| 摘要 |
PURPOSE:To obtain a good focusing capacity throughout the screen from the infinity to the short distance, by feeding the last lens of a front group lens in a speed different from that of other lenses in case of focusing from the infinity to the short distance. CONSTITUTION:A front group lens having a positive refracting power consists of the first lens of a positive meniscus lens whose convex is directed to the object, the second lens of a biconcave lens, and the third lens of a biconvex lens which are arranged in order from the object side, and a rear group lens having a negative refracting power consists of the fourth lens of a negative meniscus lens whose convex is directed to the image surface. In case of focusing from the object of the infinity to the object of the short distance, the front group lens is fed, and further, only the last lens of the front group lens is fed. Thus, the variance of the screen is eliminated to give a uniform focusing capacity onto the same face throughout the screen from the infinity to the short distance. |
