Polarization converting element and projector provided with same

• US 7,845,800 B2
• Filed: 02/01/2006
• Issued: 12/07/2010
• Est. Priority Date: 02/02/2005
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Fujinawa, Nobuhiro
• Primary Examiner(s): Epps; Georgia Y
• Assistant Examiner(s): Chowdhury; Sultan
• Application Number:
  US11/883,297
• Publication Number:
  US 20080291399A1
• Time in Patent Office: 1,770 Days
• Field of Search: 353/20, 353/81, 353/98, 353/99, 353/22, 353/23, 353/24, 359/483, 359/495, 359/496, 359/631, 359/208.1, 359/583, 359/487, 359/490, 359/491, 359/492, 349/5, 349/8, 349/9, 362/19
• US Class Current: 353/20
• CPC Class Codes: G02B 19/0019 having reflective surfaces only (e.g. louvre systems, systems with multiple planar reflectors)
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• CPC Class Codes: G02B 19/0061 the light source comprising a LED semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission H01L33/00
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 27/286 for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another G02B5/3083 takes precedence; light guide coupling means utilising polarising elements G02B6/34

Abstract

A polarization converting element includes: a main body that is made from a transparent member; an incident section that is provided to the main body, and upon which light generated from a light source is incident; an annular reflecting section that is formed on the periphery of the incident section; and a polarization splitting section that is formed opposite to the annular reflecting section on the emission side of light incident upon the incident section. One polarized light component of the incident light passes through the main body and is emitted from the polarization splitting section. Another polarized light component of the incident light is reflected towards the annular reflecting section by the polarization splitting section, and is emitted from the polarization splitting section after having again been reflected by the annular reflecting section and having been converted into light of a same polarization component as the light of the one polarized light component.

Claims

1. A polarization converting element, comprising:

a main body that is made from a transparent member and that has the following integral sections of the main body;

an incident section upon which light generated from a light source is incident;

an annular reflecting section that is formed on the periphery of the incident section; and

a polarization splitting section that is formed opposite to the annular reflecting section on the emission side of light incident upon the incident section, wherein;

one polarized light component of the incident light passes through the main body and is emitted from the polarization splitting section; and

another polarized light component of the incident light is reflected towards the annular reflecting section by the polarization splitting section, and is emitted from the polarization splitting section after having again been reflected by the annular reflecting section and having been converted into light of a same polarization component as the light of the one polarized light component.

2. A polarization converting element according to claim 1, wherein:

the incident section is endowed with a condensing function.

3. A polarization converting element according to claim 1, wherein:

the polarization splitting section is formed with an outwardly concave conical surface shape.

4. A polarization converting element according to claim 3, wherein:

the polarization splitting section has a concave curved surface shape in the neighborhood of an axis of rotational symmetry of the concave conical surface; and

the light of the one polarized light component is emitted from a portion of the concave curved surface shape substantially parallel to the axis of rotational symmetry.

5. A polarization converting element according to claim 1, wherein:

the annular reflecting section is formed with an inwardly convex conical surface shape.

6. A polarization converting element according to claim 1, wherein:

the main body, the incident section, the annular reflecting section, and the polarization splitting section are formed with rotationally symmetric shapes.

7. A polarization converting element according to claim 1, wherein:

the main body is formed in a shape of a cylinder one end of which is closed by a wall having an inner surface, on which the incident section and the annular reflecting section are formed, and an outer surface, on which the polarization splitting section is formed.

8. A polarization converting element according to claim 1, wherein:

the polarization splitting section is a polarization splitting layer formed upon a surface of the main body.

9. A polarization converting element according to claim 1, wherein:

the annular reflecting section comprises a quarter-wave plate and a reflecting surface, formed upon a surface of the main body.

10. A projection device, comprising:

a light source;

a polarization converting element according claim 1, that emits light generated from the light source as light of a single polarized component;

a display panel upon which the light emitted from the polarization converting element is incident; and

a projection optical system that projects light that has passed through the display panel upon a screen.

11. A projection device according to claim 10, wherein:

the light source is a point light source.

12. A projection device according to claim 10, wherein:

the projection optical system comprises a polarization splitting section, a quarter-wave plate, and a condensing mirror; and

light that has passed through the display panel is reflected by the polarization splitting section and passes through the quarter-wave plate, and then, after having been reflected by the condensing mirror, passes through the quarter-wave plate and the polarization splitting section.