| 摘要 |
PURPOSE:To discriminate the upper side from the rear side of an optical information recording medium having an equal reflection factor between its both sides by using a means which detects the depth of a light reflecting surface and discriminating the upper and rear sides of the recording medium based on the detected depth of the reflecting surface. CONSTITUTION:When an optical card 1 is set normally, a distance sensor 2 is positioned so that the distance is set at l0 between the sensor 2 and a card substrate 1b serving as a reflecting surface. In this case, the output current of the sensor 2 is equal to I0. When the card 1 is set upside down, the distance l1 between the sensor 2 and the substrate 1b is less than the distance l0. In this case, the output current I1 of the sensor 2 is less than the current I0. Thus it is possible to decide whether the card 1 is set normally or not based on a fact that both currents I0 and I1 are different from each other. As a result, the upper and rear sides are discriminated from each other for an optical recording medium having an equal reflection factor between its both sides. |
