JPH03211506A - Optical device - Google Patents

Abstract

PURPOSE:To obtain collimated beams of light with high accuracy by making the exit light from tapered fibers on a condenser lens after the exit light is converted to a spot light source. CONSTITUTION:This device has a light source 101 positioned at the 1st focus of an elliptical reflecting mirror 102, the elliptical reflecting mirror 102 which condenses the light from the light source 101 at a 2nd focus and a tapered fiber bundle 103 which is positioned behind this mirror and condenses the reflected light from the elliptical reflecting mirror 102. Further, the device is constituted of the condenser lens 104 which is disposed by aligning its focus to the end face on the small aperture diameter side of the fiber bundle or the inner side thereof or the position on the outer side where the condensing area is smallest. The condenser lens 104 collimates the light emitted from the tapered fiber bundle 103 to the collimated beams of light. The light source spreading at a relatively wide angle is converted to the spot light source in such a manner and the light from the spot light source is made incident on the condenser lens, by which the collimated beams of light of the high accuracy are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an optical device that can convert a light source that spreads over a relatively wide angle into a point light source.

<Prior art> ■Optical devices used as light sources for microfabrication and local processing in the production of semiconductor devices such as C and as light sources for projection-type image display devices require highly parallel and uniform light rays. Various optical systems have been devised for this purpose.

In FIG. 4(a), a parabolic reflecting mirror 2 is used to obtain parallel light rays by reflecting light from a light source l located at its focal point by the parabolic reflecting mirror y12.

In addition, FIG. 4(b) uses an elliptical reflecting mirror 3, and by placing the light source 1 at its first focal point, the reflected light from the light tA1 is positioned behind the second focal point, and the focal point is set at the ellipse. Parallel light rays are obtained by a condenser lens arranged to coincide with the second focal point of the reflecting mirror 3.

In either case, the light rays are hollow due to the shadow of the electrode of the light source 1, so a method is used in which an integrator that makes the light uniform is inserted in the optical path to prevent the light rays from falling through.

<Problems to be Solved by the Invention> In these methods, there is a limit to the parallelism of the light beam that can actually be obtained due to the arc length of the lamp used as the light source 1 and the accuracy of the reflecting mirror 2 or 3.

In an optical device using a parabolic reflecting mirror 2 as shown in FIG. 4(a), as the arc length of the light source 1 increases, the angle α in the figure increases and the parallelism decreases. Also, Figure 4 (b
) In an optical device using an elliptical reflector 3 as shown in
The light beam condensed at the second focal point should be condensed at one point if the light source l is a complete point light source, but in reality, the light beam condensed at the elliptical reflector 3
Due to the accuracy of the light source 1 and the arc length of the light source 1, the light will not be completely focused on the second focal point, and even if the elliptical reflector 3 has high precision, the size will be proportional to the arc length of the light source 1, and the larger this becomes, the more The parallelism of the light rays decreases after passing through the condenser lens.

For example, if such a light beam with low parallelism is used to expose an IC pattern, the image on the wafer will become blurred, making it difficult to perform precise exposure.

In addition, in the case of a projection type display device, out-of-focus occurs on the screen.

<Means for Solving the Problems> As a result of intensive studies to solve the above-mentioned problems, the present inventors have developed a tapered end fiber (hereinafter referred to as a tapered fiber, for example, Kyoritsu Shuppan Co., Ltd.), which has a core area different on both end faces. A tapered fiber bundle made by bundling multiple fibers (see pages 18 and 190 of "Optical Fiber" published by the company) is installed between the light source and the focal point of the condenser lens, and the light from the light source reflected by the reflecting mirror is transferred to the tapered fiber. The light is made to enter the large-diameter side of the bundle, and is output as a point light source from the end face on the small-diameter side of the tapered fiber bundle, which is positioned at the focal length of the condenser lens. Based on the idea that if the emitted light is made incident on the condenser lens, highly accurate parallel light rays can be obtained, the present invention was completed.

That is, the present invention provides a tapered fiber bundle in which 2,500 to 250,000 tapered fibers, preferably 40,000 tapered fibers are bundled, and the diameter of the end face on the large diameter side is 5 mm to 5 mm.
0 mm, preferably 30 mm, and the diameter of the end face on the small diameter side is 1
mm to 10mm preferably 3mm, total length 10m
m-100 mm, preferably 50 mm, and a highly accurate parallel light beam was obtained by converting the emitted light from the tapered fiber into a point light source and making it incident on a condenser lens.

Note that the tapered fiber may be conical or pyramid-shaped.

<Operation> When light enters the tapered fiber from the large-diameter end face and exits from the other end, the small-diameter end face, light can be focused in accordance with the area ratio of the input end face and the output end face.

On the other hand, if we consider a tapered fiber with a conical shape such that one end has a diameter a and the other end has a diameter b (a>b), it has an angle θ1 with respect to the end face with a diameter a as shown in Figure 5. When the incident light ray enters, the exit angle from the end face with diameter b is θ,
Then n+XaX5! nθ, = n, xb, Xs i nθ.

... (1) There is a relationship. Here, n I and n t are the refractive indices of the external substance at the input end and output end of the tapered fiber. (
In equation 1), if n=n, the larger the ratio of a and b, the larger θ becomes.

