JP2002365027A - Surface observation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface observation apparatus by which the roughness, the flaw, the foreign particle or the like on the surface of a specimen can be discriminated easily. SOLUTION: A laser (coherent light) luminous flux is created on the measuring face of the specimen by an optical system constituted of a collimator lens and a cylindrical lens, and a thin linear luminous flux which is imaged-formed on the surface of the specimen is projected. Reflected light from a face to be inspected forms a one-dimensional speckle pattern. The reflected light is fetched by a CCD camera or the like so as to be displayed and processed. When the apparatus is used, the surface of any specimen can be observed without coming into contact with the specimen. The observation of the state on the surface of the specimen and the high-accuracy measurement of its movement distance and its speed can be realized by a simple mechanism. Since the measurement can be performed in a noncontact manner, the fluctuation of a water surface, the movement of a blood vessel, a vibration phenomenon or the like can be visualized easily.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for observing a surface of a test object, and more particularly to an apparatus for observing a surface using a speckle pattern.

[0002]

BACKGROUND ART When visible coherent light such as a He-Ne laser is transmitted through ground glass or the like and scattered light is irradiated on a screen such as white paper, an irregular granular pattern is seen. This is interference light that is the result of light that is randomly scattered and diffracted by fine irregularities such as ground glass and the like, and scattered light with a random phase relationship is superimposed on the screen from each point of the object such as ground glass. This is called a pattern. FIG. 1 is a diagram showing a speckle pattern imaged by irradiating not a screen but a CCD camera. By using such a speckle pattern, the surface roughness and the moving speed can be measured. The configuration of the measuring device is described in, for example, JP-A-51-124454, JP-A-63-44110,
This is disclosed in JP-A-63-274807 and the like. However, in these devices, since the speckle pattern is a two-dimensional random interference pattern relating to the surface shape, it takes a lot of time for image processing and the like, and is not suitable for real-time measurement. At a glance, the surface shape was not understood.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface observing apparatus which makes it possible to easily determine the surface roughness, scratches, dust and the like of a test object.

[0004]

In order to achieve the object of the present invention, the present invention relates to a surface observing apparatus for projecting coherent light to an object and observing the state of the object by reflected light, A light source for coherent light, a light beam adjusting unit for adjusting a light beam emitted from the light source to an arbitrary size, and a light beam emitted by the light beam adjusting unit, the light beam emitted from the light beam adjusting unit being converted into one linear beam on the surface of the test object. A light flux image forming unit, and a display unit that receives reflected light from the test object and displays a speckle pattern, so that a one-dimensional spec different from the conventional speckle pattern is provided. Is formed. The light beam adjusting unit may include a collimator lens, and the light beam image forming unit may include a cylindrical lens. A speckle pattern is optically enlarged or reduced by disposing a lens between the test object and the speckle pattern display unit and enlarging or reducing a light beam incident on the speckle display unit. It can also be displayed and observed. Furthermore, since an optical scanning unit for optically scanning the object is provided between the light beam adjusting unit and the light beam image forming unit, the scanning position on the object can be shifted. The optical scanning unit includes:
It can also have a rotatable reflector.

