# Patent

## Title
Optical touch display system

## Abstract

Optical touch display system includes a light source, a reflector, an image sensor, and a processing device. The light source emits light to at least one object directly and emits light to the at least one object via the reflector at the same time. Then the image sensor receives light reflected from the at least one object directly and light reflected via the reflector simultaneously to form a set of imaging objects which have similar color parameters on an image. Then the processing device produces a set of still image parameters of the image objects such as gravity centers and border boundaries. Based on the still image parameters, the processing device determines the coordinates of the least one object on the optical touch display.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. application Ser. No. 12/817,172, filed on Jun. 16, 2010, entitled “Distance-measuring device, 3D image-sensing device, and optical touch system” and No. 12/842,045, filed on Jul. 23, 2010, entitled “Distance-measuring device of measuring distance according to variation of imaging location and calibrating method thereof”, the contents of which are incorporated herein in their entirety.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to an optical touch display system, and more particularly, to an optical touch display system for multiple touch points.
2. Description of the Prior Art
Modern touch display technologies are already widely applied in electronic products of all kinds, e.g. Automated Teller Machine (ATM), handheld electronic devices and display devices. Generally, touch display technologies can be found in three types: resistive, capacitative and optical, wherein resistive and capacitative touch displays position an object via detecting variations in electric fields on surfaces of the touch displays when the object comes in contact with a sensing device. On the other hand, an optical touch display positions an object by detecting interruptions in light paths or light variations caused by the object moving on the surface of the touch display.
Since touch devices utilizing optical touch display technologies do not require special manufacturing processes or components, and also manufacturing costs are little affected by dimensions, optical touch technology is a more cost-effective solution than resistive and capacitative touch displays for larger-scale applications. To achieve a light-weight structure, optical touch display technologies often dispose image sensors at corners of touch screens and utilize triangulation to determine coordinates of a touch object from different angles. However, for two or more touch objects, measurement accuracy is reduced due to shadowing and obstruction of light paths, resulting in less accurate or incorrect coordinates (ghost coordinates), causing inconvenience for various applications.
SUMMARY OF THE INVENTION
The present invention discloses an optical touch display system. The optical touch display system comprises a touch region; a light source, disposed on a periphery of the touch region, the light source positioned at least partially above the touch region, such that light rays emitted from the light source may traverse the touch region; a reflector, disposed on at least a part of the periphery of the touch region, for reflecting the light rays emitted from the light source and generating a mirrored image of the touch region; an image sensor, disposed above the light source, for receiving light rays of the light source, reflected from a set of touch points on the touch region and the reflector, and generating a two-dimensional image accordingly; wherein the two-dimensional image comprises a set of optical images, the set of optical images comprising a set of real images corresponding to the set of touch points, and a set of virtual images corresponding to the set of touch points, generated by the light rays from the light source reflected by the reflector; and a processing device, for generating a set of output coordinates corresponding to the set of touch points according to positions of the set of real images and the set of virtual images in the two-dimensional image.
The present invention further discloses an optical touch display system. The optical touch display system comprises a touch region; a light source, on a periphery of the touch region, the light source positioned at least partially above the touch region, such that light rays emitted from the light source may traverse the touch region; an image sensor, disposed above the light source, for receiving light rays of the light source, reflected from a set of touch points on the touch region, and generating a two-dimensional image accordingly; wherein the two-dimensional image comprises a set of optical images corresponding to the set of touch points; a distance measurement device, connected to the light source and the image sensor, for controlling the light source and the image sensor, and generating a set of image distances corresponding to the set of optical images according to coordinates of the set of optical images in the two-dimensional image along a first direction; an angle measurement device, connected to the image sensor, for generating a set of image angles corresponding to the set of optical images according to coordinates of the set of optical images in the two-dimensional image along a second direction; and a processor, for generating a set of output coordinates according to the set of image distances and the set of image angles.
The present invention further discloses an optical touch display system. The optical touch display system comprises a touch region; a light source, disposed on a periphery of the touch region, the light source positioned at least partially above the touch region, such that light rays emitted from the light source may traverse the touch region; a first image sensor, disposed above the light source, for receiving light rays of the light source, reflected from a set of touch points on the touch region, and generating a first two-dimensional image accordingly; wherein the first two-dimensional image comprises a first set of real images corresponding to the set of touch points; a second image sensor, disposed on the periphery of the touch region, for receiving light rays of the light source, reflected from the set of touch points on the touch region, and generating a second two-dimensional image accordingly; wherein the second two-dimensional image comprises a second set of real images corresponding to the set of touch points; a distance measurement device, connected to the light source and the first image sensor, for controlling the first image sensor and the light source, and generating a first set of image distances corresponding to the first set of real images according to coordinates of the first set of real images in the two-dimensional image along a first direction; and a processor, for generating a first set of real-image lines according to the first set of real images and a position of the first image sensor in the first two-dimensional image, and generating a second set of real-image lines according to the second set of real images and a position of the second image sensor in the second two-dimensional image, and the processing device generates a set of candidate coordinates corresponding to the set of touch points according to the first set of real-image lines and the second set of real-image lines, and generates a set of output coordinates corresponding to the set of touch points according to the set of candidate coordinates and the first set of image distances.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of an optical touch display system according to a first embodiment of the present invention.
FIG. 2 is a schematic diagram of the optical touch display system during a calibration stage according to the first embodiment of the present invention.
FIG. 3 is a schematic diagram the optical touch display system under normal operation according to the first embodiment of the present invention.
FIG. 4 is a side-view schematic diagram of the optical touch display system according to the first embodiment of the present invention.
FIG. 5 is a top-view schematic diagram of the optical touch display system according to the first embodiment of the present invention.
FIG. 6 is a schematic diagram of an optical touch display system according to a second embodiment of the present invention.
FIG. 7 is a flowchart of a process of the optical touch display system detecting a touch point position according to the second embodiment of the present invention.
FIGS. 8-12 are schematic diagrams illustrating the process shown in FIG. 7.
FIG. 13 is a schematic diagram of an optical touch display system according to a third embodiment of the present invention.
FIG. 14 is a flowchart of a process of the optical touch display system detecting a touch point position according to the third embodiment of the present invention.
FIG. 15 is a schematic diagram illustrating the process shown in FIG. 14.
FIGS. 16 and 17 are schematic diagrams illustrating structure and operation of a distance measurement device according to the present invention.



