Projection display apparatus

• US 20080252863A1
• Filed: 11/19/2007
• Published: 10/16/2008
• Est. Priority Date: 04/16/2007
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Kojima, Kuniko, Takeuchi, Hayato
• Granted Patent: US 7,950,808 B2
• Time in Patent Office: Days
• US Class Current: 353/99
• CPC Class Codes: G03B 21/28 Reflectors in projection beam in illumination beam G03B21/2066

Abstract

An illuminating optical system propagates a coherent light flux from at least one light source into a predetermined optical path to guide the light flux to a screen. A light bulb forms an image to be displayed on the screen on an illumination area illuminated with the light flux that is guided by the illuminating optical system. A projecting optical unit projects the image that is formed on the illumination area onto the screen in a magnifying manner. The illuminating optical system includes a diffusing unit that diffuses the light flux from the light source near a focusing position of the illuminating optical system.

Claims

1. A projection display apparatus that performs an image display by projecting an image onto a screen, the projection display apparatus comprising:

at least one light source that emits a coherent light flux;

an illuminating optical system that propagates the light flux from the light source into a predetermined optical path to guide the light flux to the screen;

a light bulb that forms an image to be displayed on the screen on an illumination area illuminated with the light flux that is guided by the illuminating optical system; and

a projecting optical unit that projects the image that is formed on the illumination area onto the screen in a magnifying manner, wherein

the illuminating optical system includes a diffusing unit that diffuses the light flux from the light source near a focusing position of the illuminating optical system.

2. The projection display apparatus according to claim 1, wherein

the illuminating optical unit further includes

a light-intensity equalizing element that equalizes an intensity distribution of the light flux from the light source, and

a relay lens group that leads the light flux from the light-intensity equalizing element to the light bulb,

the focusing position is near the relay lens group, and

the relay lens group includes the diffusing unit.

3. The projection display apparatus according to claim 1, wherein

the illuminating optical unit further includes

a light-intensity equalizing element that equalizes an intensity distribution of the light flux from the light source, and

a mirror group that leads the light flux from the light-intensity equalizing element to the light bulb,

the focusing position is near the mirror group, and

the mirror group includes the diffusing unit.

4. The projection display apparatus according to claim 1, wherein the diffusing unit is a holographic diffusing element.

5. The projection display apparatus according to claim 1, wherein the diffusing unit is a light-scattering member.

6. The projection display apparatus according to claim 1, wherein the diffusing unit is a frosted glass.

7. The projection display apparatus according to claim 2, wherein the diffusing unit is formed by making at least one surface rough from among lens surfaces in the relay lens group.

8. The projection display apparatus according to claim 2, wherein the diffusing unit is formed by forming at least one lens with a material that diffuses a light flux from among lenses in the relay lens group.

9. The projection display apparatus according to claim 2, wherein the diffusing unit is formed by attaching a light diffusing film that diffuses a light flux on at least one surface from among lens surfaces in the relay lens group.

10. The projection display apparatus according to claim 3, wherein the diffusing unit is formed by making at least one surface rough from among mirror surfaces in the mirror group.

11. The projection display apparatus according to claim 1, wherein the diffusing unit is formed by applying an antireflection coating on the diffusing unit.

12. The projection display apparatus according to claim 1, wherein the light source is a laser light source.

13. The projection display apparatus according to claim 12, wherein the light flux from the light source is guided to the intensity equalizing element via an optical fiber.