Noncontact surface property evaluation device

Abstract

To provide an easy-to-use, compact, and relatively inexpensive noncontact surface property evaluation device.SOLUTION: A noncontact surface property evaluation device includes a light detector for receiving and detecting scattered light from a measurement object, and a single or arrayed optical aperture arranged opposite to a light receiving surface of the light detector. Relative positions of the optical aperture and the light detector are fixed such that a gap between the optical aperture and a light receiving surface of the light detector is constant. Surface properties of a measurement object are evaluated on the basis of an intensity distribution of light detected by the light detector.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a non-contact surface property evaluation apparatus. For example, it relates to a non-contact surface roughness evaluation apparatus.

Background Art

[0002] A non-contact surface roughness measuring instrument that irradiates light on the surface of a measurement object and measures the surface properties of the measurement object through detection of the scattered light is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventional non-contact surface roughness measuring instruments receive the scattered light at the maximum angle with an imaging sensor, and evaluate the surface roughness of the workpiece from the imaging position (coordinates) of the maximum angle scattered light. At this time, even if the scattering angle is the same, the imaging position of the scattered light will be different if the distance (air gap) between the sensor and the workpiece is different. Therefore, the distance between the sensor and the workpiece must be adjusted accurately. However, there is a limit to extremely strictly performing the position adjustment between the sensor and the workpiece as a preparation step before measurement, and it is costly and time-consuming (man-hours). There is also a problem that the accuracy of roughness measurement is affected by the accuracy (skill) of the setting.

[0005] In addition, while enabling the imaging sensor to receive the scattered light at the maximum angle, it is required to shield unnecessary light. For this purpose, it is necessary to optimally select the size and shape of the aperture stop, and several patterns of aperture stops with different sizes and shapes are prepared and tried in order. This is also a very time-consuming task.

[0006] It is necessary to form an image of the scattered light on the imaging sensor. For this purpose, a plurality of high-performance lenses such as an objective lens and an imaging lens are required. Preparing a plurality of high-performance lenses and assembling them with high precision is time-consuming and costly. In addition, since the number of components increases, the conventional non-contact surface roughness measuring instrument inevitably becomes larger. Therefore, the conventional non-contact surface roughness measuring instrument has been large and expensive.

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

Means for Solving the Problems

[0008] The non-contact surface property evaluation apparatus of the present invention a photodetector that receives and detects scattered light from a measurement object; a single or arrayed optical aperture disposed opposite to the light receiving surface of the photodetector, and the relative position of the optical aperture and the photodetector is fixed so that the gap between the optical aperture and the light receiving surface of the photodetector is constant characterized by this.

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

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

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

[0012] In one embodiment of the present invention, evaluating the surface properties of the measurement object based on the intensity distribution of the light detected by the photodetector This is preferable.

[0013] In one embodiment of the present invention, performing frequency decomposition to obtain the amplitude for each frequency component with respect to the intensity distribution of the light detected by the photodetector, and evaluating the surface properties of the measurement object based on the magnitude of the obtained amplitude This is preferable.

[0014] In one embodiment of the present invention, evaluating the surface properties 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 image of the light detected by the photodetector This is preferable.

[0015] In one embodiment of the present invention, evaluating the surface properties of the measurement object based on the value obtained by normalizing the difference between the peak value IP of the light intensity and the bottom value IB of the light intensity in the image of the light detected by the photodetector by dividing by the overall average intensity This is preferable.

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

[0017] In one embodiment of the present invention, evaluating the surface properties of the measurement object based on the magnitude of the evaluation value obtained from the detection signal of the predetermined phase difference detected by the photodetector This is preferable.

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

[0019] In one embodiment of the present invention, the surface properties of the measurement object are 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. This is preferable.

Brief Description of the Drawings

[0020]

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Embodiments for Carrying Out the Invention

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

[0022] Note that the light irradiation unit 220 and the light receiving unit 230 may be unitized and referred to as a non-contact surface property sensor head (or non-contact surface property probe) 200.

[0023] The stage 110 is a table for mounting the object W to be measured.

