Automatic focusing apparatus

Details Automatic focusing apparatus Automatic focusing apparatus

1990-02-27

1992-01-21

Griffin, Donald A.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358227, G03B 300, G03B 1318

Patent

active

050831500

ABSTRACT:
An automatic focusing apparatus of this invention includes a photographing optical system for forming an optical image of an object, an image pickup element for converting the optical image formed by the photographing optical system into an electrical signal, a drive circuit for changing a relative position between the photographing optical system and the image pickup element, a reading circuit for reading the electrical signals at different relative positions as image signals from the image pickup element, a frequency extracting circuit for extracting frequency components of the same specific bands from the image signals read by the reading circuit (34), a focusing signal generator for adding the plurality of frequency components extracted by the frequency extracting circuit to generate a focusing signal, a filtering circuit for filtering the focusing signal to generate a filtering signal, and a microprocessor for performing an in-focus detection operation using a plurality of signal values of the filtering signal, calculating a defocus amount, and outputting a control signal to the drive circuit.

REFERENCES:
patent: 4183642 (1980-01-01), Fukuoka
patent: 4422097 (1983-12-01), Inuiya
patent: 4843413 (1989-06-01), Walther
patent: 4903135 (1990-02-01), Ohtake et al.
NHK Technical Report, vol. 17, No. 1 (Ser. No. 86), pp. 21-37, 1965.
Minolta Techno Report (1986), Focus Detection by Phase Difference Method, T. Ishida, pp. 33-39.

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