Image reading apparatus for correcting images on both sides of a document sheet

• US 7,626,735 B2
• Filed: 09/14/2004
• Issued: 12/01/2009
• Est. Priority Date: 01/21/2004
• Status: Expired due to Fees

• Current Assignee: Fuji Xerox Company Limited (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Xerox Company Limited (Fujifilm Holdings Corporation)
• Inventors: Onishi, Ayumi, Saito, Masato, Matsubara, Yoshitake, Mizuhashi, Satoshi, Mizuta, Yasuhisa, Furuoya, Sadao, Sodeura, Minoru
• Primary Examiner(s): Zimmerman; Mark K
• Assistant Examiner(s): HON, MING Y
• Application Number:
  US10/939,506
• Publication Number:
  US 20050157319A1
• Time in Patent Office: 1,904 Days
• Field of Search: 358/400, 358/408, 358/443, 358/447, 358/448, 358/462, 358/471, 358/474, 358/500, 358/512, 358/519, 358/521
• US Class Current: 358/474
• CPC Class Codes: H04N 1/12 using the sheet-feed movement or the medium-advance or the drum-rotation movement as the slow scanning component, e.g. arrangements for the main-scanningsheet-feed movement by translatory movement of a flat picture-bearing surface H04N1/1008; main-scanning using oscillating or rotating mirrors H04N1/113; using multi-element arrays H04N1/19
• CPC Class Codes: H04N 1/192 Simultaneously or substantially simultaneously scanning picture elements on one main scanning line
• CPC Class Codes: H04N 1/2034 at identical corresponding positions, i.e. without time delay between the two image signals
• CPC Class Codes: H04N 1/207 Simultaneous scanning of the original picture and the reproduced picture with a common scanning device
• CPC Class Codes: H04N 1/4095 Correction of errors due to scanning a two-sided document, i.e. show-through correction

Abstract

The invention provides an image reading apparatus includes a feeder that feeds a sheet, a transfer path on which the sheet fed by the feeder is transferred, a first reading unit that captures a first image on a first face of the sheet from one side of the transfer path to obtain first image data, a second reading unit that captures a second image on a second face of the sheet from the other side of the transfer path to obtain second image data, and a correction unit that substantially equalizes image density of the first image data and that of the second image data in a case where the first image and the second image are captured at a single transfer of the sheet through the transfer path.

Claims

1. An image reading apparatus comprising:

a feeder that feeds a sheet;

a transfer path on which the sheet fed by the feeder is transferred;

a first reading unit positioned on a first side of the transfer path that captures an image on a face of the sheet from the first side of the transfer path, the first reading unit including at least one color sensor for capturing color image data and a first monochrome sensor for capturing monochrome image data;

a second reading unit positioned on a second side of the transfer path that captures an image on a face of the sheet from the second side of the transfer path, the second reading unit consisting of a second monochrome sensor for capturing monochrome image data;

a mode selection unit for selecting a monochrome mode or a color mode;

an inversion unit in the transfer path that inverts the sheet; and

a correction unit that substantially equalizes image density of captured first image data and captured second image data,

wherein;

when the monochrome mode is selected, the captured first image data is captured by the first monochrome sensor in the first reading unit and the captured second image data is captured by the second monochrome sensor in the second reading unit on a single transfer of the sheet through the transfer path, and

when the color mode is selected, the captured first image data is captured by the at least one color sensor in the first reading unit on a first transfer of the sheet through the transfer path, the sheet is inverted by the inversion unit and the captured second image data is captured by the at least one color sensor in the first reading unit on a second transfer of the sheet through the transfer path.

2. The image reading apparatus according to claim 1, wherein the correction unit corrects one of the first image data and the second image data so that the image density of the first image data is in a range of ±

7% of the image density of the second image data.

3. The image reading apparatus according to claim 1, wherein the correction unit corrects the first monochrome image data so that the image density of the first monochrome image data is in a range of ±

7% of the image density of the second monochrome image data.

4. The image reading apparatus according to claim 1, wherein the first image data obtained by the first reading unit has a first image density and the second image data obtained by the second reading unit has a second image density, the first image density being different from the second image density.

5. The image reading apparatus according to claim 1, wherein the first image data is corrected to substantially equalize the image density of the first image data to that of the second image data based on the image density of the second image data.

6. The image reading apparatus of claim 1, wherein the correction unit selects either an image density of the captured first image data or the captured second image data as a target density, and corrects the other of the first captured image data or the captured second image data using the image density of the selected captured image data as a reference.

7. The image reading apparatus of claim 6, wherein an output value of a sensor that is not selected is corrected using an LUT to substantially equalize the image density of the captured first image data and captured second image data.

8. An image reading apparatus comprising:

a transfer path on which a sheet is transferred;

a first reading unit positioned on a first side of the transfer path that captures an image on a face of the sheet, the first reading unit including a first light source for emitting light to the face of the sheet from the first side of the transfer path and a plurality of sensors for receiving reflected light from the sheet, the plurality of sensors comprising at least one color sensor for capturing color image data and a first monochrome sensor for capturing monochrome image data;

a second reading unit positioned on a second side of the transfer path that captures an image on a face of the sheet, the second reading unit including a second light source for emitting light to the face of the sheet from the second side of the transfer path and a sensor for receiving a reflected light from the sheet, the sensor consisting of a second monochrome sensor for capturing monochrome image data;

a mode selection unit for selecting a monochrome mode or a color mode;

an inversion unit in the transfer path that inverts the sheet; and

a correction unit that corrects captured first image data so as to substantially equalize image density of the captured first image data with that of captured second image data,

wherein;

when the monochrome mode is selected, the captured first image data is captured by the first monochrome sensor in the first reading unit and the captured second image data is captured by the second monochrome sensor in the second reading unit on a single transfer of the sheet through the transfer path,

when the color mode is selected, the captured first image data is captured by the at least one color sensor in the first reading unit on a first transfer of the sheet through the transfer path, the sheet is inverted by the inversion unit and the captured second image data is captured by the at least one color sensor in the first reading unit on a second transfer of the sheet through the transfer path, and

the second light source has a wider emission wavelength range than the first light source.

