Non-contact surface property evaluation device and non-contact surface property evaluation method

Abstract

Provided is a non-contact-type surface property evaluation device that is easy to use and can be miniaturized. This surface property evaluation device comprises: a light irradiation unit that irradiates an object to be measured; a reflected light detection sensor that receives and detects reflected light from the object to be measured; an observation distance measurement means that measures an observation distance, which is the distance between the object to be measured and the reflected light detection sensor; and a corrected evaluation parameter calculation unit that obtains a corrected evaluation parameter, for evaluating the spread of reflected light at a predetermined reference observation distance, by correcting the spread of the reflected light, actually measured by the reflected light detection sensor, on the basis of the observation distance. The surface roughness of the object to be measured is evaluated on the basis of the corrected evaluation parameter.

Description

Non-contact surface texture evaluation device and non-contact surface texture evaluation method

[0001] The present invention relates to a non-contact surface texture evaluation device, for example, a non-contact surface roughness evaluation device.

[0002] 2. Description of the Related Art Non-contact surface roughness measuring instruments are known that irradiate the surface of an object to be measured with light and measure the surface properties of the object by detecting the reflected light.

[0003] Patent 5084398, Patent Publication 2006-58224, Patent 2946381

[0004] When the working distance changes, the distance from the workpiece to the light-receiving unit changes. When reflected light travels at a scattering angle, the size of the scattered light image projected onto the light-receiving unit changes depending on the distance from the workpiece to the light-receiving unit. Therefore, even when measuring the same workpiece, the appearance of the image will change depending on the working distance, resulting in differences in the calculated surface roughness. For this reason, the working distance must be precisely adjusted, but there are limits to how much adjustment can be made and it takes time, which results in a problem of not improving measurement efficiency.

[0005] One solution is to use a lens to focus the reflected light (Patent Documents 2 and 3). Lenses have the property of focusing light incident at a certain angle at a position corresponding to the angle (the principle of autocollimation). Even if the working distance changes, the angle of the light rays incident on the lens does not change, so the image size on the focal plane remains constant. However, this requires the incorporation of a large lens that can capture all of the reflected light, which inevitably makes the system large and expensive.

[0006] An object of the present invention is to provide a non-contact surface texture evaluation device that is easy to use and can be made compact.

[0007] A non-contact surface texture evaluation device according to one embodiment of the present invention comprises a light irradiation unit that irradiates a measurement object with light, a reflected light detection sensor that receives and detects reflected light from the measurement object, an observation distance measurement unit that measures an observation distance, which is the distance between the measurement object and the reflected light detection sensor, and a corrected evaluation parameter calculation unit that calculates a corrected evaluation parameter for evaluating the spread of the reflected light at a predetermined reference observation distance by correcting the spread of the reflected light actually measured by the reflected light detection sensor based on the observation distance, and evaluates the surface roughness of the measurement object based on the corrected evaluation parameter.

[0008] FIG. 1 is a diagram for explaining the configuration of a surface texture measuring device according to a first embodiment. FIG. 2 is a functional block diagram of a data processing unit. FIG. 3 is a diagram showing an example of the relationship between evaluation parameters and surface texture (surface roughness). FIG. 4 is a diagram illustrating a second embodiment. FIG. 5 is a diagram illustrating a third embodiment. FIG. 6 is a diagram illustrating a fourth embodiment. FIG. 7 is a diagram for explaining the fourth embodiment.

[0009] The present invention will be described with reference to the drawings and the reference numerals assigned to the elements in the drawings. Each embodiment may be implemented alone or in combination with two or more embodiments, and the modifications supplemented in each embodiment may also be applied to other embodiments.

[0010] First Embodiment A first embodiment of the present invention will be described below. Fig. 1 is a diagram for explaining the configuration of a surface texture measuring device according to the first embodiment of the present invention.

