Method for calibrating a shape measurement device

Abstract

To provide a calibration method for shape measurement device that can measure a surface shape of an object of measurement with high precision.SOLUTION: A calibration method for a shape measurement device 100 comprises: calibrating a luminaire 10 itself to adjust the position of the luminaire 10 and the angle of the luminaire 10 viewed from an extension direction of linear light 15 so that a reflected light image RI is projected on a screen 20. The calibration method further comprises: using a calibration plate having a marker on its surface and arranging the calibration plate so that the marker is at an inspection position; and adjusting a swing angle of the luminaire 10 viewed from a normal direction of an object 1 of measurement and a conveyance-directional position of the luminaire 10 viewed from the normal direction of the object 1 of measurement.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for calibrating a shape measuring instrument. [Background technology]

[0002] Conventionally, when measuring the surface shape of an object, such as the unevenness or roughness of the surface, a measurement method using the light-section method has been used, in which a linear light is irradiated onto the surface of the object and the surface shape of the object is detected by detecting the displacement of the linear light from a reference position. The light-section method is useful because it can measure minute surface shapes with high accuracy using a relatively simple device.

[0003] On the other hand, if an attempt is made to detect even smaller surface shapes using the light-section method, the line width of the linear light must be reduced in principle, which places a limit on how much the resolution can be improved.

[0004] Therefore, in such cases, a measurement method using an optical lever has been used, in which a linear light is irradiated onto the surface of the object to be measured, the light reflected by the surface of the object to be measured is projected onto a distant screen, and the displacement of the reflected light image projected onto the screen is detected to measure the surface shape of the object to be measured (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6278171 [Patent Document 2] Patent No. 4081414 Summary of the Invention [Problem to be solved by the invention]

[0006] By using the optical lever method, the displacement of a linear light beam on the surface of the object being measured can be magnified as the displacement of a reflected light image on a screen, enabling measurements with higher resolution than when using the light-section method.

[0007] However, when using the optical lever method, unless the various parameters that define the relationship between each element, such as the lighting device that irradiates linear light, the screen onto which the reflected light image is projected, and the imaging device that captures the reflected light image projected onto the screen, are properly calibrated in advance, errors caused by such calibration defects will be magnified in the same way as displacement.

[0008] Therefore, in order to accurately measure the surface shape of an object using the optical lever method, it was necessary to calibrate the various parameters that define the relationships between elements such as the lighting device and screen with greater precision than when using the light-section method.

[0009] In addition to the accuracy of each element required for the optical lever method, there are many other parameters that need to be calibrated when using the optical lever method, such as the angle of incidence of the linear light emitted from the lighting device onto the object to be measured, the projection position of the reflected light image on the screen, and the distance between the lighting device and the inspection position of the object to be measured (the position on the surface of the object to which the linear light is emitted from the lighting device).Furthermore, among these parameters, there are many that are difficult to adjust individually, as adjusting one parameter will affect other parameters.

[0010] Many of the parameters related to the calibration of the optical lever method are geometrically determined values, such as the distance between each element and the angle at which each element is arranged, so it should be possible to obtain the design values ​​through desk calculations. However, in reality, errors from the design values ​​occur due to unintended misalignment of each element or mechanical errors inherent in each element, and the surface shape may not be measured with the expected accuracy.

[0011] Patent Documents 1 and 2 disclose a shape measuring device that measures the surface shape of a measurement target using the optical lever method, but do not disclose a method for appropriately calibrating a large number of parameters in the optical lever method. As a result, when calibrating various parameters in a shape measuring device that uses the optical lever method, trial and error must be relied upon, and the burden of calibration is extremely large.

[0012] Therefore, rather than determining each of the numerous parameters related to the optical lever method individually, it was necessary to determine them based on a set procedure within a range that would not impair actual measurement accuracy, and to measure the surface shape of the object to be measured with high accuracy.

[0013] The present invention has been made in view of the above-mentioned problems, and has an object to provide a method for calibrating a shape measuring device that can measure the surface shape of a measurement object with high accuracy. [Means for solving the problem]

[0014] A calibration method for a shape measuring device according to the present invention is a method for calibrating a shape measuring device that measures the surface shape of a measurement object transported in a transport direction at an inspection position extending in a width direction perpendicular to the transport direction, and uses a shape measuring device that includes: an illumination device that irradiates linear light extending in the width direction perpendicular to the transport direction toward the inspection position; a screen onto which a reflected light image of the linear light reflected from the surface of the measurement object is projected; an imaging device that images the screen onto which the reflected light image is projected and generates a captured image; and a calculation processing device that measures the surface shape of the measurement object based on the captured image, and the angle of the illumination device relative to the conveying direction as viewed from the normal direction of the object to be measured, based on the linear light and the marker; and the calibration plate removal step of removing the calibration plate from the inspection position. [Effects of the Invention]

[0015] According to the present invention, calibration of the numerous parameters required to measure the surface shape of a measurement object with high accuracy can be performed based on a set procedure within a range that does not impair actual measurement accuracy, thereby enabling the surface shape of the measurement object to be measured with high accuracy. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic diagram showing a configuration when a method for calibrating an illumination device according to an embodiment of the present invention is carried out. [Figure 2] 1 is a block diagram showing the structure of a processing device according to an embodiment of the present invention; [Figure 3]10 is a flowchart illustrating processing in a calibration method for an illumination device according to the present embodiment. [Figure 4] 1 is a diagram showing a configuration of a shape measuring device according to an embodiment of the present invention. [Figure 5] 1 is a diagram showing the configuration of a shape measuring instrument according to an embodiment of the present invention when viewed from the extending direction of linear light. [Figure 6] 1 is a diagram showing the configuration of a shape measuring instrument according to an embodiment of the present invention when viewed from the normal direction of an object to be measured. [Figure 7] 1A and 1B are diagrams showing an example of a captured image generated by an imaging device according to the present invention. [Figure 8] 1A and 1B are diagrams illustrating the configuration of a calibration plate according to the present invention. [Figure 9] 10 is a flowchart for explaining processing in a method for calibrating a form measuring device according to the present embodiment. [Figure 10] 10A and 10B are diagrams for explaining a method of placing a calibration plate in the shape measuring instrument according to the present embodiment. [Figure 11] 10A and 10B are diagrams for explaining the process of adjusting the angle of the illumination device when viewed from the normal direction of the object to be measured in this embodiment so that the extending direction of the linear light is parallel to the marker drawn on the calibration plate. [Figure 12] 10A and 10B are diagrams for explaining a process for adjusting the position of the illumination device in the transport direction when viewed from the normal direction of the object to be measured in this embodiment so that linear light overlaps with a marker drawn on the calibration plate. [Figure 13] 10 shows a graph recording the change in the position of the light image in the second direction when the distance from the lighting device to the test surface in the first direction is changed in this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] The method for calibrating a shape measuring device according to this embodiment will be described in detail below with reference to the accompanying drawings.

