Image data correcting device for correcting image data to remove back projection without eliminating halftone image

• US 20020027670A1
• Filed: 08/28/2001
• Published: 03/07/2002
• Est. Priority Date: 09/04/2000
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Takahashi, Yuji, Kawamoto, Hiroyuki, Fukuda, Hiroaki
• Granted Patent: US 7,274,486 B2
• Time in Patent Office: Days
• US Class Current: 358/1.9
• CPC Class Codes: H04N 1/4095 Correction of errors due to scanning a two-sided document, i.e. show-through correction

Abstract

An image data correcting device eliminates a back projection image without eliminating an image corresponding to a low-intensity halftone image. An intensity difference detection part detects an intensity difference between first image data corresponding to a part of a predetermined small area and second image data corresponding to the remaining parts of the predetermined small area. A halftone detection part determining whether the first image data corresponds to a halftone image. An intensity change part changes an intensity of the first image data to a predetermined low intensity, when the intensity difference is equal to or smaller than a first predetermined value and the first image data does not correspond to the halftone image and the intensity of the first image data is equal to or smaller than a second predetermined value.

Claims

1. An image data correcting device comprising:

detecting means for detecting an intensity difference between first image data corresponding to a part of a predetermined small area and second image data corresponding to the remaining parts of the predetermined small area;

determining means for determining whether the first image data corresponds to a halftone image; and

intensity changing means for changing an intensity of the first image data to a predetermined low intensity, when the intensity difference is equal to or smaller than a first predetermined value and the first image data does not correspond to the halftone image and the intensity of the first image data is equal to or smaller than a second predetermined value.

2. The image data correcting device as claimed in claim 1, wherein the first predetermined value is determined so that an intensity of at least a part of an image other than the halftone image is equal to or greater than the first predetermined value and an intensity of the halftone image is smaller than the first predetermined value.

3. The image data correcting device as claimed in claim 1, wherein the second predetermined value is determined so that a difference between a first intensity difference of the first image data is equal to or greater than the second predetermined value when the first image data corresponds to the halftone image, wherein the first intensity difference is a difference between the intensity of the first image data and an average in intensities of the first image data and the second image data.

4. The image data correcting device as claimed in claim 1, wherein the predetermined small area is defined by a pixel matrix, and the first image data corresponds to one of pixels located in the center of the pixel matrix.

5. The image data correcting device as claimed in claim 4, wherein the pixel matrix is a 3×

3 matrix.

6. The image data correcting device as claimed in claim 1, wherein the predetermined low intensity is equal to or smaller than an intensity of a background of an image from which the predetermined small area is extracted.

7. The image data correcting device as claimed in claim 1, further comprising smoothing means for smoothing the first image data after the intensity of the first image data is changed.

8. The image data correcting device as claimed in claim 7, further comprising selecting means for selecting whether to output the first image data before smoothing or after smoothing.

9. The image data correcting device as claimed in claim 8, wherein the selecting means selects the first image data after smoothing when the first image data corresponds to an image other than the halftone image, and selects the first image data before smoothing when the first image data corresponding to the halftone image.

10. An image reading device comprising:

scanning means for scanning an original document to obtain image data and converting the image data into digital form; and

an image data correcting device correcting the image data supplied by the canning means,

wherein the image data correcting device comprising;

detecting means for detecting an intensity difference between first image data corresponding to a part of a predetermined small area and second image data corresponding to the remaining parts of the predetermined small area;

determining means for determining whether the first image data corresponds to a halftone image; and

intensity changing means for changing an intensity of the first image data to a predetermined low intensity, when the intensity difference is equal to or smaller than a first predetermined value and the first image data does not correspond to the halftone image and the intensity of the first image data is equal to or smaller than a second predetermined value.

11. An image forming apparatus comprising:

an image reading device generating image data by scanning an original document, said image reading device including an image data correcting device correcting the image data supplied by the image reading device; and

an image forming device forming a visible image based on the corrected image data supplied by the image data correcting device,

wherein the image data correcting device comprising;

detecting means for detecting an intensity difference between first image data corresponding to a part of a predetermined small area and second image data corresponding to the remaining parts of the predetermined small area;

determining means for determining whether the first image data corresponds to a halftone image; and

intensity changing means for changing an intensity of the first image data to a predetermined low intensity, when the intensity difference is equal to or smaller than a first predetermined value and the first image data does not correspond to the halftone image and the intensity of the first image data is equal to or smaller than a second predetermined value.