[0024] The light irradiation unit 220 irradiates light onto the surface of the object W to be measured. The light irradiation unit 220 includes a light source 221 and a collimating lens 222. As the light source 221, a white LED may be used. It may be a laser light source, but it is not essential that it is coherent light.

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

[0026] FIG. 2 illustrates the light receiving unit 230. The photodetector 240 is an image sensor here and has an imaging element 243 on the light receiving surface 242 of the first substrate 241. The imaging element 243 is a CCD or a CMOS, etc.

[0027] The aperture function unit 250 is a multi-slit here. That is, a plurality of apertures (slits) 252 are arranged in a predetermined one-dimensional direction. The aperture function unit 250 is obtained by plating a light non-transmissive member on one surface of a glass substrate (second substrate) 251 leaving the apertures (slits) 252. (Glass includes not only inorganic materials but also organic glass. As the plating, metal plating, for example, black chrome plating, etc. may be used.)

[0028] The photodetector 240 and the aperture function unit 250 are fixedly attached such 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, from several tens of micrometers to several millimeters. A plurality of convex portions (bumps) 244 having a prescribed height are provided around the imaging element 243 on the light-receiving surface side of the photodetector 240. This convex portion 244 defines the gap (space), and the photodetector 240 and the aperture function unit 250 are overlapped and fixed via the convex portion 244. This convex portion 244 serves as a spacer member for keeping the gap constant.

[0029] Alternatively, as illustrated in FIG. 3, when the optical aperture (slit) 252 is formed on the surface of the glass substrate (second substrate) 251 that is far from the light-receiving surface 242 of the photodetector 240, the glass substrate 251 and the photodetector 240 may be directly overlapped. In this case, the thickness of the glass substrate (second substrate) 251 itself serves as the 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 aperture function unit 250 may be adjusted using one or a combination of the convex portion (bump), its own thickness, and the resin.

[0031] Providing the distance (gap) between the slit (optical aperture) 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 is an example. Without interposing a spacer member between the first substrate 241 and the second substrate 251, the first substrate 241 and the second substrate 251 may be fixedly provided with a gap therebetween so as to maintain the distance (gap) between the slit (optical aperture) 252 and the light-receiving surface 242 of the photodetector 240. For example, a gap may be provided in the housing of the sensor head or the housing of the light-receiving unit 230, and the first substrate 241 and the second substrate 251 may be fixedly installed.

[0032] Note that, as the aperture function unit 250, for example, a thin plate that is non-transmissive to light (e.g., a black resin plate) with a slit aperture provided therein may be used as the aperture function unit. Alternatively, as the aperture function unit 250, a lens array (micro lens array) having an optical aperture as a lens may be used. The lens may be a spherical lens or, for example, a cylindrical lens. In addition to the function as an aperture stop that allows scattered light from the measurement target surface W to pass through, the light intensity is increased by the lens condensing function, and a more contrasty and sharpened image is obtained accordingly.

[0033] The apertures 252 of the aperture function unit 250 may be provided in a two-dimensional array. FIG. 4 is a diagram illustrating the aperture function unit 250 having apertures 252 arranged in a two-dimensional array. If the apertures 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 aperture is not limited to a rectangle, and it may be a circle or an ellipse. Also, in the aperture, the boundary between the light transmissive portion and the light non-transmissive portion may be clearly distinguishable, or it may be in a form that gradually (or stepwise) changes continuously from the light transmissive portion to the light non-transmissive portion.

[0035] When the light irradiation unit 220 irradiates the measurement target object W with light, the reflected light is incident on the light receiving unit 230 and received. That is, among the reflected light, the light that has passed through the apertures 252 of the aperture function unit 250 reaches the light receiving surface 242 of the photodetector 240 and is received by the imaging element 243. The detection signal from the photodetector 240 is sent to the data processing unit 300 and analyzed by the data processing unit 300.

