JPH08220016A - Optical device for detecting defect - Google Patents

Abstract

PURPOSE: To obtain an optimum lighting method for various kinds of materials to be inspected readily. CONSTITUTION: Parallel luminous flux transmitted through a two-dimensional light bulb 4 is reflected from a parabolic mirror 5 and converged. A material under inspection 6, which is arranged in the vicinity of the focal point of the parabolic mirror 5 is lit by the convergent light. At this time, the transmittance of the two-dimensional light bulb 4 is changed for every segment region by a control part 8. Thus, the intensity of the illuminating light to the material under inspection 6 is set for every incident direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect detecting optical device used in a defect inspection apparatus for inspecting defects such as cracks and scratches in mechanical parts and the like.

[0002]

2. Description of the Related Art Conventionally, attempts have been made to try to detect defects such as cracks and scratches in mechanical parts by using a CCD camera and image processing technology instead of visual inspection, and have been put to practical use as a defect inspection device. . Although the performance and functions of the CCD camera and the image processing technology used in this defect inspection device have been remarkably improved, whether or not defects can be effectively detected depends largely on the image quality of the inspected object. ,
Furthermore, this image quality depends largely on how the object to be inspected is illuminated.

In the conventional optical device for defect detection used in the above defect inspection apparatus, the type of light source such as a flat lamp or a ring light source or the position of the light source with respect to the inspection object is changed for each inspection object. By changing the illumination method such as the illumination position and the illumination angle, an optimal illumination method according to various inspected objects having different shapes is found by trial and error.

[0004]

However, determining the illumination method by trial and error as in the above-mentioned conventional optical apparatus for defect detection requires a great deal of time and labor, and also requires a high degree of freedom in selecting the illumination method. Is limited. Further, it is difficult to accurately record the illumination method once determined, and it takes time and time to accurately reproduce the illumination method with a deadline.

An object of the present invention is to solve the above problems, and an object thereof is to provide an optical device for defect detection which makes it possible to easily obtain an optimal illumination method for various inspection objects.

[0006]

In order to achieve the above object, the present invention provides a defect inspection apparatus for inspecting a defect of an inspected object by receiving reflected light from an illuminated inspected object by an image pickup means. A light source unit that outputs a light beam including a parallel light beam; a light amount adjusting unit that is disposed in the parallel light beam and that adjusts the amount of light emitted at each incident position of the parallel light beam; and a focus on the inspected object. And a focusing optical system for reflecting the parallel light flux emitted from the light quantity adjusting means and focusing the parallel light flux on the object to be inspected.

[0007]

According to the present invention, the parallel light flux emitted from the light quantity adjusting means is reflected by the focusing optical system and focused, and the focused light illuminates the object to be inspected. At this time, the light amount is adjusted for each incident position of the parallel light flux. Therefore, since each light beam in the parallel light beam is incident on the inspection object at an incident angle corresponding to the position, the intensity of the illumination light that illuminates the inspection object is adjusted for each incident direction.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a first embodiment of the defect detecting optical device according to the present invention will be described with reference to the drawings. FIG.
FIG. 3 is a configuration diagram of the first embodiment.

The optical device for defect detection of the first embodiment comprises a light source 1, a diffusion plate 2, a collimator 3, a two-dimensional light valve 4,
The inspected object 6, the parabolic mirror 5, and the CCD camera 7 are arranged in this order on the optical axis L, and further, the control section 8 and the monitor 17 are provided.
And so on.

The light source 1 emits light to illuminate the inspection object 6 and is composed of a fluorescent lamp, a xenon lamp, a halogen lamp or the like. The diffuser plate 2 is, for example, a disc shape and diffuses the incident light from the light source 1. Collimator 3
Is composed of, for example, a circular convex lens, and collimates a light flux emitted from an intersection with the optical axis L on the diffusion plate 2 (hereinafter referred to as an optical axis center). The light source 1, the diffusion plate 2, and the collimator 3 constitute a light source section.

The two-dimensional light valve 4 is, for example, a disk-shaped member having substantially the same radius as the collimator 3, and is made of a material such as liquid crystal or PLZT whose transmittance of incident light can be changed for each segment area. The parabolic mirror 5 reflects the transmitted light of the two-dimensional light valve 4, and constitutes a focusing optical system that reflects the incident parallel light flux and focuses it on the focal point 5a. In the center of the parabolic mirror 5, an opening 5b for observing the inspection object 6 with the CCD camera 7 is formed. The inspection object 6 has, for example, a disc shape and is arranged near the focal point 5 a of the parabolic mirror 5. The CCD camera 7 is, for example, an image pickup unit including a photoelectric conversion element such as a photodiode, and receives the light reflected by the illuminated inspection object 6 and passing through the opening 5b to observe the inspection object 6. Is.

