Image reading apparatus having a plurality of line sensors and means for correcting crosstalk therebetween

• US 4,974,072 A
• Filed: 10/11/1988
• Issued: 11/27/1990
• Est. Priority Date: 10/14/1987
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Hasegawa, Shizuo
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): VU, KIM Y
• Application Number:
  US07/255,977
• Time in Patent Office: 777 Days
• Field of Search: 358/75, 358/77, 358/80, 358/482, 358/213.15, 358/213.18
• US Class Current: 358/514
• CPC Class Codes: H04N 1/56 Processing of colour picture signals H04N1/52 takes precedence
• CPC Class Codes: H04N 23/84 for processing colour signals
• CPC Class Codes: H04N 23/88 for colour balance, e.g. white-balance circuits or colour temperature control
• CPC Class Codes: H04N 5/16 Circuitry for reinsertion of dc and slowly varying components of signal; Circuitry for preservation of black or white level

Abstract

An image reading apparatus has a plurality of line sensors for reading an image, a pulse generator for independently driving the plurality of line sensors under the control of a CPU, and black level correction circuits for correcting black levels of output image signals from the plurality of line sensors. The black level correction circuits perform different black level correction operations for crosstalk portions than for other portions generated by the plurality of line sensors.

Claims

1. An image reading apparatus comprising:

a plurality of line sensors for reading an image;

driving means for independently driving said plurality of line sensors; and

correcting means for correcting black levels of output image signals from said plurality of line sensors,

wherein said correcting means performs different black level correction operations for crosstalk portions than for other portions generated by said plurality of line sensors.

2. An apparatus according to claim 1, wherein said plurality of line sensors comprise different color separation filters.

3. An apparatus according to claim 1, wherein said driving means drives said plurality of line sensors in accordance with a read magnification of the image.

4. An apparatus according to claim 1, wherein said correcting means corrects the black levels in accordance with black reference signals output from said plurality of line sensors.

5. An apparatus according to claim 1, wherein each of said plurality of line sensors reads a different image line of an original.

6. An image reading apparatus comprising:

a plurality of line sensors for reading an image;

memory means for storing black reference signals output from said plurality of line sensors; and

correcting means for correcting black levels of output image signals from said plurality of line sensors on the basis of the black reference signals stored in said memory means,

wherein said correcting means divides at least one black reference signal stored in said memory means into a plurality of portions and corrects the black levels of the corresponding image signals on the basis of the divided black reference signal portions.

7. An apparatus according to claim 6, wherein said plurality of line sensors comprise different color separation filters.

8. An apparatus according to claim 6, wherein said correcting means divides the at least one black reference signal into crosstalk portions and other portions generated by said plurality of line sensors.

9. An apparatus according to claim 6, wherein each of said plurality of line sensors reads a different image line of an original.

10. An image reading apparatus comprising:

a plurality of line sensors for reading an image;

driving means for independently driving said plurality of line sensors; and

a plurality of correcting means, respectively coupled to said plurality of line sensors, for correcting black levels of output image signals from said plurality of line sensors,

wherein each of said plurality of correcting means performs black level correction also utilizing crosstalk portions provided by line sensors other than the line sensor corresponding to said each correcting means.

11. An apparatus according to claim 10, wherein said plurality of line sensors comprise different color separation filters.

12. An apparatus according to claim 10, wherein said driving means drives said plurality of line sensors in accordance with a read magnification of the image.

13. An apparatus according to claim 10, wherein said correcting means performs different black level correction operations for the crosstalk portions than for other portions.

14. An apparatus according to claim 10, wherein each of said plurality of line sensors reads a different image line of an original.