JPH06241758A - Flaw inspection device - Google Patents

Abstract

PURPOSE:To detect a flaw existing on the rough face of a an optical memory disk very easily and sensitively. CONSTITUTION:A light source 1 is a light source having high luminance such as a halogen lamp, the light flux emitted from this light source 1 is converted by a cylindrical lens 2 serving as a light flux projecting means while the divergence angle in the incidence face is kept nearly parallel, then it is radiated to the reflecting surface 6 (measured surface) of an optical memory disk 3 to form a measured area 5 shown by a broken line. The light flux reflected on the reflecting surface 6 is projected on a screen 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection apparatus for inspecting defects caused by minute foreign matter, deformation, etc. present on the surface or recording surface of an optical disc or the like.

[0002]

2. Description of the Related Art Conventionally, inspection of defects existing on a smooth mirror-finished surface of a molded substrate of an optical disk, optical parts, etc. has been performed using light. For example, a high-luminance light beam is projected on the surface to be measured, and only the light beam scattered by the defect is detected, or specularly reflected light is projected on the light-receiving surface such as a screen and the illuminance of the portion scattered by the defect is detected. It was customary to apply the so-called shadow graph principle, which utilizes the fact that the area becomes dark and becomes dark. Furthermore, CCD and I
Image processing has also been performed in combination with a TV camera or the like to determine the shape and size of a defect.

[0003]

However, the conventional means for detecting a defect by using light is not effective unless the surface to be measured is a mirror surface, and a matte surface (rough surface) having diffusivity is used. Was not applicable. For example, in a magneto-optical disk of a magnetic field modulation recording system, which has been developed in recent years, a magnetic field is applied from the protective film side by using an air levitation type magnetic head slider when recording information, so that the head is not attracted. The surface of the protective film may be a matte surface for the purpose of prevention. At this time, if the surface of the mat-like protective film has microscopic defects, especially protrusion-shaped defects, the head collides with it and the flying height of the head fluctuates,
If recording / playback is not performed normally, or if it is excessive, it may cause damage such as damage to the magnetic head.
It has been desired to develop a method and apparatus for inspecting such defects in advance.

In addition, a defect inspection apparatus that performs image processing by combining a CCD, an ITV camera, etc., and determines the shape and size of a defect uses a frame memory for storing an image and a complicated structure by using an image device. Since expensive hardware is required, (first, the method of visually inspecting by a person has a problem in terms of detection accuracy, such as a judgment level not being constant due to individual differences, small defects cannot be detected, and further workability, In terms of efficiency, it was also insufficient. Although such problems can be solved by the photoelectric inspection device that uses scattered light and the inspection device that applies the image processing technology, using the image processing device) There is a problem that the cost becomes high. Further, a problem common to all the methods and apparatuses described above is that the size and shape of a defect can be determined to some extent, but the direction and amount of irregularities cannot be determined.

Further, a transparent film may be applied on the surface of the optical-incidence-side substrate of the optical disk for the purpose of preventing scratches and electrification. Since unevenness may occur and affect the recording / reproducing characteristics of the optical disc, a method and apparatus for inspecting this in advance have also been desired.

The present invention has been made in view of the above problems of the prior art, and it is an object of the present invention to provide a defect inspection apparatus for detecting defects existing on a rough surface of an optical disk or the like with extremely easy and high sensitivity. And

A further object of the present invention is to allow non-contact, high-speed and convenient inspection of the size and deformation of a defect existing on a surface such as a smooth surface or a rough surface, and if only the size of the defect is present. It is another object of the present invention to provide a defect inspection apparatus capable of determining the direction, amount, and shape of unevenness.

[0008]

A defect inspection apparatus according to a first aspect of the present invention for achieving the above object, is such that at least a part of a light beam is larger than a scene critical angle on a surface to be measured having diffuse reflectivity. It has a light beam projecting means for projecting so as to be incident at an incident angle, and a light receiving means for receiving the light beam reflected or scattered by the surface to be measured, and is present on the surface to be measured using the light receiving means. It is characterized by detecting defects.

Further, the luminous flux projection means includes a divergence angle limiting means for limiting the divergence angle of the luminous flux within the incident plane so that all the luminous fluxes are incident at an incident angle larger than the scene critical angle.

Further, the light receiving means may be a screen or an image pickup tube.

