Fly eye lens

Details Fly eye lens Fly eye lens

2000-08-01

2001-11-06

Schwartz, Jordan M. (Department: 2873)

Optical: systems and elements

Single channel simultaneously to or from plural channels

By surface composed of lenticular elements

C359S741000, C359S820000

Reexamination Certificate

active

06313949

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plastic fly eye lens used in an optical system such as a liquid crystal projector.
2. Related Background Art
As conventional fly eye lenses, fly eye lenses B and C, employed in a pair in a housing A of an optical system such as a liquid crystal projector are known, as shown in FIG.
5
. These fly eye lenses B and C respectively have pluralities of cells E
B
and E
C
, and light from a light source can uniformly irradiate a target object with the optical function of the cells E
B
and E
C
.
The fly eye lenses B and C are fitted in the housing A, fixed with retainers H extending through the housing A with their outer edge portions abutting against projections F projecting on the inner surface of the housing A, and are positioned such that their lens surfaces perpendicularly intersect an optical axis Z of this optical system. In this state, when a lamp D emits light, this light is focused in units of cells E
B
of the fly eye lens B. The focused light is then received and enlarged in units of cells E
C
of the fly eye lens C that correspond to the cells E
B
in one-to-one correspondence. The light thus irradiates a target optical system G as uniform light.
In this conventional optical system, the interior of the optical system is heated to a high temperature of 150° C. or more by irradiation with the lamp D. The housing A and fly eye lenses B and C thus thermally expand, so desired optical performance cannot be obtained.
For example, when the coefficient of thermal expansion of the housing A is larger than that of the fly eye lenses B and C, the housing A becomes larger with respect to the fly eye lenses B and C. Then, a gap is formed between the inner wall of the housing A and the outer edges of the fly eye lenses B and C, and the centers of the fly eye lenses B and C are shifted from the optical axis Z. In this case, the centers of the two fly eye lenses B and C are also shifted from each other, and the optical performance may undesirably, largely degrade.
When the coefficient of thermal expansion of the housing A is smaller than that of the fly eye lenses B and C, the fly eye lenses B and C become larger with respect to the housing A. Thus, the fly eye lenses B and C are to expand by pushing the inner wall of the housing A. Therefore, the fly eye lenses B and C may be distorted, leading to degrading optical performance.
As a countermeasure for this inconvenience, a glass plate I coated with an anti-reflecting coating may be interposed as a heat-insulating member between the lamp D and fly eye lens B, as shown in FIG.
6
. However, as heat of the lamp D is conducted through the housing A and the like, thermal expansion of the housing A and fly eye lenses B and C cannot be prevented effectively.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems, and has as its object to provide a fly eye lens which can obtain desired optical performance even if it thermally expands.
More specifically, according to the present invention, there is provided a fly eye lens with a plurality of cells at an optical functional portion thereof, characterized by having first, second, and third positioning portions on an outer edge thereof, wherein the first and second positioning portions are formed on one of regions of a plane normal to the optical axis of the lens, and divided by a first reference line extending through a center of thermal expansion located on the plane of the lens, the first and second positioning portions having end portions located on the first reference line, and the third positioning portion has an end portion located on a second reference line crossing the first reference line and extending through the center of thermal expansion located on the plane of the lens.
According to the present invention, the fly eye lens is positioned with respect to an optical system by using the end portions of the first, second, and third positioning portions. Even when the fly eye lens thermally expands, the end portions of its first and second positioning portions can be positioned on the first reference line and the end portion of its third positioning portion can be positioned on the second reference line. Therefore, when the fly eye lens thermally expands, the center of its thermal expansion can be prevented from moving with respect to the optical system, and degradation in optical function resulted from movement of the fly eye lens can be prevented.
The fly eye lens according to the present invention can be characterized in that the first, second, and third positioning portions described above are projections projecting from the outer edge of the fly eye lens, or recesses formed by recessing the outer edge of the fly eye lens. When the respective positioning portions are formed in this manner, in addition to the function and effect described above, a gap through which heat in the optical system is discharged can be ensured easily.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.


REFERENCES:
patent: 4402572 (1983-09-01), Tsunoda et al.
patent: 4884869 (1989-12-01), Uemura
patent: 4-265919-A (1992-09-01), None

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