| 摘要 |
PROBLEM TO BE SOLVED: To excellently correct chromatic aberration by the small number of lenses and to make a telephotographic lens compact and light in weight by arranging a diffraction and refraction hybrid surface provided with zonal structure having the action of a blazed positive diffraction lens in a front group and satisfying a specified condition with the Abbe's number and the partial variance ratio thereof. SOLUTION: The telephotographic lens is constituted of the front group 10 consisting of a first positive lens 11 and a second negative lens 12 and a rear group 20 consisting of two of a positive lens 21 and a negative lens 22 in turn from an object side. Then, the diffraction and refraction hybrid surface (surface provided with both of a diffracting action and a refracting action) provided with the circular zonal structure having the action of the blazing (for optimizing the shape of a diffraction surface in order to enhance diffraction efficiency) positive diffraction lens is arranged in the group 10. Besides, when the Abbe's numberνd of the lens 11 is defined asν1, the partial variance ratioθgF is defined asθ2, the conditions ofν2/ν1<0.55 and 0.040<θ2<θ1 are satisfied.
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