| 摘要 |
PROBLEM TO BE SOLVED: To provide a zoom lens, which is more suitable to be made small-sized and low-cost in comparison with a conventional zoom lens and is especially suitable for a small-sized portable information terminal. SOLUTION: A first lens group G1, which has a positive refraction power and is fixed at the time of varying the power of the system, a second lens group G2 which has a negative refraction power and is moved from the object side to the image surface side between the wide-angle end and the telephoto end, when varying the power of the system, a third lens group G3 which has a positive refracting power and is moved from the image surface side to the object side between the wide-angle end and the telephoto end when varying the power of the system, and a fourth lens group G4 which has a positive refracting power and can be moved, when varying the power of the system are provided in the order from the object side, and this zoom lens satisfies conditional formula (1) related to the power of the third lens group G3, conditional formula (2) related to the extent of movement of the third lens group G3, when varying the power of the system or conditional formula (3) related to the combined power of the third and fourth lens groups G3 and G4, and a condition (10) related to the actual value of the back focus.
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