DETAILED DESCRIPTION
Please refer to FIG. 1, which is a schematic diagram of an optical touch display system 100 according to a first embodiment of the present invention. The optical touch display system 100 includes an image sensor 101, a light source 102, a touch region 103, a light absorption component 104, and a processing device 120. The processing device 120 includes a distance measurement device 105, an angle measurement device 106, and a processor 107. The optical touch display system 100 is capable of detecting multiple touch points. Moreover, the distance measurement device 105 further controls the image sensor 101 and the light source 102 via a control signal SC. In FIG. 1, only two touch points O1, O2 are shown for illustrative purposes. Moreover, relative positions of components in FIG. 1 are shown for illustration, and in reality the components may be disposed differently. In reality, a lens LN is disposed on a sensing side of the image sensor 101 in the optical touch display system 100, such that all incident light rays to the image sensor 101 pass through the lens LN. However, the lens LN is omitted from FIG. 1 for simplicity.
Preferably, the touch region 103 is set to a rectangle, and the light absorption component 104 is disposed on a periphery of the touch region 103, for absorbing light rays of the light source 102 such that light rays of the light source 102 are not reflected back to the image sensor 101. However, the touch region 103 can also be set to a trapezoid, or other polygonal shapes, according to user requirements. The light source 102 is disposed on the periphery of the touch region 103; preferably, the light source 102 is positioned at least partially above a corner of the touch region touch region 103, such that light rays emitted from the light source 102 may traverse the touch region 103. The image sensor 101 is disposed close to the light source 102; preferably, the image sensor 101 is disposed above the light source 102. Moreover, the light source 102 may be a two-dimensional light source, including a linear light source and a light source conversion device, wherein the linear light source is generated via a laser diode or a Light Emitting Diode (LED); the light source conversion device converts the linear light source to the two-dimensional light source, to generate light rays on the touch region 103; the light source conversion device may be a cylindrical lens, a Diffractive Optical Element (DOE) or a MEMS micro mirror module.
The image sensor 101 contains a light sensing array constituted from M columns and N rows of sensing units, and generates a two-dimensional image F with a resolution of M by N. More specifically, in Cartesian coordinates, the two-dimensional image F has a resolution of M along an X-axis and a resolution of N along a Y-axis.
In one embodiment, the present invention employs a polar coordinate system for the touch region 103. As shown in FIG. 1, the origin (0,0) of the polar coordinate system is defined as a top-left corner of the touch region 103, and the polar axis is defined as a top boundary of the touch region 103. Preferably, the image sensor 101 is disposed at the top-left corner of the touch region, i.e. polar coordinates of the image sensor 101 is also the origin (0,0); the light source 102 is also disposed at the top-left corner of the touch region, i.e. polar coordinates of the light source 102 is also the origin (0,0). Therefore, a position of an object on the touch region 103 is represented by a distance R from the top-left corner of the touch region 103, and an angle θ from the top boundary of the touch region 103.
The distance measurement device 105 and the angle measurement device 106 measures an image distance and image angle of the touch point according to positions of an optical image generated by light rays reflected from the touch point in the two-dimensional image F. More specifically, the distance measurement device 105 calculates the distance of the touch point according to a position of the optical image in the two-dimensional image F along the Y-axis; the angle measurement device 106 calculates the angle of the touch point according to a position of the optical image in the two-dimensional image F along the X-axis. The processing device 107 further outputs the position of the touch point (in distance and angle) according to information obtained by the distance measurement device 105 and the angle measurement device 106.
Please refer to FIG. 2, which is a schematic diagram illustrating the optical touch display system 100 during a calibration stage. Before starting to detect the position of the touch point, the optical touch display system 100 may first undergo a calibration stage. The following illustrates operations of the optical touch display system 100 of the present invention during the calibration stage. For the same illustrative purposes, the lens LN is omitted from FIG. 2.
During the calibration stage, calibration objects P1, P2, P3, P4 can be disposed at each of four corners of the touch region 103, corresponding to coordinates (RP1, θP1), (RP2, θP2), (RP3, θP3), (RP4, θP4), respectively. The light source 102 emits light rays at the calibration objects P1, P2, P3, and P4, respectively; the calibration objects P1, P2, P3, and P4 reflect the light rays from the light source 102 to the image sensor 101. Here, it is assumed that the calibration objects P1, P2, P3, P4 respectively form images on the sensing units CS(M, 0), CS(M,N), CS(0,N), CS(0,0) (assumed for illustrative purposes only, and may differ in reality). In other words, coordinates of optical images IP1, IP2, IP3, IP4 corresponding to the calibration objects P1, P2, P3, P4 on the two-dimensional image F are (M,0), (M,N), (0,N), (0,0), respectively. Since that the calibration objects P1 ̃P4 are disposed at corners of the touch region, and that a length and width of the touch region 103 are both known, and providing that the origin (0,0) is defined as the top-left corner of the touch region, it follows that (RP1, θP1), (RP2, θP2), (RP3, θP3), (RP4, θP4) may be mathematically determined. For example, assuming the length and width of the touch region 103 are RL and WL, then (RP1, θP1), (RP2, θP2), (RP3, θP3), (RP4, θP4) may be expressed (0,0), (RL,0), ((RL2+WL2)1/2, tan−1(WL/RL)), (WL, 90°), respectively. As such, in the case of the calibration