| 摘要 |
PURPOSE:To make a distance measurement area constant and to secure forcusing by providing an autofocus device with a projection lens system so that its power is variable. CONSTITUTION:The projection lens barrel 3 of the autofocus device 1 is provided with a variable power ring 4 and a gear 5 is formed at its periphery. The gear 5 engages a gear 22 provided to the photographic lens barrel 20 of an image pickup lens system 25. The power of the projection lens system 6 is therefore varied as the image pickup lens system 25 is displaced. Consequently, when the power of the projection lens system 6 is varied, the distance measurement area which is varied between a telephoto and a wide-angle in a conventional image pickup plane is made constant and misfocusing due to the entry of an unnecessary object into the distance measurement area is evaded, so that secure focusing is performed. |