A defect inspection apparatus according to a second aspect of the present invention comprises an optical system for converging a slit-shaped light beam on a surface to be measured,
A moving means for moving the surface to be measured relative to the slit-shaped light beam, and a plurality of light receiving units provided at positions conjugate with the surface to be measured and receiving reflected light from the surface to be measured. A photodetector consisting of a surface and a detection means for detecting a defect by calculating an output obtained from the photodetector, and with respect to the relative movement direction of the surface to be measured, The slit-shaped light beams may be arranged so that their longitudinal directions are orthogonal to each other, and the light-receiving surfaces of the photodetectors are arranged in parallel with each other. Further, the photodetectors may be arranged adjacent to each other. It is a two-division type photodetector comprising a light-receiving surface, and the detection means uses the differential output of the two-division type photodetector to measure the size of the defect on the surface to be measured, the unevenness direction of the defect and the amount of the defect. May be determined.

Here, "the position conjugate with the surface to be measured" described in claim 5 means that the light from the surface to be measured forms an image after passing through an optical system such as a lens. It is a position that has a relationship.

[0013]

According to the first aspect of the present invention, the first aspect is configured as described above.
The device of the invention of the invention utilizes a scene phenomenon,
That is, when the surface to be measured is a diffuse reflection surface, the direction in which the incident light beam is scattered differs depending on the incident angle.
When the incident angle is small, the scattered light is scattered with a wide light distribution centered on the specular reflection light, but when the incident angle exceeds a certain angle called the scene critical angle, the scattered light almost disappears, It is known that the regular reflection component becomes extremely strong. The present invention makes it possible to detect a defect similar to that of a conventional specular surface to be measured by utilizing the fact that the same light reflection and scattering characteristics as in the case of a mirror surface are obtained with respect to the surface to be measured which is a rough surface. Become.

In the device of the second invention according to claim 5,
A slit-shaped light beam is condensed on the surface to be measured, and reflected light reflected from the surface to be measured is received by a photodetector including a plurality of light receiving surfaces provided at positions conjugate with the surface to be measured. And
When the surface to be measured is moved relative to the slit-shaped light beam by the moving means, the slit-shaped image incident on the photodetector is deformed due to the presence of defects on the surface to be measured.

Therefore, the direction and amount of deformation of the slit-shaped image caused by the presence of the defect on the surface to be measured are received by the photodetector, and the output obtained therefrom is calculated by the detecting means to determine the size of the defect, The direction and amount of unevenness are determined.

[0016]

Embodiments of the present invention will now be described with reference to the drawings.

(First Embodiment) FIG. 1 is a schematic perspective view of a first embodiment of the defect inspection apparatus of the present invention, FIG. 2 is a schematic side view of the defect inspection apparatus shown in FIG. 1, and FIG. It is a schematic plan view of the defect inspection apparatus shown in FIG.

As shown in FIGS. 1 to 3, the light source 1 is a high-luminance light source such as a halogen lamp, and the luminous flux emitted from the light source 1 is incident on the incident surface by a cylindrical lens 2 which is a luminous flux projection means. After the divergence angle is converted into a substantially parallel state, the reflection surface 6 (measurement surface) of the optical disc 3 is irradiated with the measurement area 5 shown by a broken line. Here, the incident angles of all the light fluxes illuminating the reflecting surface 6 (surface to be measured) are set to a value larger than the scene critical angle.

FIG. 4 is a diagram of an optical system for explaining a so-called scene phenomenon. When the reflection surface 6 is a diffuse reflection surface, the direction in which the incident light 7 incident on the reflection surface 6 is scattered depends on the incident angle θ. When the incident angle θ is small, the scattered light is scattered with a wide light distribution characteristic 9 centered on the specular reflection light 8 as shown by a broken line. However, it is known that when the incident angle θ exceeds a certain angle called the scene critical angle, scattered light almost disappears and the specular reflection component becomes significantly strong. That is, the light distribution characteristic 10 having a strong directivity around the regular reflection direction 8 is exhibited.
Although the value of the scene critical angle varies depending on the material of the diffusion surface, it is usually around 60 degrees.

As can be seen from the above description, in the apparatus shown in FIGS. 1 to 3, most of the luminous flux incident at an incident angle larger than the scene critical angle is specularly reflected and projected onto the screen 4. . The illuminance distribution of the light on the screen 4 has a uniform distribution when there are no defects such as protrusions or foreign matter that prevent specular reflection on the surface 5 to be measured. Reduces the illuminance of the corresponding part to form a dark part. That is, since the projected light beam is directly specularly reflected (total scene reflection) on the defect-free portion, the same uniform distribution as the projected light beam appears on the light receiving surface, while the light is scattered on the defect portion. The light does not reach the position corresponding to the defective portion on the light receiving surface, and the illuminance decreases.
By visually measuring this illuminance distribution, it becomes possible to perform the same inspection as that conventionally performed on a mirror surface.
The approximate position of this defective portion can be obtained by counting the number of pulses supplied to the stepping motor of the moving mechanism for moving the optical disc. Also, the illuminance distribution may be measured using a photoelectric means.
That is, an image pickup tube of an ITV camera may be provided instead of the screen, and as shown in FIG. 5, it may be found from the cross-sectional intensity of the illuminance distribution 17 imaged by this image pickup tube that the optical disc has a defective portion. May be projected once on the screen and indirectly photographed by the ITV camera.