[0036] If the surface of the object W to be measured is close to a mirror surface, the reflected light (specular reflection light) strongly reflected by the mirror surface is the main reflected light, and the light passing through the aperture 252 will be imaged as a sharp bright line image corresponding to the multi-slit of the aperture function unit 250, as shown by A in FIG. 5. When the surface of the object W to be measured is a rough surface, the light scattered by the surface of the object W spreads, and it will be imaged as a somewhat distorted or blurred image, as shown by B in FIG. 5. In FIG. 5, for the sake of explanation, white and black are drawn in reverse. 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 incoherent light such as an LED, and is an example of a somewhat blurred image. For example, if coherent light such as laser light is used for the light source 221, an image with some disturbance such as so-called speckle can be obtained.

[0037] The data processing unit 300 evaluates the surface roughness of the object to be measured from the captured light and dark pattern image. When scanning in the direction across the pattern images of A and B in FIG. 5 and plotting the light intensity, the light intensity distributions of FIGS. 6 and 7 are obtained. The light intensity distribution of a sharp bright line image such as A in FIG. 5 will be obtained as a continuous rectangle with a high maximum peak and a minimum bottom almost zero, as shown in FIG. 6. In the case of an image where the object to be measured is a rough surface and light scattering is large, such as B in FIG. 5, the peak value IP of the light intensity will be smaller accordingly. Therefore, the surface properties (surface roughness) can be evaluated based on the magnitude of the peak value IP of the light intensity.

[0038] The data processing unit 300 calculates the peak value IP of the light intensity and the bottom value IB of the light intensity respectively, and obtains the difference ΔI = (IP - IB) between the two. The surface roughness can be evaluated based on this light and dark difference ΔI. Here, the peak value IP of the light intensity may be the peak (the maximum value of the luminance value (or pixel value)) in the entire captured image (or a preset area range). Alternatively, for the peak value IP of the light intensity, bright lines may be extracted one by one from the captured image data, the peak value may be obtained for each bright line, and further, the average value IP of the peak values may be calculated. Similarly, for the bottom value IP of the light intensity, valleys between bright lines may be extracted from the captured image data, the bottom value may be obtained for each valley, and further, the average value IP of the bottom values may be calculated. Furthermore, the normalized brightness difference obtained by dividing the brightness difference ΔI by the average value of the entire image data (or a preset area range) may be used. Although the intensity of the light incident on the light receiving unit may vary depending on the intensity of the light source, the lifespan of the light source, the workpiece reflectivity, etc., by using the brightness difference or the normalized brightness difference, it is possible to extract only the roughness information without being affected by the light source or the reflectivity.

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

[0040] For example, taking the relationship between the normalized brightness difference as the roughness evaluation index value (IR) and the workpiece surface roughness (here, for example, the arithmetic mean roughness Ra), as illustrated in FIG. 8 for example, a relationship can be obtained in which the evaluation index value (IR) decreases as the roughness (Ra) increases. 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 by the method of the present invention and prepare them as a roughness evaluation table to be used as a roughness evaluation criterion.

[0041] The effects of this embodiment will be described. According to this embodiment, even if the distance between the measurement object W and the sensor head 200 changes, there is no variation in the roughness evaluation value IR. FIGS. 9 and 10 are examples when 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 measuring the roughness of a measurement object W in a state where the distance (air gap) between the measurement object and the sensor head 200 is relatively narrow. FIG. 10 is a diagram schematically showing scattered light when measuring the roughness of a measurement object W in a state where the distance (air gap) between the measurement object and the sensor head 200 is relatively wide.

[0042] In FIG. 9, it is assumed that scattered light from the incident points A1 and A2 on the workpiece passes through the aperture (slit) 252 and reaches the photodetector 240 as the outermost light rays. On the other hand, in the case of FIG. 10, the scattered light from the incident points A1 and A2 on the workpiece is blocked by the aperture function unit 250 and cannot reach the photodetector 240. However, instead, scattered light at the "same angle" from incident points B1 and B2 different from A1 and A2 passes through the aperture (slit) 252 and reaches the photodetector 240 as the outermost light rays. Here, in the present embodiment, in the light receiving unit 230, the gap between the aperture function unit 250 and the photodetector 240 is fixed and constant. Then, there is no difference in the amount of light that forms an image on the imaging element after passing through the aperture function unit 250, and therefore, there is no difference in the evaluation index value (IR) obtained in relation to the brightness difference or the normalized brightness difference, and the estimated surface roughness of the measurement object is the same. The accuracy of the workpiece setting does not affect the surface roughness evaluation value, leading to high robustness.

