Image processing apparatus

• US 6,433,896 B1
• Filed: 06/10/1998
• Issued: 08/13/2002
• Est. Priority Date: 06/10/1997
• Status: Expired due to Term

• Current Assignee: Minolta Co., Ltd. (Konica Minolta Inc.)
• Original Assignee: Minolta Co., Ltd. (Konica Minolta Inc.)
• Inventors: Mishima, Nobuhiro, Ueda, Kazuhiro, Hirota, Soh, Tohyama, Daisetsu
• Primary Examiner(s): Lee, Cheukfan
• Application Number:
  US09/095,311
• Time in Patent Office: 1,525 Days
• Field of Search: 358/488, 358/449, 358/401, 382/289, 382/296, 382/297, 382/293, 382/286, 382/295, 399/17, 399/81, 399/371
• US Class Current: 358/488
• CPC Class Codes: G06V 10/24 Aligning, centring, orientation detection or correction of the image
• CPC Class Codes: H04N 1/00384 Key input means, e.g. buttons or keypads electromechanical details of key input means in general H01H13/00
• CPC Class Codes: H04N 1/00411 the display also being used for user input, e.g. touch screen
• CPC Class Codes: H04N 1/00681 Detecting the presence, position or size of a sheet or correcting its position before scanning H04N1/047 takes precedence; mode signalling H04N1/333; skew detection or correction in image signals H04N1/3878
• CPC Class Codes: H04N 1/00702 Position
• CPC Class Codes: H04N 1/0071 Width
• CPC Class Codes: H04N 1/00713 Length
• CPC Class Codes: H04N 1/00718 Skew
• CPC Class Codes: H04N 1/00737 using the scanning elements as detectors
• CPC Class Codes: H04N 1/00748 Detecting edges, e.g. of a stationary sheet
• CPC Class Codes: H04N 1/00753 of a sheet relative to a particular backgroud
• CPC Class Codes: H04N 1/00816 Determining the reading area, e.g. eliminating reading of margins
• CPC Class Codes: H04N 1/3878 Skew detection or correction

Abstract

In an image processing apparatus, an image reading unit reads a document put on a platen glass to generate image data, and a detector in the image reading unit detects offset, tilt angle and document area of the document put on the platen glass. A rotation angle is set based on the image data of a document. The entire document area is determined based on a portion of the document which exists within the image reading area when the document extends beyond the image reading area. The document area can be detected even if a document is not rectangular. For example, a slope of the document is determined based on the detected longest segment. In order to solve the unequal reading pitch, the longest segment is selected in the segments having a slope smaller than a predetermined angle relative to the subscan direction. Then, the image data are corrected according to the above result.

Claims

1. An image processing apparatus comprising:

a document setter, having an image reading area on which a document is put;

an image reader which reads the document put on said document setter;

a detector which detects an offset of the document from a standard position based on image data of the document read by said image reader, said detector including a means for determining an area of the entire document based on a portion of the document which exists within the image reading area in the case when the document extends beyond the image reading area;

a moving means for modifying the image data such that a position of the image data is moved to be located at a predetermined position when the offset of the document is detected by said detector; and

a means for forming an image on a paper based on the modified image data.

2. The image processing apparatus according to claim 1, wherein the document to be detected is rectangular.

3. The image processing apparatus according to claim 1, wherein said moving means comprises a rotator to rotate the image data.

4. The image processing apparatus according to claim 3, wherein said detector detects sides of the document in the image reading area, estimates sides of the document extending beyond the image reading area, determines a paper size for image forming from the detected and estimated sides and sets parameters for image forming based on a tilt angle of the document, the paper size and the offset of the document.

5. The image processing apparatus according to claim 4, wherein said detector determines the sides of the document based on coordinates of the document area and estimates the tilt angle based on the determined sides.

6. The image processing apparatus according to claim 3, wherein said detector detects sides of the document and wherein said image processing apparatus further comprises a means for inhibiting said rotator from rotating the image data when said detector cannot detect the sides of the document.