Since the cylindrical lens 2 is used, the light beam is incident on the surface to be measured in a diverging state without being subjected to a converging (converging) effect in a plane orthogonal to the incident surface, but it can be easily understood. Since any part of the luminous flux is incident on the surface to be measured at an angle larger than the scene critical angle, specular reflection due to a scene phenomenon is realized in all irradiation areas. The advantage of using the cylindrical lens 2 is that the measured region can be wide in the horizontal direction while maintaining the regular reflectance. Especially diameter 130
This method is suitable for inspecting an optical disc having a large size of mm, 300 mm. If the area to be measured is sufficiently small, it goes without saying that a normal spherical lens may be used instead of the cylindrical lens 2.

(Second Embodiment) FIG. 6 is a schematic side view of a second embodiment of the defect inspection apparatus of the present invention. In the figure, reference numeral 1
3 to 3 are the same members as those in the first embodiment, the description thereof will be omitted. The difference from the first embodiment is that the scattered light component shown by the broken line is used for detecting defects without using the specularly reflective light flux 12. As described above, when the light is incident at an angle larger than the scene critical angle, most of the light is reflected sideways as the specularly reflected light 12, and only the scattered light due to the defect is scattered upward. By using the same observation optical system 11 as described above, it becomes possible to visually detect a defect with high sensitivity by a so-called dark field method.

(Third Embodiment) FIG. 7 is a schematic side view of a third embodiment of the defect inspection apparatus of the present invention.

The structure of the defect inspection apparatus of this embodiment is almost the same as that of the second embodiment, except that a polarizer 13 is provided in the projection optical path and an analyzer 14 is added to the observation optical system 11. Different from the second embodiment.

In the polarizer 13 installed in the projected light beam, the polarization state of the light beam passing through the polarizer 13 is S with respect to the incident surface.
The azimuth is determined so that the polarization state is achieved. When the polarization state is determined in this way, the specularly reflective light beam 12 maintains the S polarization state, but the light beam (broken line) scattered by the defect has its polarization state disturbed and generates a component other than the S polarization. An analyzer 14 is installed in the middle of the observation optical system 11 in an orientation that allows only a P-polarized component to pass through with respect to the incident surface, and a scattered light component (apart from specular reflection from a rough surface slightly left by the analyzer ( S component) is removed. Therefore, it becomes possible to detect defects with high sensitivity.

Various modifications as will be described later can be considered in each of the embodiments described above.

As the light source, it is possible to use laser light in addition to the usual high-intensity incandescent light source such as a halogen lamp. When a light source having good coherence such as laser light is used, it is preferable to use light through a vibrating diffusion plate in order to remove a speckle pattern caused by interference of scattered light. The lens used for projecting the light flux is not limited to the above-mentioned cylindrical lens, and may be an ordinary spherical lens, or, as shown in FIG. 8, a divergence angle limiting means having a slit (opening) without using a lens. The slit plate 21 may be provided to limit the divergence angle of the luminous flux so that the incident angles of all the luminous fluxes incident on the measured surface do not exceed the scene critical angle.

The structure of the apparatus can be selected such that a part of the object is irradiated, the entire surface is irradiated all at once according to the size of the object to be measured, and the object to be measured is in a stationary state or rotational scanning for the purpose. A scanning mode can be adopted. In addition, FIG.
As shown in Fig. 3, thin stripe defects are easier to detect when light is projected from the direction orthogonal to the stripes.Therefore, by providing multiple screens and combining irradiation from multiple directions instead of one direction, linear It is also possible to facilitate the detection of defects in the.

The defect detection method is not limited to the above-mentioned visual method, and it goes without saying that it can be combined with a known method such as photoelectrically detecting a defect using an image pickup tube. That is, as shown in FIG. 10, a slice level is set in the illuminance distribution photographed by the image pickup tube, and the defect portion and the defective portion are distinguished by binarization by the slice level, and the defect size and number are automatically determined. You may measure.

Further, as shown in FIG. 11, in order to separate specularly reflected light and scattered light due to defects, a so-called Schlieren optical system in which an imaging lens and a light shielding plate for cutting zero-order light are combined is used in addition to the method described above. Can also be used. When this schlieren optical system is used, the specularly reflected light does not reach the screen, and only the spots scattered by defects in the entire surface are dark and shine.

