| 摘要 |
PURPOSE:To output an image plane movement signal and its correcting signal by converting the driven extent of a focusing lens into as image plane movement extent signal in prescribed relation which does not depend upon variation in focal length, and also generating a focal length signal as the correcting signal. CONSTITUTION:The pattern 27 of a gear 26 rotates as a focusing lens moves in its optical-axis direction. The focal length of a zoom lens is inputted to a variable resistance 36 in the form of a focal length ratio. Light from a light emitting diode 40 is reflected by the pattern 27 to illuminate a phototransistor 29, and amplitude modulation is imposed by focal length information through a constant current from a constant current source 41; and a pulse signal consisting of pulses whose number corresponds to the movement extent of an image plane is inputted to a programmable counter 45 through a comparator 42 and delay circuit 44. A pulse detector 46, on the other hand, separates a focal length ratio signal, which is inputted through an AD converter 47 and latch circuit 48 to a counter 45; and a pulse signal from a delay circuit 44 is frequency-divided according to the focal length ratio to output an image plane movement extent signal irrelative to the focal length of the zoom lens. |
