JPH11132956A - Method and apparatus for optical visual inspection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical visual inspection apparatus by which a protruding defect such as a polished surface or the like can be discriminated from a recessed defect. SOLUTION: In an optical visual inspection apparatus, a work surface W1 as an object to be inspected is irradiated with first parallel light from its vertical direction, and a work surface image in which a protruding and recessed defect on the work surface is imaged as a black part from a gray part is obtained. In this state, the work surface W1 is irradiated with linear parallel light L4 along the work surface W1 from a direction parallel to the work surface W1. Then, a work surface image in which a recessed defect W2 on the work surface is as it is and in which only the part of a protruding defect W3 shines to be white is obtained. Thereby, when the work surface image is inspected, the protruding defect W3 which shines to be white can be discriminated simply from the recessed defect W2 in which the black part from the gray part exists.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical appearance inspection method and apparatus for inspecting concave and convex defects on a polished surface of a flat polished product such as a glass disk.

More specifically, the present invention relates to an optical appearance inspection method and apparatus capable of detecting a convex defect from a concave defect in a state that can be visually identified. Further, the present invention relates to an optical appearance inspection method and apparatus capable of detecting a polished state of a polished surface in a visually identifiable state. Furthermore, the present invention relates to an optical appearance inspection method and apparatus capable of detecting a state of a chamfered portion on a polished surface in a visually identifiable state.

[0003]

2. Description of the Related Art As a method for inspecting defects or the like on a flat substrate surface which has been polished with very high precision, a minute spot observation using an optical microscope or the like is employed. In this method, a lens optical system of an optical microscope and an illumination optical system for illuminating the work surface to be inspected are coaxially arranged, the work surface is illuminated from a vertical direction, and reflected light from the work surface is reflected by the optical microscope. Observed by In the image of the work surface observed by this method, the surface portion having no uneven defects has a uniform brightness. However, in the concave defect and the convex defect, the illumination light is irregularly reflected at the portion, so that the amount of reflected light is lower than at other portions. As a result, these parts are displayed as darker parts than other parts. In general, the darker these parts are, the higher the degree of unevenness is. Concave defects on the polished surface
Pits, bubbles, voids, etc., and the convex defects are foreign substances, particles, etc. attached to the surface.

[0004]

However, this method has the following problems. First, it is not possible to determine whether a spot representing a defect observed on the polished surface is a concave defect or a convex defect. Second, the surface roughness of the polished surface cannot be observed. Third, in a glass disk or the like, a portion such as an outer peripheral edge is chamfered, but the surface state of such a chamfered portion cannot be observed. Fourthly, since the observation area for one observation by the optical microscope is small, it takes time to inspect the entire polished surface.

It is to be noted that a convex defect such as a minute foreign substance or a particle can be eliminated by using a non-contact three-dimensional measuring device or a laser type measuring device. However, such a device is expensive and large-scale. There is a negative effect.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the conventional visual inspection apparatus using an optical microscope or the like, and to make it possible to distinguish between a concave defect and a convex defect on a work surface such as a polished surface. An object of the present invention is to propose an optical appearance inspection method and apparatus capable of inspection.

Another object of the present invention is to propose an optical appearance inspection method and apparatus capable of identifying the state of the work surface, for example, the surface roughness.

A further object of the present invention is to propose an optical appearance inspection method and apparatus capable of identifying the state of a chamfered portion on a work surface or the like.

[0009]

In order to solve the above-mentioned problem, the present invention irradiates a first parallel light from a vertical direction to a work surface to be inspected, and a first parallel light from the work surface. An optical appearance inspection method for imaging a reflected light image of the workpiece at a position coaxial with the first parallel light and determining an uneven defect on the workpiece surface based on the captured first workpiece surface image. In order to distinguish a convex defect on the surface from a concave defect, the following is performed.

That is, in the optical appearance inspection method of the present invention, the work surface is irradiated with the second parallel light along the work surface in a direction parallel to the work surface, and the second parallel light is irradiated on the work surface. Imaging the second reflected light image from the work surface at a position coaxial with the first parallel light, and determining a convex defect on the work surface based on the imaged second work surface image. I have to.

