| 摘要 |
PURPOSE:To attain accurate measurement of distance from a close distance to remote distance by projecting light generated by continuous pulse driving to an object, converting a signal based on the reflected light from an object into a voltage and counting the number of times of inverting outputs after comparing the voltage with a reference voltage. CONSTITUTION:An infrared light emission diode 1 which is optically modulated by being continuously driven in terms of pulse is used as the light source of an automatic focusing (AF) device. When the pulse light which returns by reflected from the object is photoelectrically converted, the photoelectrically converted voltage of signal for automatic focusing is compared with the reference voltage by one comparator 19. Thereafter, the number of times of the inversion in the comparator is counted by a counter 22 so as to control to digitally switch an IRED driving current with the outputs from the counter. Since the switching of light quantity in two stages or above can be possible, the accurate AF can be performed from a close distance to a remote distance by using the optimum signal level. |
