WO2008011640A1

WO2008011640A1 - A device for determining an object position inside a predefined region

Info

Publication number: WO2008011640A1
Application number: PCT/VN2007/000002
Authority: WO
Inventors: Dinh Le
Original assignee: Dinh Le
Priority date: 2006-07-20
Filing date: 2007-07-19
Publication date: 2008-01-24

Abstract

The invention discloses a device for determining the existence and position of an object appearing inside a predefined region. The device comprises of: a set of photo emitters (1), a set of photo detectors (2) that is placed opposite the set of photo emitters so that the photo emitter and detector of each photo emitter/detector pair face and oppose each other, wherein photo emitters (1 ) and detectors (2) are placed around the predefined region so that the light beams from photo emitters (1) to photo detectors (2) form a coordinate grid; a processing unit (40) for processing the output signals of photo detectors (2) and thereby determining the coordinates of the object when the object appears in the predefined region.

Description

A DEVICE FOR DETERMINING AN OBJECT POSITION

INSIDE A PREDEFINED REGION

FIELD OF THE INVENTION

The invention relates to a device for determining an object's position inside a predefined region, in particular to an optically driven surface sensing device that, when touched on a coordinate point (corresponding to a key on a keyboard) or being glided over on its predefined region (corresponding to the movement of a fingertip on a touchpad), can determine the coordinate(s) of the point being touched or set of points being glided over, and display the coordinate on the display or, based on the coordinate, determine which key of the keyboard is active.

BACKGROUND OF THE INVENTION

Numerous devices for sensing the position of objects on surfaces, including the stylus over tablet (U.S. Pat. No. 5,1:13,041), resistive touch-screen (U.S. Pat. No. 4,806,709), capacitive touch-screen (U.S. Pat. No. 5,463,388), and virtual laser keyboard (U.S. Pat. No. 6,266,048) are well-known.

In the "stylus over tablet" device, the position of the stylus can be determined by means of the signals transmitted to the stylus from a grid of signal lines embedded in the tablet. The processed signal is then sent to the host computer via direct or wireless connection.

In the "resistive/capacitive touch-screen" device, the position of the finger touching the screen, comprising of resistive/insulating layers with point electrodes spaced evenly on the screen, is computed from the relative values of the currents/capacitance received from the point electrodes.

In the "virtual laser keyboard" device, image sensors are used to capture the hand motion over a projected virtual keyboard and the system applies some optical recognition algorithm to the captured image to determine which key(s) has been entered and sends the result to the host system. These surface sensing devices can be used to enter textual and graphical information and to move a cursor around a display. The touch-screen devices have a semi- transparent body that layers over a display.

SUMMARY OF THE INVENTION

The invention discloses an optically driven surface sensing device that, when being touched on a coordinate point (corresponding to a key on a keyboard) or being glided over on its predefined region, can precisely determine the position of the point being touched or set of points being glided over. The device comprises of: a set of photo emitters; a set of photo detectors that is placed opposite the set of photo emitters so that the photo emitter and detector of each photo emitter/detector pair face and oppose each other wherein the said photo emitters and detectors are placed around the predefined region so that the light beams from photo emitters to photo detectors form a coordinate grid; a processing unit for processing the output signals of photo detectors and thereby determining the coordinates of the object when the object appears in the predefined region. The processing unit also provides active pulses for driving the photo emitter emitting pulses of photo signals.

In accordance with an embodiment of the present invention, the device further comprises a pulser for providing active pulses driving the photo emitters and detectors in a predetermined period.

Preferably, the device sequentially determines the position of an object in a first direction, and then in a second direction which crosses over the first direction.

In accordance with an embodiment of the present invention, at least two photo emitter/detector pairs, which are placed so that their two light beams crossover each other, operate simultaneously for determining a coordinate of an object on a plane.

Preferably, the photo emitter/detector pairs are infrared or laser emitters/detectors.

