Non-contact surface property evaluation device

Abstract

Provided is a non-contact surface property evaluation device that is easy to use, compact, and relatively inexpensive. The surface property evaluation device comprises: a light detector (240) that receives and detects scattered light from a measurement target object; and a single optical aperture (250) or arrayed optical apertures (250) disposed so as to face a light receiving surface (242) of the light detector (240). The relative positions of the optical aperture (250) and the light detector (240) are fixed such that a gap between the optical aperture (250) and the light receiving surface (242) of the light detector (240) is constant. The surface properties of the measurement target object are evaluated on the basis of the intensity distribution of the light detected by the light detector (240).

Description

Non-contact surface texture evaluation device

[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 scattered light.

[0003] Patent Publication No. 2006-58224

[0004] Conventional non-contact surface roughness measuring instruments receive scattered light at the maximum angle with an imaging sensor and evaluate the surface roughness of a workpiece from the image position (coordinates) of that scattered light. Even if the scattering angle is the same, the image position of the scattered light will change if the distance (air gap) between the sensor and the workpiece is different, so the distance between the sensor and the workpiece must be precisely adjusted. However, there are limits to how precisely the positioning between the sensor and the workpiece can be adjusted as a preparatory step before measurement, and it requires cost and effort (man-hours). Another problem is that the accuracy of the roughness measurement is affected by the accuracy (skill) of the setting.

[0005] Additionally, it was necessary to block out unnecessary light while allowing the image sensor to receive the maximum angle scattered light. To achieve this, it was necessary to select the optimal size and shape of the aperture stop, and several patterns of aperture stops with different sizes and shapes were prepared and tried in order. This was also a very time-consuming task.

[0006] It is necessary to form an image of the scattered light on an imaging sensor, which requires multiple high-performance lenses, such as objective lenses and imaging lenses. Preparing multiple high-performance lenses and assembling them with high precision is time-consuming and expensive. Furthermore, the large number of parts makes it unavoidable that conventional non-contact surface roughness measuring instruments are large. As a result, conventional non-contact surface roughness measuring instruments are large and expensive.

[0007] An object of the present invention is to provide a non-contact surface texture evaluation device that is easy to use, small, and relatively inexpensive.

[0008] The non-contact surface texture evaluation device of the present invention comprises a photodetector that receives and detects scattered light from a measurement object, and a single or arrayed optical aperture that is arranged opposite the light receiving surface of the photodetector, and the relative positions of the optical aperture and the photodetector are fixed so that the gap between the optical aperture and the light receiving surface of the photodetector is constant.

[0009] In one embodiment of the present invention, the optical aperture is preferably a lens portion or a light-transmitting portion surrounded by a light-non-transmitting portion.

[0010] In one embodiment of the present invention, it is preferable that a first substrate in which the photodetector is fabricated and a second substrate in which the optical aperture is fabricated are fixed facing each other with a gap therebetween, and that the gap between the optical aperture and the light receiving surface of the photodetector is constant.

[0011] In one embodiment of the present invention, it is preferable that the first substrate on which the photodetector is formed and the second substrate on which the optical opening is formed are attached in an opposing state via a spacer member, and that the gap between the optical opening and the light receiving surface of the photodetector is constant.

[0012] In one embodiment of the present invention, it is preferable that the surface texture of the measurement object is evaluated based on the intensity distribution of light detected by the photodetector.

[0013] In one embodiment of the present invention, it is preferable to perform frequency decomposition on the intensity distribution of the light detected by the photodetector to determine the amplitude of each frequency component, and evaluate the surface texture of the measurement object based on the magnitude of the obtained amplitude.

[0014] In one embodiment of the present invention, it is preferable to evaluate the surface texture of the measurement object based on the difference between the peak value IP of the light intensity and the bottom value IB of the light intensity in the light image detected by the photodetector.

[0015] In one embodiment of the present invention, it is preferable to evaluate the surface texture of the object to be measured based on a normalized value obtained by dividing the difference between the peak light intensity IP and the bottom light intensity IB of the light image detected by the photodetector by the overall average intensity.

[0016] In one embodiment of the present invention, it is preferable to further include a parallel light irradiation unit that irradiates the measurement object with parallel light.

