OPTICAL TOUCH SYSTEM, APPARATUS AND METHOD FOR CALCULATING THE POSITION OF AN OBJECT

• US 20110304588A1
• Filed: 01/03/2011
• Published: 12/15/2011
• Est. Priority Date: 06/11/2010
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: PixArt Imaging Incorporated
• Inventors: TSAI, CHENG-NAN, Lin, Chih-Hsin, Su, Tzung-Min
• Granted Patent: US 8,477,119 B2
• Time in Patent Office: Days
• US Class Current: 345/175
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• CPC Class Codes: G06F 2203/04108 Touchless 2D- digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface without distance measurement in the Z direction
• 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

An optical touch system, an apparatus and a method for calculating the position of an object are provided. The apparatus includes an image sensor and a processing circuit. The processing circuit selects at least one dot from a curve segment of a brightness distribution profile obtained from a background image, wherein the curve segment corresponds to an imaging range of an object. And the processing circuit regards the column pixel brightness value corresponding to the dot as a brightness reference value. Afterwards, the processing circuit calculates brightness difference between the brightness reference value and the column pixel brightness values corresponding to the dots of a curve segment of a brightness distribution profile obtained from a sensed image, so as to further calculate a gravity of the imaging range. After that, the processing circuit regards the gravity as a representative position of the object in the sensed image.

Claims

1. An apparatus for calculating the position of an object, the apparatus being suitable for an optical touch system and being provided for determining a representative position of the object in a sensed image, the apparatus comprising:

an image sensor; and

a processing circuit electrically coupled to the image sensor, the processing circuit acquiring a sensed image containing an image of the object through the image sensor, and the processing circuit obtaining brightness value of at least one pixel in each pixel column of the sensed image to obtain a first brightness distribution profile, the processing circuit comparing the first brightness distribution profile with a second brightness distribution profile obtained from a background image, so as to select a plurality of column pixel brightness values in the first brightness distribution profile as an imaging range of the object, the processing circuit selecting column pixel brightness value corresponding to at least one dot from a curve segment of the imaging range in the second brightness distribution profile, so as to regard the selected column pixel brightness value as a brightness reference value, the processing circuit further calculating the brightness difference between the brightness reference value and the column pixel brightness value corresponding to each dot of the curve segment of the imaging range in the first brightness distribution profile, so as to calculate a gravity of the imaging range and to regard the gravity as a representative position of the object in the sensed image.

2. The apparatus as claimed in claim 1, wherein after comparing the first brightness distribution profile and the second brightness distribution profile, the processing circuit regards a distribution range of a plurality of column pixel brightness values in the first brightness distribution profile as the imaging range of the object, there is a brightness difference lager than a predetermined brightness difference between each column pixel brightness value in the distribution range and each column pixel brightness value in a corresponding range in the second brightness distribution profile.

3. The apparatus as claimed in claim 1, wherein the processing circuit acquires the brightness values of the N brightest pixels of each pixel column in the sensed image, so as to calculate an average brightness value or a total brightness value of the selected N brightest pixels in each pixel column to obtain the first brightness distribution profile, wherein N is a natural number, and the background image is an image which is obtained in advance by the processing circuit, and it does not contain any image of the object, the processing circuit also calculates an average brightness value or a total brightness value of the selected N brightest pixels in each pixel column of the background image, so as to obtain the second brightness distribution profile.

4. The apparatus as claimed in claim 1, wherein the processing circuit acquires the brightness values of a plurality of pixels whose brightness values are larger than a predetermined value in each pixel column of the sensed image, so as to calculate an average brightness value of the pixels whose brightness values are larger than the predetermined value in each pixel column to obtain the first brightness distribution profile, and the background image is an image which is obtained in advance by the processing circuit, and it does not contain any image of the object, the processing circuit also calculates an average brightness value of the pixels whose brightness values are larger than the predetermined value in each pixel column of the background image.

