Electro-optical device and method of driving the same

• US 5,784,073 A
• Filed: 02/13/1995
• Issued: 07/21/1998
• 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): Hjerpe, Richard
• Assistant Examiner(s): CHANG, KENT WU
• Application Number:
  US08/387,234
• Time in Patent Office: 1,254 Days
• Field of Search: 345/89, 345/98, 345/100, 345/204, 345/205, 345/148, 345/149, 345/196, 345/197, 345/198, 345/517, 345/508, 345/92, 345/511, 348/790, 348/792
• US Class Current: 345/537
• 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:

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;

transferring said digital binary signal from said memory areas to a first in first out memory; and

sending the digital binary signal from said first in first out memory to a shift register operatively connected with an active matrix electro-optical device,

wherein said digital binary signal is transferred from said memory areas to said first in first out memory in such a manner that each two digits of data is paired and simultaneously transferred to said first in first out memory.

2. The method of claim 1 wherein k is even.

3. The method of claim 1 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.

4. An electro-optical device comprising:

an active matrix device having a plurality of pixels;

an A/D converter for converting an analog image data into k digits of digital data;

a gradation data memory for storing said k digits of digital data;

a first in first out memory device connected with said gradation data memory;

means for transferring said k digits of digital data from said gradation data memory into said first in first out memory device;

means for transferring said k digits of digital data to a driver circuit to generate pulses to be applied to said pixels,

wherein said k digits of digital data stored in said gradation data memory is transferred in such a manner that each two digits of data is paired and simultaneously transferred to said first in first out memory device.

5. The device of claim 4 further comprising a pair of substrates, an electrode arrangement provided on inside surfaces of said substrates, an electro-optical modulating layer provided between said substrates.

6. The device of claim 5 wherein said electro-optical modulating layer comprises a liquid crystal selected from the group consisting of a twisted nematic liquid crystal, a super twisted namatic liquid crystal, a ferroelectric liquid crystal, an anti-ferroelectric liquid crystal and a dispersion liquid crystal.

7. The device of claim 5 wherein said electrode arrangement comprises pixel electrodes provided on one of said inside surfaces and said active matrix device further comprises thin film transistors provided on said one of said inside surfaces and connected with said pixel electrodes.

8. An electro-optical device comprising:

a synchronous separation circuit for receiving and separating analog image data;

an A/D converter for converting the analog image data into digital image data;

a dual port memory for storing said digital image data;

a first in first out memory (FIFO) for receiving the digital image data transferred from said dual port memory;

a write address pointer operationally connected to said dual port memory;

a read address pointer operationally connected to said dual port memory;

a data shift register for receiving a data from said FIFO; and

a timing sequence controller for generating a timing signal and operationally connected to said synchronous separation circuit, said A/D converter, said dual port memory, said FIFO, said write address pointer, said read address pointer and said data shift register,

wherein said digital data is transferred from said dual port memory to said first in first out memory in such a manner that each two digits of data is paired and simultaneously transferred to said first in first out memory.