Sensing system and method for obtaining position of pointer thereof

• US 8,269,158 B2
• Filed: 09/10/2009
• Issued: 09/18/2012
• Est. Priority Date: 10/10/2008
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: PixArt Imaging Incorporated
• Inventors: Chen, Hsin-Chia, Su, Tzung-Min, Lu, Chih-Hung, Lin, Cho-Yi
• Primary Examiner(s): Sohn, Seung C
• Application Number:
  US12/557,451
• Publication Number:
  US 20100090950A1
• Time in Patent Office: 1,104 Days
• Field of Search: 250/203.1, 702150-153, 345157-158, 345/173, 382/312, 178/18.09
• US Class Current: 250/203.1
• 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

In a sensing system and a method for obtaining a position of a pointer, the sensing system includes a sensing area, a reflective mirror, an image sensor and a processing circuit. The reflective mirror is configured for generating a mirror image of a pointer when the pointer approaches the sensing area. The image sensor is configured for sensing the pointer and the mirror image thereof when the pointer approaches the sensing area. When the pointer approaches the sensing area, the processing circuit calculates a coordinate value of the pointer according to an image sensed by the image sensor and a predetermined size of the pointer. The pointer forms an imaginary orthographic projection in the sensing area, the processing circuit regards the imaginary orthographic projection as a round projection, and a radius of the round projection is the predetermined size.

Claims

1. A sensing system, comprising:

a sensing area;

a reflective mirror configured for generating a mirror image of a pointer when the pointer approaches the sensing area;

an image sensor configured for sensing the pointer and the mirror image thereof when the pointer approaches the sensing area; and

a processing circuit, when the pointer approaches the sensing area, the processing circuit calculating a coordinate value of the pointer according to the image sensed by the image sensor and a predetermined size of the pointer, wherein the pointer forms an imaginary orthographic projection in the sensing area, the processing circuit regards the imaginary orthographic projection as a round projection, and a radius of the round projection is the predetermined size.

2. The sensing system as claimed in claim 1, wherein when an image corresponding to the pointer and an image corresponding to the mirror image of the pointer sensed by the image sensor partially overlap, the image sensor senses a periphery of the pointer along a first sensing route, and the image sensor senses a periphery of the mirror image of the pointer along a second sensing route, the pointer and the mirror image thereof are between the first sensing route and the second sensing route, the processing circuit determines linear equations of the first sensing route and the second sensing route, defines a current axes coordinate of the pointer as a first unknown coordinate and defines a current axes coordinate of the mirror image of the pointer as a second unknown coordinate, the processing circuit also obtains a first equation according to the first unknown coordinate, the linear equation of the first sensing route and the predetermined size, and obtains a second equation according to the second unknown coordinate, the linear equation of the second sensing route and the predetermined size to calculate a value of the first unknown coordinate according to the first equation and the second equation as the coordinate value of the pointer, the first equation describes that a distance between the first unknown coordinate and the first sensing route is the predetermined size, and the second equation describes that a distance between the second unknown coordinate and the second sensing route is the predetermined size.

3. The sensing system as claimed in claim 1, wherein when an image corresponding to the pointer and an image corresponding to the mirror image of the pointer sensed by the image sensor do not partially overlap, the image sensor senses a periphery of the pointer along a first sensing route and a second sensing route, the pointer is between the first sensing route and the second sensing route, the processing circuit determines linear equations of the first sensing route and the second sensing route and defines a current axes coordinate of the pointer as an unknown coordinate, the processing circuit also obtains a first equation according to the unknown coordinate, the linear equation of the first sensing route and the predetermined size, and obtains a second equation according to the unknown coordinate, the linear equation of the second sensing route and the predetermined size to calculate a value of the unknown coordinate according to the first equation and the second equation as the coordinate value of the pointer, the first equation describes that a distance between the unknown coordinate and the first sensing route is the predetermined size, and the second equation describes that a distance between the unknown coordinate and the second sensing route is the predetermined size.

4. The sensing system as claimed in claim 1, wherein when an image corresponding to the pointer and an image corresponding to the mirror image of the pointer sensed by the image sensor do not overlap, the image sensor senses a periphery of the mirror image of the pointer along a first sensing route and a second sensing route, the mirror image of the pointer is between the first sensing route and the second sensing route, the processing circuit determines linear equations of the first sensing route and the second sensing route, and defines a current axes coordinate of the mirror image of the pointer as an unknown coordinate, the processing circuit further obtains a first equation according to the unknown equation, the linear equation of the first sensing route and the predetermined size, and obtains a second equation according to the unknown equation, the linear equation of the second sensing route and the predetermined size to calculate a value of the unknown coordinate according to the first equation and the second equation as the coordinate value of the pointer, the first equation describes that a distance between the unknown coordinate and the first sensing route is the predetermined size, and the second equation describes that a distance between the unknown coordinate and the second sensing route is the predetermined size.

5. The sensing system as claimed in claim 1, wherein the step of the processing circuit obtaining the predetermined size is firstly obtaining the coordinate value of the pointer, at this moment, the processing circuit forms a tangent point on the round projection along an imaginary route through the image sensor, then the processing circuit calculates a distance between a coordinate of the pointer and the tangent point as the predetermined size.

