| 摘要 |
Viewed from the subject side, the macrolens system consists of a first positive lens group (10), a second negative lens group (20) and positive third (30) and negative fourth (40) lens groups and in sharp focusing, commencing from infinity focus right through to the close-up limit, the second lens group (20) is moved towards the image and the third group (30) moved towards the subject. This should satisfy the condition (lf . m/ delta X3l to lie between 3.7 and 9.9) wherein (f) denotes the total focal length in the infinity setting with image scale at near focus limit and ( delta X3) is the travel by the third lens group (30) from infinity to near focus setting. In addition to this, the system satisfies the condition (l delta X3/ delta X2l between 0.85 and 1.5) in which ( delta X2) represents the path traveled by the second lens group (20) from infinity to near focus setting. In a third condition (l beta 3E- beta 3sl) should be between 0.1 and 0.34, with ( beta 3E/ beta 3s to be up to 0). The image scale of the third lens group (30) in infinity setting is denoted by ( beta 3E) and ( beta 3s) is the third lens group image scale in the near focus setting.
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