Further, in each of the above-mentioned embodiments, all of the projected light beams are made incident at the scene critical angle, and the entire light beams are reliably reflected in the scene. However, at least a part of the incident light beams is incident at an angle smaller than the scene critical angle. It should be big.

(Fourth Embodiment) FIG. 12 is a schematic structural view of a fourth embodiment of the defect inspection apparatus of the present invention, FIG. 13 is a top view of the slit shown in FIG. 12, and FIG. 14 is shown in FIG. First
It is a front view of the two-divided sensor.

The defect inspection apparatus of the present invention, as shown in FIG. 12, includes a first illumination device 102 and a first illumination device 102.
Slit 103 for making the luminous flux emitted from the slit shape
And transmits the light flux that has passed through the slit 103, and
Half mirror 104 that reflects the light flux that is reflected and returns again
And the objective lens 105 which forms a slit-shaped image by condensing the slit-shaped light flux transmitted through the half mirror 104 on the surface 101a to be measured of the optical disc 101, and the half mirror 1.
The first two-divided sensor 106 that receives the light flux reflected by 04, and the light flux emitted from the first illuminating device 102 is emitted substantially at right angles to the light flux axis when it is focused on the surface 101a to be measured. And a second lighting device 107 including an LED and a semiconductor laser, and a second lighting device 107.
A first optical path bending mirror 108 that bends a light beam emitted from the optical path and makes it enter the periphery of the objective lens 105;
From the illumination device 107 of the first optical path bending mirror 108
A second optical path bending mirror 109 that bends the light beam that is incident on the periphery of the objective lens 105 via the light source, is condensed on the measured surface 101a of the optical disc 101, is reflected, and is transmitted again through the periphery of the objective lens 105. A second two-divided sensor 110 that receives the light flux that has passed through the second optical path bending mirror 109.
It is integrally held in the optical disk 0 and can be moved in the radial direction of the optical disc 101 indicated by an arrow A in the figure by using a drive mechanism (not shown).

In this defect inspection apparatus, as shown in FIG. 12, the light flux passing through the slit 103 is condensed by the objective lens 105 on the surface 101a to be measured of the optical disc 101 to form an image by the slit 3. The measured surface 101a is, for example, a smooth surface of a protective film applied on the magnetic layer of the magneto-optical disk. The light beam condensed on the surface is reflected and returns to the same optical path again, and the half mirror 104 forms an image by the slit 103 on the light receiving surface of the first two-divided sensor 106.

As shown in FIG. 13, the slit 103 is composed of an opaque portion shown by diagonal lines and a vertically long transparent opening 103a opened in the center thereof. The opening can be formed, for example, by etching a metal thin film or a metal film deposited on a glass substrate.

The light flux which has passed through the opening 103a is shown in FIG.
The first light receiving surface 1 of the first two-divided sensor 106 shown in FIG.
06a and the second light receiving surface 106b above the opening 103a
An image 103b having the same size as the aperture area of is formed. Here, the longitudinal direction of the image 103b formed by the opening 103a and the dividing line of the first two-divided sensor 106 are in the same direction, and the image 103b formed by the opening 103a is evenly applied to the two light-receiving surfaces 106a and 106b. In addition, the positional relationship between the slit 103 and the first two-divided sensor 106 is preliminarily adjusted. The optical disc 101 is rotated around a rotation axis 121 by a rotation mechanism (not shown).
The opening 103a of the slit 103 is arranged so that its longitudinal direction coincides with the radial direction of the optical disc 101. The slit image 103b scans the disk in the circumferential direction as the optical disk 101 rotates. The measurement on the entire surface of the optical disk is performed by the combination of the scanning in the circumferential direction and the movement of the housing 120 in the direction of the arrow A described above. The differential amplifiers connected to the first light-receiving surface 106a and the second light-receiving surface 106b are connected to each other, and the output result from this operational amplifier is subjected to a calculation process described later to detect a defect. The direction, size and amount of the unevenness can be determined.