In accordance with an embodiment of the present invention, the said device further comprises an assigning unit for assigning each coordinate point to a key of a keyboard, which corresponds to at least one crossover point of at least two light beams in two directions from the photo emitters to the corresponding photo detectors, a displaying panel having key symbols of a keyboard thereon and being placed below the coordinate grid, which is formed by the light beams from at least two photo emitters to their corresponding photo detectors, so that the key symbols of keyboard are below the intersections of all crossing light beams emitted from the photo emitters to their corresponding photo detectors in two directions. Preferably, the displaying panel, with printed key symbols of keyboard corresponding to coordinate points, is made of flexible material.

In accordance with an embodiment of the present invention, the device comprises of several keyboard interfaces, which are pre-set so that an operator can change one preset keyboard to another when using.

Preferably, the said predefined region is a rectangle with photo emitters and detectors arranged around its circumference so that a plurality of pairs of photo emitters/detectors are placed on the length side and the wide side of the rectangle.

Preferably, the photo emitters/detectors pairs are placed around a hollow rectangular frame, which defines the predefined region at the center, so that the photo emitters/detectors pairs are inserted into predetermined holes on a hollow rectangular frame. The predetermined holes are arranged so that the photo emitter of each photo emitter/detector pair faces and opposes the corresponding photo detector.

In accordance with an embodiment of the present invention, the said device further comprises a multiplexer, encoder, and resistor, used for eliminating an influence of light from the exterior environment on the photo detectors. Preferably, the multiplexer, encoder, resistor, and processing unit are placed on a flexible circuit, which is wrapped around the hollow rectangular frame in such a manner that the pins of the photo emitters/detectors can be soldered thereon.

In accordance with an embodiment of the present invention, the devices are stacked on top of each other to provide a predetermined 3D region, which is a three-dimensional sensoring module for determining an object in the predetermined 3D region.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates an 8 by 12 arrangement of photo emitter/detector pairs in accordance with an embodiment of the present invention.

Figure 2 illustrates a 4 by 4 device in accordance with an embodiment of the present invention.

Figure 3 is an operating flowchart of the device in accordance with an embodiment of the present invention.

Figure 4 shows the top, side and perspective views, respectively, of a 4 by 4 device in accordance with an embodiment of the present invention.

Figure 5 is a layout of a 4 by 4 flexible circuit in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention discloses a device with a plurality of pairs of photo emitters/detectors which are faced with each other and placed around the circumference of a predefined region to determine the existence and coordinates of an object appearing inside the predefined region. All photo emitter/detector pairs are positioned so that emitted lights are sent directly from the photo emitters to their corresponding photo detectors.

The predefined region can be any 2D or 3D shape. The device, in accordance with the present invention, can determine the position of an object appearing inside the predefined region when the object blocks two emitted lights (along the first and second dimensions, respectively) sent from the two photo emitters to their corresponding photo detector pairs. Each photo emitter/detector pair is unique and the emitted light sent from one photo emitter to its corresponding photo detector pair does not interfere with the emitted lights sent from the photo emitters of other photo emitter/detector pairs. The intersection of at least two emitted lights along two different dimensions of the predefined region is called a coordinate. Thus, based on the coordinate of an object inside the predefined region, the device can precisely determine the position of that object.

Furthermore, by assigning each coordinate point to a key of keyboard, for example, the device can determine an activated key, which corresponds to a key on the keyboard.

Figure 1 illustrates an arrangement of a set of photo emitter/detector pairs. The device, in accordance with an embodiment of the present invention, can determine an object's position on the plane which is inside the predefined region formed by photo emitter/detector pairs. In this embodiment, the device comprises of twenty photo emitters and twenty photo detectors being placed arounα a nonow rectangular irame, wherein eight photo emitter/detector pairs are set on the two sides along the width of the rectangular frame and the other twelve pairs are set on the two sides along the length.

