JP3434015B2 - Optical homogenizer - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an optical homogenizer. The optical homogenizer of the present invention can be used as a light source for exposure of photolithography and a light source for liquid crystal of a liquid crystal projector.

[0002]

2. Description of the Related Art In the manufacture of a semiconductor IC, when "exposing an IC circuit pattern on a wafer with a mask" or when "illuminating a liquid crystal and projecting an image on the liquid crystal onto a screen" in a liquid crystal projector. In such a case, it is necessary to illuminate a certain area with uniform intensity of light.

In general, a light beam from the light source side is rare when the light intensity on the cross section of the light beam is uniform, and usually has some intensity distribution. Therefore, in order to irradiate a certain area area with light having a uniform intensity distribution, it is necessary to make the intensity distribution of the light flux from the light source side uniform (homogenize),
An optical element that does this is called an "optical homogenizer".

Various types of optical homogenizers have been known so far. Among them, the one considered to be practical is disclosed in Japanese Patent Laid-Open No. 3-16114.
“A large number of equivalent small-diameter lenses (element lenses) are densely combined with each other, and they are made immobile by pressing force to form a lens group (fly-eye lens), and the light flux from the light source side is made into a parallel light flux and enters this lens group Then, the light flux condensed by each small-diameter lens is made to enter the condenser lens while diverging, and the condenser lens is configured to collimate the light flux from each small-diameter lens and irradiate the desired area region. It will be something.

In this case, if there is an element lens with low accuracy, the element lenses cannot be densely combined with each other. Therefore, it is necessary to form the element lens with high accuracy as required for the prism. At the time of formation, while combining the element lens groups, the element lenses with low accuracy are replaced by the element lenses with high accuracy, and the combination work is complicated, and it is difficult to reduce the manufacturing cost of the lens groups. There is a problem.

[0006]

The present invention has been made in view of the above circumstances, and an object thereof is to provide a novel optical homogenizer which can be manufactured easily and inexpensively.

[0007]

As shown in FIG. 1, an optical homogenizer according to claim 1 has conical surfaces C1, C2 ,. ． Ci ,. ． Cn
They are closely concentrically arranged (FIG. 1A), and the conical surfaces Ci are formed so that the inclination of each conical surface Ci gradually increases from the central portion toward the outer peripheral portion to form a conical surface group (FIGS. 1B and 1C). ), It has a function of condensing a light beam incident on this conical surface group in a predetermined region on the light beam optical axis.

"Plate-shaped transparent body" in which "conical surface group" is formed
May be "parallel plate-like" as in the example shown in FIG. 1 (b), or as in the example shown in FIG. 1 (c), the wall thickness is "from the central conical surface C1 portion to the peripheral portion." It gets thinner as you go. "
Alternatively, the wall thickness may be such that “the thickness gradually increases from the central portion to the peripheral portion”.

Examples of the material of the plate-shaped transparent body include not only ordinary optical glass, plastic, etc., but also materials that transmit ultraviolet light, such as fused quartz, synthetic quartz, SiO ₂ , and Al _2.
A single crystal of fluoride, chloride, bromide, iodide or oxide represented by O ₃ or CaF ₂ can be used (claim 2).

The optical unit according to claim 1 or 2
The homogenizer can be configured as another optical homogenizer in combination with a magnifying optical system that magnifies the image of the light flux condensing position by these (claim 3).

In the optical homogenizer according to claim 1, 2 or 3, the "conical surface group" is that "the photoresist layer formed on the surface of the plate-shaped transparent body is patterned into a shape corresponding to the conical surface group. , A patterned shape is engraved on a plate-shaped transparent body by anisotropic etching. (Claim 4), or alternatively, the conical surface group is formed into a shape corresponding to the conical surface group. A curable resin is sandwiched between a mold having a shape and the surface of a plate-shaped transparent body, and the shape formed on the surface of the curable resin by curing with light and / or heat is engraved on a transparent substrate by etching. Can be formed (claim 5).

When plastic is used as the material, an optical homogenizer having a conical surface group can be obtained by molding or injection molding.

The "predetermined area on the optical axis of the light beam" may be an "area area" orthogonal to the optical axis of the light beam at a predetermined position, or may have a certain width in the optical axis direction. region"
Sometimes.

Further, the light beam (light beam to be homogenized) which is incident on the optical homogenizer according to the first to fifth aspects may be a parallel light beam, divergent or convergent. An appropriate optical homogenizer can be designed according to the form of the incident light flux.

The arrangement intervals (radial intervals) of the conical surfaces in the conical surface group may be uniform or may be different according to the distance from the central portion. However, the arrangement interval (the width of the ring-shaped region when the conical surface is projected on the surface orthogonal to the central axis) is preferably 500 μm to several mm.

The optical homogenizer according to the present invention is designed so that the luminous flux from a fluorescent lamp, a halogen lamp or the like, or L
It can be used for homogenizing a wide variety of light fluxes such as light fluxes from D and LED, and further light fluxes from various lasers such as excimer lasers.

