Title:
【発明の名称】画像読取り装置
Document Type and Number:
Japanese Patent JP2679979
Kind Code:
B2
Abstract:
PURPOSE:To uniformly keep the gradation of a read picture regardless of the increase/decrease in the luminous quantity by controlling the input level of an A/D converter properly even when the luminous quantity is increased as well as the reduced luminous quantity incoming to an image sensor. CONSTITUTION:At first, a logarithmic transforming data at radiation onto a reference white plate 6 is fetched from a RAM 14 to a CPU 42. Then whether or not a maximum value DMAX in logarithmic transforming data is a value corresponding to a maximum output FFH is discriminated and when the value is not a value corresponding to the output yet, a CPU 42 designates each bit of control data D0-D7 so that output VOUT of the multiplier 41 is a maximum permissible input VMAX. When it is discriminated that the value dMAX corresponds already to the value FFH, since the input to the A/D converter 12 exceeds the value VMAX because of increased luminous quantity conversely, the control data D0-D7 are designated again to decrease the input level of the A/D converter 12 by a minute value K. Through the operation above, the A/D conversion output data at the radiation of white plate is approached limitelessly to the value FFH.
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Inventors:
Kenichi Suda
Hasegawa Shizuo
Nobuo Matsuoka
Hasegawa Shizuo
Nobuo Matsuoka
Application Number:
JP26984486A
Publication Date:
November 19, 1997
Filing Date:
November 14, 1986
Export Citation:
Assignee:
Canon Inc
International Classes:
H04N1/407; G06T1/00; H04N1/40; H04N1/46; H04N1/48; (IPC1-7): H04N1/407; G06T1/00
Domestic Patent References:
| JP60251768A | ||||
| JP61120579A | ||||
| JP62180662A | ||||
| JP62268269A |
Attorney, Agent or Firm:
Yoshikazu Tani