| 摘要 |
PROBLEM TO BE SOLVED: To obtain a telecentric zoom lens having fixed speed on the image side of the lens by mechanically including a telecentricity formed diaphragm positioned in the middle of an objective lens and a zoom group. SOLUTION: The telecentric zoom lens system includes a 1st collimator FC, a 1st decollimator FD, a zoom group ZG, a 2nd collimator SC and a 2nd decollimator SD along an optical axis. The 1st collimator FC turns a light beam from the axial point of an object surface substantially in parallel with the optical axis. The 1st decollimator FD is arranged along the optical axis on the image side of the objective lens and converges the light beam at the image side of the 1st decollimator FD. The telecentric diaphragm TA is arranged along the optical axis of the back of the 1st collimator FC, and arranged at a fixed position along the optical axis. It is desirable that the telecentric diaphragm TA is variable, and its variation range is enough to provide the fixed speed to the image side.
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