[0017]

As described above, the optical homogenizer of the present invention uses the "conical surface group". Since the inclination of each conical surface in the conical surface group is determined so as to gradually increase from the central portion toward the outer peripheral portion, the light flux refracted by the conical surface has the conical surface at the outer peripheral portion of the conical surface group. The closer it is, the larger the deflection toward the center portion side becomes, and the deflection angle becomes larger as the conical surface moves away from the center portion of the conical surface group.

Therefore, by combining the light beams deflected by the respective conical surfaces, a region where the light intensity is uniform can be realized at the converging portion.

As the material of the plate-shaped transparent body, SiO ₂ etc., as in the optical homogenizer according to claim ₂ ,
When a "material that transmits ultraviolet light" is used, a homogenizing effect can be obtained even for an ultraviolet light flux.

[0020]

EXAMPLES Examples will be described below. FIG. 2 shows claim 1.
It is a figure for demonstrating one Example of the described "optical homogenizer."

In FIG. 2, reference numeral 10 indicates an optical homogenizer. The optical homogenizer 10 has one side of a transparent parallel plate, which is a "plate-shaped transparent body".
The conical surfaces C1, C2 ,. ． , Ci ,. ． ． Are formed into concentric circles to form a concentric circle group.

The inclination of the conical surface Ci is defined by "90 degrees-cone angle", and gradually increases from the central part to the outer peripheral part of the concentric circular conical surface group. In other words, each conical surface C
The “cone angle” of i gradually decreases from the central portion toward the outer peripheral portion.

As shown in FIG. 2, the incident light beam LF to be homogenized is orthogonally incident on the optical homogenizer 10 as a "parallel light beam" over the entire surface of the conical surface group. The incident light flux portion is defined as a light flux f _i . The light beam f _i is a hollow cylindrical light beam portion whose central axis is the light beam optical axis.

The light beam f _i is deflected by the conical surface Ci as shown in the figure, and the diameter is defined as "the width of the ring-shaped region when the conical surface Ci is projected on the surface orthogonal to the central axis" on the surface S. The light is focused on the circular area S1.

From optical homogenizer 10 to surface S
Is L and the radius of the conical surface Ci is r _i . If the deflection angle of the light beam f _i deflected by the conical surface Ci is θ _i , the deflection angle θ _i is a function of the inclination angle α _i (not shown) of the conical surface Ci and the refractive index of the plate-shaped transparent body. And the tilt angle: α
It changes in proportion to _i . That is, when the tilt angle: α _i is determined, the deflection angle: θ _i is determined.
_i (α _i ) ”can be written. If the parallel light flux is made incident from the flat surface side of the optical homogenizer, the refraction angle by each conical surface becomes the deflection angle as it is.

In order for all the light beams f _i incident on the arbitrary conical surface Ci to merge in the area S1 on the surface S, the deflection angle: θ
_{i (α i)} is the relationship: it is sufficient to satisfy the _{"θ i (α i) = tan} ~ 1 (r i / L) ". If the inclination angle α _i of the conical surface Ci (i = 1, 2, ...) Is set so that this relationship is satisfied,
Parallel light flux L incident on the optical homogenizer 10
All F will merge on the area S1 on the surface S.

Now, the light intensity distribution in the incident light beam LF is
Using two-dimensional polar coordinates: r, φ, F (r, φ), and the width of the conical surface Ci is Δi. It is assumed that F (r, φ) is a gradual change in the direction of r in the range of the width of the conical surface: Δi (which is a general situation) so that it can be regarded as uniform (a general situation). The intensity distribution of f _i is F
(R _i , φ).

The intensity distribution of the light beam f _i is converged in the area S1 (light beam confluence portion) on the surface S, so that the change with respect to φ is completely integrated, and only the dependence on the radius r is obtained. However, as described above, since the light intensity can be regarded as uniform within the range of the width Δi of the conical surface, the light intensity of the light flux f _i condensed in the area region S1 is uniform in the area region S1. Becomes

Therefore, if the light beams deflected by the respective conical surfaces Ci are merged in the area S1, the light intensity becomes ΣF (r
_i ) (the sum is for i, and for all conical surfaces) and is uniform.

When the converging position of the light beam f _i is shifted little by little in the light beam optical axis direction for each conical surface, the state where the light intensity distribution is substantially uniform in the “finite region in the optical axis direction” ( Within the above region, the light intensity is uniform on any surface orthogonal to the optical axis of the light flux). Even if this is not done, the light intensity distribution is substantially uniform in some areas before and after the area area S1.

As the width of each conical surface in the conical surface group becomes smaller, the "uniformity of light intensity" becomes higher, and the light intensity becomes [∫∫
F (r, φ) rdrdφ].

If the width of the conical surface is increased, the light collecting portion (area area S1) is increased.
The effect of homogenization in the radial direction of the conical surface group is reduced, and the uniformity of light intensity is reduced.

Therefore, the more the uniform light intensity is required, the smaller the size of the light converging portion becomes. In such a case, the magnifying optical system 31 is placed behind the optical homogenizer 10 as shown in FIG.
The image of the area S1 which is the light flux converging position by the homogenizer 10 may be enlarged and imaged on a desired illumination unit (claim 3).

