JP6758765B2 - Measurement method and measurement program - Google Patents

Description

The present invention relates to a measuring method and a measuring program, and more particularly to a measuring method and a measuring program for accurately measuring the surface height of a curved object.

As a measuring method for measuring the surface height, surface roughness, three-dimensional shape, etc. of a measurement object, an optical interferometry method using brightness information of interference fringes generated by light interference is known. In the optical interferometry, the peaks of the interference fringes of each wavelength are overlapped and synthesized at the focus position where the optical path length of the reference optical path and the optical path length of the measurement optical path coincide with each other, and the brightness of the interference fringes is increased. Therefore, in the optical interferometry, an interferometric image showing a two-dimensional distribution of the interference light intensity is taken by an imaging element such as a CCD camera while changing the optical path length of the reference optical path or the measurement optical path. Then, by detecting the focus position where the intensity of the interference light peaks at each measurement position in the photographing field, the height of the measurement surface at each measurement position is measured, and the three-dimensional shape of the measurement object is measured. (See, for example, Patent Documents 1 to 3).

Japanese Unexamined Patent Publication No. 2011-191118 Japanese Unexamined Patent Publication No. 2015-045575 Japanese Unexamined Patent Publication No. 2015-118076

However, when the surface of the object to be measured is curved, the measured value includes the curved state of the surface, so that it is difficult to accurately measure the uneven state of the surface, the surface roughness, and the like. .. In particular, when the object to be measured is a cylindrical inner wall surface (for example, the inner wall surface of a cylinder), a part of the inner wall surface is conventionally transferred to a replica agent, and the transferred shape is manually analyzed with a laser microscope or the like. .. In such a manual analysis, the reliability of the inspection and the bias by the inspector become large.

An object of the present invention is to provide a measuring method and a measuring program capable of automatically and accurately measuring the surface of a curved object.

In order to solve the above problems, the present invention is a method of measuring the surface of an object having a curved shape by measuring the distance from the measuring head, and the measurement range of the object and the threshold of unevenness. The process of setting, the process of acquiring shape reference data including the curved shape of the object, and the process of measuring the distance between the object and the measurement head in the measurement range and acquiring the three-dimensional data of the surface of the object. And the process of removing the shape reference data from the three-dimensional data to acquire the curvature removal data, the first reference data is obtained based on the curvature removal data, and the data exceeding the threshold value with respect to the first reference data is obtained from the curvature removal data. It is characterized by including a step of obtaining a second reference data obtained by excluding and averaging, and a step of extracting data exceeding a threshold value with respect to the second reference data from the curvature removal data and obtaining uneven shape data. ..

According to such a configuration, in order to remove the shape reference data including the curved shape from the three-dimensional data acquired for the surface of the object having the curved shape, the data obtained by removing the curved state on the surface of the object (curvature removal). Data) can be obtained. By excluding the data exceeding the threshold value from the first reference data based on the curvature removal data, the second reference data excluding the uneven shape of the surface can be obtained. Then, by performing the threshold value determination again on the second reference data, it is possible to perform highly accurate measurement including the determination of the uneven shape.

The measuring method of the present invention may further include a step of determining the surface roughness of the object by using the data excluding the data exceeding the threshold value from the curvature removal data with respect to the second reference data. This makes it possible to obtain the surface roughness that does not include the curved shape and the uneven shape.

In the measuring method of the present invention, the shape data of the unevenness may include at least one of the area, the area ratio, the volume, the maximum value of the opening, the minimum value of the opening, and the average value of the opening. Further, the surface of the object may be the inner surface of any of a cylinder, a cone, an elliptical cylinder and an elliptical weight. Further, the measuring head may measure the distance by the optical interferometry.

