Light guiding apparatus, illumination apparatus and image projection system

• US 20060062013A1
• Filed: 09/16/2005
• Published: 03/23/2006
• Est. Priority Date: 09/22/2004
• Status: Abandoned Application

• Current Assignee: Olympus Corporation
• Original Assignee: Olympus Corporation
• Inventors: Imade, Shinichi
• Application Number:
  US11/228,076
• Publication Number:
  US 20060062013A1
• Time in Patent Office: Days
• US Class Current: 362/551
• CPC Class Codes: G02B 27/0972 Prisms prisms per se G02B5/04
• 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 9/315 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

The invention is directed to a light guiding apparatus for guiding illumination light from a light source to an illuminated area. The light guiding apparatus comprises a plurality of light guiding rods, each including a first entrance end face, a first exit end face of an area smaller than that of the first entrance end face, and a first reflection surface for guiding the illumination light incident on the first entrance end face to the first exit end face while reflecting the illumination light at an inner surface thereof; and a tapered rod including a second entrance end face, a second exit end face of an area larger than that of the second entrance end face, and a second reflection surface for guiding the illumination light to the second exit end face while reflecting the illumination light incident on the second entrance end face at an inner surface thereof, wherein each of the first exit end faces of the light guiding rods is in contact with the second entrance end face and a total of the areas of the first exit end face is almost equal to an area of the second entrance end face. The invention also relates to an illumination apparatus using the light guiding apparatus and an image projection system incorporating the illumination apparatus.

Claims

1. A light guiding apparatus for guiding illumination light from a light source to an illuminated area, comprising:

a plurality of light guiding rods, each including a first entrance end face, a first exit end face of an area smaller than that of the first entrance end face, and a first reflection surface for guiding the illumination light incident on the first entrance end face to the first exit end face while reflecting the illumination light at an inner surface thereof; and

a tapered rod including a second entrance end face, a second exit end face of an area larger than that of the second entrance end face, and a second reflection surface for guiding the illumination light to the second exit end face while reflecting the illumination light incident on the second entrance end face at an inner surface thereof,

wherein each of the first exit end faces of the light guiding rods is in contact with the second entrance end face and a total of the areas of the first exit end face is almost equal to an area of the second entrance end face.

2. The light guiding apparatus as recited in claim 1, wherein a maximum expansion angle β

1max of the illumination light emitting from the first exit end face satisfies the following equation;

β

1max≦

τ

1+(π

/2−

θ

1),

where τ

1 is an angle between a first central axis orthogonal to the first entrance end face of the light guiding rod and the first second reflection surface, and θ

1 is a critical angle at the first reflection surface.

3. The light guiding apparatus as recited in claim 1, wherein a maximum expansion angle β

2max of the illumination light incident from the second exit end face satisfies the following equation;

β

2max≦

τ

2+(π

/2−

θ

2),

where τ

2 is an angle between a second central axis orthogonal to the second exit end face of the tapered rod and the second reflection surface, and θ

2 is a critical angle at the second reflection surface.

4. The light guiding apparatus as recited in claim 1, wherein a maximum expansion angle γ

max of the illumination light emitting from the second exit end face satisfies the following equation;

γ

max≦

π

/2−

θ

−

τ

2,

where τ

2 is an angle between a second central axis orthogonal to the second exit end face of the tapered rod and the second reflection surface, and θ

2 is a critical angle at the second reflection surface.

11. An illumination apparatus using the light guiding apparatus as recited in claim 1, wherein the light source is plural and is disposed so that the emitted illumination light enters each of the first entrance end faces.

12. The illumination apparatus as recited in claim 11, wherein the plurality of light sources includes a plurality of light source elements that emits illumination light of red, green and blue, respectively, and

wherein the plurality of light source elements are disposed opposite to the first entrance end faces so that the illumination light incident on the first entrance end faces contains red, green and blue.

13. An image projection system using the illumination apparatus as recited in claim 1, comprising:

a space modulation unit illuminated by the illumination light emitted from the second exit end face or exit face; and

a projection optical unit for projecting the illumination light modulated by the space modulation unit.

5. A solid light guiding apparatus for guiding illumination light from a light source to an illuminated area along an optical axis, comprising:

a first entrance end face orthogonal to the optical axis and receiving the illumination light;

a mirror surface for guiding the illumination light incident on the first entrance end face while reflecting the illumination light at an inner surface thereof and for approaching the optical axis as the illumination light moves on to an exit side; and

an exit face for radiating the illumination light reflected at least at the mirror surface,

wherein an angle between the illumination light emitting from the exit face and the optical axis after emission is smaller than an angle before emission.

6. The solid light guiding apparatus as recited in claim 5, wherein the exit face is a wall surface of a wedge-shaped space provided on the exit side.

7. The solid light guiding apparatus as recited in claim 5, wherein illumination light satisfying a requirement for total reflection at the exit face of the illumination light that has reached the exit face is converted into another type of illumination light that enters the exit face at an angle not satisfying the requirement for total reflection while repeating reflection between the exit face and the mirror surface to be radiated from the exit face.

8. An illumination apparatus using the light guiding apparatus as recited in claim 5, wherein the light source is plural and is disposed so that the emitted illumination light enters each of the first entrance end faces.

9. The illumination apparatus as recited in claim 8, wherein the plurality of light sources includes a plurality of light source elements that emits illumination light of red, green and blue, respectively, and

wherein the plurality of light source elements are disposed opposite to the first entrance end faces so that the illumination light incident on the first entrance end faces contains red, green and blue.

10. An image projection system using the illumination apparatus as recited in claim 5, comprising:

a space modulation unit illuminated by the illumination light emitted from the second exit end face or exit face; and

a projection optical unit for projecting the illumination light modulated by the space modulation unit.