Electro-optical device

• US 5,337,171 A
• Filed: 01/16/1992
• Issued: 08/09/1994
• Est. Priority Date: 01/17/1991
• Status: Expired due to Term

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Mase, Akira, Yamazaki, Shunpei
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/821,573
• Time in Patent Office: 936 Days
• Field of Search: 359/56, 359/54, 359/53, 359/100, 359/87, 359/93, 359/84, 359/85, 359/41, 340/784, 340/793, 345/89, 345/93, 345/88, 345/97, 345/99, 345/102
• US Class Current: 349/74
• CPC Class Codes: G02F 1/1347 Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells
• CPC Class Codes: G02F 2203/30 Gray scale
• CPC Class Codes: G09G 2300/0823 used to establish symmetry in driving, e.g. with polarity inversion
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 3/002 to project the image of a two-dimensional display, such as an array of light emitting or modulating elements or a CRT
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/2025 the sub-frames having all the same time duration
• CPC Class Codes: G09G 3/2074 using sub-pixels
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/364 with use of subpixels
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3651 using multistable liquid crystals, e.g. ferroelectric liquid crystals
• CPC Class Codes: H04N 5/7441 the modulator being an array of liquid crystal cells
• CPC Class Codes: H04N 9/3105 for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators simultaneous projection in colour photography G03B33/10; beam splitting or combining systems per se G02B27/10
• CPC Class Codes: H04N 9/3126 for spatial light modulators in series

Abstract

An electro-optical apparatus comprising a pair of first and second devices, which are provided in an optical path extending from a light source and a screen for outputting a picture image thereon, the first and second devices each including a pair of first and second substrates each having electrodes and leads formed thereon, which sandwich therebetween an electro-optical modulating layer (comprising for example a liquid crystal composition) and a means for orienting the liquid crystal composition at least in an initial stage. The light transmission factor of the second device changes with time rotationally in the ratios of approximately 2⁰ to 2¹ to 2² to . . . to 2ⁿ (n is an arbitrary natural number). Thus, it is possible to realize tonal display, reduce the overall weight of the apparatus and improve the yield.

Claims

1. An electro-optical device comprising:

a first electro-optical panel comprising a pair of substrates, an electro-optical modulating layer provided therebetween, and means for applying an electric field to individually control pixel elements defined in said layer;

a second electro-optical panel for supplying said first panel with light at a variable intensity level, said second panel comprising a pair of substrates, an electro-optical modulating layer provided therebetween, and means for applying an electric field to said layer of said second panel; and

control means for varying the intensity of light transmitted by said second electro-optical panel in a repeating cycle;

wherein said second panel can transmit light incident on one of said substrates of said second panel and said first panel is provided on the side of said second panel opposite to the side of said one of said substrates.

2. The device of claim 1 wherein said first panel comprises pixels arranged in a matrix and the light transmitted by said second panel can be incident on said pixels.

3. The device of claim 1 wherein said electro-optical modulating layer of said first panel comprises a ferroelectric liquid crystal.

4. The device of claim 1 wherein said layer of said second panel comprises a ferroelectric liquid crystal.

5. The device of claim 1 wherein said layer of said second panel comprises a polymer resin and a liquid crystal selected from the group consisting of a nematic liquid crystal, a cholesteric liquid crystal, and a smectic liquid crystal.

6. The device of claim 1 wherein said electric field applying means of said first panel comprises a plurality of electrodes provided on one of said substrates of said first panel in the form of a matrix, each electrode operatively connected with a complementary p-channel transistor and n-channel transistor pair.

7. The device of claim 1 wherein said first and second panels are provided between a light source and a screen.

8. The device of claim 1 further comprising means for synchronously controlling the pixel elements of the first electro-optical panel in conjunction with said light intensity varying cycle to transmit a selected total intensity of light through each said pixel element for the cycle.

9. The device of claim 8 further comprising color varying means for selectively changing the color of light supplied to said first panel by said second panel in a repeating cycle to produce time-sequential color transmissions.