[0005] The speckle pattern display section has a CC
It has a D camera and a display device, and the CCD camera can convert the reflected light into an electric signal and display a speckle pattern on the display device. The speckle pattern display unit may include an image processing unit, and the image processing unit performs a correlation operation of the reflected light from the test object or the image to calculate a movement amount of the test object. It is also possible. In addition, the present invention is a surface observation device that projects coherent light onto a test object and observes the state of the test object by reflected light, wherein a light source of the coherent light and a light beam emitted from the light source are arbitrarily selected. A light beam adjusting unit that adjusts the size of the light beam, a light beam image forming unit that forms the light beam emitted by the light beam adjusting unit into one linear image on the surface of the test object, and Speckle in response to reflected light
A speckle pattern display unit for displaying a pattern, the speckle pattern display unit having a CCD camera, an image processing unit, and a display device, and further for optically scanning the test object. The light scanning unit is provided between the light beam adjusting unit and the light beam image forming unit, the image processing unit, from the two-dimensional image formed by reflected light obtained by scanning the test object, the Another feature is that the surface roughness of the test object is calculated.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration and embodiments of the apparatus of the present invention will be described below with reference to the drawings. The apparatus of the present invention projects a laser (coherent light) beam on the measurement surface of the test object, focuses only one of the light beams on the surface of the test object,
A thin linear light beam is used. This linear light beam is collimated
A one-dimensional speckle pattern is formed from the test surface, which is created by an optical system composed of a lens and a cylindrical lens and is illuminated with this linear light beam, mainly from interference due to scattering in the depth direction. You. Therefore, when the reflected light from the surface to be inspected is received by a screen or received by a CCD camera or the like and connected to a display device, the above-described one-dimensional speckle pattern can be displayed. In addition, since the linear light beam is narrowed down to several μm and focused on the surface to be inspected, if the reflected light beam is received on a screen or received by a video camera and connected to a display device, the surface roughness and the like are reduced. This makes it possible to visualize, for example, cutter marks on a precisely finished surface. Further, this speckle pattern is substantially enlarged to about 10,000 times only in one direction by using, for example, a 1/3 inch CCD camera and a 10 inch display screen. High-precision measurement can be realized with a simple mechanism. Since it can be performed in a non-contact manner, it is possible to visualize fluctuations of the water surface, movement of blood vessels, vibration phenomena, and the like.

<Structure of Apparatus> Referring to FIGS. 2 and 3,
The configuration of the device according to the embodiment of the present invention will be described. FIG.
FIG. 2A is a top view of the apparatus, and FIG. 2B is a side view of the apparatus. Surface observation device 2 for observing the surface of test object 230
00 is the case 2 where the power input terminal 206 is attached.
02 consists of several parts. Case 20
2 includes a laser driver board 204, and a volume 207 for adjusting the intensity of laser light energy.
Is installed. Further, a laser light source 210 and a collimator lens 21 for making a laser beam into an arbitrary size
2. It comprises a cylindrical lens 214, a filter 220 and a CCD camera 240 which are rotatably mounted. The CCD camera 240 is connected to an image output terminal 208, and is connected to an external image display device or the like via the image output terminal 208. Note that the one-point fine broken line in the figure is the optical axis center light, the two-point fine broken line is the light flux peripheral light, and the arrow on the broken line is the direction of the optical path. FIG. 3 shows a system for displaying an image and the like. The image input unit 312, the arithmetic processing unit 314, the image memory 316, and the input unit 318 constitute an image processing unit 310 such as a personal computer and an image such as a display. It comprises a display device 320. The image output terminal 208 is connected to the image processing device 310, and the image processing device 310 outputs the image to the image display device 320 and
Display a pattern.

