Displacement detection system of an optical touch panel and method thereof

• US 8,269,749 B2
• Filed: 06/29/2010
• Issued: 09/18/2012
• Est. Priority Date: 06/30/2009
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: PixArt Imaging Incorporated
• Inventors: Lin, Chih-Hsin, Gu, Ren-Hau, Su, Tzung-Min, Lin, Cho-Yi
• Primary Examiner(s): Young, Wayne
• Assistant Examiner(s): BUTCHER, BRIAN M
• Application Number:
  US12/826,638
• Publication Number:
  US 20100328244A1
• Time in Patent Office: 812 Days
• Field of Search: None
• 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

At a first time, a first image sensor and a second image sensor capture a first image and a second image including images of an object respectively. At a second time, the first image sensor and the second image sensor capture a third image and a fourth image including images of the object respectively. A coordinate calculation device calculates a first coordinate of the object at the first time according to the first image and the second image, and a second coordinate of the object at the second time according to the third image and the fourth image. A coordinate correction device calculates a displacement between the first time and the second time according to the first coordinate and the second coordinate, and corrects an output coordinate of the object at the second time according to the displacement.

Claims

1. A displacement detection system of an optical touch panel, comprising:

a panel for being touched by an object;

at least one first image sensor and a second image sensor, wherein the first image sensor and the second image sensor are installed on different positions of the panel, and view of the first image sensor and view of the second image sensor are overlapped;

a coordinate calculation device for utilizing the first image sensor and the second image sensor to capture a first image and a second image including images of the object respectively at a first time, utilizing image positions of the object in the first image and the second image to calculate a first coordinate of the object at the first time, utilizing the first image sensor and the second image sensor to capture a third image and a fourth image including images of the object respectively at a second time, and using image positions of the object in the third image and the fourth image to calculate a second coordinate of the object at the second time; and

a coordinate correction device for calculating a displacement of the object between the first time and the second time according to the first coordinate and the second coordinate, and for correcting an output coordinate of the object at the second time according to the displacement.

2. The displacement detection system of claim 1, further comprising a light source for lighting the panel.

3. The displacement detection system of claim 1, wherein the coordinate correction device corrects the image positions of the object in the first image and the second image according to the displacement to obtain a first weighted image position, corrects the image positions of the object in the third image and the fourth image according to the displacement to obtain a second weighted image position, and calculates the output coordinate according to the first weighted image position and the second weighted image position.

4. The displacement detection system of claim 1, further comprising a smoothing parameter generating device for generating an adaptive smoothing parameter according to the displacement and the following equation:

5. The displacement detection system of claim 4, wherein the operation that the coordinate correction device corrects the output coordinate at the second time according to the adaptive smoothing parameter is according to the following equations:

y_o(t)=(1−

λ

)y_i(t)+λ

y_o(t−

1);

x_o(t)=(1−

λ

)x_i(t)+λ

x_o(t−

1);

wherein

y_o(t) is a corrected y coordinate of the object at the second time; and

x_o(t) is a corrected x coordinate of the object at the second time.

6. A displacement detection method of an optical touch panel, comprising:

capturing a first image including an object by a first image sensor and a second image including the object by a second image sensor on a panel at a first time;

capturing a third image including the object by the first image sensor and a fourth image including the object by the second image sensor on the panel at a second time;

calculating a first coordinate of the object at the first time according to image positions of the object in the first image and the second image;

calculating a second coordinate of the object at the second time according to image positions of the object in the third image and the fourth image;

calculating a displacement of the object between the first time and the second time according to the first coordinate and the second coordinate; and

correcting an output coordinate of the object at the second time according to the displacement.

7. The displacement detection method of claim 6, wherein correcting the output coordinate of the object at the second time according to the displacement comprises:

correcting the image positions of the object in the first image and the second image according to the displacement to obtain a first weighted image position;

correcting the image positions of the object in the third image and the fourth image according to the displacement to obtain a second weighted image position; and

correcting the output coordinate according to the first weighted image position and the second weighted image position.

8. The displacement detection method of claim 6, further comprising generating an adaptive smoothing parameter according to the displacement and the following equation, and correcting the output coordinate at the second time according to the adaptive smoothing parameter:

9. The displacement detection method of claim 8, wherein correcting the output coordinate at the second time according to the adaptive smoothing parameter is performed according to the following equations:

y_o(t)=(1−

λ

)y_i(t)+λ

y_o(t−

1);

x_o(t)=(1−

λ

)x_i(t)+λ

x_o(t−

1);

wherein

y_o(t) is a corrected y coordinate of the object at the second time; and

x_o(t) is a corrected x coordinate of the object at the second time.

10. A displacement detection system of an optical touch panel, comprising:

a panel for being touched by an object;

at least one first image sensor and a second image sensor, wherein the first image sensor and the second image sensor are installed on different positions of the panel, and view of the first image sensor and view of the second image sensor are overlapped;

a coordinate calculation device for saving an initial coordinate of the object on the panel at an initial time, utilizing the first image sensor and the second image sensor to capture a first image and a second image including images of the object respectively at a first time, and utilizing image positions of the object in the first image and the second image to calculate a first coordinate of the object at the first time; and

a coordinate correction device for calculating a displacement of the object between the initial time and the first time according to the initial coordinate and the first coordinate, and for correcting an output coordinate of the object at the first time according to the displacement.

11. The displacement detection system of claim 10, further comprising a smoothing parameter generating device for generating an adapting smoothing parameter according to the displacement and the following equation, and for correcting the output coordinate at the first time according to the adaptive smoothing parameter:

12. The displacement detection system of claim 11, wherein the operation that the coordinate correction device corrects an output coordinate of the object at the first time according to the displacement is performed according to the following equations:

y_o(t)=(1−

λ

)y_i(t)+λ

y_o(t−

1);

x_o(t)=(1−

λ

)x_i(t)+λ

x_i(t−

1);

wherein

y_o(t) is a corrected y coordinate of the object at the end first time; and

x_o(t) is a corrected x coordinate of the object at the first time.