10. The device of claim 9 wherein the color varying means includes a means for providing red, green, and blue colors in sequence and wherein the control means includes speed determining means for controlling the time-sequential color transmissions and selective intensity transmissions within said color transmissions through the first panel at a speed such that an apparent color picture image is formed thereby when the transmission through the first panel is viewed with human persistence of vision.

11. An electro-optical device comprising:

a first electro-optical panel comprising a pair of substrates, an electro-optical modulating layer provided therebetween and means for applying an electric field to said layer;

a second electro-optical panel comprising a pair of substrates, an electro-optical modulating layer provided therebetween, and a plurality of electrode strips for applying an electric field to said layer of said second panel; and

brightness level cycling means for cyclically applying an electric potential to a series of different predetermined numbers of said strips to cyclically vary a light transmission of said second panel;

wherein said first panel and said second panel are provided between a light source and a viewing position for viewing said device.

12. The device of claim 11 wherein said first panel comprises pixels arranged in a matrix and light transmitted by said second panel can be incident on said pixels.

13. The device of claim 11 wherein said light transmission can be varied with time rotationally at a ratio 2⁰ :

2¹ ;

2² ;

. . . ;

2ⁿ where n is a natural number.

14. The device of claim 11 wherein said layers of said first panel and said second panel comprise ferroelectric liquid crystals, respectively.

15. An electro-optical device comprising:

a first electro-optical panel comprising a pair of substrates, an electro-optical modulating layer provided therebetween, and means for applying an electric field to said layer;

a second electro-optical panel adjacent to said first panel, comprising a pair of substrates, an electro-optical modulating layer provided therebetween, and an electrode means for selectively applying an electric field to different regions of said layer; and

brightness control means connected to said second panel for controlling said electrode means to vary the intensity of light passing through said second panel in a repeating cycle, using both spatial and temporal variation of the field applied to said second panel.

16. The device of claim 15 wherein the brightness control means includes means for selectively activating different fractions of a total number of electrodes of the second panel, so that different spatial fractions of a surface area of said second panel are sequentially activated in a temporally repeated cycle.

17. A television receiver for projecting a visual image on a screen comprising:

a first electro-optical panel comprising a pair of substrates, an electro-optical modulating layer provided therebetween and means for applying an electric field to individually control picture elements defined in said layer;

a second electro-optical panel comprising a pair of substrates, an electro-optical modulating layer provided therebetween, and means for applying an electric field to said layer of said second panel to selectively vary intensity of light transmitted through said second panel;

control means for varying the intensity of light transmitted by said second electro-optical panel in a repeating cycle; and

means for synchronously controlling the pixel elements of the first electro-optical panel in conjunction with said light intensity varying cycle to transmit a selected total intensity of light through each said pixel element for the cycle;

wherein said first panel and said second panel are provided between a light source and said screen on a path of light emitted from said light source.

18. The receiver of claim 17 further comprising color varying means for selectively changing the color of light supplied to said first panel by said second panel in a repeating cycle to produce time-sequential color transmissions.

19. The receiver of claim 18 wherein the color varying means includes a means for providing red, green, and blue colors in sequence and wherein the control means includes speed determining means for controlling the time-sequential color transmissions and selective intensity transmissions within said color transmissions through the first panel at a speed such that an apparent color picture image is formed thereby when the transmission through the first panel is viewed with human persistence of vision.

20. An electro-optical device comprising:

first and second electro-optical panels, each comprising a pair of substrates, an electro-optical modulating layer provided therebetween, and means for applying an electric field to said layer;

control means for varying the intensity of light transmitted by said second electro-optical panel in a repeating cycle; and

means for synchronously controlling the pixel elements of the first electro-optical panel in conjunction with said light intensity varying cycle to transmit a selected total intensity of light through each said pixel element for the cycle.

21. The device of claim 20 further comprising color varying means for selectively changing the color of light supplied to said first panel by said second panel in a repeating cycle to produce time-sequential color transmissions.

22. The device of claim 21 wherein the color varying means includes a means for providing red, green, and blue colors in sequence and wherein the control means includes speed determining means for controlling the time-sequential color transmissions and selective intensity transmissions within said color transmissions through the first panel at a speed such that an apparent color picture image is formed thereby when the transmission through the first panel is viewed with human persistence of vision.