Video projection apparatus

• US 4,989,076 A
• Filed: 01/25/1988
• Issued: 01/29/1991
• Est. Priority Date: 01/27/1987
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Owada, Mitsuru, Nagashima, Yoshitake, Tajima, Mizuho
• Primary Examiner(s): Britton, Howard W.
• Application Number:
  US07/147,519
• Time in Patent Office: 1,100 Days
• Field of Search: 358/60, 358/61, 358/232, 358/236, 340/784, 350/337, 350/338, 350/345, 350/401, 350/403, 350/408, 353/31, 353/34
• US Class Current: 348/751
• 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 9/3167 for polarizing the light beam polarizing optical systems per se G02B27/28

Abstract

An apparatus for receiving the illumination light from an illumination light souce and for providing a color image on a projection lens includes three displays responsive to a video signal for modulating incident light to display respective component images. Also included are a first dichroic layer for separating the illumination light into a first light component and a first mixed light of different wavelengths to transmit the first light component to one of the displays, a second dichroic layer for separating the mixed light into second and third light component of different wavelengths to transmit the second and third light component to the other two of the displays, respectively, a third dichroic layer for combining the first and second information lights from the first two displays, and a fourth dichroic layer for further combining the information light combined by the third dichroic layer with a third information light from the third display.

Claims

1. An apparatus, receiving a polarized light, for providing a color image on a projection lens, comprising:

(a) first, second and third display device for modulating incident light in response to a video signal to display respective component images;

(b) a first dichroic layer for separating the polarized light into a first light component and a first mixed light of different wavelength regions from each other and for providing said first light component to said first display device;

(c) a second dichroic layer for separating said first mixed light into second and third light components of different wavelength regions from each other, and for providing said second and said third light components to said second and third display devices, respectively;

(d) a third dichroic layer for synthesizing first and second information lights from said first and second display devices; and

(e) a fourth dichroic layer for further synthesizing the light synthesized by said third dichroic layer with a third information light from said third display device; and

wherein said first, second, third, and fourth dichroic layers extend parallel to each other, and wherein said first dichroic layer separates the polarized light after it passes through an optical element for rotating a plane of polarization of the polarizing light by 90° and

generates a first polarizing beam which does not pass through the optical element and a second polarized beam which passes through the optical element and has a same plane of polarization as the first polarized beam.

2. An apparatus according to claim 1, wherein said first dichroic layer separates out said illumination light into a light component comprising a green light component and first mixed light comprising a red-blue mixed light, and wherein said second dichroic layer separates said red-blue mixed light into second and third light components comprising a red light component and a blue light component.

3. An apparatus according to claim 1, wherein said first dichroic layer separates out said illumination light into a light component comprising a red light component and a first mixed light comprising green-blue mixed light, and wherein said second dichroic layer separates said green-blue mixed light into second and third light components comprising a green light component and a blue light component.

4. An apparatus according to claim 1, wherein said third dichroic layer synthesizes first and second information lights comprising green information light and blue information light, and wherein said fourth dichroic layer synthesizes the light synthesized by said third dichroic layer with the third information light comprising red information light.

5. An apparatus according to claim 1, wherein said third dichroic layer synthesizes first and second information lights comprising red information light and blue information light, and wherein said fourth dichroic layer synthesizes the light synthesized by said third dichroic layer with the third information light comprising green information light.

6. An apparatus according to claim 1, wherein said second display device is positioned between said second and third dichroic layers.

7. An apparatus according to claim 1, further comprising first and second mirrors, wherein said first mirror reflects the first light component separated by said first dichroic layer toward said first display device, wherein said first display device is positioned between said first mirror and said third dichroic layer, wherein said second mirror reflects said third light component separated by said second dichroic layer toward said fourth dichroic layer, and wherein said third display device is positioned between said second dichroic layer and said second mirror.

8. An apparatus according to claim 1, further comprising:

(f) a first substrate supporting said first and said third dichroic layers; and

(g) a second substrate supporting said second and said fourth dichroic layers.

9. An apparatus according to claim 2, wherein the two kinds of dichroic layers on said substrate are provided in partition.

10. An apparatus according to claim 2, wherein the two kinds of dichroic layers on said substrate are provided in partly superimposed relation.

11. An apparatus for providing a color image on a projection lens, comprising:

(a) an illumination device for generating illumination light which passes through a polarizing beam splitter to provide a polarized beam, said beam splitter having an optical element for rotating a plane of polarization of the polarizing beam by 90° and

generating a first polarizing beam which does not pass through said optical element and a second polarizing beam which passes through said optical element and has a same plane of polarization as said first polarizing beam;

(b three display devices for modulating said illumination light incident thereon in response to a video signal to display respective component images, wherein said display devices are liquid crystal displays each having no polarizer;

(c) component light forming means, comprising dichroic layers, for receiving said illumination light, wherein said dichroic layers are of different wavelength separation characteristics for successively separating said illumination light into red, blue and green components, and for providing said red, blue, and green components to said three display devices respectively, wherein said dichroic layers extend parallel to each other; and

(d) information light synthesizing means for conducting information lights of red, blue and green from aid display devices successively to dichroic layers of different wavelength separation characteristics to synthesize said red, blue, and green information lights.

12. An apparatus according to claim 11, wherein said component light forming means separates the illumination light incident thereon into a reflected light and a transmitted light by a first dichroic layer, and further separates one of the reflected light and the transmitted light into a reflected light and a transmitted light by a second dichroic layer.

13. An apparatus according to claim 11, wherein said information light synthesizing means synthesizes light transmitted through a third dichroic layer with light reflected from the third dichroic layer, and wherein one of the synthesized light and the remaining information light is reflected and the other of which is transmitted to effect synthesizing.

14. An apparatus according to claim 11, wherein said information light synthesizing means extends parallel to said component light forming means.

15. An apparatus according to claim 11, wherein one of said display devices is positioned between said component light forming means and said information light synthesizing means.