The monitor 17 displays an image of the inspection object 6 taken by the CCD camera 7. Control unit 8
Includes a memory 81 and includes a microcomputer, a light valve control circuit, and the like. The input section 9 is
It consists of a keyboard, mouse, etc. and is connected to the control unit 8.
The transmittance pattern and the like of the two-dimensional light valve 4 are set and operated.

The control unit 8 controls the transmittance of incident light for each segment area over the entire surface of the two-dimensional light valve 4, and the light amount is adjusted by the control unit 8 and the two-dimensional light valve 4. Means are configured.

The control unit 8 also has a function of causing the memory 81 to store the transmittance pattern for each segment area of the two-dimensional light valve 4 in accordance with the operation of the input unit 9. It also has a function of reading out and reproducing the transmittance pattern stored in the memory 81.

With the above-mentioned structure, the light flux from the light source 1 illuminates the diffusion plate 2 to form a surface light source having a predetermined area. Then, as shown in FIG. 1, the light flux from the center of the optical axis of the diffusion plate 2 becomes a parallel light flux by the collimator 3, passes through the two-dimensional light valve 4, is reflected by the parabolic mirror 5, and forms a parabolic surface. It is focused on the focal point 5a of the mirror 5, and the inspected object 6 is illuminated by this focused light. Illuminated inspection object 6
Is C through the opening 5b provided at the center of the parabolic mirror 5.
Observed by the CD camera 7.

Then, the operator looks at the image taken by the CCD camera 7 on the monitor 17 and the two-dimensional light valve 4
By controlling the transmission pattern of, the illumination light intensity of the inspection object 6 is set for each incident angle.

Here, one ray 3a in the parallel light flux and the optical axis L
When the distance between and is da, the angle between the light ray 3a and the optical axis L when the light ray 3a is reflected by the parabolic mirror 5 toward the focal point 5a, that is, the incident angle θa is expressed by the formula 1.

[0018]

## EQU1 ## θa = 2 · tan ^-1 (da / 2f) where f is the focal length of the parabolic mirror 5.

By controlling the transmittance of the segment area 4a of the two-dimensional light valve 4, the intensity of the light ray 3a can be controlled.

Next, an example of the transmission pattern of the two-dimensional light valve 4 will be described with reference to FIGS. FIG.
FIG. 3 is a view of the two-dimensional light valve 4 viewed from the direction of the CCD camera 7.

In FIG. 2, passing points of the light rays 3a and 3x are shown. Here, when the ray 3x, that is, the distance between the segment region 4x of the two-dimensional light valve 4 and the optical axis L is dx, the incident angle θx is

[0022]

[Expression 2] θx = 2 · tan ⁻¹ (dx / 2f)

As described above, by controlling the transmittance of the segment region 4x of the two-dimensional light valve 4 through which the light ray 3x passes, the intensity of the light ray 3x that illuminates the object 6 to be inspected at the azimuth angle φ and the incident angle θx. Can be controlled.

Therefore, since the transmittance of all the segment areas of the two-dimensional light valve 4 can be controlled for each individual area, as shown in FIG. It can be controlled for each angle and incident angle.

Further, in FIG. 3, the luminous flux incident area 41 of the two-dimensional light valve 4 is divided into four areas 42 to 45. That is, the region 42 is a circular region from the center to a radius of 0.54f,
The area 43 is an annular area having a radius of 0.54f to 0.83f, the area 44 is an annular area having a radius of 0.83f to 1.15f, and an area 45.
Is an annular region having a radius of 1.15f to 2f. The light transmission range of the region 42 is an annular region excluding the central portion blocked by the inspection object 6.

In this case, assuming that the transmittance of the regions 42 and 44 is 0 and the transmittance of the regions 43 and 45 is 1, the inspection object 6
Is an incident angle of 30 ° to 45 ° and 60 ° to 9 with respect to the optical axis L.
It is illuminated with a cone of light with an incident angle of 0 °.

Therefore, the transmittance of each of the regions 42 to 45 is 0 to
4 with the desired strength by setting between 1 and 4
The inspected object 6 can be illuminated with two conical light beams. Further, by changing the transmittance for each segment area in each area, the illumination light intensity can be changed by the azimuth angle in the conical light flux.

Illumination of the object 6 to be inspected by the light rays passing through the same segment area of the two-dimensional light valve 4 will be described with reference to the configuration diagram of FIG.