<One-dimensional speckle pattern> A light beam emitted from a laser light source 210 which is a coherent light source is
The collimator lens 212 forms a parallel light beam. FIG.
4A and 4B are diagrams illustrating a relationship between a cylindrical lens 214 and an optical path, wherein FIG. 4A is a top view and FIG. 4B is a side view. As shown in FIG. 4, the cylindrical lens 214
Has an effect of forming a parallel light beam on the test object 230 in one direction, so that a linear light beam is projected on the test object 230. For this reason, the cylindrical lens 2
The one-dimensional speckle pattern on the surface of the test object 230 is generated by the linear light beam by 14. actually,
The width of the line on the specimen is 3 to 10 μm, and the speckle pattern is for a surface of this width.
Further, since the cylindrical lens 214 is rotatably mounted as described above, the surface of the test object 230 can be irradiated with a linear light beam in an arbitrary direction, and the surface of the test object can be irradiated in various directions. One-dimensional speckle patterns can be observed. The diffused light or specularly reflected light reflected from the test object 230 is converted into an image signal by the CCD camera 240. FIG. 5 is a diagram showing a one-dimensional speckle pattern captured by the CCD camera 240 displayed on the image display device 320. When the test object 230 is in focus, it is displayed as a beautiful one-dimensional speckle pattern as shown in FIG. 5A, but by slightly shifting the focus, the pattern as shown in FIG. Become. In the state where the focus is not adjusted at all, the speckle pattern becomes the same as the conventional one as shown in FIG. The feature of the one-dimensional speckle pattern is that the pattern state is different depending on the roughness of the surface of the test object 230 because the one-dimensional speckle pattern is mainly caused by interference due to scattering in the depth direction. This difference in speckle pattern is so remarkable as to be seen with the naked eye. If the surface roughness is smaller than the wavelength of the laser light, the pattern will have a low contrast and a less linear pattern will be noticeable,
When the surface roughness is large and the phase fluctuation of the scattered light is slightly large, a speckle pattern with high contrast appears. As described above, the contrast of the speckle pattern gradually decreases as the unevenness of the surface shape of the test object becomes smaller than the wavelength of light. By observing the speckle pattern, the surface state can be determined. Although the CCD camera 240 and the image processing device 310 are used to display the speckle pattern in the example of the present embodiment, the diffused light or the specularly reflected light reflected from the test object 230 is used. Alternatively, the image may be formed on a screen such as paper or cloth, or even when the image is formed by the CCD camera 240, the image may be directly output to the image display device 320 and displayed without using the image processing device 310. .

<Determination of Mirror Surface State> FIG. 6 is a diagram showing a mirror made of glass and an aluminum alloy used as a test object. In FIG. 6, a glass mirror 231 to which glass is polished with fine abrasive powder or the like and an aluminum vapor deposition film is added.
And an aluminum alloy mirror 232 manufactured by fly cutting an aluminum alloy with a polygon processing machine or the like. Using these as test objects, using the surface observation device 200 having the configuration shown in FIG. 2 so that the surface of the test object is focused,
A linear light beam is irradiated in the long side direction of each mirror, and speckles due to reflected light are formed on the CCD camera 240 and observed. [Observation of Glass Mirror] FIG. 7A is a speckle pattern obtained by observing the surface of the glass mirror 231 with the surface observation device 200, and FIG.
FIG. 9 is a diagram showing a result of measuring No. 1 by an interferometer. FIG. 7 (a)
The speckle pattern is a thin linear pattern and the pattern is inconspicuous, and the surface is expected to be smooth in the direction of the linear light flux as described above.
As can be seen from the results measured by the interferometer of FIG.
The glass mirror 231 has a smooth concave surface. [Observation of Aluminum Alloy Mirror] FIG. 8A is a speckle pattern obtained by observing the surface of the aluminum alloy mirror 232 with the surface observation device 200, and FIG. It is a figure which shows the result measured in. Compared to the speckle of the glass mirror 231 in FIG. 7A, the pattern has a clear contrast. For this reason, it can be seen that the surface of the aluminum alloy mirror 232 is rough in the direction of the linear light beam. 8B, it was also confirmed that the surface of the aluminum alloy mirror 232 was convex and had a cutter mark.

<Difference Due to Processing of Silicon Carbide (SiC) -Based Ceramics Surface> FIG. 9 is a diagram showing a processed surface of ceramics. In FIG. 9, a ceramic 233 having a ground surface and a ceramic 23 having a polished surface are shown.
4 is shown. These two types of ceramics 233,2
The speckle pattern of each of the surfaces 34 is observed by the surface observation device 200. FIG. 10 shows the surface observation device 20.
It is a figure which shows the speckle pattern of two types of ceramics 233,234 using 0. FIG. 10A is a speckle pattern of the ceramics 233 whose surface is ground, and FIG. 10B is a ceramics 234 whose surface is polished.
It is. Comparing the speckle pattern patterns as in the above-described example of the mirror surface, it can be seen that the surface state of the ceramics 233 whose surface is ground is rougher in the direction of the linear light beam than the ceramics 234 whose surface is polished. In this way, the surface roughness, the uneven polishing of the mirror surface, the cutter mark of the mirror surface obtained by fly-cutting an aluminum alloy, and the like can be actually observed on the display screen without applying image processing.

