Optical touch panel system and positioning method thereof

The present invention discloses an optical touch panel system and a positioning method for positioning an object existing in a touch control area. The system includes: at least one reflective element disposed on a side of the touch control area; at least one light guide module disposed on a side of the touch control area adjacent to or opposite the reflective element and emitting light; an image sensor capturing an image of the object; a plurality of photo detectors arranged on a side of the touch control area adjacent to the image sensor and sensing the object to obtain shade information; and a processor calculating the coordinates of the object according to the image and the shade information.

CROSS REFERENCE

The present invention claims priority to TW 100138762, filed on Oct. 26, 2011.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to an optical touch panel system and a positioning method thereof, in particular to such optical touch panel system and positioning method which utilize plural photo detectors to resolve the problem of blind zones.

2. Description of Related Art

Touch screen apparatuses are a kind of interactive apparatuses for users to directly and intuitively operate application software on screen. There are various types of touch screen apparatuses, and one of which is the optical touch panel.

FIG. 1shows a prior art optical touch panel system1which is disclosed by U.S. Pat. No. 4,782,328. As shown inFIG. 1, the optical touch panel system1comprises two sensors11for capturing the images of an object13on a touch control area12. A processor14is coupled to the two sensors11, and calculates the sensing paths15linking the object13with the two sensors11by analyzing the images outputted by the sensors11. The processor14also calculates the coordinates of the position of the object13according to the sensing paths15. When the object13is in the region16of the touch control area12close to the side where the two image sensors11are, because the object13is located near the outer of the view angle of the two image sensors11, the images of the object13formed in the two image sensors11are deteriorated or illegible. The region16is called a blind zone.

FIG. 2shows another prior art optical touch panel system2disclosed by Taiwanese Patent Publication No. 201003477, counterpart U.S. Pat. No. 7,689,381 B2. The optical touch panel system2comprises a mirror21, two light sources22, an image sensor23and a processor24. The mirror21and the two light sources22are located around a touch control area28. The mirror21is used to reflect the object25to generate a mirror image26of the object25. The image sensor23captures the image of the object25and the mirror image26. The processor24analyzes the sensing paths27passing the image of the object25and the mirror image26, and calculates the coordinates of the object25according to the two sensing paths27.

In the optical touch panel system2, when the two sensing paths27are too close to each other, the images of the object25and the mirror image26overlap with each other, and the position of the object25cannot be obtained. As shown inFIG. 2, when the object25is in the region of the touch control area28near the side where no light source is provided, the precise position of the object25cannot be detected because the images of the object25and the mirror image will overlap. This region is called the blind zone.

To resolve the problem of the blind zone, Taiwanese Invention Patent Application No. 098131423 (FIG. 10 of U.S. Patent Publication No. 2010/0309169 also discloses a similar apparatus) provides an optical touch control apparatus, as shown inFIG. 3. The optical touch control apparatus100acomprises a lighting device120, an image detection module130, two light guide bars (112a,112b), and two stripe-like mirrors (114a,114b). The light guide bars (112a,112b) are close to each other, and the stripe-like mirrors (114a,114b) are close to each other. The light guide bars (112a,112b) and the stripe-like mirrors (114a,114b) are disposed around the four sides of a rectangle. The inside area of the rectangle is a sensing area116. The light guide module110aincludes two stripe-like mirrors (114a,114b), so each point being touched in the sensing area116generates three mirror images. The image detection module130captures the real image of the object B and the mirror images B1-B3, and calculates the position of the object B according to these images. The area of the blind zone150ain the optical touch control apparatus100ais reduced, but the problem of the blind zone still exists. That is, the dark images of B and B1partially overlap with each other and the dark images of B2and B3partially overlap with each other.

In view of above, the present invention overcomes the foregoing drawbacks by providing an optical touch panel system and a positioning method which utilize plural photo detectors to resolve the problem of blind zones, whereby the positioning of an object is more accurate.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide an optical touch panel system for resolving the problem of blind zones.

Another objective of the present invention is to provide a positioning method of an optical touch panel system.

To achieve the foregoing objectives, in one aspect, the present invention provides an optical touch panel system for positioning an object existing in a touch control area, comprising: at least one reflective element disposed on a first side of the touch control area; at least one light guide module disposed on a second side of the touch control area adjacent to the reflective element or on a third side of the touch control area opposite the reflective element, the light guide module emitting light; an image sensor for capturing an image of the object; a plurality of first photo-detectors arranged on a fourth side of the touch control area adjacent to the image sensor, the first photo-detectors sensing the object to obtain first shade information; and a processor for calculating the coordinates of the object according to the image of the object and the first shade information.

