Liquid crystal display device

• US 4,405,921 A
• Filed: 05/11/1981
• Issued: 09/20/1983
• Est. Priority Date: 05/12/1980
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Suwa Seikosha
• Original Assignee: Kabushiki Kaisha Suwa Seikosha
• Inventors: Mukaiyama, Fumiaki
• Primary Examiner(s): Curtis, Marshall M.
• Application Number:
  US06/262,357
• Time in Patent Office: 862 Days
• Field of Search: 340/708, 340/707, 340/709, 340/712, 340/706, 340/784, 340/765
• US Class Current: 345/182
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/042 by opto-electronic means

Abstract

A light crystal display device which includes a liquid crystal panel and a light pen. The liquid crystal panel includes a plurality of display dots defined by spaced electrodes having a twisted nematic liquid crystal therebetween. The display dots are selectively driven by a drive circuit between light-transmissive and non-transmissive states in a predetermined flickering timing. The light pen selectively directs light to the display dots which is caused to flicker thereby. The flickered light is detected by a sensor in the light pen and produces positioning data signals representative of the sequence of dots selected.

Claims

1. A liquid crystal display device comprising liquid crystal display means including a plurality of liquid crystal display dots arranged in a matrix array to define a group of rows and a group of columns, each said liquid crystal display dot having a row position and a column position, driving circuit means including flickering means for selectively flickering;

each of said display dots between light-transmissive and non-transmissive states in a predetermined flickering timing, said flickering means providing a different switching time between said light-transmissive and non-transmissive states for each said row and column, respectively, in one of said groups of rows and columns of said display dots, said flickering means providing a different length of time that each respective row and column in the other one of said groups of rows and columns is in said light-transmissive state whereby each display dot has a unique flickering timing, light means for selectively directing light to selected display dots, said light being flickering by the switching of said selected display dots through which the light passes, and sensor means including light receiving means for detecting the flickered light passing through said selected display dots.

2. The liquid crystal display device, as claimed in claim 1, wherein each display dot is defined by a first electrode and a second electrode spaced from said first electrode and having a liquid crystal material disposed therebetween, said display dots being selectively driven between said light-transmissive and non-transmissive states by said driving circuit means in said predetermined timing.

3. The liquid crystal display device, as claimed in claim 2, wherein said sensor means includes converter circuit means for indicating the position of said selected display dots on said display means in response to the flickered light detected by said light receiving means.

4. The liquid crystal display device, as claimed in claim 3 wherein said flickering means selectively switches each said display dot between said light-transmissive and non-transmissive states in a different timing, light from said light means being flickered in said different timing when passing through respective display dots.

5. The liquid crystal display device, as claimed in claim 4, wherein said converter circuit means transforms the different flickering timing of light passing through a selected display dot and detected by said light receiving means into dot positioning data.

6. The liquid crystal display device, as claimed in claim 5, wherein said converter circuit means includes counter means for counting the switching time of said selected display dots and for counting the time that said selected display dots are in the transmissive state.

7. The liquid crystal display device, as claimed in claim 6, wherein said converter circuit means includes flip-flop means for indicating the row position of said selected display dots and subtraction means for indicating the column position of said selected display dots.

8. The liquid crystal display device, as claimed in claim 3 or 7, wherein said light means selectively directs light to a sequence of display dots, said light receiving means detecting the flickered timing of light passing through said sequence of display dots and producing signals representative thereof, said converter circuit means indicating the sequence of display dots through which said light passes.

9. The liquid crystal display device, as claimed in claim 8, wherein said light receiving means and said light means are formed into a light pen.

10. The liquid crystal display device, as claimed in claim 9, wherein said light means is a light emitting diode.

11. The liquid crystal display device, as claimed in claim 9, wherein said light receiving means is a photo diode.

12. The liquid crystal display device, as claimed in claim 11, wherein said light means is a light emitting diode.

13. The liquid crystal display device, as claimed in claim 10, wherein said light receiving means is a photo transistor.

14. The liquid crystal display device, as claimed in claim 8, wherein said liquid crystal material is in a twisted nematic mode.