[0018] <How to calibrate lighting equipment> First, the principle of the method for calibrating the illumination device installed in the shape measurement instrument according to this embodiment will be described below. If the optical axis or light emission position of the illumination device deviates from the ideal optical axis or emission position that should be in the design, the illumination device will be difficult to use when used alone as a shape measurement instrument. Furthermore, if the illumination device is incorporated into a shape measurement instrument that measures the surface shape of a measurement target using the optical lever method, problems will arise such as an inability to obtain the intended measurement accuracy. Therefore, it is extremely important to calibrate the light emission position and optical axis of the illumination device before using the illumination device.

[0019] Therefore, in view of the above problem, in the method for calibrating a form measuring apparatus according to this embodiment, it is desirable to calibrate the optical axis and emission position of the illumination device in advance to an optimal state.

[0020] The configuration used when implementing the method for calibrating an illumination device according to this embodiment will be described with reference to Fig. 1. Fig. 1 shows the configuration used when implementing the method for calibrating an illumination device according to this embodiment. The method for calibrating an illumination device according to this embodiment uses an illumination device 510, an imaging device 520, a processing device 530, and a test surface 560.

[0021] Note that, in the calibration method for the lighting device 510 according to the present embodiment, a case will be described in which the image capturing device 520 and the arithmetic processing device 530 are used to calculate the deviation amount of the light emission position and the optical axis of the lighting device 510, but the present invention is not limited to this. For example, as another calibration method for the lighting device 510, without using the image capturing device 520 and the arithmetic processing device 530, a calibration operator may himself measure, record, or otherwise perform the processes executed by the image capturing device 520 and the arithmetic processing device 530, and calculate the deviation amount of the light emission position and the optical axis of the lighting device 510.

[0022] The illumination device 510 is an illumination device having a light emitting function, which is incorporated into a shape measuring device that uses the optical lever method. The illumination device 510 has an optical system such as a light source and a lens inside, and irradiates light from an emission position on a lens (not shown) provided on the front surface of the illumination device 510 to the outside of the housing that constitutes the illumination device 510. The light source and optical system provided in the illumination device 510 can be any known light source and optical system that can be used in appropriate combination.

[0023] In consideration of the design of the illumination device 510, the illumination device 510 is expected to irradiate light in a certain direction from a predetermined emission position. This direction is the direction of the ideal designed optical axis of the illumination device 510, and the optical axis designed for this illumination device 510 will be referred to as the designed optical axis IL hereinafter. Furthermore, due to manufacturing errors of the illumination device 510, deterioration over time, etc., it is possible that the emission position on the lens from which light is actually emitted (irradiated) from the illumination device 510 deviates from the designed emission position, or that the direction of the optical axis of actual light irradiated from the illumination device 510 deviates from the designed optical axis IL. This non-ideal optical axis deviated from the designed optical axis IL will be referred to as the real optical axis (or actual optical axis) RIL hereinafter.

[0024] The test surface 560 is a calibration plane (e.g., a flat plate) used in the calibration method for the illumination device 510 according to this embodiment. As described below, the test surface 560 is illuminated by light emitted from the illumination device 510, and the surface illuminated by the light is substantially flat. The shape of the surfaces of the test surface 560 other than the surface illuminated by the light from the illumination device 510 is not particularly limited, as long as the position illuminated by the light from the illumination device 510 can be identified. If the roughness of the test surface 560 is too low, the specular reflection property increases, and the optical image appearing on the test surface 560 due to the light irradiated onto the test surface 560 from the illumination device 510 becomes invisible. Furthermore, if the roughness of the test surface 560 is too high, the shape of the optical image appearing on the test surface 560 becomes blurred, making it difficult to identify the position of the optical image on the test surface 560. Therefore, the test surface 560 is preferably formed from a material with a certain degree of roughness, but the type of material itself is not limited.

[0025] The imaging device 520 is a camera that captures an optical image that appears on the test surface 560 due to light irradiated onto the test surface 560 from the lighting device 510. For example, an area camera such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) is used as the imaging device 520. The imaging device 520 uses the surface of the test surface 560 that is illuminated by light as its imaging field of view, captures the optical image on the test surface 560, and generates a captured image. The generated captured image is output to the arithmetic processing device 530.

[0026] The arithmetic processing device 530 calculates the amount of deviation of the actual optical axis RIL from the design optical axis IL of the lighting device 510. The arithmetic processing device 530 is configured as a computer device having a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), etc. FIG. 2 shows the structure of the arithmetic processing device 530 according to this embodiment. As shown in FIG. 2, the arithmetic processing device 530 includes an image acquisition unit 531, a distance acquisition unit 532, and a deviation amount calculation unit 533. The arithmetic processing device 530 can function as a calibration device including the image acquisition unit 531, the distance acquisition unit 532, and the deviation amount calculation unit 533 by reading and developing a readable lighting device calibration program.

[0027] The image acquisition unit 531 acquires the captured image generated by the imaging device 520. In this case, the image acquisition unit 531 acquires the captured image generated by the imaging device 520 in real time, but may also acquire a captured image generated by the imaging device 520 in the past.

[0028] When an image is captured by the imaging device 520, the distance acquisition unit 532 acquires the value of the distance between the illumination device 510 and the test surface 560 as distance information. The distance between the illumination device 510 and the test surface 560 is, for example, the distance between the light emission position of the illumination device 510 and the position of the test surface 560 along the normal direction of the surface on which the light strikes the test surface 560. The distance value acquired by the distance acquisition unit 532 may be measured using, for example, a laser measuring device or the like, or may be measured visually by a calibration worker using a measurable ruler or the like. The distance value that is the measurement result is input to the distance acquisition unit 532 as distance information.

[0029] The deviation amount calculation unit 533 calculates the deviation amount between the design optical axis IL of the illumination device 510 and the actual optical axis RIL based on a plurality of captured images obtained by capturing an optical image on the test surface 560 by the imaging device 520 for each distance while changing the distance between the illumination device 510 and the test surface 560 along the normal direction of the test surface 560. As will be described in detail later, the deviation amount calculation unit 533 calculates the deviation amount between the design optical axis IL and the actual optical axis RIL based on the relationship between the distance (distance information) between the illumination device 510 and the test surface 560 acquired by the distance acquisition unit 532 and the captured images acquired for each distance.

[0030] Next, the processing in the method for calibrating an illumination device according to this embodiment will be described with reference to Fig. 1 to Fig. 3. Fig. 3 shows a flowchart for explaining the processing in the method for calibrating an illumination device according to this embodiment.

[0031] (Step S501) When the calibration method for the illumination device 510 according to this embodiment is started, processing of step S501 is performed. In step S501, the illumination device 510 and the test surface 560 are arranged opposite to each other so that the designed optical axis IL of the illumination device 510 and the normal direction of the test surface 560 are the same direction (arrangement step).

[0032] In this case, the test surface 560 has a surface parallel to a direction (second direction) perpendicular to the direction (first direction) of the designed optical axis IL of the illumination device 510. The first direction is an arbitrary direction selected from directions that are convenient for observing the optical axis of the illumination device 510 when calibrating the illumination device 510, and the second direction is a direction perpendicular to the first direction in the plane direction of the test surface 560.

