Title:
IRIS CONTROL METHOD AND ELECTRONIC IRIS CONTROL CIRCUIT FOR VIDEO CAMERA
Document Type and Number:
Japanese Patent JP3158702
Kind Code:
B2
Abstract:
PURPOSE: To narrow an error range corresponding to electric charge storage time by fluctuating the difference between an upper side reference value and a lower side reference value so as to become larger as the electric charge storage time is shortened corresponding to the electric charge storage time.
CONSTITUTION: A voltage corresponding to the brightness of an entire screen is outputted from a low-pass filter 9. The voltage is compared with reference voltages V1 and V2 by comparator circuits 11 and 12 and when the output voltage of the low-pass filter 9 is higher than the upper side reference voltage V1, that is, when it is too bright, an instruction for increasing the count value of a count value specifying circuit 14 is issued from a decoder 13 and when it is lower than the reference voltage V2, the instruction for decreasing the count value of the count value specifying circuit 14 is issued from the decoder 13. Then, a reference value specifying circuit 18 generates the upper side reference voltage V1 and the lower side reference voltage V2 corresponding to exposure time, that is, shutter gain difference, applies them through the low-pass filters 19 and 20 to the reference voltage input terminal (-) of the comparator circuits 11 and 12 and changes the width of a neutral zone.
Inventors:
Masanori Yamaguchi
Application Number:
JP23539992A
Publication Date:
April 23, 2001
Filing Date:
August 10, 1992
Export Citation:
Assignee:
ソニー株式会社
International Classes:
H04N5/238; H04N5/335; H04N5/351; H04N5/353; H04N5/357; H04N5/372; H04N5/378; (IPC1-7): H04N5/335
Domestic Patent References:
| JP432380A | ||||
| JP548975A | ||||
| JP595508A | ||||
| JP4293372A |
Attorney, Agent or Firm:
Hideaki Ogawa