Method for driving display device

• US 5,488,387 A
• Filed: 02/28/1994
• Issued: 01/30/1996
• Est. Priority Date: 03/07/1989
• Status: Expired due to Fees

• Current Assignee: Sharp Electronics Corporation (Hon Hai Precision Industry Co., Ltd.), Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Maeda, Hiroshi, Omori, Takuro
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): Saras, Steven J.
• Application Number:
  US08/203,617
• Time in Patent Office: 701 Days
• Field of Search: 345/147, 345/148, 345/149, 345/89, 345/99
• US Class Current: 345/89
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/2051 with use of a spatial dither pattern
• CPC Class Codes: G09G 3/2055 the pattern being varied in time
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers
• CPC Class Codes: H04N 3/127 using liquid crystals

Abstract

A frame thinning out system has been used as a driving method for a display device for creating a gradational display with several brightness levels on the screen of a liquid crystal display device and the like. This driving method creates a gradational display by setting a plurality of frame time periods, during which each of pixels on the screen of the display device are controlled for displaying an image, as one integration time period, and turning on pixels only for a number of specified frame time periods corresponding to a brightness level to be displayed, out of all frame time periods within the integration time period. In this driving method, all pixels of the display device are grouped into multiple groups, each of which is composed of a plurality of pixels contiguous to each other. The number of pixels to be turned on in each frame time period within one integration time period is selected corresponding to the specified gradation data within the same group. Further, the frame time period during which the number of pixels turned on is kept constant and is set to a period short enough such that a human being does not notice display flicker. In this way, viewing a plurality of pixels as one group over a unit image area, a gradational display without noticeable flicker can be obtained.

Claims

1. A method for driving a display device to create a gradationally toned display of at least one of a plurality of brightness levels by setting a plurality of sequential frame time periods, during which each of a plurality of pixels on a screen of the display device is controlled to display an image, as one integration time period and by turning on pixels for a number of specified frame time periods corresponding to display data of the image within the integration time period, the method comprising the steps of:

grouping the plurality of pixels of the display device into a plurality of groups, each composed of a plurality of contiguous pixels;

selecting a number of pixels to be turned on for one integration time period corresponding to specified gradation data, for each of the plurality of groups; and

setting a number of pixels to be turned on for each of the sequential frame time periods within each integration time period, such that a minimum and a maximum number of pixels turned on within each integration time period is established by at least the second sequential frame time period, for each of the plurality of brightness levels, to thereby reduce display flicker, wherein the difference between the minimum and maximum number of pixels turned on within each integration time period, at each brightness level, is, at most, one pixel.

2. A method for driving a display device according to claim 1, wherein the gradational display is created by using multiple gradation data for each frame time period, on the basis of a total of gradation data to be applied over each integration time period, spaced apart by nearly equal levels of specified gradation data in directions opposite to each other.

3. A method for driving a display device according to claim 1, wherein the gradation display is created by turning on an equal number of pixels, corresponding to the specified gradation data, for each frame time period.

4. A method for driving a display device according to claim 3, wherein the pixels to be turned on in each group are selected to include pixels in different positional locations for successive frame time periods in each integration time period.

5. A method for driving a display device according to claim 2, wherein difference between the plural gradation data is selected so as to be the minimum unit of the gradation data.

6. A method for driving a display device according to claim 2, wherein a period of variation among the plural gradation data is selected so as to be a period equal to the frame time period.

7. A gradation display apparatus comprising:

display drive means for driving a plurality of pixels on a screen of a display device to display a gradationally toned image of at least one of a plurality of gradation levels based upon input gradation data;

grouping means for grouping the plurality of pixels into a plurality of groups, each of which is composed of a plurality of contiguous pixels, and for setting a plurality of sequential frame time periods equal to an integration time period, during which each of the groups of pixels are driven to display the image based on input gradation data; and

selection means for selecting a number of pixels to be turned on for each integration time period corresponding to the input gradation data and for selecting a number of pixels to be turned on for each of the sequential frame time periods within each integration time period, such that a minimum and a maximum number of pixels turned on within each integration time period is established by at least the second sequential frame time period, for each of the plurality of gradation levels, to thus reduce display flicker, wherein the difference between the minimum and maximum number of pixels turned on within each integration time period, at each gradation level, is, at most, one pixel.

8. The gradation display apparatus of claim 7, wherein the selecting means selects an equal number of pixels to be turned on in each frame time period such that the number of pixels turned on in each frame time period remains constant.

9. The gradation display apparatus of claim 8, wherein the pixels selected to be turned on in each group are selected to include pixels in different positional locations for successive frame time periods, in each integration time period.

10. A method of producing a gradation display comprising the steps of:

(a) selecting a number of sequential frame time periods, within one integration time period, in which input gradation display data is to be displayed;

(b) grouping each of a plurality of pixels on a display, into a plurality of groups, each composed of a plurality of contiguous pixels;

(c) selecting a number of pixels in each of the plurality of groups to be turned on for each integration time period corresponding to the input gradation display data;

(d) selecting a number of pixels to be turned on for each sequential frame time period in each group, such that a minimum and a maximum number of pixels turned on within each integration time period is established by at least the second sequential frame time period, for each of the plurality of gradation levels, wherein the difference between the minimum and maximum number of pixels turned on within each integration time period, at each gradation level, is, at most, one pixel; and

(e) driving the selected number of pixels in each group, to be turned on in each of the plurality of sequential frame time periods in each integration time period, to produce a gradation display with minimal flicker.

11. The method of claim 10, wherein, in step (d), an equal number of pixels are selected to be turned on in each frame time period.

12. The method of claim 11, further comprising the step of, selecting pixels in each group, to be turned on during each successive frame time period, to include pixels in different positional locations.