Touch Control Apparatus and Touch Point Detection Method

• US 20110141030A1
• Filed: 12/14/2009
• Published: 06/16/2011
• Est. Priority Date: 12/14/2009
• Status: Active Grant

• Current Assignee: Silicon Motion Incorporated California (Silicon Motion)
• Original Assignee: Silicon Motion Incorporated California (Silicon Motion)
• Inventors: Chen, Yung-Wei
• Granted Patent: US 8,558,804 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• 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 control apparatus, having a touch pad receiving contact from at least one object is provided. Four edges form a rectangle that encircles the touch pad. All the edges are surfaced with geometric textures. A first camera is deposited on a corner of the first edge and the fourth edge of the rectangle, having a field of view sufficient to collect a first image including the second edge and third edge of the rectangle. A second camera is deposited on a corner of the second edge and the fourth edge of the rectangle, having a field of view sufficient to collect a second image including the first edge and third edge of the rectangle. A calculation unit performs a characteristic extraction process on the geometric textures of the first and second images to determine whether an object has touched the touch pad, and if so, coordinates thereof are determined.

Claims

1. A touch control apparatus, comprising:

a touch pad, receiving contact from at least one object;

a first edge, a second edge, a third edge and fourth edge forming a rectangle that encircles the touch pad, wherein the first edge is opposite to the second edge, the third edge is opposite to the fourth edge, and the first edge, the second edge, and the third edge are surfaced with geometric textures;

a first camera, deposited on a corner of the first edge and the fourth edge of the rectangle, having a field of view sufficient to collect a first image including the second edge and third edge;

a second camera, deposited on a corner of the second edge and the fourth edge of the rectangle, having a field of view sufficient to collect a second image including the first edge and third edge; and

a calculation unit, coupled to the first camera and second camera, performing a characteristic extraction process on the geometric textures of the first and second images to determine whether an object has touched the touch pad, and if so, coordinates thereof are determined.

2. The touch control apparatus as claimed in claim 1, wherein when an object touches the touch pad on a touch point:

the first camera captures images of the second edge, third edge and the touch point to form the first image;

the second camera captures images of the second edge, third edge and the touch point to form the second image; and

the first and second images are one dimensional line images.

3. The touch control apparatus as claimed in claim 2, wherein:

the object on the touch point is an obstruction preventing geometric textures on relative locations to be presented on the first and second images; and

the calculation unit performs the characteristic extraction process on the geometric textures of the first and second images to identify obstruction locations on the first and second images respectively.

4. The touch control apparatus as claimed in claim 3, wherein:

the geometric textures comprise periodic high contrast stripe patterns;

when performing the characteristic extraction process, the first and second images are processed as a plurality of incremental segments, and the calculation unit detects edge sum variations between each incremental segment; and

if an edge sum of a particular segment is varied by a rate beyond an expected average value, its corresponding location is assessed as being obstructed.

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

the geometric textures comprise predetermined hue values in the Hue Saturation Lightness (HSL) color space;

when performing the characteristic extraction process, the first and second images are processed as a plurality of incremental segments, and the calculation unit detects hue value variations between each adjacent incremental segment; and

if a hue value of a particular segment is varied by a rate beyond an expected average value, its corresponding location is assessed as being obstructed.

6. The touch control apparatus as claimed in claim 3, wherein:

the calculation unit determines a first angle indicating a direction from the first camera to the touch point based on a first obstructed point on the first image, and a second angle indicating a direction from the second camera to the touch point based on a second obstructed point on the second image; and

the calculation unit performs a geometric calculation based on the first angle, the second angle, and the width and height of the touch pad to determine the coordinates of the touch point.

7. The touch control apparatus as claimed in claim 6, wherein the first and second angles are calculated by the calculation unit substituting the first and second obstruction locations into a linear function to determine the first and second angles.

8. The touch control apparatus as claimed in claim 7, wherein:

the linear function is obtained by the calculation unit performing a calibration process on the touch pad;

when performing the calibration process, the touch pad receives contact on each corners of the touch pad, wherein angles of the corners are predetermined known values based on the width and height of the touch pad;

the calculation unit detects the obstruction locations on the first and second images related to the corners to establish relationships between the known angles and the obstructed locations; and

the calculation unit performs linear interpolation to derive other angle values related to non-corner locations on the first and second images.

9. The touch control apparatus as claimed in claim 3, wherein the calculation unit determines the coordinates according to a look up table and the obstruction locations.

10. A touch point detection method, comprising:

providing a touch pad for receiving contact from at least one object;

encircling the touch pad with a first edge, a second edge, a third edge and fourth edge, wherein the first edge is opposite to the second edge, the third edge is opposite to the fourth edge, and the first edge, the second edge, and the third edge are surfaced with geometric textures;

capturing a first image including the touch point, the second edge and third edge from a first corner between the first edge and the fourth edge;

capturing a second image including the touch point, the first edge and the third edge from a second corner between the second edge and fourth edge; and

performing a characteristic extraction process on the geometric textures of the first and second images to determine coordinates of a touch point where the touch pad is contacted;

wherein the first and second images are one dimensional line images.

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

the object on the touch point is an obstruction that prevents geometric textures on relative locations to be presented on the first and second images;

and the touch point detection method further comprises performing the characteristic extraction process on the geometric textures of the first and second images to identify obstruction locations on the first and second images respectively.

12. The touch point detection method as claimed in claim 11, wherein:

the geometric textures comprise periodic high contrast stripe patterns; and

the characteristic extraction process comprises;

processing the first and second images as a plurality of incremental segments;

detecting edge sum variations between each incremental segment; and

if an edge sum of a particular segment is varied by a rate beyond an expected average value, assessing its corresponding location as being obstructed.

13. The touch point detection method as claimed in claim 11, wherein:

the geometric textures comprise predetermined hue values in the Hue Saturation Lightness (HSL) color space; and

the characteristic extraction process comprises;

processing the first and second images as a plurality of incremental segments;

detecting hue value variations between each adjacent incremental segment; and

if a hue value of a particular segment is varied by a rate beyond an expected average value, assessing its corresponding location as being obstructed.

14. The touch point detection method as claimed in claim 11, further comprising:

determining a first angle indicating a direction from the first corner to the touch point based on an obstructed location on the first image;

determining a second angle indicating a direction from the second corner to the touch point based on an obstructed location on the second image; and

performing a geometric calculation based on the first angle, the second angle, and the width and height of the touch pad to determine the coordinates of the touch point.

15. The touch point detection method as claimed in claim 14, wherein calculation of the first and second angles comprises substituting the obstructed locations into a linear function to determine the first and second angles.

16. The touch point detection method as claimed in claim 15, further comprising performing a calibration process on the touch pad to obtain the linear function, comprising:

receiving contact on each corners of the touch pad, wherein angles of the corners are predetermined known values based on the width and height of the touch pad;

detecting the obstructed locations on the first and second images related to the corners to establish relationships between the known angles and the obstructed locations; and

performing linear interpolation to derive other angle values related to non-corner locations on the first and second images.

17. The touch point detection method as claimed in claim 11, wherein the coordinates is determined according to a look up table and the obstruction locations.