objects P3 and P4, the distance measurement device 105 can know that a distance difference of N along the Y-axis in the two-dimensional image F is equivalent to a distance difference of WL in actual space. Thus, a distance of an object from the origin on the touch region 103 may be derived, via interpolation, from a position of a corresponding optical image along the Y-axis in the two-dimensional image F. In the case of the calibration objects P1 and P3, the angle measurement device 106 knows that a distance difference of M along the X-axis in the two-dimensional image F is equivalent to an actual angle difference of 90°. Thus, an angle of an object from the polar axis on the touch region 103 may be derived from a position of a corresponding optical image along the X-axis in the two-dimensional image F, via interpolation. Moreover, in the above-mentioned calibration method, different variations according to user requirements are possible, e.g. different positions or a different quantity of the calibration objects, etc.
Please refer to FIG. 3, which is a schematic diagram of the optical touch display system 100 during normal operation according to the present invention. During normal operation, the light source 102 emits the light rays to the touch point O1; the touch point O1 reflects the light rays emitted from the light source 102 back to the image sensor 101, and an image is formed on the sensing unit CS(X1,Y1). In other words, the touch point O1 corresponds to an optical image IO1 with coordinates (X1,Y1) in the two-dimensional image F. Since the coordinate relationship between the touch region 103 and the two-dimensional image F can be known by the distance measurement device 105 and the angle measurement device 106 after the calibration stage, it is possible to calculate that a position of the touch point O1 in the touch region 103 is at (RO1, θO1). A position of the touch point O2 may be calculated in a way similarly to the touch point O1, and not further described herein.
Please refer to FIG. 4, which is a side-view schematic diagram of the optical touch display system 100. FIG. 4 illustrates how the distance measurement device 105 measures the distance R, and uses the calibration objects P1, P2 and the touch point OT as an example. Furthermore, the lens LN shown in FIG. 4 illustrates that all inflecting light rays of the image sensor 101 pass through the lens LN, therefore resulting in image positions as shown in FIG. 4. It may be assumed that the calibration objects P1 and P2 are spaced apart by a known distance RL, and correspond to optical images IP1 and IP2 in the two-dimensional image F, with coordinates (M,N) and (M,0), respectively. It follows that, ROT, a distance of the touch point OT to be detected by the distance measurement device 105, may be derived from a position of an optical image IOT (corresponding to the touch point OT) relative to the optical images IP1, IP2 along the Y-axis in the two-dimensional image F. More specifically, suppose the optical image IOT is at (XT, YT), then the distance ROT may be expressed as follows: ROT=(YT/N)×RL.
Please refer to FIG. 5, which is a top-view of the optical touch display system 100. FIG. 5 illustrates how the angle measurement device 106 measures the angle θ, using the calibration objects P2, P3 as an example. Assume that an angle ΘP3 between the calibration objects P2 and P3 is known (e.g. tan−1(WL/RL)), and that the calibration objects P2 and P3 correspond to optical images IP2 and IP3, at positions (M,N) and (0,N), respectively. It follows that the angle θOT of the touch point OT to be detected by the angle measurement device 106 may be derived from the position of the optical image IOT relative to the optical images IP2 and IP3 along the X-axis in the two-dimensional image F. More specifically, suppose the optical image IOT is at (XT, YT), then the angle θOT may be expressed by the following: θOT=(XT/M)×θP3.
Please refer to FIG. 6, which is a schematic diagram of an optical touch display system 600 according to a second embodiment of the present invention. Compared with the optical touch display system 100, the optical touch display system 600 is configured with an extra reflector 108, for enhancing accuracy of determining positions of the touch points. Furthermore, the processing device 120 of the optical touch display system 600 may optionally include a real image determination device 170. In the following, it is assumed that it is known whether the optical images in the two-dimensional image F are real images or not. Moreover, those skilled in the art may derive other cases according to the aforementioned relationship between positions of an object in the touch region and its corresponding optical image in the two-dimensional image. Therefore, for illustrative purposes, the following mainly describes positions of objects within the touch region.
Please refer to FIG. 7, which is a flowchart of a process illustrating the optical touch display system 600 detecting the position of the touch point. For simplicity, the following describes a case with two touch points O1, O2. Moreover, steps disclosed in FIG. 7 merely serve illustrative purposes. In practice, operations do not need to follow the steps as disclosed in FIG. 7. The steps of the process are as follows:
Step 701: The light source 102 emits light rays, and generate optical images IO1, IO2, IO1J, IO2J in the two-dimensional image F via reflections of the touch points O1, O2, and the reflector, wherein IO1J and IO2J are mirrored images (virtual images) of the touch points O1 and O2, respectively; refer to FIG. 8; dashed-lined areas in FIG. 8 represent mirrored images produced by the reflector 108 reflecting the light rays of the light source 102, wherein the touch points O1, O2 correspond to mirrored images O1J and O2J, respectively. Therefore, the image sensor 101 sees four optical images IO1, IO2, IO1J and IO2J, wherein O1J and O2J are virtual images, as shown by the two-dimensional image F in FIG. 8.
Step 702: The angle measurement device 106 generates image angles θO1, θO2, θO1J, and θO2J according to positions of the optical images IO1, IO2, IO1J, and IO2J along the X-axis in the two-dimensional image F. Please refer to FIG. 9A.
Step 703: Using the light source 102 as an origin, the processing device 107 generates real-image lines SLO1 and SLO2, and virtual-image lines SLO1J, SLO2J according to the image angles θO1, θO2, θO1J, θO2J, respectively; please refer to FIG. 9B.
