| 摘要 |
PURPOSE:To focus automatically even if the focusing distance is changed in a zoom lens, by focusing by dividing and counting pulses generated by revolving a motor for lens extension in a corresponding proportion to a rotating angle of a zoom ring of a zoom lens. CONSTITUTION:A defocus amount DELTAL outputted from a range finding part 9 and a signal in the direction of lens extension are inptted to a controller 11 and a lens extension amount DELTAd is counted and made to digital to be outptted to an up down counter 12. A signal of driving a motor 2 is outputted to a driving circuit 13 from the controller 11, and a pulse of each unit of lens 7 movement is inputted to a divider 34 from a generator 10, and the data corresponding to a rotating angle of a zoom ring of a lens 7 from a zoom ring encoder 35 is also inputted to the divider 34, and the pulses from the generator 10 is divided at a ratio in accordance with the data. The pulses from the divider 34 are inputted to a counter 12 and the lens extension amount DELTAd which is preset is subtracted, and when the value of the counter 12 becomes zero, focusing is made and the motor 2 is stopped. |