[0033] 1, assume that the illumination device 510 is configured in a housing with a flat bottom surface and is designed so that the designed optical axis IL of the illumination device 510 is oriented in a direction parallel to the bottom surface of the housing. Also, the origin O is the emission position, which is the position on the lens where light is emitted from the illumination device 510, and the p-axis is taken as a direction passing through the origin O and parallel to the first direction (the direction of the designed optical axis IL of the illumination device 510), and the q-axis is taken as a second direction passing through the origin O and perpendicular to the first direction (the surface direction of the test surface 560).

[0034] Here, for example, when illumination device 510 removed from a shape measuring device described later is placed on reference plane 561, which is a plane horizontal to the reference p-axis, and light is irradiated toward test surface 560, the design of illumination device 510 irradiates light parallel to the first direction from origin O and reaches point A on test surface 560, and the designed optical axis IL is a straight line connecting origin O and point A. Furthermore, if the light emission position or irradiation direction (direction of the actual optical axis) of illumination device 510 deviates from the design, light is emitted from point C on the lens of illumination device 510, which is displaced from origin O, rather than from origin O, and reaches point B on test surface 560, and the actual optical axis RIL is a straight line connecting point C and point B.

[0035] For simplicity of explanation, the following description will be given taking as an example a case where the first direction is the horizontal direction and the second direction is the height direction, but the present invention is not limited to this case as long as the first direction and the second direction are in a positional relationship that is perpendicular to each other. Furthermore, the designed optical axis IL does not depend on the shape of the housing of the lighting device 510, but depends on the direction in which the designed light of the lighting device 510 is irradiated.

[0036] In step S501, once lighting device 510 and test surface 560 are positioned as described above, the process proceeds to step S503.

[0037] (Step S503) In step S503, the distance from the illumination device 510 to the test surface 560 is changed along the normal direction of the test surface 560, and the optical image that appears on the test surface 560 according to the distance due to the light emitted from the illumination device 510 is measured. That is, assuming that the measurement index is i, the distance d from the illumination device 510 to the test surface 560 is i While changing the position y of the light image that appears on the test surface 560 by the light irradiated from the illumination device 510 along a first direction (for example, the horizontal direction), i b (For example, the position in the height direction as the second direction) is measured (optical image measuring step).

[0038] The light emitted from the lighting device 510 creates a light image on the test surface 560, so it is easy to observe which position on the test surface 560 the emitted light reaches.

[0039] If light is irradiated from the lighting device 510 along a design optical axis IL (e.g., the horizontal direction), even if the distance between the lighting device 510 and the test surface 560 is changed, the position of the light image generated by the light irradiating the test surface 560 does not change in the second direction (here, the height direction) because the test surface 560 is perpendicular to the direction of the light. On the other hand, if the actual optical axis RIL of the lighting device 510 deviates from the design optical axis IL, the position of the light image generated by the light irradiating the test surface 560 will change in the second direction (height direction) as the distance between the lighting device 510 and the test surface 560 is changed in the first direction. Therefore, by measuring the change in the second direction of the light image on the test surface 560, it is possible to know to what extent the emission position and irradiation angle of the actual optical axis RIL irradiated from the lighting device 510 deviates from the design optical axis IL.

[0040] Here, the distance d between the lighting device 510 and the test surface 560 is iWhile changing the distance d i along with the value of the position y of the light image on the test surface 560 in the second direction. i b (In the case of Figure 1, measure the height from the origin O).

[0041] In this embodiment, the distance d i The distance acquisition unit 532 acquires the value of i The image acquisition unit 531 acquires a captured image of the light image at each time point, and determines the position y of the light image in the second direction on the test surface 560 based on the position of the light image in the captured image. i b Then, the deviation amount calculation unit 533 obtains the distance d i The captured image in which the light image is captured for each time is analyzed, and the position y of the light image on the test surface 560 in the second direction in the captured image is calculated. i b distance d i As mentioned above, these processes do not necessarily have to be performed on the arithmetic processing device 530, and the calibration technician may manually measure and record the data. When an appropriate number of measurements of data have been obtained, the process proceeds to step S505.

[0042] (Step S505) In step S505, the distance d from the lighting device 510 to the test surface 560 is i and distance d i Based on the position of the light image appearing on the test surface 560 for each test point, the amount of deviation of the light image from the designed optical axis IL of the illumination device 510 is calculated as the distance d between the illumination device 510 and the test surface 560. i For example, the distance d from the lighting device 510 to the test surface 560 in the first direction is calculated according to i and the position y of the light image in the second direction i bBy approximating the relationship between the above using the least squares method, the tilt deviation of the illumination device 510 corresponding to the angle difference θ between the actual optical axis RIL of the illumination device 510 and the designed optical axis IL, and the displacement deviation of the illumination device 510 corresponding to the positional difference in the second direction between the irradiation start position (actual emission position) of the actual optical axis RIL of the illumination device 510 and the irradiation start position (design emission position) of the designed optical axis IL are calculated as deviation amounts (deviation amount calculation step).

[0043] In the example of Figure 1 described above, the positional deviation between the origin O and point C in the second direction corresponds to the displacement deviation, and the angle θ between the designed optical axis IL and the actual optical axis RIL corresponds to the tilt deviation.

[0044] More specifically, as shown in FIG. 1 , an index i corresponds to the number of measurements performed while changing the distance from the illumination device 510 to the test surface 560 in the first direction, and the distance d i The light irradiated along the designed optical axis IL travels from the origin O(0,0) to a point A(d i However, the light irradiated along the actual optical axis RIL is projected vertically from the origin O at y a The point C(0, y a ) and at an angle shifted by an angle θ from the designed optical axis IL, point B (d i , y i b ), the relationship of the following formula (1) is obtained from the geometric positional relationship between the illumination device 510 and the test surface 560.

number

[0045] Distance d i and the position y of the light image on the test surface 560 in the second direction. i bThe value of can be found by actually measuring the position of the test surface 560 and the position of the optical image on the test surface 560 in step S503.

[0046] Therefore, for example, by changing the position of test surface 560 along the first direction, distance d i Vary the distance d i and the position y of the light image on the test surface 560 in the second direction. i b By finding the value of , the unknown displacement y a and the inclination deviation θ can be calculated. a The least squares method is preferably used to calculate the inclination deviation θ. In this case, the displacement deviation y a The tilt deviation θ can be calculated using the following equations (2) and (3), where n is the total number of data obtained by actual measurements.

number

number

[0047] In addition, the displacement deviation y a is the distance deviation (offset) in the second direction between the light emission position on the actual optical axis RIL of the illumination device 510 and the light emission position on the designed optical axis IL. Also, the tilt deviation θ is the angle deviation corresponding to the difference in direction between the actual optical axis RIL of the illumination device 510 and the designed optical axis IL.

[0048] Thus, the displacement y a If we know the inclination error θ, we can calculate the displacement error y a and the tilt deviation θ, the illumination device 510 is calibrated (calibration step), and the method for calibrating the illumination device 510 according to this embodiment is completed.

[0049] As described above, according to this embodiment, the displacement deviation y aSince the tilt deviation θ can be known, when using the lighting device 510, the displacement deviation y a Since the illumination device 510 can be used after tilting or providing an offset according to the tilt deviation θ, it becomes possible to irradiate light from an accurate position in an accurate direction regardless of errors inherent in the illumination device 510. Therefore, when the illumination device 510 is used in a shape measurement device that uses the optical lever method, it is possible to prevent problems caused by errors in the illumination device 510.