When the second parallel light is radiated in parallel along the surface of the work, the light irradiated to the convex defect such as a foreign substance or a particle adhered to the surface of the work is irregularly reflected by the portion and is imaged. . On the other hand, the second parallel light is not reflected on the portion of the workpiece surface where there is no defect or the portion of the concave defect. As a result, in the second work surface image obtained by imaging the second reflected light image, only a portion corresponding to the convex defect on the work surface appears in a state of glowing white. Therefore, the convex defect on the work surface can be identified from the concave defect.

Here, it is desirable to irradiate the line-shaped second parallel light from both sides of the work surface. In this way, the portion of the convex defect on the work surface can be reliably identified.

In a typical method of the present invention, the first and second parallel lights are simultaneously irradiated on the work surface, and based on a composite image of the imaged first and second work surface images, The convex defect and the concave defect on the work surface are identified. In the composite image obtained in this case, the concave defects appear as darker portions than the other portions, and conversely, the convex defects appear as white portions than the other portions, so that they can be easily identified.

Further, in order to obtain a workpiece surface image in which these concave defects and convex defects are more clearly distinguished,
The amount of light received when capturing the first reflected light image may be adjusted. For example, if the amount of received light of the first reflected light image is significantly reduced, a work surface image with more prominent convex defects can be obtained.

Next, the method of the present invention further comprises the first
Is irradiated from a direction inclined by a predetermined angle from a direction perpendicular to the work surface, and a third reflected light image from the work surface by the first parallel light is defined as the first parallel light. An image is taken at a coaxial position, and the surface roughness of the work surface is determined based on the taken third work surface image. When the first parallel light is emitted from a direction inclined with respect to the work surface, a work surface image in a state where the surface roughness of the work surface is three-dimensionally raised can be obtained. By looking at the workpiece surface image, the surface polishing state can be intuitively recognized.

On the other hand, in order to realize the method of the present invention, a work stage device, a first illumination device, an imaging device, a video processing device, and an image display device are provided. The surface of a work placed on the work placement surface of the stage device is irradiated with first parallel light from a perpendicular direction thereof, and the imaging device is arranged coaxially with the optical axis of the first parallel light. An image of a reflected light from the surface of the work is captured by the captured image sensor, and the image processing device processes a video signal captured by the image sensor, and causes the image signal to be visually displayed via the image display device. In the optical appearance inspection apparatus, the following configuration is added in the present invention.

That is, a second illuminating device for irradiating the surface of a plate-shaped work placed on the work placement surface with linear parallel light along the surface from a direction parallel to the surface is provided. The added configuration is adopted.

Here, in order to reliably capture a convex defect on the surface of the work, the second illuminating device is provided with two illuminating units for irradiating the linear collimated light. It is desirable that these lighting units are arranged opposite to each other with the work mounting surface interposed therebetween, and linear collimated light is radiated from both sides in parallel along the work surface.

Further, in order to obtain a work surface image in which the work surface is polished, the work stage device may be configured such that the work mounting surface is inclined at a predetermined inclination angle with respect to the optical axis of the first parallel light. It is desirable to have a configuration having a gonio stage that can be set.

In this case, in order to maintain a state in which the linear parallel light is always parallel to the surface of the work placed on the work placement surface and irradiated along the surface, It is preferable that the irradiation unit of the second lighting device is supported by the gonio stage so as to move integrally with the work mounting surface.

Further, in order to highlight white spots representing convex defects in the work surface image, a light amount stop mechanism for adjusting the light amount of the reflected light by the first parallel light incident on the image pickup device is arranged. Then, it is desirable to reduce the amount of reflected light due to the first parallel light.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical appearance inspection apparatus to which the present invention is applied will be described with reference to the drawings.

(Overall Configuration) FIG. 1 is an overall configuration diagram of an optical appearance inspection apparatus according to the present invention, and FIG. 2 is a schematic side view and a schematic plan view thereof.