9. The image reading apparatus according to claim 8, wherein

the first light source is a xenon lamp, and

the second light source is an LED.

10. The image reading apparatus according to claim 8, wherein

the plurality of sensors includes a first image sensor for capturing the reflected light through a minification optical system, and

the second monochrome sensor is a second image sensor for capturing the reflected light at a closer position than the first image sensor.

11. The image reading apparatus according to claim 8, wherein the correction unit corrects the first image data so that the image density of the first image data is in a range of ±

7% of the image density of the second image data.

12. The image reading apparatus according to claim 8, wherein the first image data obtained by the first reading unit has a first image density and the second image data obtained by the second reading unit has a second image density, the first image density being different from the second image density.

13. The image reading apparatus according to claim 8, wherein the first image data is corrected to substantially equalize the image density of the first image data to that of the second image data based on the image density of the second image data.

14. An image reading apparatus comprising:

a feeder that feeds a sheet;

a transfer path on which the sheet fed by the feeder is transferred;

a first reading unit positioned on a first side of the transfer path that captures an image on a face of the sheet from the first side of the transfer path to obtain at least one of color image data or first monochrome image data;

a second reading unit positioned on a second side of the transfer path that captures an image on a face of the sheet from the second side of the transfer path to obtain second monochrome image data;

a mode selection unit for selecting a monochrome mode or color mode;

an inversion unit in the transfer path that inverts the sheet; and

a correction unit that (1) corrects the first monochrome image data captured by the first reading unit and the second monochrome image data captured by the second reading unit in the monochrome mode on a single transfer of the sheet through the transfer path, to substantially equalize image density of the first monochrome image data and the second monochrome image data, and (2) corrects first color image data captured by the first reading unit and second color image data captured by the first reading unit in the color mode on two transfers of the sheet through the transfer path with an inversion in between, to substantially equalize image density of the first color image data and the second color image data.

15. The image reading apparatus according to claim 14, further comprising:

a generating unit that, in the monochrome mode, generates a correction value for equalizing the image density of the first monochrome image data and the second monochrome image data, wherein

the correction unit corrects the first monochrome image data with the correction value.

16. The image reading apparatus according to claim 15, wherein the correction unit corrects the first monochrome image data so that the image density of the first monochrome image data is in a range of ±

7% of the image density of the second monochrome image data.

17. The image reading apparatus according to claim 14, wherein the correction unit corrects the first monochrome image data so that the image density of the first monochrome image data is in a range of ±

7% of the image density of the second monochrome image data.

18. The image reading apparatus according to claim 14, wherein the first image data obtained by the first reading unit has a first image density and the second image data obtained by the second reading unit has a second image density, the first image density being different from the second image density.

19. The image reading apparatus according to claim 14, wherein the first image data is corrected to substantially equalize the image density of the first image data to that of the second image data based on the image density of the second image data.

20. An image reading apparatus comprising:

a feeder that feeds a sheet;

a transfer path on which the sheet fed by the feeder is transferred;

a first reading unit positioned on a first side of the transfer path that captures an image on a face of the sheet from the first side of the transfer path, the first reading unit including at least one color sensor for capturing color image data and a first monochrome sensor for capturing monochrome image data;

a second reading unit positioned on a second side of the transfer path that captures an image on a face of the sheet from the second side of the transfer path, the second reading unit consisting of a second monochrome sensor for capturing monochrome image data;

a mode selection unit for selecting a color mode or a monochrome mode;

an inversion unit in the transfer path that inverts the sheet; and

an acceptor that accepts a selection concerning correcting an image density of captured image data,

wherein;

when the monochrome mode is selected, first image data is captured by the first monochrome sensor in the first reading unit and second image data is captured by the second monochrome sensor in the second reading unit on at a single transfer of the sheet through the transfer path,

when the color mode is selected, first image data is captured by the at least one color sensor in the in the first reading unit on a first transfer of the sheet through the transfer path, the sheet is inverted by the inversion unit and second image data is captured by the at least one color sensor in the first reading unit on a second transfer of the sheet through the transfer path, and

the acceptor accepts a selection concerning whether (a) to bring image density of the captured second image data close to that of the captured first image data, or (b) to bring the image density of the captured first image data close to that of the captured second image data.

21. The image reading apparatus according to claim 20, wherein the first reading unit and the second reading unit have light sources for emitting light to the sheet, respectively, each having a different emission characteristic.

22. The image reading apparatus according to claim 20, wherein the first reading unit and the second reading unit have sensors for capturing the image on the sheet, respectively, each of the first and second reading units having a different resolution characteristic.

23. The image reading apparatus according to claim 20, wherein the acceptor further accepts a selection concerning whether (a) to prioritize sharpness of the image, or (b) to prioritize reproducibility of the image density.

24. The image reading apparatus according to claim 20, wherein the first image data obtained by the first reading unit has a first image density and the second image data obtained by the second reading unit has a second image density, the first image density being different from the second image density.

25. The image reading apparatus according to claim 20, wherein the first image data is corrected to substantially equalize the image density of the first image data to that of the second image data based on the image density of the second image data.