Study on Shadow Touching for interactive projector devices
Touch devices have become one of the major elements in today’s most electronic devices. It is commonly used in ATMs, smart phones and tablet PCs. Touch technology can be divided into different types as resistive, capacitive, infrared, and so on. However, with the increase of detection elements, most types of touch screen suffer more cost and lower yield when the accuracy of touch location or larger size is requested. Therefore, it is essential to design a different kind of touch technology with an accurately detection that the cost is not proportional to its size simultaneously. The purpose of this thesis is to provide a kind of touch system that uses the distance between the object and its shadow to detect the touch-timing and position. It can be applied to an interactive projection system without using a lot of touch detecting elements. That is, no additional costs are needed for a great touch screen. This thesis takes advantage of the relative relationship between finger (stylus) and its shadow to determine whether a finger or stylus touches the screen. When a finger or stylus approaches screen, its tip will close to the tip of shadow and even mask it. By tracking the location of the finger with the distance changes between fingertip and its shadow in many frames, the occurrence of touching and its location can be determined. Touch system proposed by this thesis needs only one camera and one IR source, and acts with an interactive projector to detect the occurrence of touching and its location. One of advantages of this touch system is that it needs only one camera. Secondly, it can be moved easily and constructed by any white wall or projection screen. Finally, the touch detection can be done without touching the screen hardly. Comparing to other large-size touch panels which are not easy to move and need two or more cameras to locate touch position, the touch system proposed in this thesis is superior in cost and establishment.
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