Since the two-dimensional light valve 4 is arranged in the vicinity of the focal point 5a of the parabolic mirror 5, a plurality of light fluxes passing through the one segment area 4a at different incident angles are reflected by the parabolic mirror 5. After being reflected, the light flux becomes almost parallel. For example, as shown in FIG. 4, the optical axis center 2c of the diffusion plate 2
And light rays 1c, 1h, and 1g which are emitted from the two points 2h and 2g and pass through the collimator 3 and the segment area 4a of the two-dimensional light valve 4 have the centers 6c and two points of the inspection object 6 at substantially the same incident angle. Illuminate 6h and 6g.

As described above, the light flux passing through one segment area of the two-dimensional light valve 4 becomes a parallel light flux having an azimuth angle and an incident angle determined by the position of the segment area, and illuminates the entire surface of the inspection object 6. . Therefore, by controlling the transmittance of the segment area, the intensity of the illumination light can be controlled.

As described above, according to the first embodiment, the transmittance of the two-dimensional light valve 4 is controlled for each segment area, so that the inspection object 6 is spatially directed to the object 6 with a simple structure. The intensity of the illumination light can be easily set.
In addition, since the transmittance pattern of the two-dimensional light valve 4 is stored in the memory 81, the transmittance pattern stored in the memory 81 is read out to instantaneously determine the intensity pattern of the illumination light used in the past. Can be accurately reproduced.

Next, a second embodiment of the defect detecting optical device according to the present invention will be described with reference to the block diagram of FIG.
In the following embodiments, the same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

The defect detecting optical device according to the second embodiment has the first structure.
A glass plate 10 is arranged in place of the two-dimensional light valve 4 in the embodiment, and the inspection object 6 is arranged on the glass plate 10 arranged near the focal plane of the parabolic mirror 5. Also,
Instead of the light source 1, the diffusion plate 2 and the collimator 3, the CRT 31 is arranged so that the fluorescent screen is located immediately upstream of the glass plate 10 and constitutes a light source section. Further, the control unit 8
The brightness of each light emitting point on the phosphor screen of the CRT 31 is controlled.

Then, as shown in FIG. 5, the component parallel to the optical axis of the light flux output from the CRT 31 is reflected and focused by the parabolic mirror 5, and the inspected object 6 is illuminated by the focused light. .

Further, since the phosphor screen of the CRT 31 is located near the focal plane of the parabolic mirror 5, different emission from one light emitting point on the phosphor screen is performed as in the case of FIG. 4 of the first embodiment. After being reflected by the parabolic mirror 5, the plurality of angular light beams become parallel light beams having an azimuth angle and an incident angle determined by the position of the light emitting point, and the parallel light beams illuminate the inspection object 6.

Therefore, according to the second embodiment, the CRT 31
By controlling the brightness of each light emitting point on the phosphor screen by the control unit 8, the same effect as in the first embodiment can be obtained.

Next, a third embodiment of the defect detecting optical device according to the present invention will be described with reference to the configuration diagram of FIG.

The defect detecting optical device of the third embodiment is the first
In addition to the embodiment, a second two-dimensional light valve 11 is arranged immediately downstream of the diffusion plate 2. Also,
The control unit 8 controls the first and second two-dimensional light valves 4, 11
The transmittance of is controlled for each segment area.

With this configuration, the transmission pattern of the second two-dimensional light valve 11 is imaged on the focal plane of the parabolic mirror 5 by the collimator 3 and the parabolic mirror 5.

For example, in FIG. 6, the second two-dimensional light valve 11 is controlled so that only the segment region 11k transmits light, and the two-dimensional light valve 4 controls only the segment regions 4a and 4g. . In this case, the area 6k of the inspection object 6 determined by the segment area 11k is the light ray 1 having the incident angle determined by the positions of the segment areas 4a and 4g.
Illuminated by a, 1k.

As described above, in the third embodiment, the illumination area of the inspection object 6 can be set by the transmission pattern of the second two-dimensional light valve 11. Furthermore, by combining with the transmission pattern of the two-dimensional light valve 4, both the illumination area and the illumination direction for the inspection object 6 can be set.

Therefore, one or a plurality of desired regions of the inspection object 6 can be illuminated from one or a plurality of desired directions. Further, the intensity of the illumination light can be changed for each area and direction.

Further, the shutter time of the CCD camera 7 is extended, during which the combination of the illumination area and the illumination direction is sequentially switched to illuminate from different directions for each area, and they are combined to synthesize an image of the entire inspection object 6. Can be obtained.

In this embodiment, the same effect can be obtained even if a CRT is used instead of the light source 1, the diffusion plate 2 and the second two-dimensional light valve 11.

Next, a fourth embodiment of the defect detecting optical device according to the present invention will be described with reference to the block diagram of FIG.