It's important to point out that any number of pairs of photo emitters/detectors can be used.

In accordance with another embodiment of the present invention, the emitter/detector pairs are either IR-LED/IR-transistor or laser-LED/photo-diode.

In accordance with another embodiment of the present invention, the hollow rectangular frame can be of any shape, not necessarily rectangular, as long as emitted lights sent from the photo emitters to their corresponding photo detectors pairs are unique and do not interfere with one another.

In accordance with an embodiment of the present invention, as illustrated in Figure 1, the photo emitters are placed on the top and left sides of the hollow rectangular frame, while, the photo detectors are placed on the bottom and right sides of the hollow rectangular frame so that the photo emitter and detector of each photo emitter/detector pair oppose and face each other. Thus, emitter 1 and detector 2 constitute one emitter/detector pair wherein emitter 1 and detector 2 face and oppose each other. Similarly, other emitter/detector pairs in Figure 1 include emitter/detector pairs from 3/4 to 39/40 (not shown). The dash lines in Figure 1 illustrate the emitted light beams sent from the photo emitters to their corresponding photo detectors pairs. The light beams along the length (first dimension) intersect with the light beams along the width (second dimension) to form a 2D coordinate grid. Each intersection of the light beams along the length and the width denotes a coordinate point and corresponds to a key on a keyboard, for instance. If an object appears on a coordinate point, it will block two emitted lights from an emitter/detector pair along the length and an emitter/detector pair along the width. Based on the coordinate created by the pairs of emitters/detectors, the position of an object in the predefined region can precisely be determined.

In accordance with another embodiment of the present invention, emitter/detector pairs are alternatively positioned. For example, on the top, bottom, left, and right sides of me nollow rectangular frame, the photo emitters ana pnoto aetectors are alternatively interposed, i.e. on the same side of the hollow rectangular frame there is a sequence of one emitter and then one detector and then another emitter etc., while on the opposite side, there is a sequence of one detector and then one emitter and then another detector etc., respectively.

Figure 2 is a layout of a printed circuit board (PCB) of a 4 by 4 surface sensor module in accordance with an embodiment of the present invention. This device comprises: the breadboard 20 with appropriate holes to hold pins of the photo emitters (21, 23, 25, 27, 29, 31, 33, 35) and pins of their corresponding photo detectors (22, 24, 26, 28, 30, 32, 34, 36); the micro-controller 40, resistors Rl and R2 in slots allocated behind. The interconnection between pins on the complete board can be fabricated using traditional etching and soldering techniques.

The micro-controller 40 is the most important element of the module, and sends pulses to emitters (21, 23, 25, 27, 29, 31, 33, 35) via output ports (1, 2, 3, 4, 5, 6, 7, 8) and receives sensoring signals from detectors (22, 24, 26, 28, 30, 32, 34, 36) via input ports (9, 10, 11, 12, 13, 14, 15, 16). Based on the signals received via input ports, the micro-controller 40 can determine the existence and coordinates of an object appearing inside the predefined region formed by emitters (21, 23, 25, 27, 29, 31, 33, 35) and detectors (22, 24, 26, 28, 30, 32, 34, 36).

In accordance with the present invention, the photo emitter/detector pairs are preferably IR-LED/IR-transistor and laser-LED/photo-diode.

The micro-controller 40 sends active pulses to emitters (21, 23, 25, 27, 29, 31, 33, 35) in a predetermined period. In accordance with an embodiment of the present invention, the micro-controller 40 divides one second into 8 periods from tl to t8, and then sends 8 pulses corresponding tl-t8 periods to emitters 21, 23, 25, 27, 29, 31, 33, 35, wherein each period is 0.125 second. In each period, the micro-controller 40 inspects whether or not detectors 22, 24, 26, 28, 30, 32, 34, 36 receive signals from the corresponding emitters 21, 23, 25, 27, 29, 31, 33, 35, respectively. For example, in 1 second, the micro-controller 40 sends a pulse in period tl = 0.125 second to emitter 21, and inspects whether or not the corresponding detector 22 receives the signal from emitter 21. Therefore, in the period of 1 second, if one key is pressed, which corresponds to that an object appears in the predefined region and blocks a iignt beams oi at least one photo emitter/detector pair in the horizontal direction and at least one photo emitter/detector pair in the vertical direction, the micro-controller 40 will be able to determine the coordinates of the object corresponding to the key pressed.

