| 摘要 |
PURPOSE:To minimize the unequality in the low-pass effect by zooming and the degradation in image quality by disposing an optical low-pass filter in front of a 2nd lens group in proximity thereto and moving the low-pass filter integrally with the 2nd lens group at the time of executing zooming. CONSTITUTION:The low-pass filter 3 is disposed near an image pickup plane 5 in order to assure the space where a photographing lens makes variable power by movement of the 2nd lens group having a positive refracting power to an object side and corrects the fluctuation of the image plane arizing from zooming by movement of the 1st lens group having a negative refracting power cooperatively with the 2nd lens group 4 to an image side. The luminous flux passing the filter 3 can be relatively widened and the pitch of the phase grating of the filter 3 can be relatively coarsened by installing the filter 3 on the front side of the 2nd lens group 4 and, therefore, the degradation in the image quality by the diffracted light of the phase grating is suppressed.
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