On the other hand, in FIG. 12, the second illumination light source 1
The light flux (shown by the diagonal lines) emitted from 07 enters the periphery of the objective lens 105 via the first optical path bending mirror 108, is once condensed on the measured surface 101a of the optical disc 101, is reflected, and is again objective. The light enters the second two-divided sensor 110 through the periphery of the lens 105 and the second optical path bending mirror 109. This optical system starting from the second illumination light source 107 is the same as that used in the auto-focus optical system of a microscope and the like and will not be described in detail, but in short, the distance between the measured surface 101a and the optical system in the housing 120 is short. Of the light spot on the second two-divided sensor 110 is detected, and an output proportional to the displacement is detected.
Alternatively, the objective is to feed back to an actuator mechanism (not shown) that moves the objective lens 105 in the vertical direction to keep the focal plane constant. If the depth of focus of the optical system for projecting the image of the slit 103 is sufficiently deep to cover the range of surface wobbling of the optical disc, the above-mentioned autofocus optical system may be omitted. Next, the principle of defect detection in the embodiment will be described with reference to FIGS. Figure 15
FIG. 13 is a diagram showing an image projected on the light receiving surface of the first two-divided sensor shown in FIG. 12, (a) shows a state in which the image is distorted on the first light receiving surface side, and (b) ) Shows a state where the image is straightened, and (c) shows a state where the image is distorted toward the second light receiving surface side. FIG. 16 is a graph showing the differential output on the two light receiving surfaces of the first two-divided sensor shown in FIG. 12 when the defective portion is a protrusion.

As the optical disk rotates, FIG.
The presence of the defective portion indicated by a broken line in FIGS. 1 to (c) moves the light receiving surfaces 106a and 106b of the two-divided sensor from left to right in the figure, and the slit 1 on the light receiving surfaces 106a and 106b.
The image 103b of No. 03 is deformed due to the presence of the defective portion. That is, when a defective portion which is a projection is scanned, the surface of the defective portion exhibits substantially the same action as the convex mirror with respect to the projected slit image, and thus the slit image is applied to the defective portion as the defective portion moves. The part first distorts to the left, becomes almost straight when passing directly above, and then distorts to the right. At this time, the differential output of the signals obtained from the first and second light-receiving surfaces 106a and 106b of the first two-divided sensor 106 has an inverted S-shape corresponding to the passage of the defective portion, as shown in FIG. Draw a curved line.

FIG. 17 is a diagram showing an image projected on the light receiving surface of the first two-divided sensor shown in FIG.
(A) shows a state in which the image is distorted on the second light receiving surface side,
(B) shows a state where the image is straightened, (c)
Shows a state in which the image is distorted on the first light receiving surface side.
FIG. 18 is a graph showing the differential output on the two light-receiving surfaces of the first two-divided sensor shown in FIG. 12 when the defective portion is a hole. If you scan a defective part that is a hole,
Since the surface of the defective portion exhibits almost the same action as that of the concave mirror, the slit image 3 is formed as shown in FIGS.
The order of deformation of b is opposite to that shown in FIG. 15, and as a result, the differential output becomes an S-shaped curve as shown in FIG. Therefore, it is possible to determine the concave-convex direction of the defective portion depending on whether the curve of the differential output is S-shaped or inverted S-shaped.

Furthermore, the approximate size and shape of the defect can be known by measuring the time interval between the maximum and minimum peaks of the curve and the height of the peak.

Here, the general relationship between the size and height (or depth) of the defective portion and the waveform of the differential output from the two-divided sensor will be described.

FIG. 19 is a diagram showing the general relationship between the size and shape of the defective portion and the operation output, and FIG. 19A is a graph showing the operation output by the two-divided sensor on the time axis, and FIG. FIG. 8A is a diagram showing the relationship between the defect size and the differential output graph in the case where the height (depth) of the defect is constant, and FIG. FIG. 5 is a diagram showing a relationship between a height of a defective portion and a graph of differential output.

As can be seen from FIGS. 19B and 19C, the general tendency is that when the height (or depth) of the defect portion is constant and the size of the defect portion becomes large, FIG. The output time interval l appearing on the time axis of the graph shown in FIG. Further, when the size of the defective portion is constant (especially in the case of a rough surface), when the height (or depth) of the defective portion becomes large, the peak h of the operation output of the graph shown in FIG. 19A becomes large. . Therefore, assuming that the slit light scans the surface to be measured of the defective portion at a constant speed, the time axis of the output waveform is proportional to the distance (size), so the approximate size of the defective portion is above a certain level. The output can be determined from the time interval (time interval 1 shown in FIG. 19A) at which the output of (1) appears. On the other hand, the height (or depth) of the defect is
The surface to be measured differs depending on whether it is a glossy surface or a rough surface. In the case of a glossy surface, the curvature of the defect causes a slightly complicated movement, but since the magnitude of the operating output is generally proportional to the height (or depth) of the defect, , Can be determined by calculating from the magnitude of the peak value h of the operation output.

The slit opening 10 used in the apparatus of the present invention.
The size of 3a can be arbitrarily set according to the required detection accuracy and resolution. For example, the width is 0.5m
m, the length is 5 mm, and the imaging magnification of the objective lens is 1/1
If it is 0, the size of the slit image on the surface to be measured 101a is 50 μm × 500 μm, and the detection method using the differential output as described above can sufficiently detect a defect with a size of several μm. Is.