[0011] The surface texture measuring device 100 includes a stage 110 and a non-contact surface texture sensor head 200. The non-contact surface texture sensor head 200 is sometimes called a non-contact surface texture probe.

[0012] The stage 110 is a platform on which the measurement object W is mounted.

[0013] The non-contact surface texture sensor head 200 measures the surface texture, for example, surface roughness, of a measurement object W set on the stage 110 in a non-contact manner. The non-contact surface texture sensor head 200 is not fixedly positioned relative to the stage 110, and the position and height of the non-contact surface texture sensor head 200 can be appropriately adjusted by an operator's hand or by some other mechanism. When measuring the surface roughness of a measurement object using the non-contact surface texture sensor head 200, it is preferable to adjust the relative orientation of the non-contact surface texture sensor head 200 and the stage 110 (i.e., the surface of the measurement object W) so that they face each other directly. On the other hand, there is no particular restriction on the distance between the non-contact surface texture sensor head 200 and the stage 110 (i.e., the surface of the measurement object W), and strict adjustment is not necessary.

[0014] The non-contact surface texture sensor head 200 includes a light emitting unit 210 , a reflected light detection sensor 220 , an observation distance measuring unit 230 , and a data processing unit 240 .

[0015] The light irradiation unit 210 irradiates the surface of the measurement object W with light. The light irradiation unit 210 may be a white LED. A laser light source may also be used, but it is not essential that the light be coherent. The light irradiation unit 210 preferably focuses parallel light using a pinhole and irradiates the surface of the measurement object W with spot light by epi-illumination. Here, the light emitted from the light irradiation unit 210 is deflected by a half mirror 211 and irradiated perpendicularly to the surface of the measurement object W. This allows spot light to be irradiated onto the surface of the measurement object with epi-illumination.

[0016] The reflected light detection sensor 220 receives and detects the reflected light that is reflected back from the surface of the measurement object W. The reflected light detection sensor 220 here is an image sensor, such as a two-dimensional CCD image sensor or a CMOS image sensor.

[0017] This image sensor is referred to as a first image sensor 220, and is distinguished from an image sensor (second image sensor 311) for measuring an observation distance in a second embodiment described later.

[0018] In addition, since the reflected light detection sensor 220 only needs to be able to detect the spread of light, it may be possible to detect the spread of light by one-dimensionally or two-dimensionally scanning a single-point detection optical sensor such as a photodiode. Alternatively, a line sensor may be used to detect only the one-dimensional direction of the spread of light, or the line sensor may be scanned to detect the spread of light two-dimensionally.

[0019] If the light spread is detected one-dimensionally, the device can be made smaller while obtaining surface characteristics corresponding to one direction, whereas if the light spread is detected two-dimensionally, surface characteristics corresponding to two directions can be obtained.

[0020] It is assumed that there is no lens between the reflected light detection sensor 220 and the surface of the measurement object W that collects all of the reflected light and guides it to the reflected light detection sensor 220 .

[0021] The observation distance measurement unit 230 measures the distance to the surface of the measurement object. As the observation distance measurement unit 230, an optical distance measuring device capable of measuring distance without contact may be used. The measurement principle is not limited to a phase difference method, a pulse method, triangulation, or the like. In this embodiment, a TOF sensor is used as an example of the observation distance measurement unit 230. Here, the observation distance measurement unit 230 and the reflected light detection sensor 220 are arranged side by side with their heights aligned so that the measured distance acquired by the observation distance measurement unit 230 directly corresponds to the distance between the reflected light detection sensor 220 and the surface of the measurement object (observation distance, working distance). Of course, there may be a known height difference (or optical path difference) between them.

[0022] 2 is a functional block diagram of the data processing unit 240. The data processing unit 240 evaluates the surface roughness of the measurement object based on the spread of reflected light acquired by the reflected light detection sensor 220. The data processing unit 240 includes a light intensity distribution acquisition unit 241, an observation distance acquisition unit 242, a corrected evaluation parameter calculation unit 244, and a surface texture evaluation unit 245.