[0017] In one embodiment of the present invention, it is preferable that the surface texture of the measurement object is evaluated based on the magnitude of an evaluation value obtained from a detection signal having a predetermined phase difference detected by the photodetector.

[0018] In one embodiment of the present invention, the photodetector preferably has a light-receiving element array arranged to correspond to the intensity distribution of light that passes through the optical aperture and is formed on the light-receiving surface of the photodetector.

[0019] In one embodiment of the present invention, it is preferable to evaluate the surface texture of the measurement object based on the magnitude of an evaluation value related to the diameter of a Lissajous circle obtained from a phase signal from the light-receiving element array.

[0020] 1 is a diagram for explaining the configuration of a surface texture measuring device according to a first embodiment of the present invention. FIG. 1 is a diagram illustrating a light receiving unit. FIG. 2 is a diagram illustrating a light receiving unit. FIG. 3 is a diagram illustrating an aperture function unit having apertures arranged two-dimensionally. FIG. 4 is a diagram illustrating an image obtained by a photodetector. FIG. 5 is a diagram illustrating a light intensity distribution. FIG. 6 is a diagram illustrating a relationship between roughness and an evaluation index value. FIG. 7 is a diagram illustrating a state in which the distance between the measurement object and the sensor head is relatively short. FIG. 8 is a diagram illustrating a state in which the distance between the measurement object and the sensor head is relatively long. FIG. 9 is a diagram illustrating a configuration in which the light irradiating unit does not include a collimating lens. FIG. 10 is a diagram illustrating scattered light when the roughness of a measurement object is measured when the distance between the measurement object and the sensor head is relatively long. FIG. 11 is a diagram illustrating the light intensity distribution of an image when a specular surface is measured with a wide air gap. FIG. 12 is a diagram illustrating the light intensity distribution of an image when a rough surface is measured with a wide air gap. FIG. 13 is a diagram illustrating scattered light when the roughness of a measurement object is measured when the distance between the measurement object and the sensor head is relatively short. 10 is a diagram illustrating the light intensity distribution of an image when a specular surface is measured with a narrow air gap; FIG. 11 is a diagram illustrating the light intensity distribution of an image when a rough surface is measured with a narrow air gap; FIG. 12 is a diagram comparing the results of Fourier transform of the light intensity distribution for a specular surface and a rough surface; FIG. 13 is a diagram illustrating an example of a light receiving surface of a photodetector in a second embodiment; and FIG. 14 is a diagram illustrating an example of an arithmetic circuit incorporated in a data processing unit.

[0021] Embodiments of the present invention will be illustrated and described with reference to the reference numerals assigned to each element in the drawings. Note that each embodiment may be implemented not only alone, but also in combination with two or more embodiments, and examples of modifications supplemented in each embodiment can also be applied to other embodiments. (First Embodiment) A first embodiment of the present invention will be described. FIG. 1 is a diagram for explaining the configuration of a surface texture measuring device according to a first embodiment of the present invention. The surface texture measuring device 100 includes a stage 110, a light irradiation unit 220, a light receiving unit 230, and a data processing unit 300.

[0022] The light emitting section 220 and the light receiving unit section 230 may be combined into a unit and referred to as a non-contact surface texture sensor head (or non-contact surface texture probe) 200.

[0023] The stage 110 is a platform on which the measurement object W is mounted.

[0024] The light irradiating unit 220 irradiates the surface of the measurement object W with light. The light irradiating unit 220 includes a light source 221 and a collimating lens 222. The light source 221 may be a white LED. It may also be a laser light source, but it is not essential that the light be coherent light.

[0025] The light receiving unit 230 receives scattered light from the surface (surface to be measured for roughness) of the measurement object W. The light receiving unit 230 includes a photodetector 240 and an aperture function portion 250.

[0026] 2 illustrates an example of the light receiving unit 230. The photodetector 240 is an image sensor in this case, and has an image sensor 243 on a light receiving surface 242 of a first substrate 241. The image sensor 243 is a CCD or a CMOS, for example.

[0027] The aperture function section 250 here is a multi-slit section. That is, a plurality of apertures (slits) 252 are arranged in a predetermined one-dimensional direction. The aperture function section 250 is formed by plating one surface of a glass substrate (second substrate) 251 with a non-light-transmitting material, leaving the apertures (slits) 252. (Glass includes not only inorganic materials but also organic glass. The plating may be metal plating, such as black chrome plating.)

