JPH05346555A - Optical trap and image pickup device - Google Patents

Abstract

PURPOSE:To make image processing with a high S/N ratio possible by forming an annular trap hole of a couple of internal and external curved surfaces and narrowing the interval between the couple of curved surface with the distance from the light entrance of the trap hole. CONSTITUTION:The tip parts 10 and 14 of 1st and 2nd housings 8a and 8b are adhered together in one body with an adhesive material, etc., to form the light entrance 17 at the base end parts 9 and 13 of the 1st and 2nd housings 8a and 8b, and a constant space 18 is formed on a more center side than the light entrance 17. The two curved surfaces 12 and 16 formed on the internal surfaces of the 1st and 2nd housings 8a and 8b when the 1st and 2nd housings 8a and 8b are combined are arranged so that the convex surface of one surface and the concave surface of the other face are faced each other, thereby forming the annular optical trap hole 19. The interval between the curved surfaces 12 and 16 which form the optical trap hole 19 becomes narrower with the distance from the light entrance 17 and the innermost part of the optical trap hole 19 is formed at the coupling place of the tip parts 10 and 14 of the 1st and 2nd housings 8a and 8b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical trap suitable for use in a device for capturing an object with a camera and processing an image with a high S / N ratio, and an imaging device using this optical trap.

[0002]

2. Description of the Related Art In an image processing apparatus, when a camera 2 captures a mirror-like object 1 as shown in FIG.
There is a problem that background light is reflected and reflected on the subject 1 over the range indicated by the symbol S. This is because the illumination light from the lamp 3 reflected by the mirror-like subject 1 illuminates the surroundings. As a simple method for treating such unnecessary light, black matte alumite or black matte paint may be applied to the reflecting surface 4 where the illumination light is most strongly reflected. In addition, if necessary, black betting or a non-reflective sheet may be used. In addition, optical traps may be used when there is a need to handle unwanted light more efficiently.

Optical traps are usually made of black glass,
The shape is like a curved conical cylinder. And
Light enters through the light inlet at the base end of the cylinder, travels deep into the trap hole while being reflected, and finally becomes heat and is absorbed. Also, since the tip of the conical cylinder is bent,
Light that enters vertically from the center of the light entrance is always reflected on the way. Therefore, the light entering from the center of the light entrance does not reach the tip of the trap hole without being reflected even once, and as a result, there is no problem that the reflected light leaks from the vicinity of the light entrance.

An example in which such an optical trap is used to process the reflected light from the subject 1 is shown in FIG.

FIG. 7 shows an example in which an optical trap 5 is used for the reflecting surface 4 which reflects the illumination light shown in FIG. 6 most strongly. In this case, after the illumination light from the lamp 3 is reflected by the subject 1, it enters the inside of the light entrance 5a of the light trap 5 and is guided to the depth of the trap hole while being repeatedly reflected between the curved surfaces 5b and 5c. , Becomes heat at the end and is absorbed.
In the configuration example of FIG. 7, the strongest reflected light reflected by the subject 1 is absorbed by the light trap 5, but the light diffusely reflected by the subject or dust in the air illuminates the surroundings brightly. The brightly illuminated background and scattered light from the camera are reflected by the subject 1 and the area S is reflected as noise.

In order to solve the above problems, means shown in FIG. 8 can be considered. In this configuration, a first optical trap 6 is provided at the position of the reflecting surface 4 shown in FIG. 5, and a second optical trap 7 for absorbing reflection is separately provided near the camera 2. The light inlet 7a of the second light trap 7 is arranged near the camera 2, and the light from the background is absorbed by the second light trap 7, so that the background light as in the case of FIG. There is no reflection. However, in the case of FIG.
Since the camera 2 is arranged so as to avoid the second optical trap 7, the axis of the lens of the camera 2 is arranged not at right angles to the subject 1 but at a certain inclination angle, and therefore, the image. There is a problem of distortion.

In order to solve the above problem, means shown in FIG. 9 can be considered. In FIG. 9, the second light trap 7 for absorbing reflection is arranged on the background side so that the axis line passing through the light entrance 7a is perpendicular to the subject 1, and the camera 2 has a peripheral edge of the light entrance 7a. It is provided in a position that does not stick out. Therefore, the irregularly reflected light is absorbed by the second light trap 7 and is not reflected on the camera 2, and the camera 2 can also be arranged vertically to the subject 1, so that the image is not distorted. However, in the configuration of FIG. 8, the second optical trap 7
Since the light entrance 7a must have at least the same diameter as the size of the range S in which the background light is reflected as shown in FIG.
Along with that, the depth dimension also becomes longer, and the second optical trap 7 becomes larger accordingly.

