Rear-screen projection television with spatial light modulator and positionable anamorphic lens

• US 6,317,171 B1
• Filed: 09/16/1998
• Issued: 11/13/2001
• Est. Priority Date: 10/21/1997
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Dewald, Duane S.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Tran, Trang U.
• Application Number:
  US09/154,425
• Time in Patent Office: 1,154 Days
• Field of Search: 348/781, 348/742, 348/743, 348/756, 348/757, 359/822, 359/823, 359/824, 359/671, 359/668, 359/783, 359/501, 359/683
• US Class Current: 348/756
• CPC Class Codes: H04N 2005/7466 Control circuits therefor
• CPC Class Codes: H04N 5/46 for receiving on more than one standard at will deflecting circuits of multi-standard receivers H04N3/27
• CPC Class Codes: H04N 5/7458 the modulator being an array of deformable mirrors, e.g. digital micromirror device [DMD]
• CPC Class Codes: H04N 7/0122 the input and the output signals having different aspect ratios

Abstract

A television receiver (10) that has a spatial light modulator (15) and a projection lens (17a) and that projects images to a screen (18). If the aspect ratio of the image to be displayed does not match that of the spatial light modulator (15), an anamorphic lens (17b) is positioned in the optical path of the image, between the projection lens (17b) and the screen (18). In this case and in typical applications, the spatial light modulator (15) generates an image that is anamorphically squeezed in the horizontal dimension, and the anamorphic lens (17b) widens the image so that the viewer perceives a normal wide-screen image on the screen (18).

Claims

1. A projection television comprising:

a signal interface for receiving images according to a plurality of aspect ratios including a first and a second aspect ratio;

a pixel data processing unit for scaling, in at least one dimension, received images in the first aspect ratio, to fit a second aspect ratio;

a spatial light modulator for generating images to be displayed, the spatial light modulator having the second aspect ratio;

a projection lens operable to project images along an optical path from said spatial light modulator to a screen;

an anamorphic lens moveable in and out of said optical path, said anamorphic lens operable to optically adjust said image in said at least one dimension to match the first aspect ratio; and

a mechanism attached to said anamorphic lens, operable to move said anamorphic lens in and out of said optical path.

2. The television of claim 1, wherein said first and second aspect ratios differ in the horizontal dimension and wherein said anamorphic lens stretches said images in said horizontal dimension.

3. The television of claim 1, wherein said first aspect ratio is 4:

3.

4. The television of claim 1, wherein said anamorphic leans modifies images projected by the projection lens by 1.5:

1.

5. A projection optics unit for a television receiver that uses a spatial light modulator to generate images to be displayed on a screen, where the spatial light modulator has an associated aspect ratio and the images may have aspect ratios that differ in at least one dimension from that of said spatial light modulator, comprising:

a projection lens operable to project images along an optical path from said spatial light modulator to a screen;

an anamorphic lens moveable in and out of said optical path, said anamorphic lens operable to optically adjust said image in said at least one dimension, having a series of lens elements comprising;

a first lens element that is a bi-concave lens;

a second lens element spaced from said first lens element and having a first surface that is convex;

a third lens element having a first surface that is convex, said second lens and said third lens formic a doublet;

a fourth lens element spaced from said third lens element to define an air space therebetween, and having a first surface that is planar; and

a fifth lens element having a first surface that is concave, said fourth lens element and said fifth lens element forming a doublet; and

a mechanism attached to said anamorphic lens, operable to move said anamorphic lens in and out of said optical path.

6. The television of claim 5, wherein said air space between said third lens element and said fourth lens element may be adjusted to accommodate said projection lens having a throw ratio substantially in the range of 7:

1 to 3;

1.

8. The method of claim 6, wherein said aspect ratios differ in the horizontal dimension and wherein said anamorphic lens stretches said images in said horizontal dimension.

9. The method of claim 6, wherein said spatial light modulator has a 4:

3 aspect ratio.

10. The method of claim 6, wherein said anamorphic lens modifies said aspect ratio of said spatial light modulator by 1.5:

1.

7. A method of displaying images with different aspect ratios, using a television receiver having a spatial light modulator and a projection lens for projecting the images to a screen, said spatial light modulator having an associated aspect ratio, and said screen and said projector having an optical path between them, comprising:

determining whether the aspect ratio of a spatial light modulator substantially matches the aspect ratio of one type of the images received by a television receiver;

responsive to said determining step determining that said aspect ratios do not substantially match in at least one dimension;

scaling the received image in at least one dimension into a squeezed image corresponding to the aspect ratio of the spatial light modulator; and

positioning an anamorphic lens in said optical path, said anamorphic lens operable to optically resize said squeezed image in said at least one dimension; and

responsive to said determining step determining that said aspect ratios substantially match, positioning the anamorphic lens out of said optical path.

11. A method of displaying images with different aspect ratios, using a television receiver having a spatial light modulator for generating the images at an associated aspect ratio, a projection lens for projecting the images to a screen along an optical path, and an anamorphic lens having a series of lens elements comprising a first lens element that is a bi-concave lens, a second lens element spaced from said first lens element and having a first surface that is convex, a third lens element having a first surface that is convex so that said second lens element and said third lens element form a doublet, a fourth lens element having a planar first surface and spaced from said third lens element to define an air space therebetween, and a fifth lens element having a first surface that is concave so that said fourth lens element and said fifth lens element form a doublet, the method comprising:

determining whether the aspect ratio of a spatial light modulator substantially matches the aspect ratio of one type of the images received by a television receiver;

if said determining step determines that said aspect ratios substantially match, positioning the anamorphic lens out of said optical path; and

if said determining step determines that said aspect ratios do not substantially match in at least one dimension, positioning an anamorphic lens in said optical path, said anamorphic lens operable to optically resize said image in said at least one dimension.

12. The method of claim 11, wherein said air space between said third lens element and said fourth lens element may be adjusted to accommodate said projection lens having a throw ratio substantially in the range of 7:

1 to 3;

1.