Display device

• US 4,908,613 A
• Filed: 09/18/1987
• Issued: 03/13/1990
• Est. Priority Date: 09/20/1986
• Status: Expired due to Fees

• Current Assignee: Thorn EMI Plc (Universal Music Group NV)
• Original Assignee: Thorn EMI Plc (Universal Music Group NV)
• Inventors: Green, Ian M.
• Primary Examiner(s): Brigance, Gerald
• Assistant Examiner(s): Hjerpe, Richard
• Application Number:
  US07/098,169
• Time in Patent Office: 907 Days
• Field of Search: 340/718, 340/719, 340/765, 340/767, 340/771, 340/773, 340/776, 340/777, 340/784, 340/793, 350/330, 350/331 R, 350/332, 350/333
• US Class Current: 345/90
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0828 forming a digital to analog [D/A] conversion circuit
• CPC Class Codes: G09G 2330/12 Test circuits or failure detection circuits included in a display system, as permanent part thereof
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3651 using multistable liquid crystals, e.g. ferroelectric liquid crystals
• CPC Class Codes: G09G 3/3655 Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors
• CPC Class Codes: H04N 3/127 using liquid crystals

Abstract

A liquid crystal display has a matrix of pixels each with a continuously clocked counter used both as the data store and as the mechanism of grey scale generation. The grey level of each pixel is stored as the phase of the counter with respect to a reference count.

The data bus, load clock, counter clock and master phase reference are all lines which transport signals common to a large number of pixels.

The shift data line is used to propagate a bit which enables the counter load input. Each pixel circuit instructs the adjacent circuit that it is next to be loaded, by use of a clock delay. Thus pixels are loaded in sequence from data on the load bus, that data being between load clock pulses. The bistable circuit element, set from the master timing and reset from the counter, has an output which directly drives a bistable liquid crystal display device.

Claims

1. A display device for displaying a picture represented by picture-signals, the display device comprising:

a lattice of pixels for displaying the picture;

an associated counter for each pixel, each associated counter being operable for continuous counting; and

means to operate each associated counter to effect actuation of each pixel for a time period dependent upon at least the value of the picture-signal for that pixel.

2. A display device according to claim 1 wherein the display device has means to input the picture-signal for a pixel to that pixel in order to set that pixel to a state.

3. A display device according to claim 1, the picture signal for a pixel having a detectable characteristic, the display device also comprising means for producing and applying a reference signal to each pixel, the reference signal having another detectable characteristic such that an interval of time between the reception at a pixel of said detectable characteristic and the reception of said another detectable characteristic can be determined wherein the time period for said pixel corresponds to said interval of time.

4. A display device according to claim 1, the picture signal for a pixel having a detectable characteristic, wherein an associated counter has means to monitor for the presence of said detectable characteristic and means to set said pixel to a state upon detection of said detectable characteristic.

5. A display device according to claim 1, 2, 3 or 4 wherein liquid crystal cells form the lattice.

6. A method of operating a display device to display a picture represented by picture signals, the display device comprising a lattice of pixels for displaying the picture and an associated counter for each pixel, each associated counter being operable for continuous counting, the method comprising operating each associated counter to effect actuation of each pixel for a time period dependent upon at least the value of the picture-signal for that pixel.

7. A method according to claim 6, the picture signal for a pixel having a detectable characteristic, the method further comprising the steps of producing a reference signal having another detectable characteristic and of applying the reference signal to a pixel wherein the interval of time between the reception at a pixel of said detectable characteristic and the reception of said another detectable characteristic can be determined and the time period for said pixel corresponds to said interval of time.

8. A method according to claim 6, the picture signal for a pixel having a detectable characteristic wherein an associated counter monitors for the presence of said detectable characteristic and sets said pixel to a state upon detection of said detectable characteristic.

9. A method according to claim 6, comprising inputting the picture-signal for a pixel to that pixel in order to set that pixel to a state.

10. A display device for displaying a picture represented by a picture signal, the display device comprising:

a lattice of pixels for displaying the picture;

an associated counter for each pixel, each associated counter being operable for continuous counting;

and means to operate each associated counter to effect actuation of each pixel at a brightness level for the picture dependent upon at least the value of the picture-signal for that pixel.

11. A display device according to claim 10, the picture signal for a pixel having a detectable characteristic, the display device also comprising means for producing and applying a reference signal to each pixel, the reference signal having another detectable characteristic such that an interval of time between the reception at a pixel of said detectable characteristic and the reception of said another detectable characteristic can be determined wherein the brightness level of a pixel is determined by said interval of time.

12. A method of operating a display device to display a picture represented by picture-signals, the display device comprising a lattice of pixels for displaying a picture and an associated counter for each pixel each associated counter being operable for continuous counting, the method comprising operating each counter to effect actuation of each pixel at a brightness level for the picture dependent upon at least the value of the picture-signal for that pixel.

13. A method according to claim 12, the picture signal for a pixel having a detectable characteristic, the method further comprising the steps of producing a reference signal having another detectable characteristic and of applying the reference signal to a pixel wherein the interval of time between the reception at a pixel of said detectable characteristic and the reception of said another detectable characteristic can be determined and said brightness level is determined by said interval of time.