| 摘要 |
<p>PROBLEM TO BE SOLVED: To suppress an influence upon an output signal and to prevent detection missing even when an influence of an external light (noise) is received and a light receiving energy of a light receiving element fluctuates. SOLUTION: This touch panel irradiates a retroreflection body with a laser beam outputted from a light emission part 15, compares a signal equivalent to a light receiving energy of a light receiving element 16 with a threshold, and detects a coordinates' position specified by an object. In this case, the touch panel is provided with a laser driver IC 32 as a laser driver, an LD driving pulse (1) is supplied to a control terminal 37 of the baser driver IC 32 so as to output a laser beam in a pulse shape from a laser diode 30 of the light emission part 15. The touch panel is also provided with a clamp circuit 41 which champs a low level side of a light receiving signal of the light receiving element 16 to a minimum level by the pulse (1) and a sample hold circuit 43 which samples/holds an output of the clamp circuit 41 by the pulse (1) and outputs a signal V1a (V2a) equivalent to the light receiving energy.</p> |