Therefore, when using a tapered fiber for the purpose of condensing light, if the angle of the emitted light exceeds 90°, the incident light will be totally reflected at the smaller end face and will return in the opposite direction without being emitted. The critical angle of l+ sin θ+ < (n 2 X b ) / (n +
X a )(2) It is necessary to satisfy the following condition.

Furthermore, since the TENO KUICHI FI/S-' itself functions as an integrator, it becomes possible to obtain a uniform light beam, which has been a problem in the past due to the shadow of the light source's electrode.

<Example 1> Examples of the present invention will be described below with reference to the drawings.

FIG. 1 shows an optical device according to one embodiment of the invention.

As shown in FIG. 1, the optical device according to this embodiment includes a light source 101 located at a first focus of an elliptical reflector 102, and an ellipse reflector 102 that focuses light from the light source 101 on a second focus. , located behind the elliptical reflector 102 and for condensing the reflected light from the ellipse reflector 102.
-7 Finoy bundle 103 and Taper Finoy s1 bundle 10
3, or a condenser lens 104 disposed with its focal point aligned at a position with the smallest condensing area on the inside or outside of the end surface on the small diameter side. The condenser lens 104 converts the light emitted from the tapered fiber bundle 103 into parallel light beams.

In this embodiment, the light source 101 is arc g 7
A tapered fiber bundle is made by bundling 40,000 tapered fibers, using a metal halide lamp of mm, and the diameter of the large-diameter end face a is 30 mm, the diameter of the small-diameter end face a is 3 mm, and the length is 50 mm. was used. The condenser lens 104 used had a focal length of 200 mm.

In the optical device described above, the maximum incident angle θ to the large-diameter end face of each tapered fiber of the tapered fiber bundle 103
If 1=3°, then from equation (1), the output light will reach the maximum output I.
A light source with an angle θ=31.5° and a diameter of 3 mm, which is very close to a point light source, was created, and as a result of RIing the emitted light from the point light source into the rear condenser lens 104, a light ray that was very close to parallel rays was obtained.

In this embodiment, a xenon lamp or a halogen lamp is used in addition to a metal halide lamp as the light 4101, and a parabolic reflector in addition to an elliptical reflector is used as the reflector +02.

<Example 2> FIG. 2 shows an example using this optical device.

FIG. 2 is a schematic diagram of a projection type image display device using the present invention.

In the figure, 201 is a liquid crystal panel, and the pixel pitch is 190 vertically.
μm x width 161μm, opening is length 88μm x width 10
It is of an active matrix drive type with a diameter of 4 μm and an aperture ratio of 30%. Reference numeral 202 denotes an optical device similar to that in Example 1, and is given the same reference numeral and description thereof will be omitted. 203 is a field lens, and 204 is a projection lens, both of which have a focal length of 20 Qmm. 205 is a projection screen.

In the above-mentioned projection type image display device, when the parallel light beam obtained from the optical device 202 is incident on the compound eye lens, the size of the condensed spot is as shown in Fig. 6, assuming that the degree of inclination of the incident light is ±θ. As shown, it has a size of 2fXtanθ, and this is a picture element.

If it is larger than the aperture, the effect of the compound eye lens 110 cannot be fully exhibited, but by applying the present invention and making parallel light beams with high accuracy enter the compound eye lens 110, the effect can be fully exhibited, and the screen Usually 40 on
Is it 200x in inches or 400x or more?
I was able to obtain an image that was more than twice as bright.

In this embodiment, a compound lens was used as the microlens, but the present invention can also be applied to a lenticular lens.

<Example 3> FIGS. 3(a) and 3(b) show the light irradiation device 2 in Example 1.
A schematic diagram of a proximity type exposure apparatus and a reduction projection type exposure apparatus is shown as an example using 02.

Even in the existing exposure apparatus, precise exposure could be performed by using a highly parallel beam of light that passed through the photomask 301 or 303 and the wafer 302.

In particular, in the reduction projection type exposure apparatus, there was no change in the projection magnification on the wafer 304 due to positional deviation of the photomask 303 or the wafer 304 in the optical axis direction, which has been a problem in the past.

In addition, in the reduction projection exposure in this example, telecentric optical systems were used on both the photomask side and the wafer side, but by using a telecentric system on either the photomask side or the wafer side, The magnification error can also be corrected by intentionally moving the wafer in the optical axis direction.

<Effects of the Invention> As described above, by applying the present invention, a light source that spreads over a relatively wide angle can be converted into a point light source.

Further, by making the light from the point light source obtained in the present invention incident on a condenser lens, highly accurate parallel light rays can be obtained.

FIG. 1 is a schematic diagram of an apparatus according to an embodiment of the present invention.

Fig. 2 is a block diagram when the present invention is applied to a projection type image device, Figs. 3 (a) and (b) are block diagrams when the present invention is applied to an exposure apparatus, and Figs. 4 (a) and (b) is a diagram showing a typical example of the prior art, Figure 5 is a diagram showing the optical path passing through the tapered fiber, and Figure 6 is a diagram showing the size of the condensed spot that changes depending on the parallelism of the incident light. It is.

lOl...Light source, 102...Elliptical reflector, 103.
...Tapered fiber L104...Condenser lens.

Claims (1)

[Claims] 1. An optical device in which the large-diameter side of a tapered optical fiber bundle consisting of a plurality of tapered optical fibers is an input end and the small-diameter side is an output end, and the light emitted from the output end is converted into a point light source. optical equipment.