JP2024000912A - Calibration method for shape measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: 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

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a method for calibrating a shape measuring device.

Conventionally, when measuring the surface shape such as unevenness and roughness of the surface of a measurement target, it is necessary to irradiate the surface of the measurement target with linear light and detect the displacement of the linear light from a reference position. A measurement method using optical cutting was used to detect the surface shape of the object to be measured. The optical cutting method is useful because it can measure minute surface shapes with high precision using a relatively simple device.

On the other hand, if an attempt is made to detect even smaller surface shapes using the optical cutting method, the line width of the linear light must be reduced in principle, and there is a limit to the improvement of resolution.

Therefore, in such cases, linear light is irradiated onto the surface of the measurement target, the reflected light reflected from the surface of the measurement target is projected onto a distant screen, and the reflected light projected onto the screen is A measurement method using an optical lever method has been used in which the surface shape of a measurement target is measured by detecting the displacement of an image (see, for example, Patent Document 1 and Patent Document 2).

Patent No. 6278171 Patent No. 4081414

By using the optical lever method, the displacement of the linear light on the surface of the measurement target can be magnified as the displacement of the reflected light image on the screen, resulting in higher resolution than when using the optical section method. Measurement becomes possible.

However, when using the optical lever method, the relationship between each element such as a lighting device that irradiates linear light, a screen on which a reflected light image is projected, an imaging device that captures the reflected light image projected on the screen, etc. If the various parameters that define the displacement are not suitably calibrated in advance, errors caused by such calibration failures will be magnified in the same way as the displacement.

Therefore, in order to accurately measure the surface shape of the object to be measured using the optical lever method, it is necessary to use the optical section method to determine the various parameters that define the relationships between each element such as lighting equipment and screens. In addition to the above, it was necessary to calibrate with high accuracy.

In addition to the accuracy of each element required for the optical lever method, the parameters that need to be calibrated when using the optical lever method include the accuracy of the linear light irradiated from the illumination device on the measurement target such as the angle, the projection position of the reflected light image on the screen, and the distance between the illumination device and the inspection position of the measurement object (the position on the surface of the measurement object where the linear light is irradiated from the illumination device). There are many such parameters, and among these parameters, there are many that are difficult to adjust individually, such as when adjusting one parameter affects other parameters.

Many of the parameters involved in 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 installed, so it should be possible to obtain them as design values through theoretical calculations. It is.
However, in reality, errors from the design values occur due to unintended placement deviations of each element, mechanical errors in each element, etc., and the surface shape may not be measured with the expected accuracy. there were.

Patent Document 1 and Patent Document 2 disclose a shape measuring device that measures the surface shape of a measurement target using an optical lever method, but in the optical lever method, these many parameters are preferably calibrated. The method was not disclosed. Therefore, when calibrating various parameters in a shape measuring device that uses the optical lever method, it is necessary to rely on trial and error, and the burden during calibration is extremely large.

Therefore, instead of determining the many parameters related to the optical lever method individually for each parameter, it is necessary to determine them based on a certain procedure within a range that does not impair actual measurement accuracy, and to determine the surface of the object to be measured. There was a need to measure shapes with high precision.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for calibrating a shape measuring device that can measure the surface shape of an object to be measured with high precision.

A method for calibrating a shape measuring device according to the present invention is a method for calibrating a shape measuring device that measures the surface shape of an object to be measured that is transported in a transport direction at an inspection position extending in a width direction perpendicular to the transport direction. an illumination device that irradiates linear light extending in a width direction perpendicular to the conveying direction toward the inspection position; and a reflected light image of the linear light reflected on the surface of the measurement object is projected. an imaging device that captures the screen on which the reflected light image is projected and generates a captured image, and an arithmetic processing device that measures the surface shape of the measurement target based on the captured image; Using a shape measuring device having an entrance-side temporary adjustment step of adjusting the geometric arrangement projected on the screen; a calibration plate placement step of arranging a calibration plate having a linear marker on its surface so that the marker matches the inspection position; an illumination step of irradiating the linear light from the illumination device to the calibration plate; and determining an angle of the illumination device with respect to the conveying direction as seen from the normal direction of the measurement object, between the linear light and the marker. and a position adjustment step of adjusting the position of the illumination device in the transport direction, as viewed from the normal direction of the measurement target, based on the linear light and the marker. and a calibration plate removal step of removing the calibration plate from the inspection position.

According to the present invention, it is possible to calibrate a large number of parameters required for highly accurate measurement of the surface shape of an object to be measured based on a fixed procedure without impairing actual measurement accuracy. Therefore, the surface shape of the object to be measured can be measured with high precision.

1 is a schematic diagram illustrating a configuration when implementing a method for calibrating a lighting device according to an embodiment; FIG. FIG. 1 is a block diagram showing the structure of an arithmetic processing device according to the present embodiment. It is a flow chart for explaining processing in a calibration method of a lighting device concerning this embodiment. FIG. 1 is a diagram showing the configuration of a shape measuring device according to the present embodiment. FIG. 2 is a diagram showing the configuration of the shape measuring device according to the present embodiment when viewed from the extending direction of linear light. FIG. 1 is a diagram showing the configuration of the shape measuring device according to the present embodiment when viewed from the normal direction of the object to be measured. FIG. 2 is a diagram showing an example of a captured image generated by the imaging device according to the present invention. FIG. 3 is a diagram for explaining the configuration of a calibration plate according to the present invention. It is a flow chart for explaining processing in a calibration method of a shape measuring device concerning this embodiment. FIG. 3 is a diagram for explaining a method of arranging a calibration plate in the shape measuring device according to the present embodiment. In this embodiment, a process of adjusting the angle of the illumination device when viewed from the normal direction of the measurement target so that the extending direction of the linear light and the marker drawn on the calibration plate will be explained. This is a diagram for To explain the process of adjusting the position of the illumination device in the transport direction when viewed from the normal direction of the measurement target in this embodiment so that the linear light and the marker drawn on the calibration plate overlap. It is a diagram. In this embodiment, a graph is shown that records changes in the position of the optical image in the second direction when the distance in the first direction from the illumination device to the test surface is changed.

The method for calibrating the shape measuring device according to the present embodiment will be described in detail below with reference to the accompanying drawings.