[0050] As described above, in this embodiment, the displacement deviation y a Since the calibration of the tilt deviation θ can be performed according to a set procedure within a range that does not impair the actual measurement accuracy, the surface shape of the measurement object can be measured with high accuracy.

[0051] As described above, in this embodiment, the least squares method is used to calculate the deviation amount, and the displacement deviation y a In the above example, the tilt deviation θ was calculated using the equation (1), but the present invention is not limited to this. For example, when calculating the deviation amount, a look-up table (LUT) may be created in which the distance between the illumination device 510 and the test surface 560 corresponds to the deviation amount acquired at that time, and the illumination device 510 may be calibrated by referring to the corresponding deviation amount based on the distance between the illumination device 510 and the test surface 560 along the designed optical axis IL. If the LUT does not contain a deviation amount that matches the placement position of the illumination device 510, the deviation amounts for distances before and after the distance at the placement position on the LUT may be referenced, and the deviation amount may be calculated by proportional allocation.

[0052] <Method for calibrating a shape measurement device> Next, a calibration method for a shape measuring device capable of measuring the surface shape of a measurement target object using the optical lever method, using an illumination device calibrated by the above-described illumination device calibration method, will be described below. The calibration method for a shape measuring device using the optical lever method according to this embodiment will be described in detail below with reference to the accompanying drawings. Note that in this specification and drawings, components having substantially the same functional configuration as the above-described components will be designated by the same reference numerals, and redundant description may be omitted.

[0053] Here, in a measurement method using the optical lever method, in which a linear light is irradiated from an illumination device onto the surface of the object to be measured at a predetermined angle of incidence, the light reflected from the surface of the object to be measured is projected onto a screen, and the surface shape of the object to be measured based on the reflected light image on the screen, even if each element that makes up the shape measurement device, such as the illumination device and screen, is arranged according to design, in reality there is a risk that there will be unintended slight deviations in the position or angle of each element, or that each element itself will contain errors.

[0054] Furthermore, if the calibration of a shape measurement device using the optical lever method is insufficient (poor accuracy), when measuring the surface shape of an object through a reflected light image (bright line) projected onto a screen, not only the displacement corresponding to the surface shape but also the error due to insufficient calibration are magnified and displayed, making it difficult to perform highly accurate measurements. Furthermore, since shape measurement devices using the optical lever method have a wide range of parameters that need to be calibrated, calibration is complicated, and adjusting one parameter can affect other parameters, causing problems such as changes in those parameters. Therefore, it has been desired to specify a procedure for performing calibration.

[0055] Therefore, in view of the above problems, the calibration method for a shape measurement device using the optical lever method according to this embodiment provides a method that can calibrate a large number of parameters related to a measurement method using the optical lever method based on a certain procedure, within a range that does not impair actual measurement accuracy.

[0056] The configuration used in the calibration method for a form measuring device according to this embodiment will be described with reference to Figs. 4 to 6. Fig. 4 shows the configuration of a form measuring device 100 according to this embodiment. Fig. 5 shows the configuration of the form measuring device 100 according to this embodiment when viewed from the direction in which linear light extends. Fig. 6 shows the configuration of the form measuring device 100 according to this embodiment when viewed from the normal direction of the surface of the object 1 to be measured.

[0057] The shape measuring device 100 is a device that detects the surface shape of the object 1 moving in the conveyance direction at a predetermined inspection position LB that extends along the width direction of the surface of the object 1, perpendicular to the conveyance direction, and any known shape measuring device that uses the optical lever method can be used as long as it does not contradict the following description. The shape measuring device 100 that uses the optical lever method has an illumination device 10, a screen 20, an imaging device 30, and a processing unit 40. Note that the illumination device 10 has the same configuration as the above-mentioned illumination device 510, and it is desirable that the actual optical axis be calibrated according to the calibration method of the illumination device 510 described above.

[0058] The measurement object 1 is an object to be measured (inspected) when the shape measuring device 100 measures the surface shape, such as defects such as irregularities and unevenness of the roughness, present on the surface.

[0059] The object to be measured 1 can be, for example, various steel plates such as flat thick or thin plates, but is not limited to these.Various objects can be used as the object to be measured as long as the surface shape can be measured using a measurement method that utilizes the optical lever method.

[0060] The measurement object 1 is transported relative to the shape measuring device 100 along a predetermined transport direction by a transport device (not shown). That is, the measurement object 1 may move while the shape measuring device 100 is fixed, or the measurement object 1 may move while the shape measuring device 100 is fixed, or both the measurement object 1 and the shape measuring device 100 may move. When the measurement object 1 is transported, it may be transported with tension applied to both ends of the measurement object 1 to minimize vibration, deflection, and the like.

[0061] The lighting device 10 is an illumination device that has the function of irradiating linear light 15 that extends in the width direction perpendicular to the conveying direction in the in-plane direction of the surface of the object to be measured 1 toward the object to be measured 1 or the position where the object to be measured 1 should be, more specifically toward the inspection position LB described below.

[0062] The lighting device 10 has a light source and an optical system such as a lens inside a housing, generates linear light 15, which is a linear light that extends long in a width direction perpendicular to the conveyance direction of the measurement object 1 and has a narrow width in the conveyance direction, and irradiates the linear light 15 toward the surface of the measurement object 1. The linear light 15 extends so as to cover substantially the entire width of the measurement object 1. The light source and optical system provided in the lighting device 10 can be any known light source and optical system that can be appropriately combined.

[0063] The central wavelength of the light emitted from the illumination device 10 is designed taking into consideration the specular reflectivity of the measurement object 1 at the inspection position LB and the wavelength sensitivity characteristics of the imaging device 30. Due to the nature of light, the longer the wavelength of light, the more easily it is specularly reflected from the surface of the measurement object 1. This increases the brightness of the reflected light image (bright line) RI formed on the screen 20, and increases the S / N ratio. On the other hand, if the central wavelength of the illumination device 10 exceeds the wavelength range that can be captured by the imaging device 30 (described later), the brightness of the reflected light image RI in the captured image PH decreases, and the S / N ratio decreases. Therefore, the central wavelength of the illumination device 10 is designed with a lower limit wavelength that takes into consideration the specular reflectivity of the measurement object 1 and an upper limit wavelength that takes into consideration the wavelength sensitivity characteristics of the imaging device 30.

[0064] The spectral width of the light emitted from the illumination device 10 is designed taking into consideration the speckle noise observed in the reflected light image RI. If light with a narrow spectral width, such as laser light, is used in the shape measurement device 100, speckle noise in the form of a fine, high-contrast spotted pattern will appear in the reflected light image RI in the captured image PH, reducing the S / N ratio. For this reason, the illumination device 10 uses light with a wide spectral width and low coherence.

[0065] Linear light 15 emitted from lighting device 10 is emitted toward the surface of object 1 in the range indicated by dashed line 15a in Figures 4 to 6, and strikes the surface of object 1 in a line (linear light 15) at inspection position LB, which will be described later, and is reflected. The reflected light of linear light 15 reflected at inspection position LB on the surface of object 1 passes through the range indicated by dashed line 15b in Figures 4 to 6, is irradiated onto screen 20, which will be described later, and is projected, appearing as a reflected light image RI.