[0043] In the present embodiment, since parallel light is irradiated from the light irradiation unit, there is no change in the size of the spread of the light detected by the photodetector 240 between the case of FIG. 9 and the case of FIG. 10. Considering such a point as well, it is preferable that the light irradiation unit is a parallel light irradiation unit that emits parallel light by a collimating lens or the like.

[0044] In the above embodiment, the light irradiation unit has a collimating lens, and the case where the light irradiation unit irradiates parallel light is exemplified. However, the effects of the present embodiment can be maintained even without a collimating lens. In FIG. 11, the light irradiation unit 220 does not include a collimating lens, and light is irradiated onto the workpiece as it is at the light emission angle of the light source 221. Alternatively, a lens for focusing or diverging may be provided between the light source 221 and the workpiece W. In any case, light other than the light passing through the true center will enter the light receiving unit 230 at an angle rather than perpendicular to it even if it is specularly reflected light (regularly reflected light).

[0045] FIGS. 12 and 15 are examples when 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 measuring the roughness of the measurement object 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 measuring the roughness of the measurement object in a state where the distance (air gap) between the measurement object W and the sensor head 200 is relatively narrow.

[0046] FIG. 13 is the light intensity distribution of the image when measuring the mirror surface with the wide air gap in FIG. 12. FIG. 14 is the light intensity distribution of the image when measuring the rough surface with the wide air gap in FIG. 12. FIG. 16 is the light intensity distribution of the image when measuring the mirror surface with the narrow air gap in FIG. 15. FIG. 17 is the light intensity distribution of the image when measuring the rough surface with the narrow air gap in FIG. 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 aperture function unit 250 changes depending on the difference in the air gap between the sensor head 210 and the workpiece W, and as the air gap narrows, the period of the bright and dark images widens. However, even if the period of light and dark changes due to the difference in the air gap between the sensor head 210 and the workpiece W, there is no tendency for the maximum and minimum values of the light intensity distribution to change due to the surface properties (e.g., roughness) of the workpiece surface. Therefore, by using the light and dark difference or the normalized light and dark difference, only the roughness information can be extracted.

[0048] (Modification Example 1) A modification example of data processing for evaluating the surface roughness of a measurement object from the captured light and dark pattern image will be described. When evaluating the 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 obtains the amplitude for each frequency component. This can be performed by a so-called Fourier transform. FIG. 18 is a diagram comparing the results of Fourier-transforming the light intensity distribution (or the captured image) for a mirror surface and a rough surface. The image obtained from the mirror surface is a sharp image projecting the shape of the opening, and the image obtained from the rough surface has disturbances and blurs. When each is Fourier-transformed and the amplitudes of the frequencies considered to be most contained are compared, a difference occurs in their magnitudes. (The fundamental frequency considered to be most contained is considered to be related to the pitch of the opening (slit) 252, for example.) That is, when each is Fourier-transformed, a difference occurs in the peak of the amplitude. The peak of the amplitude when the light intensity distribution (or the captured image) obtained from the mirror surface (surface with small roughness) is Fourier-transformed is large, and the peak of the amplitude when the light intensity distribution (or the captured image) obtained from the rough surface (surface with large roughness) is Fourier-transformed is smaller than that. In FIG. 18, the case of comparing the peaks of the fundamental frequency in the comparison of the amplitudes of the frequency components after Fourier transformation in the lowermost row is illustrated. (Note that the leftmost peak is the DC component.) Therefore, the peak of the amplitude (or the value based on the peak) when the light intensity distribution (or the captured image) is Fourier-transformed can be used as an evaluation value of the surface roughness.

