Image forming apparatus and projector using the same

• US 5,580,142 A
• Filed: 05/30/1995
• Issued: 12/03/1996
• Est. Priority Date: 05/06/1992
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Tanaka, Tsunefumi, Abe, Takeshi, Kurematsu, Katsumi
• Primary Examiner(s): Dowling, William C.
• Application Number:
  US08/454,411
• Time in Patent Office: 553 Days
• Field of Search: 353/31, 353/33, 353/34, 353/37, 353/20, 353/81, 353/84, 353/94, 353/98, 353/102, 359/40, 359/48, 359/49, 359/63, 359/64, 348/750, 348/766, 348/776-780, 348/810, 362/296, 362/307, 362/308, 362/341
• US Class Current: 353/31
• CPC Class Codes: G03B 21/2013 Plural light sources
• CPC Class Codes: G03B 21/2073 Polarisers in the lamp house peculiar to electronic spatial light modulators H04N9/3197
• 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
• CPC Class Codes: H04N 9/315 Modulator illumination systems general applications of lighting devices F21V; general optical systems G02B; lamp houses for projectors not peculiar to the presence of an electronic spatial light modulator G03B21/20

Abstract

An image forming apparatus of this invention relates to an image forming apparatus for forming a color image and, more particularly, to a projector using the image forming apparatus. The image forming apparatus includes a color light illuminating system having first and second light sources for emitting different color light components, and first, second, and third imaging units or liquid crystal light valves for modulating the color light components to form color images. The first light source is a light source for mainly emitting two color components corresponding to the images formed by the first and second imaging units, and the second light source is a color light source for mainly emitting a color component corresponding to the image formed by the third imaging unit.

Claims

1. A projector comprising:

a reflector having a substantially elliptical shape;

a light source arranged near one focal point of said reflector;

information forming means for modulating light from said light source to form information; and

a projection lens for projecting information light formed by said information forming means, said projection lens being arranged such that a pupil of said projection lens is located near the other focal point of said reflector,

wherein said information forming means is located at a position substantially equidistantly from the two focal points, so that non-image light reflected by said information forming means of the light emitted from said light source is directed toward a portion near said light source.

2. A projector according to claim 1, further comprising an interference-type mosaic filter, at a light source side of said information forming means, for transmitting a predetermined color component and reflecting remaining color components so as to focus the light from said light source in a mosaic pattern of red, green, an blue, thereby directing the reflected remaining color component near said light source.

3. A projector according to claim 1, wherein said information forming means comprises a liquid crystal light valve, and wherein a reflecting surface is formed within a fight transmitting portion of said fight valve on a light source side of said light valve, thereby directing light reflected by said reflecting surface near said light source.

4. A projector according to claim 1, further comprising polarizing converting means, formed between said light source and said information forming means, for splitting the light from said light source into a pair of polarized light components having mutually different polarization states, directing one polarized light component toward said information forming means, and returning the other polarized light component near said light source, so that at least part of said other polarized light component is converted to have a polarization state coinciding with that of said one polarized light component through said light source and said reflector.

5. A projector according to claim 4, wherein said polarizing converting means includes a grid polarizer.

6. A projector according to claim 4, wherein said polarizing converting means comprises a polarizing beam splitter and a reflecting member for reflecting said other polarized light component, and said reflecting member returns said other polarized light component near said light source through said polarizing beam splitter and is located at a position equivalent to a position substantially equidistantly spaced apart from the two focal points.

7. A light modulating apparatus comprising:

a light source;

an elliptic mirror for reflecting light from said light source, wherein said elliptic mirror has a first focal point and a second focal point in order from a side of said elliptic mirror; and

light modulating means for receiving and modulating said light reflected by said elliptic mirror, wherein said light modulating means are disposed at a substantially intermediate position between said first focal point and said second focal point such that a portion of said light is reflected to be directed to said light source.

8. A light modulating apparatus according to claim 7, wherein said light modulating apparatus is constructed so as to modulate a polarized component and a polarizing device for taking said polarized component from said light reflected by said elliptic mirror is disposed at a side of said light source in said light modulating means.

9. A light modulating apparatus according to claim 8, wherein said polarizing device includes a grid polarizing element.

10. A light modulating apparatus according to claim 8, wherein said polarizing device includes a polarization beam splitter and a plane mirror for directing a polarized component normal to said polarized component from said polarization beam splitter to said light source.

11. A light modulating apparatus according to claim 10, wherein a distance between said polarization beam splitter and said plane mirror is substantially equal to a distance between said polarization beam splitter and said light modulating means.

12. A light modulating apparatus according to claim 7, wherein an interference filter for taking light of a color from said light reflected by said elliptical mirror is formed in said light modulating means.

13. A light modulating apparatus according to claim 7, wherein a reflecting film is formed in an area where said interference filter in said light modulating means is not formed.

14. A light modulating apparatus according to claim 7, wherein a reflecting film for reflecting said portion of said light is formed in said light modulating means.

15. A light modulating apparatus according to claim 7, wherein said modulating means includes image forming means having a number of pixels.

16. A light modulating apparatus according to claim 15, further comprising a projecting optical system for projecting an image which said image forming means form.

17. A light modulating apparatus according to claim 15, wherein an interference filter for taking light of a color from said light reflected by said elliptical mirror is formed in said light modulating means.

18. A light modulating apparatus according to claim 17, wherein a reflecting film is formed in an area where said interference filter in said light modulating means is not formed.

19. A light modulating apparatus according to claim 15, wherein a reflecting film for reflecting said portion of said light is formed in said fight modulating means.

20. A light modulating apparatus according to claim 15, wherein said light modulating apparatus is constructed so as to modulate a polarized component and a polarizing device for taking said polarized component from said light reflected by said elliptic mirror is disposed at a side of said light source in said light modulating means.

21. A light modulating apparatus according to claim 20, wherein said polarizing device includes a grid polarizing element.

22. A light modulating apparatus according to claim 20, wherein said polarizing device includes a polarization beam splitter and a plane mirror for directing a polarized component normal to said polarized component from said polarization beam splitter to said fight source.

23. A light modulating apparatus according to claim 22, wherein a distance between said polarization beam splitter and said plane mirror is substantially equal to a distance between said polarization beam splitter and said light modulating means.

24. A light modulating apparatus according to claim 16, wherein a position of pupil of said projecting optical system is substantially equal to a position of said second focal point.

25. An image forming apparatus comprising:

first, second, and third imaging means for forming images in red, green and blue, respectively;

color synthesizing means for synthesizing image light components from said first, second, and third imaging means;

at least two light sources for illuminating said first, second, and third imaging means, respectively;

wherein said at least two light sources are color light sources for emitting color light mainly containing color components of said images formed by said first, second, and third imaging means, respectively; and

light amount adjusting means for adjusting the light amount of at least one of the color light sources to adjust a whim balance.