[0066] As is clear from the principle of the measurement method using the light-section method, the linear light 15 is displaced depending on the surface shape at the position on the surface of the object 1 to be measured where the linear light 15 is irradiated, and therefore the surface shape at the position on the object 1 to be measured where the linear light 15 is irradiated can be measured based on the displacement of the linear light 15. In other words, the shape measuring device 100 using the optical lever method measures the surface shape of the object 1 to be measured at the position on the surface of the object 1 to be measured where the linear light 15 is irradiated, and therefore the position on the surface of the object 1 to be measured where the linear light 15 is irradiated (and, when the object 1 to be measured does not exist, a position corresponding to the position on the surface of the object 1 to be irradiated where the linear light 15 is irradiated) becomes the position used when measuring the surface shape.

[0067] Therefore, the position on the surface of the object 1 to be measured where the linear light 15 is irradiated (and the position corresponding to the position on the surface of the object 1 to be irradiated where the linear light 15 is irradiated when the object 1 to be measured is not present, etc.) will be referred to as the inspection position LB used when the shape measuring device 100 measures defects. The inspection position LB is a linear position (or area) extending in the width direction perpendicular to the conveying direction.

[0068] In order to improve the accuracy of measuring the surface shape, it is preferable that the lighting device 10 is configured so that the linear light 15 in the most focused state (i.e., the state in which the line width of the linear light 15 is narrowest) is incident on the surface of the object to be measured 1 at the inspection position LB using the optical system inside the housing.

[0069] As shown in Fig. 4, the origin O1 is the center position of the linear light 15 irradiated onto the measurement object 1 by the illumination device 10 in the extension direction on the surface of the measurement object 1, the y-axis is the axis passing through the origin O1 and heading in the transport direction of the measurement object 1, the x-axis is the axis passing through the origin O1 and heading in the width direction perpendicular to the transport direction of the measurement object 1, and the z-axis is the axis passing through the origin O1 and heading in the normal direction to the surface of the measurement object 1. In this case, as shown in Fig. 5, the linear light 15 irradiated from the illumination device 10 is irradiated with the surface of the measurement object 1 at an incident angle θ1 defined by the angle it makes with the z-axis when viewed from the x-axis direction. Then, the linear light 15 is reflected at an inspection position LB on the surface of the measurement object 1 at a reflection angle θ1 defined by the angle it makes with the z-axis when viewed from the x-axis direction, and the reflected light heads toward the screen 20 and is projected as a reflected light image RI.

[0070] The illumination device 10 is disposed so as to irradiate linear light 15 in the transport direction of the object 1 as viewed from the z-axis direction, but when the shape measuring device 100 is initially installed (before calibration), the arrangement of the illumination device 10 (i.e., the irradiation direction of the linear light irradiated from the illumination device 10 relative to the transport direction as viewed from the normal direction of the object 1) may be unintentionally shifted as shown in Fig. 6. In this case, the illumination device 10 may irradiate linear light 15 in the direction of a two-dot chain line 10a that has an angle Φ (hereinafter also referred to as the swing angle Φ) with respect to the transport direction as viewed from the z-axis direction.

[0071] Furthermore, in consideration of the design of the illumination device 10 itself, it is expected that the illumination device 10 will emit linear light 15 in a certain direction from a predetermined emission position, but due to manufacturing errors or deterioration over time of the illumination device 10, the position on the lens from which the linear light 15 is emitted from the illumination device 10 may deviate from the designed emission position, or the irradiation direction of the linear light 15 emitted from the illumination device 10 may deviate from the ideal direction. Therefore, when using the illumination device 10, it may be necessary to calibrate the illumination device 10 itself as needed.

[0072] The lighting device 10 is held by a support (not shown), and the position of the lighting device 10 can be changed along the transport direction by moving the support. Preferably, the lighting device 10 is held by a mechanism that can independently change the holding angle when viewed from the x-axis direction and the holding angle when viewed from the z-axis direction.

[0073] The screen 20 is an object that functions as a projection film onto which the linear light 15 reflected by the surface of the measurement object 1 is projected as a reflected light image RI. The screen 20 is disposed at a position a predetermined distance from the inspection position LB, facing the illumination device 10, for example, so that the surface of the measurement object 1 and the surface of the screen 20 are perpendicular to each other. More specifically, the screen 20 is disposed so that the normal vector of the projection surface of the screen 20 does not have an x-component (the value of the x-component is zero) in the xyz coordinate system shown in Fig. 4.

[0074] The screen 20 is large enough to capture the entire (total length, total width) of the reflected light image RI generated on the screen 20 when the linear light 15 emitted from the illumination device 10 is reflected at the inspection position LB on the surface of the measurement target 1, making it possible to determine where on the screen 20 the reflected light image RI hits. If the roughness of the screen 20 is too low, the specular reflection property becomes too strong, making the reflected light image RI on the screen 20 invisible. On the other hand, if the roughness is too high, the shape of the reflected light image RI becomes blurred, making it difficult to identify its position. For this reason, it is preferable that the screen 20 be formed from a material with a certain degree of roughness, but the type of material itself is not limited.

[0075] The greater the distance between the inspection position LB and the screen 20, the more magnified the surface shape of the object 1 at the inspection position LB can be detected, but the greater the attenuation of the brightness of the linear light 15 becomes, and the worse the S / N ratio becomes. Therefore, it is preferable to actually measure the distance from the inspection position LB to the screen 20 in advance and to understand the average distance to some extent.

[0076] The imaging device 30 functions as a camera that captures an image of the screen 20 onto which the reflected light of the linear light 15 is projected as a reflected light image RI, and generates a captured image. That is, as shown by the dashed-dotted lines in Figures 4 to 6, the imaging device 30 captures an area on the screen 20 as an imaging field of view that includes at least all of the reflected light images RI projected on the surface of the screen 20, thereby generating a captured image PH. Therefore, the reflected light images RI projected onto the screen 20 appear in the captured image PH.

[0077] In this embodiment, when calibrating the actual optical axis of the illumination device 10 according to the calibration method of the illumination device 510, the imaging device 30 may be applied as the imaging device 520 shown in FIG. 1, and the imaging device 520 used when calibrating the illumination device 10 may be provided separately from the imaging device 30 of the shape measurement device 100.

[0078] The captured image PH is preferably a two-dimensional captured image made up of two-dimensional images, and the imaging device 30 is preferably an area camera that generates a two-dimensional captured image. The imaging device 30 may be a black-and-white camera or a color camera, and the captured image PH may be a black-and-white image or a color image.

[0079] The arithmetic processing device 40 performs data processing and calculations for measuring the surface shape of the measurement object 1 based on the captured image PH captured by the imaging device 30. The arithmetic processing device 40 is realized by, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a communication device, etc. As shown in FIG. 4 (not shown in FIGS. 5 and 6), the arithmetic processing device 40 is connected to the imaging device 30 via a wired or wireless connection, and can acquire the captured image PH generated by the imaging device 30.