<How to calibrate lighting equipment>
First, the principle of a method for calibrating a lighting device installed in a shape measuring device according to this embodiment will be described below. If the optical axis of the lighting device or the light emission position of the lighting device deviates from the ideal optical axis or emission position that should be in the design, it may cause problems when using the lighting device alone as a shape measuring device. In addition, if an illumination device is incorporated as part of a shape measuring device that measures the surface shape of the object to be measured using the optical lever method, it may be difficult to obtain the original measurement accuracy. This will cause problems such as not being able to do so. Therefore, it is extremely important to calibrate the light emission position and optical axis deviation of the lighting device before using the lighting device.

Therefore, in view of the above problems, in the method for calibrating a shape measuring device according to the present embodiment, it is desirable to calibrate the optical axis and output position of the illumination device to an optimal state in advance.

The configuration used when implementing the lighting device calibration method according to this embodiment will be described using FIG. 1. FIG. 1 shows a configuration used when implementing the method for calibrating a lighting device according to this embodiment. In the method for calibrating a lighting device according to this embodiment, a lighting device 510, an imaging device 520, an arithmetic processing device 530, and a test surface 560 are used.

Note that in the method for calibrating the illumination device 510 according to the present embodiment, a case will be described in which the light emission position and optical axis deviation amount of the illumination device 510 are calculated using the imaging device 520 and the arithmetic processing device 530. However, the present invention is not limited to this. For example, another method for calibrating the illumination device 510 is to measure the processing performed by the imaging device 520 and the arithmetic processing device 530 by the calibration operator himself, without using the imaging device 520 and the arithmetic processing device 530. It may also be executed by recording or the like to calculate the light emission position of the illumination device 510 and the amount of deviation of the optical axis.

The lighting device 510 is a lighting device that has a function of emitting light and is used by being incorporated into a shape measuring device using an optical lever method. The illumination device 510 has a light source and an optical system such as a lens inside, and the casing forming the illumination device 510 can be viewed from an output position on a lens (not shown) provided on the front surface of the illumination device 510. Irradiates light onto the outside of the body. As the light source and optical system provided in the illumination device 510, known ones can be used in combination as appropriate.

Considering the design of the lighting device 510, the lighting device 510 is expected to emit light in a certain direction from a predetermined emission position, and this direction is the ideal designed light of the lighting device 510. Hereinafter, the optical axis designed for this illumination device 510 will be referred to as the designed optical axis IL. Furthermore, due to manufacturing errors or aging deterioration of the lighting device 510, the light emission position on the lens where light is actually emitted (irradiated) from the lighting device 510 may deviate from the designed emission position, or the light emitted from the lighting device 510 may deviate from the designed emission position. It is conceivable that the direction of the actual optical axis of the light may deviate from the designed direction of the optical axis IL. Hereinafter, this non-ideal optical axis that is deviated from the designed optical axis IL and has an error will be referred to as an actual optical axis (or actual optical axis) RIL.

The test surface 560 is a plane for calibration (for example, a plane plate) used in the method for calibrating the illumination device 510 according to this embodiment. The test surface 560 will be hit by light emitted from the illumination device 510 as described later, and the surface that is hit by the light is a substantially flat surface. Note that, as long as the position of the test surface 560 that is irradiated with the light from the illumination device 510 can be specified, the shape of the surfaces other than the surface that is irradiated with the light is not particularly limited. If the roughness of the test surface 560 is too low, the property of specular reflection becomes high, and the light image that appears 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 light image appearing on the test surface 560 becomes blurred, making it difficult to identify the position of the light image on the test surface 560. Therefore, the test surface 560 is preferably formed of a material having a certain degree of roughness, but the type of material itself is not limited.

The imaging device 520 is a camera that captures a light image appearing on the test surface 560 due to light irradiated onto the test surface 560 from the illumination device 510. As the imaging device 520, for example, an area camera such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) is employed. The imaging device 520 uses the surface of the test surface 560 that is illuminated by the light as an imaging field of view, generates a captured image by capturing a light image on the test surface 560, and outputs the generated captured image to the arithmetic processing device 530.

The arithmetic processing unit 530 calculates the amount of deviation of the actual optical axis RIL from the designed optical axis IL of the illumination device 510. The arithmetic processing unit 530 is configured as a computer device having a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like. 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 section 531, a distance acquisition section 532, and a deviation amount calculation section 533. The arithmetic processing unit 530 can function as a calibration device including an image acquisition unit 531, a distance acquisition unit 532, and a deviation amount calculation unit 533 by reading and developing a readable illumination device calibration program.

The image acquisition unit 531 acquires a captured image generated by the imaging device 520. In this case, the image acquisition unit 531 acquires a 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.

The distance acquisition unit 532 acquires the value of the distance between the illumination device 510 and the test surface 560 as distance information when the captured image is captured by the imaging device 520. 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 light-irradiated surface of the test surface 560. It is distance. The distance value determined 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 operator using a measurable ruler or the like. A distance value that is a measurement result is input to the distance acquisition unit 532 as distance information.

The deviation amount calculation unit 533 captured a light image on the test surface 560 with 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. Based on a plurality of captured images, the amount of deviation between the designed optical axis IL of the illumination device 510 and the actual optical axis RIL is calculated. As will be described in detail later, the deviation amount calculation unit 533 calculates 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 image taken for each distance. Based on this, the amount of deviation between the designed optical axis IL and the actual optical axis RIL is calculated.

Next, processing in the method for calibrating a lighting device according to this embodiment will be described using FIGS. 1 to 3. FIG. 3 shows a flowchart for explaining the processing in the lighting device calibration method according to the present embodiment.

(Step S501)
When the method for calibrating the lighting device 510 according to this embodiment is started, the process of step S501 is performed. In step S501, the illumination device 510 and the test surface 560 are arranged to face each other so that the designed optical axis IL of the illumination device 510 and the normal direction of the test surface 560 are in the same direction (arrangement step). .

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

For example, as shown in FIG. 1, the lighting device 510 is configured with a casing having a flat bottom surface, and the optical axis IL of the lighting device 510 is designed to point in a direction parallel to the bottom surface of the casing. Suppose that Further, the emission position, which is the position on the lens from which light is emitted from the illumination device 510, is the origin O, and p passes through the origin O in a direction parallel to the first direction (the direction of the optical axis IL in the design of the illumination device 510). It is assumed that the q-axis is taken in a second direction (direction of the surface of the test surface 560) passing through the origin O and perpendicular to the first direction.

Here, for example, if an illumination device 510 removed from a shape measuring device to be described later is placed on a reference surface 561 that is a plane horizontal to the p-axis serving as a reference and irradiates light toward the test surface 560, the illumination Due to the design of the device 510, light is emitted from the origin O in parallel in the first direction and reaches the point A on the test surface 560, and the designed optical axis IL is a straight line connecting the origin O and the point A. becomes. In addition, if the light emission position and irradiation direction (actual optical axis direction) of the illumination device 510 deviate from the design, the position on the lens of the illumination device 510 is not from the origin O but from the origin O. Light is emitted from the shifted point C and reaches point B on the test surface 560, and the actual optical axis RIL becomes a straight line connecting points C and B.

