LCD projector

• US 6,409,350 B1
• Filed: 10/26/2000
• Issued: 06/25/2002
• Est. Priority Date: 03/06/1998
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Noguchi, Toshiyuki, Kakimoto, Yasuhiro, Kotaka, Mitsuru
• Primary Examiner(s): DOWLING, WILLIAM C
• Application Number:
  US09/623,412
• Time in Patent Office: 607 Days
• Field of Search: 353/85, 353/94, 315/225, 315/209.R
• US Class Current: 353/85
• CPC Class Codes: H04N 2005/745 Control circuits therefor
• CPC Class Codes: H04N 5/74 Projection arrangements for image reproduction, e.g. using eidophor
• CPC Class Codes: H04N 5/7441 the modulator being an array of liquid crystal cells
• CPC Class Codes: H04N 9/3102 using two-dimensional electronic spatial light modulators micromechanical modulators as such G02B26/0833; liquid crystal modulators as such G02F1/13
• CPC Class Codes: H04N 9/3155 for controlling the light source light source control per se H05B35/00 – H05B47/00; control of an illumination source for displays in general G09G3/3406
• CPC Class Codes: H04N 9/3164 using multiple light sources
• CPC Class Codes: H04N 9/3182 Colour adjustment, e.g. white balance, shading or gamut white balance per se H04N9/73; control of amplitude of colour signals H04N9/68; colour control circuits for displays in general G09G5/02, G09G3/2003, G09G3/3607
• CPC Class Codes: H04N 9/73 Colour balance circuits, e.g. white balance circuits or colour temperature control camera processing pipelines for colour balance H04N23/88

Abstract

An LCD projector (K1) comprising: a power source (20); an image data source (90) for producing an image data; a light source (30) which is able to provide different levels of power; an LCD panel (50) for modifying a light ray from the light source (30) in accordance with said image data to produce light rays of an image; a projecting lens (60) for projecting the light rays from the LCD panel (50) onto a screen (70) through enlargement; a control circuit (81) for controlling an output of the power source (20) so as to selectively set an output power: and a correcting circuit (100) for correcting an image data before being supplied to the LCD panel (50) so as to compensate the disturbance of the white balance caused by the change of the power of the light source (30).

Claims

1. An LCD projector comprising:

a power source (11, 20);

an image data input for producing an image data;

a light source (30) which is capable of emitting light with R, G, B components and to provide different levels of power;

wherein the change in output power of the power source (20) is used to change the output power of the light source (30);

a LCD panel (50) for modifying light rays from the light source (30) in accordance with said image data to produce light rays of an image;

a projecting lens (60) for projecting the light rays from the LCD panel (50) onto a screen (70) through enlargement;

a control circuit (81) for controlling an output of the power source so as to selectively set an output power;

a correcting circuit (100) for correcting image data before being supplied to the LCD panel (50) so as to compensate the disturbance of the white balance caused by the change of the power of the light source (30),

a counter (61) for counting an integrated on-state period of the light source; and

a memory (51 ) for storing the integrated on-state period of the light source, which is connected to the counter and the control circuit;

wherein the control circuit (81) changes the output of the power source (20) upon lapse of the integrated on-state period of the light source (30) stored by the memory (51) so as to keep luminance of the light source (30) constant.

2. An LCD projector as claimed in claim 1, wherein the correcting circuit (100) further corrects said image data so as to compensate the light intensity change caused by the relationship between the applied voltage and the transmissivity of the LCD panel (50).

3. An LCD projector as claimed in claim 1, wherein the correcting circuit (100) includes a plurality of look-up tables (T₁ to T_n) and a changeover switch (105) of effecting changeover of the look-up tables (T₁ to T_n).

11. An LCD projector as claimed in claim 2, wherein the correcting circuit (100) includes a plurality of look-up tables (T₁ to T_n) and a changeover switch (105) for effecting changeover of the look-up tables (T₁ to T_n).

4. An LCD projector comprising;

a power source (21);

a plurality of light sources (31) capable of emitting light with R, G, B components which are driven by the power source (21);

an LCD panel (50) for modifying an image by receiving light rays from the light sources (31);

a projecting lens (60) for projecting the image of the LCD panel (50) onto a screen through enlargement;

a control circuit (81) for controlling the power source (21) so as to turn on the light sources (31) selectively, wherein the control circuit (81) selects order of priority of the light sources (31) when the light sources (31) are turned on selectively, and wherein the control circuit (81) determines the order of priority of the light sources (31) on the basis of integrated on-state periods of the light sources (31).

5. An LCD projector as claimed in claim 4, wherein the control circuit (100) determines, in accordance with brightness of a room in which the LCD projector is installed, how many ones of the light sources (31) should be turned on.

6. An LCD projector as claimed in claim 4, wherein said power source comprises a D/A converter (110) for receiving an output from the power source (21) and for producing different voltage levels.

7. An LCD projector as claimed in claim 4, further comprising:

a correcting circuit (100) for correcting image data before being supplied to the LCD panel (50) so as to compensate the disturbance of the white balance caused by the change of the power of each of the light sources (31).

12. An LCD projector as claimed in claim 5, further comprising:

a correcting circuit (100) for correcting image data before being supplied to the LCD panel (50) so as to compensate the disturbance of the white balance caused by the change of the power of each of the light sources (31).

13. An LCD projector as claimed in claim 6, further comprising:

a correcting circuit (100) for correcting image data before being supplied to the LCD panel (50) so as to compensate the disturbance of the white balance caused by the change of the power of each of the light sources (31).

8. A method of controlling a plurality of light sources of an LCD projector so as to turn on the light sources selectively, comprising the steps of:

inputting to the LCD projector a signal on how many ones of the light sources should be turned on;

attempting to turn on all the light sources and making a decision on whether or not the number of useable ones of the light sources is not less than a predetermined number designated by the signal; and

by selecting, on the basis of the decision, by priority in increasing order of integrated on-state periods of the light sources which ones of the light sources should be used, turning off those of the light sources, whose contribution is not required to reach a desired output power.

9. A method as claimed in claim 8, wherein the signal is produced by operating a remote control unit.

10. A method as claimed in claim 8, wherein the signal is produced by a sensor detecting brightness of a room in which the LCD projector is installed.