| 摘要 |
<p>PURPOSE:To always enable optimal holding of sensitivity of a detector by adjusting the quantity of a detection light to set an optimum sensitivity with the reading of a received light signal. CONSTITUTION:A quantity of light adjusting means is made up of a control voltage setting circuit 11, a current setting circuit 12, an LED driving circuit 13 and a pulse generation circuit 14 to adjust the quantity of a detection light projected from a light emitting element 5. Then, a signal detection circuit 15 reads a signal of a light receiving element 6 according to the quantity of the detection light and a CPU 10 as sensitivity setting means selects a quantity of the detection light so as to maximize a difference in signal between a state with a lower cloth alone and a state with upper and lower cloths, namely, a sensitivity difference and the sensitivity difference thus obtained is set as sensitivity of the detector. Thus, the sensitivity of the detector is so set to maximize the sensitivity difference between the state with the lower cloth alone and the state with the upper and lower cloths thereby always making the detector sensitivity optimal and correct irrelevant to the thickness and color of the lower and upper cloths.</p> |