In order to simplify the explanation, here we will explain the case where the first direction is the horizontal direction and the second direction is the height direction, but the first direction and the second direction are As long as the positions are perpendicular to each other, the present invention is not limited to this case. Further, the designed optical axis IL does not depend on the shape of the casing of the illumination device 510, but depends on the direction in which light is irradiated in the design of the illumination device 510.

In step S501, when the illumination device 510 and the test surface 560 are arranged as described above, the process proceeds to step S503.

(Step S503)
In step S503, while changing the distance from the illumination device 510 to the test surface 560 along the normal direction of the test surface 560, the light image that appears on the test surface 560 according to the distance is measured by the light irradiated from the illumination device 510. do. That is, while changing the distance d ⁱ from the illumination device 510 to the test surface 560 along the first direction (for example, horizontal direction), the measurement index is set to i, and the light emitted from the illumination device 510 appears on the test surface 560. The position y ⁱ _b (for example, the position in the height direction, which is the second direction) of the optical image is measured (light image measurement step).

Since the light emitted from the illumination device 510 creates an optical image on the test surface 560, it is possible to easily observe which position on the test surface 560 the emitted light has reached.

If light is emitted from the illumination device 510 along the designed optical axis IL (for example, in the horizontal direction), even if the distance between the illumination device 510 and the test surface 560 is changed, the test surface 560 Since it is perpendicular to the direction of the light, the position of the light image generated when the test surface 560 is irradiated with light does not change in the second direction (here, the height direction). On the other hand, if the actual optical axis RIL of the illumination device 510 deviates from the designed optical axis IL, as the distance between the illumination device 510 and the test surface 560 is changed along the first direction, the test surface 560 The position of the optical image generated when light is irradiated upward changes along the second direction (height direction). Therefore, by measuring the change in the second direction of the light image on the test surface 560, it is possible to determine how far the actual optical axis RIL emitted from the illumination device 510 differs from the designed optical axis IL in terms of the emission position and the irradiation angle. You can tell if it's out of alignment.

Here, while changing the distance d ⁱ between the illumination device 510 and the test surface 560 multiple times (i is an index corresponding to the measurement times), the light image on the test surface 560 is changed along with the value of the distance d ⁱ . The position y ⁱ _b in the second direction (the height from the origin O in the case of FIG. 1) is measured.

In this embodiment, the distance acquisition unit 532 acquires the value of the distance d ⁱ , the image acquisition unit 531 acquires a captured image in which a light image is captured for each distance d ⁱ , and based on the position of the light image in the captured image. Then, the position y ⁱ _b of the optical image appearing on the test surface 560 in the second direction is obtained. Then, the deviation amount calculation unit 533 analyzes the captured image in which the light image is captured at each distance d ⁱ , and calculates the position y ⁱ _b of the light image on the test surface 560 in the second direction within the captured image by the distance d ⁱ Measure each time. Note that, as described above, these processes do not necessarily need to be performed on the arithmetic processing device 530, and may be manually measured and recorded by the proofreading operator himself.
If data for an appropriate number of measurements is obtained, the process advances to step S505.

(Step S505)
In step S505, based on the distance d ⁱ from the illumination device 510 to the test surface 560 and the position of the light image appearing on the test surface 560 for each distance d ⁱ , the light image with respect to the designed optical axis IL of the illumination device 510 is The amount of deviation is calculated according to the distance d ⁱ between the illumination device 510 and the test surface 560. For example, by approximating the relationship between the distance d ⁱ in the first direction from the illumination device 510 to the test surface 560 and the position y ⁱ _b of the optical image in the second direction, The inclination shift 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 irradiation start position (actual emission position) of the actual optical axis RIL of the illumination device 510. and the designed irradiation start position of the optical axis IL (designed emission position) in the second direction. The displacement of the illumination device 510 corresponding to the difference in position in the second direction is calculated as the amount of deviation (deviation amount calculation step) .

In the example of FIG. 1 described above, the positional deviation between the origin O and the point C in the second direction corresponds to the displacement deviation, and the angle θ formed by the designed optical axis IL and the actual optical axis RIL is Corresponds to tilt deviation.

More specifically, as shown in FIG. It is assumed that the illumination device 510 is located a distance d ⁱ from the illumination device 510 (having an emission position at ). The light irradiated along the designed optical axis IL is supposed to reach the point A (d ⁱ , 0) on the test surface 560 from the origin O (0, 0). However, the light irradiated along the actual optical axis RIL is irradiated from a point C (0, y _a ) on the q-axis, which is an emission position vertically shifted by y _a from the origin O, and Assuming that a point B (d ⁱ , y ⁱ _b ) on the test surface 560 is reached by being irradiated at an angle shifted by an angle θ from the upper optical axis IL, the relationship between the illumination device 510 and the test surface 560 is From the geometrical positional relationship, the following equation (1) can be obtained.

The value of the distance d ⁱ and the value of the position y ⁱ _b of the light image on the test surface 560 in the second direction are determined in step S503 to determine the actual position of the test surface 560 and the position of the light image on the test surface 560. It can be known by measuring.

Therefore, for example, by changing the position of the test surface 560 along the first direction, the distance d ⁱ is changed, and each distance d ⁱ and the position y ⁱ _b of the optical image on the test surface 560 in the second direction are changed. By determining the values of , it is possible to calculate the displacement deviation y _a and the tilt deviation θ, which are unknown values. Furthermore, in order to further improve accuracy, it is preferable to use the least squares method to calculate the displacement deviation y _a and the tilt deviation θ. In that case, the displacement deviation y _a and the tilt deviation θ are It can be calculated using the following equations (2) and (3), where n is the total number of data obtained by doing so.

Note that the displacement shift _ya is a distance shift (offset) in the second direction between the light output position on the actual optical axis RIL of the illumination device 510 and the light output position on the designed optical axis IL. Further, the tilt deviation θ is an angular deviation corresponding to the difference in direction between the actual optical axis RIL and the designed optical axis IL of the illumination device 510.

In this way, if the displacement deviation y _a and the tilt deviation θ can be known as the deviation amount, the lighting device 510 is calibrated based on the displacement deviation y _a and the tilt deviation θ (calibration step), and the lighting device according to the present embodiment The calibration method of step 510 ends.