7. The image processing apparatus according to claim 3, wherein said detector detects sides of the document and determines at least one tilt angle and wherein said image processing apparatus further comprises a means for inhibiting said rotator from rotating the image data when said at least one tilt angle is substantially different from other tilt angles obtained from the sides of the document.

8. The image processing apparatus according to claim 3, wherein said detector detects a document area and sides of the document and said detector further calculates a paper size from a rectangular size which corresponds to the detected document area and the detected sides.

9. The image processing apparatus according to claim 8, further comprising a means for inhibiting said rotator from rotating the image data when the calculated paper size is larger than a maximum paper size.

10. The image processing apparatus according to claim 8, further comprising a 90°

rotation means for rotating the image by 90°

, wherein said 90°

rotation means and said rotator are activated while changing the direction of the paper when the calculated paper size exceeds a dimension of a current paper size but is smaller than the maximum paper size which can be prepared by the printer.

11. The image processing apparatus according to claim 1, wherein said detector detects sides of the document and determines a tilt of the document on said document setter based on a longest side in the detected sides of the document.

12. The image processing apparatus according to claim 1, wherein said detector detects a document area and sides of the document, said detector further calculates a paper size which corresponds to the detected document area and the detected sides, and wherein said detector calculates a parallel translation of the image data from the calculated paper size when two adjacent sides of the document exist in the detected sides.

13. A method for detecting a document comprising the steps of:

reading a document put on a document setter, having an image reading area on which a document to be read is put;

extracting edges of the document based on image data obtained by reading the document put on the image reading area;

obtaining lines of the document from the extracted edges;

determining edges along a longest line among the obtained lines of the document obtained from the extracted edges; and

determining a slope of the document put on the document setter based on the edges along the longest line.

14. The method according to claim 13, further comprising the step of determining a document area in the image reading area based on the obtained lines and slope.

15. The method according to claim 13, further comprising the step of grouping the obtained lines according to the slope, wherein the slope of the document is determined by calculating a sum of slopes of the obtained lines in each group and the slope of the document is set as the slope of the group having the largest sum.

16. The method according to claim 15, wherein in said grouping step, a group consists of lines having a first slope and lines having a second slope which is perpendicular to the first slope.

17. An image forming apparatus comprising:

a document setter, having an image reading area on which a document is put;

an image reader which reads the document put on said document setter;

a detector which detects a document area of the document in the image reading area based on image data of the document read by said image reader;

a means for determining a rectangular area which includes the detected document area, said means for determining a rectangular area being adapted for determining a rectangular area even in the case when the document extends beyond the image reading area;

a means for determining a slope of the rectangular area;

a rotator which rotates the image data included in the rectangular area to correct a tilt of the document; and

a printer which forms an image on a paper based on the image data rotated by said rotator.

18. The image forming apparatus according to claim 17, wherein said detector which detects a document area of the document comprises:

an edge detecting means for detecting edges of the document; and

an extraction means for extracting edge change points as points at which a slope of a line changes between connecting adjacent edges; and

a determining means for determining the document area based on the edge change points.

19. The image forming apparatus according to claim 18, wherein said detector which detects a document area of the document further comprises a means for detecting a slope of the document based on lines connecting the extracted edge change points, and said determining means determines the document area as a rectangular area having the slope of the document and including all the edge change points.

20. A method for detecting a document comprising the steps of:

reading a document put on a document setter, having an image reading area for reading a document which is put in the image reading area, by moving a scanner in the subscan direction for reading an image with a line sensor aligned in the main scan direction;

extracting edges of the document based on image data read from the document;

determining, from the extracted edges, edges of lines having slopes equal to or smaller than a predetermined angle relative to the subscan direction in the extracted edges; and

determining a tilt of the document put on the document setter based on the determined edges of lines;

wherein in the step of determining the tilt of the document, the slope of a longest line in the lines having slopes equal to or smaller than the predetermined angle relative to the subscan direction is determined as the tilt of the document.

21. The method according to claim 20, wherein in the step of determining the tilt of the document, the slope of a longest line in the lines having slopes equal to or smaller than the predetermined angle relative to the subscan direction and having a line perpendicular thereto is determined as the tilt of the document.