| 摘要 |
PROBLEM TO BE SOLVED: To provide a retroreflection type touch panel device designed to reduce the effect of disturbance light and eliminate detection troubles without using a douser, and also to facilitate cleaning.SOLUTION: Equipped with a retroreflection member for recursively reflecting the light emitted from a light source 21 and diffused in the form of a fan parallel to a touch board surface, the retroreflection type touch panel device detects a touch position by the presence of reflected light. The retroreflection type touch panel device comprises an oscillator 41 for generating a sinusoidal wave and a drive circuit 42 for supplying a drive current amplitude modulated by the sinusoidal wave to the light source 21. The retroreflection type touch panel device further comprises a photodetector system 50 provided with a DC circuit breaker for eliminating the DC component of the output of a photodetector that receives the reflected light, a synchronous detector for synchronous-detecting the output of the DC circuit breaker using the sinusoidal wave, a low-pass filter for smoothing the output of the synchronous detector, and a comparator for comparing the output of the low-pass filter with a prescribed threshold and determining the presence of reflected light. |