[0028] The photodetector 240 and the aperture function unit 250 are fixedly attached so that the distance (gap) between the slit (optical aperture) 252 and the light receiving surface 242 of the photodetector 240 is constant. The distance (gap) between the slit (optical aperture) 252 and the light receiving surface 242 of the photodetector 240 is, for example, several tens of micrometers to several millimeters. A plurality of convex portions (bumps) 244 of a specified height are provided around the imaging element 243 on the light receiving surface side of the photodetector 240. The convex portions 244 define a gap (space), and the photodetector 240 and the aperture function unit 250 are overlapped and fixed via the convex portions 244. The convex portions 244 serve as spacer members for maintaining a constant gap.

[0029] 3, when an optical opening (slit) 252 is formed on the surface of the glass substrate (second substrate) 251 that is farther from the light receiving surface 242 of the photodetector 240, the glass substrate 251 and the photodetector 240 may be directly stacked on each other. In this case, the thickness of the glass substrate (second substrate) 251 itself serves as a spacer member.

[0030] Alternatively, the gap may be adjusted by sandwiching a transparent resin between the first substrate 241 and the second substrate 251. The gap between the photodetector 240 and the opening function portion 250 may be adjusted by using one or a combination of the protrusions (bumps), the thickness of the protrusions themselves, and the resin.

[0031] One example is to provide a distance (gap) between the slit (optical opening) 252 and the light receiving surface 242 of the photodetector 240 by interposing a spacer member between the first substrate 241 and the second substrate 251. The distance (gap) between the slit (optical opening) 252 and the light receiving surface 242 of the photodetector 240 may be maintained by fixedly providing the first substrate 241 and the second substrate 251 with a gap therebetween without interposing a spacer member between the first substrate 241 and the second substrate 251. For example, the first substrate 241 and the second substrate 251 may be fixedly provided with a gap in the housing of the sensor head or the housing of the light receiving unit 230.

[0032] The aperture function unit 250 may be, for example, a non-light-transmitting thin plate (e.g., a black resin plate) with slit openings. Alternatively, the aperture function unit 250 may be a lens array (microlens array) with optical openings as lenses. The lenses may be spherical lenses or, for example, cylindrical lenses. In addition to functioning as an aperture stop that passes scattered light from the measurement target surface W, the lens condenses the light to increase the light intensity, thereby obtaining a sharper image with higher contrast.

[0033] The openings 252 of the opening function portion 250 may be arranged in a two-dimensional array. Fig. 4 is a diagram illustrating an example of an opening function portion 250 having two-dimensionally arranged openings 252. If the openings 252 are arranged two-dimensionally, the surface roughness in two directions of the measurement target surface can be evaluated simultaneously.

[0034] The shape of the opening is not limited to a rectangle, but may be a circle or an ellipse. Furthermore, the opening may have a clearly defined boundary between the light-transmitting portion and the light-non-transmitting portion, or may have a gradual, continuous (or stepwise) transition from the light-transmitting portion to the light-non-transmitting portion.

[0035] When light is irradiated onto the measurement target W from the light irradiating section 220, the reflected light is incident on and received by the light receiving unit section 230. That is, of the reflected light, light that passes through the opening 252 of the opening function section 250 reaches the light receiving surface 242 of the photodetector 240 and is received by the image sensor 243. A detection signal from the photodetector 240 is sent to the data processing section 300 and analyzed by the data processing section 300.

[0036] If the surface of the measurement object W is close to a mirror, the reflected light will be mainly light strongly reflected by the mirror surface (specular reflection), and the light passing through the aperture 252 will be captured as a sharp, bright line image corresponding to the multi-slits of the aperture functional unit 250, as shown at A in FIG. 5. If the surface of the measurement object W is rough, the light scattered by the surface of the measurement object W will be diffused, resulting in a slightly distorted or blurred image, as shown at B in FIG. 5. For convenience of explanation, black and white are reversed in FIG. 5. Also, B in FIG. 5 is an example of an image acquired by the photodetector 240 (image sensor 243) when the light source 221 is an incoherent light source such as an LED, and is an example of a slightly blurred image. For example, if coherent light such as laser light is used as the light source 221, an image with slight distortion similar to so-called speckle will be obtained.

