COORDINATE DETECTION SYSTEM

• US 3,764,813 A
• Filed: 04/12/1972
• Issued: 10/09/1973
• Est. Priority Date: 04/12/1972
• Status: Expired due to Term

• Current Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Original Assignee: Barton Leigh Richardson, Frank John Clement
• Inventors: Clement, Frank John, Richardson, Barton Leigh
• Primary Examiner(s): Lawrence, James W.
• Assistant Examiner(s): Nelms, D. C.
• Application Number:
  US05/243,256
• Time in Patent Office: 545 Days
• Field of Search: 250/221,222,223,219CR,22R,22M 178/19 340/146.3,173LS
• US Class Current: 250/221
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G01D 5/342 the sensed object being the obturating part
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen

Abstract

In a coordinate detection system, the interruption of pulsed invisible light beams is used to determine the spatial coordinates of a passive stylus, such as a finger or a pencil, relative to an associated display. The system comprises a rectangular frame which houses two mutually perpendicular linear arrays of infrared light-emitting diodes and two perpendicular linear arrays of associated silicon detector diodes. Driving circuitry sequentially pulses the light emitters in repeating cycles. Associated detecting circuitry responds to the detectors and determines during each cycle the spatial coordinates of the interfering stylus. This spatial information is then coded and transmitted, if necessary. Sequential pulsing eliminates the need for beam collimating structures and lenses and allows for the application of high instantaneous power driving levels to the emitters.

Claims

1. A coordinate detection system wherein the interruption of crossing light pulses by a passive stylus is used to determine a coordinate location, said system comprising:

a rectangular frame;

first and second linear arrays of light-emitting means respectively mounted along two adjacent internal edges of said rectangular frame;

third and fourth linear arrays of light-detecting means respectively mounted along the remaining two adjacent internal edges of said rectangular frame, each detecting means principally receiving light from one associated emitting means;

means for causing said light-emitting means to generate light pulses in repeating scan cycles so that at least one X-directed light pulse and at least one Y-directed light pulse intersect each said coordinate location during each said scan cycle; and

means responsive to said light-detecting means for determining during each cycle which light-detecting means failed to receive a light pulse from their associated light-emitting means, thereby indicating the coordinate location of said interfering stylus.

2. The system of claim 1 wherein said light-emitting means are of the type which convert an input electrical signal to light and wherein said light-detecting means are of the type which convert incident light to an output electrical signal.

3. The system of claim 2 wherein said light-emitting means and light-detecting means are respectively light-emitting diodes and light-detecting diodes.

4. The system of claim 1 wherein said light-emitting means and light-detecting means are respectively infrared light-emitting means and infrared light-detecting means.

5. The system of claim 4, further comprising an infra-red filter located in front of each light-emitting and light-detecting means.

6. The system of claim 1 wherein said sequentially operable means further comprises means for simultaneously pulsing associated light-emitting means from each of said first and second linear arrays.

7. The system of claim 3 wherein corresponding light-emitting diodes from said first and second linear arrays are connected in series.

8. The system of claim 7 wherein said sequentially operable means includes:

a clock which provides periodic timing pulses; and

a shift register having a plurality of stages corresponding in number to the maximum number of light-emitting diodes in either of said first or second arrays, said shift register being responsive to said clock for sequentially pulsing said serial combinations of light-emitting diodes.

9. The system of claim 3 wherein said coordinate location indicating means includes:

a clock which provides periodic timing pulses;

a binary counter responsive to said clock whose count increases with each clock pulse;

means jointly responsive to said light-detecting diodes, said clock, and said counter for interrogating at each clock pulse the light-detecting diode which corresponds to the count of said counter; and

means jointly responsive to said counter and said interrogating means for indicating which light-detecting diodes, if any, failed to receive light from their associated light-emitting diodes.

10. The system of claim 1 further comprising amplifying circuitry and means for connecting the outputs of selected light-detecting means from each of said third and fourth linear arrays to said amplifying circuitry in such a manner that only one light-detecting means per group receives light at any given instant.

11. The system of claim 1 wherein said sequentially operable means and said coordinate location indicating means are also mounted On said rectangular frame.