Projection system

• US 4,983,032 A
• Filed: 01/12/1990
• Issued: 01/08/1991
• Est. Priority Date: 09/01/1989
• Status: Expired due to Term

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Van Den Brandt, Adrianus H. J.
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Dowling, William C.
• Application Number:
  US07/463,752
• Time in Patent Office: 361 Days
• Field of Search: 353/34, 353/33, 353/31, 353/30, 353/37, 353/81, 353/122, 358/60, 358/61
• US Class Current: 353/30
• CPC Class Codes: H04N 9/3105 for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators simultaneous projection in colour photography G03B33/10; beam splitting or combining systems per se G02B27/10

Abstract

A projection system comprises a plurality of reflective LCDs (41, 42, 43) which are irradiated with colored sub-beams (21, 22, 23). The sub-beams are not perpendicularly incident on the LCDs so that the reflected beams (24, 25, 26) do not coincide with the incident beams. The sub-beams originate from a white light beam (20) which is split up into colored sub-beams by means of color-selective mirrors (31, 33). The same mirrors are used to combine the reflected beams (24, 25, 26) to a projection beam (27). An angle-dependent beam separater (80) is arranged so as to realize a spatial separation between the incident beams and the reflected beam. The angle-dependent beam separater (80) is arranged in such a way that the angle at which the beam (20) is incident on the color-selective mirrors (31, 33) is equal to the angle at which the reflected sub-beams (24, 25, 26) are incident on these mirrors.

Claims

1. A projection system comprising a radiation source unit (10) for generating a radiation beam (20), a modulation system for modulating the radiation beam in accordance with a picture to be displayed, and a projection lens system (60) for projecting the picture to be displayed on a projection screen, said modulation system having at least one color-selective mirror (31) for splitting the radiation beam to sub-beams (21, 22) and at least a first and a second reflective light valve (41, 42) for reflecting and modulating the sub-beams (24, 25), characterized in that the axes of the radiation path of the radiation beams incident on the light valves (41, 42) and reflected by the light valves extend at an angle to the respective normals of the planes of the light valves.

2. A projection system as claimed in claim 1, characterized in that the color-selective mirror (31, 33) is arranged in the radiation path of both the radiation beams incident on the light valves and the beams reflected by the light valves.

3. A projection system as claimed in claim 1, characterized in that the projection system comprises an angle-dependent beam separator (71, 75;

72, 76;

     80) for separating the incident and reflected radiation beams.

4. A projection system as claimed in claim 3, characterized in that the color-selective mirror (31, 33) is arranged in the radiation path between the reflective light valves (41, 42, 43) and the angle-dependent beam separator (80).

5. A projection system as claimed in claim 1, characterized in that a first plane in which the axes of the radiation path of the sub-beams (22, 25) incident on the first light valve and reflected thereby are located and a second plane in which the radiation path of the sub-beams (23, 26) incident on the second light valve and reflected thereby are located, extend at an angle of more than zero.

6. A projection system as claimed in claim 5, characterized in that the said first plane and the said second plane intersect each other in accordance with the line of intersection which is parallel to a line of intersection of a plane of the color-selective mirror and a plane of a reflective light valve.

7. A projection system as claimed in claim 1, in which the modulation system has two color-selective mirrors (31, 33) for splitting the radiation beam generated by the radiation source unit into a red, a green and a blue sub-beam and three reflective light valves (41, 42, 43) for modulating the three sub-beams with parts of a picture to be displayed.