[0037] The data processing unit 300 evaluates the surface roughness of the measurement object from the captured light and dark pattern image. By scanning across the pattern images A and B in FIG. 5 and plotting the light intensity, the light intensity distributions in FIGS. 6 and 7 are obtained. The light intensity distribution of a sharp bright line image such as A in FIG. 5 will likely be obtained as a series of rectangles with a high maximum peak and a minimum bottom of almost zero, as shown in FIG. 6. If the measurement object has a rough surface and the image shows significant light scattering, such as B in FIG. 5, the peak light intensity value IP will be correspondingly smaller. Therefore, the surface texture (surface roughness) can be evaluated based on the magnitude of the peak light intensity value IP.

[0038] The data processing unit 300 calculates the peak light intensity value IP and the trough light intensity value IB, and calculates the difference ΔI between them, i.e., (IP - IB). Surface roughness can be evaluated based on this light-difference ΔI. Here, the peak light intensity value IP may be the peak (maximum brightness value (or pixel value)) within the entire captured image (or a predetermined area range). Alternatively, the peak light intensity value IP may be calculated by extracting individual bright lines from the captured image data, calculating peak values ​​for each bright line, and then calculating the average peak value IP. Similarly, the trough light intensity value IP may be calculated by extracting valleys between bright lines from the captured image data, calculating trough values ​​for each valley, and then calculating the average trough value IP. Furthermore, a normalized light-difference value obtained by dividing the light-difference ΔI by the average value for the entire image data (or a predetermined area range) may be used. The intensity of light entering the light receiving unit may vary depending on the strength of the light source, the lifespan of the light source, the reflectivity of the workpiece, etc., but by using the brightness difference or normalized brightness difference, it is possible to extract only the roughness information without being affected by the light source or reflectivity.

[0039] The denominator for normalization is not limited to the average light intensity of the entire image data (or a predetermined area range). For example, the sum of the extracted peak value IP and bottom value IB may be used as the denominator.

[0040] For example, by using the normalized brightness difference as the relationship between the roughness evaluation index value (IR) and the workpiece surface roughness (here, for example, the arithmetic mean roughness Ra), it is possible to obtain a relationship in which the evaluation index value (IR) tends to decrease as the roughness (Ra) increases, as shown in Figure 8. Conversely, the roughness (for example, Ra) can be estimated from the evaluation index value (IR). It is advisable to measure several sample workpieces with known roughness in advance using the method of the present invention, prepare a roughness evaluation table, and keep it as a roughness evaluation standard.

[0041] The effects of this embodiment will be described. According to this embodiment, the roughness evaluation value IR does not fluctuate even if the distance between the measurement object W and the sensor head 200 changes. FIGS. 9 and 10 are examples of cases where the distance (air gap) between the measurement object W and the sensor head 200 is different. FIG. 9 is a diagram schematically showing scattered light when the roughness of the measurement object is measured when the distance (air gap) between the measurement object W and the sensor head 200 is relatively narrow. FIG. 10 is a diagram schematically showing scattered light when the roughness of the measurement object is measured when the distance (air gap) between the measurement object W and the sensor head 200 is relatively wide.

[0042] In FIG. 9, scattered light from incident points A1 and A2 on the workpiece passes through the aperture (slit) 252 and reaches the photodetector 240 as the outermost light beam. In contrast, in FIG. 10, scattered light from incident points A1 and A2 on the workpiece is blocked by the aperture function unit 250 and cannot reach the photodetector 240. Instead, scattered light from incident points B1 and B2, which are different from A1 and A2, at the same angle passes through the aperture (slit) 252 and reaches the photodetector 240 as the outermost light beam. In this embodiment, the gap between the aperture function unit 250 and the photodetector 240 in the light-receiving unit 230 is fixed and constant. This results in no difference in the amount of light passing through the aperture function unit 250 and forming an image on the imaging element. Therefore, there is no difference in the evaluation index (IR) obtained in relation to the contrast and normalized contrast, and the estimated surface roughness of the measurement object is equivalent. The accuracy of workpiece setting does not affect the surface roughness evaluation value, leading to high robustness.

