Video projector

• US 4,936,656 A
• Filed: 03/18/1988
• Issued: 06/26/1990
• Est. Priority Date: 03/18/1987
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Takubo, Yoneharu, Takeda, Mamoru, Miyatake, Yoshito, Yamashita, Ichiro
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): Mai, Huy K.
• Application Number:
  US07/168,318
• Time in Patent Office: 830 Days
• Field of Search: 350/333, 350/334, 350/345, 350/335, 350/338, 353/31, 353/34, 353/37, 353/49, 340/784
• US Class Current: 349/8
• CPC Class Codes: G02F 1/136213 Storage capacitors associated with the pixel electrode
• CPC Class Codes: G02F 1/13624 having more than one switching element per pixel
• CPC Class Codes: H04N 5/7441 the modulator being an array of liquid crystal cells

Abstract

A video projector utilizes a reflective liquid crystal light valve of the active matrix system and a polarizing beam splitter. An active matrix array circuit of the light valve has pixel electrodes arranged in a matrix mattern. The pixel electrodes each has a reflective surface for reflecting a light beam and protects corresponding switch elements from the light beam. There are provided at least two switch elements for each of the pixel electrodes so as to enhance the redundancy of the array circuit. Further, each pixel electrode is provided with a suitable additional capacitance.

Claims

1. A video projector comprising:

a reflective type liquid crystal light valve for reflecting a light beam being incident thereon while modulating the polarization of the light beam according to a video signal;

a light source for generating a light beam; and

an optical means for linearly polarizing the light beam from the light source, and for leading the linearly polarized light beam to the light valve, and for projecting the modulated light beam reflected from the light valve onto a screen to form a visible image on the screen,

wherein the light valve comprises;

a transparent first substrate having on a surface thereof a transparent electrode;

a second substrate having an active matrix array circuit on a surface thereof opposing the transparent electrode; and

a liquid crystal layer interposed between the first and second substrate;

wherein said active matrix array circuit includes;

a plurality of scanning lines for supplying a control signal;

a plurality of signal lines arranged to intersect the scanning lines for supplying the video signal;

a plurality of pixel electrodes opposing the transparent electrode and being arranged in a matrix to correspond to respective intersecting points of the scanning and signal lines; and

a plurality of switching elements for applying the video signal on the signal lines to the pixel electrodes selectively according to the control signal on the scanning lines, the pixel electrodes each having on a surface opposing the transparent electrode a reflective surface for reflecting the light beam being incident thereon from the first substrate side of the light valve and covering the switching elements so that the incident light beam does not reach the switching elements, each of the pixel electrodes being connected to at least two of the switching elements which are respectively controlled by at least two of the scanning lines which are different from each other, and

wherein a capacitance is formed between each of the pixel electrodes and one of the plurality of scanning lines which is different from the scanning lines for controlling the at least two switching elements connected to the each pixel electrode.

2. A video projector as in claim 1, wherein, if each of the plurality of scanning lines is designate by a sequential number n in a sequential order thereof, then each of the pixel electrodes disposed between an (n-1)-th scanning line and an n-th scanning line is connected to two switching elements which are respectively controlled by the (n-1)-th scanning line and the n-th scanning line, and the capacitance connected to the each pixel electrode is connected to an (n-2)-th scanning line.

3. A video projector as in claim 1, wherein, if each of the plurality of scanning lines is designate by a sequential number n in a sequential order thereof, then each of the pixel electrodes disposed between an (n-1)-th scanning line and an n-th scanning line is connected to two switching elements which are respectively controlled by the (n-2)-th scanning line and the n-th scanning line, and the capacitance connected to the each pixel electrode is connected to an (n-1)-th scanning line.

4. A video projector as in claim 1, wherein each of the at least two switching elements connected to each of the pixel electrodes has on each of its terminal portions an area to be cut off, when defective, by laser trimming so as to be separated from the array circuit.

5. A video projector as in claim 4, wherein the second substrate is transparent at a wave length of a laser beam used for the laser trimming.

6. A video projection comprising:

a plurality of reflective type liquid crystal light valves each for reflecting a light beam being incident thereon while modulating the polarization of the light beam according to a video signal;

a light source for generating a light beam; and

an optical means for splitting the light beam from the light source into a plurality of light beams having different wave lengths from one another, and for linearly polarizing the split light beams, and for leading the linearly polarized light beams respectively to the plurality of light valves, and for projecting the modulated light beams from the light valves onto a screen to form a visible image on the screen;

wherein each of the light valves comprises;

a transparent first substrate having on a surface thereof a transparent electrode;

a second substrate having an active matrix array circuit on a surface thereof opposing the transparent electrode; and

a liquid crystal layer interposed between the first and second substrates,

wherein said active matrix array circuit includes;

a plurality of scanning lines for supplying a control signal;