<Measurement of Movement Amount and Speed of Test Object> FIG. 11
FIG. 3 is a diagram showing an example in which the surface observation device of the present invention is applied to measurement of a moving distance and a moving speed of a test object. Surface observation device 2
At 00, the test object 235 moving is irradiated with laser light.
The one-dimensional speckle pattern formed on the CCD camera 240 in the surface observation device 200 is
At 0, the image is processed, displayed on the image display device 320, and observed and measured. This system can measure the moving distance, the moving speed, and the like, regardless of what the test object 235 is. In the configuration shown in FIG. 11, a linear light beam is projected on the test object 235, and the reflected light is reflected on the CCD camera 24 in the surface observation device 200.
0, and is displayed on the image display device 320.
Measure the amount of movement and speed. The amount of movement that can be measured is within the width of the linear light beam. As shown in FIG. 11, when the test object 235 moves in an arrow direction (upward in the figure) perpendicular to the linear light beam, the image on the image display device 320 also moves. In the direction orthogonal to the linear light beam having a thickness of several μm, the magnification of about 10,000 times in the present embodiment is equivalent to the magnification on the CCD image screen. The measurement accuracy is substantially submicron. Actual test object 2
As a method of measuring the moving distance, the moving speed, and the like of 35, there is a method of sequentially calculating the image correlation while shifting the image before and after the movement to calculate the moving amount. As another processing method for obtaining the moving distance and the moving speed, since the image is a substantially one-dimensional pattern, a linear rectangular area (hereinafter, referred to as a line) from the left end to the right end of the original image is, for example, upper, middle, and lower. , The image of the extracted area and the moved image are correlated while moving the area of the original image, and the moving distance is calculated from the moving amount of the image where the correlation is obtained. Can also be calculated. Further, when an identifiable image portion on a certain line is confirmed in the image after moving, a method of calculating a moving distance or a moving speed based on an interval between the confirmed image portions and an image acquisition time difference. There is. FIGS. 12 and 13 show the moving test object 2.
FIG. 3 is a diagram showing an image of a speckle pattern when 35 is observed by a surface observation device 200. This image has been slightly out of focus for clarity,
I'm shooting. In some cases, such as measurement of a moving distance that involves a correlation calculation, the correlation may be easily obtained by slightly shifting the focus. FIG. 12 is an image of the test object 235 moving in the vertical direction. FIG. 12A shows an image before movement, and FIG. 12B shows an image after movement. As can be seen by comparing the two figures, the image moves from line A to line A ′ (the image moves in the vertical direction in FIG. 12). By examining the relationship between the display on the CCD camera and the actual moving distance, it is possible to know how many pixels have moved on the CCD camera 240 and measure the moving distance. Similarly, FIG.
FIG. 1 shows the test object 235 moved in the horizontal direction.
3A shows the state before the movement, and FIG. 13B shows the state after the movement. As can be seen by comparing the two figures, line B to line B '
It can be seen that the image moves (the image moves in the horizontal direction in FIG. 13). When measuring the movement amount, in order to associate the focus state of the apparatus and the actual movement amount of the test object with the movement amount of the image by the CCD camera, the test object is moved by a predetermined distance, and the image is moved. It is necessary to perform correspondence (calibration) by measuring the amount of movement.