[0023] The light intensity distribution acquisition unit 241 acquires sensor data from the reflected light detection sensor 220 and obtains the distribution of reflected light. Here, since the reflected light detection sensor 220 is two-dimensional, the light intensity distribution I(x, y) of reflected light is obtained, for example. To make it easier to understand that these are actual measured values ​​before correction, the light intensity distribution of reflected light based on the actual measured values ​​is represented by Im.

[0024] The observation distance acquisition unit 242 obtains the distance (working distance, observation distance) between the reflected light detection sensor 220 and the surface of the object to be measured from the distance measurement value measured by the observation distance measurement unit 230. The distance between the reflected light detection sensor 220 and the surface of the object to be measured is defined as the observation distance Zm.

[0025] The corrected evaluation parameter calculation unit 244 calculates evaluation parameters for evaluating the surface roughness. That is, the corrected evaluation parameter calculation unit 244 performs correction taking into account the observation distance, and calculates corrected evaluation parameters for evaluating the surface roughness according to the observation distance.

[0026] Previous research evaluating surface roughness from the spread of light reflected from an object surface is already known, and it is also known that surface roughness can be evaluated from the magnitude of the spread of reflected light and the intensity distribution of reflected light. Here, the magnitude of the spread of reflected light, R, is used as the evaluation parameter for surface roughness. If the radius from the point of incidence of specularly reflected light to the edge of the reflected light (scattered light) is r, then the magnitude of the spread of reflected light, R, is 2r (R = 2r). Instead of approximating it to a circle, the maximum diameter across the light spot (which can also be considered the maximum inner diameter) can be used as the magnitude of the spread of reflected light, R. Since the greater the surface roughness, the stronger the light scattering phenomenon, so surface roughness can be evaluated by the magnitude of the spread of reflected light.

[0027] An example of a procedure for calculating the corrected evaluation parameter will be described. First, the corrected evaluation parameter calculation unit 244 obtains the magnitude R of the spread of the reflected light as an actual measurement value from the light intensity distribution Im of the reflected light actually measured by the reflected light detection sensor 220. The magnitude R of the spread of the reflected light as an actual measurement value is defined as Rm.

[0028] Next, the corrected evaluation parameter calculation unit 244 corrects the actual measurement value of the spread of the reflected light Rm based on the observation distance Zm to obtain the spread of the reflected light Rrev at a predetermined reference observation distance (Zs). The spread of the reflected light R corrected according to the observation distance is the corrected evaluation parameter Rrev.

[0029] The reference observation distance (Zs) may be, for example, 50 cm or 100 cm, and may be any value determined as appropriate. For example, the corrected evaluation parameter Rrev can be obtained by correcting the magnitude of the spread of reflected light Rm, which is an actually measured value, by the ratio (γ=Zs / Zm) between the reference observation distance (Zs) and the actual observation distance (Zm). Rrev=Rm×γ

[0030] The surface texture evaluation unit 245 evaluates the surface roughness of the measurement target W from the corrected evaluation parameter (Rrev) calculated by the corrected evaluation parameter calculation unit 244. A sample workpiece with a known roughness is observed at a standard observation distance (Zs) to determine the spread R of the reflected light, and the relationship between the roughness and the spread R of the reflected light is prepared as an evaluation table or evaluation formula. Alternatively, it may be determined by simulation calculation without using an actual sample.

[0031] For example, it has been reported that there is a positive correlation between roughness (Ra) and the extent R of the spread of reflected light, as shown in Figure 3. The surface texture evaluation unit 245 applies the corrected evaluation parameter (Rrev) calculated by the corrected evaluation parameter calculation unit 244 to an evaluation table or an evaluation formula to obtain a roughness evaluation value of the surface of the object to be measured. Note that this is just one example, and other parameters such as the standard deviation of the light intensity distribution and the average intensity of the received reflected light may also be used alone or in appropriate combination.

