WO2009070134A1

WO2009070134A1 - System and method for anamorphic illumination of a display system

Info

Publication number: WO2009070134A1
Application number: PCT/US2007/024477
Authority: WO
Inventors: Ming Xu
Original assignee: Thomson Licensing
Priority date: 2007-11-28
Filing date: 2007-11-28
Publication date: 2009-06-04

Abstract

A system for anamorphically illuminating a display system, comprising a light beam spot shaper adapted to receive light from a light source and transmit the light as a shaped light beam to an integrator input face is disclosed.

Description

SYSTEM AND METHOD FOR ANAMORPHIC ILLUMINATION OF A DISPLAY SYSTEM

Field of the Invention

The present invention is related to the field of display systems.

Background of the Invention

One measure of a display system's efficiency relates to how efficiently light from a light source is provided to an imager of the display system. An upper limit of a range of possible brightness levels emitted by a display system is undesirably reduced if light emitted by the light source is not efficiently delivered to the imager. Typically, the light source emits light in the form of a light beam having a substantially constant solid angle. Some display systems utilize optical integrators to collimate light from the light source and facilitate transmission of the collimated light to the imager. An area of a plane illuminated by the light beam, where the plane is substantially coplanar to an integrator input face, may be referred to as a conventional input beam spot. As shown in Prior Art Figure 1, the conventional input beam spot 100 is represented as a substantially circular uncrosshatched area surrounded by a dark area 102 (shown as crosshatched) that is not illuminated by the conventional input beam spot 100.

In an ideal display system, each optical component has the same etendue or optical extent. However, design limitations often prevent an ideal implementation of providing optical components with closely matched etendue values. A prevalent problem in display systems relates to the drastic geometric mismatch between the shape of the conventional input beam spot 100 of a conventional light source and a conventional integrator input face 104 as shown in Prior Art Figure 1. The conventional input beam spot 100 of a conventional light source is substantially circular while the conventional integrator input face 104 is substantially rectangular, sometimes having a size ratio of 16x9. The differences in shapes contribute to an etendue mismatch and corresponding loss of light transmission efficiency from the light source to the imager. While the conventional input beam spot is substantially circular (having a horizontal axis X and a vertical axis Y), the conventional integrator input face 104 is substantially rectangular (having a horizontal axis X' and a vertical axis Y'). Because the conventional input beam spot 100 should illuminate the entire area of the conventional integrator input face 104 to ensure that light strikes the entire area of the imager, it is shown in Fig. 1 that the conventional input beam spot 100 substantially circumscribes the conventional integrator input face 104. Accordingly, the portion of the conventional input beam spot 100 that does not strike the conventional integrator input face 104 is not collimated and is not transmitted to the imager, but instead, is wasted and decreases the efficiency of transmitting light from the light source to the imager. Further, since imagers are increasingly proportioned to have a 16x9 size ratio, conventional integrators are likewise increasingly proportioned to have integrator inputs of a similar cross-sectional shape and 16x9 size ratio. However, a tapered integrator 200 was developed to utilize more light emitted from conventional light sources. As shown in Prior Art Figure 2, a tapered integrator 200 comprises a substantially rectangular (approximating a square) tapered integrator input face 202 integrally connected to a substantially rectangular tapered integrator output face 204 generally having a 16x9 size ratio. When a conventional input beam spot 100 tightly encircles the tapered integrator input face 202 (and where a center of the tapered integrator input face 202 is substantially aligned with the intersection of horizontal axis X and vertical axis Y of the conventional input beam spot 100), the tapered integrator 200 collects and collimates more light than the conventional integrator input face 104 shown in Prior Art Figure 1 allows. However, tapered integrators 200 are substantially more expensive than the conventional integrators that are substantially constant in cross- section. Further, the tapered integrator 200 provides only a fixed anamorphic etendue.

Summary of the Invention

The invention is a system for anamorphically illuminating a display system comprising a light beam spot shaper adapted to receive light from a light source and transmit the light as a shaped light beam to an integrator input face. The invention includes the method of illuminating an imager in the display system. The method comprises the steps of generating a light beam, anamorphically shaping the light beam to define a substantially elliptical cross-section envelope, defining a substantially rectangular portion of the light beam circumscribed by the envelope, and integrating the substantially rectangular portion of the anamorphically shaped light beam.

