Color image reading apparatus with a plurality of line sensors in which a white balance operation is performed by determining amplifier gains while reading a white reference plate

• US 4,734,762 A
• Filed: 06/12/1987
• Issued: 03/29/1988
• Est. Priority Date: 10/20/1982
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Aoki, Takao, Ikeda, Yoshinori, Tokuhara, Mitsuhiro
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): Svihla, Randall S.
• Application Number:
  US07/061,042
• Time in Patent Office: 291 Days
• Field of Search: 358/29, 358/75, 358/163, 358/80, 358/29 C
• US Class Current: 358/516
• CPC Class Codes: H04N 1/40 Picture signal circuits H04N1/387 takes precedence
• CPC Class Codes: H04N 1/401 Compensating positionally unequal response of the pick-up or reproducing head H04N1/403 takes precedence
• CPC Class Codes: H04N 1/482 using the same detector device sequentially for different colour components

Abstract

A color image reading apparatus with a plurality of line sensors and an associated plurality of rotary color filter disks produces a plurality of sequential color component signals from each line sensor. An amplifier with an adjustable gain is provided for each of the line sensors. A white balance operation is performed prior to reading a color document by determining gains for each of the amplifiers to use in amplifying corresponding ones of the sequential color component signals on the basis of a plurality of reference color component signals generated by reading a white reference plate with the line sensors. The determined gains are stored in a memory as digital data. The data is read out and used to control the gains of the amplifiers while a color document is being read. Color balance correction switch units enable an operator to selectively modify the determined gains in order to adjust the color balance of the color component signals.

Claims

1. A color image reading apparatus comprising:

a plurality of linear sensor means for reading a color document, each of said linear sensor means photoelectrically reading a different portion of a line of the color document in a divided manner and generating a plurality of color component signals representing colors on the color document;

a plurality of amplifying means each for amplifying said plurality of color component signals generated by a respective one of said plurality of linear sensor means;

determining means for determining gains for said plurality of amplifying means to use in amplifying corresponding ones of said plurality of color component signals on the basis of a plurality of reference color component signals generated by reading a reference member having a reference density with said plurality of linear sensor means; and

correcting means for causing each of said plurality of amplifying means to amplify said plurality of color component signals using the respective gains determined by said determining means, thereby correcting the level of each of said plurality of color component signals representing colors on the color document generated by each of said plurality of linear sensor means.

2. An apparatus according to claim 1, further comprising a document table for supporting the color document so as to be read by said plurality of linear sensor means, wherein said reference member is disposed at a position associated with said document table so as to be read by said plurality of linear sensor means.

3. An apparatus according to claim 1, wherein each of said plurality of linear sensor means comprises color separation means for separating color components of the colors on the color document.

4. An apparatus according to claim 1, wherein said correcting means corrects for non-uniformity in the levels of color component signals generated by said plurality of linear sensor means when said plurality of linear sensor means are all generating the same color component signal.

5. An apparatus according to claim 1, wherein said determining means includes storage means for storing information representing the determined gains.

6. An apparatus according to claim 1, wherein each of said plurality of linear sensor means reads the corresponding different portion of a line of the color document by electrical scanning thereof in a main scanning direction, further comprising means for mechanically moving said plurality of linear sensor means relative to the color document in a subscanning direction perpendicular to the main scanning direction, wherein said plurality of linear sensor means reads the entire color document by means of the electrical scanning in the main scanning direction and the relative mechanical movement in the subscanning direction provided by said moving means.

7. An apparatus according to claim 1, further comprising setting means for setting respective desired adjustments to the levels of said plurality of color component signals amplified by said plurality of amplifying means, wherein said determining means modifies the determined gains on the basis of the desired adjustments set by said setting means.

8. An apparatus accoording to claim 1, further comprising means for recording a color image on a recording material on the basis of the plurality of color component signals amplified by said plurality of amplifying means.

9. An apparatus according to claim 1, further comprising means for converting the plurality of color component signals amplified by said plurality of amplifying means to digital color component signals.

10. An apparatus according to claim 1, wherein said determining means causes said plurality of linear sensor means to read the reference member prior to reading the color document in order to determine the gains for said plurality of amplifying means to use in amplifying corresponding ones of said plurality of color component signals.

11. An apparatus according to claim 1, wherein each of said plurality of linear sensor means is operable to read the color document a plural number of times in order to generate said plurality of color component signals.