JP2000149607A - Lighting system and examination method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting system facilitating the change of the irradiated area size and the irradiated NA, and increasing the operability for changing a lamp. SOLUTION: A lighting system has a light condensing optical system 2 condensing the light flux from a light source 1, a fiber bundle 31 having an incoming end positioned near the light condensing position of the light condensing optical system, a condenser optical system 4 introducing the light flux from an outgoing end of the fiber bundle 31 to an irradiated surface 5. Large number of optical element fibers constituting the fiber bundle 31 have a cross section with a size changing almost linearly from the incoming end to the outgoing end. The fiber bundle 31 is constituted as changeable with other fiber bundles (32, 33).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device and an inspection method using the lighting device.
The present invention relates to a lighting device suitable for inspection of output uniformity of a three-dimensional light receiving element.

[0002]

2. Description of the Related Art For example, in order to illuminate a light receiving surface of a CCD and to check the uniformity of the output of the CCD based on the output of each minute pixel, an illuminating device having high uniformity of light quantity on a surface to be illuminated is used. FIG. 2 is a diagram schematically showing a configuration of a conventional illumination device of this type. In FIG. 2, a light beam emitted from a light source 21 such as a halogen lamp is
After being converted into a parallel light beam through the collimator lens 22, the light beam enters the fly-eye integrator 23. The light beam incident on the fly-eye integrator 23 is two-dimensionally split by a number of lens elements constituting the fly-eye integrator 23, and forms a number of light source images at the rear focal position (ie, near the exit end).

[0003] Light beams from a large number of light source images formed at the rear focal position of the fly-eye integrator 23 are converted into parallel light beams by a condenser lens 24, and are converted to an illuminated surface 25 such as a light receiving surface of a CCD to be inspected. Illuminate in a superimposed manner. The condenser lens 24 is disposed so as to perform so-called Koehler illumination on the irradiated surface 25 using a large number of light source images formed at the rear focal position of the fly-eye integrator 23 as secondary light sources. Thus, in the illumination device shown in FIG. 2, the irradiated surface 25 is illuminated with a substantially uniform light amount.

[0004]

However, in the above-described conventional lighting apparatus, the size of the illuminated area is uniquely determined by the F-number of each lens element of the fly-eye integrator 23 and the focal length of the condenser lens 24. Therefore, the size of the irradiation area cannot be easily changed. Also, for similar reasons,
The numerical aperture of the light beam incident on the irradiation surface 25, that is, the irradiation N
A could not be easily changed. As a result, depending on the size of the CCD to be inspected, there is a disadvantage that the inspection itself becomes impossible or a large light amount loss occurs.

Further, in the above-described conventional illuminating device, components from the light source 21 to the condenser lens 24 are integrally accommodated in one box. Therefore, if the lamp constituting the light source 21 needs to be replaced due to its life, the entire apparatus is moved to a predetermined work place, and then the lamp is removed and a new lamp is attached.
The entire apparatus had to be returned to its original position. That is, the conventional lighting device has a disadvantage that the workability of lamp replacement is poor.

In the above-described conventional illuminating device, a method of changing the focal length of the condenser lens 24 to change the size of the irradiated area by forming the condenser lens 24 with a zoom lens is adopted. Sometimes. However, in this case, the telecentricity of the illumination generally collapses, and the uniformity of the light amount on the surface to be irradiated is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and can not only illuminate with a uniform light amount without losing the light amount with a simple configuration, but also can reduce the size of the irradiation region and the irradiation NA. It is an object of the present invention to provide a lighting device that can easily change the lamp size and has improved workability for lamp replacement. It is another object of the present invention to provide an inspection method capable of accurately and quickly inspecting the output uniformity of a two-dimensional light receiving element such as a CCD using the illumination device of the present invention.