Next, a modification of the fourth embodiment will be described with reference to FIGS. FIG. 20 is a schematic configuration diagram of a six-divided sensor applied to the fourth embodiment of the present invention, and FIG.
Is a front view of the six-division sensor shown in FIG. 20,
(A) shows that the image is slightly distorted to the right,
(B) shows a state in which the image is greatly distorted to the right.

In the modification of this embodiment, the light receiving surface of the sensor is not divided into two as shown in FIG.
It is divided into six parts of 06c to 106h, and from here (106c to 106d), (106e to 106f),
Three types of differential signals (106g to 106h) are obtained. That is, (106c to 106d), (106e to 106)
f) and (106g to 106h), the three pairs of light-receiving surfaces are respectively connected to differential amplifier circuits, and the respective operation signals based on these operation amplifier circuits cause the direction and size of the defective portion to be uneven, The amount is determined.

When the size of the defect portion in the direction orthogonal to the scanning direction is short, the differential output appears only in the portion (106e to 106f) in FIG. 21A, and no other differential output appears. On the other hand, when the size of the defective portion is long, the slit image 103b is greatly distorted, so that the differential output appears in all. According to this, it is possible to obtain information about the size of the defect in the direction orthogonal to the scanning direction.

FIG. 22 is a schematic diagram showing a four-division sensor which is still another example of the division sensor applied to the fourth embodiment of the present invention, in which the image on the light receiving surface is slightly distorted to the left. It shows the state.

In the example shown in FIG. 22, the light receiving surface of the sensor is divided into four arrays 106j to 106m in the scanning direction. Then, (106k to 106l), (1
The differential amplifier circuits are connected to the two pairs of light receiving surfaces (06j to 106m), and the direction, size, amount, etc. of the unevenness of the defective portion are determined by the respective operation signals based on these operation amplifier circuits. It That is, according to this array, (1
The output appears at (06k to 106l) and then (106j to
If it appears at 106 m), the height (or depth) of the defective portion is large, and only at (106 k to 106 l) (106 j to 106 l).
If it does not appear in m), it can be determined that the height (or depth) of the defective portion is small.

(Fifth Embodiment) FIG. 23 is a schematic side view of a fifth embodiment of the defect inspection apparatus of the present invention.

In this embodiment, the measured surface 1 of the optical disk 101 is
This is suitably applied when 01a is a rough surface having fine irregularities.

As shown in FIG. 23, the defect inspection apparatus of this embodiment includes an illuminating device 111, a slit 103 for making a light beam emitted from the illuminating device 111 into a slit shape, and a slit 1.
03, a projection lens 113 for projecting the light flux emitted from the optical disc 101 onto the measured surface 101a of the optical disc 101, and an objective lens 114 for condensing the scattered light scattered because the measured surface 101a is a rough surface. It is composed of a two-divided sensor 115 similar to that of the first embodiment, which receives the light flux from the objective lens 114, and the above-mentioned components are integrally held in the housing 120 and a drive mechanism (not shown) is used. Thus, it is movable in the radial direction of the optical disc 101 indicated by arrow B in the figure.

In the apparatus of the present embodiment, the light beam projected obliquely from above onto the optical disc 101 via the projection lens 113 causes the surface to be measured 101a which is a rough surface of the optical disc 101 to be measured.
The scattered light is condensed by the objective lens 114 and is imaged on the light receiving surface of the two-divided sensor 15.

Next, based on FIGS. 24 to 27, the two-division sensor 11 when scanning over a defect in the apparatus of the present invention.
While explaining the change of the shape of the slit image on 5,
The principle of detecting a defective portion will be described.

FIG. 24 is a diagram showing an image projected on the light receiving surface of the two-divided sensor shown in FIG. 23. FIG. 24A shows a state in which the image is slightly distorted to the second light receiving surface side. Shows,
(B) shows a state where the image is largely distorted on the second light receiving surface side, and (c) shows a state where the image is slightly distorted on the second light receiving surface side. FIG. 25 is a graph showing the differential output on the two light-receiving surfaces of the two-divided sensor shown in FIG. 23 when the defective portion is a protrusion.

As described above, the slit image emitted through the slit 112 is projected obliquely from above by the projection lens 113.
Is projected onto the surface 101a to be measured. Here, when the slit image is scanned on the defect portion which is the protrusion, the image 112b received by the two-divided sensor 115 is generated by scattering, and therefore, in FIGS. 24 (a), (b), and (c). As shown, even if the defective portion moves, the direction of strain is constant, and the amount of deformation only changes gradually. Therefore, the differential output (115a to 115b) obtained from the first light receiving surface 115a and the second light receiving surface 115b becomes a curve as shown in FIG.

