Speckle reducting device and projector

Patent metadata

Field	Value
Publication number	US-9182608-B2
Application number	US-201113248378-A
Country	US
Kind code	B2
Filing date	Sep 29, 2011
Priority date	Sep 29, 2010
Publication date	Nov 10, 2015
Grant date	Nov 10, 2015

Abstract

A speckle reducing device includes: a polarization splitter element with a polarization splitter portion that splits incident light into first and second light containing a first and a second component respectively, which outputs the first and the second light along different directions; a first reflecting member that reflects the first light to reenter the polarization splitter element; a first conversion member disposed between the first reflecting member and the polarization splitter element, which converts the first light to third light containing the second component; a second reflecting member that reflects the third light to reenter the polarization splitter element; and a second conversion member disposed between the second reflecting member and the polarization splitter element, which converts the third light to fourth light containing the first component, wherein: the polarization splitter element outputs the second and the fourth light along one direction.

First claim

What is claimed is:

1. An optical device, comprising:
a first polarization splitter unit that splits incident light into first light having a first polarization and second light having a second polarization, and that outputs the first light and the second light;
a first reflecting unit that reflects first light output from the first polarization splitter unit back to the first polarization splitter unit;
a first partial reflecting unit disposed between the first reflecting unit and the first polarization splitter unit, which reflects a part of the first light output from the first polarization splitter unit and transmits a part of the first light output from the first polarization splitter unit;
a first conversion unit disposed between the first reflecting unit and the first polarization splitter unit, which converts light having the first polarization to light having the second polarization;
a second reflecting unit that reflects, back to the first polarization splitter unit, first light output from the first polarization splitter unit after having been reflected back to the first polarization splitter unit by the first reflecting unit; and
a second conversion unit disposed between the second reflecting unit and the first polarization splitter unit, which converts light having the second polarization to light having the first polarization.

2. An optical device according to claim 1 , wherein:
the first polarization splitter unit outputs the first light, having been reflected back to the first polarization splitter unit by the second reflecting unit, and the second light from an output surface different from a surface at which the incident light enters the first polarization splitter unit.

3. An optical device according to claim 1 , wherein:
the first partial reflecting unit reflects a part of the first light output from the first polarization splitter unit back to the first polarization splitter unit.

4. An optical device according to claim 1 , further comprising:
a second partial reflecting unit disposed between the second reflecting unit and the first polarization splitter unit, which reflects a part of the first light output from the first polarization splitter after having been reflected back to the first polarization splitter unit by the first reflecting unit, and which transmits a part of the first light output from the first polarization splitter unit after having been reflected back to the first polarization splitter unit by the first reflecting unit.

5. An optical device according to claim 4 , wherein:
the second partial reflecting unit reflects a part of the first light output from the first polarization splitter unit back to the first polarization splitter unit.

6. An optical device according to claim 1 , wherein:
the first conversion unit converts light having the first polarization to light having the second polarization by the light being passed twice through the first conversion unit.

7. An optical device according to claim 4 , wherein:
first light is reflected multiple times between the first reflecting unit and the first partial reflecting unit, and is reflected multiple times between the second reflecting unit and the second partial reflecting unit.

8. An optical device according to claim 1 , wherein:
a first air-converted length of a path extending between the first reflecting unit and the first partial reflecting unit is greater than half a coherence length of the incident light.

9. An optical device according to claim 1 , further comprising:
a second polarization splitter unit that splits and outputs first light having the first polarization and second light having the second polarization that are output from the first polarization splitter unit;
a third reflecting unit that reflects second light output from the second polarization splitter unit back to the second polarization splitter unit;
a third partial reflecting unit disposed between the third reflecting unit and the second polarization splitter unit, which reflects a part of the second light output from the second polarization splitter unit and reflects a part of the second light output from the second polarization splitter unit; and
a fourth reflecting unit that reflects, back to the second polarization splitter unit, second light output from the second polarization splitter unit after having been reflected back to the second polarization splitter unit by the third reflecting unit.

10. An optical device according to claim 1 , further comprising:
a third conversion unit that converts the first polarization of first light output from the first polarization splitter unit to the second polarization, and that converts the second polarization of second light output from the first polarization splitter unit to the first polarization;
a second polarization splitter unit that splits and outputs the first light having the second polarization and the second light having the first polarization, after those lights are output from the third conversion unit;
a third reflecting unit that reflects second light output from the second polarization splitter unit back to the second polarization splitter unit;
a third partial reflecting unit disposed between the third reflecting unit and the second polarization splitter unit, which reflects a part of the second light output from the second polarization splitter unit and transmits a part of the second light output from the second polarization splitter unit;
a fourth conversion unit disposed between the third reflecting unit and the second polarization splitter unit, which converts the first polarization to the second polarization;
a fourth reflecting unit that reflects, back to the second polarization splitter unit, second light output from the second polarization splitter unit after having been reflected back to the second polarization splitter unit by the third reflecting unit;
a fourth partial reflecting unit disposed between the fourth reflecting unit and the second polarization splitter unit, which reflects a part of the second light output from the second polarization splitter unit after having been reflected back to the second polarization splitter unit by the third reflecting unit, and transmits a part of the second light output from the second polarization splitter unit after having been reflected back to the second polarization splitter unit by the third reflecting unit; and
a fifth conversion unit disposed between the fourth reflecting unit and the second polarization splitter unit, which converts the second polarization to the first polarization.

11. An optical device according to claim 10 , further comprising:
a second partial reflecting unit disposed between the second reflecting unit and the first polarization splitter unit, which reflects a part of the first light output from the first polarization splitter after having been reflected back to the first polarization splitter unit by the first reflecting unit, and which transmits a part of the first light output from the first polarization splitter unit after having been reflected back to the first polarization splitter unit by the first reflecting unit,
wherein the first partial reflecting unit and the third partial reflecting unit are configured to be used commonly, and the second partial reflecting unit and the fourth partial reflecting unit are configured to be used commonly.

12. A speckle reducing device incorporating an optical device according to claim 1 arranged so as to reduce speckle due to the incident light.

13. An optical device according to claim 1 , wherein:
the first conversion unit is a quarter wave plate, and
the second conversion u

Assignees

• Suga Akinobu
• Nikon Corp

Inventors

• Suga Akinobu

Classifications

• G03B21/14

  Details · CPC title

• G02B27/283 Primary

  used for beam splitting or combining · CPC title

• G03B21/208

  Homogenising, shaping of the illumination light · CPC title

• G02B27/48 Primary

  Laser speckle optics · CPC title

• H04N9/3161

  using laser light sources (using laser beams scanning the display screen H04N9/3129) · CPC title