<Other Embodiment> FIG. 14 is a view showing a state in which a rotatable mirror 213 is mounted between a collimator lens 212 and a cylindrical lens 214. By rotating the mirror 213 in the direction A or the direction B, the linear luminous flux on the test object 230 can be shifted like the scanning lines a to c in FIG. By reconstructing the image of the speckle pattern two-dimensionally by the image processing device 310 or the like, a two-dimensional speckle pattern of the test object can be obtained. By using this two-dimensional speckle pattern, the surface roughness can be accurately indicated by numerical values using conventional image processing. FIG. 15 is a flowchart showing a procedure for obtaining a two-dimensional speckle pattern of the test object 230 using the surface observation device 200 to which the structure shown in FIG.
The details will be described below based on this flowchart.
The scanning mirror 213 is moved to match the scanning start position on the test object 230 (S510). Then, a laser is irradiated, the one-dimensional speckle pattern at the above-mentioned scanning position is taken into the image processing device (S520), and compression-converted into a speckle pattern having a width corresponding to the scanning pitch (S5).
30), and write to the image memory 316 (S540). If scanning of the portion to be observed has not been completed (N in S550)
o) Returning to step S510 again, the scanning mirror 213
Is moved by the scanning pitch to repeat the scanning process. At this time, writing to the image memory is performed in an adjacent part of the speckle pattern written before. In this way, a two-dimensional speckle pattern corresponding to the scanning target area on the surface of the test object is sequentially written in the image memory. When all the scans are completed (Yes in S550), the speckle pattern stored in the image memory 316 corresponding to the scanned area is made to correspond to each scanning pitch, and the conventional 2
The image is analyzed by the same method as the two-dimensional speckle pattern, the surface roughness is detected (S560), and the result is displayed (S570). According to the procedure as described above, the test object 230
Can be accurately calculated. As described above, the one-dimensional speckle pattern is considered to be mainly caused by interference due to scattering from the depth direction. Therefore, the surface roughness is detected after compressing the one-dimensional speckle pattern. Therefore, two-dimensional information can be accurately obtained from the measurement of the surface roughness obtained from the conventional two-dimensional speckle pattern. FIG. 16 shows the magnifying lens 21 between the test object 230 and the CCD camera 240.
It is a figure showing what attached 5. The reflected light from the test object 230 is enlarged (reduced) by the enlargement (reduction) lens 215 that can be raised and lowered to an arbitrary magnification, and an optically enlarged (reduced) speckle pattern can be observed.

[0013]

According to the present invention, the linear light beam is narrowed down to a few μm and focused on the surface to be inspected. Therefore, when the reflected light beam is received by a CCD or the like, the surface roughness and the precision can be improved. Visible light, such as cutter marks on the surface, can be digitized. In addition, only one direction is substantially enlarged to, for example, about 10,000 times, so that a highly accurate measurement of the moving distance and the speed can be realized by a simple mechanism. Since the contact can be performed, it is possible to visualize the fluctuation of the water surface, the movement of the blood vessel, the vibration phenomenon, and the like.

[Brief description of the drawings]

FIG. 1 is a diagram showing a speckle pattern.

FIG. 2 is a diagram illustrating a configuration of an apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing a system for displaying a speckle pattern and performing image processing.

FIG. 4 is a diagram showing a relationship between a cylindrical lens and an optical path.

FIG. 5 is a diagram showing a one-dimensional speckle pattern.

FIG. 6 is a view showing a mirror used as a test object and made of glass and an aluminum alloy.

FIG. 7A is a diagram showing a one-dimensional speckle pattern on the surface of a glass mirror. (B) is a diagram showing a result of measuring a glass mirror by an interferometer.

FIG. 8A is a diagram showing a one-dimensional speckle pattern obtained by observing the surface of an aluminum alloy mirror with a surface observation device. FIG. 4B is a diagram showing a result of measuring an aluminum alloy mirror with an interferometer.

FIG. 9 is a view showing a test object obtained by processing ceramics.

FIG. 10 is a diagram showing a one-dimensional speckle pattern of two types of ceramics.

FIG. 11 is a diagram showing an example in which the surface observation device of the present invention is applied to measurement of a moving distance and a moving speed of a test object.

FIG. 12 is a diagram showing a one-dimensional speckle pattern when an object moving in a vertical direction is observed by a surface observation device.

FIG. 13 is a diagram showing a one-dimensional speckle pattern when a test object moving in a lateral direction is observed by a surface observation device.