In accordance with an embodiment of the present invention, micro-controller 40 can simultaneously send pulses to two photo emitters, one of which is in the horizontal direction and the other is in the vertical direction.

In accordance with an embodiment of the present invention, the device further comprises a filtering system for blocking out unwanted ambient light that may affect the accuracy of the signals of the device. Therefore, 3 output ports of micro-controller 40 are used for a multiplexer and 3 input ports of micro-controller 40 are used for an encoder. Other output ports of micro-controller 40, such as Clock, Data, GND, and Vcc, are used to enable the device to communicate with other devices, such as a computer.

Although this embodiment is provided with the arrangement of photo emitter/detector pairs including 4 pairs in horizontal and 4 pairs in vertical, the number of photo emitter/detector pairs may increase or decrease by n pairs in horizontal and m pairs in vertical depending on the emulated system's requirements, wherein n and m are integers.

With the arrangement of 4 pairs in horizontal 8 and 4 pairs in vertical, there are 16 coordinates and each coordinate can be associated with a key on a keyboard. The keys on the keyboard are presented on displaying panel placed below the coordinate grid so that each coordinate corresponds to a predefined key on the keyboard. The displaying panel is preferably made by a plastic material, preferably by polyester or polyimide resin.

The micro-controller 40 is configured to recognize each coordinate point corresponding to a key of the keyboard.

In accordance with an embodiment of the present invention, the device further comprises an assigning unit for assigning each coordinate point to a key of a keyboard. The assigning unit may contain many keyboard interfaces and a user can easily change from one to another keyboard interface according to his/her demand. Therefore, data from micro-controller 40 is further processed by the assigning unit for determining which key is currently active.

In accordance with an embodiment of the present invention, the assigning unit is integrated into the micro-controller 40.

Figure 3 is the operational flowchart of the micro-controller 40 in Figure 2, wherein: the emitter 29 is a High value (emitter 29 HIGH), i.e. the micro-controller 40 sends a pulse with a HIGH level (HIGH pulse) to output port 1 of the micro-controller 40 connected with emitter 29 for emitting a signal with a HIGH level (HIGH signal), the emitter 29 is a Low value (emitter 29 LOW), i.e. the micro-controller 40 sends a pulse with LOW level (LOW pulse) to output port 1 of the micro-controller 40 connected with emitter 29 for emitting a signal with a LOW level (LOW signal), therefore, if the detector 30 = 1, i.e. the detector 30 receives a HIGH signal from emitter 29, the micro-controller 40 also receives a HIGH signal from emitter 29, and similarly for other emitter/detector pairs.

It should be noted that, IR photo transistors will emit a HIGH signal in the absence of IR light, and a LOW signal when there is IR light.

The process starts by resetting the variables rowPos (horizontal direction) and colPos (vertical direction) to zero. Then it proceeds to find the row position of the object. If no object is found along the rows, the algorithm goes back to the beginning. If an object is detected, its row position is saved in the variable rowPos before continuing to find the object's column position. If no object is found along the columns, the algorithm goes back to the beginning. If an object is detected, its column position is saved in the variable colPos before continuing to execute another application, depending on the type of the application such as a keyboard protocol, mouse protocol, etc. Afterward, the algorithm starts over again. The programming code for searching the object's row position starts with the command 'HIGH emitter 29' to send a pulse to IR emitter 29. Then the conditional statement 'if detector 30 = V is run to sense whether the signal generated by the IR photo transistor 30 (its paired detector) is high (IR light is blocked) or low (IR light is not blocked). IfIR light from its paired emitter is blocked, the variable rowPos is set to 1, command 'LOW emitter 29' is run, and the algorithm continues on to find the object's column position. IfIR light from its paired emitter is not blocked, command 'LOW emitter 29' is run, command 'HIGH emitter 31' is executed, and is repeated for the rest of the emitter/detector pairs along the row as described in the flowchart shown in Figure 3. The programming code for searching the object's column position is similar to that for searching the row position as described by the flowchart shown in Figure 3.