In one embodiment, the image sensor is disposed on one end of the third side of the touch control area opposite the first side on which the reflective element is.

In one embodiment, the optical touch panel system further comprises a plurality of light emitting units disposed on a segment of the second side of the touch control area opposite the first photo detectors.

In one embodiment, the light guide module includes a light guide bar and at least one light emitting device disposed at an end of the light guide bar.

In one embodiment, the optical touch panel system comprises two light guide modules respectively disposed on the second and third sides of the touch control area adjacent to and opposite the reflective element.

In one embodiment, the optical touch panel system further comprises a plurality of second photo detectors disposed on the first side of the touch control area on which the reflective element is, wherein the second photo detectors are adjacent to the first photo detectors, and the second photo detectors sense the object to obtain second shade information for the processor to calculate the coordinates of the object.

In one embodiment, the optical touch panel system further comprises a plurality of second photo detectors disposed on the third side of the touch control area opposite the reflective element, wherein the second photo detectors are adjacent to the image sensor, and the second photo detectors sense the object to obtain second shade information for the processor to calculate the coordinates of the object.

In one embodiment, the first photo-detectors are photo diodes or photo transistors.

In one embodiment, the reflective element is a retro-reflector.

In one embodiment, the image sensor and the first photo-detectors alternatively receive light during different periods.

In yet another aspect, the present invention provides an optical touch panel system for positioning an object existing in a touch control area, comprising: two image sensors disposed on two ends of a side of the touch control area, the image sensors capturing images of the object; a plurality of photo detectors arranged on a middle segment of the side of the optical touch area on which the two image sensors are, the photo detectors sensing the object to obtain shade information; and a processor calculating the coordinates of the object according to the images and the shade information.

In one embodiment, the optical touch panel system further comprises at least one reflective element disposed on a side of the touch control area different from the side on which the two image sensors are.

In one embodiment, the optical touch panel system further comprises a light guide module disposed on a side of the touch control area different from the side of the touch control area on which the two image sensors are.

In another aspect, the present invention provides a positioning method of an optical touch panel system, comprising: capturing at least one image of an object existing in a touch control area by at least one image sensor; sensing the object to obtain first shade information by a plurality of first photo detectors; and calculating the coordinates of the object according to the at least one image and the first shade information.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 4shows a schematic diagram illustrating an embodiment of an optical touch panel system of the present invention. When an object45(e.g. a finger or a stylus pen) is on or above the touch control areas48of an optical touch panel system4, the system can calculate the coordinates of the object45to position it. The optical touch panel system4comprises a reflective element411, a first light guide module421, a second light module422, an image sensor43, a plurality of photo detectors49, and a processor44. The reflective element411is disposed on a first side481of the touch control area48. The first and second light guide modules (421,422) are respectively disposed on a second side482and a third side483of the touch control area48adjacent to each other. The first light guide module421may be, but not limited to, an assembly of alight guide bar423and at least one light emitting device424, and similarly, the second light guide module422may be an assembly of a light guide bar425and at least one light emitting device426. In this embodiment, two light emitting devices424are disposed at two opposite ends of the light guide bar423, while only one light emitting device426is disposed at one end of the light guide bar425. The light guide bar423directs the light emitted from the light emitting devices424towards the surface of the touch control area48and the light guide bar425directs the light emitted from the light emitting device426towards the surface of the touch control area48. The light emitting devices424and426may each be, but not limited to, a linear light source capable of emitting invisible light. In a preferred embodiment, the image sensor43includes an image-sensing window and a filter.

As shown in this figure, the photo detectors49on the fourth side484can receive the light from the first light guide module421on the opposite side482. However, when the object45is in the blind zone of the touch control area48, a portion of the light is shaded by the object45, so at least one photo detector49cannot receive sufficient light, although the other photo detectors49may receive light. Thus, the position of the object can be clearly defined by the shade information from the photo detectors49. The photo detectors may be photo diodes, photo transistors, or other opto-electronic semiconductor devices capable of acting as a light-controllable switch.

