| 摘要 |
PURPOSE:To make an efficient focus adjustment by projecting and photodetecting light through a constituent lens group when the focal length of a photographic lens is larger than a specific reference value, and making the focus adjustment through a projecting and a photodetecting part installed outside when said length is smaller. CONSTITUTION:The center of a light spot 43 in focus is aligned to the center of a two-divided photodetecting element 25. Then when a zoom lens 12 is extended toward a subject beyond an in-focus state, the center of a light spot 44 shifts to right, and when the lens moves toward an image pickup element 17, a light spot 45 shift to left. For the purpose, the values of two signal outputs I1 and i2 are compared and the photographic lens is driven on the basis of the comparison result to make the focus adjustment. The light from the 1st light emitting element 22 is received by the 1st photodetecting element 25 and the light from the 2nd light emitting element 23 is photodetected by the 2nd photodetecting element 26; and their outputs are passed through current-voltage converters 27-29 and voltage amplifiers 30-32, then compared by the 1st and the 2nd comparators 33 and 34, and a focus adjusting mechanism 36 outputs a signal which shows the stop or driving direction of the lens group for adjusting the focus to the zoom lens 12. |