[0008]

In order to solve the above-mentioned problems, the present invention provides a light source for supplying an illumination light beam, a condensing optical system for condensing a light beam emitted from the light source, A fiber bundle, which is formed by bundling a large number of fiber strands and has an incident end positioned near the light condensing position of the light condensing optical system, and for guiding a light beam from the exit end of the fiber bundle to an irradiated surface. Wherein each of the plurality of fiber strands constituting the fiber bundle has a cross section of which the size changes substantially linearly from an input end to an output end, and the fiber bundle includes The lighting device is configured to be replaceable with the fiber bundle of the above.

According to a preferred aspect of the present invention, a plurality of fiber bundles having different ratios between the diameter of the exit end face and the diameter of the entrance end face of each fiber strand are provided, and one fiber bundle selected from the plurality of fiber bundles is provided. Two fiber bundles are removably mounted in the optical path between the condenser optics and the condenser optics. Also,
It is preferable that the fiber bundle is configured by randomly bundling the plurality of fiber strands. Further, when the diameter of the entrance end face of each fiber strand constituting the fiber bundle is Di and the diameter of the exit end face of each fiber strand is Do, 0.5 ≦ Do / Di
It is preferable to satisfy the condition of ≦ 2.

According to another aspect of the present invention, a light-receiving surface of a two-dimensional light receiving element to be inspected is illuminated using the lighting device of the present invention, and the light receiving surface of the two-dimensional light receiving element illuminated by the lighting device is illuminated. An inspection method is provided wherein the output uniformity of the two-dimensional light receiving element is inspected based on the output of each light receiving area. In this case, it is preferable that the lighting device illuminates the light receiving surface of the two-dimensional light receiving element with Koehler illumination.

[0011]

In the present invention, a light beam emitted from a light source is condensed by a condensing optical system such as a collector lens, and a light source image is formed at the condensing position. An entrance end of a fiber bundle (fiber bundle) formed by bundling a large number of fiber strands is disposed near the light condensing position, that is, the position where the light source image is formed. That is, the condensing optical system has a light source having a desired size corresponding to the incident end face of the fiber bundle and a desired NA (numerical aperture of a light beam incident on the fiber bundle from the light source image) corresponding to the characteristics of each fiber strand. Form an image.

In the present invention, each fiber strand constituting the fiber bundle has a cross section whose size changes almost linearly from the entrance end to the exit end. In the present invention, the fiber bundle is configured to be exchangeable with another fiber bundle. Specifically, a plurality of fiber bundles having different ratios Do / Di between the diameter Do of the exit end face and the diameter Di of the entrance end face of each fiber strand are provided, and one fiber bundle selected from the plurality of fiber bundles is provided. Is removably mounted in the optical path between the condenser optical system and the condenser optical system.
Here, a plurality of fiber bundles have a ratio Do / D
It may include a fiber bundle with i = 1, that is, a normal fiber bundle composed of a fiber strand having a constant cross section from the entrance end to the exit end.

The light flux from the light source image formed near the incident end face of the fiber bundle reaches the exit end of each fiber strand, that is, the exit end of the fiber bundle after repeating total reflection inside each fiber strand. . Thus, a light source image having a predetermined size and NA is formed on the emission end face of the fiber bundle. The light beam emitted from the emission end of each fiber strand constituting the fiber bundle is guided to the irradiated surface via the condenser optical system. Specifically, the light beam from the exit end of each fiber strand is converted into a substantially parallel light beam by the condenser optical system, and illuminates the irradiated surface in a superimposed manner. Thus, the illumination device of the present invention can illuminate the illuminated surface with a uniform light amount with a simple configuration without loss of light amount.