FIG. 26 is a diagram showing an image projected on the light receiving surface of the two-divided sensor shown in FIG. 23.
Shows a state in which the image is slightly distorted on the first light receiving surface side, (b) shows a state in which the image is greatly distorted on the first light receiving surface side, and (c) shows the image in the first light receiving surface side. It shows a state where the surface side is slightly distorted. FIG. 27 is a graph showing the differential output on the two light-receiving surfaces of the two-divided sensor shown in FIG. 23 when the defect is a hole.

Even if the defective portion is a hole, even if the defective portion is moved, the direction of strain is constant and the amount of deformation is gradually changed. However, the distortion direction of the image 112b is shown in FIG.
As shown in (a), (b), and (c), the defect is opposite to that when the defect is a protrusion. Therefore, the differential output from the two-divided sensor becomes a curve with the opposite sign shown in FIG. 27 as compared with the curve shown in FIG.

As described above, in this embodiment, since the operation output by the two-divided sensor differs depending on the direction of the defective portion, the unevenness of the defective portion can be determined by the sign of the differential output. Further, the size of the defective portion can be determined from the duration time when the output appears on the time axis.

This embodiment is applied to the case where the surface to be measured is a rough surface, such as an inspection of the surface of a protective film which is roughened for the purpose of preventing adsorption of a magnetic head, such as a magnetic field modulation type optical disk. Suitable for

[0061]

Since the present invention is configured as described above, it has the following effects.

According to the first aspect of the present invention, it becomes possible to detect minute defects existing on a rough surface, which cannot be performed conventionally, very easily and with high sensitivity. It greatly contributes to the improvement of productivity.

In addition to the above effects, the first aspect of the present invention can surely reflect the entire luminous flux in the scene to improve the inspection accuracy.

According to a second aspect of the present invention, a defect or deformation present on the surface such as a reflective smooth surface or a rough surface can be inspected in a non-contact, high-speed and convenient manner from the surface to be measured, and It is possible to determine not only the size but also the direction, amount, and shape of the unevenness, which can contribute to the quality improvement of the optical disc and the like.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a first embodiment of a defect inspection apparatus of the present invention.

FIG. 2 is a schematic side view of the defect inspection apparatus shown in FIG.

3 is a schematic plan view of the defect inspection apparatus shown in FIG.

FIG. 4 is a diagram of an optical system for explaining the principle of the defect inspection of the present invention.

FIG. 5 is a diagram showing a cross-sectional intensity of an illuminance distribution by an image pickup tube.

FIG. 6 is a schematic side view of a second embodiment of the defect inspection apparatus of the present invention.

FIG. 7 is a schematic side view of a third embodiment of the defect inspection apparatus of the present invention.

FIG. 8 is a diagram showing a modified example of the defect inspection apparatus of the present invention, in which a slit plate is provided in place of the cylindrical lens.

FIG. 9 is a diagram showing another modification of the defect inspection apparatus of the present invention, in which light beams are projected from a plurality of directions.

FIG. 10 is a diagram for explaining binarization of the intensity of the illuminance distribution by the image pickup tube.

FIG. 11 is a diagram showing still another modified example of the defect inspection apparatus of the present invention, in the case where a Schlieren optical system is used.

FIG. 12 is a schematic side view of a fourth embodiment of the defect inspection apparatus of the present invention.

13 is a top view of the slit shown in FIG.

FIG. 14 is a front view of the first two-divided sensor shown in FIG.

FIG. 15 is a diagram showing an image projected on the light receiving surface of the first two-divided sensor shown in FIG. 12, and FIG.
Shows a state where the image is distorted on the light receiving surface side, (b) shows a state where the image is straightened, and (c) shows a state where the image is distorted on the second light receiving surface side.

16 is a graph showing a differential output on two light receiving surfaces of the first two-divided photosensor shown in FIG. 12 when the defect is a protrusion.

17 is a diagram showing an image projected on the light receiving surface of the first two-divided sensor shown in FIG. 12, and FIG.
Shows a state where the image is distorted on the light receiving surface side, (b) shows a state where the image is straightened, and (c) shows a state where the image is distorted on the first light receiving surface side.

FIG. 18 is a graph showing differential outputs on two light receiving surfaces of the first two-divided sensor shown in FIG. 12 when the defect is a hole.

FIG. 19 is a diagram showing a general relationship between the size and shape of a defect portion and an operation output, (a) is a graph showing an operation output by a two-divided sensor on a time axis, and (b) is a defect. It is a figure showing the relation between the size of the defective part and the graph of the differential output when the height (depth) of the part is constant,
(C) is a diagram showing the relationship between the height of the defective portion and the differential output graph when the size of the defective portion is constant.