Referring to these drawings, an optical appearance inspection apparatus 1 includes a work stage apparatus 2 for setting a work to be inspected and an optical system for extracting a defect on the surface of the set work. And an optical system / illumination unit 3 in which an illumination system is incorporated, and an illumination system unit 4 for extracting only convex defects among the defects on the work surface. Also, a C for capturing a reflected light image of the work surface obtained through the optical system / illumination system unit 3 and imaging the reflected light image is provided.
A CD camera 5 is attached to the upper end of the optical / illumination unit 3. Further, it has a video processing unit 6 for electrically enhancing and correcting the video signal obtained by the CCD camera 5, and a display monitor 7 for visualizing the video signal corrected by the unit 6.

The main body 8 of the optical appearance inspection apparatus 1 of this embodiment is
The work stage device 2 is mounted on the base 9, and a horizontal arm extending horizontally in front of the device is provided at an intermediate position of the support 9. The cylindrical optical system / illumination system unit 3 is supported on the tip of the horizontal arm in a vertical posture.

The work stage device 2 mounted on the base 9 has a work mounting surface 21 on which a plate-like work W to be inspected can be mounted so as to be perpendicular to the optical axis 3a of the optical / illumination system unit 3. Have. Further, the work stage device 2 of the present embodiment has the
An X stage that can be moved horizontally, a Z stage that can be moved up and down, and a gonio stage that can turn around a center located on a vertical plane including the optical axis 3a.

In the present embodiment, two illumination system units 4 for extracting a convex defect on the surface of a work are opposed to each other with the work mounting surface 21 interposed therebetween. From these illumination system units 4, linear parallel lights are respectively parallel to the surface of the plate-shaped work W placed on the work placement surface 21, and
Irradiated along the surface. These two illumination system units 4 have the same configuration, and are mounted on the gonio stage surface 22 of the work stage device 2. Therefore, the linear parallel light emitted from these illumination system units 4 is
The relationship of being irradiated parallel to the surface of the work placed on the work placement surface 21 and along the surface is always maintained.

(Optical system / illumination system unit 3) FIG. 3 (a)
The schematic configuration of the optical system / illumination system unit 3 will be described with reference to FIG. Light is guided to the unit 3 from a light source 32 such as a halogen lamp via an optical fiber 31. The lens optical system in which the unit 3 is incorporated has an optical axis 3
The beam splitter 33 is provided coaxially with a. Light from the optical fiber 31 enters the beam splitter 33, and a part of the light is reflected and separated in the direction of the optical axis 3a. The light component reflected in the direction of the optical axis 3 a via the beam splitter 32 is emitted as circularly polarized light via the １ ／ wavelength plate 34.

The light L3 emitted from the unit 3 irradiates the surface of the inspection target plate-like work W placed on the work placement surface 21. Usually, the surface normal of the plate-shaped work W is set so as to coincide with the optical axis 3a. In this case, the outgoing light L3 irradiates the work surface vertically. The reflected light from the work surface again becomes linearly polarized light via the quarter-wave plate 34, and the reflected light component that has passed through the beam splitter 33 as it is becomes a polarizing plate 35 disposed on the back side of the beam splitter 33. And enters the light receiving surface of the CCD camera 5. By passing through the polarizing plate 35, the different phase frequency component contained in the reflected light component is removed.

In this example, the quarter-wave plate 34 is a rotating mechanism 3
6 enables rotation about the optical axis 3a. By rotating the quarter-wave plate 34 by the rotation mechanism 36, the amount of light received by the CCD camera 5 can be reduced.

Here, the optical fiber 31 is formed of a multi-component glass fiber, and the NA angle of the light emitted from the tip of the optical fiber is close to 60 to 70 degrees. However, even if the illuminance distribution is uniform, there is a light component that includes a large disturbance angle, so that a fine defect on the work surface cannot be captured. Therefore,
In this example, as shown in FIG. 3B, a diffusing element 37 for removing the shadow of the polished surface of the bundle at the tip of the optical fiber 31 and a pinhole element 38 having a diameter of 0.5 mm, for example.
Are mounted on a composite plate 39 in which the components are laminated. This composite board 3
Through 9, uniform and sharp light is emitted to the beam splitter 33.

