Optical touch panel and coordinate information correction method and detecting device therefor

This application claims priority of Taiwanese Application No. 099126915, filed on Aug. 12, 2010.

1. Field of the Invention

The present invention relates to a correction method for a touch panel, more particularly to a coordinate information correction method for an optical touch panel.

2. Description of the Related Art

Conventional touch panels include resistive touch panels, capacitive touch panels, and optical touch panels. The resistive touch panel, compared to the capacitive touch panel, is less expensive but has a slower response.

One example of an optical touch panel uses an infrared LED module, which emits infrared beams, and photodetector pairs around a periphery of the touch panel for detecting an interruption in a pattern of the infrared beams. Another optical touch panel uses an infrared backlight module and at least two image sensors (CCD or CMOS sensor elements) placed around the periphery of the touch panel for detecting a shadow, which is produced by an object approaching the touch panel, in a light curtain region defined by the infrared backlight module so as to locate the object.

A conventional optical touch panel disclosed in U.S. Patent Application Publication No. 2009/0146972 teaches the use of a processor to determine distortion parameters of lenses during calibration for correcting pointer coordinate data associated with a position of the pointer relative to a touch surface. Since the techniques proposed therein adopt nonlinear equations, the solutions obtained are only approximations, and the calculations involved are relatively complicated.

Therefore, an object of the present invention is to provide a coordinate information correction method which is applied to an optical touch panel, and which permits correction of different kinds of distortion of the optical touch panel by calculating relatively simple equations.

Accordingly, a coordinate information correction method of this invention is for an optical touch panel that includes a touch surface, a light source module, at least two light detectors, and a processor. The light source module is disposed to define a light curtain region on one side of the touch surface. The at least two light detectors are disposed at at least one edge of a periphery of the touch surface, and are spaced apart from each other. Each of the light detectors has a field of detection along the touch surface. The light detectors are arranged in a manner that at least portions of the fields of detection of the light detectors overlap with each other and that the light detectors are able to detect changes in intensity of the light received from the light source module that are produced as a result of the presence of an object in the light curtain region. The processor receives output signals from the at least light detectors.

The coordinate information correction method comprises:

a) determining, using the processor, a set of to-be-corrected included angle values according to the output signals, each of the to-be-corrected including angle values representing an included angle between a base line and a connecting line that extends from a respective one of the light detectors to a location of the object in the light curtain region; b) calculating, using the processor, a set correction values, each of which is a finite order function of a respective one of the to-be-corrected included angle values; c) calculating, using the processor, a set of corrected included angle values from the set of to-be-corrected included angle values and the set of correction values; and d) generating, using the processor, corrected coordinate information associated with the location of the object in the light curtain region from the corrected included angle values.

Preferably, in step b), the processor is configured calculate the set of correction values (Δα 1 , Δα 2 , . . . Δα k ) according to the following equation

Δ ⁢ ⁢ α j = A j ⁢ ⁢ o + ∑ i = 1 n ⁢ A ji ⁡ ( α j ⁢ ⁢ _ ⁢ ⁢ act ) i , j = 1 ∼ k , n ≥ 1 ,

in which k represents a total number of the light detectors in the optical touch panel, j represents a jth one of the light detectors, i is a power of the equation, A jo ˜A ji are predetermined correction coefficients, and α j — net is the to-be-corrected included angle value corresponding to the jth one of the light detectors.

Preferably, in step c), the processor is configured to calculate a jth one of the corrected included angle values (α 1 — cor , α 2 — cor , . . . α k — cor ) as a difference between the jth one of the to-be-corrected included angle values and the jth one of the correction values.

Preferably, for each of the light detectors, the connecting line is a line passing through a lens of the light detector and the location of the object in the light curtain region, and the base line passes through the lens of the light detector.

Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which:

FIG. 1 is a schematic diagram illustrating a preferred embodiment of an optical touch panel of the present invention;

FIG. 2 is a flowchart illustrating a coordinate information correction method for the optical touch panel of FIG. 1 ;

FIG. 3 is a schematic diagram, illustrating a field of detection of one light detector of a detecting device of the preferred embodiment; and

FIG. 4 is a schematic diagram, illustrating a field of detection of another light detector of the detecting device of the preferred embodiment.

Referring to FIG. 1 , a preferred embodiment of an optical touch panel 100 according to the present invention includes a touch surface 10 , which is generally a planar surface, for contact with an object 9 , a light source module, and a detecting device 2 . The light source module is disposed to define a light curtain region on one side of the touch surface 10 , and includes a plurality of light sources 12 for emitting invisible light, for example infrared LEDs, and a plurality light guides 13 for uniformly distributing the light emitted from the light sources 12 across the side of the touch surface 10 . The touch surface 10 is substantially rectangular in shape and has a length L and a width W.

The detecting device 2 includes two light detectors 3 , and a processor 20 . The light detectors 3 are disposed respectively adjacent to a first corner and a second corner, wherein the first corner and the second corner are located at two ends of a long edge of the touch surface 10 . Each of light detectors 3 includes a sensor 32 , a lens 30 , and an optical filter 34 . The optical filters 34 have a light filtering capability such that only light of a specific wavelength is able to pass therethrough and reach the sensors 32 for subsequent detection thereby, thus obtaining more accurate detection results.

Referring to FIG. 3 and FIG. 4 , each of the light detectors 3 has a field of detection along the touch surface 10 . The light detectors 3 are arranged in a manner that at least portions of the fields of detection of the light detectors 3 overlap with each other and that the light detectors 3 are able to detect changes in intensity of the light received from the light source module. Specifically, each of the light detectors 3 is disposed at a distance h from said long edge of the touch surface 10 . The touch surface 10 has a monitoring field ACD. Referring to FIG. 3 , the light detector 3 near the first corner, which is at a point A, has the field of detection A′BCD that is able to cover the monitoring field ABCD. Furthermore, referring to FIG. 4 , the light detector 3 near the second corner, which is at a point B, has the field of detection AB′CD that is able to cover the monitoring field ABCD.

