Rear projector

• US 6,233,024 B1
• Filed: 08/26/1998
• Issued: 05/15/2001
• Est. Priority Date: 08/29/1997
• Status: Expired due to Fees

• Current Assignee: JENOPTIK LDT GmbH (Rheinmetall AG)
• Original Assignee: LDT GmbH & Co. Laser-Display-Technologie KG
• Inventors: Goepfert, Frank, Hiller, Klaus
• Primary Examiner(s): Eisenzopf, Reinhard
• Assistant Examiner(s): NATNAEL, PAULOS M
• Application Number:
  US09/139,912
• Time in Patent Office: 993 Days
• Field of Search: 348/744, 348/756, 348/759, 348/781, 348/782, 348/783, 348/787, 348/788, 348/804, 349/5, 349/7, 349/67, 349/57, 353/74, 353/77-79, 359/453, 359/456, 359/460, 359/196
• US Class Current: 348/744
• CPC Class Codes: H04N 9/3129 scanning a light beam on the display screen scanning a light beam on a screen in displays other than projection devices G09G3/02; scanning systems in general G02B26/10; projectors using laser light sources in general H04N9/3161

Abstract

In a rear projector with a housing on whose front side is arranged a screen for displaying a video picture, with a brightness-modulated and color-modulated R-G-B light source for emitting a light bundle, with a deflecting device for scanning this light bundle, wherein the light bundle is deflected by the deflecting device over a total angle α with respect to vertical scanning, and with a deflecting mirror which is located in the housing and arranged at an angle δ, wherein the light bundle exiting from a real or virtual vertex of the total deflection angle α is deflected onto the screen by the deflecting mirror, the virtual or real vertex located in front of the deflecting mirror lies at a location where the smallest angle β of the light bundle to the surface of the screen during deflection is less than 20° and the angle δ is given by $\delta \le 45°-\frac{\alpha }{4}+\beta .$

Claims

1. A rear projector comprising:

a housing;

a screen arrangement on a front side of the housing for displaying a video picture;

a brightness-modulated and color-modulated R-G-B light source for emitting a light bundle;

a deflecting device for scanning said light bundle;

said deflecting device for deflecting said light bundle over a total angle α

with respect to vertical scanning;

a deflecting mirror which is located in the housing and arranged at an angle δ

;

wherein the light bundle exiting from a real or virtual vertex of the total deflection angle α

is deflected onto the screen by the deflecting mirror;

wherein the virtual or real vertex located in front of the deflecting mirror lies at a location where the smallest angle β

of the light bundle to the surface of the screen during deflection is less than 20° and

the angle δ

is given by $\mathrm{\delta <br><br>}\le <br><br>45<br><br>\mathrm{°<br><br>}-\frac{\mathrm{\alpha <br><br>}}{4}+\mathrm{\beta <br><br>};<br><br>$

and

wherein angle δ

is determined for curved mirror surfaces of the deflecting mirror between the projection surface given by the screen and the chord between the extreme points of incidence of the light bundle on the deflecting mirror during vertical scanning over the angle α

.

2. The rear projector according to claim 1, wherein the vertex is virtual and is generated by additional deflecting mirrors in the rear projector.

3. The rear projector according to claim 1, wherein a computing device by which the video picture is recalculated prior to projection with respect to distortion due to oblique projection or curvature of the deflecting mirror and by a control device which controls the deflection and/or intensity modulation of the light bundle, so that there appears on the screen in the image direction a virtually undistorted video picture which diverges from an equal distribution of lines by less than 30%, particularly less than 10%, with respect to line spacing.

4. The rear projector according to claim 1, wherein the distance of the screen from the point on the deflecting mirror on which the light bundle impinges at an angle β

is less than 10 cm and, in particular, less than 3 cm.

5. The rear projector according to claim 1, wherein the deflecting mirror is a plane mirror and a light bundle reflected at a deflection angle α

/2 in the direction of the deflecting mirror impinges vertically on the screen.

6. The rear projector according to claim 1, wherein the R-G-B light source is arranged on the base of the housing.

7. The rear projector according to claim 1, wherein the deflecting device is arranged at the base of the housing.

8. The rear projector according to claim 1, wherein the deflecting device has magnification optics that have been corrected for the tangential condition for proportional magnification of the tangent of the deflection angle.