| 摘要 |
PROBLEM TO BE SOLVED: To provide a position detector and an auto-focus apparatus which can be realized by simple and inexpensive structure and to provide an image recorder which records an image corresponding to an image signal in a recording material by using these position detector or auto-focus apparatus. SOLUTION: Light beams which form an image in the neighborhood of the surface of an object is emitted from a light source, and reflected light scattered on the surface of the object is caught by an optical detection element to obtain the current signal of a current value. This current signal is converted to the voltage signal of a voltage level according to the current value, the maximum value and the minimum value per a unit time of the voltage signal are respectively detected to calculate the voltage of the difference between the maximum value and the minimum value of the voltage signal. Then, the voltage of the difference is compared with a reference value. According to the compared result, it is discriminated whether the object exists within a prescribed range decided by the reference value. COPYRIGHT: (C)2003,JPO |
