SHORT THROW PROJECTION LENS WITH A DOME

• US 20100141902A1
• Filed: 12/10/2008
• Published: 06/10/2010
• Est. Priority Date: 12/10/2008
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Hallas, James, Smith, Steve, Destain, Patrick Rene
• Granted Patent: US 8,777,427 B2
• Time in Patent Office: Days
• US Class Current: 353/69
• CPC Class Codes: G03B 21/14 Details
• CPC Class Codes: G03B 21/145 Housing details, e.g. position adjustments thereof
• CPC Class Codes: G03B 21/147 Optical correction of image distortions, e.g. keystone
• CPC Class Codes: G03B 21/28 Reflectors in projection beam in illumination beam G03B21/2066

Abstract

The present invention relates to an outer dome configured to provide protection and optical correction to a system of projection optics and the output thereof. More particularly, an optical projection system having an optical offset of greater than 100% is comprised within a projector housing having an outer dome comprised of an optically active material mounted onto an opening approximately coinciding with the optical projection system'"'"'s exit pupil. The outer dome is configured to be decenterized from the exit pupil (e.g., the center of the dome is offset from the exit pupil in one or more of an x, y, and z direction) such that it provides optical correction to a projected image. Therefore, an outer dome is configured to provide protection to optical elements provided therein and improvement of projected image quality (e.g., reduced image distortion, reduced aberration).

Claims

1. An optical projection system, comprising:

a projector housing having an opening;

a decenterized outer dome comprised of an optically active material mounted onto the opening, wherein the outer dome provides a protective barrier between inside of the projector housing an external environment; and

an optical system comprising a plurality of optical elements housed within the projector housing which projects an illumination, the optical system configured to project the illumination with an image offset of greater than 100% so that the illumination is incident onto an off axis region of the outer dome, thereby resulting in a projected image having an improved image quality due to optical effects of the outer dome.

2. The optical projection system of claim 1, wherein the improved image quality comprises a reduction in image distortion of the projected image.

3. The optical projection system of claim 2, wherein the outer dome introduces a second order distortion correction to the image distortion.

4. The optical projection system of claim 1, wherein the improved image quality comprises a reduction in an aberration of the projected image.

5. The optical projection system of claim 1, wherein the outer dome has a substantially equal thickness along a solid angle of the outer dome through which the illumination passes.

6. The optical projection system of claim 1, wherein the outer dome comprises a spherical curvature.

7. The optical projection system of claim 1, wherein the outer dome comprises a conic curvature.

8. The optical projection system of claim 1, wherein the outer dome forms a hermetic seal.

9. The optical projection system of claim 1, wherein the optical system comprises:

an illumination source to output the illumination;

a rear group of lenses coaxially configured along an optical axis to receive illumination from the illumination source and relay the illumination to the spatial light modulator; and

a spatial light modulator (SLM) configured to relay illumination from an illumination source to a set of projection optics therein.

10. The optical projection system of claim 9, wherein the projection optics comprise:

a plurality of aspheric surfaces configured to receive illumination from an illumination module and provide a reduction in optical aberration; and

a very short throw lens comprising a mirror with aspheric prescription.

11. The optical projection system of claim 9, wherein the plurality of aspheric surfaces are decenterized with respect to the opening.

12. An optical projection system, comprising:

an outer dome comprised of an optically active material that provides a protective barrier between the optical projection system and an external environment; and

an optical projection system configured to output an illumination comprising image data at an image offset of greater than 100% through an off axis region of the outer dome, comprising;

an illumination source configured to output the illumination, wherein the illumination has an image distortion;

a digital micro-mirror device (DMD) comprising mirrors configured to reflect the illumination to a downstream group of projection optics; and

a graphics driver configured to selectively tilt the mirrors in a manner that provides an output image;

13. The optical projection system of claim 12, wherein the group of projection optics comprises:

a first lens comprising a first and a second surface having an aspheric prescription, wherein the first surface is configured to receive illumination from the illumination source;

a second lens comprising a third and a fourth surface having an aspheric prescription, wherein third surface is configured to receive illumination from the first lens; and

a mirror having an aspheric prescription and a convex surface, the mirror configured to receive illumination from the second lens, spread out the illumination, and project the image onto a display screen.

14. The optical projection system of claim 13, further comprising:

a fold mirror configured to receive illumination from the first lens and to convey the illumination to the second lens, thereby reducing the distance from the illumination source to the aspheric mirror.

15. The optical projection system of claim 14, wherein the optical projection system is comprised within an interactive electronic white board configuration.

16. The optical projection system of claim 14, wherein the optical projection system is comprised within a base of a rear projection television.

17. A method for generating an optical projection system with good image quality, comprising:

providing an illumination source to output an illumination comprising image data for images, wherein the illumination has an image distortion;

positioning a rear group of coaxial optics to receive illumination from the illumination source;

providing a digital micro-mirror device (DMD) configured to receive illumination from the rear group of coaxial optics;

positioning projection optics to receive illumination from the DMD and relay the illumination to an outer dome, the projection optics having an offset of greater than 100%; and

positioning the outer dome to be decentered with respect to an axis of the optical projection system in a manner that allows illumination from the projection optics to propagate through an off axis region of the outer dome which provides an improvement in projected image quality.

18. The method of claim 17, wherein the outer dome has a substantially equal thickness through which the illumination passes.

19. The method of claim 17, wherein the illumination source comprises a light emitting diode (LED) die.

20. The method of claim 19, wherein the projection optics comprise a plurality of aspheric surfaces configured provide reduction of optical aberration.