As described above, the beam splitter 33 is irradiated with uniform and sharp light by attaching the composite plate 37 to the beam splitter 33.
By arranging the quarter-wave plate 34 and the polarizing plate 35 in the unit, the reflected light component received by the CCD camera 5 becomes a very uniform and partially coherent sharp collimated light with limited frequency characteristics. Become.

(Illumination System Unit 4) Next, the illumination system unit 4 for extracting a convex defect on the work surface will be described. The unit 4 includes a light source 32 and an optical fiber 4.
The light is guided through 1 (see FIG. 1). As shown in FIG. 4A, the light guided to the unit 4 is guided by a light guide 42 disposed therein, and is incident on a line condenser lens 43 disposed on the tip side thereof.
The light emitted from the line condenser lens 43 passes through the slit plate 44 and the 波長 wavelength plate 45, and is emitted as linear parallel light. By using the slit plate 44 and the quarter-wave plate 45, it is possible to obtain a parallel light beam having a very narrow width, for example, a parallel light beam having a width of 2 mm. In addition, halation at the edge of the work end surface can be prevented.

Here, as shown in FIG. 4B, in this example, two illumination system units 4 are arranged to face each other, and are parallel to the work surface from the relative direction of 180 degrees, and along the surface. It is designed to emit line-shaped parallel light.

The operation of detecting defects on the work surface by the optical appearance inspection apparatus 1 according to the present embodiment will be described.

(Detection of Irregular Defects) First, in order to inspect for irregular defects on the work surface, the work mounting surface 21 is set so as to be perpendicular to the optical axis 3a. The work W is placed. When the optical system / illumination system unit 3 is turned on in this state, a very uniform and partially coherent parallel light L3 whose frequency characteristics are restricted is emitted, and the work surface is illuminated vertically. The reflected light on the work surface passes through the optical / illumination unit 3 again,
The light is received by the CCD camera 4. The image signal of the work surface obtained by the CCD camera 5 is displayed as a work surface image on the screen of the display monitor 7 via the image processing unit 6. When the display image is a monochrome image, a portion having no defect on the work surface is displayed as a bright gray image. On the other hand, the uneven defect portion is displayed as a dark gray to black image. Therefore, the portion having the uneven defect can be immediately and intuitively recognized on the monitor screen by the difference between these shadows.

(Detection of Surface Condition) Here, in order to be able to three-dimensionally recognize the state of the work surface and, in the case of a polished surface, the polished state on a monitor screen, the gonio-stage of the stage device 2 must be mounted. After the adjustment, the normal line of the work surface on the work mounting surface 21 is set to be slightly inclined with respect to the optical axis 3a. For example, the normal of the work surface is the optical axis 3a.
Is formed at an angle of about 0.5 to 1.5 degrees. In the work surface image obtained on the monitor screen in this way, the shape of the defective portion including the polished state of the work surface is three-dimensionally highlighted. Therefore, the observer can immediately recognize the polishing state of the work surface.

(Identification of Convex Defects) Next, in order to identify only the convex defects among the irregular defects on the work surface, 2
The illumination system unit 4 is turned on to irradiate a linear parallel light L4 from both sides to the work surface on the work mounting surface. The line-shaped parallel light L4 is irradiated parallel to the work surface and licking the work surface. The principle of identifying a convex defect using the linear parallel light L4 will be described.

As shown in FIG. 4 (c), even if this line-shaped parallel light L4 irradiates the work surface w1, it is a parallel light traveling in a direction perpendicular to the lens optical axis 3a. The upper minute concave defect w2 does not appear on the imaging surface of the CCD camera 5. Similarly, there is almost no detection of dirt that has entered the work surface or bubbles or voids generated inside. On the other hand, when there is a minute convex defect w3 on the work surface, the linear parallel light L4 hits the convex defect w3 and is irregularly reflected, and the reflected light image of the relevant portion is taken by the imaging surface of the CCD camera 5. Is reliably captured.