According to the present invention, the diameter Ii and the numerical aperture NAi (numerical aperture of the light beam incident on the fiber bundle) of the light source image formed near the incident end face of the fiber bundle via the condensing optical system, The relationship expressed by the following equation (1) is established between the diameter Io of the light source image formed on the emission end face and the numerical aperture NAo (numerical aperture of the light beam emitted from the fiber bundle), if the transmission loss of the fiber is ignored. I do. Ii · NAi = Io · NAo (1) Since this relationship naturally holds for each strand of the fiber, the relationship of Expression (1) is equivalent even if it is expressed by the following Expression (2). Di · NAi = Do · NAo (2)

As described above, the diameter Io of the light source image formed on the exit end face of the fiber bundle is equal to the diameter Ii of the light source image formed near the incident end face of the fiber bundle.
o / Di times. The numerical aperture of the light source image formed on the exit end face of the fiber bundle, that is, the numerical aperture NAo of the light beam emitted from the fiber bundle, is the numerical aperture of the light source image formed on the exit end face of the fiber bundle, that is, the incident light flux on the fiber bundle. Of numerical aperture NAi of
It changes i / Do times.

On the other hand, the size of the irradiated area is determined depending on the numerical aperture NAo of the light beam emitted from the fiber bundle and the focal length f of the condenser optical system. That is, the size of the irradiated region is determined by the numerical aperture NAi of the light beam incident on the fiber bundle and the ratio D of the fiber bundle.
o / Di and the focal length f of the condenser optical system. Here, the values of the numerical aperture NAi of the light beam incident on the fiber bundle and the focal length f of the condenser lens are usually fixed values peculiar to the apparatus, and the ratio Do / Di of the fiber bundle is a value that changes by replacing the fiber bundle. It is. Therefore, the size of the irradiation area is changed depending on the change in the ratio Do / Di of the fiber bundles by replacing the fiber bundle. More specifically, since the size of the irradiated area is proportional to the numerical aperture NAo of the light beam emitted from the fiber bundle, it is inversely proportional to the ratio Do / Di of the fiber bundle.

The numerical aperture of the light beam incident on the irradiated surface, that is, the irradiated NA, is determined depending on the diameter Io of the light source image formed on the exit end face of the fiber bundle and the focal length f of the condenser lens. . That is, the irradiated NA
Is the diameter Ii of the light source image formed near the entrance end face of the fiber bundle and the ratio Do /
It is determined depending on Di and the focal length f of the condenser lens. Here, the value of the diameter Ii of the light source image formed near the entrance end face of the fiber bundle and the value of the focal length f of the condenser lens are usually fixed values inherent to the apparatus, and the ratio Do / Di of the fiber bundle is determined by the fiber bundle. Is a value that changes due to the exchange of Therefore, similarly to the size of the irradiation area, the irradiation NA is changed depending on the change of the fiber bundle ratio Do / Di by replacing the fiber bundle. More specifically, the irradiated NA is proportional to the diameter Io of the light source image formed on the emission end face of the fiber bundle, and therefore proportional to the ratio Do / Di of the fiber bundle.

As described above, in the present invention, the ratio Do / D
The size of the irradiation area and the irradiation NA can be easily changed only by appropriately switching the fiber bundles used among the plurality of different fiber bundles of i. In the present invention, a fiber bundle is used as a light homogenizing element. However, in order to disperse the brightness unevenness of a light source image formed in the vicinity of the incident end face of the fiber bundle, each of the fiber strands on the incident end face and the emission end are dispersed. It is preferable to form a fiber bundle by randomly bundling a large number of fiber wires so that the positional relationship between the end face and each fiber wire does not correspond.

Further, in the present invention, the fiber bundle is removably mounted in the optical path between the light source section including the light source and the condensing optical system and the irradiation section including the condenser optical system. For this reason, when actually configuring the lighting device of the present invention, the light source box that houses the light source unit and the irradiation box that houses the irradiation unit can be mechanically separated. Therefore, even if replacement is necessary due to the life of the lamp constituting the light source, only the relatively small and light source box is moved to a predetermined work place without moving the entire apparatus, and after replacing the lamp, You just have to return to the original position. That is, in the lighting device of the present invention, the workability of lamp replacement is significantly improved. As described above, in the lighting device of the present invention, it is possible not only to illuminate with a uniform light amount without losing the light amount with a simple configuration, but also to easily change the size of the irradiation area and the irradiation NA. And the workability of lamp replacement is improved.