Brief Description of the Drawings

Prior Art Figure 1 is a schematic view of a conventional input beam spot illuminating a conventional integrator input face according to the prior art;

Prior Art Figure 2 is an oblique view of a tapered integrator according to the prior art;

Figure 3 is a diagram of a system for anamorphically illuminating a display system according to an embodiment of the present invention;

Figure 4 is a diagram of an angular anamorphic illumination system according to an embodiment of the present invention;

Figure 5 is a schematic of an angular input beam spot of the angular anamorphic illumination system of Figure 4; Figure 6 is a schematic of an angular imager of the angular anamorphic illumination system of Figure 4;

Figure 7 is a diagram of an aligned anamorphic illumination system according to an embodiment of the present invention; Figure 8 is a schematic of an aligned input beam spot of the aligned anamorphic illumination system of Figure 7;

Figure 9 is a schematic of an aligned imager of the angular anamorphic illumination system of Figure 7; and Figure 10 is a diagram of a method of anamorphically illuminating a display system according to an embodiment of the present invention.

Detailed Description of the Invention

A system for anamorphically illuminating a display system according to an embodiment of the present invention is shown in Figure 3. In this embodiment, an unaltered light beam 300 is first emitted from a light source 302 and subsequently transmitted to a light beam spot shaper 304. The light source 302 provides a substantially circular light beam spot (not shown) to the light beam spot shaper 304 (substantially similar to the light beam spot of Prior Art Figure 1). The light beam spot shaper 304 manipulates the light passing therethrough so that light exits the light beam spot shaper 304 in the form of a shaped light beam 306. The shaped light beam 306 has a shape that produces a shaped light beam spot (not shown) generally complementary to the shape of an imager 308, where the complementary shape substantially maximizes light transmission while illuminating substantially the entire area of the imager 308. To accomplish this, the shaped light beam spot produced by the shaped light beam 306 emitted from the light beam spot shaper 304 strikes substantially the entire face of an integrator input face of an integrator 310 (substantially similar to the conventional integrator input face 104 of Prior Art Figure 1). The integrator 310 is substantially similar to conventional integrators that are shaped to transmit light complementary in shape and etendue to the shape and etendue of an associated imager and associated projection optics (not shown). Therefore, the integrator 310 subsequently transmits the shaped light beam 306 to the imager 308 associated with the integrator 310, resulting in efficient light transmission. The light transmission efficiency is at least in part due to the closely matched etendue of the light beam spot shaper 304, the integrator 310, and the imager 308. It will be appreciated that in some embodiments, the light beam spot shaper 304 can manipulate the unaltered light beam 300 into the shaped light beam 306 using one or more spherical lenses, aspherical lenses, cylindrical lenses, Fresnel lenses, pairs of anamorphic prisms, or any combination thereof.

Another system for anamorphically illuminating a display system according to another embodiment of the present invention is shown in Figure 4. Angular anamorphic illumination system 400 comprises a light source 402 that emits an unaltered light beam 404 to an angular light beam spot shaper 406. The angular light beam spot shaper 406 receives the unaltered light beam 404 and manipulates the light using one or more spherical lenses, aspherical lenses, cylindrical lenses, Fresnel lenses, pairs of anamorphic prisms, or any combination thereof. The manipulated light exits the angular light beam spot shaper 406 as a shaped light beam 408 having a shape that provides an angular input beam spot 410 to an integrator input face 412 of an integrator 414. The integrator input face 412 is shown in Figure 5 and is substantially similar to conventional integrator input face 104. The shaped light beam 408 is received by the integrator 414 and subsequently transmitted to an angular imager 416 (discussed infra).

As shown in Figure 5, shaped light beam 408 is shaped so that the angular input beam spot 410 is generally elliptical and is proportioned to generally elliptically encircle the integrator input face 412 while illuminating substantially all of the integrator input face 412 and while providing an angular offset θ (discussed infra). The angular input beam spot 410 is represented as a substantially elliptical uncrosshatched area surrounded by a dark area 418 (shown as crosshatched) that is not illuminated by the angular input beam spot 410. (Substantially and generally elliptical shapes are intended to include shapes where the sum of the distances for an individual peripheral point to the two foci of an ellipse is +/- 15% of the fixed sum of the distances of a true ellipse peripheral point to the two foci.) The angular input beam spot 410 has a horizontal axis X and a vertical axis Y while the integrator input face 412 has a horizontal axis X' and a vertical axis Y'. The horizontal axis X is aligned with the major axis of the ellipse while the vertical axis Y is aligned with the minor axis of the ellipse. Similarly, the horizontal axis X' is centered and aligned with the longest length of the integrator input face 412 while the vertical axis Y' is centered and aligned with the shortest length of the integrator input face 412. As illustrated, the coordinate systems X,Y and X',Y' are aligned at their origins but, as a whole, the coordinate systems X,Y and X', Y' are angularly offset from each other by an angular offset, denoted as θ.

