| 摘要 |
The zoom lens is of the type having equivalent focal lengths varying from less than the diagonal of its image frame to an equivalent focal length at least twice the diagonal of the image frame and having a short front vertex distance. The zoom range may be as great as 5:1, with a field angle in excess of 70 degrees at the widest field position. The lens comprises a positive group(G1), a second negative group(G2) & a third positive group(G3). At least two of the groups are movable axially to vary the equivalent focal length. The second group has an absolute optical power greater than the first & third groups.
|