Step 704: The processing device 107 calculates intersection points G1, G2 at which the virtual-image lines SLO1J and SLO2J intersect a plane on which the reflector 108 is disposed; the processing device 107 generates virtual-image lines SLG1 and SLG2 according to a mirrored image 101J of the image sensor 101 (or a mirrored image 102J of the light source 102), and the intersection points G1, G2; please refer to FIG. 10.
Step 705: The processing device 107 calculates and generates four candidate coordinates OC1, OC2, OC3 and OC4 according to the real-image lines SLO1, SLO2 and the virtual-image lines SLG1, SLG2; please refer to FIG. 11.
Step 706: The distance measurement device 105 generates image distances RO1, RO2 according to positions of the optical images IO1, IO2 along the Y-axis in the two-dimensional image F; please refer to FIG. 12A.
Step 707: The processing device 107 selects a candidate coordinate on the real-image line SLO1 having a minimum deviation from the image distance RO1 as an output coordinate for the touch point O1; please refer to FIG. 12B; the processing device 107 selects a candidate coordinate on the real-image line SLO2 having a minimum deviation from the image distance RO2, as an output coordinate for the touch point O2; please refer to FIG. 12B.
As can be seen from the above, the optical touch display system 600 may first measure the image angle via the image sensor 101 and the reflector 108, then determine the coordinate with minimum deviation within the candidate coordinates according to the distance measured by the distance measurement device 105, and then output the coordinate as the final output coordinate of the touch point.
Moreover, the image distance measured by the measurement device 105 can only be used in steps 707, 708 to determine the output coordinates within the candidate coordinates; therefore, extremely high measurement accuracy for the image distance is not required. In reality, the output coordinates of the touch points may still be calculated and decided by the processing device 107 using the measured angle.
Furthermore, the real image determination device 170 determines whether the optical images on the image sensor 101 corresponding to the optical images in the touch region are real images or virtual images. More specifically, the real image determination device 170 is capable of determining whether an optical image X is a real image, according to whether a measured image distance RX and image angle θX of the optical image X satisfies a predefined relationship. For example, the optical image X is determined to be a real image if the predefined relationship between the image distance RX and the image angle θX is satisfied, such that coordinates of the optical image X fall within a range of the touch region 103. Conversely, the optical image X is determined as a virtual image.
Please refer to FIG. 13, which is a schematic diagram of an optical touch display system 1300 according a third embodiment of the present invention. Compared with the optical touch display system 100, the optical touch display system 1300 is configured with an extra image sensor 109 with functionalities similar to that of the reflector 108, mainly for enhancing accuracy of determining the positions of the touch points. Preferably, the image sensor 109 may be disposed at the top-right corner of the touch region 103. Operations of the optical touch display system 1300 are similar to that of the optical touch display system 600, and details of which are provided in the following.
Please refer to FIGS. 14 and 15. FIG. 14 illustrates a process through which the optical touch display system 1300 detects a position of a touch point. FIG. 15 is a schematic diagram illustrating the process shown in FIG. 14. Moreover, steps of the process disclosed in FIG. 14 merely serve illustrative purposes. In practice, operations do not need to follow the process disclosed in FIG. 14. The steps of the process are as follows:
Step 1401: The light source 102 emits light rays, which are reflected by the touch points O1 and O2; optical images IO11, IO21 are generated in the two-dimensional image F1 sensed by the image sensor 101, and optical images IO19, IO29 are also generated in the two-dimensional image F2 sensed by the image sensor 109.
Step 1402: The angle measurement device 106 generates image angles θO11, θO21, θO19, and θO29 according to positions of the optical images IO11, IO21 along the X-axis in the two-dimensional image F1, and according to positions of the optical images IO19, IO29 along the X-axis direction in the two-dimensional image F2, respectively; note that the image sensor 109 is the origin for the angles θO19, θO29.
Step 1403: Using position of the image sensor 101 as origin, the processing device 107 generates real-image lines SLO11 and SLO21, according to the image angles θO11, θO21, respectively; and then using position of the image sensor 109 as an origin, the processing device 107 generates real-image lines SLO19 and SLO29 according to the image angles θO19, θO29, respectively.
Step 1404: Next, the processor 107 calculates intersections of the real-image lines SLO11, SLO21, SLO19, SLO29 and virtual-image lines SLG1, SLG2, to calculate and generate four candidate coordinates OC1, OC2, OC3 and OC4.
Step 1405: The distance measurement device 105 generates image distances RO11, RO21 according to positions of the optical images IO11, IO21 along the Y-axis in the two-dimensional image F1.
Step 1406: The processor 107 selects a candidate coordinate on the real-image line SLO11 having minimum deviation from the image distance RO11 as an output coordinate for the touch point O1; the processor 107 selects a candidate coordinate on the real-image line SLO21 having minimum deviation from the image distance RO21 as an output coordinate for the touch point O2.
As can be seen from the above, the optical touch display system 1300 may first measure the image angles via the image sensors 101 and 109, then determine the coordinate within the candidate coordinates with minimum deviation according to the distance measured by the distance measurement device 105, and then output the coordinate as the final output coordinate of the touch point.