[0049] In the surface roughness evaluation based on the light and dark difference ΔI (the difference between the peak value IP of the light intensity and the bottom value IB of the light intensity) described in the first embodiment, and also in this Fourier transform method, they are common in that the surface roughness of the object to be evaluated is evaluated based on the magnitude of the light intensity when the light that has passed through the aperture function unit 250 is captured by the photodetector 240. However, depending on the state of the surface of the object to be measured, the stripe disorder becomes large, and there are limits to the resolution and accuracy even when trying to simply capture the difference ΔI = (IP - IB) between the peak value IP of the light intensity and the bottom value IB of the light intensity. In this regard, by performing frequency decomposition by Fourier transform and extracting the amplitude of the frequency to be obtained (the frequency of interest) and using this as the evaluation value of the roughness, the resolution or accuracy can be improved.

[0050] Note that, instead of using the peak of the fundamental frequency, the information of the peak (or the value based on the peak) of a higher frequency component may be used to evaluate the surface roughness, or in addition to the peak of the fundamental frequency, the information of the peak (or the value based on the peak) of a higher frequency component may also be used secondarily to evaluate the surface roughness.

[0051] (Second Embodiment) The second embodiment of the present invention will be described. In the second embodiment, the light receiving surface 242 of the photodetector 240 has a light receiving element array 260 arranged so as to correspond to the intensity distribution of light formed on the light receiving surface 242. Note that in the second embodiment, it is assumed that the light irradiation unit 220 emits parallel light.

[0052] FIG. 19 is a diagram illustrating the light receiving surface 242 of the 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 aperture (slit) 252 of the aperture 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 90-degree phase difference with respect to one period (one pitch) λ of the slit 252 of the aperture function section 250. (The phase difference pitch of the light-receiving elements may be 120 degrees, 45 degrees, or any value related to the diameter of the Lissajous circle finally obtained.)

[0053] Each light-receiving element 261 is collectively 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 are assumed to correspond to 0°, 90°, 180°, and 270° respectively. If the phase signal from the first output pad 262 is defined as the A phase and the phase signal from the third output pad 264 is defined as the inverse A phase, then the A phase and the inverse A phase are in an inverse phase relationship. If the phase signal from the second output pad 263 is defined as the B phase and the phase signal from the fourth output pad 265 is defined as the inverse B phase, then the B phase and the inverse B phase are in an inverse phase relationship.

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

[0055] Here, by an analog arithmetic circuit, after amplifying each phase signal with an operational amplifier (amplifier), the difference (differential signal) VA between the A phase Ia and the inverse A phase Ia', and the difference (differential signal) VB between the B phase Ib and the inverse B phase Ib' are obtained. At the same time, the sum Vdc of all signals (Ia, Ia', Ib, Ib') is obtained. Further, the following evaluation value P is obtained by the evaluation value calculation circuit 350.

[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 light and dark difference. If the surface roughness of the workpiece becomes rough, the contrast of the stripes deteriorates, so the diameter of the Lissajous circle becomes small. If this is used as the evaluation value P normalized by the overall sum, it becomes an evaluation value correlated with the surface properties (for example, roughness). Therefore, it is possible to provide a non-contact surface property evaluation apparatus that is easy to use, small, and relatively inexpensive.

[0058] (Modification 2) In the second embodiment, the example in which the light receiving element array 260 is arranged on the light receiving surface 242 of the photodetector 240 has been described. However, in obtaining the evaluation value related to the diameter of the Lissajous circle, the photodetector is not limited to the light receiving element array. For example, when the photodetector is an image sensor, if a specific pixel region is assigned, for example, as A phase, B phase, inverse A phase, inverse B phase, etc., the light detection values (light intensities) of each phase can be obtained from each pixel region, and based on these, a value corresponding to the diameter of the Lissajous circle can be obtained. In the case of an image sensor, since the detection value is a digital value, the post-processing is digital calculation. However, if it is a light receiving element array, the post-processing can be made analog, so it is suitable for chip formation and high-speed processing of an analog calculation circuit.