The present invention is a measurement program that measures the surface state of an object by measuring the distance from the measurement head of the object having a curved shape, and means that a computer is used to set a measurement range of the object and a threshold of unevenness. , A means for acquiring shape reference data including the curved shape of the object, a means for measuring the distance between the object and the measurement head in the measurement range, and a means for acquiring three-dimensional data on the surface of the object, and a shape from the three-dimensional data. A means for removing the reference data and acquiring the curvature removal data, the first reference data based on the curvature removal data is obtained, and the second reference data averaged by excluding the data exceeding the threshold from the first reference data from the curvature removal data is obtained. It is a measurement program that functions as a means for obtaining, and a means for obtaining data on the shape of unevenness by extracting data exceeding a threshold value from the second reference data from the curvature removal data.

According to such a configuration, data obtained by removing the curved shape from the three-dimensional data acquired for the surface of the object (curved removal data) is acquired by a computer, and the first reference data based on the curved removal data is obtained. Performs processing to exclude data that exceeds the threshold value. As a result, the second reference data excluding the uneven shape of the surface is obtained. Then, by performing the threshold value determination again on the second reference data, it is possible to calculate a highly accurate measurement result including the determination of the uneven shape.

It is a figure which shows the whole structure of the image measuring apparatus which concerns on this embodiment. It is a schematic diagram which illustrates the structure of the optical interference optical head. It is an enlarged view of the main part of the objective lens part. (A) to (c) are schematic views explaining an object and a measurement area. It is a block diagram which illustrates the structure of a computer. It is a flowchart which illustrates the flow of the measurement program which concerns on this embodiment. (A) and (b) are schematic diagrams illustrating the measurement range. (A) and (b) are schematic diagrams illustrating reference data. (A) and (b) are schematic diagrams illustrating the determination of pits from the reference data.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same members are designated by the same reference numerals, and the description of the members once described will be omitted as appropriate.

[Overall configuration of measuring device]
FIG. 1 is a diagram showing an overall configuration of a measuring device according to the present embodiment, more specifically, an image measuring device.
As shown in FIG. 1, the image measuring device 1 according to the present embodiment includes a device main body 10 that measures the shape of an object W and a computer system 20 that controls the device main body 10 and executes necessary data processing. , Equipped with. In addition to these, the image measuring device 1 may appropriately include a printer or the like that prints out the measurement results and the like. The image measuring device 1 according to the present embodiment is suitable for measuring an object W having a curved shape, such as an inner wall of a cylinder.

The apparatus main body 10 includes a gantry 11, a stage 12, an X-axis guide 14, and an imaging unit 15. In the present embodiment, the X-axis direction (direction along the X-axis) is one direction along the surface of the stage 12. The Y-axis direction (direction along the Y-axis) is a direction along the surface of the stage 12 and orthogonal to the X-axis direction. The Z-axis direction (direction along the Z-axis) is a direction orthogonal to the X-axis direction and the Y-axis direction. The Z-axis direction is also called the vertical direction. Further, the X-axis direction and the Y-axis direction are also referred to as horizontal directions.

The gantry 11 is arranged on, for example, the vibration isolation pedestal 3, and suppresses external vibrations from being transmitted to the stage 12 and the imaging unit 15 on the gantry 11. The stage 12 is arranged on the gantry 11. The stage 12 is a table on which the object W to be measured is placed. The stage 12 is provided so as to be movable in the Y-axis direction with respect to the gantry 11 by a Y-axis drive mechanism (not shown).

Support portions 13a and 13b are provided on both sides of the gantry 11. Each of the support portions 13a and 13b is provided so as to extend upward from the side portion of the gantry 11. The X-axis guide 14 is provided on the support portions 13a and 13b so as to straddle them. An imaging unit 15 is attached to the X-axis guide 14.

The image pickup unit 15 is provided so as to be movable in the X-axis direction along the X-axis guide 14 by an X-axis drive mechanism (not shown), and is provided so as to be movable in the Z-axis direction by a Z-axis drive mechanism. With such a drive mechanism, the relative positional relationship between the object W on the stage 12 and the image pickup unit 15 along the X-axis, Y-axis, and Z-axis can be set. That is, by adjusting this positional relationship, the imaging region by the imaging unit 15 can be adjusted to the measurement region of the object W.

