Modulation optical system

• US 20040218125A1
• Filed: 05/27/2004
• Published: 11/04/2004
• Est. Priority Date: 01/07/2002
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Moxtek Inc (Nippon Kayaku Company Limited)
• Inventors: Kurtz, Andrew F., Kessler, David, Mi, Xiang-Dong
• Granted Patent: US 6,897,926 B2
• Time in Patent Office: Days
• US Class Current: 349/117
• CPC Class Codes: G02B 27/18 for optical projection, e.g. combination of mirror and condenser and objective photographic, cine and overhead projectors G03B21/00; photographic projection printing G03B27/32; photolithographic projectors G03F7/20; projection television H04N5/74; colour projection television H04N9/31
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 5/3016 involving passive liquid crystal elements optical properties of liquid crystals G02F1/0063; polarising elements associated with active liquid crystal devices G02F1/133528
• CPC Class Codes: G02B 5/3058 comprising electrically conductive elements, e.g. wire grids, conductive particles
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133548 Wire-grid polarisers
• CPC Class Codes: G02F 1/133634 the refractive index Nz perpendicular to the element surface being different from in-plane refractive indices Nx and Ny, e.g. biaxial or with normal optical axis
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: G02F 2203/02 reflective
• CPC Class Codes: H04N 9/3108 by using a single electronic spatial light modulator
• CPC Class Codes: H04N 9/3167 for polarizing the light beam polarizing optical systems per se G02B27/28
• CPC Class Codes: H04N 9/3191 Testing thereof testing of displays in general G09G3/006

Abstract

A projection display apparatus (10) uses a modulation optical system (200) that includes a liquid crystal device (210) in combination with a wire grid polarization beamsplitter (240), a wire grid polarization analyzer (270) and a projection lens (285) to form an image. In order to achieve high contrast and maintain high brightness levels, a compensator (260) is provided for minimizing leakage light for pixels in the black (OFF) state. A number of configurations are possible, such as with the compensator (260) disposed in the optical path between the liquid crystal device (210) and the wire grid polarization beamsplitter (240) and with a secondary compensator (265) disposed between wire grid polarization analyzer (270) and the wire grid polarization beamsplitter (240).

Claims

1. A modulation optical system for providing high contrast modulation of an incident light beam, comprising:

(a) a wire grid pre-polarizer for pre-polarizing said beam of light;

(b) a transmissive liquid crystal device for selectively modulating said polarized beam of light having to encode image data thereon in order to form a modulated beam;

(c) a wire grid polarization analyzer which transmits said modulated beam and blocks light of the opposite polarization; and

(d) a compensator located between said wire grid pre-polarizer and said wire grid polarization analyzer which conditions oblique and skew rays.

2. The system of claim 1 wherein said compensator comprises one or more birefringent layers, wherein said birefringent layers comprise at least one of the following;

an A-plate film, a C-plate film, or a biaxial film.

3. The A-plate according to claim 2 wherein the optical axis of said A-plate is substantially parallel to the sub-wavelength wires of said wire grid polarization analyzer.

4. The A-plate according to claim 2 wherein the optical axis of said A-plate is substantially perpendicular to the sub-wavelength wires of said wire grid polarization analyzer.

5. The system of claim 1 wherein said reflective liquid crystal device has a vertically aligned construction.

6. The apparatus of claim 1 wherein the polarization axis orientation of said wire grid pre-polarizer is perpendicular to the polarization axis orientation of said wire grid polarization analyzer.

7. The apparatus of claim 1 wherein the polarization axis orientation of said wire grid pre-polarizer is parallel to the polarization axis orientation of said wire grid polarization analyzer.

8. The system of claim 1 wherein said compensator is located between said transmissive liquid crystal device and said wire grid polarization analyzer.

9. The system of claim 1 wherein said compensator is located between said wire grid pre-polarizer and said transmissive liquid crystal device.