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US 5,402,175 AGranted
Automatic focusing device wherein lens movement is controlled in accordance with lens hunting
AssigneeCanon Kabushiki Kaisha
InventorTaeko Tanaka
Life of this patent
Estimating the term…
Abstract
An automatic focusing device including a focus detection circuit for detecting a focus state, and a motor for driving a focusing lens in accordance with an output from the focus detection circuit. The device controls the driving state of the motor in accordance with a result of comparing the amplitude of hunting of the focusing lens with a predetermined value when the direction of the drive of the focusing lens is reversed.
Claims21
An automatic focusing device, comprising:
- focus detection means for detecting a focus state;
- driving means for driving a focusing lens in accordance with an output from said focus detection means;
- comparison means for comparing a magnitude of hunting corresponding to a difference between two positions of the focusing lens with a predetermined value when a direction of the driving of the focusing lens is reversed;
- and
- control means for controlling the driving of said driving means in accordance with a result of said comparison means.
2 more elements
A video camera, comprising:
- lens driving means for driving a photographing lens;
- comparison means for comparing a magnitude of hunting corresponding to a difference between two positions of the photographing lens with a predetermined value when a driving direction of the photographing lens is reversed;
- control means for controlling driving speed of the photographing lens by said driving means in accordance with a result of said comparison means;
- and
- changing means for changing the predetermined value in accordance with a depth of field of the photographing lens.
2 more elements
An automatic focusing device, comprising:
- focus detection means for detecting a focus state by extracting from a picture signal a focus signal which changes in accordance with the focus state;
- a focusing motor for driving a focusing lens, in a lens system, in accordance with an output from said focus detection means;
- comparison means for comparing an magnitude of hunting corresponding to a difference between two positions of the focusing lens, when the focusing lens oscillates back and forth in its moving direction, with a predetermined value;
- detection means for detecting the duration of the hunting when the focusing lens moves back and forth in its moving direction;
- control means for controlling drive speed of said focusing motor in accordance with outputs from said comparison means and said detection means;
- and
- correction means for correcting the predetermined value in accordance with depth of field of the focusing lens.
4 more elements
An automatic focusing device, comprising:
- focus detection means for detecting a focus state;
- driving means for driving a focusing lens in accordance with an output from said focus detection means;
- determination means for determining a magnitude of hunting of the focusing lens between two positions thereof when hunting of the focusing lens, in its moving direction, is detected;
- and
- control means for controlling a speed of said driving means in accordance with a result of the determination by said determination means.
2 more elements
Dependencies are inferred from the claim text.