[0059] Note that the present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the gist. There is no particular limitation on the width and interval of the opening of the opening function section. If the width and interval of the opening are narrow, light may diffract or overlap with adjacent stripes, but the surface roughness of the present invention can be evaluated. Note that although the characteristics vary depending on whether there is light diffraction or overlap, in any case, several sample workpieces with known roughness are measured in advance and prepared as a roughness evaluation table to be used as a roughness evaluation criterion, and there is no difference that the surface roughness of the measurement target cannot be evaluated by post-value assignment (calibration).

Description of Signs

[0060] 110 Stage 200 Sensor Head 220 Light Irradiation Unit 221 Light Source 222 Collimating Lens 230 Light Receiving Unit 240 Photodetector 250 Aperture Function Unit 241 First Substrate 242 Light Receiving Surface 243 Imaging Element 251 Glass Substrate 252 Aperture 300 Data Processing Unit

Claims

1. A photodetector that receives and detects scattered light from a measurement object, A single or arrayed optical aperture disposed opposite to the light receiving surface of the photodetector, and comprising: The relative position of the optical aperture and the photodetector is fixed so that the gap between the optical aperture and the light receiving surface of the photodetector is constant A non-contact surface property evaluation apparatus characterized by the above.

2. In the non-contact surface property evaluation apparatus according to Claim 1, The optical aperture is a lens portion or a light transmission portion surrounded by a light non-transmission portion. A non-contact surface property evaluation apparatus characterized by the above.

3. In the non-contact surface property evaluation apparatus according to Claim 1, A first substrate on which the photodetector is formed and a second substrate on which the optical aperture is formed are fixed in a facing state with a gap therebetween, and the gap between the optical aperture and the light receiving surface of the photodetector is constant. A non-contact surface property evaluation apparatus characterized by the above.

4. In the non-contact surface property evaluation apparatus according to Claim 3, A first substrate on which the photodetector is formed and a second substrate on which the optical aperture is formed are attached in a facing state via a spacer member, and the gap between the optical aperture and the light receiving surface of the photodetector is constant. A non-contact surface property evaluation apparatus characterized by the above.

5. In the non-contact surface property evaluation apparatus according to Claim 1, The surface property of the measurement object is evaluated based on the intensity distribution of the light detected by the photodetector. A non-contact surface property evaluation apparatus characterized by the above.

6. In the non-contact surface property evaluation apparatus according to Claim 1, Frequency decomposition is performed to obtain the amplitude for each frequency component with respect to the intensity distribution of the light detected by the photodetector, and the surface properties of the measurement object are evaluated based on the magnitude of the obtained amplitude. A non-contact surface property evaluation apparatus characterized by the above.

7. In the non-contact surface property evaluation apparatus according to claim 1, The surface properties of the measurement object are evaluated based on the difference between the peak value IP of the light intensity and the bottom value IB of the light intensity in the image of the light detected by the photodetector. A non-contact surface property evaluation apparatus characterized by the above.

8. In the non-contact surface property evaluation apparatus according to claim 1, The surface properties of the measurement object are evaluated based on a value obtained by normalizing the difference between the peak value IP of the light intensity and the bottom value IB of the light intensity in the image of the light detected by the photodetector by dividing it by the overall average intensity. A non-contact surface property evaluation apparatus characterized by the above.

9. In the non-contact surface property evaluation apparatus according to claim 1, It includes a parallel light irradiation unit that irradiates the measurement object with parallel light. A non-contact surface property evaluation apparatus characterized by the above.

10. In the non-contact surface property evaluation apparatus according to claim 9, The surface properties of the measurement object are evaluated based on the magnitude of the evaluation value obtained from the detection signal of the predetermined phase difference detected by the photodetector. A non-contact surface property evaluation apparatus characterized by the above.

11. In the non-contact surface property evaluation apparatus according to claim 9 or claim 10, The photodetector has a light receiving element array arranged so as to correspond to the intensity distribution of the light formed on the light receiving surface of the photodetector through the optical aperture. A non-contact surface property evaluation apparatus characterized by the above.

12. In the non-contact surface property evaluation apparatus according to claim 11, evaluating the surface property of the measurement target based on the magnitude of the evaluation value related to the diameter of the Lissajous circle obtained from the phase signal from the light receiving element array A non-contact surface property evaluation apparatus characterized by the above.

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