Moreover, the image distance measured by the measurement device 105 can only be used in steps 1407, 1408 to determine the output coordinates within the candidate coordinates; therefore, extremely high measurement accuracy for the image distance is not required. In reality, the output coordinates of the touch points may still be calculated and decided by the processing device 107 using the measured angles.
Please refer to FIGS. 16 and 17, which are schematic diagrams illustrating structure and operations of the distance measurement device 105 according to the present invention. Disposed as shown in FIG. 1, the distance measurement device 105 measures the image distance RO1 between the touch point O1 and the light source 102. The distance measurement device 105 includes a lighting/sensing control circuit 110 and a distance calculation circuit 140. The lighting/sensing control circuit 110 generates a control signal SC to control the light source 102 and the image sensor 101. Connections of internal components in the distance measurement device 105 are shown in FIG. 1, and not reiterated herein. Moreover, to enhance accuracy, it is possible to further dispose lenses LEN1 and LEN2 in front of the image sensor 101 and the light source 102, respectively.
The control signal SC generated by the lighting/sensing control circuit 110 includes a light pulse signal SLD, a shutter pulse signal SST, phase signal SP, read signal SRE, and known distance signal SD. Distance measurement performed by the distance measurement device 105 may be divided into two stages: 1. Distance sensing stage; and 2. Noise sensing stage. During the distance sensing stage, the lighting/sensing control circuit 110 of the distance measurement device 105 simultaneously generates the light pulse signal SLD representing “lit” and the shutter pulse signal SST representing “open”, both with a pulse width of TC; then the lighting/sensing control circuit 110 simultaneously generates the read signal SRE representing “read” and the phase signal Sp representing “sum”, both with a pulse width of TR. When the distance measurement device 105 is in the noise sensing stage, the lighting/sensing control circuit 110 generate the shutter pulse signal SST representing “open” and simultaneously, the light pulse signal SLD representing “unlit”, and the shutter pulse signal has a pulse width of TC; then the lighting/sensing control circuit 110 simultaneously generates the read signal SRE representing “read” and the phase signal Sp representing “noise”, both with a pulse width of TR.
The light source 102 is controlled by the lighting/sensing control circuit 110, and used for emitting a detecting light ray LID to the touch point O1 according to the light pulse signal SLD, such that the touch point O1 generates a reflecting light ray LRD. More specifically, when the light pulse signal SLD represents “lit”, the light source 102 emits the detection light ray LID to the touch point O1; when the light pulse signal SLD represents “unlit”, the light source 102 does not emit the detection light ray LID.
Take a column of the image sensor 101 as an example, e.g. a Q-th sensing column CSQ includes N sensing units CS(Q,1) ̃CS(Q,N) set side-by-side, each sensing unit having a height equal to a pixel height HPIX, i.e. the N sensing units CS(Q,1) ̃CS(Q,N) set side-by-side measure a total width of N×HPix. The sensing units CS(Q,1) ̃CS(Q,N) are for detecting an energy of the light rays converged by the lens LEN1 according to the shutter pulse signal SST. More specifically, when the shutter pulse signal SST represents “open”, the sensing units CS(Q,1) ̃CS(Q,N) detect the energy of the light rays converged by the lens LEN1 (e.g. background light ray LB or reflected light ray LRD) to generate the light sensing signal accordingly; when the shutter pulse signal SST represents “shut”, the sensing units CS(Q,1) ̃CS(Q,N) do not detect the energy of the light rays converged by the lens LEN1. For example, when the shutter pulse signal SST represents “open”, the sensing unit CS(Q,1) senses the energy of the light rays converged by the lens LEN1 to generate a light sensing signal SLS1 accordingly; the sensing unit CS(Q,2) senses the energy of the light rays converged by the lens LEN1 to generate a light sensing signal SLS2; similarly, the sensing unit CS(Q,N) senses the energy of the light rays converged by the lens LEN1 to generate light sensing signal SLSN. Moreover, when the read signal SRE represents “read”, the sensing units CS(Q,1) ̃CS(Q,N) output the light sensing signals SLS1 ̃SLSN, respectively, forming the image signal for the Q-th column of the two-dimensional image F.
The distance calculation circuit 140 includes a plurality of storage units, used for storing the light sensing signals SLS1 ̃SLSN outputted by the sensing units CS(Q,1) ̃CS(Q,N), respectively, and for setting properties of the received light sensing signals according to the phase signal SP. In this embodiment, the distance calculation circuit 140 includes N storage units M1 ̃MN as an example. When the phase signal Sp represents “sum”, the storage units M1 ̃MN set the received light sensing signals SLS1 ̃SLSN as positive, i.e. the receive light sensing signals SLS1 ̃SLSN represent “sum” according to the phase signal SP, and are marked as positive light sensing signals SLS1+ ̃SLSN+; when the phase signal SP represents “noise”, the storage units M1 ̃MN set the received light sensing signals SLS1 ̃SLSN as negative, i.e. the receive light sensing signals SLS1 ̃SLSN represent “noise” according to the phase signal SP and are marked as negative light sensing signals SLS1− ̃SLSN−. The distance calculation circuit 140 can calculate the image distance RO1 according to the positive light sensing signals SLS1+ ̃SLSN+ and the negative light sensing signals SLS1− ̃SLSN−. The following describes operations of the distance calculation circuit 140 calculating the image distance RO1.