[0032] According to this embodiment, a corrected evaluation parameter is calculated by correcting an actual measurement value to a value at a reference observation distance based on the observation distance. Therefore, when measuring the surface roughness of a measurement object using the non-contact surface texture sensor head 200, there is no need to take the time to precisely adjust the distance (observation distance, working distance) between the non-contact surface texture sensor head 200 and the stage 110 (i.e., the surface of the measurement object). Furthermore, there is no need to worry about errors in roughness measurement due to deviations in the observation distance (working distance). In other words, improvements in measurement efficiency and measurement accuracy can be achieved simultaneously.

[0033] There is no need for a large lens between the reflected light detection sensor 220 and the surface of the object to be measured W to collect all of the reflected light and direct it to the reflected light detection sensor 220, which makes it possible to make the entire device smaller and less expensive.

[0034] Second Embodiment As a second embodiment, a configuration in which the observation distance measurement unit 230 uses triangulation is shown in Fig. 4. The observation distance measurement unit 230 is composed of a condenser lens 310 and a second image sensor 311 installed at an angle. Here, a light irradiation unit 210 that generates scattered light is used as the light source of the observation distance measurement unit 230.

[0035] The observation distance can be determined from the image formation position on the second image sensor 311. With this configuration, the observation distance measurement unit 230 can share the reflected light detection sensor 220 and the light irradiation unit 210, which allows for a reduction in the number of parts and size of the entire device.

[0036] In order to evaluate the surface texture (surface roughness), it is desirable for the first image sensor 220 to receive as much of the geometrically-optically reflected light from the surface of the measurement object as possible. Therefore, the observation distance measurement unit 230 (condenser lens 310, second image sensor 311) is preferably installed so as to receive only the component with a large scattering angle. For example, the optical axis of the condenser lens 310 is preferably installed at an angle of 40° or more with respect to the incident light beam incident on the surface of the measurement object from the light irradiation unit 210. Although the component of light with a large reflection angle (power) may be small, the condenser lens 310 can collect the light, allowing distance measurement. Note that the size of the condenser lens 310 need only be large enough to perform triangulation; a large lens that can capture all of the reflected light is not necessary.

[0037] If the reflected light received by the first image sensor 220 is insufficient by the amount of light received by the observation distance measurement unit 230, this can be resolved as follows: If the observation distance measurement unit 230 is installed on the plus X side of the first image sensor 220, the data on the minus X side in the first image sensor 220 can be used to interpolate the data on the plus X side.

[0038] Third Embodiment In a third embodiment, the observation distance measurement unit 230 not only shares the light irradiation unit 210 but also the image sensor (first image sensor 220) of the reflected light detection sensor 220. FIG. 5 shows the third embodiment. In FIG. 5, multiple small lenses 410 or pinholes are used as the observation distance measurement unit 230. Here, two small lenses 410 are spaced apart, leaving a gap equal to the width of the optical path through which reflected light passes. As shown by comparing A and B in FIG. 5, when the observation distance changes, the spacing between the spots (bright points) formed by the two small lenses 410 on the first image sensor 220 changes. Therefore, the observation distance can be calculated. According to the third embodiment, components can be further shared, reducing the number of components and miniaturizing the entire device.

[0039] Although the two small lenses 410 are arranged on opposite sides of the optical path for the reflected light, it is not essential to arrange them on opposite sides of the optical path.

[0040] Fourth Embodiment In a fourth embodiment, a lens may be used to measure the change in the spacing between points (dark or bright points) through the lens. FIG. 6 illustrates the fourth embodiment. In FIG. 6, the observation distance measurement unit 230 includes multiple opaque sections 520. A light-transmitting thin plate 510, such as glass, is disposed in front of the first image sensor 220. Two opaque sections 520 are spaced apart from each other on the light-transmitting thin plate 510. A lens 530 is disposed between the light-transmitting thin plate 510 and the first image sensor 220. This lens 530 does not need to capture all of the reflected light; it may be large enough to cover the two opaque sections 520. The light source of the observation distance measurement unit 230 is configured such that light from the light irradiator 210 is deflected by a half mirror 540 and irradiated perpendicularly onto the surface of the object to be measured, thereby providing epi-illumination of the surface of the object. However, the light source of the observation distance measurement unit 230 may be provided separately from the light irradiator 210.

