| 摘要 |
PURPOSE:To obtain a wide angle lens and to lengthen a back-focus, by providing the first lens consisting of a positive lens, the second lens consisting of a positive lens and the third lens consisting of a negative lens, on the same optical axis, and reducing a space between the second lens and the third lens. CONSTITUTION:The first lens P1 consisting of a positive lens, the second lens P2 consisting of a biconcave positive lens and the third lens P3 consisting of a negative lens are provided in said order on the same optical axis. In case of this invention, a space L2 between the second lens P2 and the third lens P3 is set so as to satisfy 0.6f>L2>0.3f. (Provided that (f) denotes a focal distance of the whole lens system). In this way, a wide angle lens is obtained and a back-focus is lengthened by reducing the space between the second lens P2 and the third lens P3. |