[0008]

As described above, as means for preventing the background light from being reflected and reflected on the subject,
If a conventional optical trap is used, the camera must be tilted or the optical trap must be made sufficiently large, and in the former case, the image is distorted. Further, in the latter case, the distance between the pair of curved surfaces forming the optical trap is widened, the reinforcement structure for that is complicated, and the assembly becomes difficult. In addition, there is a problem in that the positioning of the camera and the optical trap and the supporting structure become complicated.

An object of the present invention is to provide an optical trap which solves the above drawbacks.

[0010]

In order to achieve the above object, an optical trap according to the present invention has an annular trap hole provided by a pair of inner and outer curved surfaces facing each other such that a concave surface and a convex surface face each other. It is characterized in that the distance between the pair of curved surfaces is made narrower as the distance from the light inlet of the trap hole increases.

In the optical trap of the present invention, the pair of inner and outer curved surfaces are formed by a first cylinder and a second cylinder in which the front ends of the curved surfaces are expanded and the middle portion is curved inward. It is preferable that the tips of the first and second cylinders are joined together.

Further, the image pickup device of the present invention may be composed of a light source for irradiating a subject with light, and a television camera in which a lens system is vertically arranged in the space at the center of the optical trap so as to face the subject.

[0013]

According to the present invention, the light entering the trap hole from the light inlet is repeatedly reflected by the curved surface, travels to the back, and is finally absorbed. In addition, since a constant space is formed in the center of the annular trap hole, a camera can be arranged in this space to capture an image while the background light is not reflected on the subject.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. The same elements as those of the conventional example will be described with the same reference numerals.

FIG. 1 is a perspective view of an optical trap, FIG. 2 is an exploded perspective view, FIG. 3 is a sectional view, and FIG. 4 is an explanatory view of a usage example. The optical trap 8 according to this embodiment is configured by combining a first cylindrical body 8a and a second cylindrical body 8b. First
The cylindrical body 8a has a base portion 9 having a small diameter, a tip portion 10 having a large diameter, an intermediate portion 11 is curved inward, and an inner surface thereof is a convex curved surface 12. The second tubular body 8b has a base end portion 13
Has a small diameter, the tip portion 14 has a large diameter, the intermediate portion 15 is curved more inward than the intermediate portion 11 of the first tubular body 8a, and the outside thereof is a concave curved surface 16. The outer diameter of the base end portion 13 of the second tubular body 8b is smaller than the inner diameter of the base end portion 9 of the first tubular body 8a. Then, as shown in FIG. 3, the tip portions 10 and 14 of the first tubular body 8a and the second tubular body 8b are integrally coupled to each other by adhesion or the like, so that the first and second tubular bodies An annular light inlet 17 is formed at the base end portions 9 and 3 of 8a and 8b, and a constant space 18 is formed at a portion closer to the center than the light inlet 17.

When the first cylinder 8a and the second cylinder 8b are combined, one of the two curved surfaces 12 and 16 formed on the inner surface of the first cylinder 8a is a convex surface and the other is a concave surface. An optical trap hole 19 having an annular shape is formed. The curved surfaces 12, 16 forming the optical trap hole 19
Is narrowed as the distance from the light inlet 17 increases, and the tip portions 10, 14 of the first and second cylindrical bodies 8a, 8b are separated.
The innermost part of the optical trap hole 19 is formed at the connecting point of.

As shown in FIG. 4, the optical trap 8 according to the present embodiment is used by arranging the camera 2 in a space 18 formed at the center thereof. In the case of this use example, the camera 2
Is held at the center of the optical trap 8, and the camera 2 and the optical trap 8 are arranged perpendicular to the subject 1. An optical trap 5 having a conventional structure is provided at a position where the illumination light of the lamp 3 is most strongly reflected by the subject 1.

In FIG. 4, the light reflected from the subject 1 toward the rear of the camera 2 enters the inside of the annular light inlet 17 of the optical trap 8 and is repeatedly reflected by the curved surfaces 12 and 16 to repeat the optical trap hole. It is guided to the back of 19 and almost absorbed until it reaches the end. Therefore, when the camera 1 captures the mirror-like subject 1, the background light is not reflected and reflected on the subject 1.

