Display apparatus with two polarization compensators

• US 7,184,115 B2
• Filed: 08/05/2005
• Issued: 02/27/2007
• Est. Priority Date: 01/07/2002
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Moxtek (Polatechno Co.,Ltd.)
• Inventors: Kurtz, Andrew F., Kessler, David, Mi, Xiang-Dong
• Primary Examiner(s): CHOWDHURY, TARIFUR RASHID
• Application Number:
  US11/198,916
• Publication Number:
  US 20060033976A1
• Time in Patent Office: 571 Days
• Field of Search: 349/5, 349/9, 349/96, 349117-119, 353/8, 353/20, 359/486
• US Class Current: 349/119
• 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 contrast modulation of an incident light beam comprising:

(a) a wire grid prepolarizer for modifying the polarization of said incident beam of light to provide a polarized beam of light;

(b) a wire grid polarization beamsplitter for receiving said polarized beam of light, for transmitting said polarized beam of light having a first polarization, and for reflecting said polarized beam of light having a second polarization orthogonal to said first polarization;

(c) a reflective spatial light modulator which receives said polarized beam of light, having either a first polarization or a second polarization, and then selectively modulates said polarized beam of light to encode data thereon, providing both modulated light and unmodulated light which differ in polarization;

(d) wherein said reflective spatial light modulator reflects back both said modulated light and said unmodulated light to said wire grid polarization beamsplitter;

(e) wherein a first polarization compensator, located between said wire grid polarization beamsplitter and said reflective spatial light modulator, conditions the polarization states of oblique and skew light rays relative to said wire grid polarization beamsplitter, or said reflective spatial light modulator, or both;

(f) wherein said wire grid polarization beamsplitter separates said modulated light from said unmodulated light;

(g) a wire grid polarization analyzer which receives said modulated light, and which further removes any residual unmodulated light from said modulated light;

(h) a second polarization compensator, which is provided for conditioning the polarization states of oblique and skew rays relative to said wire grid polarization beamsplitter and to either of said wire grid polarization analyzer or said wire grid prepolarizer; and

(g) wherein said first compensator and said second compensator each comprise one or more birefringement layers, wherein said birefringement layers comprise at least one of the following;

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

2. A modulation optical system for providing contrast modulation of an incident light beam comprising:

(a) a wire grid prepolarizer for modifying the polarization of said incident beam of light to provide a polarized beam of light;

(b) a wire grid polarization beamsplitter for receiving said polarized beam of light, for transmitting said polarized beam of light having a first polarization, and for reflecting said polarized beam of light having a second polarization orthogonal to said first polarization;

(c) a reflective spatial light modulator which receives said polarized beam of light, having either a first polarization or a second polarization, and selectively modulates said polarized beam of light to encode data thereon, providing both modulated light and unmodulated light which differ in polarization;

(d) wherein said reflective spatial light modulator reflects back both said modulated light and said unmodulated light to said wire grid polarization beamsplitter;

(e) wherein a first polarization compensator, located in the portion of the optical path that includes said wire grid polarization beamsplitter and said reflective spatial light modulator, conditions the polarization states of oblique and skew light rays relative to said wire grid polarization beamsplitter, or said reflective spatial light modulator, or both;

(f) wherein said wire grid polarization beamsplitter separates said modulated light from said unmodulated light;

(g) a wire grid polarization analyzer which receives said modulated light, and which further removes any residual unmodulated light from said modulated light;

(h) a second polarization compensator, which is provided for conditioning the polarization states of oblique and skew rays relative to said wire grid polarization beamsplitter and to either of said wire grid polarization analyzer or said wire grid prepolarizer; and

(g) wherein said first compensator and said second compensator each comprise one or more birefringement layers, wherein said birefringement layers comprise at least one of the following;

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

3. A modulation optical system for providing contrast modulation of an incident light beam comprising:

(a) a prepolarizer for modifying the polarization of said incident beam of light to provide a polarized beam of light;

(b) a wire grid polarization beamsplitter for receiving said polarized beam of light, for transmitting said polarized beam of light having a first polarization, and for reflecting said polarized beam of light having a second polarization orthogonal to said first polarization, wherein sub-wavelength wires on said wire grid polarization beamsplitter face a reflective spatial light modulator;

(c) wherein said reflective spatial light modulator which receives said polarized beam of light, having either a first polarization or a second polarization, selectively modulates said polarized beam of light to encode data thereon, providing both modulated light and unmodulated light which differ in polarization;

(d) wherein said reflective spatial light modulator reflects back both said modulated light and said unmodulated light to said wire grid polarization beamsplitter;

(e) wherein a first polarization compensator, located in the portion of the optical path that includes said wire grid polarization beamsplitter and said reflective spatial light modulator, conditions the polarization states of oblique and skew light rays relative to said wire grid polarization beamsplitter, or said reflective spatial light modulator, or both;

(f) wherein said wire grid polarization beamsplitter separates said modulated light from said unmodulated light;

(g) a polarization analyzer which receives said modulated light, and which further removes any residual unmodulated light from said modulated light;

(h) a second polarization compensator, which is provided for conditioning the polarization states of oblique and skew rays relative to said wire grid polarization beamsplitter and to either of said polarization analyzer or said prepolarizer; and

(g) wherein said first compensator and said second compensator each comprise one or more birefringement layers, wherein said birefringement layers comprise at least one of the following;

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