Apparatus and method for image projection with pixel intensity control

• US 5,589,852 A
• Filed: 06/07/1995
• Issued: 12/31/1996
• Est. Priority Date: 02/27/1989
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Thompson, E. Earle, DeMond, Thomas W.
• Primary Examiner(s): BRIER, JEFFERY A
• Application Number:
  US08/472,377
• Time in Patent Office: 573 Days
• Field of Search: 345/102, 345/147, 345/148, 348/195-205, 348/750-757, 348/707, 348/771, 348/743
• US Class Current: 345/690
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: G09F 19/16 involving the use of mirrors
• CPC Class Codes: G09F 19/18 involving the use of optical projection means, e.g. projection of images on clouds projection apparatus per se G03B
• CPC Class Codes: G09F 9/372 the positions of the elements being controlled by the application of an electric field
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0814 used for selection purposes, e.g. logical AND for partial update
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0847 being a dynamic memory without any storage capacitor, i.e. with use of parasitic capacitances as storage elements
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/0262 The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
• CPC Class Codes: G09G 2310/066 Waveforms comprising a gently increasing or decreasing portion, e.g. ramp
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 3/2007 Display of intermediate tones
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/2025 the sub-frames having all the same time duration
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/346 based on modulation of the reflection angle, e.g. micromirrors micromirrors devices per se G02B26/0833
• CPC Class Codes: H04N 13/363 using image projection screens volumetric display H04N13/388
• CPC Class Codes: H04N 13/395 : with depth sampling, i.e. the volume being constructed from a stack or sequence of 2D image planes
• CPC Class Codes: H04N 13/398 : Synchronisation thereof; Control thereof
• CPC Class Codes: H04N 5/7458 : the modulator being an array of deformable mirrors, e.g. digital micromirror device [DMD]
• CPC Class Codes: H04N 9/3111 : for displaying the colours sequentially, e.g. by using sequentially activated light sources sequential projection in colour photography G03B33/08
• CPC Class Codes: H04N 9/3161 : using laser light sources using laser beams scanning the display screen H04N9/3129
• CPC Class Codes: H04N 9/3179 : Video signal processing therefor

Abstract

A digital video system including a light source and a spatial light modulator system. Varying intensities of light to achieve gray shades either with a monochrome system or within each color can be accomplished in several ways. The intensity of the light source itself can be modulated to provide variation, the spatial light modulator elements can have their states in which light is directed to a surface to form a pixel modulated, or both.

Claims

1. A method for varying intensity of a pixel comprising:

a. varying the intensity of light produced from at least one light source such that said light source produces at least two distinct levels of illumination along a first optical path;

b. reflecting light from said light source in said first optical path to form said pixel in a second optical path; and

c. varying the amount of time said light source is reflected into said second optical path.

2. The method of claim 1 wherein said at least one light source includes a coherent light source.

3. The method of claim 2 wherein said at least one light source further comprises three coherent light sources, one producing red light, one producing green light and one producing blue light.

4. The method of claim 3 wherein said intensity varying step further comprises controlling the intensity of each colored coherent light source to color said pixel.

5. The method of claim 1 wherein said intensity varying step comprises using a variably graded filter and a light source generator.

6. The method of claim 1 wherein said at least one light source is such that said pixel is colored by sequencing colors from said source or sources.

7. The method of claim 6 wherein said colors are sequenced such that one color is used more frequently than the other of said colors.

8. The method of claim 1 wherein said intensity varying step is done such that said variations of intensity occur at a frequency above the critical flicker frequency of the human eye.

9. The method of claim 1 wherein said varying step is done such that said time variations occur at a frequency higher than the critical flicker frequency of the human eye.