[0041] 7, when the observation distance changes, the interval between the spots (dark points) formed by the two opaque portions 520 changes on the first image sensor 220. Therefore, the observation distance can be determined.

[0042] If the interval between the opaque portions 520 is d, the interval between the dark portions on the image sensor 220 is s, and the focal length of the lens 530 is f, the distance Zo from the opaque portion 520 to the surface of the object to be measured can be expressed as follows: Zo=(f×d) / s

[0043] As shown in Figure 6, if the angle of reflection of the light ray reflected by the opaque area is set to α, the following three equations can be written, and the above equation holds true: (d / 2) / Zo = tanα (s / 2) / f = tanα (s / 2) / f = (d / 2) / Zo

[0044] Once the distance Zo from the opaque portion to the surface of the object to be measured is obtained, the spread of reflected light can be corrected according to the observation distance to obtain corrected evaluation parameters, just as in the first embodiment.This makes it possible to provide a small, relatively inexpensive non-contact surface texture evaluation device that is simple in that it does not require adjustment of the observation distance.

[0045] In Figure 6, opaque section 520 is provided on light-transmitting thin plate 510, but conversely, multiple light-transmitting sections (holes or transparent sections) may be provided on a light-impermeable thin plate, and the observation distance may be obtained from the change in the spacing between the bright spots.

[0046] The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the invention.

[0047] In the above embodiment, when calculating the corrected evaluation parameter, first, the evaluation parameter (Rm) is obtained from the measured light intensity distribution, and then the corrected evaluation parameter Rrev is obtained by performing a correction calculation based on the observation distance. This order may be reversed. That is, first, a corrected intensity distribution may be obtained by correcting the measured light intensity distribution based on the observation distance, and then the evaluation parameter (i.e., the corrected evaluation parameter) Rrev may be obtained from the corrected light intensity distribution. For example, the corrected intensity distribution Irev can be obtained by reordering the coordinates of the measured light intensity distribution Im from (x, y) to (γx, γy).

[0048] Furthermore, when evaluating surface roughness in each direction, such as the surface roughness in the X direction and the surface roughness in the Y direction, the magnitude of spread of reflected light in the X direction Rx and the magnitude of spread of reflected light in the Y direction Ry may be treated separately according to each evaluation direction.

[0049] Instead of using the diameter of the reflected light itself as the spread of the reflected light, the variance and standard deviation (σ) of the reflected light distribution when it is treated as a Gaussian distribution may be calculated, and the variance and standard deviation (σ) of the light intensity distribution may be used as the evaluation parameter for surface roughness. In other words, the standard deviation (σ) of the light intensity distribution, which indirectly represents the degree of spread of light, may be used as the evaluation parameter. The standard deviation σx in the x direction and the standard deviation σy in the y direction may be calculated as standard deviations about the two orthogonal principal axes of the two-dimensional Gaussian function. The variance and standard deviation (σrev) of the light intensity distribution may be calculated based on the corrected intensity distribution Irev and used as the corrected evaluation parameter (σrev). Alternatively, the variance and standard deviation (σm) of the actually measured light intensity distribution Im may be calculated and corrected based on the observation distance to obtain the corrected evaluation parameter (σrev).