As explained above, according to the present embodiment, since it is possible to know the displacement deviation y _a and the tilt deviation θ according to the error of the lighting device 510, when the lighting device 510 is used, the lighting device 510 The illumination device 510 can be used after giving an offset or tilting it according to the displacement deviation y _a and the inclination deviation θ. It will be possible to emit light in a direction. Therefore, when the illumination device 510 is used in a shape measuring device using the optical lever method, it is possible to prevent problems caused by errors in the illumination device 510 from occurring.

As explained above, in this embodiment, the displacement deviation _ya and the tilt deviation θ, which are necessary for highly accurate measurement of the surface shape of the object to be measured, are calibrated within a range that does not impair the actual measurement accuracy. , can be performed based on a fixed procedure, so the surface shape of the object to be measured can be measured with high precision.

As described above, in this embodiment, the displacement deviation y _a and the tilt deviation θ are calculated by employing the least squares method to calculate the deviation amount, but the present invention is not limited to this. do not have. For example, when calculating the amount of deviation, an LUT (Look Up Table) is created that correlates the distance between the illumination device 510 and the test surface 560 with the amount of deviation obtained at that time. The illumination device 510 may be calibrated by referring to the amount of deviation corresponding to the distance between the illumination device 510 and the test surface 560 along the optical axis IL. Note that if there is no deviation amount on the LUT that matches the arrangement position of the lighting device 510, the deviation amount can be calculated by proportional distribution by referring to the deviation amount at the front and rear distances on the LUT that sandwich the distance at the arrangement position. good.

<Calibration method of shape measuring device>
Next, a method for calibrating a shape measuring device capable of measuring the surface shape of a measurement object using an optical lever method using a lighting device calibrated by the method for calibrating a lighting device described above will be described below. A method for calibrating a shape measuring device using an 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 the drawings, components having substantially the same functional configuration as those described above may be designated by the same reference numerals, thereby omitting redundant explanations.

Here, linear light is irradiated from the illumination device onto the surface of the object to be measured at a predetermined incident angle, the reflected light from the surface of the object to be measured is projected on a screen, and measurements are taken based on the reflected light image on the screen. In the measurement method that uses the optical lever method to measure the surface shape of an object, even if the elements such as the lighting device and screen that make up the shape measurement device are arranged as designed, the actual position of each element is There is a possibility that there may be unintended slight deviations in the direction, angle, etc., or that each element itself may contain errors.

In addition, if the calibration of the shape measuring device using the optical lever method is insufficient (accuracy is poor), the surface shape of the object to be measured can be measured through the reflected light image (bright line) projected on the screen. When doing so, not only displacements depending on the surface shape but also errors due to insufficient calibration are magnified and displayed, making it difficult to perform highly accurate measurements. Furthermore, calibration is complicated because shape measuring devices that use the optical lever method have a wide variety of parameters to calibrate, and adjusting one parameter may affect other parameters, causing changes in other parameters. Since problems such as calibration may occur, it has been desired to define procedures for performing calibration.

Therefore, in view of the above-mentioned problems, in the method for calibrating a shape measuring device using the optical lever method according to the present embodiment, the calibration of a large number of parameters related to the measurement method using the optical lever method is performed without compromising the accuracy of actual measurement. Provides a method that can be carried out based on certain procedures to the extent that the

The configuration used in the method for calibrating the shape measuring device according to this embodiment will be explained using FIGS. 4 to 6. FIG. 4 shows the configuration of the shape measuring device 100 according to this embodiment. FIG. 5 shows the configuration of the shape measuring device 100 according to this embodiment when viewed from the extending direction of the linear light. FIG. 6 shows the configuration of the shape measuring device 100 according to this embodiment when viewed from the normal direction of the surface of the object to be measured 1. As shown in FIG.

The shape measuring device 100 is a device that detects the surface shape of the object to be measured 1 moving in the transport direction at a predetermined inspection position LB extending along the width direction perpendicular to the transport direction on the surface of the object to be measured 1. A shape measuring device using a known optical lever method can be used as long as it does not contradict the following description. A shape measuring device 100 using the optical lever method includes an illumination device 10, a screen 20, an imaging device 30, and an arithmetic processing device 40. Note that the lighting device 10 has the same configuration as the lighting device 510 described above, and it is desirable that the actual optical axis be calibrated according to the method of calibrating the lighting device 510 described above.

The measurement object 1 is an object to be measured (inspected) when the shape measuring apparatus 100 measures a surface shape such as defects such as unevenness or unevenness of roughness existing on the surface.

The object to be measured 1 can be, for example, various types of steel plates such as flat thick plates or thin plates, but is not limited thereto, and the surface shape can be measured using a measurement method using an optical lever method. Various objects can be used as measurement objects as long as they can be measured.

The object to be measured 1 is transported relative to the shape measuring device 100 along a predetermined transport direction by a transport device (not shown). That is, the object to be measured 1 may be moved while the shape measuring device 100 is fixed, or the object to be measured 100 may be moved while the object to be measured 1 is fixed, and the object to be measured 1 and its shape may be moved. Both measurement devices 100 may be moved. When the object to be measured 1 is transported, tension may be applied to both ends of the object to be measured 1 to avoid vibrations, deflections, etc. as much as possible.

The illumination device 10 runs perpendicular to the transport direction in the in-plane direction of the surface of the measurement target 1 toward the measurement target 1 or the position where the measurement target 1 should be, more specifically toward an inspection position LB, which will be described later. This lighting device has a function of emitting linear light 15 extending in the width direction.

The illumination device 10 has a light source and an optical system such as a lens inside the housing, and has a line extending long in the width direction perpendicular to the conveyance direction of the measurement target 1 and having a narrow width in the conveyance direction. A linear light 15 is generated, and the linear light 15 is irradiated toward the surface of the object 1 to be measured. The linear light 15 extends so as to cover substantially the entire width of the measurement object 1 . As the light source and optical system provided in the illumination device 10, known ones can be used in combination as appropriate.

The center wavelength of the light emitted from the illumination device 10 is designed in consideration of the specular reflectance 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 likely it is to be specularly reflected on the surface of the measurement object 1, so the brightness of the reflected light image (bright line) RI formed on the screen 20 increases. , the S/N ratio increases. On the other hand, when the center 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 decreases within the captured image PH, and the S/N ratio decreases. Therefore, the center wavelength of the illumination device 10 is designed with the lower limit being a wavelength that takes the specular reflectance of the measurement object 1 into consideration, and the upper limit being a wavelength that takes into account the wavelength sensitivity characteristics of the imaging device 30.