Therefore, using the lighting device of the present invention,
For example, by illuminating the light-receiving surface of a two-dimensional light-receiving element such as a CCD with a uniform amount of light, output uniformity inspection can be accurately performed based on the output of each minute pixel of the CCD. Particularly, in the case of a CCD, there are various sizes, but in the lighting device of the present invention, the size of the irradiation area and the irradiation NA can be easily changed.
The output uniformity can be accurately and promptly inspected by uniform light quantity illumination with no light quantity loss by appropriately changing the size of the irradiation area according to the change in the size of the CCD to be inspected.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram schematically illustrating a configuration of a lighting device according to an embodiment of the present invention. In the illumination device of FIG. 1, a light beam emitted from a light source 1 such as a halogen lamp is collected by a collector lens 2 to form a light source image having a predetermined size and NA. At the position where the light source image is formed, an incident end of a fiber bundle 31 configured by randomly bundling a large number of fiber strands is arranged.

The luminous flux from the light source image formed on the incident end face of the fiber bundle 31 enters each fiber element constituting the fiber bundle 31. The light beam incident on each fiber strand reaches the emission end of each fiber strand, that is, the emission end of the fiber bundle 31, after repeating total reflection inside. Thus, the predetermined size and NA are set on the exit end face of the fiber bundle 31.
Is formed.

The light beam emitted from the emission end of each fiber strand constituting the fiber bundle 31 is converted into a parallel light beam by the condenser lens 4 and illuminates the irradiated surface 5 in a superimposed manner. Here, the condenser lens 4 is arranged so as to perform so-called Koehler illumination on the irradiated surface 5 using the light source image formed on the exit end face of the fiber bundle 31 as a secondary light source. Thus, with the illumination device of the present embodiment, Koehler illumination of the irradiated surface 5 can be performed with a simple configuration without loss of the light amount and with a uniform light amount.

The fiber bundle 31 is detachably mounted in the optical path between the collector lens 2 and the condenser lens 4. That is, the fiber bundle 31 is configured to be exchangeable with another fiber bundle. In this embodiment, the fiber bundle 3
Two fiber bundles 32 and 33 are provided as fiber bundles that can be exchanged for one. here,
Each of the fiber bundles 31 to 33 is configured by randomly bundling a large number of fiber strands.
/ Di are different from each other. The diameter of each fiber strand constituting the fiber bundles 31 and 32 linearly increases from the entrance end to the exit end, and the diameter of each fiber strand constituting the fiber bundle 33 increases linearly from the entrance end to the exit end. Has decreased.

However, each of the fiber bundles 31 to 33
Are the same as each other.
In each of the fiber bundles 31 to 33, the diameter of the incident end face of the fiber strand is equal to each other. Therefore, the sizes of the incident end faces of the fiber bundles 31 to 33 are equal to each other. The size of the light source image formed by the collector lens 2 is
3 is set slightly smaller than the size of the incident end face. Hereinafter, in order to numerically explain the operation of the present embodiment, the ratio Do / Di of the fiber bundle 31 is set to 1.5.
And the ratio Do / Di of the fiber bundle 32 is 2
And the ratio Do / Di of the fiber bundle 33 is 1
/ 2.

First, in the optical path between the collector lens 2 and the condenser lens 4, a fiber bundle 31 is provided.
Is mounted, the ratio Do / Di is 1.5, so the size of the light source image formed on the exit end face of the fiber bundle 31 is given by referring to the above equations (1) and (2). , 1.5 times the size of the light source image formed on the incident end face of the fiber bundle 31. Further, referring to the above-described equation (1), the NA of the light beam from the light source image formed on the exit end face of the fiber bundle 31 is equal to the NA of the light beam from the light source image formed on the incident end face of the fiber bundle 31. /1.5≒0.67 times.

