TOUCH DETECTION APPARATUS AND TOUCH POINT DETECTION METHOD

• US 20110084938A1
• Filed: 01/26/2010
• Published: 04/14/2011
• Est. Priority Date: 10/08/2009
• Status: Active Grant

• Current Assignee: Silicon Motion Incorporated California (Silicon Motion)
• Original Assignee: Silicon Motion Incorporated California (Silicon Motion)
• Inventors: Wang, Karl-Lin
• Granted Patent: US 8,922,526 B2
• Time in Patent Office: Days
• US Class Current: 345/175
• CPC Class Codes: G06F 3/0428 by sensing at the edges of the touch surface the interruption of optical paths, e.g. an illumination plane, parallel to the touch surface which may be virtual sensing beam interruptions in a planar beam grid of an optical touch-screen G06F3/0421

Abstract

A touch detection apparatus is provided, in which a touch panel is implemented with four surrounding edges. Three of the edges are embedded with retro-reflection materials. Light sources and pinholes are deployed on both corners of the touch panel, allowing reflections from the three edges to be projected on light sensors through the pinhole. The images projected on the light sensors are analyzed to determine coordinates of one or more contact points on the touch panel.

Claims

1. A touch detection apparatus for detecting a location of a touch point touched by an object, comprising:

a touch panel for receiving contact from at least one object;

a first edge, a second edge, a third edge and a fourth edge for encircling the touch panel, wherein the first edge is opposite to the second edge and the third edge is opposite to the fourth edge, and the first edge, the second edge and the third edge comprise retro-reflection materials;

a first pinhole and a first light source disposed on the corner of the first edge and the fourth edge for emitting a first light beam toward the second edge and the third edge to generate a first reflection light;

a second pinhole and a second light source disposed on the corner of the second edge and the fourth edge for emitting a second light beam toward the first edge and the third edge to generate a second reflection light;

a first light sensor module disposed at the outer edge of the touch panel and separated from the first pinhole by a predetermined distance for detecting a first image projected on the first light sensor module by the first reflection light through the first pinhole;

a second light sensor module disposed at the outer edge of the touch panel and separated from the second pinhole by the predetermined distance for detecting a second image projected on the second light sensor module by the second reflection light through the second pinhole; and

a calculation unit coupled to the first light sensor module and the second light sensor module for receiving the first image and the second image, wherein the calculation unit performs an image analysis process according to the first image and the second image when at least one object contacts the touch panel, so as to determine a coordinate of the touch point where the touch panel is contacted by the at least one object.

2. The touch detection apparatus as claimed in claim 1, wherein the first light sensor module and the second light sensor module are characterized by a one-dimensional structure with the same length, and the first image and the second image are one-dimensional line images.

3. The touch detection apparatus as claimed in claim 2, wherein the first edge and the second edge have a first length, and the third edge and the fourth edge have a second length.

4. The touch detection apparatus as claimed in claim 3, wherein the first light source and the second light source are light emitting diodes, and the first light beam and the second light beam comprise at least a laser beam, an infrared ray, or a visible ray.

5. The touch detection apparatus as claimed in claim 3, wherein:

when a first object touches the touch panel on a first touch point, the first reflection light is obstructed by the first object to generate a first obstructed point on the first image and the second reflection light is obstructed by the first object to generate a second obstructed point on the second image, and

the calculation unit performs the image analysis process by calculating a first angle formed between a direction from the first object to the first pinhole and the first edge based on an obstructed location of the first obstructed point on the first image, and calculating a second angle formed between a direction from the first object to the second pinhole and the second angle based on an obstructed location of the second obstructed point on the second image.

6. The touch detection apparatus as claimed in claim 5, wherein the calculation unit performs the image analysis process to calculate the first angle and the second angle according to the following angle formula:

7. The touch detection apparatus as claimed in claim 6, wherein the calculation unit further performs the image analysis process to obtain a coordinate of the first touch point via a conversion operation based on the first angle, the second angle, the first length, and the second length.

8. The touch detection apparatus as claimed in claim 7, wherein the conversion operation is accomplished by using the following formula:

9. The touch detection apparatus as claimed in claim 8, wherein:

when the first object and a second object touch the touch panel on different touch points, the first reflection light is obstructed by the first object and the second object to generate two obstructed points on the first image and the second reflection light is obstructed by the first object and the second object to generate two obstructed points on the second image, and

the calculation unit substitutes any two obstructed locations of the obstructed points on the first image and the second image into the angle formula and performs the conversion operation to obtain a first set of possible solutions which comprises four coordinate candidates of the touch points.

10. The touch detection apparatus as claimed in claim 9, further comprising:

a third pinhole disposed on the middle of the fourth edge; and

a third light sensor module disposed at the outer edge of the fourth edge towards the third pinhole for detecting a third image projected on the third light sensor module by the first reflection light and the second reflection light through the third pinhole.

11. The touch detection apparatus as claimed in claim 10, wherein:

the third image is obstructed by the first object and the second object to generate two obstructed points thereon, and the calculation unit substitutes any two obstructed locations of the obstructed points on the first image and the third image into the angle formula and performs the conversion operation to obtain a second set of possible solutions which comprises four coordinate candidates of the touch points, and

the calculation unit determines the coordinates of the touch points touched by the first object and the second object in the intersection of the first set of possible solutions and the second set of possible solutions.

