# US 7,744,226 B2 · Projection type image display apparatus

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- Number: US 7,744,226 B2
- Document ID: US7744226B2
- Status: Granted
- Kind: B2
- Application number: 11/384,645
- Filed: 2006-03-20
- Published: 2006-10-05
- Granted: 2010-06-29
- Earliest claimed: 2005-03-31
- Assignees: Konica Minolta Opto, Inc.
- Inventors: Tomokazu Masubuchi; Atsushi Matsuura; Satoshi Onishi; Kohei Watasru; Takashi Ohta
- Web page: https://patentgrep.com/patent/US7744226B2

## CPC

- G03B 21/10: Projectors with built-in or built-on screen
- G03B 21/20: Lamp housings
- G03B 21/28: Reflectors in projection beam {(in illumination beam G03B21/2066)}
- G03B: APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR (optical parts of such apparatus G02B; photosensitive materials or processes for photographic purposes G03C; apparatus for processing exposed photographic materials G03D)

## Abstract

A projection type image display apparatus has: an illumination optical system generating illumination light; a projection optical system projecting an image light onto a screen; a digital micromirror device (DMD) modulating the illumination light so as to form the image light; and a reflection mirror arranged in a position opposite to an optical path of the illumination light entering the DMD. The reflection mirror reflects an off-light reflected by the DMD in an “OFF” state in a direction separated from a projection light reflected by the DMD in an “ON” state.

## Claims

### Claim 1

A projection image display apparatus comprising:
an illumination optical system configured to generate an illumination light;
a projection optical system configured to project an image light onto a screen;
a reflective image forming device configured to modulate the illumination light so as to form the image light, the reflective image forming device having an image forming surface on which a plurality of micromirrors are arranged two-dimensionally, a rotational angle of the micromirrors being set to at least one of first and second angles according to a picture signal input into the reflective image forming device, the micromirrors being configured to reflect the illumination light in a first direction where the light is led to the screen via the projection optical system at the first angle and to reflect the illumination light in a second direction where the light is not led to the screen at the second angle;
a reflection mirror arranged in a position opposite to an optical path of the illumination light to enter the reflective image forming device across an optical path of the image light reflected in the first direction by the micromirrors at the first angle, the reflection mirror configured to reflect the light reflected in the second direction by the micromirrors at the second angle in a direction separated from the image light;
a sealed structure that seals the image forming surface of the reflective image forming device and the reflection mirror; and
a transparent member that comprises a part of the sealed structure, is arranged in a position opposed to the reflection mirror, and is configured to transmit the light reflected by the reflection mirror to an outside of the sealed structure,
wherein:
the illumination optical system is arranged so as to emit the illumination light to the image forming surface of the reflective image forming device from below,
the image forming surface of the reflective image forming device has a rectangular shape having a long side and short side,
a rotational axis of the micromirrors is parallel with the long side of the image forming surface, and the light beams reflected to the first and the second directions by the micromirrors set at the first and the second angles are led upward, and
the projection optical system has a plurality of curved mirrors that lead the image light from the reflective image forming device to the screen in a down-to-up direction.

### Claim 2 (depends on 1)

The projection image display apparatus according to claim 1, wherein the reflection mirror is a concave mirror.

### Claim 3 (depends on 1)

The projection image display apparatus according to claim 1, wherein the reflection mirror is configured to reflect the light reflected in the second direction by the reflective image forming device in a down direction.

### Claim 4 (depends on 1)

The projection image display apparatus according to claim 1, wherein the transparent member is a glass plate.

### Claim 5

A projection image display apparatus comprising:
a projection optical system configured to project an image light onto a screen;
an optical component holding member holding at least one optical component of the projection optical system;
a reflective image forming device configured to separate an illumination light into image light to be projected onto the screen and other unnecessary light according to an input signal thereto;
a reflection element configured to reflect the unnecessary light arranged in a space between the reflective image forming device and the projection optical system; and
a first transparent member;
wherein the reflective image forming device is held by the optical component holding member via an image forming device holder;
wherein the optical component holding member has a tube portion having a first opening, the image forming device holder is held to the first opening, and the optical component holding member has a second opening for leading the unnecessary light reflected by the reflection element to the outside of the optical component holding member;
wherein the first transparent member covers the second opening; and
wherein the reflection element is configured to reflect the unnecessary light not towards the projection optical system but towards an optical path of the illumination light.

### Claim 6 (depends on 5)

The projection image display apparatus according to claim 5, wherein the reflection element is held by the optical component holding member.

### Claim 7 (depends on 5)

The projection image display apparatus according to claim 5, wherein the projection optical system has a plurality of curved mirrors, and the apparatus is configured so that a center principal ray of the image light, a center principal ray of the unnecessary light, and a center principal ray of the illumination light entering the reflective image forming device are on the same plane.

### Claim 8

A projection image display apparatus comprising:
a projection optical system configured to project an image light onto a screen;
an optical component holding member holding at least one optical component of the projection optical system;
a reflective image forming device configured to separate an illumination light into image light to be projected onto the screen and other unnecessary light according to an input signal thereto;
a reflection element configured to reflect the unnecessary light arranged in a space between the reflective image forming device and the projection optical system;
a first transparent member; and
a second transparent member arranged on an optical path of the image light between the reflective image forming device and the projection optical system and being held by the optical component holding member;
wherein the reflective image forming device is held by the optical component holding member via an image forming device holder;
wherein the optical component holding member has a tube portion having a first opening, the image forming device holder is held to the first opening, and the optical component holding member has a second opening for leading the unnecessary light reflected by the reflection element to the outside of the optical component holding member;
wherein the first transparent member covers the second opening; and
wherein the optical component holding member, the reflective image forming device, the image forming device holder, the first transparent member, and the second transparent member surround a space between the reflective image forming device and the projection optical system.

### Claim 9 (depends on 5)

The projection image display apparatus according to claim 5, wherein the reflective image forming device is a digital micromirror device.

### Claim 10 (depends on 4)

The projection image display apparatus according to claim 4, wherein the reflection mirror is a concave mirror.

### Claim 11 (depends on 7)

The projection image display apparatus according to claim 7, further comprising:
a second transparent member arranged on an optical path of the image light between the reflective image forming device and the projection optical system and being held by the optical component holding member,
wherein the optical component holding member, the reflective image forming device, the image forming device holder, the first transparent member, and the second transparent member surround a space between the reflective image forming device and the projection optical system.