The spectral width of the light emitted from the illumination device 10 is designed in consideration of speckle noise observed on the reflected light image RI. When light with a small spectral width, such as laser light, is used in the shape measuring device 100, speckle noise in the form of a fine speckled pattern with high contrast occurs in the reflected light image RI in the captured image PH, resulting in a reduction in S/N. ratio decreases. Therefore, the lighting device 10 uses light with a wide spectrum width and low coherence.

The linear light 15 irradiated from the illumination device 10 is irradiated toward the surface of the object to be measured 1 in a range indicated by a broken line 15a in FIGS. The light hits the surface in a linear manner (linear light 15) and is reflected. The reflected light of the linear light 15 reflected at the inspection position LB on the surface of the measurement object 1 passes through the range shown by the broken line 15b in FIGS. Appears as RI.

As is clear from the principle of the measurement method using the light cutting method, the linear light 15 is displaced depending on the surface shape of the surface of the measurement object 1 at the position where the linear light 15 is irradiated. Based on the displacement of the linear light 15, the surface shape of the measurement target 1 at the position irradiated with the linear light 15 can be measured. That is, the shape measuring device 100 using the optical lever method measures the shape of the surface of the object to be measured 1 at the position where the surface of the object to be measured 1 is irradiated with the linear light 15. The position on the surface of the object 1 that is irradiated with the linear light 15 (and the position corresponding to the position on the surface of the object 1 that is irradiated with the linear light 15 if the object 1 to be measured does not exist) is , is the position used when measuring the surface shape.

Therefore, it corresponds to the position on the surface of the measurement object 1 irradiated with the linear light 15 (and in cases where the measurement object 1 does not exist, the position on the surface of the measurement object 1 irradiated with the linear light 15). position) is referred to as an 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 orthogonal to the conveyance direction.

In order to improve the measurement accuracy of the surface shape, the illumination device 10 uses an optical system provided inside the housing to measure the linear light 15 in the most focused state (that is, the state in which the line width of the linear light 15 is the narrowest). It is preferable that the light 15 hits the surface of the object to be measured 1 at the inspection position LB.

As shown in FIG. 4, here, the center position of the linear light 15 irradiated onto the measurement object 1 by the illumination device 10 in the extending direction on the surface of the measurement object 1 is defined as the origin O1, and the measurement is performed after passing through the origin O1. The y-axis is the axis that runs in the transport direction of the object 1, and the x-axis is the axis that passes through the origin O1 and runs in the width direction perpendicular to the transport direction of the object 1. The axis in the linear direction is defined as the z-axis. In this case, as shown in FIG. 5, the linear light 15 irradiated from the illumination device 10 has an incident angle defined by the angle formed with the z-axis with respect to the surface of the measurement target 1 when viewed from the x-axis direction. Irradiation is performed at θ1. Then, the linear light 15 is reflected at the inspection position LB on the surface of the measurement object 1 at a reflection angle θ1 defined by the angle with the z-axis when viewed from the x-axis direction, and the reflected light hits the screen 20. On the opposite side, it is projected as a reflected light image RI.

Note that the illumination device 10 is arranged so as to irradiate the linear light 15 in the direction of conveyance of the object to be measured 1 when viewed from the z-axis direction. In the stage before calibration), as shown in FIG. There is also a risk that the irradiation direction) may shift. In this case, the illumination device 10 emits linear light 15 in the direction of a chain double-dashed line 10a that has an angle Φ (hereinafter also referred to as a swing angle Φ) with respect to the conveying direction when viewed from the z-axis direction. There may be cases where you have already done so.

Further, in consideration of the design of the lighting device 10 itself, the lighting device 10 is expected to emit linear light 15 in a certain direction from a predetermined emission position. Due to manufacturing errors or deterioration over time, the position on the lens from which the linear light 15 is emitted from the lighting device 10 may deviate from the designed emission position, or the irradiation direction of the linear light 15 emitted from the lighting device 10 may change. It is also conceivable that the direction may deviate from the ideal direction. Therefore, when using the lighting device 10, it may be necessary to calibrate the lighting device 10 itself as appropriate.

The lighting device 10 is held by a support part (not shown), and by moving the support part together, the position of the lighting device 10 can be changed along the conveyance direction. Further, it is preferable that the lighting device 10 is held on the support portion 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.

The screen 20 is an object that functions as a projection film on which the reflected light of the linear light 15 reflected on the surface of the measurement object 1 is projected as a reflected light image RI. The screen 20 is disposed at 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 arranged such that the normal vector of the projection plane of the screen 20 has no x component (the value of the x component is zero) in the xyz coordinate system shown in FIG. .

The screen 20 is configured such that the linear light 15 irradiated from the illumination device 10 is reflected at the inspection position LB on the surface of the object to be measured 1, so that the entire reflected light image RI (full length, full width) is generated on the screen 20. , is large enough to be reflected in the image, and it is 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 property of specular reflection will be high and the reflected light image RI on the screen 20 will become invisible. Furthermore, if the roughness is too high, the shape of the reflected light image RI becomes blurred, making it difficult to identify the position. Therefore, the screen 20 is preferably formed of a material having a certain degree of roughness, but the type of material itself is not limited.

The larger the distance from the inspection position LB, the screen 20 is able to enlarge and detect the surface shape of the measurement object 1 at the inspection position LB, but the brightness of the linear light 15 also attenuates more. As a result, the S/N ratio deteriorates. Therefore, it is preferable to actually measure the distance from the inspection position LB to the screen 20 in advance to understand the market price for the distance to a certain extent.

The imaging device 30 functions as a camera that images the screen 20 on which the reflected light of the linear light 15 is projected as a reflected light image RI, and generates a captured image. That is, the imaging device 30 images an area on the screen 20, which includes at least all of the reflected light image RI projected onto the surface of the screen 20, as an imaging field of view, as shown by the dashed line in FIGS. 4 to 6. Then, a captured image PH is generated. Therefore, the reflected light image RI projected onto the screen 20 is reflected in the captured image PH.

Note that in this embodiment, when the actual optical axis of the illumination device 10 is calibrated according to the method for calibrating the illumination device 510, the imaging device 30 may be applied as the imaging device 520 shown in FIG. Furthermore, the imaging device 520 used when calibrating the illumination device 10 may be provided separately from the imaging device 30 of the shape measuring device 100.

The captured image PH is preferably a two-dimensional captured image consisting of a two-dimensional image, and the imaging device 30 is preferably an area camera that generates a two-dimensional captured image. The imaging device 30 may be a monochrome camera or a color camera, and the captured image PH may be a monochrome image or a color image.

