# US 9,039,196 B2 · Image displaying apparatus having plane mirror at conjugate to image displaying element

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- Number: US 9,039,196 B2
- Document ID: US9039196B2
- Status: Granted
- Kind: B2
- Application number: 13/664,830
- Filed: 2012-10-31
- Published: 2013-05-02
- Granted: 2015-05-26
- Earliest claimed: 2011-10-31
- Assignees: Ricoh Company, Ltd.
- Applicants: Makoto Hirakawa; Hibiki Tatsuno; Takanobu Osaka; Yasuyuki Shibayama; Kiichiro Nishina
- Inventors: Makoto Hirakawa; Hibiki Tatsuno; Takanobu Osaka; Yasuyuki Shibayama; Kiichiro Nishina
- Web page: https://patentgrep.com/patent/US9039196B2

## CPC

- G03B 21/28: Reflectors in projection beam {(in illumination beam G03B21/2066)}
- G02B 17/0816: {off-axis or unobscured systems in which not all of the mirrors share a common axis of rotational symmetry, e.g. at least one of the mirrors is warped, tilted or decentered with respect to the other elements}
- G03B 21/008: {using micromirror devices}
- G03B 21/2066: {Reflectors in illumination beam (in projection beam G03B21/28)}
- H04N 9/3152: {for shaping the light beam (beam shaping per se G02B27/09)}
- G03B 21/10: Projectors with built-in or built-on screen
- 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)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

An image displaying apparatus including a light source, an image displaying element configured to control exiting of incident light to display an image, an illumination optical system configured to illuminate the image displaying element with light exiting from the light source, and a projection optical system configured to project an image displayed on a display surface of the image displaying element, to provide an enlarged display. The projection optical system includes a lens optical system, a first mirror configured to reflect light transmitted through the lens optical system, and a second mirror configured to reflect light reflected from the first mirror toward the surface to be projected onto, and one of the mirrors is arranged at a position conjugate to the image displaying element, and wherein an optical surface of the one mirror is arranged to face vertically downward.

## Claims

### Claim 1

An image displaying apparatus comprising:
a light source;
an image displaying element configured to control exiting of incident light to display an image;
an illumination optical system configured to illuminate the image displaying element with light exiting from the light source; and
a projection optical system configured to project an image displayed on a display surface of the image displaying element onto a surface to be projected onto, to provide an enlarged display,
wherein the projection optical system includes a leas optical system, a first mirror configured to reflect light transmitted through the lens optical system, and a second mirror configured to reflect light reflected from the first mirror toward the surface to be projected onto,
wherein one of the first mirror and the second mirror is arranged so that at least a part of an optical surface of said one of the first mirror and the second mirror is present at a position that is conjugate to the image displaying element,
wherein the optical surface of the one mirror is arranged to face a vertically downward direction, and wherein light condensation of the light reflected from the second mirror towards the surface to be projected onto is at a position proximate to a contamination barrier and the first mirror.

### Claim 2 (depends on 1)

The image displaying apparatus as claimed in claim 1, wherein the display surface of the image displaying element and the surface to be projected onto are generally mutually orthogonal.

### Claim 3 (depends on 1)

The image displaying apparatus as claimed in claim 1, wherein a lens surface of a lens closest to the first mirror among plural lenses constituting the lens optical system is a convex surface.

### Claim 4 (depends on 1)

The image displaying apparatus as claimed in claim 1, wherein the one mirror arranged at a position conjugate to the image displaying element is a plane mirror.

### Claim 5 (depends on 1)

The image displaying apparatus as claimed in claim 1, wherein the one mirror arranged at a position conjugate to the image displaying element is the first mirror.

### Claim 6 (depends on 1)

The image displaying apparatus as claimed in claim 1, wherein a non-telecentric optical system is provided at a position of an entrance pupil of the lens optical system.

### Claim 7 (depends on 1)

The image displaying apparatus as claimed in claim 1, wherein the projection optical system configured to project the image and provide the enlarged display has a throw ration of about 0.3 or less.

### Claim 8 (depends on 1)

The image displaying apparatus as claimed in claim 1, wherein the contamination barrier is configured to transmit light reflected from the second mirror toward the surface to be projected onto, the contamination barrier being disposed adjacent to an end of the first mirror.