Coordinative detecting methods and apparatus for liquid crystal display unit and liquid crystal integral type tablet

• US 5,638,089 A
• Filed: 10/07/1994
• Issued: 06/10/1997
• Est. Priority Date: 12/24/1993
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Takemoto, Masato
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): TRAN, VUI
• Application Number:
  US08/320,194
• Time in Patent Office: 977 Days
• Field of Search: 345/87, 345/103, 345/104, 345/201
• US Class Current: 345/104
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/0441 using active external devices, e.g. active pens, for receiving changes in electrical potential transmitted by the digitiser, e.g. tablet driving signals
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

A coordinate detecting method for a liquid crystal display unit has the steps of generating a second display control signal for controlling a display provided in a display period and a non-display period on the basis of a first display control signal set such that one frame is constructed by only the display period; the display period and the non-display periods being set such that an image is displayed on a liquid crystal panel in the display period and is not displayed on the liquid crystal panel in the non-display period; storing transmitted image data to a memory in accordance with timings shown by the first display control signal; reading these stored image data from the memory in accordance with timings shown by the second display control signal; displaying the image on the liquid crystal panel by the read image data and the second display control signal; and detecting coordinates by a detecting pen in the non-display period. A coordinate detecting method and an apparatus for a liquid crystal integral type tablet is also shown.

Claims

1. A method for adding a coordinate detecting function in a liquid crystal display unit having only an image displaying function, comprising the steps of:

generating a second display control signal including a display period and a non-display period alternately on the basis of a first display control signal including only a display period for displaying a frame of imaging data, a sum of the duration of said display period and said non-display period of said second control signal being equal to the duration of said display period of said first control signal;

the display period and the non-display periods being set such that an image is displayed on a liquid crystal panel in the display period and is not displayed on said liquid crystal panel in the non-display period;

storing transmitted image data to a memory in accordance with timings shown by said display period of said first display control signal;

reading these stored image data from the memory in accordance with timings shown by said second display control signal;

displaying read out image data on said liquid crystal panel in said display period of said second display control signal; and

detecting coordinates of a coordinate indicate means in said non-display period of said second control signal.

2. The method according to claim 1, wherein said memory includes a first frame memory and a second frame memory and at the storing step, one of the first frame memory and the second frame memory stores the frame of imaging data, alternately.

3. The method according to claim 1, wherein said memory is a first-in first-out memory.

4. A coordinate detecting method in a liquid crystal integral type tablet in which an image is displayed on a liquid crystal panel and coordinates indicated by a coordinate indicate means are detected when no image is displayed on said liquid crystal panel;

the coordinate detecting method comprising the steps of;

dividing row electrodes arranged in said liquid crystal panel into a plurality of electrode groups constructed by continuous row electrode groups;

dividing a display period for displaying a frame of image data into a plurality of display periods each displaying a part of the image data on respective one of said plurality of electrode groups;

forming a non-display period for undisplaying the image on said liquid crystal panel at every interval of said plurality of display periods; and

detecting coordinates of said coordinate indicate means in said non-display period so as to detect the coordinates a plurality of times within the display period for displaying the frame of image data;

wherein a common pulse for displaying one of said electrode groups is removed after the display period corresponding to said one of said electrode groups is completed, and a common pulse for displaying next one of said electrode groups is applied prior to the display period for said next one of said electrode groups in order to drive said plurality of electrode groups by a single common driving circuit.

5. The method according to claim 4, wherein said row electrodes are divided into two groups.

6. An apparatus including a liquid crystal display unit having a circuit for generating a first control signal including only a display period for displaying a frame of image data, and a display circuit for displaying the frame of data in accordance with said first control signal, and a coordinate indicate means, said apparatus comprising:

a detecting circuit for detecting coordinates of said coordinate indicate means;

a generating circuit for generating a second control signal including a display period and a non-display period from said first control signal, a sum of the duration of said display period and said non-display period of said second control signal being equal to the duration of said display period of said first control signal;

a memory means for storing the frame of image data; and

a control circuit for controlling said memory means to read out the stored image data in shorter time than storing time, said display circuit to display the read out image data in said display period of said control signal, and said detecting circuit to detect the coordinates of said coordinate indicate means in said nondisplay period of said control signal.

7. An apparatus according to claim 6, wherein said memory means includes a first frame memory and a second frame memory for storing the frame of image data, alternately.

8. An apparatus according to claim 6, wherein said memory means is a first-in first-out memory.

9. A coordinate detecting apparatus with a liquid crystal display unit and a coordinate indicate means, comprising:

a single common driving circuit for driving row electrodes of the liquid crystal display unit, said row electrodes being divided into a plurality of groups;

a segment driving circuit for driving column electrodes of the liquid crystal display unit;

a display control circuit for controlling the liquid crystal display unit in a display period for displaying a frame of image data;

a detecting circuit for detecting coordinates of the coordinate indicate means in a non-display period; and

a control circuit for controlling said display period and said non-display period,

said display period being divided into a plurality of periods each corresponding to one of said groups of said row electrodes, and said control circuit controlling said non-display period to be inserted at every interval of said plurality of periods so as to detect the coordinates a plurality of times within the display period for displaying the frame of image data,

wherein said control circuit applies a signal for removing a common pulse for displaying one of said electrode groups after the display period corresponding to said one of said electrode groups is completed, and said control circuit applies a signal for setting a common pulse for displaying next one of said electrode groups prior to the display period for said next one of said electrode groups in order to drive said plurality of electrode groups by said single common driving circuit.

10. An apparatus according to claim 9, wherein said row electrodes are divided into two groups.