The case where the parallel light flux is used as the incident light flux has been described above, but the incident light flux is "divergent" or "convergent".
But you can design an optical homogenizer with the required performance.

The embodiments of the present invention described in claims 4 and 5 will be described below.

FIG. 3 is a diagram for explaining a characteristic part of one embodiment of the optical homogenizer according to the fourth aspect.

In FIG. 3A, a layer of positive photoresist 3 is formed on the surface of the plate-shaped transparent body indicated by reference numeral 1. The mask 5 is brought into close contact with the layer of the photoresist 3, and uniform light is irradiated through the mask 5 to expose the layer of the photoresist 3.

The mask 5 is formed so as to have a light transmittance distribution as shown in FIG. 3B in the radial direction (left and right direction of the figure) around the central axis shown by the chain line.

After exposure, the photo-irradiated photoresist 3 is removed and post-cured is the state shown in FIG. 3 (c). The surface of the photoresist 3 is in a state where concavities and convexities having a sawtooth cross-sectional shape are concentrically formed.

From this state, anisotropic etching is performed to engrave the surface shape of the photoresist 3 on the surface of the plate-shaped transparent body 1 so that a conical surface group can be formed as the surface shape of the plate-shaped transparent body 1 ( FIG. 3D).

FIG. 4 is a diagram for explaining the characteristic portion of one embodiment of the optical homogenizer according to the fifth aspect.

In FIG. 4A, the plate-shaped transparent body indicated by reference numeral 2 is made of SiO ₂ . The mold shown by reference numeral 4 has a shape corresponding to a desired conical surface group.

As shown in FIG. 4A, the ultraviolet curable resin 6 which is a curable resin is formed by the surface of the transparent plate 2 and the mold 4.
And irradiate uniform ultraviolet light through the plate-shaped transparent body 2,
The ultraviolet curable resin 6 is cured.

After curing, the mold 4 is removed to obtain a state in which the cured ultraviolet curable resin 6 is fixed to the surface of the plate-shaped transparent body 2 as shown in FIG. 4 (b). A desired shape of the conical surface group is transferred from the mold 4 to the surface of the ultraviolet curable resin 6.

From this state, anisotropic etching is carried out to engrave the surface shape of the ultraviolet curable resin 6 on the surface of the plate-shaped transparent body 2, so that the conical surface group can be formed as the surface shape of the plate-shaped transparent body 2. (FIG.4 (c)).

In the embodiments of FIGS. 3 and 4, if the anisotropic etching selection ratio is 1, the shapes formed on the surfaces of the photoresist 3 and the ultraviolet curable resin 6 are jointly defined. It can be engraved as the surface shape of a plate-shaped transparent body, but by changing the selection ratio, the ratio of the height of the engraved shape to the height of the surface shape of photoresist or UV curable resin
It can be adjusted to the desired value.

[0047]

As described above, according to the present invention, a novel optical homogenizer can be provided (claims 1 to 5). Since the optical homogenizer of the present invention has the configuration in which the conical surface group is formed on the plate-shaped transparent body as described above, it can be easily and inexpensively manufactured.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an optical homogenizer of the present invention.

FIG. 2 is a diagram for explaining an embodiment of the optical homogenizer according to claims 1 and 3.

FIG. 3 is a view for explaining an embodiment of the optical homogenizer according to claim 4;

FIG. 4 is a view for explaining a characteristic part of an embodiment of the optical homogenizer according to claim 5;

[Explanation of symbols]

Ci conical surface S The surface where the light beams deflected by the conical surface join

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/027 G03F 7/20 521 G02B 3/08

Claims (5)

(57) [Claims] 1. A conical surface is formed on one surface of a plate-shaped transparent body so that conical surfaces are concentrically closely contacted with each other and the inclination of each conical surface gradually increases from a central portion toward an outer peripheral portion. The optical beam has a function of condensing the light beam incident on the conical surface group in a predetermined area on the light beam optical axis.
Homogenizer. 2. The optical homogenizer according to claim 1, wherein the plate-shaped transparent body is a plate made of a material that transmits ultraviolet light. 3. An optical homogenizer according to claim 1 or 2, and a magnifying optical system for magnifying an image of a light beam focusing position by the optical homogenizer.
Homogenizer. 4. The optical homogenizer according to claim 1, 2 or 3, wherein the conical surface group is formed by patterning a shape corresponding to the conical surface group on a photoresist layer formed on the surface of the plate-shaped transparent body, An optical homogenizer, which is formed by engraving a patterned shape on a plate-shaped transparent body by anisotropic etching. 5. The optical homogenizer according to claim 1, 2 or 3, wherein the conical surface group includes a mold having a mold shape corresponding to the conical surface group and the surface of the plate-shaped transparent body to sandwich the curable resin. Then, light and /
Alternatively, the optical homogenizer is characterized by being formed by engraving a shape formed on the surface of the curable resin by curing with heat onto a transparent substrate by etching.