[0080] Based on the acquired captured image PH, the calculation processing device 40 can use a measurement method utilizing the well-known optical lever method to measure the surface shape at the inspection position LB on the surface of the object to be measured 1 from the displacement of the linear light 15 captured in the captured image PH.

[0081] In this embodiment, when the actual optical axis of the illumination device 10 is calibrated according to the calibration method of the illumination device 510, the arithmetic processing device 40 may be configured to include the image acquisition unit 531, the distance acquisition unit 532, and the deviation amount calculation unit 533 shown in FIG. 2. Furthermore, the arithmetic processing device 530 that calibrates the illumination device 10 may be provided separately from the arithmetic processing device 40.

[0082] 7 shows an example of a captured image PH generated by the imaging device 30 according to the present invention. When unevenness exists on the surface of the measurement object 1 at the inspection position LB (FIG. 6), a concave or convex displacement CD occurs in the reflected light image RI captured in the captured image PH, with the reflected light image RI when the surface of the measurement object 1 at the inspection position LB is flat as a reference line.

[0083] The displacement CD of this reflected light image RI corresponds to the unevenness of the surface of the measurement object 1, and therefore the surface shape of the measurement object 1 at the inspection position LB can be determined by performing calculations based on the displacement CD in the calculation processing device 40. Furthermore, as the measurement object 1 is transported and passes through the inspection position LB, the position on the surface of the measurement object 1 at the inspection position LB changes, and the surface shape can be measured at each position along the transport direction of the surface of the measurement object 1.

[0084] As will be described later, the shape measuring instrument 100 uses a calibration plate 50 when calibrating itself.

[0085] The calibration plate 50 is, for example, a flat plate with linear markers CL drawn on its surface, as shown in FIG. 8, and as will be described later, the calibration plate 50 is used to adjust the swivel angle Φ of the lighting device 10 and the position of the lighting device 10.

[0086] The marker CL drawn on the calibration plate 50 may be printed on the calibration plate 50, may be attached to the calibration plate 50 with a sticker or the like, or may be formed by forming a shallow depression or the like on the surface of the calibration plate 50, and the marker CL itself may be a solid line or a dotted line, etc.

[0087] When calibrating the shape measuring device 100, the inspection position LB and the marker CL are compared, as will be described later. Therefore, it is preferable that the calibration plate 50 has a size and shape that allows it to be accurately positioned at the inspection position LB and that allows the inspection position LB and the marker CL to be compared.

[0088] The calibration plate 50 has sufficient rigidity to prevent bending even when placed at any position. If the roughness of the calibration plate 50 is too low, the specular reflection property will be high, and the linear light 15 will not be visible at the inspection position LB, which may make it impossible to compare the marker CL with the linear light 15. Furthermore, if the roughness is too high, the shape of the linear light 15 will be blurred, making it difficult to identify its position. For this reason, the calibration plate 50 is preferably made of a material with a certain degree of roughness, but the type of material itself is not limited.

[0089] Next, processing in the calibration method for the form measuring device 100 according to this embodiment will be described with reference to Fig. 9. Fig. 9 shows a flowchart for explaining processing in the calibration method for the form measuring device 100 according to this embodiment.

[0090] (Step S101) When the calibration method for the shape measuring device 100 according to this embodiment is started, processing of step S101 is performed. In step S101, the actual optical axis of the illumination device 10 is calibrated relative to the designed optical axis of the illumination device 10 in a direction perpendicular to both the direction along the designed optical axis of the illumination device 10 and the direction in which the linear light 15 extends, thereby calibrating the illumination device 10 itself (illumination device calibration step).

[0091] As described above, due to manufacturing errors of the illumination device 10 itself, deterioration over time, etc., the emission position of the linear light 15 emitted from the illumination device 10 and the actual direction of the optical axis may deviate from the ideal emission position and direction of the optical axis determined in the design of the illumination device 10. Therefore, in step S101, the emission position of the linear light 15 emitted from the illumination device 10 and the actual direction of the optical axis are calibrated.

[0092] As a method for calibrating the lighting device 10 itself, a known calibration method for a lighting device can be used as appropriate. However, it is desirable to use, for example, the calibration method for the lighting device 510 according to this embodiment. In this case, in the lighting device calibration step, the lighting device 10 is calibrated according to the flowchart shown in FIG. 3. Specifically, for example, using the calibration method for the lighting device 510 according to this embodiment, the amount of deviation of the actual linear light 15 from the designed optical axis of the lighting device 10 in a direction perpendicular to both the direction along the designed optical axis of the lighting device 10 and the extension direction of the linear light 15 (i.e., the second direction on the test surface 560 (FIG. 1)) is calibrated. When the calibration of the lighting device 10 in step S101 is completed, the process proceeds to step S103.

[0093] (Step S103) In step S103, the position of the illumination device 10 calibrated in step S101 and the angle at which the linear light 15 is irradiated onto the surface of the measurement object 1 as viewed from the extending direction of the linear light 15 are adjusted to a geometric arrangement in which the reflected light image RI is projected at a predetermined position on the screen 10. That is, the depression angle of the illumination device 10 with respect to the measurement object 1 as viewed from the extending direction of the linear light 15 (the angle of the optical axis of the illumination device 10 as viewed from the extending direction of the linear light 15) is adjusted to a geometric arrangement in which the reflected light image RI of the linear light 15 is projected at a predetermined position on the screen 20 (for example, the center of the screen 20) (incident side temporary adjustment step).

[0094] In a measurement method using the optical lever method, the surface shape of the surface of the measurement object 1 at the inspection position LB is measured based on the displacement of the reflected light image RI projected onto the screen 20, so even if there is some displacement depending on the degree of the surface shape, the reflected light image RI needs to be projected onto the screen 20 with a positional margin so that it does not deviate from the inside of the screen 20 (and the imaging field of the imaging device 30). Therefore, in order to ensure as much margin as possible, the illumination device 10 is adjusted so that the reflected light image RI is positioned approximately in the center of the screen 20.

[0095] Since the distance between the screen 20 and the inspection position LB is constant, if the height at which the illumination device 10 is placed is determined arbitrarily, the position of the illumination device 10 and the angle of the illumination device 10 with respect to the inspection position LB can be uniquely determined from the geometric relationship when the reflected light image RI of the linear light 15 is projected onto the center of the screen 20. Therefore, the illumination device 10 is adjusted so that the distance and angle are determined from the geometric relationship.

[0096] However, even if such geometric adjustments are made to place the illumination device 10 in the most correct position and angle possible, in reality, given the accuracy of the shape measuring device 100, there is a potential for deviations that will affect the measurement results, and in many cases the reflected light image RI will not be projected in accordance with the geometric relationship onto the center of the screen 20. However, in step S103, the illumination device 10 is adjusted to match the geometrically determined position and angle, regardless of the actual projection position of the reflected light image RI. Therefore, in step S103, deviations from the arrangement that occur unintentionally during calibration are not taken into consideration. When the adjustment of the lighting device 10 in step S103 is completed, the process proceeds to step S105.

[0097] (Step S105) In step S105, the calibration plate 50, on whose surface a linear marker CL is drawn, is placed so that the marker CL drawn on the calibration plate 50 is aligned with the inspection position LB (calibration plate placement step).

