| 摘要 |
PROBLEM TO BE SOLVED: To efficiently use a diffraction grating and to make an optical system compact in terms of aberration by providing a 2nd group with the diffraction grating in the lens optical system performing zooming by changing a distance between a 1st group and a 2nd group. SOLUTION: This optical system is constituted to perform the zooming by changing the distance between the 1st group Gr1 and the 2nd group Gr2. The 1st group Gr1 is constituted of a biconcave negative lens and a positive meniscus lens which is convex to an object side. The 2nd group Gr2 is constituted of a bonded lens consisting of a biconvex positive lens and a negative meniscus lens which is concave to the object side, and is provided with the diffraction grating on a 6th surface r6 being a bonded surface. It is desirable to provide the 2nd group Gr2 with the lens bonded surface and the lens bonded surface with the diffraction grating in terms of excellently compensating chromatic aberration. In order to make the zoom type lens optical system compact, it is effective to use the diffraction grating in the 2nd group Gr2 in terms of compensating the aberration.
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