Referring now to Figure 6, angular imager 416 is a digital micromirror device comprising a plurality of mirrors 420, each being rotatable along an angular hinge axis 422. Each mirror 420 is substantially aligned so that the direction of rotation of the mirrors 420 is substantially parallel to a horizontal axis X" while each angular hinge axis 422 is substantially parallel to a vertical axis Y". In this embodiment, the X,Y axes of the angular input beam spot 410 are rotated by the angular offset θ relative to the X'Y' axes of the integrator 414, thereby more closely aligning a major axis (not shown) of the shaped light beam 408 (that is aligned with the X axis of the angular input beam spot 410) with the horizontal axis X". While the major axis of the shaped light beam 408 is not fully parallel to the horizontal axis X" in this embodiment, other embodiments of the present invention can provide that the major axis of the shaped light beam 408 be parallel to the horizontal axis X". Still further, other embodiments of the present invention can provide that the angular offset θ be greater or less than the angular offset shown in Figure 5, resulting in a varying degrees of angular alignment between the major axis of the shaped light beam 408 (and the X axis of the angular input beam spot 410) and the horizontal axis X". It will be appreciated that the angular offset θ can be altered by altering the angular position of the optical components of the angular light beam spot shaper 406 with respect to the integrator input face 412.

Another system for anamorphically illuminating a display system according to another embodiment of the present invention is shown in Figure 7. Aligned anamorphic illumination system 500 comprises a light source 502 that emits an unaltered light beam 504 to an aligned light beam spot shaper 506. The aligned light beam spot shaper 506 receives the unaltered light beam 504 and manipulates the light using one or more spherical lenses, aspherical lenses, cylindrical lenses, Fresnel lenses, pairs of anamorphic prisms, or any combination thereof. The manipulated light exits the aligned light beam spot shaper 506 as a shaped light beam 508 having a shape that provides an aligned input beam spot 510 to an integrator input face 512 (substantially similar to conventional integrator input face 104) of an integrator 514. The shaped light beam 508 is received by the integrator 514 and subsequently transmitted to an aligned imager 516 (discussed infra). As shown in Figure 8, shaped light beam 508 is shaped so that the aligned input beam spot 510 is generally elliptical and is proportioned to generally circumscribe the integrator input face 512 while also illuminating substantially all of the integrator input face 512. The aligned input beam spot 510 is represented as a substantially elliptical uncrosshatched area surrounded by a dark area 518 (shown as crosshatched) that is not illuminated by the aligned input beam spot 510. The aligned input beam spot 510 has a horizontal axis X and a vertical axis Y while the integrator input face 512 has a horizontal axis X' and a vertical axis Y'. The horizontal axis X is aligned with the major axis of the ellipse while the vertical axis Y is aligned with the minor axis of the ellipse. Similarly, the horizontal axis X' is centered and aligned with the longest length of the integrator input face 512 while the vertical axis Y' is centered and aligned with the shortest length of the integrator input face 512. As illustrated, the coordinate systems X,Y and X', Y' aligned at their origins but and are generally collocated without an angular offset.

Referring now to Figure 9, the aligned imager 516 is a digital micromirror device comprising a plurality of mirrors 520, each being rotatable an aligned hinge axis 522. Each mirror 520 is substantially aligned so that the direction of rotation of the mirrors 520 is substantially parallel to a horizontal axis X'" while each aligned hinge axis 522 is substantially parallel to a vertical axis Y'". In this embodiment, the X,Y axes of the aligned input beam spot 510 are generally aligned parallel to the X" ',Y'" axes, respectively. However, other embodiments of the present invention can provide that the major axis of the shaped light beam 508 (and the X axis) not be parallel to the horizontal axis X'". In other embodiments, angular rotation of the X axis with respect to the X'" axis can result in a varying degrees of angular alignment between the major axis of the shaped light beam 508 (and the X axis of the angular input beam spot 410) and the horizontal axis X'". It will be appreciated that the angular offset of other embodiments can be obtained by altering the angular position of the optical components of the aligned light beam spot shaper 506 with respect to the integrator input face 512.

