of the slit light 20. More specifically, the imaging unit 3 may calculate the position of max pixel 321_n0 where the amount of incident light is greatest on the order of magnitude smaller than the size of max pixel 321_n0 (subpixel order), and detect the calculated position as the center position 20c of the slit light 20. Specifically, the imaging unit 3 may calculate the position in the max pixel 321_n0 where the amount of incident light is greatest based on the center position and incident light amount of the max pixel 321_n0 in the pixel row, and the center positions and incident light amounts of the adjacent pixels 321_n-1 and 321_n+1 adjacent to the max pixel 321_n0 in the pixel row. In this way, for example, the center position 20c of the slit light 20 projected onto the subject 9 can be detected with high accuracy.

[0139] As described with reference to Figures 16 to 19, the imaging unit 3 may generate the difference image 330 based on signal values ​​obtained by AD converting signals from the plurality of pixels 321 obtained when the light source unit 2 is on, after performing AZ (auto-zero) adjustment based on signals from the plurality of pixels 321 obtained when the light source unit 2 is off. For example, each of the plurality of pixels 321 may include a charge storage unit FD1 that stores a charge corresponding to the amount of incident light when the light source unit 2 is off, and the AZ adjustment may be performed based on a signal corresponding to the charge stored in the charge storage unit FD1. For example, by effectively utilizing the charge storage unit FD1 in the pixel 321, the AZ adjustment during AD conversion, and the like, the difference image 330 can be generated quickly. A frame memory is also not required.

[0140] As described with reference to Figures 2 and 9, the imaging unit 3 may generate a mask to remove outliers from the center positions 20c of the slit light 20 at each position in the longitudinal direction (X-axis direction) of the slit light 20. For example, the center positions 20c of the slit light 20 corresponding to outliers may be center positions 20c whose difference from adjacent center positions 20c is greater than a threshold. By generating such a mask, it is possible to remove obvious outliers from the detected center positions 20c. This can further improve robustness.

[0141] 1 , 2 , 9 , 13 , 14 , etc., the imaging unit 3 may detect the center position 20c of each of the multiple slit beams 20 projected at different positions on the subject 9, based on multiple difference images 330 obtained by scanning the subject 9 with the slit beams 20. For example, the measurement system 1 may include a transport unit 5 that transports the subject 9, and the subject 9 may be moved by the transport, thereby scanning the subject 9 with the slit beams 20. This allows the three-dimensional shape of the subject 9 to be measured.

[0142] The imaging unit 3 described with reference to Figures 1 to 3 and 5 to 20 is also one of the disclosed technologies. The imaging unit 3 is used together with a light source unit 2 that irradiates a slit of light onto an object 9. The imaging unit 3 includes a detection unit 37 that detects a center position 20c in the short direction (Y-axis direction) of the slit of light 20 projected onto the object 9 at each position in the long direction (X-axis direction) of the slit of light 20 projected onto the object 9, based on a difference image 330 that shows the difference between when the light source unit 2 is off and when it is on. As described above, this imaging unit 3 can also improve measurement performance.

[0143] The effects described in this disclosure are merely examples and are not limited to the disclosed contents. Other effects may also be obtained.

[0144] Although the embodiments of the present disclosure have been described above, the technical scope of the present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present disclosure. Furthermore, components of different embodiments and modifications may be combined as appropriate.

[0145] The present technology can also be configured as follows: (1) A measurement system comprising: a light source unit that irradiates a subject with a slit light; an imaging unit that detects a center position in a short direction of the slit light at each position in a long direction of the slit light projected onto the subject based on a differential image that shows a difference between when the light source unit is off and when it is on; and a processing unit that measures the subject based on the center position of the slit light detected by the imaging unit. (2) The measurement system described in (1), wherein the imaging unit includes a plurality of pixels arranged in a two-dimensional array, a pixel column in the two-dimensional array corresponds to the short direction of the slit light, and each of the plurality of pixels outputs a signal according to an amount of incident light, and the imaging unit detects the position of a max pixel in the pixel column that has the largest amount of incident light as the center position of the slit light. (3) The measurement system according to (2), wherein the imaging unit calculates the position in the max pixel where the amount of incident light is maximum on the order of magnitude smaller than the size of the max pixel and detects the calculated position as the center position of the slit light. (4) The measurement system according to (3), wherein the imaging unit calculates the position in the max pixel where the amount of incident light is maximum based on the center position and amount of incident light of the max pixel in the pixel row and the center positions and amounts of incident light of adjacent pixels adjacent to the max pixel in the pixel row. (5) The measurement system according to any of (2) to (4), wherein the imaging unit generates the difference image based on signal values ​​obtained by AD converting signals from the plurality of pixels obtained when the light source unit is on, after performing AZ (auto-zero) adjustment based on signals from the plurality of pixels obtained when the light source unit is off. (6) The measurement system according to (5), wherein each of the plurality of pixels includes a charge accumulation unit that accumulates a charge corresponding to an amount of incident light when the light source unit is off, and the AZ adjustment is performed based on a signal corresponding to the charge accumulated in the charge accumulation unit.(7) The measurement system according to any one of (1) to (6), wherein the imaging unit generates a mask for removing outliers from the center position of the slit light at each position in the longitudinal direction of the slit light. (8) The measurement system according to (7), wherein the center position of the slit light corresponding to the outlier is a center position whose difference from an adjacent center position is greater than a threshold. (9) The measurement system according to any one of (1) to (8), wherein the imaging unit detects the center position of each of the plurality of slit lights projected at different positions on the subject based on the plurality of difference images obtained by scanning the subject with the slit light. (10) The measurement system according to any one of (1) to (8), comprising a transport unit that transports the subject, wherein the subject moves by the transport, thereby scanning the subject with the slit light. (11) An imaging unit used together with a light source unit that irradiates a subject with a slit light, the imaging unit comprising: a detection unit that detects a center position in the short direction of the slit light at each position in the long direction of the slit light projected onto the subject, based on a differential image that shows a difference between when the light source unit is off and when it is on.