[0043] In this embodiment, since parallel light is emitted from the light emitting unit, there is no difference in the size of the spread of light detected by the photodetector 240 between the cases of Fig. 9 and Fig. 10. Taking this into consideration as well, it is preferable that the light emitting unit be a parallel light emitting unit that emits parallel light using a collimator lens or the like.

[0044] In the above embodiment, the light irradiation unit has a collimating lens and irradiates parallel light, but the effects of this embodiment can be maintained even without a collimating lens. In FIG. 11, the light irradiation unit 220 does not have a collimating lens, and light is irradiated onto the workpiece at the same emission angle of the light from the light source 221. Alternatively, a lens for converging or diverging the light may be provided between the light source 221 and the workpiece W. In either case, even if the light passing through the exact center is specularly reflected light (regularly reflected light), it will be incident on the light-receiving unit 230 at a certain angle rather than perpendicularly.

[0045] 12 and 15 are examples of cases where the distance (air gap) between the measurement object W and the sensor head 200 is different. Fig. 12 is a diagram schematically showing scattered light when the roughness of the measurement object is measured in a state where the distance (air gap) between the measurement object W and the sensor head 200 is relatively wide. Fig. 15 is a diagram schematically showing scattered light when the roughness of the measurement object is measured in a state where the distance (air gap) between the measurement object W and the sensor head 200 is relatively narrow.

[0046] Figure 13 shows the light intensity distribution of the image when measuring a mirror surface with the wide air gap of Figure 12. Figure 14 shows the light intensity distribution of the image when measuring a rough surface with the wide air gap of Figure 12. Figure 16 shows the light intensity distribution of the image when measuring a mirror surface with the narrow air gap of Figure 15. Figure 17 shows the light intensity distribution of the image when measuring a rough surface with the narrow air gap of Figure 15.

[0047] When the light from the light irradiation unit (light source 221) is divergent light, the period of the image of the slit 252 of the opening function unit 250 changes depending on the difference in the air gap between the sensor head 210 and the workpiece W, and the period of the light and dark image widens as the air gap narrows. However, even if the period of light and dark changes depending on the difference in the air gap between the sensor head 210 and the workpiece W, there is no difference in the tendency for the maximum and minimum values ​​of the light intensity distribution to change depending on the properties of the workpiece surface (for example, roughness), and therefore, by using the light and dark difference or normalized light and dark difference, it is possible to extract only roughness information.

[0048] (Variation 1) A variation of data processing for evaluating the surface roughness of a measurement object from a captured light-dark pattern image will be described. When evaluating surface roughness from the light intensity distribution, the data processing unit 300 converts the spatial light intensity distribution into the frequency domain, decomposes it into frequency components, and calculates the amplitude of each frequency component. This can be done using a so-called Fourier transform. Figure 18 is a diagram comparing the results of Fourier transforming the light intensity distribution (or captured image) for a specular surface and a rough surface. The image obtained from the specular surface is a sharp image that projects the shape of the opening, while the image obtained from the rough surface is distorted and blurred. When the Fourier transforms are performed on each, a difference occurs in the amplitude of the frequency that is thought to be most prevalent. (The fundamental frequency that is thought to be most prevalent is thought to be related to the pitch of the opening (slit) 252, for example.) In other words, when the Fourier transforms are performed on each, a difference occurs in the amplitude peak. When a light intensity distribution (or a captured image) obtained from a mirror surface (a surface with low surface roughness) is Fourier transformed, the amplitude peak is large, while when a light intensity distribution (or a captured image) obtained from a rough surface (a surface with high surface roughness) is Fourier transformed, the amplitude peak is smaller. In the comparison of the amplitudes of the frequency components after Fourier transform in the bottom row of Figure 18, an example is shown in which the peaks of the fundamental frequency are compared. (Note that the peak on the left is a DC component.) Therefore, the amplitude peak (or a value based on the peak) when a light intensity distribution (or a captured image) is Fourier transformed can be used as an evaluation value for surface roughness.