a plurality of signal lines arranged to intersect the scanning lines for supplying the video signal;

a plurality of pixel electrodes opposing the transparent electrode and being arranged in a matrix to correspond to respective intersecting points of the scanning and signal lines; and

a plurality of switching elements for applying the video signal on the signal lines to the pixel electrodes selectively according to the control signal on the scanning lines, the pixel electrodes each having on a surface opposing the transparent electrode a reflective surface for reflecting the light beam being incident thereon from the first substrate side of the light valve and covering the switching elements so that the incident light beam does not reach the switching elements, each of the pixel electrodes being connected to at least two of the switching elements which are respectively controlled by at least two of the scanning lines which are different from each other, and

wherein a capacitance is formed between each of the pixel electrodes and one of the plurality of scanning lines which is different from the scanning lines for controlling the at least two switching elements connected to the each pixel electrode.

7. A video projector as in claim 6, wherein, if each of the plurality of scanning lines is designated by a sequential number n in a sequential order thereof, then each of the pixel electrodes disposed between an (n-1)-th scanning line and an n-th scanning line is connected to two switching elements which are respectively controlled by the (n-1)-th scanning line and the n-th scanning line, and the capacitance connected to the each pixel electrode is connected to an (n-2)-th scanning line.

8. A video projector as in claim 6, wherein, if each of the plurality of scanning lines is designated by a sequential number n in a sequential order thereof, then each of the pixel electrodes disposed between an (n-1)-th scanning line and an n-th scanning lines is connected to two switching elements which are respectively controlled by an (n-2)-th scanning line and the n-th scanning line, and the capacitance connected to the each pixel electrode is connected to the (n-1)-th scanning line.

9. A video projection as is claim 6, wherein each of the at least two switching elements connected to each of the pixel electrodes has on each of its terminal portions as area to be cut off, when defective, by laser trimming so as to be separated from the array circuit.

10. A video projector as in claim 9, wherein the second substrate is transparent at a wave length of a laser beam used for the laser trimming.

11. A reflective type liquid crystal light valve for reflecting a light beam being incident thereon while modulating the polarization of the light beam according to a modulation signal, comprising:

a transparent first substrate having on a surface thereof a transparent electrode;

a second substrate having an active matrix array circuit on a surface thereof opposing the transparent electrode; and

a liquid crystal layer interposed between the first and second substrate;

wherein said active matrix array circuit includes;

a plurality of scanning lines for supplying a control signal;

a plurality of signal lines arranged to intersect the scanning lines for supplying the modulation signal;

a plurality of pixel electrodes opposing the transparent electrode and being arranged in a matrix to correspond to respective intersecting points of the scanning and signal lines; and

a plurality of switching elements for applying the modulation signal on the signal lines to the pixel electrodes selectively according to the control signal on the scanning lines, the pixel electrodes each having on a surface opposing the transparent electrode a reflective surface for reflecting the light beam being incident thereon from the first substrate side of the light valve and covering the switching elements so that the incident light beam does not reach the switching elements, each of the pixel electrodes being connected to at least two of the switching elements which are respectively controlled by at least two of the scanning lines which are different from each other, and

wherein a capacitance is formed between each of the pixel electrodes and one of the plurality of scanning lines which is different from the scanning lines for controlling the at least two switching elements connected to the each pixel electrode.

12. A light valve as in claim 11, wherein, if each of the plurality of scanning lines is designated by a sequential number n in a sequential order thereof, then each of the pixel electrodes disposed between an (n-1)-th scanning line and an n-th scanning line is connected to two switching elements which are respectively controlled by the (n-1)-th scanning line and the n-th scanning line, and the capacitance connected to the each pixel electrode is connected to an (n-1)-th scanning line.

13. A light valve as in claim 11, wherein, if each of the plurality of scanning lines is designated by a sequential number n in a sequential order thereof, then each of the pixel electrodes disposed between an (n-1)-th scanning line and an n-th scanning line is connected to two switching elements which are respectively controlled by an (n-2)-th scanning line and the n-th scanning line, and the capacitance connected to the each pixel electrode is connected to an (n-1)-th scanning line.

14. The light valve as in claim 11, wherein each of the at least two switching elements connected to each of the pixel electrodes has on each of its terminal portions an area to be cut off, when defective, by laser trimming so as to be separated from the array circuit.

15. A light valve as in claim 14, wherein the second substrate is transparent at a wave length at a laser beam use for the laser trimming.