[0050] The entire data processing unit may be incorporated into the non-contact surface texture sensor head unit, for example, as a microcomputer chip. Alternatively, all or some of the functional units of the data processing unit may be provided as a computer (arithmetic unit) separate from the non-contact surface texture sensor head. The arithmetic processing in the data processing unit 240 (acquisition of light intensity distribution, acquisition of observation distance, calculation of corrected evaluation parameters, and surface texture evaluation) may be performed by a so-called computer having a CPU (central processing unit) and ROM and RAM storing predetermined programs. Alternatively, the non-contact surface texture evaluation program may be executed by a computer to realize the respective functional units of light intensity distribution acquisition, acquisition of observation distance, calculation of corrected evaluation parameters, and surface texture evaluation. The method of providing the non-contact surface texture evaluation program is not limited. The program may be installed by directly inserting a (non-volatile) recording medium containing the program into the computer. Alternatively, the program may be installed into the computer from an external reader attached to the computer, or the program may be provided to the computer via a communication line such as the Internet, a LAN cable, or a telephone line, or wirelessly.

[0051] The following additional notes are provided regarding the above-described embodiments.

[0052] (Supplementary Note 1) A non-contact surface texture evaluation device comprising: a light irradiation unit that irradiates a measurement object with light; a reflected light detection sensor that receives and detects reflected light from the measurement object; an observation distance measurement unit that measures an observation distance, which is the distance between the measurement object and the reflected light detection sensor; and a corrected evaluation parameter calculation unit that obtains a corrected evaluation parameter that evaluates the spread of the reflected light at a predetermined reference observation distance by correcting the spread of the reflected light actually measured by the reflected light detection sensor based on the observation distance, and that evaluates the surface roughness of the measurement object based on the corrected evaluation parameter.

[0053] (Supplementary Note 2) In the non-contact surface texture evaluation device described in Supplementary Note 1, the reflected light detection sensor and the observation distance measurement means share one light irradiation unit, and the observation distance measurement means measures the observation distance using a portion of the reflected light.

[0054] (Supplementary Note 3) The non-contact surface texture evaluation device according to Supplementary Note 1, wherein the distance measurement by the observation distance measurement means is a triangulation method.

[0055] (Appendix 4) In the non-contact surface texture evaluation device described in Appendix 1, the reflected light detection sensor and the observation distance measurement means share one of the light irradiation units, the distance measurement by the observation distance measurement means is a triangulation method, and the observation distance measurement means measures the observation distance using a portion of the reflected light.

[0056] (Appendix 5) The non-contact surface texture evaluation device according to Appendix 1, wherein the reflected light detection sensor and the observation distance measurement means share one light irradiation unit, and further, the reflected light detection sensor and the observation distance measurement means share one image sensor that receives reflected light from the measurement object, and the observation distance measurement means measures the observation distance using a portion of the reflected light.

[0057] (Appendix 6) In the non-contact surface texture evaluation device described in Appendix 5, the observation distance measurement means has two or more lenses or pinholes arranged at a fixed distance from the image sensor, and the observation distance measurement means obtains the observation distance based on the distance between spots generated on the image sensor through the two or more lenses or pinholes.

[0058] (Appendix 7) In the non-contact surface texture evaluation device described in Appendix 5, the observation distance measurement means has a lens that is provided with a fixed distance from the image sensor and two or more opaque portions or light-transmitting portions, and the observation distance measurement means obtains the observation distance based on the distance between dark portions or light portions created on the image sensor by the two or more opaque portions or light-transmitting portions.

[0059] (Appendix 8) In the non-contact surface texture evaluation device described in Appendix 1, the observation distance measurement means has a lens that is arranged at a fixed distance from an image sensor and two or more opaque or light-transmitting portions, and the observation distance measurement means obtains the observation distance based on the distance between dark or light portions that are produced on the image sensor by the opaque or light-transmitting portions when a portion of the reflected light is imaged on the image sensor through the lens.

[0060] (Appendix 9) A non-contact surface texture evaluation method comprising: irradiating a measurement object with light; receiving and detecting reflected light from the measurement object with a reflected light detection sensor; measuring an observation distance that is a distance between the measurement object and the reflected light detection sensor; correcting the spread of the reflected light actually measured by the reflected light detection sensor based on the observation distance, thereby determining a corrected evaluation parameter for evaluating the spread of the reflected light at a predetermined reference observation distance; and evaluating the surface roughness of the measurement object based on the corrected evaluation parameter.