FIG. 20 is a schematic configuration diagram of a six-divided sensor applied to a fourth embodiment of the present invention.

FIG. 21 is a front view of the six-divided sensor shown in FIG. 20, in which (a) shows a state in which the image is slightly distorted to the right,
(B) shows a state in which the image is greatly distorted to the right.

FIG. 22 is a schematic configuration diagram showing a four-division sensor which is still another example of the division sensor applied to the fourth embodiment of the present invention, showing a state where the image on the light-receiving surface is slightly distorted to the left. Shows.

FIG. 23 is a schematic side view of the fifth embodiment of the defect inspection apparatus of the present invention.

24 is a diagram showing an image projected on the light receiving surface of the two-divided sensor shown in FIG. 23, and FIG. 24 (a) shows a state in which the image is slightly distorted toward the second light receiving surface side, b) shows a state in which the image is greatly distorted on the second light receiving surface side, and (c)
Indicates that the image is slightly distorted on the second light receiving surface side.

25 is a graph showing differential outputs on two light receiving surfaces of the two-divided sensor shown in FIG. 23 when the defective portion is a protrusion.

26 is a diagram showing an image projected on the light receiving surface of the two-divided sensor shown in FIG. 23, and FIG. 26 (a) shows a state in which the image is slightly distorted on the first light receiving surface side, (b) shows a state where the image is largely distorted toward the first light receiving surface side, and (c) shows a state where the image is slightly distorted toward the first light receiving surface side.

27 is a graph showing a differential output on two light receiving surfaces of the two-divided sensor shown in FIG. 23 when the defect is a hole.

[Explanation of symbols]

 1 Light Source 2 Cylindrical Lens 3 Optical Disc 4, 22, 23, 32 Screen 5 Measurement Area 6 Reflection Surface (Measurement Surface) 7 Incident Light 8, 12 Regular Reflection Light 9, 10 Light Distribution Characteristics 11 Observation Optical System 13 Polarization Child 14 Analyzer 15 Light receiving portion 16 Dark portion 17 Illuminance distribution 20 Divergence angle 21 Slit plate 24, 34 Measurement surface 25, 26 Light flux 27 Slice level 28 Light receiving portion on screen 29 Schlieren optical system 30 Imaging lens 31 Light-shielding plate 33 Defect 101 Optical disc 101a Surface to be measured 102 First illumination device 103 Slit plate 103a Openings (slits) 103b, 103c, 103d images 104 Half mirror 105 Objective lens 106 First two-divided sensor 106a First light-receiving surface 106b Second light receiving surface 106c to 106m Light receiving surface 107 Second Lighting device 108 First optical path bending mirror 109 Second optical path bending mirror 110 Second two-divided sensor 111 Illuminator 112 Slit plate 112b Image 113 Projection lens 114 Objective lens 115 Two-divided sensor-115a First light receiving surface 115b 2 light receiving surface 116 6-division sensor 117 4-division sensor 120 Housing 121 Rotation axis θ Incident angle α Divergence angle

Claims (7)

[Claims] 1. A light beam projecting means for projecting a light beam onto a surface to be measured having diffuse reflectance so that at least a part thereof is incident at an incident angle larger than a scene critical angle, and the light beam is reflected by the surface to be measured. Or a light receiving unit for receiving the scattered light beam, and the defect detecting unit is used to detect a defect existing on the surface to be measured. 2. The luminous flux projection means includes a divergence angle limiting means for limiting a divergence angle of the luminous flux within an incident plane so that all of the luminous fluxes are incident at an incident angle larger than a scene critical angle. 1. The defect inspection device according to 1. 3. The defect inspection apparatus according to claim 1, wherein the light receiving unit is a screen. 4. The defect inspection apparatus according to claim 1, wherein the light receiving unit is an image pickup tube. 5. An optical system for converging a slit-shaped light beam on a surface to be measured, a moving means for moving the surface to be measured relative to the slit-shaped light beam, and the object to be measured. A photodetector which is provided at a position conjugate with the surface, and which comprises a plurality of light receiving surfaces for receiving the reflected light from the surface to be measured, and a detecting means for detecting a defect by calculating an output obtained from the photodetector. Defect inspection equipment. 6. The longitudinal direction of the slit-shaped light beam is arranged orthogonal to the relative movement direction of the measured surface, and the light-receiving surfaces of the photodetector are arranged in parallel. The defect inspection device according to claim 5. 7. The photodetector is a two-division type photodetector consisting of two light-receiving surfaces adjacent to each other, and the detection means uses a differential output of the two-division type photodetector to detect the light. The defect inspection apparatus according to claim 5 or 6, which determines the size of the defect on the measurement surface, the uneven direction of the defect, and the amount of the defect.