Touch panel using modulated light

• US 4,893,120 A
• Filed: 11/18/1988
• Issued: 01/09/1990
• Est. Priority Date: 11/26/1986
• Status: Expired due to Fees

• Current Assignee: Lucas Automation & Control Engineering, Inc.
• Original Assignee: Digital Electronics Corporation (Schneider Electric SE)
• Inventors: McManus, Colin F., Doering, Roger W.
• Primary Examiner(s): Oberley, Alvin
• Application Number:
  US07/274,708
• Time in Patent Office: 417 Days
• Field of Search: 340/706, 340/707, 340/365 P, 340/712, 250/221, 250/214 B, 250/214 C, 178/18, 178/17 D, 341/26, 341/31, 341/5, 73/DIG. 11
• US Class Current: 341/31
• CPC Class Codes: G01V 8/20 using multiple transmitters or receivers
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen

Abstract

A touch panel system using modulated light beams to enable the system to detect when one or more of the light beams are blocked even in bright ambient light conditions. The system has a "touch sensitive" display surface with a defined perimeter. Surrounding the display surface are a multiplicity of light emitting elements and light receiving elements. These elements are located so that the light paths defined by selected pairs of light emitting and light receiving elements cross the display surface and define a grid of intersecting light paths. A scanning circuit sequentially enables selected pairs of the light emitting and light receiving elements, modulating the amplitude of the light emitted in accordance with a predetermined pattern. A filter generates a blocked path signal if the currently enabled light receiving element is not generating an output signal modulated in accordance with the predetermined pattern. Finally a computer is used to determine if an object is adjacent to the display surface and the location of the object, by determining if the filter is generating at least two blocked path signals corresponding to light paths which intersect each other within the perimeter of the display surface. A failure detection circuit for testing the LEDs and phototransistors, by checking for blocked LED/phototransistor pairs. When a blocked pair is found the phototransistor of the blocked pair is paired with an LED near the blocked LED and the block LED is paired with a photo-transistor near the blocked LED to determine if they have failed.

Claims

1. A touch panel, comprising:

a display surface having a defined perimeter;

a multiplicity of light emitting elements and light receiving elements;

said elements located so that the light paths defined by selected pairs of light emitting and light receiving elements cross said display surface and define a grid of intersecting light paths thereon;

said light receiving elements including means for generating an output signal corresponding to the amplitude of the light received thereby;

scanning means for sequentially enabling selected pairs of said light emitting and light receiving elements;

modulation means for modulating the amplitude of the light emitted by the currently enabled light emitting element at a frequency of at least 10 kilohertz in accordance with a predetermined pattern;

filter means for generating a blocked path signal if the currently enabled light receiving means is not generating an output signal modulated in accordance with said predetermined pattern; and

computer means, responsive to signals from said filter means, for determining if an object is adjacent to said display surface and the location of said object, including means for determining if said filter means is generating at least two blocked path signals corresponding to light paths which intersect each other within the perimeter of said display surface;

including component failure detection means, including means for testing a selected light emitting element, said testing means including means for;

enabling said selected light emitting element and a light receiving element across said display surface from said light emitting element, and testing for the presence of a blocked path signal;

enabling the same light receiving element and a second light emitting element which is located near said selected light emitting element, and testing for the presence of a blocked path signal; and

denoting the detection of a component failure if a blocked path signal is detected when said selected light emitting element is enabled, but no blocked path signal is detected when said second light emitting element is enabled.

2. A touch panel, comprising:

a display surface having a defined perimeter;

a multiplicity of light emitting elements and light receiving elements;

said elements located so that the light paths defined by selected pairs of light emitting and light receiving elements cross said display surface and define a grid of intersecting light paths thereon;

said light receiving elements including means for generating an output signal corresponding to the amplitude of the light received thereby;

scanning means for sequentially enabling selected pairs of said light emitting and light receiving elements;

modulation means for modulating the amplitude of the light emitted by the currently enabled light emitting element in accordance with a predetermined pattern;

filter means for generating a blocked path signal if the currently enabled light receiving means is not generating an output signal modulated in accordance with said predetermined pattern;

computer means, responsive to signals from said filter means, for determining if an object is adjacent to said display surface and the location of said object, including means for determining if said filter means is generating at least two blocked path signals corresponding to light paths which intersect each other within the perimeter of said display surface;

and component failure detection means for testing the operability of a selected one of said elements by performing the steps of;

enabling said selected element and a complementary element across said display surface from said selected element, and testing for the presence of a blocked path signal;

enabling the same complementary element and a second element of the same type as said selected element and which is located near said selected element, and testing for the presence of a blocked path signal; and

denoting the detection of a component failure if a blocked path signal is detected when said selected element is enabled, but no blocked path signal is detected when said second element is enabled.