The imaging unit 15 is detachably provided with an image optical head 151 for capturing a two-dimensional image of the object W and an optical interference optical head 152 for measuring the three-dimensional shape of the object W by optical interference measurement, and any of the heads is provided. The object W is measured at the measurement position set by the computer system 20.

The measurement field of view of the image optical head 151 is usually set wider than the measurement field of view of the optical interference optical head 152, and both heads can be switched and used under the control of the computer system 20. The image optical head 151 and the optical interference optical head 152 are supported by a common support plate so as to maintain a constant positional relationship, and are calibrated in advance so that the measurement coordinate axes do not change before and after switching.

The image optical head 151 includes a CCD camera, a lighting device, a focusing mechanism, and the like, and captures a two-dimensional image of the object W. The captured two-dimensional image data is taken into the computer system 20.

The optical interferometry optical head 152 measures the shape of the object W by, for example, the white interferometry. In the present embodiment, the optical interference optical head 152 is an example of a measurement head. Details of the optical interference optical head 152 will be described later.

The computer system 20 includes a computer body 201, a keyboard 202, a mouse 204, and a display 205. The computer main body 201 controls the operation of the device main body 10 and the like. The computer main body 201 controls the operation of the device main body 10 by a circuit (hardware) such as a control board and a program (software) executed by the CPU. Further, the computer main body 201 calculates the information of the object W based on the signal output from the device main body 10, and displays the calculation result on the display 205.

The joystick 203 is used when setting the position for imaging the object W. That is, when the user operates the joystick 203, the relative positional relationship between the object W and the image pickup unit 15 changes, and the position of the image pickup region displayed on the display 205 can be adjusted.

FIG. 2 is a schematic view illustrating the configuration of the optical interference optical head.
As shown in FIG. 2, the optical interference optical head 152 includes a light emitting unit 200, an optical interference optical head unit 21, an objective lens unit 22, a reference mirror unit 23, an imaging lens 24, and an imaging unit 25. , The drive mechanism unit 26 is provided.

The light emitting unit 200 includes a light source that has a large number of wavelength components over a wide band and outputs wide band light having low coherency, and for example, a white light source such as a halogen or an LED (Light Emitting Diode) is used.

The optical interference optical head unit 21 includes a beam splitter 211 and a collimator lens 212. The light emitted from the light emitting unit 200 is emitted from the direction perpendicular to the optical axis of the objective lens unit 22 in parallel to the beam splitter 211 via the collimator lens 212, and the light along the optical axis is emitted from the beam splitter 211. It is emitted and a parallel beam is irradiated to the objective lens unit 22 from above.

The objective lens unit 22 includes an objective lens 221 and a beam splitter 222. In the objective lens unit 22, when a parallel beam is incident on the objective lens 221 from above, the incident light becomes convergent light on the objective lens 221 and is incident on the reflecting surface 222a inside the beam splitter 222. Here, the incident light is transmitted light (reference light) traveling in the reference optical path (broken line in the figure) having the reference mirror 231 and reflected light (measurement light) traveling in the measurement optical path (solid line in the figure) in which the object W is arranged. It is divided into and. The transmitted light converges and is reflected by the reference mirror 231 and further propagates through the reflecting surface 222a of the beam splitter 222. On the other hand, the reflected light converges and is reflected by the object W, and is reflected by the reflecting surface 222a of the beam splitter 222. The reflected light from the reference mirror 231 and the reflected light from the object W are combined by the reflecting surface 222a of the beam splitter 222 to form a composite wave.

The combined wave synthesized at the position of the reflecting surface 222a of the beam splitter 222 becomes a parallel beam by the objective lens 221 and travels upward, passes through the optical interference optical head portion 21, and is incident on the imaging lens 24 (FIG. 2). Middle one-dot chain line). The imaging lens 24 converges the composite wave and forms an interference image on the imaging unit 25.

