| 摘要 |
In a system for driving automatically an objective lens into a desired focal position so as to form a focussed image on a film plane, in order to derive a driving signal for a driving motor moving the objective lens along its optical axis, an auxiliary lens is arranged movably along its optical axis, a moving coil and a position detecting coil are wound around a lens holder, magnets cooperating with the coils are arranged around the coils, and an array of photoelectric converting elements is arranged to receive a light flux transmitted through the auxiliary lens. The auxiliary lens is vibrated about a reference position by supplying a sinusoidal signal to the moving coil. An output signal from the array of photoelectric converting elements is supplied to a focus detection circuit to generate sampling pulses at such timings that the photoelectric converting elements receive the best focussed image. An output signal from the coil is supplied to a lens position detecting circuit to produce a lens position signal representing a deviation of the auxiliary lens with respect to the reference position. The lens position signal is sampled and held by the sampling signal to produce the driving signal for the motor.
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