Photography – With exposure objective focusing means – focusing aid – or... – Optical detail with photoelement system
Reexamination Certificate
2005-12-06
2005-12-06
Perkey, W. B. (Department: 2851)
Photography
With exposure objective focusing means, focusing aid, or...
Optical detail with photoelement system
C396S121000, C250S201700
Reexamination Certificate
active
06973264
ABSTRACT:
First to third liquid crystal filters are arranged at first to third different distances from a predeterminate image formation surface. Light flux passing through the liquid crystal filters is received by a photodiode and converted into an electric signal. A variable-density stripe pattern of a predetermined space frequency is formed on the first liquid crystal filter while the second and the third liquid crystal filter are in the state of entire transparency and a first signal is output from the photodiode. Similarly, a variable-density stripe pattern is formed on the second liquid crystal filter while the first and the third liquid crystal filter are in the state of entire transparency and a second signal is output. Similarly, a variable-density stripe pattern is formed on the third liquid crystal filter while the first and the second liquid crystal filter are in the state of entire transparency and a third signal is output. According to the first, second, and third signals, a focal point position is calculated.
REFERENCES:
patent: 4453818 (1984-06-01), Hayashi et al.
patent: 4488799 (1984-12-01), Suzuki et al.
patent: A 59-034504 (1984-02-01), None
patent: A 04-333010 (1992-11-01), None
patent: A 07-084177 (1995-03-01), None
Nikon Corporation
Oliff & Berridg,e PLC
Perkey W. B.
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