For example, the frequency characteristic of the monochrome CCD element having the highest spectral characteristic (6000K peak 550n)
m), the convex defect w3 is captured by nearly 100% by using high-power metal halide light (output of about 50 times or more the coaxial light L3 parallel to the optical axis 3a), and the integration effect due to diffuse reflection. Is generated, so that the image is reliably captured by the imaging surface of the CCD camera.

As a result, by irradiating the parallel light L3 parallel to the optical axis 3a, all the fine irregularities on the work surface which changed from gray to black in the work image obtained on the monitor screen were removed. Of which, a line-shaped parallel light L
Irradiation of No. 4 causes a defective portion to change to white. Thus, the white shining portion is a convex defect. Therefore, on the monitor screen, it is possible to immediately discriminate the concave defect, which is gray to black, and the convex defect, which shines white.

Here, the optical system / illumination system unit 3
When the quarter-wave plate 34 mounted on the side of is rotated,
It is possible to change the incident light branching ratio of the parallel light L3 having a lower light energy than the linear light L4 by the beam splitter 33. That is, it is possible to adjust the balance between the work surface image obtained by the reflected light of the parallel light L3 obtained through the CCD camera 5 and the composite image formed by the work surface image obtained by the reflected light of the linear parallel light L4.

For example, by reducing the amount of reflected light of the parallel light L3, it is possible to obtain a work surface image in which convex defects on the work surface are conspicuous. If the parallel light L3 is blocked,
Only the convex defects can be displayed on the monitor.

It is to be noted that, instead of rotating the quarter-wave plate 34, the Z-axis stage of the stage device 2 is moved to bring the obtained work surface image into a defocused state.
Due to the pinhole, only the work surface image is blurred due to the reflected light of the parallel light L3 having a small depth of focus. Therefore, this makes it possible to obtain a work surface image that can recognize only the convex defect.

(Inspection of chamfered portion) On the other hand, according to the optical appearance inspection apparatus 1 of this example, the chamfered portion formed on the edge of the surface of the work W or the like is polished by using the linear parallel light L4. A work surface image that can recognize the state, surface roughness, and the like can be obtained.

That is, the height of the work W on the work mounting surface is adjusted by the Z-axis stage, and the illuminance level of the linear parallel light L4 is adjusted.
As shown in (c), the linear parallel light L4 is set so as to irradiate just the surface portion chamfered at an angle such as 30 degrees or 45 degrees. As a result, the linear parallel light L4 applied to the chamfered portion w4 is reflected, and CC
The polished state of the chamfered portion w4 captured by the D camera 5 is displayed on the monitor in the form of a subtle shadow image.

A monochrome CCD is used as the CCD camera.
Is described, for example, by using a three-plate color CCD, a high-definition color monitor, a high-definition camera, and a high-definition monitor,
The change of the incident condition by the four-wavelength plate can be displayed as a subtle color difference image. This is preferable because the degree of recognition of the operator performing the inspection can be further increased.

The work that can be inspected by the method and apparatus of the present invention may be basically a substrate that has been planarly polished. The shape of the work may be any of a round shape, a donut shape, a square shape, and a polygonal shape.
The thickness is not particularly limited by using the Z stage for height adjustment.

Furthermore, a case has been described in which a workpiece surface image is displayed on a monitor screen, and the inspecting operator visually observes the unevenness defect on the workpiece surface, but this may be automated. For example, the obtained work surface image may be automatically analyzed by the image processing unit for the characteristic amount (size, area, number, etc.) of the defective portion.

[0050]

As described above, in the optical appearance inspection method and apparatus according to the present invention, parallel light is irradiated on the work surface from a direction parallel to the work surface along the work surface. Therefore, it is possible to obtain a work surface image in which only the convex defects on the work surface are displayed as white shining portions, and it is possible to easily identify only the convex defects from among the defects on the work surface. .