FIG. 14 is a diagram showing a configuration in which a rotatable mirror is mounted between a collimator lens and a cylindrical lens.

FIG. 15 is a flowchart illustrating a procedure for obtaining two-dimensional information of a test object using a surface observation device to which a scanning lens is added.

FIG. 16 is a diagram showing a configuration in which a lens is attached between a test object and a CCD camera.

[Explanation of symbols]

 Reference Signs List 200 surface observation device 202 case 204 laser driver board 205 mounting portion 206 power input terminal 207 volume 208 image output terminal 210 laser light source 212 collimator lens 214 cylindrical lens 220 filter 230 test object 231 mirror 232 mirror 233 ceramics 234 ceramics 235 Test object 240 CCD camera 310 Image processing device 312 Image input unit 314 Operation processing device 316 Image memory 318 Input device 320 Image display device

Continuation of the front page (71) Applicant 501094018 Isamu Nitta 1130-9, Terachi, Niigata-shi, Niigata (72) Inventor Kimio Omata 1-1-1, Otakubo, Saitama-shi, Saitama (72) Inventor Satoshi Iguchi Chino, Nagano 17-55 Ichinaka Oshio (72) Inventor Isamu Nitta 1130-9 Terachi, Niigata City, Niigata Prefecture F-term (reference) 2G051 AA34 AA90 AB01 AB02 AB10 BA10 BB07 BB09 BB11 BB19 BC05 CA04 CB01 CC20 EA12 EA14 EA30 2G086 GG01

Claims (9)

[Claims] 1. A surface observation apparatus that projects coherent light onto a test object and observes the state of the test object by reflected light, wherein a light source of the coherent light and a light beam emitted from the light source are arbitrarily large. A light beam adjusting unit that adjusts the light beam, a light beam image forming unit that forms the light beam emitted by the light beam adjusting unit into a single line on the surface of the test object, and reflected light from the test object. A display unit for displaying a speckle pattern in response to the display. 2. The surface observation device according to claim 1, wherein the light flux adjusting unit has a collimator lens. 3. The surface observation device according to claim 1, wherein the light beam imaging unit has a cylindrical lens. 4. The surface observation device according to claim 1, wherein a lens is arranged between the test object and the speckle pattern display unit, and the lens is incident on the speckle display unit. A surface observation device characterized by expanding or reducing a light beam. 5. The surface observation device according to claim 1, further comprising: an optical scanning unit for optically scanning the test object, wherein the optical scanning unit includes a light beam adjusting unit and the light beam imaging unit. A surface observation device, which is provided in between. 6. The surface observation apparatus according to claim 5, wherein the optical scanning unit has a rotatable reflecting mirror. 7. The surface observation device according to claim 1, wherein the speckle pattern display unit has a CCD camera and a display device, and the CCD camera electrically transmits the reflected light. Convert it to a signal,
A surface observation device, wherein a speckle pattern is displayed on the display device. 8. The surface observation device according to claim 7, wherein the speckle / pattern display unit has an image processing unit, and the image processing unit reflects light reflected from the test object or the image. The surface observation apparatus, wherein the correlation calculation of (1) is performed to calculate the movement amount of the test object. 9. A surface observation apparatus for projecting coherent light onto an object and observing the state of the object by reflected light, comprising: a light source for coherent light; and a light beam emitted from the light source having an arbitrary size. A light beam adjusting unit that adjusts the light beam, a light beam image forming unit that forms the light beam emitted by the light beam adjusting unit into one linear image on the surface of the test object, and reflected light from the test object. A speckle pattern display unit for displaying a speckle pattern in response to the received signal. The speckle pattern display unit includes a CCD camera, an image processing unit, and a display device. An optical scanning unit for optically scanning an object is provided between the light beam adjusting unit and the light beam imaging unit, and the image processing unit is formed by reflected light obtained by scanning the object. From the two-dimensional image, determine the surface roughness of the test object. Surface observation apparatus characterized by output.