5. The apparatus as claimed in claim 1, wherein the processing circuit acquires the column pixel brightness value corresponding to the lowest dot of the curve segment corresponding to the imaging range in the second brightness distribution profile, and the processing circuit regards the acquired column pixel brightness value as the brightness reference value.

6. The apparatus as claimed in claim 1, wherein the image sensor comprises an infra-red illuminating unit and an infra-red filtering unit which only allows infra-red ray to pass through, and the image sensor acquires the sensed image through the infra-red filtering unit.

12. An optical touch system, comprising:

a touch surface used for providing an interactive interface between an object and the optical touch system;

at least two apparatuses as claimed in claim 1, for calculating the representative position of the object sensed by the two apparatuses, the said at least two apparatuses being configured in different places of the touch surface, and the relative position between the said at least two apparatuses and the touch surface being known; and

a coordinates-calculating apparatus used for calculating a relative coordinates of the object on the touch surface in accordance with the relative position between the said at least two apparatuses and the touch surface and the representative positions of the object sensed by the said at least two apparatuses.

13. An optical touch system, comprising:

a touch surface used for providing an interactive interface between an object and the optical touch system;

a mirror element used for forming a mirror image of the touch surface;

an apparatus as claimed in claim 1, for calculating a representative position of the object sensed by the apparatus and for calculating a representative position of a virtual object formed in the mirror image, wherein the relative position between the apparatus and the touch surface is known, and the apparatus and the mirror element are configured on two opposite sides of the touch surface; and

a coordinates-calculating apparatus used for calculating a relative coordinates of the object on the touch surface in accordance with the relative position between the apparatus and the touch surface and the representative positions of the object and the virtual object sensed by the apparatus.

7. A method for calculating the position of an object, the method being used for an optical touch system and being provided for determining a representative position of the object in an sensed image, the method comprising the steps of:

acquiring a brightness value of at least a pixel in each pixel column of the sensed image containing an image of the object to obtain a first brightness distribution profile;

comparing the first brightness distribution profile with a second brightness distribution profile obtained from a background image, so as to select a plurality of column pixel brightness values in the first brightness distribution profile as an imaging range of the object;

selecting a column pixel brightness value corresponding to at least one dot from a curve segment of the imaging range in the second brightness distribution profile, so as to regard the selected column pixel brightness value as a brightness reference value; and

calculating the brightness difference between the brightness reference value and the column pixel brightness value corresponding to each dot of the curve segment of the imaging range in the first brightness distribution profile, so as to calculate a gravity of the imaging range and to regard the gravity as a representative position of the object in the sensed image.

8. The method as claimed in claim 7, wherein after comparing the first brightness distribution profile and the second brightness distribution profile, a distribution range of a plurality of column pixel brightness values in the first brightness distribution profile is regarded as the imaging range of the object, wherein there is a brightness difference lager than a predetermined brightness difference between each column pixel brightness value in the distribution range and each column pixel brightness value in a corresponding range in the second brightness distribution profile.

9. The method as claimed in claim 7, wherein the brightness values of the N brightest pixels of each pixel column in the sensed image are acquired, so as to calculate an average brightness value or a total brightness value of the selected N brightest pixels in each pixel column to obtain the first brightness distribution profile, wherein N is a natural number, the background image is an image which is obtained in advance, and it does not contain any image of the object, and an average brightness value or an total brightness value of the selected N brightest pixels in each pixel column of the background image is also calculated, so as to obtain the second brightness distribution profile.

10. The method as claimed in claim 7, wherein the brightness values of a plurality of pixels whose brightness values are larger than a predetermined value in each pixel column of the sensed image are acquired, so as to calculate an average brightness value of the plurality of pixels of each pixel column to obtain the first brightness distribution profile, the background image is an image which is obtained in advance, and it does not contain any image of the object, and an average brightness value of the pixels whose brightness values are larger than the predetermined value in each pixel column of the background image is calculated, so as to obtain the second brightness distribution profile.

11. The method as claimed in claim 7, wherein a column pixel brightness value corresponding to the lowest dot of the curve segment corresponding to the imaging range in the second brightness distribution profile is regarded as the brightness reference value.