3. A touch panel as set forth in claim 2, wherein said component failure detection means includes means for sequentially testing the operability of all of said elements.

4. A touch panel as set forth in claim 3, wherein said component failure detection means includes means for displaying a message on said display surface requesting the user to prevent any objects from touching said display surface.

5. A method of locating the position of an object adjacent to a display surface having a defined perimeter, the steps of the method comprising:

providing a multiplicity of light emitting elements and light receiving elements;

said elements located so that the light paths defined by selected pairs of light emitting and light receiving elements cross said display surface and define a grid of intersecting light paths thereon;

sequentially energizing selected pairs of said light emitting and light receiving elements;

modulating the amplitude of the light emitted by the currently enabled light emitting element at a frequency of at least 10 kilohertz in accordance with a predetermined pattern;

generating a blocked path signal if the light received by the currently enabled light receiving means is not modulated in accordance with said predetermined pattern; and

generating a location signal when, during a single sequential energization of said elements, at least two blocked path signals are generated corresponding to light paths which intersect each other within the perimeter of said display surface;

further including the step of testing the operability of a selected one of said elements by performing the steps of;

enabling said selected element and a complementary element across said display surface from said selected element, and testing for the presence of a blocked path signal;

enabling the same complementary element and a second element of the same type as said selected element and which is located near said selected element, and testing for the presence of a blocked path signal; and

denoting the detection of a component failure if a blocked path signal is detected when said selected element is enabled, but no blocked path signal is detected when said second element is enabled.

6. A method as set forth in claim 5, further including the step of sequentially testing the operability of all of said elements.

7. A method of locating the position of an object adjacent to a display surface having a defined perimeter, the steps of the method comprising:

providing a multiplicity of light emitting elements and light receiving elements;

said elements located so that the light paths defined by selected pairs of light emitting and light receiving elements cross said display surface and define a grid of intersecting light paths thereon;

sequentially energizing selected pairs of said light emitting and light receiving elements;

generating a blocked path signal when the currently enabled light receiving means does not receive the light emitted from the currently enabled light emitting means; and

testing the operability of a selected one of said elements by performing the steps of;

enabling said selected element and a complementary element across said display surface from said selected element, and testing for the presence of a blocked path signal;

enabling the same complementary element and a second element of the same type as said selected element and which is located near said selected element, and testing for the presence of a blocked path signal; and

denoting the detection of a component failure if a blocked path signal is detected when said selected element is enabled, but no blocked path signal is detected when said second element is enabled.

8. A method as set forth in claim 7, further including the step of sequentially testing the operability of all of said elements.

9. A touch panel, comprising:

a display surface having a defined perimeter;

a multiplicity of light emitting elements and light receiving elements;

said elements located so that the light paths defined by selected pairs of light emitting and light receiving elements cross said display surface and define a grid of intersecting light paths thereon;

said light receiving elements including means for generating an output signal corresponding to the amplitude of the light received thereby;

scanning means for sequentially enabling selected pairs of said light emitting and light receiving elements;

blockage detection means for generating a blocked path signal when the currently enabled light receiving means does not receive the light emitted from the currently enabled light emitting means; and

component failure detection means, including testing means coupled to said blockage detection means for testing a selected light emitting element, said testing means including means for;

enabling said selected light emitting element and a light receiving element across said display surface from said light emitting element, and testing for the presence of a blocked path signal;

enabling the same light receiving element and a second light emitting element which is located near said selected light emitting element, and testing for the presence of a blocked path signal; and

denoting the detection of a component failure if a blocked path signal is detected when said selected light emitting element is enabled, but no blocked path signal is detected when said second light emitting element is enabled.