[0098] In step S105, the calibration plate 50 is placed alone, excluding the measurement target 1, so that the inspection position LB and the position of the marker CL overlap.

[0099] 10 is a diagram illustrating a method for placing the calibration plate 50 on the profile measuring apparatus 100 according to this embodiment. In FIG. 10, for the sake of explanation, the measurement object 1 is shown by a dashed line in the location where the measurement object 1 was placed. As shown in FIG. 10, the inspection position LB is a linear area extending in the width direction perpendicular to the transport direction of the measurement object 1, so that the linear marker CL drawn on the calibration plate 50 can be placed so as to coincide with the position of the inspection position LB (so that the straight line of the marker CL is aligned with the extension direction of the inspection position LB). After the calibration plate 50 has been placed in step S105, the process proceeds to step S107.

[0100] (Step S107) In step S107, linear light 15 is emitted using illumination device 10 (illumination step). In step S105, marker CL of calibration plate 50 is positioned so as to overlap inspection position LB. Therefore, when linear light 15 is emitted from illumination device 10, if there is no error in the distance from illumination device 10 to inspection position LB or in the irradiation angle of linear light 15 from illumination device 10, it is expected that linear light 15 emitted from illumination device 10 will be emitted so as to overlap with straight line CL drawn on calibration plate 50. Once irradiation of linear light 15 from illumination device 10 begins in step S107, the process proceeds to step S109.

[0101] (Step S109) In step S109, the angle Φ (swing angle Φ) of the illumination device 10 relative to the transport direction as viewed from the normal direction of the measurement object 1 is adjusted based on the linear light 15 and the marker CL on the calibration plate 50. That is, the swing angle Φ of the illumination device 10 as viewed from the normal direction of the measurement object 1 is adjusted so that the extension direction of the linear light 15 and the extension direction of the marker CL drawn on the calibration plate 50 are parallel (angle adjustment step).

[0102] Figures 11(a) and 11(b) show diagrams for explaining the process of adjusting the swivel angle Φ of the lighting device 10 relative to the conveying direction when viewed from the normal direction of the object to be measured 1 so that the extension direction of the linear light 15 and the extension direction of the marker CL drawn on the calibration plate 50 are parallel.

[0103] As shown by the dotted line 10a in Figure 6, if the lighting device 10 has a swing angle Φ of the actual optical axis of the lighting device 10 relative to the y-axis direction, which is the conveying direction, when viewed from the z-axis direction (i.e., when viewed from the normal direction of the object to be measured 1), the extension direction of the linear light 15 is perpendicular to the swing angle Φ, and therefore the marker CL and the linear light 15 are not parallel, as shown in Figure 11(a).

[0104] Therefore, in step S109, while visually checking the linear light 15 and the marker CL, the position and angle of the lighting device 10 calibrated in step S101 (the angle at which the linear light 15 is irradiated onto the surface of the object to be measured 1 as viewed from the extension direction of the linear light 15) are adjusted, and the swivel angle Φ of the lighting device 10 relative to the y-axis direction when viewed from the z-axis direction is adjusted so that the extension direction of the linear light 15 and the extension direction of the marker CL are parallel, as shown in Figure 11(b). When the adjustment of the swing angle Φ of the lighting device 10 is completed in step S109 so that the extending direction of the linear light 15 and the extending direction of the marker CL are parallel to each other, the process proceeds to step S111.

[0105] (Step S111) In step S111, the position of the illumination device 10 in the transport direction when viewed from the normal direction of the measurement object 1 is adjusted based on the linear light 15 and the marker CL on the calibration plate 50. That is, the position of the illumination device 10 in the transport direction when viewed from the normal direction of the measurement object 1 is adjusted so that the linear light 15 and the marker CL drawn on the calibration plate 50 overlap (position adjustment step).

[0106] Figures 12(a) and 12(b) show diagrams for explaining the process of adjusting the position of the illumination device 10 in the transport direction when viewed from the normal direction of the object to be measured 1 so that the linear light 15 overlaps with the marker CL drawn on the calibration plate 50.

[0107] As shown in Figure 12(a), when viewed from the z-axis direction (viewed from the normal direction of the object to be measured 1), the extension direction of the linear light 15 and the extension direction of the marker CL drawn on the calibration plate 50 are adjusted to be parallel in step S109, but there is a positional deviation in the conveying direction (y-axis direction) between the linear light 15 and the marker CL drawn on the calibration plate 50.

[0108] Therefore, in step S111, while visually checking the linear light 15 and the marker CL, the position of the lighting device 10 is adjusted along the conveying direction while being careful not to change the position and angle of the lighting device 10 calibrated in step S101 (the angle at which the linear light 15 is irradiated onto the surface of the object to be measured 1 as seen from the extension direction of the linear light 15), so that the linear light 15 and the marker CL overlap, as shown in Figure 12(b). When the adjustment is completed in step S111 so that the linear light 15 and the marker CL drawn on the calibration plate 50 overlap, the process proceeds to step S113.

[0109] (Step S113) In step S113, the calibration plate 50 is removed from the inspection position LB (calibration plate removal step). By removing the calibration plate 50 from the inspection position LB of the shape measuring device 100, the object 1 to be measured, the surface shape of which is to be inspected, can be transported toward the shape measuring device 100, and the surface shape of the object 1 can be measured by the shape measuring device 100.

[0110] In this way, once the calibration of the profile measuring device 100 is completed and it becomes possible to measure the surface profile, the method for calibrating the profile measuring device 100 according to this embodiment is completed.

[0111] As described above, according to this embodiment, it becomes possible to calibrate a shape measuring instrument 100 that uses the optical lever method, which has a wide variety of parameters that need to be adjusted and may have parameters that cannot be freely adjusted, based on certain guidelines.

[0112] By performing such calibration, the shape measuring device 100 can be calibrated with minimal trial and error, without randomly changing a large number of parameters through trial and error.

[0113] Furthermore, by performing such calibration, even if the calibration operator believes that he has adjusted each element of the shape measuring device 100, such as the lighting device 10 and the screen 20, to the geometrically correct position and angle, and there are errors in each element that the calibration operator is unable to recognize, the shape measuring device 100 can be calibrated so that errors that cause practical problems do not occur.

[0114] As described above, in the calibration method for the shape measuring device 100 according to this embodiment, the calibration of the numerous parameters required to measure the surface shape of the object to be measured 1 with high accuracy can be performed based on a certain procedure within a range that does not impair the actual measurement accuracy, thereby enabling the surface shape of the object to be measured 1 to be measured with high accuracy.

[0115] <Other embodiments> 9 , light (linear light 15) emitted from the illumination device 10 is incident on the test surface 560 used when calibrating the illumination device 10 in the illumination device calibration step of step S101, as described below. However, as long as the surface on which the light is incident is substantially flat and the position where the light is incident can be identified, the shape of the surfaces of the test surface 560 other than the surface on which the light is incident is not particularly limited. It is preferable to use a material for the test surface 560 that has relatively low light diffusion properties, since this makes it easier to identify the outer edge shape of the light on the test surface 560. Calibration of the illumination device 10 may be performed with the illumination device 10 detached from the shape measurement device 100, or may be performed with the illumination device 10 attached to a predetermined position on the shape measurement device 100.