Next, when the fiber bundle 32 or 33 is mounted instead of the fiber bundle 31 in the optical path between the collector lens 2 and the condenser lens 4, the ratio Do / Di is 2 or 1/2. The size of the light source image formed on the exit end face of the fiber bundle 32 or 33 is twice or half the size of the light source image formed on the incidence end face of the fiber bundle 32 or 33. Fiber bundle 32
Alternatively, the NA of the luminous flux from the light source image formed on the exit end face of the fiber bundle 32 is 1/2 = 0.5 of the NA of the luminous flux from the light source image formed on the incident end face of the fiber bundle 32 or 33.
Double or 2/1 = 2 times.

As described above, the size of the irradiated area is
The numerical aperture NAi of the light beam incident on each of the fiber bundles 31 to 33 and the ratio Do of each of the fiber bundles 31 to 33
/ Di and the focal length f of the condenser lens 4. However, in the present embodiment, the numerical aperture of the light source image formed on the incident end face of each of the fiber bundles 31 to 33, that is, the numerical aperture NAi of the light beam incident on each of the fiber bundles 31 to 33 is constant. The value of the focal length f is also constant. Therefore, the size of the irradiated area is determined by changing the fiber bundles by changing the ratio Do / Di of the fiber bundles 31 to 33.
Will be changed depending on the change of.

As described above, the irradiating NA is determined by the diameter Ii of the light source image formed on the incident end face of each of the fiber bundles 31 to 33, and the diameter of each of the fiber bundles 31 to 33.
Is determined depending on the ratio Do / Di and the focal length f of the condenser lens 4. However, in this embodiment, the size of the light source image formed on the incident end face of each of the fiber bundles 31 to 33, that is, its diameter Ii is constant, and the value of the focal length f of the condenser lens 4 is also constant. Accordingly, similarly to the size of the irradiation area, the irradiation NA is changed depending on the change of the ratio Do / Di of the fiber bundles 31 to 33 by exchanging the fiber bundles.

As described above, in this embodiment, the ratio Do /
Three different fiber bundles 31 to 3 of Di
3, the size of the illuminated area and the illuminated NA can be changed only by appropriately switching the fiber bundle attached to the optical path, in other words, by simply changing the fiber bundle.
Can be easily changed. More specifically, since the size of the irradiated area is proportional to the numerical aperture NAo of the light beam emitted from the fiber bundle, it is inversely proportional to the ratio Do / Di of the fiber bundle. The irradiated NA
Is proportional to the diameter Io of the light source image formed on the exit end face of the fiber bundle, and is therefore proportional to the ratio Do / Di of the fiber bundle.

Also, in this embodiment, a light source box accommodating the light source 1 and the collector lens 2 integrally, an irradiation box accommodating the condenser lens 4, and three fiber bundles interchangeably connecting the two boxes. 31
To 33 can constitute a lighting device. That is, the light source box that houses the light source 1 and the irradiation box can be mechanically separated. Therefore, light source 1
Even if replacement is necessary due to the life of the lamp constituting the lamp, only the relatively small and lightweight light source box is moved to a predetermined work place without moving the entire apparatus, and after replacing the lamp, the original light source box is returned again. You just have to return to the position. That is, in the lighting device of the present embodiment, the workability of lamp replacement is significantly improved.

As described above, in the lighting device of the present embodiment,
With a simple configuration, it is possible not only to illuminate with a uniform light amount without loss of light amount, but also to easily change the size of the irradiation area and the irradiation NA, and to improve the workability of lamp replacement.

Therefore, the illumination device of the present embodiment is used to illuminate the light-receiving surface of a solid-state image sensor such as a CCD with a uniform amount of light, so that the uniformity of output is obtained based on the output of each minute pixel of the CCD. Inspection can be performed with high accuracy. Particularly in the case of a CCD, for example, 1
There are various sizes such as / 5 inch, ４ inch, イ ン チ inch, ／ inch, and 1 inch. In the lighting device of this embodiment, the size of the irradiation area and the irradiation NA can be easily adjusted. Since the size of the illuminated area can be appropriately changed according to the change in the size of the CCD to be inspected, the uniformity of the illumination with no loss of the light quantity can inspect the uniformity of the output accurately and quickly. It can be carried out.