[0049] Both the surface roughness evaluation based on the brightness difference ΔI (the difference between the peak light intensity value IP and the bottom light intensity value IB) described in the first embodiment and this Fourier transform method have in common that the surface roughness of the evaluation target is evaluated based on the magnitude of the light intensity when light passing through the aperture functional portion 250 is captured by the photodetector 240. However, depending on the surface condition of the measurement target, fringe disturbances may become significant, and there are limitations to the resolution and accuracy of simply attempting to obtain the difference ΔI = (IP - IB) between the peak light intensity value IP and the bottom light intensity value IB. In this regard, the resolution or accuracy can be improved by performing frequency decomposition using Fourier transform, extracting the amplitude of the frequency of interest, and using this as the roughness evaluation value.

[0050] It is also possible to evaluate the surface roughness by using information on the peak of a higher frequency component (or a value based on the peak) instead of the peak of the fundamental frequency, or by using information on the peak of a higher frequency component (or a value based on the peak) in addition to the peak of the fundamental frequency as a secondary means to evaluate the surface roughness.

[0051] Second Embodiment A second embodiment of the present invention will be described. In the second embodiment, a light receiving surface 242 of a photodetector 240 has a light receiving element array 260 arranged so as to correspond to the light intensity distribution formed on the light receiving surface 242. In the second embodiment, the light irradiating unit 220 emits parallel light.

[0052] 19 is a diagram illustrating a light receiving surface 242 of a photodetector 240 in the second embodiment. In FIG. 19, light receiving elements 261 are arranged on the light receiving surface 242 of the photodetector 240 in accordance with the period (pitch) of the openings (slits) 252 of the opening function section 250. The light receiving surface 242 of the photodetector 240 is a so-called light receiving element array 260. Here, the light receiving elements 261 are arranged so as to detect light with a phase difference of 90 degrees with respect to one period (one pitch) λ of the slits 252 of the opening function section 250. (The phase difference pitch of the light receiving elements may be a phase difference of 120 degrees or a phase difference of 45 degrees, as long as a value related to the diameter of the Lissajous circle can ultimately be obtained.)

[0053] The light receiving elements 261 are connected to output pads 262-265 for each phase group so that a light receiving signal can be extracted for each phase. Here, there are a first output pad 262, a second output pad 263, a third output pad 264, and a fourth output pad 265, which correspond to 0°, 90°, 180°, and 270°, respectively. If the phase signal from the first output pad 262 is A phase and the phase signal from the third output pad 264 is anti-A phase, then the A phase and anti-A phase have an anti-phase relationship. If the phase signal from the second output pad 263 is B phase and the phase signal from the fourth output pad 265 is anti-B phase, then the B phase and anti-B phase have an anti-phase relationship.

[0054] 20 shows an example of an arithmetic circuit incorporated in the data processing unit 300. Since the positional relationship (phase) of the optical signal received by each light receiving element 261 relative to the brightness of the slits 252 formed in the light receiving surface 242 is always the same, a fixed process can be performed on each received light signal. For example, the same coefficient can be multiplied or the same addition and subtraction can be performed each time. Because it is a fixed operation, once the arithmetic circuit is incorporated, there is no need for complex image processing, and the roughness evaluation index value can be obtained directly.

[0055] Here, an analog calculation circuit amplifies each phase signal using an operational amplifier (amplifier), and then obtains the difference (differential signal) VA between phase A Ia and anti-phase A Ia', and the difference (differential signal) VB between phase B Ib and anti-phase B Ib'. At the same time, all signals (Ia, Ia', Ib, Ib') are added together to obtain a total Vdc. Furthermore, the evaluation value calculation circuit 350 obtains the following evaluation value P:

[0056] P = 2 · ((Va / 2) 2 +(Vb / 2) 2 ) (1 / 2) / Vdc

[0057] This numerator corresponds to the diameter of the so-called Lissajous circle, and the evaluation value P corresponds to the normalized brightness difference. If the surface roughness of the workpiece increases, the contrast of the fringes deteriorates, and the diameter of the Lissajous circle becomes smaller. If this is normalized by the total sum as the evaluation value P, it becomes an evaluation value that correlates with the surface texture (e.g., roughness). Therefore, it is possible to provide an easy-to-use, small, and relatively inexpensive non-contact surface texture evaluation device.