The reference mirror unit 23 holds a reference mirror 231 that reflects transmitted light (reference light) traveling in the reference optical path branched by the beam splitter 222 described above. When the object W is the inner wall of the cylinder, the inner wall surface is arranged substantially perpendicular to the stage 12. Therefore, the focused light from the objective lens 221 is reflected at a right angle (horizontally) by the beam splitter 222, and the measurement light is applied to the inner wall surface of the vertically arranged cylinder.

The image pickup unit 25 is a CCD camera or the like including a two-dimensional image pickup element for forming an image pickup means, and is a composite wave output from the objective lens unit 22 (reflected light from the object W and reflected from the reference mirror 231). The interference image of light) is taken. The data of the captured image is taken into the computer system 20.

The drive mechanism unit 26 moves the optical interference optical head 152 in the optical axis direction in response to a movement command from the computer system 20. Here, in the enlarged view of the main part of the objective lens unit 22 shown in FIG. 3, when the optical path lengths of the reference optical path (optical path 1 + optical path 2) and the measurement optical path (optical path 3 + optical path 4) are equal, the optical path length difference is 0. Become. Therefore, in the measurement, the drive mechanism unit 26 moves the optical interference optical head 152 horizontally in the optical axis direction of the light beam reflected by the beam splitter 222 so that the optical path length difference is 0, so that the length of the optical path is measured. Adjust the light. In the above description, the case where the optical interference optical head 152 is moved has been described as an example, but the length of the measurement optical path may be adjusted by moving the stage 12. In this way, in the optical interference optical head 152, the optical path length of either the reference optical path or the measurement optical path is variable. When the measurement surface of the object W is arranged in the horizontal direction, an optical system that allows the measurement light to be transmitted in the vertical direction by reversing the transmission and reflection of the reference light and the measurement light by the beam splitter 222. May be applied.

Under the control of the computer system 20, the optical interference optical head 152 repeats imaging by the imaging unit 25 while being moved and scanned by the drive mechanism unit 26 at a position in the optical axis direction. The image data of the interference image at each moving scanning position captured by the imaging unit 25 is taken into the computer system 20, and at each position in the measurement field, the moving scanning position where the peak of the interference fringe occurs is detected, and the object W The height at each position of the measurement surface of is obtained.

4 (a) to 4 (c) are schematic views illustrating an object and a measurement area.
FIG. 4A is a schematic perspective view showing an example of an object W having a curved shape, FIG. 4B is a schematic view illustrating a measurement region, and FIG. 4C is a three-dimensional data and a cross section. It is a schematic diagram which shows an example.
In the present embodiment, the shape of the object W having a curved shape such as the inner wall of the cylinder shown in FIG. 4A is measured. The optical interference optical head 152 measures a distance in a direction perpendicular to the inner wall surface S, with a predetermined region of the inner wall surface S as a measurement area R. In FIG. 4B, one of the measurement regions R is schematically shown.

As shown in FIG. 4C, the three-dimensional data of the inner wall surface S includes the direction (depth direction) perpendicular to the inner wall surface S for each pixel of the imaging unit 25 corresponding to the measurement area R. Contains distance data. If there is a pit (dent) on the inner wall surface S, for example, the data will be lower than the reference surface. If this data is lower than the threshold value, it is judged to be a pit.

