Multi-zoned dichroic mirror for liquid crystal projection system

• US 5,708,530 A
• Filed: 03/29/1996
• Issued: 01/13/1998
• Est. Priority Date: 03/29/1996
• Status: Expired due to Term

• Current Assignee: Transpacific IP Group Limited
• Original Assignee: Electronics Research & Service Organization
• Inventors: Huang, Tsai-Yun
• Primary Examiner(s): Epps, Georgia Y.
• Assistant Examiner(s): MACK, RICKY LEVERN
• Application Number:
  US08/622,883
• Time in Patent Office: 655 Days
• Field of Search: 359/634, 359/583, 359/490
• US Class Current: 359/634
• CPC Class Codes: G02B 27/142 Coating structures, e.g. thin films multilayers

Abstract

A multi-zoned dichroic mirror for use in a liquid crystal projection system that is capable producing projected images having improved color uniformity including a dichroic mirror which is divided into at least two regions of a first and a second region, a first region on the dichroic mirror that is coated with a first dichroic coating which compensates for color variations caused by variations in the incident angles of the incident light beams in a positive manner, and a second region on the dichroic mirror coated with second dichroic coating which compensates for color variation caused by variations in the incident angles of the incident light beams in a negative manner.

Claims

1. A dichroic mirror for use in a liquid crystal projection system to produce projected color images comprising:

a dichroic mirror divided into at least two regions characterized by a first region and a second region,

said first region on said dichroic mirror coated with a first dichroic coating, said first dichroic coating compensates for color variations caused by the variations in the angles of incident light beams by shifting a spectrum toward a longer wavelength, and

said second region on said dichroic mirror coated with a second dichroic coating, said second dichroic coating compensates for color variations caused by the variations in the angles of incident light beams by shifting said spectrum toward a shorter wavelength.

2. A dichroic mirror according to claim 1, wherein for each increased degree of the angle of the incident light beam, the spectrum is shifted toward a shorter wavelength by between 1.0 nm and 2.0 nm.

3. A dichroic mirror according to claim 1, wherein for each decreased degree of the incident angle of the incident light beams, the spectrum is shifted toward a longer wavelength by between 1.0 nm and 2.0 nm.

4. A dichroic mirror according to claim 1, wherein said first dichroic coating generates a spectrum which shifts toward a longer wavelength in an uncorrected spectrum.

5. A dichroic mirror according to claim 1, wherein said second dichroic coating generates a spectrum which shifts toward a shorter wavelength in an uncorrected spectrum.

6. A dichroic mirror according to claim 1, wherein said first and said second dichroic coating comprise alternating layers of titanium oxide and silicon oxide.

7. A dichroic mirror according to claim 1, wherein said first and said second dichroic coating are each deposited on a glass substrate.

8. A dichroic mirror according to claim 1, wherein said first and said second dichroic coating have a total of between 20 layers and 40 layers of titanium oxide and silicon oxide.

9. A dichroic mirror for use in a liquid crystal projection system for producing projected color images comprising:

a dichroic mirror divided into three regions characterized by a first, a second, and a third region,

said first region on said dichroic mirror coated with a first dichroic coating, said first dichroic coating compensate for colored variations caused by variations in the incident angles of incident light beams in a first manner, and

said second region on said dichroic mirror coated with a second dichroic coating, said second dichroic coating compensates for color variation caused by variations in the incident angles of incident light beams in a second manner, and

said third region on said dichroic mirror situated in between said first and said second regions coated with a third dichroic coating, which does not compensate for color variation.

10. A dichroic mirror according to claim 9, wherein said three regions are of approximately equal area.

11. A dichroic mirror according to claim 9, wherein said first dichroic coating compensate for color variations by generating a spectrum which shifts toward a longer wavelengths.

12. A dichroic mirror according to claim 9, wherein said second dichroic coating compensate for color variations by generating a spectrum which shifts toward a shorter wavelength.