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, and the like. As shown in FIG. 4 (not shown in FIGS. 5 and 6), the arithmetic processing device 40 is connected to the imaging device 30 by wire or wirelessly, and processes the captured images generated by the imaging device 30. PH can be obtained.

Based on the acquired captured image PH, the arithmetic processing unit 40 calculates the measurement target 1 from the displacement of the linear light 15 reflected in the captured image PH using a measurement method using a known optical lever method. The surface shape at the surface inspection position LB can be measured.

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 arithmetic processing unit 40 includes the image acquisition unit 531 and the distance acquisition unit 532 shown in FIG. A configuration may also be provided in which a deviation amount calculation unit 533 is provided. Furthermore, the arithmetic processing device 530 that calibrates the lighting device 10 may be provided separately from the arithmetic processing device 40.

FIG. 7 shows an example of a captured image PH generated by the imaging device 30 according to the present invention. If there are irregularities on the surface of the object to be measured 1 at the inspection position LB (FIG. 6), the reflected light image RI reflected in the captured image PH will show that the surface of the object to be measured 1 at the inspection position LB is flat. Using the reflected light image RI in a certain case as a reference line, a concave or convex displacement CD occurs in the reflected light image RI.

Since the displacement CD of this reflected light image RI corresponds to the unevenness of the surface of the object to be measured 1, the surface of the object to be measured 1 at the inspection position LB is Shape can be determined. In addition, since the measurement object 1 is being 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 of the measurement object 1 changes. The surface shape can be measured at each position along the transport direction.

Further, as will be described later, the shape measuring device 100 uses the calibration plate 50 when calibrating the shape measuring device 100.

The calibration plate 50 is, for example, a flat plate on which linearly extending markers CL are drawn on the surface as shown in FIG. It is used to adjust the position of the device 10.

The marker CL drawn on the calibration plate 50 may be printed on the calibration plate 50 or may be affixed to the calibration plate 50 with a sticker or the like, or may be formed by forming a shallow recess on the surface of the calibration plate 50. In addition, the marker CL itself may be a solid line, a dotted line, or the like.

When calibrating the shape measuring device 100, as will be described later, the inspection position LB and the marker CL are compared, so the calibration plate 50 can be placed accurately at the inspection position LB. It is preferable that the size and shape are such that the inspection position LB and the marker CL can be compared.

The calibration plate 50 has enough rigidity that it will not bend even if it is placed at an arbitrary position. If the roughness of the calibration plate 50 is too low, the property of specular reflection will be high, and the linear light 15 may become invisible at the inspection position LB, making it impossible to compare the marker CL and the linear light 15. Furthermore, if the roughness is too high, the shape of the linear light 15 may become blurred, making it difficult to identify the position. Therefore, the calibration plate 50 is preferably formed of a material having a certain degree of roughness, but the type of material itself is not limited.

Next, processing in the method for calibrating the shape measuring device 100 according to the present embodiment will be described using FIG. 9. FIG. 9 shows a flowchart for explaining the processing in the method of calibrating the shape measuring device 100 according to the present embodiment.

(Step S101)
When the method for calibrating the shape measuring device 100 according to this embodiment is started, the process of step S101 is performed. In step S101, the actual optical axis with respect to the designed optical axis of the lighting device 10 is determined in a direction perpendicular to both the direction along the designed optical axis of the lighting device 10 and the extending direction of the linear light 15. By calibrating, the lighting device 10 itself is calibrated (lighting device calibration step).

As described above, the emission position of the linear light 15 irradiated from the lighting device 10 and the direction of the actual optical axis may differ due to manufacturing errors or aging deterioration of the lighting device 10 itself. There is a possibility that the output position and the direction of the optical axis are deviated from the ideal output position determined in the design. Therefore, in step S101, the emission position of the linear light 15 irradiated from the illumination device 10 and the direction of the actual optical axis are calibrated.

As a method for calibrating the lighting device 10 itself, any known method for calibrating a lighting device can be used as appropriate, but for example, it is desirable to use the method for calibrating the lighting device 510 according to the present embodiment. In this case, in the lighting device calibration step, the lighting device 10 is calibrated according to the flowchart shown in FIG. Specifically, for example, by using the method of calibrating the illumination device 510 according to the present embodiment, it is possible to calibrate the illumination device 510 in both the direction along the designed optical axis of the illumination device 10 and the extending direction of the linear light 15. The amount of deviation of the actual linear light 15 from the designed optical axis of the illumination device 10 in the orthogonal direction (that is, 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.

(Step S103)
In step S103, the position of the illumination device 10 calibrated in step S101 and the angle at which the surface of the measurement object 1 is irradiated with the linear light 15 as seen from the extending direction of the linear light 15 are determined as reflected light images. The geometric arrangement is adjusted such that the RI is projected onto a predetermined position on the screen 10. That is, the angle of depression of the illuminating device 10 with respect to the measurement target 1 when viewed from the extending direction of the linear light 15 (the angle of the optical axis of the illuminating device 10 when viewed from the extending direction of the linear light 15) is The geometrical arrangement is adjusted so that the reflected light image RI of the light 15 is projected onto a predetermined position of the screen 20 (for example, the center of the screen 20) (incidence side provisional adjustment step).

In the measurement method using the optical lever method, the surface shape at the inspection position LB of the surface of the object to be measured 1 is measured based on the displacement of the reflected light image RI projected on the screen 20. Even if there is a displacement, 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 view of the imaging device 30). Therefore, in order to secure as much margin as possible, the illumination device 10 is adjusted so that the reflected light image RI is placed approximately at the center of the screen 20.

Since the distance between the screen 20 and the inspection position LB is constant, if the height at which the illumination device 10 is arranged is arbitrarily determined, the reflected light image RI of the linear light 15 will be reflected from the screen 20 due to the geometrical relationship. The position of the illumination device 10 and the angle of the illumination device 10 with respect to the inspection position LB when projected onto the central portion are uniquely determined. Therefore, the lighting device 10 is adjusted so that the distance and angle are determined based on such geometrical relationships.

However, even if the illumination device 10 is made to have the correct position and angle as much as possible, the accuracy of the shape measurement device 100 will actually affect the measurement results if only such geometric adjustments are made. In many cases, the reflected light image RI is not projected onto the center of the screen 20 according to the geometrical relationship due to potential deviations that may affect the actual projection position of the reflected light image RI. The lighting device 10 is adjusted according to the position and angle determined geometrically. 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.