As shown on the left of FIG. 17, during the distance sensing stage, the lighting/sensing control circuit 110 generates the light pulse signal SLD representing “lit”, and the light source 102 emits the detection light ray LID to the touch point O1, such that the touch point O1 generates the reflected light ray LRD. Then, the lighting/sensing control circuit 110 generates the shutter pulse signal SST representing “open”, such that the sensing units CS(Q,1) ̃CS(Q,N) sense the energy of the reflected light ray LRD and of the background light ray LB, and generate the light sensing signals SLS1 ̃SLSN, respectively. Then, the lighting/sensing control circuit 110 outputs the read signal SRE representing “read”, such that the image sensor 101 outputs the light sensing signals SLS1 ̃SLSN to the distance calculation circuit 140, and the lighting/sensing control circuit 110 generates the phase signal SP representing “sum” to indicate to the distance calculation circuit 140 that the received light sensing signals are in the distance sensing stage, i.e. the positive light sensing signals SLS1+ ̃SLSN+. Set during the distance sensing stage, the reflected light ray LRD mainly converges to form image on the sensing unit CS(Q,K), and values of the positive light sensing signals SLS1+ ̃SLSN+ received by the distance calculation circuit 140 are as shown in the top-right of FIG. 17, the sensing unit CS(Q,K) simultaneously senses the background light ray LB and the reflected light ray LRD (i.e. the touch point O1 forms image on the sensing unit CS(Q,K)). Therefore, the sensing signal SLSK+ equals the accumulated energy BK of the sensing unit CS(Q,K) sensing the background light ray LB plus the accumulated energy RK of the sensing unit CS(Q,K) sensing the reflected light ray LRD, whereas other sensing units only receive the background light ray LB. Therefore, the sensing signal SLS1+ is equal to an accumulated energy B1 of the sensing unit CS(Q,1) sensing the background light ray LB; the sensing signal SLS2+ is equal to an accumulated energy B2 of the sensing unit CS(Q,2) sensing the background light ray LB; similarly, the sensing signal SLSN+ is equal to an accumulated energy BN of the sensing unit CS(Q,N) sensing the background light ray LB.
As shown on the left of FIG. 17, during the noise sensing stage, the lighting/sensing control circuit 110 generates the shutter pulse signal SST representing “open”, such that the sensing units CS(Q,1) ̃CS(Q,N) sense the light rays converged by the lens LEN1, to generate the light sensing signals SLS1 ̃SLSN. However, the lighting/sensing control circuit 110 would then generate the light pulse signal SLD representing “unlit”, and therefore the light source 102 does not emit the detection light ray LID to the touch point O1, nor does the touch point O1 generate the reflected light ray LRD. Then the lighting/sensing control circuit 110 would output the read signal SRE representing “read”, such that the image sensor 101 outputs the light sensing signals SLS1 ̃SLSN to the distance calculation circuit 140, and the lighting/sensing control circuit 110 generates the phase signal SP representing “noise” to indicate to the distance calculation circuit 140 that the received light sensing signals are in the noise sensing stage, i.e. the negative light sensing signals SLS1− ̃SLSN−. Values of the light sensing signals SLS1− ̃SLSN− received by the distance calculation circuit 140 are as shown in the bottom-right of FIG. 17. The shutter pulse signal SST has a same pulse width (duration TC) during both the distance sensing stage and the noise sensing stage. Therefore, accumulated energy corresponding to the background light ray LB of the light sensing signals SLS1 ̃SLSN generated by the sensing units CS(Q,1) ̃CS(Q,N) during the distance sensing stage and the noise sensing stage would be the same. In other words, the accumulated energy of the background light (B1 ̃BN) would be the same within the positive light sensing signals SLS1+ ̃SLSN+ as within the negative light sensing signals SLS1− ̃SLSN−.
After the distance sensing stage and the noise sensing stage, the lighting/sensing control circuit 110 generates the phase signal Sp representing “distance calculation”. The distance calculation circuit 140 would subtract the negative light sensing signals from the positive light sensing signals in the storage units, and select the storage units with maximum stored values after subtraction, to determine the position of the image formed by the reflected light ray LRD on the image sensor 101 accordingly. In other words, values stored in the storage units M1 ̃MN of the distance calculation circuit 140 equal the values of the positive light sensing signals SLS1+ ̃SLSN+ subtracted by the values of the negative light sensing signals SLS1− ̃SLSN−, respectively. More specifically, the storage unit M1 stores the positive light sensing signal SLS1− and the negative light sensing signals SLS1−, and since both the positive light sensing signal SLS1+ and the negative light sensing signal SLS1− equals B1, the value stored in the storage unit M1 after subtraction would be zero; the storage unit M2 stores the positive light sensing signal SLS2+ and the negative light sensing signals SLS2−, and since both the positive light sensing signal SLS2+ and the negative light sensing signal SLS2− equals B2, the value stored in the storage unit M2 after subtraction would be zero, and so forth. Similarly, the storage unit MK stores the positive light sensing signal SLSK+ and the negative light sensing signal SLSK−, and since the positive light sensing signal SLS2+ equals (BK+RK) and the negative light sensing signals SLS2− equals BK, the value stored in the storage unit MK after subtraction would be RK; the storage unit MN stores the positive light sensing signal SLSN+ and the negative light sensing signals SLSN−, and since both the positive light sensing signal SLSN+ and the negative light sensing signal SLSN− equals BN, the value stored in the storage unit MN after subtraction would be zero. In other words, within the storage units M1-MN, the value of storage unit MK equals RK, while values of all the other storage units equal zero; therefore, the distance calculation circuit 140 may select the storage unit MK accordingly, i.e. the light sensing signal stored by the storage unit MK has an energy corresponding to the reflected light ray LRD. Since the storage unit MK stores the light sensing signal generated by the sensing unit CS(Q,K), the distance calculation circuit 140 may determine that the reflected light ray LRD generated by the touch point O1 mainly converges to form an image at the sensing unit CS(Q,K). As such, the distance calculation circuit 140 may accordingly further derive an image position DCS of the reflected light ray LRD in FIG. 16, from the following equation:

DCS=K×HPIX  (1);

Moreover, in FIG. 16, the line LF formed between a focal point OF of the lens LEN1 and the sensing unit CS(Q,1) is parallel to the detection light ray LID; therefore, an angle θ1 formed by the detection light ray LID and the reflected light ray LRD equals an angle θ2 formed by the LF and the reflected light ray LRD. In other words, a relationship between tan θ1 and tan θ2 may be expressed as follows:

tan θ1=L/DM=tan θ2=DCS/DF  (2);

wherein L represents a predefined distance between the light source 102 and the image sensor 101 (the detection light ray LID and the line LF), DCS represents the image position of the reflected light ray LRD, DF represents a focal distance of the lens LEN1. According to Eqn. (2), the image distance RO1 may be expressed as the following:

RO1=(DF×L)/DCS  (3);

Therefore, the distance calculation circuit 140 may first calculate the image position DCS via Eqn. (1), then calculate the image distance RO1 via Eqn. (3) according to the predefined distance L and the focal distance DF.
Simply put, in the distance measurement device 105, the lighting/sensing control circuit 110 controls the light source 102 to emit the detection light ray LID to the touch point O1 during the distance sensing stage, and the sensing units CS(Q,1) ̃CS(Q,N) sense the light rays converged by the lens LEN1 (e.g. the reflected light ray LRD and the background light ray LB), to generate the positive light sensing signals SLS1+ ̃SLSN+ accordingly, which are stored in the storage units M1 ̃MN. During the noise sensing stage, the lighting/sensing control circuit 110 controls the light source 102 to not emit the detection light ray LID, and the sensing units CS(2,1) ̃CS(Q,N) sense the light rays converged by the lens LEN1 (e.g. the reflected light ray LRD and the background light ray LB), to generate the negative light sensing signals SLS1 ̃SLSN− accordingly, which are stored in the storage units M1 ̃MN. At this point, values stored in the storage units M1 ̃MN would equal the positive light sensing signals SLS1+ ̃SLSN+ subtracted by the negative light sensing signals SLS1− ̃SLSN−. Therefore, the value of the storage unit MK corresponding to the sensing unit CS(Q,K) at which the reflected light ray LRD converges would be higher than that of the other storage units. As such, the distance calculation circuit 140 may determine the sensing unit CS(Q,K) at which the reflected light ray LRD converges, and calculate the image position DCS of the reflected light ray LRD accordingly. Therefore, the distance calculation circuit 140 may calculate the image distance RO1 according to the image position DCS, the focal distance DF of the lens LEN1, and the predefined distance L.
In summary, the optical touch display system of the present invention is capable of determining true coordinates for each of multiple touch points via verification by the distance measurement device. Therefore, the optical touch display system of the present invention may be utilized in multi-touch applications and can accurately determine the position of each touch point, providing the user with more convenient operation.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.

## Claims

1. An optical touch display system, comprising:
a touch region;
a light source, on a periphery of the touch region, the light source positioned at least partially above the touch region, such that light rays emitted from the light source may traverse the touch region;
an image sensor, disposed above the light source, for receiving light rays of the light source, reflected from a touch point on the touch region, and generating a two-dimensional image accordingly, wherein the image sensor is a light sensing array containing M columns and N rows of sensing units for generating the two-dimensional image having a resolution of M×N, where M and N are both integers greater than or equal to two;
a first lens, the first lens for converging a background light or light rays reflected from the first touch point, wherein the image sensor senses an energy of the light converged by the first lens to generate M light sensing signals;
wherein the two-dimensional image comprises a set of optical images corresponding to the touch point, a first optical image of the set of optical images corresponds to a first touch point of the touch point, and a first image distance of the set of image distances and a first image angle of the set of image angles correspond to the first optical image;
a distance measurement device, connected to the light source and the image sensor, for controlling the light source and the image sensor, and generating a set of image distances corresponding to the set of optical images according to coordinates of the set of optical images in the two-dimensional image along a first direction along a Y-axis of the set of optical images in the two-dimensional image, the distance measurement device comprising:
a lighting/sensing control circuit, connected to the light source, for controlling the light source to emit light during a distance sensing stage, while controlling the image sensor to sense the energy of the light converged by the first lens to generate M first light sensing signals, and controlling the light source to not emit light during a noise sensing stage, while controlling the image sensor to sense the energy of the light converged by the first lens to generate M second light sensing signals; and
a distance calculation circuit, connected to the image sensor, for determining an image position of the light rays reflected from the first touch point along the first direction of the image sensor according to the M first light sensing signals and the M second light sensing signals, and calculating the first image distance according to the image position, a focal distance of the first lens, a predefined distance between the light source and the image sensor;

an angle measurement device, connected to the image sensor, for generating a set of image angles corresponding to the set of optical images according to coordinates of the set of optical images in the two-dimensional image along a second direction; and
a processor, for generating a set of output coordinates according to the set of image distances and the set of image angles.