[Measurement method and measurement program]
The measuring method according to the present embodiment is, for example, a method of measuring the surface of an object W having a curved shape as shown in FIG. 4A by using the image measuring device 1 as described above.
The measuring method has the following steps.
(1) Step of setting the measurement area R of the object W and the threshold value of the unevenness (2) Step of acquiring shape reference data including the curved shape of the object W (3) The object W and the measurement head in the measurement area R ( Step of measuring the distance from the optical interference optical head 152) and acquiring the three-dimensional data of the surface of the object W (4) The step of removing the shape reference data from the three-dimensional data and acquiring the curvature removal data (5) ) The process of obtaining the first reference data based on the curvature removal data, excluding the data exceeding the threshold from the first reference data from the curvature removal data, and obtaining the average second reference data (6) For the second reference data The process of extracting data that exceeds the threshold and obtaining the shape data of the unevenness

Each of the above steps (1) to (6) is executed by, for example, a program (measurement program) executed by the computer system 20 of the image measuring device 1 or a computer reading the three-dimensional data acquired by the device main body 10. To. The computer may be included in the computer system 20.

FIG. 5 is a block diagram illustrating the configuration of a computer. The computer includes a CPU (Central Processing Unit) 311, an interface 312, an output unit 313, an input unit 314, a main storage unit 315, and a sub storage unit 316.

The CPU 311 controls each part by executing various programs. The interface 312 is a part that inputs / outputs information to / from an external device. In the present embodiment, the information sent from the apparatus main body 10 is taken into the computer via the interface 312. Further, information is sent from the computer to the apparatus main body 10 via the interface 312. The interface 312 is also a part that connects a computer to a LAN (Local Area Network) or WAN (Wide Area Network).

The output unit 313 is a part that outputs the result processed by the computer. For the output unit 313, for example, the display 205 shown in FIG. 1 or a printer is used. The input unit 314 is a part that receives information from the user. A keyboard, mouse, or the like is used for the input unit 314. Further, the input unit 314 includes a function of reading the information recorded on the recording medium MM.

For the main storage unit 315, for example, a RAM (Random Access Memory) is used. As a part of the main storage unit 315, a part of the sub storage unit 316 may be used. For the sub-storage unit 316, for example, an HDD (Hard disk drive) or an SSD (Solid State Drive) is used. The sub-storage unit 316 may be an external storage device connected via a network.

FIG. 6 is a flowchart illustrating the flow of the measurement program according to the present embodiment.
The measurement program according to the present embodiment causes the computer to function as a means corresponding to the above steps (1) to (6). The processes of steps S101 to S106 shown in FIG. 6 correspond to the steps (1) to (6) above.

First, as shown in step S101, the measurement range and the threshold value are set. FIG. 7A schematically shows the measurement region R of the inner wall of the cylinder. The measurement area R of the inner wall of the cylinder is set by designating the angle of the cylinder axis and the position of the depth in the direction of the cylinder axis. Further, as a threshold value setting for the unevenness of the inner wall of the cylinder, for example, a threshold value for the depth of the pit is set.

When the measurement area R exceeds the measurable range in one scan by the measurement head (for example, the optical interference optical head 152), the measurement positions of a plurality of local data are calculated in order to cover the entire measurement area R. I will do it. FIG. 7B schematically shows the correspondence between the measurement region R on the inner wall of the cylinder and the plurality of local data.

Next, as shown in step S102, the shape reference data is acquired. The shape reference data is data representing a shape including a curved shape of the object W. For example, as shown in FIG. 8A, when the object W is the inner wall of a cylinder, the shape reference data is data of elements (inclination of the cylinder axis, diameter of the cylinder) for expressing the cylinder shape. In the present embodiment, the image optical head 151 is attached to the image pickup unit 15, the object W is imaged by the image optical head 151, and the shape reference data is acquired. In the case of the inner wall of a cylinder, the data of the circle is obtained by measuring three points on the edge of the cylinder, and the diameter of the cylinder is calculated. In addition, the data of two circles are obtained in the depth direction, and the slope of the cylindrical axis is obtained by the line connecting the centers of each circle. In order to acquire the shape reference data, a touch probe may be used in addition to the image optical head 151.

Next, as shown in step S103, three-dimensional data is acquired. In the present embodiment, the image optical head 151 mounted on the image pickup unit 15 is switched to the optical interference optical head 152, the distance between each measurement point and the measurement head in the measurement area R is measured by the optical interference optical head 152, and the measurement area is measured. Acquire the three-dimensional data of R.