(Step S105)
In step S105, the calibration plate 50 on which a linear marker CL is drawn is arranged so that the marker CL drawn on the calibration plate 50 matches the inspection position LB (calibration plate placement step).

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

FIG. 10 shows a diagram for explaining a method of arranging the calibration plate 50 in the shape measuring device 100 according to the present embodiment. In FIG. 10, for the sake of explanation, the measurement object 1 is indicated by a broken line at the location where the measurement object 1 was placed. As shown in FIG. 10, since the inspection position LB is a linear region extending in the width direction perpendicular to the conveyance direction of the measurement target 1, the linear marker CL drawn on the calibration plate 50 is It can be arranged so as to match the position of LB (so that the straight line of marker CL and the extending direction of inspection position LB are aligned).
When the arrangement of the calibration plate 50 in step S105 is completed, the process advances to step S107.

(Step S107)
In step S107, the illumination device 10 is used to irradiate the linear light 15 (illumination step). In step S105, since the marker CL of the calibration plate 50 is arranged to overlap the inspection position LB, if the linear light 15 is irradiated from the illumination device 10, the distance from the illumination device 10 to the inspection position LB or If there is no error in the irradiation angle of the linear light 15 from the illumination device 10, the linear light 15 irradiated from the illumination device 10 is irradiated so as to overlap the straight line CL drawn on the calibration plate 50. It is expected. When the illumination device 10 starts irradiating the linear light 15 in step S107, the process advances to step S109.

(Step S109)
In step S109, the angle Φ (oscillation angle Φ) of the illumination device 10 with respect to the conveying direction as seen from the normal direction of the measurement target 1 is adjusted based on the linear light 15 and the marker CL of the calibration plate 50. . That is, the swing angle Φ of the illumination device 10 when viewed from the normal direction of the measurement object 1 is determined by the direction in which the linear light 15 extends and the direction in which the marker CL drawn on the calibration plate 50 extends. Adjust so that they are parallel (angle adjustment step).

FIGS. 11(a) and 11(b) show the swing angle Φ of the illumination device 10 with respect to the conveying direction when viewed from the normal direction of the measurement object 1, and the extending direction of the linear light 15, A diagram for explaining a process of adjusting so that the extending direction of the marker CL drawn on the calibration plate 50 is parallel to the extending direction is shown.

As shown by the two-dot chain line 10a in FIG. 6, the illumination device 10 provides illumination in the y-axis direction, which is the transport direction, when viewed from the z-axis direction (that is, when viewed from the normal direction of the measurement target 1). Assuming that the actual optical axis of the device 10 has a swing angle Φ, the extending direction of the linear light 15 is perpendicular to the swing angle Φ, so as shown in FIG. 11(a), The marker CL and the linear light 15 are not parallel to each other.

Therefore, in step S109, while visually checking the linear light 15 and the marker CL, While being careful not to change the angle at which the linear light 15 is irradiated onto the surface of ), the extending direction of the linear light 15 and the extending direction of the marker CL are made parallel to each other.
After adjusting the swing angle Φ of the illumination device 10 so that the extending direction of the linear light 15 and the marker CL are parallel to each other in step S109, the process proceeds to step S111.

(Step S111)
In step S111, the position of the illumination device 10 in the transport direction as viewed from the normal direction of the measurement target object 1 is adjusted based on the linear light 15 and the marker CL of 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).

12(a) and 12(b) show the position of the illumination device 10 in the transport direction when viewed from the normal direction of the measurement object 1, drawn on the linear light 15 and the calibration plate 50. A diagram for explaining a process of adjusting so that the marker CL overlaps with the marker CL is shown.

As shown in FIG. 12(a), when viewed from the z-axis direction (viewed from the normal direction of the measurement target 1), the extending direction of the linear light 15 and the drawing on the calibration plate 50 are determined in step S109. Although the extending direction of the marker CL is adjusted to be parallel to the extending direction of the marker CL, there is a difference in the transport direction (y-axis direction) between the linear light 15 and the marker CL drawn on the calibration plate 50. ) there is a positional shift.

Therefore, in step S111, while visually checking the linear light 15 and the marker CL, The position of the illumination device 10 is adjusted along the transport direction while being careful not to change the angle at which the linear light 15 is irradiated onto the surface of the The light 15 and the marker CL are made to overlap.
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.

(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 measuring object 1 whose surface shape is to be inspected is transported toward the shape measuring device 100. It becomes possible to measure the surface shape of

In this way, when the calibration of the shape measuring device 100 is completed and the surface shape can be measured, the method for calibrating the shape measuring device 100 according to the present embodiment is completed.

As explained above, according to the present embodiment, the shape measuring device 100 using the optical lever method, which has a wide variety of parameters to be adjusted, and there may be parameters that cannot be adjusted freely, can be adjusted based on certain guidelines. You will be able to perform calibration.

By performing such calibration, it is possible to calibrate the shape measuring device 100 with a minimum amount of trial and error without having to randomly trial and error a large number of parameters.

In addition, by performing such calibration, the calibration operator may think that each element of the shape measuring device 100, such as the lighting device 10 and the screen 20, has been adjusted to the geometrically correct arrangement and angle. Even if there is an error related to an element that the calibrator cannot recognize, the shape measuring device 100 can be calibrated so that there is no error that would cause a practical problem.

As described above, the method for calibrating the shape measuring device 100 according to the present embodiment calibrates a large number of parameters required to measure the surface shape of the object 1 with high precision within a range that does not impair the actual measurement accuracy. , can be performed based on a fixed procedure, so that the surface shape of the object to be measured 1 can be measured with high precision.

<Other embodiments>
Note that the light (linear light 15) irradiated from the lighting device 10 hits the test surface 560 used when calibrating the lighting device 10 in the lighting device calibration step of step S101 in FIG. However, the shape of the surfaces of the test surface 560 other than the surface that is illuminated by the light is not particularly limited, as long as the surface that is illuminated by the light is substantially flat and the position that is irradiated with the light can be specified. As the material for the test surface 560, it is preferable to use a material with relatively low light diffusivity because the shape of the outer edge formed by the light on the test surface 560 can be easily identified. In calibrating the illumination device 10, the illumination device 10 may be removed from the shape measurement device 100, or the illumination device 10 may be calibrated with the illumination device 10 attached to a predetermined position of the shape measurement device 100.

Furthermore, in the above-described embodiment, a case has been described in which both the displacement deviation y _a and the tilt deviation θ are calculated as the deviation amount, but the present invention is not limited to this _. Only one of the deviations θ may be calculated as the deviation amount.