2. The optical touch display system of claim 1, wherein the distance calculation circuit calculates the first image distance according to the following equation:


RO1=(DF×L)/DCS;

wherein RO1 represents the first image distance, DF represents the focal distance of the first lens, L represents the predefined distance between the light source and the image sensor, DCS represents the image position.

3. The optical touch display system of claim 1, wherein the image sensor is disposed at a corner of the touch region.

4. An optical touch display system, comprising:
a touch region;
a light source, on a periphery of the touch region, the light source positioned at least partially above the touch region, such that light rays emitted from the light source may traverse the touch region;
an image sensor, disposed above the light source, for receiving light rays of the light source, reflected from a touch point on the touch region, and generating a two-dimensional image accordingly;
wherein the two-dimensional image comprises a set of optical images corresponding to the touch point, and a first optical image of the set of optical images corresponds to a first touch point of the touch point;
a first lens, the first lens for converging a background light or light rays reflected from the first touch point, the image sensor for sensing an energy of the light converged by the first lens, to generate M light sensing signals;
a distance measurement device, connected to the light source and the image sensor, for controlling the light source and the image sensor, and generating a set of image distances corresponding to the set of optical images according to coordinates of the set of optical images in the two-dimensional image along a first direction, wherein a first image distance of the set of image distances corresponds to the first optical image, the distance measurement device comprising:
a lighting/sensing control circuit, connected to the light source, for controlling the light source to emit light during a distance sensing stage, while controlling the image sensor to sense the energy of the light converged by the first lens to generate M first light sensing signals, and controlling the light source to not emit light during a noise sensing stage, while controlling the image sensor to sense the energy of the light converged by the first lens to generate M second light sensing signals;
wherein M is an integer; and
a distance calculation circuit, connected to the image sensor, for determining an image position of the light rays reflected from the first touch point along the first direction of the image sensor according to the M first light sensing signals and the M second light sensing signals, and calculating the first image distance according to the image position, a focal distance of the first lens, a predefined distance between the light source and the image sensor;

an angle measurement device, connected to the image sensor, for generating a set of image angles corresponding to the set of optical images according to coordinates of the set of optical images in the two-dimensional image along a second direction, wherein a first image angle of the set of image angles corresponds to the first optical image; and
a processor, for generating a set of output coordinates according to the set of image distances and the set of image angles.

5. The optical touch display system of claim 3, wherein the image sensor is disposed at a corner of the touch region.

6. An optical touch display system, comprising:
a touch region;
a light source on a periphery of the touch region, the light source positioned at least partially above the touch region, such that light rays emitted from the light source may traverse the touch region;
an image sensor receiving light rays reflected from a touch point on the touch region and capturing a two-dimensional image having an X-axis and a Y-axis, wherein the image sensor generates M light sensing signals;
a lens converging a background light or light rays reflected from the touch point onto the image sensor; and
a processing device identifying an object image of an object in the two-dimensional image, and calculating a coordinate of the object corresponding to the touch region, wherein the coordinates of the object are measured in the Cartesian coordinate system, wherein an X position of the object image along the X-axis is used to determine an angle of the object with respect to the image sensor and a Y position of the object image along the Y-axis is used to determine a distance of the object from the image sensor, the processing device comprising:
a distance measurement device, connected to the image sensor, generating the distance according to the coordinate of the object in the two-dimensional image along the Y-axis, wherein the distance measurement device comprises:
a lighting/sensing control circuit, connected to the light source, for controlling the light source to emit light during a distance sensing stage, while controlling the image sensor to sense energy of the light converged by the lens to generate M first light sensing signals, and controlling the light source to not emit light during a noise sensing stage, while controlling the image sensor to sense the energy of the light converged by the lens to generate M second light sensing signals, wherein M is an integer; and
a distance calculation circuit, connected to the image sensor, for determining an image position of the light rays reflected from a first touch point along the Y-axis of the image sensor according to the M first light sensing signals and the M second light sensing signals, and calculating the distance according to the image position, a focal distance of the lens, and a predefined distance between the light source and the image sensor;

an angle measurement device, connected to the image sensor, generating the angle of the object according to the coordinate of the object in the two-dimensional image along the X-axis; and
a processor, connected to the distance measurement device and the angle measurement device, and generating an output coordinate according to the distance and the angle of the object.

7. The optical touch display system of claim 6, wherein the distance calculation circuit calculates the distance according to the following equation:


RO1=(DF×L)/DCS;

wherein RO1 represents the distance, DF represents the focal distance of the lens, L represents the predefined distance between the light source and the image sensor, DCS represents the image position.

8. The optical touch display system of claim 6, wherein the image sensor is disposed at a corner of the touch region.