Optical generic switch panel

• US 20070046640A1
• Filed: 08/29/2005
• Published: 03/01/2007
• Est. Priority Date: 08/29/2005
• Status: Active Grant

• Current Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Inventors: Keh, Kean, Oon, Chin, Chen, Fam
• Granted Patent: US 7,265,749 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G02B 6/0033 Means for improving the coupling-out of light from the light guide
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G06F 2203/04109 FTIR in optical digitiser, i.e. touch detection by frustrating the total internal reflection within an optical waveguide due to changes of optical properties or deformation at the touch location
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen

Abstract

A switch panel having a touch plate, image generator, imaging system and light source is disclosed. The touch plate includes an optically transparent layer having first and second surfaces in which a light signal is trapped by internal reflection. The image generator displays an image that includes a plurality of button positions to a person viewing the touch plate from the first surface. When the user touches the front surface at one of the button positions, light from a multi-LED light source that generates the trapped light signal is caused to escape the touch plate at a point corresponding to the point of contact. The light leaving the touch plate is imaged by the imaging system and used to determine the location of the point of contact. Images taken with different LEDs in the light source are used to make the contact determination to reduce the effects of ambient light.

Claims

1. A switch panel comprising:

a touch plate comprising an optically transparent layer having first and second surfaces, said optically transparent layer having an index of refraction greater than that of air;

an image generator that displays an image comprising a plurality of button positions to a person viewing said touch plate from said first surface;

an imaging system that records a color image of said first surface of said touch plate;

a controller that receives said image and that generates an output signal if said touch plate is touched at one of said button positions; and

a light source that generates a light signal that is reflected between said first and second surfaces of said touch plate within said transparent layer, said light source comprising a plurality of LEDs, each LED generating light having a different spectrum than the others of said LEDs, each LED being turned on in a predetermined sequence such that only one of said LEDs is turned on at a time.

2. The switch panel of claim 1 wherein said controller causes said imaging system to record a color position image of said first surface of said touch plate corresponding to each LED when that one of said LEDs is turned on.

3. The switch panel of claim 2 wherein said controller causes said imaging system to record a color background image of said first surface of said touch plate when none of said LEDs is turned on, and wherein said controller subtracts said color background image from each of said color position images to form a corrected color position image.

4. The switch panel of claim 3 wherein said controller combines said corrected color position images to determine if said touch plate has been touched and where said touch panel was touched.

5. The switch panel of claim 1 wherein said light signal is perceived to be a constant light signal of a predetermined color by a user viewing said signal.

6. The switch panel of claim 5 wherein a portion of said light signal exits said first surface of said touch plate when a user touches said first surface.

7. The switch panel of claim 1 wherein a portion of said light signal is reflected toward said second surface at an angle greater than the critical angle in said optically transparent layer when said first surface is touched with a force greater than a predetermined force.

8. The switch panel of claim 1 wherein said first surface deforms sufficiently when a predetermined pressure is applied thereto to cause a portion of said light signal to be reflected toward said second surface at an angle greater than the critical angle in said optically transparent layer.