The first light guide module421and the second light guide module422can be replaced by any other type of light emitting devices, provided that they can generate light to illuminate the object45in the touch control area48, and the image sensor43and the photo detectors49can receive the light. To obtain the shade information with a better quality by the photo detectors49, preferably but not necessary, the first light guide module421and the second light guide module422can be turned on in a two-step manner. That is, in the first period, the first light guide module421and the second light guide module422simultaneously emit light, and the image sensor43captures the image in this period. In the second period, only the first light guide module421emits light and the second light guide module422is turned off, and the photo detectors49sense the object45in this period so that the photo detectors49only receive light from their front side but not their lateral side. However, the two-step or multiple-step illumination is not necessary if the photo detectors49can sense the shade information with enough good quality when the first light guide module421and the second light guide module422both emit light. In the second period when the photo detectors49are active, to reduce excessive light for better quality lest the excessive light interfere the sensing of the photo detectors49, it can be arranged so that only the light source facing the photo detectors49is turned on. For example, in one embodiment, only the upper one of the light emitting devices424of the first light guide module421is turned on. Thus, the interference from unnecessary light sources can be avoided, and electrical power is also saved.

The processor44analyzes the shade information obtained by the photo detectors49and the image obtained by the image sensor43, to obtain the coordinates of the position of the object45.

FIG. 5shows a schematic diagram illustrating another embodiment of an optical touch panel system of the present invention. Plural light emitting units427such as LEDs (light emitting diodes) are disposed on the second side482of the optical touch panel system4′. Each of the light emitting units427on the second side482and a corresponding one of the photo detectors49on the fourth side484act as a pair of light emitter and light receiver, so that the shade information is further improved. The first light guide module421′ is adjacent to the light emitting units427. The first light guide module421′ can include one light emitting device424at one end of the light guide bar423′ or two light emitting devices424disposed at two opposite ends of the light guide bar423′.

FIG. 6shows a schematic diagram illustrating another embodiment of an optical touch panel system of the present invention. Different fromFIG. 4, the optical touch panel system6of this embodiment comprises two image sensors43. Because a blind zone is located on the middle region close to the side (third side483) on which the two image sensors43are, the photo detectors49are preferably disposed on the middle segment of the third side483. Two first light guide modules421are respectively disposed on the second side482and the fourth side484opposite each other, and the first reflective element411is disposed on the first side481. The above arrangement is just an example; the light guide modules and the reflective element may be respectively disposed on the first side481, the second side482, and the fourth side484in any arrangement. The processor44can calculate the coordinates of the position of the object45according to the images (including real images of the object45and virtual images from the reflective element) captured by the two image sensors43and the shade information obtained by the photo detectors49.

FIG. 7shows a schematic diagram illustrating another embodiment of an optical touch panel system of the present invention. Different fromFIG. 4, the optical touch panel system7of this embodiment further comprises a plurality of photo detectors49′ disposed on the first side481. The first reflective element411′ is adjacent to the photo detectors49′. Furthermore, to obtain the shade information with a better quality by the photo detectors49and49′, preferably but not necessary, the first light guide module421and the second light guide module422can be turned on in a three-step manner. That is, in the first period, the first light guide module421and the second light guide module422simultaneously emit light, and the image sensor43captures the image in this period. In the second period, the first light guide module421emits light and the second light guide module422is turned off, and the photo detectors49sense the object45in this period, so that the photo detectors49only receive the light from their front side but not their lateral side. In the third period, the second light guide module422emits light and the first light guide module421is turned off, and the photo detectors49′ sense the object45, so that the photo detectors49′ only receive the light from their front side but not their lateral side.

FIG. 8shows a schematic diagram illustrating another embodiment of an optical touch panel system of the present invention. In this embodiment, the photo detectors49′ are disposed on the third side483. The light guide bar425′ of the second light guide module422′ is adjacent to the photo detectors49′. Similar to the previous embodiment, preferably but not necessary, the first light guide module421and the second light guide module422′ can illuminate the touch control area in a three-step manner.

The present invention has been described in considerable detail with reference to certain preferred embodiments thereof. It should be understood that the description is for illustrative purpose, not for limiting the scope of the present invention. Those skilled in this art can readily conceive variations and modifications within the spirit of the present invention. For example, the positions and the number of the photo detectors can be different from the foregoing embodiments. For another example, the reflective element may be a retro-reflector, and three reflective elements can be respectively disposed on the three sides (481,482,484) opposite and adjacent the two image sensors43in the embodiment ofFIG. 6. Thus, the present invention should cover all such and other modifications and variations, which should be interpreted to fall within the scope of the following claims and their equivalents.