The energy efficiency and reliability are achieved by the following reasons. Each IR LED takes a turn to emit IR beam and a single IR beam consumes less energy than multiple IR beams. Each IR emitter is pulsed and then turned off, thus consuming a fraction of the energy that a continuously beamed IR emitter would require. Pulsed current can be provided stronger than regular current, and therefore, easier generated to detect the IR beam. A single beam being sent to a single destination does not interfere with its neighbors, while multiple beams sent to multiple destinations do interfere with one another.

In one embodiment of the present invention, an arrangement of emitter/detector pairs is provided with a flexible circuit, as shown in Figure 5, and a hollow rectangular frame having a hollow center, as shown in Figure 4, create a flex-frame optical surface sensor module. Flexible circuitry layout is much like PCB circuitry layout except that a flexible polyimide or polyester base is to be used instead of a rigid breadboard. Information about flexible circuit technology can be obtained from J. Fjelstad's "Flexible Circuit Technology 2nd Edition, Silicon Valley Publishers Group, Sunnyvale, Calif., 1998." The flexible base enables a flexible circuit to be placed on non-flat surface, in particular, in accordance with this embodiment of the present invention, to be wrapped around the hollow rectangular frame. The functions of the hollow rectangular frame are to hold the emitter/detector pairs firmly inside its rigid body, to block ambient light from interfering with IR LEDs and IR photo transistors, to keep emitters and detectors accurately aligned, and to provide a big hollow region between the emitters and detectors.

Figure 4 shows a hollow rectangular frame having 4 lines and 4 columns according to one embodiment of the present invention. The hollow rectangular frame has been made from a dark color non-conductive rigid material (mostly dark plastic). 16 holes on the four walls are arranged so that 8 emitters can be placed snuggly inside the holes 51, 52, 53, 54, 59, 60, 61 and 62, and 8 detectors can be placed snuggly inside the holes 55, 56, 57, 58, 63, 64, 65 and 66 to create 4 emitter/detector pairs along the row and 4 emitter/detector pairs along the column and each emitter of the emitter/detector pairs is faced and opposed to the corresponding detector. Thus, the emitter inside hole 59 and the detector inside hole 63 would form an emitter/detector pair. The hollow region (Figure 4) allows light beams to freely run from emitters to detectors, expands the module capability to fit and integrate in tricky environment, and enables it to be stacked and integrated with other flex-frame optical surface sensor module to become 3D flex-frame optical cubic space sensor module.

In accordance with an embodiment of the present invention, by stacking multiple devices of the invention, it is possible to determine and track the position and size of an object in 3D space by matching the original coordinate points with the coordinate points in which the signals from emitters to detectors are blocked so as to detect which key is pressed.

Figure 5 illustrates a flexible circuit, which wraps around a hollow rectangular frame so that the emitters' and detectors' pins stand at the locations 70 to 85. Specifically, the IR photo transistor in hole 55 of the frame in Figure 4 can be inserted into the two pin holes at location 70 and is soldered therein. Similarly, the IR photo transistor in hole 56 of the frame in Figure 4 can be inserted into the two pin holes at location 71 and soldered therein, and the other elements are treated in the same manner. As shown in Figure 4, preferably, the MUX (multiplexer) in the flexible circuit is located on FACE A of the frame, MC (micro-controller) on FACE B, and ENC (encoder) on FACE C. The circuitry and programming code for both PCB and flex-frame surface sensor modules are similar.

