| 摘要 |
<p>PURPOSE: To detect presence or absence of an object of detection within a prescribed distance by receiving a reflected light of a signal light from the object, by detecting an image of the object with a fixed-light component removed and by reading a signal- light component after a prescribed time from emission of the light. CONSTITUTION: When a light-emitting part LA is turned ON, switches SA1 and SA2 ON and SA3 and SA4 OFF, an electric charge corresponding to a fixed light plus a signal light is stored in a capacitance CA. When the light-emitting part LA is turned OFF and the switches SA1 to SA4 are operated reversely, then, a fixed-light component is subtracted from the stored charge of the capacitance CA and a signal-light component is left. This component is added up and stored repeatedly, switches SA3 and SA6 are turned ON at a prescribed period and the charge of the capacitance CA is transferred to a capacitance CI. A function as an image sensor is thereby executed. Subsequently, the switches SA1 and SA2 are turned ON only for a prescribed time after a certain time from emission of light and SA3 and SA4 are turned ON a sufficient time later. Presence or absence of an object within a prescribed distance can be determined on the basis of whether the electric charge is left or not in the capacitance CA at this time.</p> |
