Vari-focal lens control system with lens driving and magnificati

Details Vari-focal lens control system with lens driving and magnificati Vari-focal lens control system with lens driving and magnificati

1992-09-23

1993-12-28

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

354402, G01J 120

Patent

active

052742237

ABSTRACT:
A control system for vari-focal lens can keep a vari-focal lens in focus during magnification change, and can conduct quick focusing even if a distance measurement is not possible in a phase difference detection method. A focusing correction calculation circuit calculates two data, one of which is a focusing lens position datum obtained by a focusing lens position detection device and the other of which is a magnification changing lens group position datum obtained by a magnification changing lens position detection device, to obtain a correction amount datum and a correction focusing direction datum. Another calculation circuit obtains a phase difference datum based on a phase difference detection datum detected by a phase difference detector. If a judgement circuit judges either that the distance measurement is not possible, that the phase difference is under calculation, or that the phase difference is under detection, a focusing correction is effected based on the correction amount datum and the correction focusing direction datum. If the judgement circuit judges otherwise, the focusing is effected based on the datum obtained from the phase difference detection datum.

REFERENCES:
patent: 4881799 (1989-11-01), Ohno et al.
patent: 4899190 (1990-02-01), Hata
patent: 5053800 (1991-10-01), Ishida et al.
patent: 5053801 (1991-10-01), Ishida et al.

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