[0116] In the above-described embodiment, the displacement deviation y a The case where both the displacement deviation y and the tilt deviation θ are calculated as the deviation amount has been described, but the present invention is not limited to this. a Alternatively, only one of the inclination deviation θ and the tilt deviation θ may be calculated as the deviation amount.

[0117] In the above-described embodiment, the displacement deviation, which is the difference between the designed irradiation start position of the lighting device in the in-plane direction of the test surface and the actual irradiation start position of the lighting device, is, for example, a displacement deviation y in the height direction (second direction) perpendicular to the normal direction (first direction) of the test surface 560 in the in-plane direction of the test surface 560. a However, the present invention is not limited to this, and it is also possible to calculate displacement deviation in various second directions, such as the width direction perpendicular to the normal direction of the test surface 560, in the in-plane direction of the test surface 560.

[0118] Furthermore, in the above-described embodiment, the illumination device calibration step for calibrating the actual optical axis of the illumination device based on the deviation between the design optical axis of the illumination device and the actual optical axis of the illumination device in an in-plane direction perpendicular to the direction along the design optical axis of the illumination device is performed by changing the distance from the illumination device 510 to the test surface 560 along the normal direction of the test surface 560, measuring the position of an optical image that appears in the in-plane direction of the test surface 560 by light irradiated from the illumination device 510 for each distance (the in-plane direction perpendicular to the direction along the design optical axis of the illumination device 510), calculating the deviation from the design optical axis, and calibrating the actual optical axis based on the deviation. However, the present invention is not limited to this. For example, various other calibration methods may be applied, such as moving the illumination device 10 so as to change the distance from the measurement object 1 without using the test surface 560, and measuring the position of the optical image projected onto the measurement object 1 in the in-plane direction perpendicular to the direction along the design optical axis of the illumination device 10 to calibrate the actual optical axis.

[0119] In the above-described embodiment, the captured image naturally includes not only the specific form of an image displayed on a display unit such as a monitor, but also data before it is generated as an image on the display unit. [Example]

[0120] FIG. 13 shows the distance d from the illumination device 510 to the test surface 560 in this embodiment. i is changed along the normal direction (first direction) of the test surface 560, and the position y of the light image on the test surface 560 in the second direction is measured for each distance. i and calculate the position y i A graph recording the changes in

[0121] The horizontal axis of FIG. 13 is the distance d from the lighting device 510 to the test surface 560 in the first direction (for example, the horizontal direction). i and the vertical axis represents the position y of the light image on the test surface 560 in the second direction. i is.

[0122] As shown in Figure 13, the distance d i Change 10 patterns (using 10 different i), and calculate the distance d i The position of the light image on the test surface 560 was measured for each test, and 10 plots were obtained.

[0123] The approximation curve obtained by linear approximation using the 10 acquired data points by the least squares method is shown by the black dashed line in FIG.

[0124] From the above equation (2), the inclination error θ is calculated, and from the above equation (3), the displacement error y is calculated. a The calculated tilt error was θ = 2.2° and the displacement error was y a =12.3mm.

[0125] When performing linear approximation using the least squares method, the coefficient of determination R is generally calculated using the following formula (4): 2 It is known that the validity of the approximation by the least squares method can be evaluated using the coefficient of determination R 2 If is close to 1, the distance d iand position y i There is a strong linear relationship between these two, and it can be determined that linear approximation using the least squares method is appropriate.

number

[0126] Therefore, the tilt deviation θ and displacement deviation y obtained by the measurement a Based on the coefficient of determination R 2 When we calculated the value, R 2 =0.996, and R 2 was found to be very close to the value of 1.0.

[0127] Therefore, the inclination deviation θ and the displacement deviation y a The linear approximation by the least squares method based on the above is valid, and the tilt error θ = 2.2° and the displacement error y a = 12.3 mm is found to be a reasonable value that can be used to calibrate the illuminator 510. [Explanation of symbols]

[0128] 1. Measurement object 10, 510 Lighting equipment 15 Linear light 20 screens 30, 520 Imaging device 40, 530 Processing unit 50 Calibration plate 560 Test Surface 100 Shape measuring device

Claims

1. 1. A method for calibrating a shape measuring device that measures a surface shape of a measurement object transported in a transport direction at an inspection position extending in a width direction perpendicular to the transport direction, comprising: an illumination device that irradiates linear light extending in a width direction perpendicular to the conveying direction toward the inspection position; a screen onto which a reflected light image of the linear light reflected by the surface of the measurement object is projected; an imaging device that captures an image of the screen onto which the reflected light image is projected and generates a captured image; a processing unit that measures the surface shape of the measurement object based on the captured image; Using a shape measuring device having an incident side temporary adjustment step of adjusting the position of the illumination device and the angle at which the linear light is irradiated onto the surface of the measurement object as seen from the extending direction of the linear light to a geometric arrangement in which the reflected light image is projected onto the screen; a calibration plate placement step of placing a calibration plate having a linear marker on its surface so that the marker aligns with the inspection position; an illumination step of irradiating the calibration plate with the linear light from the illumination device; an angle adjustment step of adjusting an angle of the illumination device with respect to the conveyance direction as viewed from a normal direction of the measurement object based on the linear light and the marker; a position adjustment step of adjusting a position of the illumination device in the transport direction as viewed from a normal direction of the measurement object based on the linear light and the marker; a calibration plate removal step of removing the calibration plate from the inspection position; A method for calibrating a shape measuring device, comprising:

2. Before the incident side temporary adjustment step, 2. The method for calibrating a shape measurement device according to claim 1, further comprising: an illumination device calibration step of calibrating an actual optical axis of the illumination device based on an amount of deviation between the design optical axis of the illumination device and the actual optical axis of the illumination device in an in-plane direction perpendicular to a direction along the design optical axis of the illumination device.

3. The lighting device calibration step includes: a positioning step of positioning the lighting device so that the test surface faces the lighting device and the normal direction of the test surface is the same direction as the design optical axis of the lighting device; an optical image measuring step of measuring an optical image that appears on the test surface by light irradiated from the illumination device while changing the distance from the illumination device to the test surface along the normal direction of the test surface; a deviation amount calculation step of calculating a deviation amount of the optical image with respect to a design optical axis of the illumination device based on a distance from the illumination device to the test surface and a position of the optical image appearing on the test surface; a calibration step of calibrating an actual optical axis of the lighting device based on the amount of deviation calculated in the deviation amount calculation step; The method for calibrating a shape measurement device according to claim 2 , comprising:

4. 4. The method for calibrating a shape measuring instrument according to claim 3, wherein the deviation amount calculation step calculates the deviation amount by approximating a relationship between the distance and the position of the light image on the test surface measured for each distance using a least squares method.

5. 5. The method for calibrating a shape measuring device according to claim 3, wherein the deviation amount calculation step calculates, as the deviation amounts, an inclination deviation which is an angle between a normal direction of the test surface and an actual optical axis of the lighting device, and a displacement deviation which is a difference between a designed irradiation start position of the lighting device and an actual irradiation start position of the lighting device in an in-plane direction of the test surface.

Images