Next, as shown in step S104, the curvature removal data is acquired. That is, the curvature removal data is obtained by removing the shape reference data acquired in step S102 from the three-dimensional data of the measurement area R acquired in step S103. As a result, the curvature component of the measurement region R is removed from the three-dimensional data. FIG. 8B schematically shows a method of acquiring curvature removal data. The three-dimensional data also includes the curvature component of the measurement region R. The shape reference data can be said to be ideal three-dimensional shape data for the measurement range. By subtracting the shape reference data from the measured three-dimensional data, data obtained by removing the curvature component from the measured value (curvature removal data) can be obtained. The curvature removal data is data obtained by apparently flattening three-dimensional data of an object including a curved shape.

When the measurement area R is composed of a plurality of local data, the curvature removal data obtained for each local data is combined (stitched). When combining, if overlapping regions occur in adjacent local data, deduplication is performed. As a result, the entire curvature removal data of the measurement region R is constructed.

Next, as shown in step S105, the reference data is calculated. First, the first reference data based on the curvature removal data obtained in step S104 is obtained. The first reference data is the average depth of all measurement point groups of the curvature removal data. Further, as the first reference data, an approximate plane obtained by subjecting the curvature removal data to a predetermined filter process and obtaining the filtered data may be used. FIG. 9A schematically shows the first reference data obtained from the curvature removal data of the measurement region R. In the measurement area R, the first reference data is planar data. The direction orthogonal to the plane of the first reference data is the depth direction.

After calculating the first reference data, the data exceeding the threshold value (threshold value of unevenness set in step S101) is excluded from the first reference data from the curvature removal data, and the second reference data which is the average value is obtained. calculate. The second reference data is an average value excluding the data determined to be uneven from the first reference data.

FIG. 9B schematically shows the range of pits excluded from the first reference data. Here, among the points having data exceeding the threshold value from the first reference data (black circles in the figure), the range closed in the plane direction (the range in which the points exceeding the threshold value are continuous in the plane direction) is determined as a pit. Then, the data of the region determined to be a pit is excluded from the curvature removal data. The second reference data obtained by excluding the pit data and calculating the average is the data representing the reference plane not affected by the pit.

Next, as shown in step S106, the shape data is calculated. That is, data exceeding the threshold value is extracted from the second reference data from the curvature removal data to obtain uneven shape data. For example, when determining a pit, as in the case of determining a pit described above, a range of points having data exceeding a threshold value from the second reference data, which is closed in the plane direction, is determined as a pit. By determining the pit, the area, area ratio, volume, and opening (maximum value, minimum value, average value, etc. of the opening) of the pit can be calculated. Further, the surface roughness can be calculated by using the data of the region other than the pit.

As described above, in the measurement program according to the present embodiment, other than the setting of the measurement area R and the threshold value shown in step S101 (steps S102 to S106) can be automatically performed. Therefore, it is possible to automatically obtain a stable measurement result regardless of the proficiency level of the operator.

As described above, according to the present embodiment, when the surface of the curved object W is measured, it is possible to suppress the influence of the curved shape and the unevenness of the surface and automatically perform the surface measurement with high accuracy. It becomes.

Here, the measurement program according to the present embodiment described above may be recorded on a computer-readable recording medium MM. That is, a part or all of steps S101 to S106 shown in FIG. 6 may be recorded on the recording medium MM in a computer-readable format. Further, the measurement program according to the present embodiment may be distributed via a network.