[0061] 100 Surface texture measuring device 110 Stage 200 Non-contact surface texture sensor head 210 Light irradiation unit 211 Half mirror 220 Reflected light detection sensor 220 First image sensor 230 Observation distance measurement unit 240 Data processing unit 241 Light intensity distribution acquisition unit 242 Observation distance acquisition unit 244 Corrected evaluation parameter calculation unit 245 Surface texture evaluation unit 310 Condenser lens 311 Second image sensor 410 Small lens 510 Light-transmitting thin plate 520 Opaque part 530 Lens 540 Half mirror W Measurement object

Claims

1. A non-contact surface texture evaluation device comprising: a light irradiation unit that irradiates a measurement object with light; a reflected light detection sensor that receives and detects reflected light from the measurement object; an observation distance measurement unit that measures an observation distance, which is the distance between the measurement object and the reflected light detection sensor; and a corrected evaluation parameter calculation unit that obtains a corrected evaluation parameter that evaluates the spread of the reflected light at a predetermined reference observation distance by correcting the spread of the reflected light actually measured by the reflected light detection sensor based on the observation distance, and that evaluates the surface roughness of the measurement object based on the corrected evaluation parameter.

2. A non-contact surface texture evaluation device according to claim 1, wherein the reflected light detection sensor and the observation distance measurement means share one light irradiation unit, and the observation distance measurement means measures the observation distance using a portion of the reflected light.

3. A non-contact surface texture evaluation device according to claim 1, wherein the distance measurement by the observation distance measurement means is a triangulation method.

4. A non-contact surface texture evaluation device according to claim 1, wherein the reflected light detection sensor and the observation distance measurement means share one light irradiation unit, the distance measurement by the observation distance measurement means is a triangulation method, and the observation distance measurement means measures the observation distance using a portion of the reflected light.

5. A non-contact surface texture evaluation device according to claim 1, wherein the reflected light detection sensor and the observation distance measurement means share one light irradiation unit, and further, the reflected light detection sensor and the observation distance measurement means share one image sensor that receives reflected light from the object to be measured, and the observation distance measurement means measures the observation distance using a portion of the reflected light.

6. A non-contact surface texture evaluation device according to claim 5, wherein the observation distance measurement means has two or more lenses or pinholes arranged at a fixed distance from the image sensor, and the observation distance measurement means obtains the observation distance based on the distance between spots generated on the image sensor after passing through the two or more lenses or pinholes.

7. A non-contact surface texture evaluation device according to claim 5, wherein the observation distance measurement means has a lens arranged at a fixed distance from the image sensor and two or more opaque or light-transmitting portions, and the observation distance measurement means obtains the observation distance based on the distance between dark or light portions created on the image sensor by the two or more opaque or light-transmitting portions.

8. A non-contact surface texture evaluation device as claimed in claim 1, wherein the observation distance measurement means has a lens arranged at a fixed distance from the image sensor and two or more opaque or light-transmitting portions, and the observation distance measurement means obtains the observation distance based on the distance between dark or light portions produced on the image sensor by the opaque or light-transmitting portions when a portion of the reflected light is imaged on the image sensor through the lens.

9. A non-contact surface texture evaluation method comprising: irradiating a measurement object with light; receiving and detecting reflected light from the measurement object with a reflected light detection sensor; measuring an observation distance, which is the distance between the measurement object and the reflected light detection sensor; correcting the spread of the reflected light actually measured by the reflected light detection sensor based on the observation distance, thereby determining a corrected evaluation parameter for evaluating the spread of the reflected light at a predetermined reference observation distance; and evaluating the surface roughness of the measurement object based on the corrected evaluation parameter.

Images