6. The sensing system as claimed in claim 1, wherein the step of the processing circuit obtaining the predetermined size is firstly obtaining the coordinate value of the mirror image of the pointer, and regarding the mirror image of the pointer as an mirror image of the round projection, at this moment, the processing circuit forms a tangent point on the mirror image of the round projection along an imaginary route through the image sensor, then the processing circuit calculates a distance between a coordinate of the mirror image of the pointer and the tangent point as the predetermined size.

7. A method for obtaining a position of a pointer, adapted to a sensing system, the sensing system comprising a sensing area, a reflective mirror and an image sensor, the reflective mirror being configured for generating a mirror image of the pointer when the pointer approaches the sensing area, the image sensor being configured for sensing the pointer and the mirror image thereof when the pointer approaches the sensing area, the method comprising:

determining whether the pointer approaches the sensing area; and

when determining the pointer approaches the sensing area, calculating a coordinate value of the pointer according to an image sensed by the image sensor and a predetermined size of the pointer,

wherein the pointer forms an imaginary orthographic projection in the sensing area, the imaginary orthographic projection is regarded as a round projection, and a radius of the round projection is the predetermined size.

8. The method as claimed in claim 7, wherein when an image corresponding to the pointer and an image corresponding to the mirror image of the pointer sensed by the image sensor partially overlap, the image sensor senses a periphery of the pointer along a first sensing route, and the image sensor senses a periphery of the mirror image of the pointer along a second sensing route, the pointer and the mirror image thereof are between the first sensing route and the second sensing route, the step of calculating the coordinate value of the pointer comprises:

determining linear equations of the first sensing route and the second sensing route, defining a current axes coordinate of the pointer as a first unknown coordinate, and defining a current axes coordinate of the mirror image of the pointer as a second unknown coordinate;

obtaining a first equation according to the first unknown coordinate, the linear equation of the first sensing route and the predetermined size, wherein the first equation describes that a distance between the first unknown coordinate and the first sensing route is the predetermined size;

obtaining a second equation according to the second unknown coordinate, the linear equation of the second sensing route and the predetermined size, wherein the second equation describes that a distance between the second unknown coordinate and the second sensing route is the predetermined size; and

calculating a value of the first unknown coordinate according to the first equation and the second equation as the coordinate value of the pointer.

9. The method as claimed in claim 7, wherein when an image corresponding to the pointer and an image corresponding to the mirror image of the pointer sensed by the image sensor do not overlap, the image sensor senses a periphery of the pointer along a first sensing route and a second sensing route, the pointer is between the first sensing route and the second sensing route, the step of calculating the coordinate value of the pointer comprise:

determining linear equations of the first sensing route and the second sensing route, and defining a current axes coordinate of the pointer as an unknown coordinate;

obtaining a first equation according to the unknown coordinate, the linear equation of the first sensing route and the predetermined size, wherein the first equation describes that a distance between the unknown coordinate and the first sensing route is the predetermined size;

obtaining a second equation according to the unknown coordinate, the linear equation of the second sensing route and the predetermined size, wherein the second equation describes that a distance between the unknown coordinate and the second sensing route is the predetermined size; and

calculating a value of the unknown coordinate according to the first equation and the second equation as the coordinate value of the pointer.

10. The method as claimed in claim 7, wherein when an image corresponding to the pointer and an image corresponding to the mirror image of the pointer sensed by the image sensor do not overlap, the image sensor senses a periphery of the mirror image of the pointer along a first sensing route and a second sensing route, the mirror image of the pointer is between the first sensing route and the second sensing route, and the step of calculating the coordinate value of the pointer comprises:

determining linear equations of the first sensing route and the second sensing route, and defining a current axes coordinate of the mirror image of the pointer as an unknown coordinate;

obtaining a first equation according to the unknown coordinate, the linear equation of the first sensing route and the predetermined size, wherein the first equation describes that a distance between the unknown coordinate and the first sensing route is the predetermined size;

obtaining a second equation according to the unknown coordinate, the linear equation of the second sensing route and the predetermined size, wherein the second equation describes that a distance between the unknown coordinate and the second sensing route is the predetermined size; and

calculating a value of the unknown coordinate according to the first equation and the second equation to further calculate the coordinate value of the pointer.

11. The method as claimed in claim 7, wherein the sensing system further comprises a processing circuit, and the step of obtaining the predetermined size comprises:

obtaining the coordinate value of the pointer, wherein at this moment, the processing circuit forms a tangent point on the round projection along an imaginary route through the image sensor; and

calculating a distance between a coordinate of the pointer and the tangent point as the predetermined size.

12. The method as claimed in claim 7, wherein the sensing system further comprises a processing circuit, and the step of obtaining the predetermined size comprises:

obtaining the coordinate value of the mirror image of the pointer and regarding the mirror image of the pointer as a mirror image of the round projection, wherein at this moment, the processing circuit forms a tangent point on the mirror image of the round projection along an imaginary route through the image sensor; and

calculating a distance between a coordinate of the mirror image of the pointer and the tangent point as the predetermined size.