[0058] (Variation 2) In the second embodiment, an example was described in which the light-receiving element array 260 was arranged on the light-receiving surface 242 of the photodetector 240. However, the photodetector is not limited to a light-receiving element array when obtaining an evaluation value related to the diameter of the Lissajous circle. For example, if the photodetector is an image sensor, by assigning specific pixel regions to, for example, phase A, phase B, anti-phase A, and anti-phase B, light detection values ​​(light intensity) for each phase can be obtained from each pixel region, and a value corresponding to the diameter of the Lissajous circle can be obtained based on these. In the case of an image sensor, the detection values ​​are digital values, so post-processing is performed by digital calculation. However, with a light-receiving element array, post-processing can be performed in an analog manner, making it suitable for incorporating analog calculation circuits on a chip and for high-speed processing.

[0059] The present invention is not limited to the above-described embodiment and can be modified as appropriate without departing from the spirit and scope of the invention. The width and spacing of the openings in the aperture functional unit are not particularly limited. Although narrow opening widths and spacings may cause light diffraction or overlap with adjacent fringes, the surface roughness of the present invention can still be evaluated. While the characteristics differ depending on whether or not light diffraction or overlap occurs, in either case, the surface roughness of the object can be evaluated by measuring several sample workpieces with known roughness in advance, preparing a roughness evaluation table, and maintaining it as a roughness evaluation standard. This allows subsequent evaluation (calibration) of the surface roughness of the object.

[0060] 110 stage 200 sensor head 220 light irradiation section 221 light source 222 collimator lens 230 light receiving unit section 240 photodetector 250 aperture function section 241 first substrate 242 light receiving surface 243 imaging element 251 glass substrate 252 aperture 300 data processing section

Claims

1. A non-contact surface texture evaluation device comprising: a photodetector that receives and detects scattered light from a measurement object; and a single or arrayed optical aperture arranged opposite the light receiving surface of the photodetector, wherein the relative positions of the optical aperture and the photodetector are fixed so that a gap between the optical aperture and the light receiving surface of the photodetector is constant.

2. A non-contact surface texture evaluation device according to claim 1, characterized in that the optical opening is a lens portion or a light-transmitting portion surrounded by a light-non-transmitting portion.

3. A non-contact surface texture evaluation device as described in claim 1, characterized in that a first substrate in which the photodetector is formed and a second substrate in which the optical aperture is formed are fixed in an opposing state with a gap between them, and the gap between the optical aperture and the light receiving surface of the photodetector is constant.

4. A non-contact surface texture evaluation device as described in claim 3, characterized in that a first substrate on which the photodetector is formed and a second substrate on which the optical opening is formed are mounted in an opposing relationship via a spacer member, and a gap between the optical opening and the light receiving surface of the photodetector is constant.

5. A non-contact surface texture evaluation device according to claim 1, characterized in that the surface texture of the measurement object is evaluated based on the intensity distribution of light detected by the photodetector.

6. A non-contact surface texture evaluation device as claimed in claim 1, characterized in that frequency decomposition is performed on the light intensity distribution detected by the photodetector to determine the amplitude of each frequency component, and the surface texture of the object to be measured is evaluated based on the magnitude of the obtained amplitude.

7. A non-contact surface texture evaluation device as claimed in claim 1, characterized in that the surface texture of the object to be measured is evaluated based on the difference between a peak value IP of light intensity and a bottom value IB of light intensity in the light image detected by the photodetector.

8. A non-contact surface texture evaluation device according to claim 1, characterized in that the surface texture of the object to be measured is evaluated based on a standardized value obtained by dividing the difference between a peak value IP of light intensity and a bottom value IB of light intensity in the light image detected by the photodetector by an overall average intensity.

9. The non-contact surface texture evaluation device according to claim 1, further comprising a parallel light irradiation unit which irradiates the measurement object with parallel light.

10. A non-contact surface texture evaluation device as claimed in claim 9, characterized in that the surface texture of the object to be measured is evaluated based on the magnitude of an evaluation value obtained from a detection signal having a predetermined phase difference detected by the photodetector.

11. A non-contact surface texture evaluation device as defined in claim 9 or 10, characterized in that the optical detector has a light receiving element array arranged to correspond to the intensity distribution of light that passes through the optical aperture and is formed on the light receiving surface of the optical detector.

12. A non-contact surface texture evaluation device as claimed in claim 11, characterized in that the surface texture of the object to be measured is evaluated based on the magnitude of an evaluation value related to the diameter of the Lissajous circle obtained from the phase signal from the light receiving element array.

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