| 摘要 |
PURPOSE:To highly accurately measure the distance to an object from short to long ranges by receiving the reflected light from the object with a photoelectric converting element so that the output signals and the signals delayed a preset time are differentially amplified by a differential amplifier. CONSTITUTION:When a shutter button is depressed with a camera directed to an object, a lens mount is pulled toward infinity by a spring SP1 so that light from a light emitting element ED1 scanns the object from short to long ranges. A photoelectric converting element PD1 receives the light reflected from the object so that the resultant output signals and the signals delayed a preset time by a delay circuit are differentially amplified by a differentially amplifying circuit. The position, where the polarity of the output of the differential amplifier is reversed, is detected through a comparator circuit to deenergize an electromagnet Mg1 so that the stop pawl AM1 of an armature lever engages with a ratchet wheel G2 to stop the movement of the lens mount thereby to position a photographic lens LS5. |