In the present invention, the work surface is
Since the work surface image is obtained by irradiating parallel light from a direction inclined by a predetermined angle with respect to the perpendicular direction, the surface state of the work surface is displayed three-dimensionally, and the surface state is intuitively displayed. Can be identified.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an optical appearance inspection apparatus to which the present invention is applied.

2 is a schematic side view and a schematic plan view of the apparatus of FIG.

FIG. 3 is an explanatory diagram showing a configuration of a main part of an illumination system / optical system unit of the apparatus of FIG. 1;

FIG. 4 is an explanatory diagram showing a configuration of a main part of an illumination system unit of the apparatus of FIG. 1;

[Explanation of symbols]

 Reference Signs List 1 optical appearance inspection device 2 stage device 21 work mounting surface 3 optical system / illumination system unit 4 illumination system unit 5 CCD camera 6 video processing unit 7 display monitor 34 quarter-wave plate L3 parallel light L4 linear parallel light W Work w1 Work surface w2 Concave defect w3 Convex defect w4 Chamfered part of work surface

Claims (10)

[Claims] 1. A surface of a work to be inspected is irradiated with a first parallel light from a vertical direction, and a first reflected light image from the work surface is coaxially aligned with the first parallel light. In an optical appearance inspection method, an image is taken at a position, and an irregularity defect on the work surface is determined based on the taken first work surface image, a second direction is set along the work surface from a direction parallel to the work surface. Illuminated, and a second reflected light image from the work surface by the second parallel light is captured at a position coaxial with the first parallel light, and the captured second work surface is imaged. An optical appearance inspection method, wherein a convex defect on the work surface is determined based on an image. 2. The optical appearance inspection method according to claim 1, wherein the second parallel light is emitted from both sides of the work surface. 3. The method according to claim 1, wherein the first and second parallel lights are simultaneously radiated on the work surface, and the first and second parallel light beams are illuminated on the basis of the synthesized image of the first and second work surface images. An optical appearance inspection method, wherein a convex defect and a concave defect on a work surface are determined. 4. The method according to claim 1, wherein the first parallel light is emitted from a direction inclined by a predetermined angle with respect to a direction perpendicular to the surface of the work. Capturing a third reflected light image from the work surface by the parallel light at a position coaxial with the first parallel light, and surface roughness of the work surface based on the captured third work surface image An optical appearance inspection method characterized in that: 5. The optical device according to claim 1, wherein an amount of light received when capturing the first reflected light image or the third reflected light image is adjusted. Type visual inspection method. 6. A work stage device, a first lighting device, an imaging device, a video processing device, and an image display device, wherein the first lighting device is mounted on a work mounting surface of the work stage device. Irradiating the first parallel light from a vertical direction to the surface of the work to be performed, and the imaging device uses an image sensor arranged coaxially with the optical axis of the first parallel light to detect the first parallel light from the surface of the work. An optical appearance inspection device configured to capture a reflected light image, process the video signal captured by the imaging device, and visually display the image signal via the image display device; For the surface of the work placed on the work placement surface,
An optical visual inspection device comprising a second illumination device that irradiates linear parallel light along a surface from a direction parallel to the surface. 7. The illumination device according to claim 6, wherein the second illumination device includes two illumination units for irradiating the line-shaped parallel light, and these are arranged to face each other with the work mounting surface interposed therebetween. An optical visual inspection device characterized by the above-mentioned. 8. The work stage device according to claim 6, wherein the work stage device includes a gonio stage capable of setting the work mounting surface at a predetermined inclination angle with respect to an optical axis of the first parallel light. An optical visual inspection device characterized by the above-mentioned. 9. The goniostage according to claim 6, wherein the irradiation unit of the second illumination device is moved integrally with the work mounting surface. An optical visual inspection device characterized by being performed. 10. A light amount stop mechanism according to claim 6, further comprising a light amount stop mechanism for adjusting a light amount of reflected light by said first parallel light incident on said image pickup device. Optical appearance inspection device.