The optical device for defect detection of the fourth embodiment comprises a light source 1, a diffusion plate 2, a lens 14, a two-dimensional light valve 4, a lens 13, a second two-dimensional light valve 11, a lens 1.
2, a collimator 3, a glass plate 10, an object to be inspected 6, a parabolic mirror 5 and a CCD camera 7 are arranged in this order on the optical axis L.

The lens 14 is a convex lens and is arranged so that the focal point is located at the center of the optical axis of the diffusion plate 2.
The light source 1, the diffusion plate 2 and the lens 14 constitute a light source section. The lens 13 is composed of a convex lens, has a focal length shorter than that of the collimator 3, and is arranged so that the focal point is located on the second two-dimensional light valve 11. The lens 12 is a convex lens, and is closely arranged on the second two-dimensional light valve 11. In addition, the inspection object 6
Are arranged near the focus of the parabolic mirror 5 on the glass plate 10.

With the above structure, the light flux from the center of the optical axis of the diffuser plate 2 illuminated by the light source 1 becomes a parallel light flux by the lens 14, passes through the two-dimensional light valve 4, and then is again focused by the lens 13. Focus. Then, the light flux that has passed through the second two-dimensional light valve 11 and the lens 12 becomes a parallel light flux by the collimator 3, passes through the glass plate 10, is reflected by the parabolic mirror 5, is focused, and is the focused light. Thus, the inspection object 6 is illuminated.

Here, the lens 12, together with the collimator 3 and the lens 13, forms an enlarged image of the two-dimensional light valve 4 on the focal plane of the parabolic mirror 5. Therefore, the two-dimensional light valve 4 is the two-dimensional light valve 4 of the first and third embodiments.
Will perform the same function as.

In this way, by controlling the transmittance of the two-dimensional light valve 4 for each segment area, the intensity pattern of the parallel light flux incident on the parabolic mirror 5 can be set. Thereby, similarly to the first and third embodiments, the intensity of the illumination light to the inspection object 6 can be controlled for each incident direction.

Further, by controlling the transmittance of the second two-dimensional light valve 11 for each segment area, the illumination area of the inspection object 6 can be set as in the third embodiment.

Further, the inspection object 6 and the two-dimensional light valve 4
Both can be placed in the focal plane of the parabolic mirror 5.
Therefore, this embodiment is effective especially when the inspection object 6 has a large thickness.

In this embodiment, the two-dimensional light valve 4 having a smaller size than the first and third embodiments can be used.

If the second two-dimensional light valve 11 is omitted in this embodiment, the same operation as in the first embodiment,
Those having an effect are obtained.

[0055]

As described above, according to the present invention,
Since the light amount of the light beam incident on the light amount adjusting means is adjusted for each incident position of the parallel light beam, it is possible to easily set the intensity of the illumination light to the inspection object for each incident direction.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of an optical device for defect detection according to the present invention.

FIG. 2 is a view of the two-dimensional light valve 4 seen from the direction of a CCD camera 7, showing an example of a transmission pattern on the two-dimensional light valve.

FIG. 3 is a view of the two-dimensional light valve 4 seen from the direction of the CCD camera 7, showing another example of the transmission pattern on the two-dimensional light valve.

FIG. 4 is a configuration diagram of the first embodiment and is a two-dimensional light valve 4.
2 shows an example of light rays that pass through the same segment area of.

FIG. 5 is a configuration diagram of a second embodiment of the defect detecting optical device according to the present invention.

FIG. 6 is a configuration diagram of a third embodiment of an optical device for defect detection according to the present invention.

FIG. 7 is a configuration diagram of a fourth embodiment of the defect detecting optical device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 light source 2 diffuser plate 3 collimator 31 CRT 4 two-dimensional light valve (light quantity adjusting means) 5 parabolic mirror (focusing optical system) 6 inspected object 7 CCD camera (imaging means) 8 control unit (light quantity adjusting means) 81 memory 9 Input Section 10 Glass Plate 11 Second Two-Dimensional Light Valve (Light Quantity Adjusting Means) 12, 13, 14 Lens 17 Monitor

Claims (1)

[Claims] 1. A defect inspection apparatus for inspecting a defect of an object to be inspected by receiving reflected light from an illuminated object to be inspected by an image pickup means, and a light source section for outputting a light beam including a parallel light beam, and the parallel light beam. Light quantity adjusting means arranged inside the light quantity adjusting means for adjusting the quantity of light emitted for each incident position of the parallel light flux, and the parallel light flux emitted from the light quantity adjusting means arranged so that the focus is located on the object to be inspected. An optical device for defect detection, comprising: a focusing optical system that reflects and focuses the light on the object to be inspected.