Video display touch detection digitizer

• US 4,621,257 A
• Filed: 08/15/1983
• Issued: 11/04/1986
• Est. Priority Date: 08/15/1983
• Status: Expired due to Term

• Current Assignee: Bell Telephone Laboratories, Inc. (Nokia Corporation)
• Original Assignee: AT&T, Inc.
• Inventors: Brown, Earl F.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/523,000
• Time in Patent Office: 1,177 Days
• Field of Search: 340/706, 340/365 P, 340/712, 340/718, 367/907, 178/18, 178/30, 358/145, 358/142, 358/141
• US Class Current: 341/5
• CPC Class Codes: G06F 3/037 using the raster scan of a cathode-ray tube [CRT] for detecting the position of the member, e.g. light pens cooperating with CRT monitors
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen

Abstract

A video display touch detection digitizer for generating the coordinate position when the video display is touched. The light signals for the X and Y coordinate array are generated from the raster scan signals of the video display during selected periods of the vertical and horizontal blanking intervals. Vertical and horizontal mirrors reflect, respectively, the resulting row and columns of light signals across the screen of the video display where other mirrors reflect the signals to, respectively, row and column signal detectors. Control circuitry detects the resulting interruption in the rows and columns of light signals when the screen of the video display is touched and generates signals representing the touch coordinates.

Claims

1. A video display for displaying light images generated by a raster scan signal, said video display comprising

a video circuit for controlling said raster scan signals including

means for generating a plurality of first signals wherein each first signal is associated with one or more picture elements of a horizontal scan line which occurs during a vertical blanking interval of said raster scan and

means for generating a plurality of second signals wherein each second signal occurs during a horizontal blanking interval of said raster scan and is associated with one or more horizontal scan lines of a displayed light image;

and

a screen including an image display area for displaying light images in response to said raster scan signals and a coordinate display area for displaying discrete light sources in response to each of said first signals and said second signals.

2. The invention of claim 1 wherein said video display is a CRT and said coordinate display area of said screen is coated with a phosphorescent material having a shorter persistence time constant than a phosphorescent material coated on said image display area.

3. The video display of claim 1 wherein said video circuit further includes

a video combiner means for generating said raster scan signal for display on said image display area, wherein said video combiner means blanks said raster scan signal during said vertical and horizontal blanking interval, wherein said video combiner means unblanks said raster scan signal during said vertical blanking interval in response to each of said plurality of first signals from said first generating means and wherein said video combiner means unblanks said raster scan signal during said horizontal blanking interval in response to each of said plurality of second signals from said second generating means.

4. The video display of claim 1 wherein said image display area is rectangular and said coordinate display area includes a first and a second section extending along two adjacent sides of said image display area for displaying discrete light sources in response to each of said first and said second signals, respectively.

5. The video display of claim 4 wherein said first signal generating means generates every n^th signal of said plurality of first signals on each of n horizontal scan lines occurring during said vertical blanking interval thereby producing a display in said first section of said coordinate display area having n horizontal rows each containing one n^th of the discrete light sources, where n is an integer greater than 1.

6. The video display of claim 4 including

a first light deflecting means positioned in proximity to said first section of said coordinate display area for deflecting light from said discrete light sources therein across a predetermined part of said image display area of said screen, and

a second light deflecting means positioned in proximity to said second section of said coordinate display area for deflecting light from said discrete light source therein across said predetermined part of said image display area of said screen.

7. The video display of claim 6 further including

a first light detection means for receiving light deflected from said first light deflecting means and

a second light detection means for receiving light deflected from said second light deflecting means.

8. The video display of claim 7 further including

a third light deflecting means positioned to deflect light received from said first light deflecting means to said first light detecting means and

a fourth light deflecting means positioned to reflect light received from said second light deflecting means to said second light detecting means.

9. The video display of claim 8 wherein said first light detecting means is a first photodetector,

said third light deflecting means focuses the light received from said first light deflecting means onto said first photodetector,

wherein said second light detecting means is a second photodetector and

said fourth light deflecting means focuses the light received from said second light deflecting means onto said second photodetector.

10. The video display of claim 7 wherein said video circuit includes

first determining means responsive to said first signals and an output from said first light detecting means for determining the X-axis location along a horizontal scan line of said predetermined part of said image display area at which an interruption of the light signal from said first light deflecting means is detected by said first light detecting means and

second determining means responsive to said second signals and an output from said second light detecting means for determining the Y-axis location associated with one more horizontal scan lines of said predetermined part of said image display area at which an interruption of the light signal from said second light deflecting means is detected by said second light detecting means.

11. The video display of claim 10 wherein said first determining means includes means for calculating the average X-axis location of said predetermined part of said image display area at which the interruption of light signals from said first light deflecting device has occurred and

said second determining means includes means for calculating the average Y-axis location of said predetermined part of said image display area at which the interruption of light signals from said second light deflecting device has occurred.

12. The video display of claim 11 wherein said video circuit includes

means responsive to an output from said first determining means and an output from said second determining means for generating a cursor image on said image display area at the intersection location specified by said first determining means and said second determining means.