Image display using liquid crystal display panel

• US 4,775,891 A
• Filed: 08/23/1985
• Issued: 10/04/1988
• Est. Priority Date: 08/31/1984
• Status: Expired due to Term

• Current Assignee: Casio Computer Company Limited
• Original Assignee: Casio Computer Company Limited
• Inventors: Usui, Minoru, Aoki, Tsuyoshi, Odake, Ryota, Kobayashi, Saburo
• Primary Examiner(s): Chin, Tommy P.
• Application Number:
  US06/769,002
• Time in Patent Office: 1,138 Days
• Field of Search: 358/160, 358/166, 358/230, 358/241, 340/752, 340/753, 340/754, 340/794, 340/805, 340/784
• US Class Current: 348/572
• 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 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3674 Details of drivers for scan electrodes
• CPC Class Codes: G09G 3/3685 Details of drivers for data electrodes
• CPC Class Codes: H04N 3/127 using liquid crystals

Abstract

An image display apparatus having an A/D converter which samples a television signal a plurality of times in each horizontal effective display period and converts the sampled signal into digital data, and a gradation signal generator combines gradation signals produced in a plurality of horizontal effective display periods according to the digital data to produce a new gradation signal. An image display panel is driven for display according to the new gradation signal.

Claims

1. An image display apparatus, comprising:

a liquid crystal display panel including common electrodes and segment electrodes arranged in the form of a matrix, including means for selecting each common electrode for a predetermined period;

analog-to-digital (A/D) conversion means for sampling a video signal, for converting the video signal into corresponding n-bit digital data, and for outputting the digital data;

means responsive to the video signal for outputting a data control signal whose level changes between a first level and a second level during said predetermined period, and for supplying the data control signal to said A/D conversion means;

said A/D conversion means including data control means responsive to said data control signal for varying the n-bit digital data output from said A/D conversion means according to a predetermined function to obtain (n-1)-bit digital data, said function depending on the level of said data control signal and certain bits of said n-bit digital data;

means for generating a gradation signal capable of assuming one of (2ⁿ -1) levels during said predetermined period in response to the (n-1)-bit digital data output from said A/D conversion means when the level of said data control signal assumes both said first level and said second level; and

means coupled to said generating means for driving said liquid crystal display panel in accordance with said gradation signal.

2. The image display apparatus according to claim 1, wherein

said data control means includes logic means coupled to said converting means, for receiving said n-bit digital data and said data control signal, and including means for outputting

the upper (n-1) bits of said n-bit digital data when the level of said data control signal is at either of said first or said second level and a least significant bit of said n-bit digital data is "O",

the upper (n-1) bits of said n-bit digital data when the level of said data control signal is at said first level and the least significant bit of said n-bit digital data is "1", and

the upper (n-1) bits obtained by adding "1" to the (n-1)th bit or to the n-th bit when the level of said data control signal is at said second level and the least significant bit of said n-bit digital data is "1".

3. The image display apparatus according to claim 2, wherein said outputting means outputs the upper (n-1) bits of said n-bit digital data when the level of said data control signal is at either of said first or said second level and each of said n-bit data is "1".

4. The image display apparatus according to claim 1, wherein said A/D conversion means includes a reference voltage source for converting the video signal, and means for switching the level of said reference voltage source in accordance with the level of said data control signal.

5. An image display apparatus, comprising:

a liquid crystal display panel including common electrodes and segment electrodes arranged in the form of a matrix, including means for selecting each common electrode for a predetermined period;

analog-to-digital (A/D) conversion means for sampling a video signal, for converting the video signal into corresponding n-bit digital data, and for outputting the digital data;

means responsive to the video signal for outputting a data control signal whose level changes between a first level and a second level in accordance with at least each of two fields of the video signal, and for supplying the data control signal to said A/D conversion means;

said A/D conversion means including data control means responsive to said data control signal for varying the n-bit digital data output from said A/D conversion means according to a predetermined function to obtain (n-1) bit digital data, said function depending on the level of said data control signal and certain bits of said n-bit digital data;

means for generating a gradation signal capable of assuming one of (2ⁿ -1) levels during a plurality of said fields in response to the (n-1)-bit digital data output from said A/D conversion means when the level of said data control signal assumes both said first level and said second level; and

means coupled to said generating means for driving said liquid crystal display panel in accordance with said gradation signal.

6. The image display apparatus according to claim 5, wherein

said data control means includes logic means coupled to said converting means, for receiving said n-bit digital data and said data control signal, and including means for outputting

the upper (n-1) bits of said n-bit digital data when the level of said data control signal is at either of said first or said second level and a least significant bit of said n-bit digital data is "O",

the upper (n-1) bits of said n-bit digital data when the level of said data control signal is at said first level and the least significant bit of said n-bit digital data is "1", and

the upper (n-1) bits obtained by adding "1" to the (n-1)th bit or to the n-th bit when the level of said data control signal is at said second level and the least significant bit of said n-bit digital data is "1".

7. The image display apparatus according to claim 6, wherein said outputting means outputs the upper (n-1) bits of said n-bit digital data when the level of said data control signal is at either of said first or said second level and each of said n-bit data is "1".

8. The image display apparatus according to claim 5, wherein said A/D conversion means includes a reference voltage source for converting the video signal, and means for switching the level of said reference voltage source in accordance with the first and the second levels of said data control signal.