Automatic focusing device
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United States of America Patent
Stats
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Nov 16, 1982
Grant Date -
N/A
app pub date -
Apr 25, 1980
filing date -
Apr 28, 1979
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
An automatic focusing device controls the setting of an actuating member to effect automatic focusing of a camera lens and is used in conjunction with a focus detecting unit which produces a focus detection signal corresponding to the object distance by photoelectrically comparing optical images transmitted by stationary and movable mirror systems. The automatic focusing device comprises pulse generating circuitry for generating pulses at a fixed repetition rate, a first counting circuit for counting pulses such that the number of pulses counted is a function of the angle of displacement of a movable mirror of the movable mirror system during a range scanning operation, and a second counting circuit connected to receive and memorize the pulse count counted by the first counting circuit when a focus detection signal is produced by the focus detecting unit and operative to count pulses such that the number of pulses counted is a function of the extent of movement of the actuating member. A detector detects when the pulse count counted by the second counting circuit reaches a predetermined count and produces a corresponding output signal which is used to terminate the movement of the actuating member to thereby effect focusing of the camera lens.
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