16. A video projection comprising:

a reflective type liquid crystal light valve for reflecting a light beam being incident thereon while modulating the polarization of the light beam according to a video signal;

a light source for generating a light beam; and

an optical means for linearly polarizing the light beam from the light source and for leading the linearly polarized light beam to the light valve, and for projecting the modulated light beam reflected from the light valve onto a screen to form a visible image on the screen,

wherein the light valve comprises;

a transparent first substrate having on a surface thereof a transparent electrode;

a second substrate having an active matrix array circuit on a surface thereof opposing the transparent electrode; and

a liquid crystal layer interposed between the first and second substrates;

wherein said active matrix array circuit includes;

a plurality of scanning lines for supply a control signal;

a plurality of signal lines arranged to intersect the scanning lines for supplying the video signal;

a plurality of pixel electrodes opposing the transparent electrode and being arranged in a matrix to correspond to respective intersecting points of the scanning and signal lines; and

a plurality of switching elements for applying the video signal on the signal lines to the pixel electrodes selectively according to the control signal on the scanning lines, the pixel electrodes each having on a surface opposing the transparent electrode a reflective surface for reflecting the light beam being incident thereon from the first substrate side of the light valve and covering the switching elements so that the incident light beam does not reach the switching elements, each of the pixel electrodes being connected to at least two of the switching elements which are respectively controlled by at least two of the scanning lines which are different from each other, and

wherein, if each of the plurality of scanning lines is designated by a sequential number n in a sequential order thereof, then each of the pixel electrodes disposed between an (n-1)-th scanning line and an n-th scanning line is connected to the two switching elements which are respectively controlled by the (n-1)-th scanning line and the n-th scanning line, and the capacitance connected to the each pixel electrode is connected to an (n-2)-th scanning line.

17. A video projection comprising:

a plurality of reflective type liquid crystal light valves each for reflecting a light beam being incident thereon while modulating the polarization of the light beam according to a video signal;

a light source for generating a light beam; and

an optical means for splitting the light beam from the light source into a plurality of light beams having different wave lengths form one another, and for linearly polarizing the split light beams, and for leading the linearly polarized light beams respectively to the plurality of light valves, and for projecting the modulated light beams from the light valves onto a screen to form a visible image on the screen;

wherein each of the light valve comprises;

a transparent first substrate having on a surface thereof a transparent electrode;

a second substrate having an active matrix array circuit on a surface thereof opposing the transparent electrode; and

a liquid crystal layer interposed between the first and second substrates,

wherein said active matrix array circuit includes;

a plurality of scanning lines for supply a control signal;

a plurality of signal lines arranged to intersect the scanning lines for supplying the video signal;

a plurality of pixel electrodes opposing the transparent electrode and being arranged in a matrix to correspond to respective intersecting points of the scanning and signal lines; and

a plurality of switching elements for applying the video signal on the signal lines to the pixel electrodes selectively according to the control signal on the scanning lines, the pixel electrodes each having on a surface opposing the transparent electrode a reflective surface for reflecting the light beam being incident thereon from the first substrate side of the light valve and covering the switching elements so that the incident light beam does not reach the switching elements, each of the pixel electrodes being connected to at least two of the switching elements which are respectively controlled by at least two of the scanning lines which are different from each other, and

wherein, if each of the plurality of scanning lines is designated by a sequential number n in a sequential order thereof, then each of the pixel electrodes disposed between an (n-1)-th scanning line and an n-th scanning line is connected to the two switching elements which are respectively controlled by the (n-2)-th scanning line and the n-th scanning line, and the capacitance connected to the each pixel electrode is connected to an (n-1)-th scanning line.

18. A reflective type liquid crystal light valve for reflecting a light beam being incident thereon while modulating the polarization of the light beam according to a modulation signal, comprising:

a transparent first substrate having on a surface thereof a transparent electrode;

a second substrate having an active matrix array circuit on a surface thereof opposing the transparent electrode; and

a liquid crystal layer interposed between the first and second substrate;

wherein said active matrix array circuit includes;

a plurality of scanning lines for supplying a control signal;

a plurality of signal lines arranged to intersect the scanning lines for supplying the modulation signal;

a plurality of pixel electrodes opposing the transparent electrode and being arranged in a matrix to correspond to respective intersecting points of the scanning and signal lines; and

a plurality of switching elements for applying the modulation signal on the signal lines to the pixel electrodes selectively according to the control signal on the scanning lines, the pixel electrodes each having on a surface opposing the transparent electrode a reflective surface for reflecting the light beam being incident thereon from the first substrate side of the light valve and covering the switching elements so that the incident light beam does not reach the switching elements, each of the pixel electrodes being connected to at least two of the switching elements which are respectively controlled by at least two of the scanning lines which are different from each other, and

wherein, if each of the plurality of scanning lines is designated by a sequential number n in a sequential order thereof, then each of the pixel electrodes disposed between an (n-1)-th scanning line and an n-th scanning line is connected to two switching elements which are respectively controlled by an (n-2)-th scanning line and the n-th scanning line, and the capacitance connected to the each pixel electrode is connected to the (n-1)-th scanning line.