Figure 4 and 5 illustrate an arrangement including 4 rows and 4 columns, and such an arrangement can easily be adapted to any n rows and m column where n and m are integers.

Although the invention is described in details by referring to specific cases and figures, it should be noted that many improvements or modifications can easily be made to the device according to the invention by the ordinarily skilled persons in this field, where such improvements or modifications must be considered as a part of the invention, and the scope of which should be defined by the appended claims.

Claims

Claims:

1. A device for determining the position of an object appearing inside a predefined region comprises: a set of photo emitters; a set of photo detectors that is placed opposite the set of photo emitters so that the photo emitter and detector of each photo emitter/detector pair face oppose each other; wherein the said photo emitters and detectors are placed around the predefined region so that the light beams from photo emitters to photo detectors form a coordinate grid; a processing unit for processing the output signals of photo detectors and thereby determining the coordinate of the object when the object appears in the predefined region.

2. The device according to claim 1, wherein the said processing unit also provides active pulses for driving the photo emitter emitting pulses of photo signal.

3. The device according to claim 1, further comprises a pulser for driving the photo emitter/detector pairs in a predetermined period.

4. The device according to any of the preceding claims, wherein the device sequentially determines the position of an object in a first direction and in a second direction which crosses over the first direction.

5. The device according to any one of claims 1-3, wherein at least two photo emitter/detector pairs which are placed so that their two light beams crossover each other, is operated simultaneously for determining coordinates of an object on the plane.

6. The device according to any of the preceding claims, wherein the photo emitters and photo detectors are infrared emitters and detectors.

7. The device according to any of the preceding claims, wherein the photo emitters and photo detectors are laser emitters and detectors.

8. The device according to any of the preceding claims, wherein the device further comprises an assigning unit for assigning each coordinate point to a key of a keyboard, which corresponds to at least one crossover point of at least two light beams in two directions from the photo emitters to the corresponding photo detectors.

9. The device according to any of the preceding claims, wherein the device further comprises a displaying panel having key symbols of a keyboard thereon and being placed below the coordinate grid, which is formed by the light beams from photo emitters to their corresponding photo detectors, so that the key symbols of the keyboard are below the intersections of all crossing light beams emitted from the photo emitters to their corresponding photo detectors in two directions.

10. The device according to claim 9, wherein the displaying panel is made of flexible material, on which key symbols of a keyboard, corresponding to coordinate points, are printed.

11. The device according to any of the preceding claims, wherein the device comprises several keyboard interfaces, which are pre-set so that in using an operator can change one pre-set keyboard to another.

12. The device according to any of the preceding claims, wherein said predefined region is of rectangular shape.

13. The device according to any of the preceding claims, wherein the photo emitters and detectors are arranged around the circumference of a predefined region so that a plurality of pairs of photo emitters/detectors are placed on the length side and the width side of a rectangle.

14. The device according to claims 12 and 13, wherein the photo emitter/detector pairs are placed around a hollow rectangular frame so that the photo emitter/detector pairs are inserted in predetermined holes on the hollow rectangular frame and the photo emitter of each photo emitter/detector pair faces and opposes the corresponding photo detector.

15. The device according to any of the preceding claims, wherein the device further comprises a multiplexer, encoder, an resistor, used for eliminating an influence of light from exterior environment on the photo detectors.

16. The device according to claim 15, wherein the multiplexer, encoder, resistor, and processing unit are placed in a flexible circuit.

17. The device according to claim 16, wherein the said flexible circuit is wrapped around a hollow rectangular frame in such a manner that the pins of photo emitters/detectors can be soldered thereon.

18. The device according to any of the preceding claims, wherein the several devices are stacked on top of each other to provide a predetermined 3D region for determining the position of an object in the predetermined 3D region.