12. The touch detection apparatus as claimed in claim 10, wherein:

the third light sensor module comprises a left light sensor and a right light sensor with the same length that are disposed perpendicularly to each other on the fourth edge to form an isosceles triangle,

perpendicular bisectors of the left light sensor and the right light sensor are respectively towards the third pinhole, and

the third image comprises;

a left half image obtained by the left light sensor detecting the first reflection light of the second edge and the third edge; and

a right half image obtained by the right light sensor detecting the second reflection light of the first edge and the third edge.

13. The touch detection apparatus as claimed in claim 12, wherein:

the calculation unit substitutes the left half image and the second image into the angle formula and performs the conversion operation to obtain one part of the touch point candidates of the second set of possible solutions, and

the calculation unit substitutes the right half image and the second image into the angle formula and performs the conversion operation to obtain the other part of touch point candidates of the second set of possible solutions.

14. A touch point detection method for detecting a location of a touch point on a touch panel contacted by at least one object, the method comprises the following steps:

providing a first edge, a second edge, a third edge and a fourth edge for encircling the touch panel, wherein the first edge is opposite to the second edge and the third edge is opposite to the fourth edge, and the first edge, the second edge and the third edge comprise retro-reflection materials;

providing a first light beam toward the second edge and the third edge on the corner of the first edge and the fourth edge to generate a first reflection light;

providing a second light beam toward the first edge and the third edge on the corner of the second edge and the fourth edge to generate a second reflection light;

disposing a first pinhole on the corner of the first edge and the fourth edge, and a second pinhole on the corner the second edge and the fourth edge;

disposing a first light sensor module at the outer edge of the touch panel and separated from the first pinhole by a predetermined distance for detecting a first image projected on the first light sensor module by the first reflection light through the first pinhole; and

disposing a second light sensor module at the outer edge of the touch panel and separated from the second pinhole by the predetermined distance for detecting a second image projected on the second light sensor module by the second reflection light through the second pinhole,

wherein an image analysis process is performed according to the first image and the second image when the at least one object contacts the touch panel, so as to determine a coordinate of the touch point where the touch panel is contacted by the at least one object.

15. The touch point detection method as claimed in claim 14, wherein:

the first light sensor module and the second light sensor module are characterized by a one-dimensional structure with the same length, and the first image and the second image are one-dimensional line images,

the first edge and the second edge have a first length, and

the third edge and the fourth edge have a second length.

16. The touch point detection method as claimed in claim 15, wherein the step of providing the first light beam and the second light beam comprises the step of:

utilizing light emitting diodes to emit an infrared ray or a visible ray.

17. The touch point detection method as claimed in claim 15, wherein:

when a first object touches the touch panel on a first touch point, the first reflection light is obstructed by the first object to generate a first obstructed point on the first image and the second reflection light is obstructed by the first object to generate a second obstructed point on the second image, and

the image analysis process comprises the steps of;

calculating a first angle θ

1 formed between a direction from the first object to the first pinhole and the first edge based on an obstructed location of the first obstructed point on the first image; and

calculating a second angle θ

2 formed between a direction from the first object to the second pinhole and the second edge based on an obstructed location of the second obstructed point on the second image.

18. The touch point detection method as claimed in claim 17, wherein the image analysis process further comprises the step of:

substituting the obstructed location of the first obstructed point on the first light sensor module and the obstructed location of the second obstructed point on the second sensor module to calculate the first angle and the second angle according to the following angle formula;

19. The touch point detection method as claimed in claim 18, wherein

the image analysis process further comprises the step of:

obtaining a coordinate of the first touch point via a conversion function based on the first angle, the second angle, the first length, and the second length, and

the conversion function is represented as;

20. The touch point detection method as claimed in claim 19, further comprising the steps of:

disposing a third pinhole on the middle of the fourth edge and a third light sensor module at the outer edge of the fourth edge towards the third pinhole for detecting a third image projected on the third light sensor module by the first reflection light and the second reflection light through the third pinhole,

wherein when the first object and a second object touch the touch panel on different touch points, the first reflection light is obstructed by the first object and the second object to generate two obstructed points on the first image and the second reflection light is obstructed by the first object and the second object to generate two obstructed points on the second image, and the third image is obstructed by the first object and the second object to generate two obstructed points thereon, and

the image analysis process further comprises the steps of;

substituting any two obstructed locations of the obstructed points on the first image and the second image respectively from the first object and the second object into the angle formula and perform the conversion function to obtain a first set of possible solutions which comprises four coordinate candidates of the touch points;

substituting any two obstructed locations of the obstructed points on the first image and the third image respectively from the first object and the second object into the angle formula and perform the conversion function to obtain a second set of possible solutions which comprises four coordinate candidates of the touch points; and

determining the coordinates of the touch points touched by the first object and the second object in the intersection of the first set of possible solutions and the second set of possible solutions.

21. The touch point detection method as claimed in claim 20, wherein:

the perpendicular bisectors of the left light sensor and the right light sensor are towards the third pinhole; and

the third light sensor module comprises a left light sensor and a right light sensor with the same length that are disposed perpendicularly to each other on the fourth edge to form an isosceles triangle,

perpendicular bisectors of the left light sensor and the right light sensor are respectively towards the third pinhole, and

the image analysis process further comprises the steps of;

obtaining a left half image of the third image by the left light sensor detecting the first reflection light of the second edge and the third edge; and

obtaining a right half image of the third image by the right light sensor detecting the second reflection light of the first edge and the third edge.

22. The touch point detection method as claimed in claim 21, further comprising the steps of:

taking the left half image and the second image into the said angle equation and the conversion equation so as to obtain one part of the touch point candidates of the second set of possible solutions; and

taking the right half image and the second image into the said angle equation and the conversion equation so as to obtain the other part of touch point candidates of the second set of possible solutions.