Optical: systems and elements – Lens – With variable magnification
Patent
1990-10-16
1991-11-26
Ben, Loha
Optical: systems and elements
Lens
With variable magnification
354400, 359698, 359701, G02B 1500
Patent
active
050678027
ABSTRACT:
A zoom lens comprises a varifocal lens section having a variator lens unit for varying the focal length of the entire system and a compensator lens unit for compensating for the image shift with zooming movement of the variator lens unit, a relay lens section using a light beam from the varifocal lens section for forming an object image on a predetermined plane, a lens unit constituting at least part of the relay lens section being made to be an axially movable adjusting lens unit, and a focus adjusting mechanism for axially moving the adjusting lens unit to effect focus adjustment, wherein information about the focus deviation with variation of the focal length by the varifocal lens section is obtained in each focal length position and memorized in a memory, whereby the focus adjustment is carried out in such a way that the predetermined focus deviation information is selected from the memory based on a signal output from a focal length detecting circuit for detecting the zooming position of the varifocal lens section, the amount of movement of the adjusting lens unit is computed by a computing circuit based on the selected focus deviation information and the signal output from an adjusting lens unit detecting circuit for detecting the axial position of the adjusting lens unit, and the adjusting lens unit is moved by a drive device based on a signal output from the computing circuit.
REFERENCES:
patent: 4054372 (1977-10-01), Schroeder
patent: 4161756 (1979-07-01), Thomas
patent: 4740064 (1988-09-01), Kono et al.
patent: 4957354 (1990-09-01), Matsuyama
Ben Loha
Canon Kabushiki Kaisha
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