In the above embodiment, the ratio Do / Di
Has three fiber bundles 31 to 33 of 1.5, 2 and 1/2, and an appropriate ratio Do / Di is set according to the size and type of the light receiving surface of the two-dimensional light receiving element to be inspected. The appropriate number of fiber bundles may be provided. In this case, the ratio D of each fiber bundle
o / Di preferably satisfies the following conditional expression (3). 0.5 ≦ Do / Di ≦ 2 (3)

Outside the range defined by the upper limit and the lower limit of the conditional expression (3), it is not preferable because it becomes difficult to manufacture each fiber strand constituting the fiber bundle. Even if the ratio Do / Di of each fiber bundle is defined so as to satisfy the range of the conditional expression (3), for example, 1 /
It is possible to cope with inspection of a wide range of sizes of CCD from 4 inches to 1 inch. The plurality of exchangeable fiber bundles may include a fiber bundle having a ratio Do / Di = 1, that is, a normal fiber bundle formed of a fiber strand having a constant cross section from the input end to the output end.

In the above-described embodiment, the case where the size and NA of the light source image formed by the collector lens 2 based on the light beam from the light source 1 are constant is described. By configuring as a lens, or by switching a plurality of collector lenses having different focal lengths, the size and NA of the light source image can be changed to some extent. However, in this case, it is needless to say that the arrangement of the light source 1 must be changed according to the change in the focal length of the collector lens 2.

[0037]

As described above, the illumination device of the present invention can illuminate the surface to be illuminated with a uniform light amount with a simple structure without loss of the light amount. Further, the size of the irradiation area and the irradiation NA can be easily changed only by appropriately switching the fiber bundle to be used among a plurality of fiber bundles having different ratios Do / Di. Further, only the relatively small and lightweight light source box needs to be moved to a predetermined work place without moving the entire apparatus, and the lamp can be replaced. improves.

Further, in the illumination device of the present invention, the size of the irradiation area and the irradiation NA can be easily changed, so that the size of the irradiation area can be changed according to the change in the size of the CCD to be inspected. The output uniformity can be inspected accurately and promptly with uniform light quantity illumination with no light quantity loss, which is appropriately changed.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a configuration of a lighting device according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing a configuration of a conventional lighting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 21 Light source 2 Collector lens 4, 24 Condenser lens 5, 25 Irradiated surface 22 Collimator lens 23 Fly-eye integrator 31-33 Fiber bundle

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G02B 6/04 G02B 6/04 Z // G01J 1/02 G01J 1/02 M

Claims (4)

[Claims] A light source for supplying an illumination light beam; a light-collecting optical system for condensing a light beam emitted from the light source;
A fiber bundle, which is formed by bundling a large number of fiber strands and has an incident end positioned near the light condensing position of the light condensing optical system, and for guiding a light beam from the exit end of the fiber bundle to an irradiated surface. Wherein each of the plurality of fiber strands constituting the fiber bundle has a cross section whose size changes substantially linearly from an input end to an output end. A lighting device characterized in that it is configured to be exchangeable with a fiber bundle. 2. A plurality of fiber bundles having different ratios between the diameter of the exit end face and the diameter of the entrance end face of each fiber strand are provided, and one fiber bundle selected from the plurality of fiber bundles is used as the light condensing element. The lighting device according to claim 1, wherein the lighting device is detachably mounted in an optical path between an optical system and the condenser optical system. 3. The condition 0.5 ≦ Do / Di ≦ 2, where Di is the diameter of the input end face of each fiber strand constituting the fiber bundle and Do is the diameter of the exit end face of each fiber strand. The lighting device according to claim 1, wherein the following condition is satisfied. 4. An illumination device for illuminating a light receiving surface of a two-dimensional light receiving element to be inspected by using the illumination device according to claim 1; An inspection method, comprising: inspecting output uniformity of the two-dimensional light receiving element based on an output of each light receiving area.