In the embodiment, the first and second cylindrical bodies 8a and 8b forming the optical trap 8 are circular, but the shape is not limited to this, and may be square, hexagonal or other shapes. Further, although the tips of the annular curved surfaces 12 and 16 are curved outwardly, they may be curved inwardly.

In the illustrated example, the optical trap 8 is constructed by combining the first and second cylindrical bodies 8a and 8b, but in addition to this, it is constructed by combining a plurality of block-shaped members. It is also possible (however, not shown).

FIG. 5 shows Si using the optical trap of the embodiment.
It is explanatory drawing of the surface inspection apparatus of a wafer. With this device,
A high-sensitivity television camera 2a is arranged toward the surface of the wafer 1a which is a subject. This television camera 2a is arranged in a space 18 formed in the center of the optical trap 8, and its lens system 2b is positioned perpendicular to the surface of the wafer 1a.

The wafer 1a is irradiated with illumination light from a light source 3a using a Xe-Hg lamp. That is, the light from the light source 3a passes through the first condenser lens 20, the pinhole 21, the second condenser lens 22, and the mask 23,
Further, after the course is bent by the reflection mirror 24, the projection lens 25 irradiates the wafer 1a.

The light regularly reflected from the wafer surface is absorbed by an optical trap (not shown) provided separately. The scattered light due to particles or scratches on the surface of the wafer 1a enters the lens system 2b of the television camera 2a and appears on the monitor screen to inspect defective products. In this wafer inspection apparatus, since the light inlet 17 of the optical trap 8 is located around the television camera 2a, the light reflected by the wafer 1a is reflected by the wafer 1a, and the light traveling toward the background side is absorbed by the optical trap 8, so that the background light is reflected by the wafer 1a. There is no problem of being reflected on the wafer and reflected on the TV camera 2a, and scratches and haze scratches on the wafer can be easily confirmed.

[0024]

As described above, the optical trap of the present invention prevents background light from being reflected on an object and reflected in an image in an apparatus for processing an image which requires a particularly high S / N ratio. It is suitable for use as an optical trap for absorbing reflections that is provided to protect the image. That is, the optical trap of the present invention has an annular trap hole, and a camera or the like can be arranged vertically in the space formed in the center of the trap hole with respect to the subject. As a result, it is possible to smoothly absorb the reflected light from the subject without distorting the image and process the image with a high S / N ratio. Moreover, the camera can be easily and surely positioned and fixed with respect to the optical trap. Further, since the optical trap is formed by bending a pair of inner and outer curved surfaces into an annular shape, the optical trap of the present invention is stronger than the conventional optical trap in structure when the diameter of the light inlet is the same. This makes it possible to easily assemble and manufacture it.

[Brief description of drawings]

FIG. 1 is a perspective view of an optical trap according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of the optical trap of FIG.

3 is a cross-sectional view of the optical trap of FIG.

FIG. 4 is an explanatory diagram of a usage example of the optical trap of FIG.

FIG. 5 is an explanatory diagram of a surface inspection apparatus for a Si wafer using the optical trap of the present invention.

FIG. 6 is an explanatory diagram showing a relationship among a camera, a subject, and reflected light.

FIG. 7 is an explanatory diagram of a first example showing a relationship between a camera, a subject, and reflected light when an optical trap is used.

FIG. 8 is an explanatory diagram of a second example of the same.

FIG. 9 is an explanatory diagram of a third example of the same.

[Explanation of symbols]

1 ... Subject, 8 ... Optical trap, 8a ... 1st cylinder, 8b
... 2nd cylinder, 9 ... Base end part, 10 ... Tip part, 11 ... Intermediate part, 12 ... Curved surface, 13 ... Base end part, 14 ... Tip part, 15
... middle part, 16 ... curved surface, 17 ... light inlet, 18 ... space, 19 ... light trap hole.

Claims (3)

[Claims] 1. An annular trap hole is provided by a pair of inner and outer curved surfaces facing each other such that a concave surface and a convex surface face each other, and the interval between the pair of curved surfaces is narrowed as the distance from the light inlet of the trap hole increases. An optical trap characterized in that. 2. A pair of the inner and outer curved surfaces is formed by a first cylinder and a second cylinder each having a diameter enlarged at a tip end side and an intermediate portion curved inward, and a first cylinder and a second cylinder. The optical trap according to claim 1, wherein the tips of the optical traps are joined together. 3. A light source for irradiating a subject with light, and
An image pickup device comprising: a television camera in which a lens system is vertically arranged so as to face a subject in a space in a central portion of the optical trap described in.