Referring now to Figure 10, a method of anamorphically illuminating a display system is shown. According to an embodiment of the present invention, a display system can be anamorphically illuminated by emitting unaltered light in a first step 600, receiving the unaltered light with a light beam spot shaper in a second step 602, emitting a shaped light beam from the light beam spot shaper in a third step 604, and receiving the shaped light beam with an integrator in a fourth step 606.

Other methods of practicing the invention can include the steps of generating a light beam, anamorphically shaping the light beam, and integrating a portion of the anamorphically shaped light beam. Additionally, the methods can include the step of shaping the light beam to (1) define an envelope having a curved cross-section that has a major axis and a minor axis or (2) define an envelope having a substantially elliptical cross-section. The methods can further include the step of integrating a substantially rectangular portion or substantially quadrilateral portion of the anamorphically shaped light beam, wherein the substantially rectangular portion or substantially quadrilateral portion has a cross section that has a major axis and a minor axis. Along with the integrating step, the methods can use the step of shaping the light beam to define an envelope having a curved cross-section and the step of circumscribing the substantially rectangular or substantially quadrilateral portion with the envelope. It should be pointed out that the expression "anamorphically" in this specification is intended to relate to an intentional distortion by unequal magnification along perpendicular axes of an image or different magnifications in two different directions. Further, the expressions "substantially rectangular" and "substantially quadrilateral" are intended to include shapes where there can be some bowing or deviation in one of more sides of the shape such that individual peripheral points do not vary more than +/- 15% from a true side of a true rectangle or quadrilateral.

The foregoing illustrates some of the possibilities for practicing the invention. Many other embodiments are possible within the scope and spirit of the invention. It is, therefore, intended that the foregoing description be regarded as illustrative rather than limiting, and that the scope of the invention is given by the appended claims together with their full range of equivalents.

Claims

1. A system for anamorphically illuminating a display system, comprising: a light beam spot shaper adapted to receive light from a light source and transmit the light as a shaped light beam to an integrator input face.

2. The system according to claim 1, wherein the shaped light beam illuminates the integrator input face with an input beam spot.

3. The system according to claim 2, wherein the input beam spot is substantially elliptically shaped.

4. The system according to claim 2, wherein the input beam spot substantially circumscribes the integrator input face.

5. The system according to claim 2, wherein the input beam spot is substantially shaped as an ellipse and a major axis of the ellipse is angularly offset from a horizontal axis of the integrator input face.

6. The system according to claim 5, wherein the angular offset causes improved alignment between the major axis of the ellipse and a rotation axis of a mirror of a digital micromirror device mirror.

7. The system according to claim 1, wherein the light beam spot shaper comprises a spherical lens.

8. The system according to claim 1, wherein the light beam spot shaper comprises an aspherical lens.

9. The system according to claim 1, wherein the light beam spot shaper comprises a cylindrical lens.

10. The system according to claim 1, wherein the light beam spot shaper comprises a Fresnel lens.

11. The system according to claim 1, wherein the light beam spot shaper comprises a pair of anamorphic prisms.

12. A method of illuminating an imager, comprising the steps of: generating a light beam; anamorphically shaping said light beam; and, integrating a portion of said anamorphically shaped light beam.

13. The method of claim 12, comprising the step of shaping said light beam to define an envelope having a curved cross-section having a major axis and a minor axis.

14. The method of claim 12, comprising the step of shaping said light beam to define an envelope having a substantially elliptical cross-section.

15. The method of claim 12, comprising the step of integrating a substantially rectangular portion of said anamorphically shaped light beam, said substantially rectangular portion having a cross section having a major axis and a minor axis.

16. The method of claim 12, comprising the step of integrating a substantially quadrilateral portion of said anamorphically shaped light beam, said substantially quadrilateral portion having a cross section having a major axis and a minor axis.

17. The method of claim 15, comprising the steps of: shaping said light beam to define an envelope having a curved cross-section; and, circumscribing said substantially rectangular portion with said envelope.

18. The method of claim 16, comprising the steps of: shaping said light beam to define an envelope having a curved cross-section; and, circumscribing said substantially quadrilateral portion with said envelope.

19. The method of claim 12, comprising the steps of: shaping said light beam to define a substantially elliptical cross-section envelope; defining a substantially rectangular portion of said light beam circumscribed by said envelope; and integrating said substantially rectangular portion of said light beam circumscribed by said envelope.