In the above-described embodiment, for example, the displacement of the test surface 560 is defined as the difference between the designed irradiation start position of the illumination device in the in-plane direction of the test surface and the actual irradiation start position of the illumination device. In the in-plane direction, the case where the displacement deviation _{y a} in the height direction (second direction) orthogonal to the normal direction (first direction) of the test surface 560 is calculated has been described, but the present invention is not limited to this. In the in-plane direction of the test surface 560, displacement deviations may be calculated in various second directions, such as the width direction orthogonal to the normal direction of the test surface 560.

In addition, in the above-described embodiment, the deviation between the designed optical axis of the lighting device and the actual optical axis of the lighting device in the in-plane direction orthogonal to the direction along the designed optical axis of the lighting device. As a lighting device calibration step of calibrating the actual optical axis of the lighting device based on the amount of light emitted from the lighting device 510 while changing the distance from the lighting device 510 to the test surface 560 along the normal direction of the test surface 560. The position of the light image appearing in the in-plane direction of the test surface 560 (in-plane direction perpendicular to the direction along the designed optical axis of the illumination device 510) is measured for each distance by the light emitted, and the designed optical axis is determined. Although the illumination device calibration step of calculating the amount of deviation with respect to the actual optical axis and calibrating the actual optical axis based on the amount of deviation has been applied, the present invention is not limited to this. For example, the illumination device 10 is moved so as to change the distance to the measurement target 1 without using the test surface 560, and the measurement target is Various other calibration methods may be applied, such as measuring the position of the optical image projected on the optical axis 1 and calibrating the actual optical axis.

Note that in the embodiments described above, the captured image naturally includes not only the form of a specific image displayed on a display unit such as a display, but also data before being generated as an image on the display unit. It is.

FIG. 13 shows that in this embodiment, the distance d ⁱ from the illumination device 510 to the test surface 560 is changed along the normal direction (first direction) of the test surface 560, and the light on the test surface 560 is A graph is shown in which the position y ⁱ of the image in the second direction is examined and the change in the position y ⁱ of the optical image is recorded.

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

As shown in FIG. 13, the distance d ⁱ is changed in 10 patterns (i is used in 10 ways), the position of the optical image on the test surface 560 is measured for each distance d ⁱ , and a 10-point plot is obtained. Ta.

An approximated curve obtained by linear approximation using the least squares method using the acquired data at 10 points is shown by a black dashed line in FIG.

When the inclination deviation θ was calculated from the above equation (2) and the displacement deviation _ya was calculated from the above equation (3), the inclination deviation θ=2.2° and the displacement deviation y _a =12.3 mm.

When performing linear approximation using the least squares method, it is generally known that the validity of the least squares approximation can be evaluated using the coefficient of determination ^R2 shown in equation (4) below. There is. If the coefficient of determination R ² is close to 1, it can be determined that there is a strong linear relationship between the distance d ⁱ and the position y ⁱ , and that the linear approximation by the least squares method is appropriate.

Therefore, when the coefficient of determination R ² was calculated based on the tilt deviation θ and the displacement deviation _{y a} obtained through measurement, R ² =0.996, which indicates that R ² is a value very close to the value of 1.0. I found out that it will happen.

Therefore, the linear approximation by the least squares method based on the inclination deviation θ and the displacement deviation y _a derived in this embodiment is appropriate, and the inclination deviation θ = 2.2° and the displacement deviation y _a = It can be seen that 12.3 mm is a reasonable value that can be used to calibrate the illumination device 510.

1 Measurement object 10, 510 Illumination device 15 Linear light 20 Screen 30, 520 Imaging device 40, 530 Arithmetic processing device 50 Calibration plate 560 Test surface 100 Shape measuring device

Claims (5)

A method for calibrating a shape measuring device that measures the surface shape of a measurement target being transported in a transport direction at an inspection position extending in a width direction perpendicular to the transport direction, the method comprising:
an illumination device that irradiates linear light extending in a width direction perpendicular to the conveyance direction toward the inspection position;
a screen on which a reflected light image of the linear light reflected on the surface of the measurement object is projected;
an imaging device that captures an image of the screen on which the reflected light image is projected and generates a captured image;
an arithmetic processing device that measures the surface shape of the object to be measured based on the captured image;
Using a shape measuring device with
The position of the illumination device and the angle at which the linear light is irradiated onto the surface of the measurement object viewed from the extending direction of the linear light are determined by the geometry at which the reflected light image is projected onto the screen. an entrance side provisional adjustment step for adjusting to the desired arrangement;
a calibration plate arranging step of arranging a calibration plate having a linear marker on its surface so that the marker matches the inspection position;
an illumination step of irradiating the linear light from the illumination device to the calibration plate;
An angle adjustment step of adjusting the angle of the illumination device with respect to the conveyance direction as seen from the normal direction of the measurement target based on the linear light and the marker;
a position adjustment step of adjusting the position of the illumination device in the transport direction as viewed from the normal direction of the measurement target 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. Before the input side temporary adjustment step,
Based on the amount of deviation between the designed optical axis of the lighting device and the actual optical axis of the lighting device in an in-plane direction perpendicular to the direction along the designed optical axis of the lighting device, The method for calibrating a shape measuring device according to claim 1, comprising a lighting device calibration step of calibrating an actual optical axis of the lighting device. The lighting device calibration step includes:
arranging the test surface and the illumination device so as to face each other so that the designed optical axis of the illumination device and the normal direction of the test surface are in the same direction;
a light image measuring step of measuring a light image appearing on the test surface by the 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 shift amount calculating step of calculating a shift amount of the light image with respect to a designed optical axis of the lighting device based on a distance from the lighting device to the test surface and a position of the light image appearing on the test surface; ,
a calibration step of calibrating the actual optical axis of the lighting device based on the amount of deviation calculated in the amount of deviation calculation step;
The method for calibrating a shape measuring device according to claim 2, comprising: According to claim 3, in the step of calculating the amount of deviation, the amount of deviation is calculated by approximating the relationship between the distance and the position of the optical image on the test surface measured for each distance by a least squares method. Calibration method of the described shape measuring device. The deviation amount calculation step includes calculating an inclination deviation which is an angle between the normal direction of the test surface and the actual optical axis of the illumination device, and a designed irradiation start position of the illumination device in the in-plane direction of the test surface. 5. The method for calibrating a shape measuring device according to claim 3, wherein a displacement deviation that is a difference between the actual irradiation start position of the illumination device and the actual irradiation start position of the illumination device is calculated as the deviation amount.

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