# US 5,708,530 A · Multi-zoned dichroic mirror for liquid crystal projection system

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 5,708,530 A
- Document ID: US5708530A
- Status: Granted
- Kind: A
- Application number: 08/622,883
- Filed: 1996-03-29
- Granted: 1998-01-13
- Earliest claimed: 1996-03-29
- Assignees: Electronics Research & Service Organization
- Inventors: Tsai-Yun Huang
- Web page: https://patentgrep.com/patent/US5708530A

## CPC

- G02B 27/142: {Coating structures, e.g. thin films multilayers}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## 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

### Claim 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.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 1)

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.

### Claim 4 (depends on 1)

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.

### Claim 5 (depends on 1)

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.

### Claim 6 (depends on 1)

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

### Claim 7 (depends on 1)

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

### Claim 8 (depends on 1)

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.

### Claim 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.

### Claim 10 (depends on 9)

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

### Claim 11 (depends on 9)

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.

### Claim 12 (depends on 9)

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.