[0146] 1 Measurement system 2 Light source unit 20 Slit light 21 Laser element 22 Control unit 23 Register 3 Imaging unit 30 Imaging range 31 Image sensor 32 Imaging element 321 Pixel 321_n0 Max pixel 321_n-1 Adjacent pixel 321_n+1 Adjacent pixel 33 Control unit 330 Difference image 330a Image 330b Image 331 Control circuit 332 Vertical drive circuit 333 DAC circuit 334 Column signal processing circuit 335 Horizontal drive circuit 336 Output circuit 339 Signal line 34 Register 35 Signal processing unit 36 ​​Preprocessing unit 37 Detection unit 38 Mask generation unit 39 IF unit 4 Processing unit 41 Register control unit 42 Image processing unit 43 Distance measurement unit 44 Shape synthesis unit 45 Memory control unit 5 Transport unit 9 Object FD1 Charge storage unit HSL1 Signal line PD1 Photoelectric conversion unit TR1 Transistor TR2 Transistor TR3 Transistor TR4 Transistor VSL1 Signal line

Claims

1. A measurement system comprising: a light source unit that irradiates a subject with a slit of light; an imaging unit that detects the center position of the slit of light in the short direction at each position in the long direction of the slit of light projected onto the subject based on a differential image that shows the difference between when the light source unit is off and when it is on; and a processing unit that measures the subject based on the center position of the slit of light detected by the imaging unit.

2. The measurement system of claim 1, wherein the imaging unit includes a plurality of pixels arranged in a two-dimensional array, a pixel row in the two-dimensional array corresponds to the short direction of the slit light, each of the plurality of pixels outputs a signal according to the amount of incident light, and the imaging unit detects the position of a max pixel in the pixel row that has the greatest amount of incident light as the center position of the slit light.

3. The measurement system according to claim 2, wherein the imaging unit calculates the position where the amount of incident light in the max pixel is maximum on an order of magnitude smaller than the size of the max pixel, and detects the calculated position as the center position of the slit light.

4. The measurement system according to claim 3, wherein the imaging unit calculates the position in the max pixel where the amount of incident light is maximum based on the center position and amount of incident light of the max pixel in the pixel row, and the center positions and amounts of incident light of adjacent pixels adjacent to the max pixel in the pixel row.

5. The measurement system according to claim 2, wherein the imaging unit generates the differential image based on signal values ​​obtained by AD converting signals from the plurality of pixels obtained when the light source unit is on, after AZ (auto-zero) adjustment based on signals from the plurality of pixels obtained when the light source unit is off.

6. The measurement system according to claim 5, wherein each of the plurality of pixels includes a charge accumulation section that accumulates a charge corresponding to the amount of incident light when the light source unit is off, and the AZ adjustment is performed based on a signal corresponding to the charge accumulated in the charge accumulation section.

7. The measurement system according to claim 1, wherein the imaging unit generates a mask for removing outliers from the center position of the slit light at each position in the longitudinal direction of the slit light.

8. The measurement system according to claim 7, wherein the center position of the slit light corresponding to the outlier is a center position whose difference from an adjacent center position is greater than a threshold value.

9. The measurement system according to claim 1, wherein the imaging unit detects the center position of each of the plurality of slit lights projected at different positions on the subject based on the plurality of difference images obtained by scanning the subject with the slit light.

10. The measurement system according to claim 1, further comprising a transport unit that transports the subject, and the subject is moved by the transport, thereby scanning the irradiation of the slit light onto the subject.

11. An imaging unit used together with a light source unit that irradiates a subject with a slit of light, the imaging unit comprising: a detection unit that detects the center position in the short direction of the slit of light projected onto the subject at each position in the long direction of the slit of light, based on a differential image that shows the difference between when the light source unit is off and when it is on.

Images