Patent
1978-07-26
1980-04-08
Sacher, Paul A.
350207, G02B 1516
Patent
active
041969693
ABSTRACT:
The present invention provides a compact zoom lens which exhibits only small distortion aberration. The present invention comprises, in order from the object side, a first lens group having a negative focal length, a second lens group having a positive focal length, and a third lens group having a negative focal length. The overall focal length is variable by moving mechanically the first, second and third lens groups, but the position of the image surface is maintained constant. In the zoom lens of the present invention, the resultant focal length of the first and second lens groups is positive during the entire zoom range, and the aerial spaces between the first and second lens groups and between the second and third lens groups, respectively, are reduced so that the overall viewing angle is also reduced. The first lens group is composed of a negative lens component and a positive lens component in order from the object side. The negative lens component is constructed using two negative lenses. The second lens group is composed of positive, negative and positive lens components in order from the object side. The first positive lens component is constructed using three positive lenses. The third positive components are constructed using two positive lenses. The third lens group is composed, in order from the object side, of a positive lens having a strong convex surface on the image side in the direction of the image, a negative double concave lens, and a positive lens having a strong convex surface on the object side in the direction of the object.
REFERENCES:
patent: 3918797 (1975-11-01), Takano
patent: 3918798 (1975-11-01), Takano
Asahi Kogaku Kogyo Kabushiki Kaisha
Sacher Paul A.
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