| 摘要 |
PURPOSE:To improve the range-finding accuracy and enable secure automatic focusing operation by range-finding by irradiating the top surface of microfilm pressure glass with a distance measurement beam and then detecting a focusing state. CONSTITUTION:At least >=2 split elements 4 and 4' are arranged so as to find a range between a lens barrel 5 and the top surface of the film pressure glass 18, and made to correspond to film carrier information. Then a trigonometric distance measurement system is employed as a range-finding system and discriminations of the top surface of the film pressure glass 3, a film surface 2, etc., and others are confirmed by comparing the peak value of the quantity of irradiation light and the positions of the split elements 4, thereby finding the range with reflected light on the top surface of the film pressure glass. Consequently, remarkable defocusing due to the replacement of a film carrier and a projection lens 5 is minimized, focus operation is facilitated, and an operation time is shortened. |