Although the present embodiment has been described above, the present invention is not limited to these examples. For example, although the optical interferometry optical head 152 by the white light interferometry is used as the measurement head, it can also be applied to an image probe or a laser probe.
Further, in the above embodiment, the object W to be measured has been described by taking a curved surface having a recess (pit) as an example, but the object to which the present invention is applicable is not limited to this. For example, the present invention is also applicable when the inner wall surface of a cylinder in which a crosshatch (net-like groove) is formed by honing is used as an object W. Further, as the measurement head, the image optical head 151 is scanned in the optical axis direction of the light irradiating the object W, and the peak of the contrast at each pixel of the CCD is detected from the continuously acquired images, whereby the object W 3 PFF (Points From Focus) for obtaining a three-dimensional shape is also applicable. Further, as the object W, it is possible to measure the surface of various curved shapes such as a cone, an elliptical cylinder, and an elliptical weight other than the cylinder, and the plane shape having no curved shape. Further, those skilled in the art appropriately adding, deleting, or changing the design of each of the above-described embodiments, or those appropriately combining the features of each embodiment also have the gist of the present invention. As long as it is included in the scope of the present invention.

1 ... Image measuring device 3 ... Vibration isolator 10 ... Device main body 11 ... Stand 12 ... Stage 13a ... Support 14 ... X-axis guide 15 ... Imaging unit 20 ... Computer system 21 ... Optical interference optical head 22 ... Objective lens 23 ... Reference mirror unit 24 ... Imaging lens 25 ... Imaging unit 26 ... Drive mechanism unit 151 ... Image optical head 152 ... Optical interference optical head 200 ... Light emitting unit 201 ... Computer body 202 ... Keyboard 203 ... Joystick 204 ... Mouse 205 ... Display 211 ... Beam splitter 212 ... Collimeter lens 221 ... Objective lens 222 ... Beam splitter 222a ... Reflection surface 231 ... Reference mirror 311 ... CPU
312 ... Interface 313 ... Output unit 314 ... Input unit 315 ... Main storage unit 316 ... Sub storage unit MM ... Recording medium R ... Measurement area S ... Inner wall surface W ... Object

Claims (6)

A method of measuring the surface of an object having a curved shape by measuring the distance from the measuring head.
The step of setting the measurement range of the object and the threshold value of the unevenness, and
The process of acquiring shape reference data including the curved shape of the object, and
A step of measuring the distance between the object and the measuring head in the measuring range and acquiring three-dimensional data on the surface of the object.
The process of removing the shape reference data from the three-dimensional data and acquiring the curvature removal data,
A step of obtaining the first reference data based on the curvature removal data, excluding data exceeding the threshold value from the first reference data from the curvature removal data, and obtaining an average second reference data.
A step of extracting data exceeding the threshold value from the curvature removal data with respect to the second reference data to obtain uneven shape data, and
A measurement method characterized by being equipped with. The measuring method according to claim 1, further comprising a step of obtaining the surface roughness of the object by using the data obtained by excluding the data exceeding the threshold value from the bending removal data with respect to the second reference data. The measuring method according to claim 1 or 2, wherein the shape data of the unevenness includes at least one of the area, area ratio, volume, maximum value of the opening, minimum value of the opening, and average value of the opening. The measuring method according to any one of claims 1 to 3, wherein the surface of the object is an inner surface of any one of a cylinder, a cone, an elliptical cylinder and an elliptical weight. The measuring method according to any one of claims 1 to 4, wherein the measuring head measures the distance by an optical interferometry. A measurement program that measures the surface condition of an object having a curved shape by measuring the distance from the measurement head.
Computer,
A means for setting the measurement range of the object and the threshold value of the unevenness,
Means for acquiring shape reference data including the curved shape of the object,
A means for measuring the distance between the object and the measuring head in the measuring range and acquiring three-dimensional data on the surface of the object.
A means for obtaining curvature removal data by removing the shape reference data from the three-dimensional data.
A means for obtaining first reference data based on the curvature removal data, excluding data exceeding the threshold value from the first reference data from the curvature removal data, and obtaining averaged second reference data.
A means for obtaining uneven shape data by extracting data exceeding the threshold value from the second reference data from the bending removal data.
A measurement program that functions as.

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