Projection type display including a holographic diffuser

• US 5,808,759 A
• Filed: 11/27/1996
• Issued: 09/15/1998
• Est. Priority Date: 11/30/1995
• Status: Expired due to Fees

• Current Assignee: Advantest Corporation, Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Kida, Hiroshi, Daijogo, Akira, Taguchi, Hirokazu, Shikama, Shinsuke, Okamori, Shinji
• Primary Examiner(s): Henry, Jon W.
• Application Number:
  US08/758,016
• Time in Patent Office: 657 Days
• Field of Search: 359/15, 359/16, 359/837, 359/599, 359/709, 349/64, 349/67, 362/308, 362/328, 355/67
• US Class Current: 359/15
• CPC Class Codes: G02B 5/0252 using holographic or diffractive means
• CPC Class Codes: G02B 5/0278 used in transmission
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• 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

A light source device including a light emitting element emits a luminous flux, which is converged by a reflecting mirror. A conical light-refracting element receives the luminous flux converged by the reflecting mirror and changes the cone angle of the luminous flux. The luminous flux exiting the conical light-refracting element is diffused by a holographic diffuser and is then converged by at least one lens. The reflecting mirror may have an elliptic curvature or a parabolic curvature. The light source device is also used to form a projector for a projection type display apparatus. In the projector, the luminous flux emitted from the light source device may be separated by color separators into a plurality of colors of light. Then, each color of light is directed to the corresponding one of a plurality of light valves. Then, a color synthesizer synthesizes the colors of light emitted from the light valves into a composite image which in turn is projected onto a screen. A plurality of such projectors are used to construct a multiscreen projection type display system where each of the projectors projects a corresponding image. At least one reflecting mirror for bending a corresponding one of the images is included in the multiscreen projection type display system. The reflecting mirror projects the image onto a screen so that the images emitted from the plurality of projectors are combined into a composite image on the screen.

Claims

1. A light source apparatus, comprising:

a light emitting element emitting a luminous flux;

a reflecting mirror converging the luminous flux emitted by said light emitting element;

a conical light-refracting element changing a cone angle of the luminous flux converged by said reflecting mirror;

a lens converging the light exiting said conical light-refracting element; and

a holographic diffuser causing the luminous flux to diffuse, wherein said holographic diffuser is disposed in a light path between said conical light-refracting element and said lens.

2. The light source apparatus according to claim 1, wherein said reflecting mirror is an elliptical mirror having an ellipsoidal surface of revolution centered on an optical axis thereof and having a first focal point and a second focal point, and said light emitting element is disposed in proximity to the first focal point.

3. The light source apparatus according to claim 2, wherein said light emitting element is a discharge lamp and a middle portion of a light-emitting portion of said discharge lamp is on the optical axis between said first and second focal points of said elliptical mirror so that 0.6≦

e≦

0.75 and 0.06≦

Δ

/f1≦

0.2

where f1 is a first focal length of said elliptical mirror, e is an eccentricity of said elliptical mirror, and Δ

is a distance from the first focal point to the middle portion.

4. The light source apparatus according to claim 1, wherein said reflecting mirror has a parabolic curvature described by the rotation of a curve derived from equations

5. The light source apparatus according to claim 1, wherein said conical light-refracting element is disposed in proximity to a focal point of said reflecting mirror.

6. The light source apparatus according to claim 5, wherein said conical light-refracting element is disposed so that light is incident upon a flat surface thereof and an axis thereof is substantially aligned with an optical axis of said reflecting mirror.

7. The light source apparatus according to claim 1, wherein said holographic diffuser is disposed in proximity to a front focal point of said lens.

8. A projection type display apparatus incorporating said light source apparatus according to claim 1, comprising:

a light valve producing an image;

said light source apparatus emitting a luminous flux to illuminate said light valve; and

a projection lens enlarging and projecting the image emitted by said light valve.

9. The projection type display apparatus according to claim 8, further comprising:

color separating means separating the luminous flux emitted from said light source apparatus into a plurality of colors of light;

a plurality of light valves each of which is disposed in a light path of a corresponding color of light; and

color synthesizing means disposed between said light valves and said projection lens, said color synthesizing means synthesizing the plurality of colors of light into an image.

10. The projection type display apparatus according to claim 9, wherein said color separating means includes a dichroic mirror, and said color synthesizing means is a dichroic prism.

11. The projection type display apparatus according to claim 9, wherein said color separating means includes a dichroic filter, and said color synthesizing means is a dichroic prism.

12. A multi-projection type display system incorporating a plurality of projection type display apparatuses according to claim 8 each of which projects a corresponding image, the system further comprising:

at least one reflecting mirror bending a corresponding one of said images from said projection type display apparatuses; and

a screen onto which said reflecting mirror projects the images so that the images emitted from said plurality of projection type display apparatuses are combined into a composite image on said screen.

13. The multi-projection type display system according to claim 12, wherein each of said projection type display apparatuses includes:

color separating means separating the received luminous flux emitted from said light source apparatus into a plurality of colors of light;

a plurality of light valves each of which is disposed in a light path of a corresponding color of light; and

color synthesizing means disposed between said light valves and said projection lens, said color synthesizing means synthesizing the plurality of colors of light into an image.

14. The light source apparatus according to claim 1, said holographic diffuser shaping an input luminous flux into an output flux having a different cross section than the input luminous flux.

15. The light source apparatus according to claim 14, wherein said holographic diffuser is a circular holographic diffuser shaping the input luminous flux into an output luminous flux having a circular cross section.

16. The light source apparatus according to claim 14, wherein said holographic diffuser is an elliptical holographic diffuser shaping the input luminous flux into an output luminous flux having an elliptical cross section.

17. The light source apparatus according to claim 14, wherein said holographic diffuser is a rectangular holographic diffuser shaping the input luminous flux into an output luminous flux having a rectangular cross section.