Referring to FIG. 1 , each of the sensors 32 may be a linear sensor or an array sensor, and has sensing elements (not shown) for generating output signals, from which information about included angle values may be obtained. In particular, the output signals represent the changes in intensity of the light received from the light source module that are produced as a result of the presence of the object 9 in the light curtain region, and each of the included angle values represents an included angle between a base line (P) and a connecting line that extends from a respective one of the light detectors 3 to a location of the object 9 in the light curtain region.

Moreover, each connecting line is a line passing through the lens 30 of the respective light detector 3 and the location of the object 9 in the light curtain region, and the base line (P) passes through the lenses 30 of the two light detectors 3 in this embodiment.

Furthermore, each sensing element of the sensors 32 is associated with a corresponding detection angle for detecting the changes in light intensity along an extension line at the corresponding detection angle. For example, referring once again to FIG. 3 , the changes in intensity of the light along a connecting line from A to D may be detected by a corresponding sensing element, which has the corresponding detection angle at 90 degrees, located at an edge 320 of the sensor 32 near the first corner.

Referring to FIG. 1 and FIG. 2 , the processor 20 is connected to the two light detectors 3 . A coordinate information correction method is performed by the detecting device 2 and comprises the steps of:

S 1 ) generating, using the light detectors 3 , the output signals indicative of the changes in intensity of the light received from the light source module; S 2 ) determining, using the processor 20 , a set of to-be-corrected included angle values according to the output signals received from the light detectors 3 , i.e., an angle value α 1 — act represents the included angle between the base line (Pi that passes through the light detector 3 near the first corner and the connecting line that extends from said light detector 3 to the location of the object 9 ; similarly, another angle value α 2 — act represents the included angle between the base line (P) and the connecting line that extends from the light detectors 3 near the second corner to the location of the object 9 may be detected. The angle value (α 1 — act , α 2 — act ) are defined as the to-be-corrected angle values; S 3 ) calculating, using the processor 20 , a set of correction values (Δα 1 , Δα 2 ), each of which is a finite order function of a respective one of the to-be-corrected included angle values (α 1 — act , α 2 — act ), according to the following equation

in which k represents a total number of the light detectors 3 in the optical touch panel 100 , j represents a jth one of the light detectors 3 , i is a power of the equation, A jo ˜A ji are correction coefficients, and α j — act is the to-be-corrected included angle value corresponding to the jth one of the light detectors 3 . In this embodiment, n=5, and Δα j is thus a fifth order function of α j — act . The correction coefficients A jo ˜A ji , are predetermined using regression algorithms according to sampling points with known coordinates. For example, the L×W touch surface 10 is divided into a 5×5 grid having 36 grid points (inclusive of boundary points), and each of the grid points has a set of known included angle values (α 1 — ref , α 2 — ref ). During a calibration process, the detecting device 2 detects the presence of an object, such as a touch pen, at each of the grid points in the light curtain region, and generates a respective one of a set of calibration included angle values (α 1 — cal , α 2 — cal ) which may be represented by the following two equations

α 1 — cal =A 10 +A 11 α 1 — ref +A 12 α 1 — ref 2 +A 13 α 1 — ref 3 +A 14 α 1 — ref 4 +A 15 α 1 — ref 5 ′

α 2 — cal =A 20 +A 21 α 2 — ref +A 22 α 2 — ref 2 +A 23 α 2 — ref 3 +A 24 α 2 — ref 4 +A 25 α 2 — ref 5 ′

Regression algorithms are used to find A 10 ˜A 15 and A 20 ˜A 25 that would make a summation of |α 1 — cal −α 1 — ref | obtained for each of the grid points and a summation of |α 2 — cal −α 2 — ref | obtained for each of the grid points reach minimum values. The A 10 ˜A 15 and A 20 ˜A 25 thus found are the correction coefficients in the step S 3 );

S 4 ) calculating, using the processor 20 , a set of corrected included angle values (α 1 — cor , α 2 — cor ) from the set of to-be-corrected included angle values (α 1 — act , α 2 — act ) and the set of correction values (Δα 1 , Δα 2 according to the following equations

α 1 — cor =α 1 — net −Δα 1 ,

α 2 — cor =α 2 — act −Δα 2 ; and

S 5 ) generating, using the processor 20 , corrected coordinate information associated with the location of the object 9 in the light curtain region from the corrected included angle values (α 1 — cor , α 2 — cor ) by using triangulation computations.

In this way, when the optical touch panel 100 has input from the object 9 , the optical touch panel 100 may detect, calculate and generate corrected coordinate information associated with the location of the object 9 , such that the response of the optical touch panel 100 corresponds correctly to the input.

Moreover, numbers and placement positions of the light detectors 3 are not limited to the closure this embodiment, as long as the light detectors 3 are not less than two in number, and any adjacent two of which are disposed at a periphery of the touch surface 10 and are spaced apart from each other. The processor 20 may process the output signals received from any of the light detectors 3 using the same coordinate information correction method.

In summary, the optical touch panel 100 of the present invention may correct deviation angles first, and then generate coordinate information from the corrected angle values. The technique utilized by the present invention may replace a conventional correction method, which requires complicated calculations to obtain rectangular coordinates. Furthermore, deviation errors may be corrected regardless of what components the deviation errors attributed to.

While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.