Image reader that stores sets of luminance correction data corresponding to document a surface height

• US 5,969,829 A
• Filed: 09/18/1997
• Issued: 10/19/1999
• Est. Priority Date: 09/19/1996
• Status: Expired due to Term

• Current Assignee: Minolta Co., Ltd. (Konica Minolta Inc.)
• Original Assignee: Minolta Co., Ltd. (Konica Minolta Inc.)
• Inventors: Kamon, Koichi, Matsuda, Shinya
• Primary Examiner(s): Coles, Edward L.
• Assistant Examiner(s): Lee, Cheukfan
• Application Number:
  US08/933,263
• Time in Patent Office: 761 Days
• Field of Search: 358/488, 358/497, 358/444, 358/475, 358/474, 358/493, 358/464, 358/465, 355/25, 355/55, 355/82, 399/362, 250/208.1, 250/234-236
• US Class Current: 358/475
• CPC Class Codes: H04N 1/1013 with sub-scanning by translatory movement of at least a part of the main-scanning components H04N1/107 takes precedence
• CPC Class Codes: H04N 1/1043 of a sensor array
• CPC Class Codes: H04N 1/193 using electrically scanned linear arrays , e.g. linear CCD arrays
• CPC Class Codes: H04N 1/387 Composing, repositioning or otherwise geometrically modifying originals
• CPC Class Codes: H04N 1/40056 Circuits for driving or energising particular reading heads or original illumination means H04N1/401, H04N1/407 take precedence
• CPC Class Codes: H04N 2201/0434 specially adapted for scanning pages of a book

Abstract

An image reader capable of outputting excellent quality read images, without illumination irregularities, similar to that of flat documents even when the document surface is curved as in the case of book-like documents. An image reader provided with a memory to store correction data to correct differences of illumination of each pixel of a document image, and which corrects the read information of each pixel in a document image using correction data corresponding to the measured height of a document surface among correction data stored in the memory. For one aspect, this image reader is constructed so as to correct a group of read information corresponding to a set of pixels arrayed in one direction by excluding specific frequencies among the illumination distribution from the set.

Claims

1. An image reader which reads a document surface of an open book-like document placed on a document platen in a face upward condition and detects a height of the document surface, said image reader comprising:

illuminating means for illuminating the document surface, said illuminating means having illuminance irregularity;

reading means for converting an image of the document surface to image data;

memory means for storing a plurality of sets of illuminance correction data to correct differences of illuminance of image data of the document surface, each set corresponding to a height of the document surface;

detecting means for detecting a height distribution of the document surface; and

correcting means for correcting the image data using said illuminance correction data sets based on the height distribution.

2. The image reader as claimed in claim 1, wherein said detecting means comprises a mirror reflecting a side view of the document to said image sensing means.

3. The image reader as claimed in claim 1, wherein said reading means comprises a line sensor.

4. The image reader as claimed in claim 1, wherein said reading means comprises an area sensor.

5. The image reader as claimed in claim 1, further comprising a filter which removes a high frequency noise from the read image data.

6. An image reader which reads a document surface of an open book-like document placed on a document platen in a face upward condition and detects a height of the document surface, said image reader comprising:

a line sensor which reads the document surface, said line sensor extending in a main scanning direction and being moved in a sub-scanning direction;

illuminating means for illuminating the document surface, said illuminating means having an illumination irregularity with respect to the main scanning direction;

memory means for storing a plurality of sets of illuminance correction data with respect to the main scanning direction, each set corresponding to a height of the document surface;

detecting means for detecting a height distribution of the document surface with respect to the sub-scanning direction; and

correcting means for correcting the image data read by the line sensor using said illumination correcting data sets based on the height distribution.

7. The image reader as claimed in claim 6, wherein said detecting means comprises a mirror reflecting a side view of the document to said image sensing means.

8. The image reader as claimed in claim 6, further comprising a filter which removes a high frequency noise from the read image data.

9. A method of processing an image of an open book-like document placed on a document platen of an image reader in a face upward condition, the method comprising the steps of:

memorizing a plurality of sets of illuminance correction data, each set corresponding to a height of the document surface;

illuminating the document surface;

detecting a height distribution of the document surface;

reading the document and outputting image data; and

correcting the image data using said luminance correction data sets based on the height distribution.

10. A method of processing an image of an open book-like document placed on a document platen of an image reader in a face upward condition, the method comprising the steps of:

reading the document surface by moving a line sensor in a sub-scanning direction, said line sensor extending in a main scanning direction;

illuminating the document surface with an illuminating light, wherein the illuminating light has an illumination irregularity with respect to the main scanning direction;

storing a plurality of sets of illuminance correction data with respect to the main scanning direction, each set corresponding to a height of the document surface;

detecting a height distribution of the document surface with respect to the sub-scanning direction; and

correcting the image data read by the line sensor using said illumination correcting data sets based on the height distribution.