Electro-optical device and method of driving the same

• US 5,414,442 A
• Filed: 06/12/1992
• Issued: 05/09/1995
• Est. Priority Date: 06/14/1991
• Status: Expired due to Term

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Hiroki, Masaaki, Mase, Akira, Takemura, Yasuhiko, Yamazaki, Shunpei
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): HARVEY, MINSUN OH
• Application Number:
  US07/897,669
• Time in Patent Office: 1,061 Days
• Field of Search: 340/784, 340/805, 340/793, 345/89, 345/148
• US Class Current: 345/89
• CPC Class Codes: G02F 1/136227 Through-hole connection of the pixel electrode to the active element through an insulation layer
• CPC Class Codes: G09G 2300/0823 used to establish symmetry in driving, e.g. with polarity inversion
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2330/04 Display protection
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3677 suitable for active matrices only
• CPC Class Codes: G09G 3/3685 Details of drivers for data electrodes
• CPC Class Codes: G09G 3/3688 suitable for active matrices only
• CPC Class Codes: G09G 5/395 Arrangements specially adapted for transferring the contents of the bit-mapped memory to the screen G09G5/399 takes precedence

Abstract

The method of fine gradation display by an electro-optical device with little influence by difference in elemental devices, is disclosed, which is an object of the present invention. In case of an active matrix electro-optical device, a visual gradation display can be carried out by digitizing an analog image signal externally supplied by means of binary notation, by temporarily storing the digital signal thus obtained, by outputting the digital signal to a circuit of next step in a proper order, and by controlling the output timing of the signal so as to output the signal to the active matrix electro-optical device, and whereby digitally controlling the time for applying voltage to a picture element.

Claims

1. A method of driving an electro-optical device comprising the steps of:

applying pulses to a signal line at intervals,

wherein said intervals are T₁ between the i-th pulse and the (i+1)-th pulse, 2^N T₁ between the (i+1)-th pulse and the (i+2)-th pulse, 2T₁ between the (i+2)-th pulse and the (i+3)-th pulse, and 2^N-i T₁ between the (i+3)-th pulse and the (i+4)-th pulse where N is a natural number, i is a natural number and T₁ is a constant period.

2. The method of claim 1 wherein said pulses are rectangular pulses.

3. The method of claim 1 where N=3.

4. A method of driving an electro-optical device comprising the step of:

outputting an j-th image signal on an active matrix electro-optical device (j+1)-th and (j+2)-tj image signals bring stored in a first in first out memory device connected to said active matrix electro-optical device during the duration of said j-th image signal on said active matrix electro-optical device where j is an arbitrary natural number and where the duration of the j-th image signal is T₁, the duration of the (j+1)-th image signal is 2^N T₁, and the duration of the (j+2)-th image signal is 2T₁, N being a natural number and T₁ being a constant period; and

outputting the (j+1)-th image to the active matrix electro-optical device, (j+2)-th and (j+3)-th image signals being stored in the first in first out memory device during the duration of said (j+1)-th image signal on the active matrix electro-optical device where the duration of the (j+3)-th image signal is 2^N-1 T₁.

5. A method of driving an electro-optical device comprising the steps of:

converting an analog image signal into digital binary signals of k digits;

outputting data D_k-2j+1 in accordance with the digital binary signal S_k-2j+1 on an active matrix electro-optical device for a period of 2^k-2j+1 T₁ with the digital binary signal S_2j-1 stored in a first in first out memory device during duration of said data D_k-2j+1 on said active matrix electro-optical device where T₁ is a constant period and k and j are integers and j<

k/2;

transferring the digital binary signal S_k-2j+2 to said first in first out memory device during said outputting step;

outputting data D_2j-1 in accordance with the digital binary signal S_2j-1 on said active matrix electro-optical device for a period of 2^2j -1 T₁ after said data D_k-2j+1 outputting step; and

outputting data D_k-2j+2 in accordance with the digital binary signal S_k-2j+2 on said active matrix electro-optical device for a period of 2^k-2j+2 T₁ after said data D_2j-1 out putting step.

6. The method of claim 5 wherein k is even.

7. The method of claim 5 wherein said electro-optical device comprises said active matrix electro-optical device, a circuit for driving said active matrix electro-optical device, said first in first out memory device connected with said circuit, and a shift driver connected with said first in first out memory device.

8. The method of claim 5 wherein each of said digital binary signals has a voltage level selected from the group consisting of a high voltage level and a low voltage level.

9. The method of claim 8 wherein said low voltage level is a zero level.

10. A method of driving an electro-optical device comprising the steps of:

converting an analog image signal into digital binary signals of k digits;

outputting data D_k-2j in accordance with the digital binary signal S_k-2j on an active matrix electro-optical device for a period of 2^k-2j T₁ with the digital binary signal S_2j stored in a first in first out memory device during duration of said data D_k-2j on said active matrix electro-optical device where T₁ is a constant period and k and j are integers and j<

k/2;

transferring the digital binary signal S_k-2j+1 to said first in first out memory device during said outputting step;

outputting data D_2j in accordance with the digital binary signal S_2j on said active matrix electro-optical device for a period of 2^2j T₁ after said data D_k-2j outputting step; and

outputting data D_k-2j+1 in accordance with the digital binary signal S_k-2j+1 on said active matrix electro-optical device for a period of 2^k-2j+1 T₁ after said data D_2j outputting step.

11. The method of claim 10 wherein k is even.

12. The method of claim 10 wherein said electro-optical device comprises said active matrix electro-optical device, a circuit for driving said active matrix electro-optical device, said first in first out memory device connected with said circuit, and a shift driver connected with said first in first out memory device.

13. The method of claim 10 wherein each of said digital binary signals has a voltage level selected from the group consisting of a high voltage level and a low voltage level.

14. The method of claim 13 wherein said low voltage level is a zero level.

15. A method of driving an electro-optical device comprising the steps of:

converting an analog image signal into digital binary signals of k digits;

storing the digital binary signal of each of said k digits into corresponding one of memory areas; and

sending the digital binary signals from said memory areas to a shift driver operatively connected with an active matrix electro-optical device so that pulses are applied to a signal line of the active matrix electro-optical device at intervals wherein said intervals are T₁ between the i-th pulse and the (i+1)-th pulse, 2^N T₁ between the (i+1)-th pulse and the (i+2)-th pulse, 2T₁ between the (i+2)-th pulse and the (i+3)-th pulse, and 2^N-1 T₁ between the (i+3)-th pulse and the (i+4)-th pulse where N is a natural number, i is a natural number and T₁ is a constant period.

16. The method of claim 15 wherein k is even.

17. The method of claim 15 wherein said electro-optical device comprises said memory areas, said active matrix electro-optical device, a circuit for driving said active matrix electro-optical device, a first in first out memory device connected with said circuit, and said shift driver connected with said first in first out memory device.