Image reader

• US 5,995,245 A
• Filed: 10/22/1997
• Issued: 11/30/1999
• Est. Priority Date: 10/25/1996
• Status: Expired due to Term

• Current Assignee: Minolta Co., Ltd. (Konica Minolta Inc.)
• Original Assignee: Minolta Co., Ltd. (Konica Minolta Inc.)
• Inventors: Moro, Fuminori
• Primary Examiner(s): Coles, Edward L.
• Assistant Examiner(s): Lee, Cheukfan
• Application Number:
  US08/956,298
• Time in Patent Office: 769 Days
• Field of Search: 358/497, 358/493, 358/474, 358/488, 358/486, 358/471, 358/464, 358/463, 250/208.1, 250/234-236
• US Class Current: 358/474
• CPC Class Codes: H04N 1/02409 Focusing, i.e. adjusting the focus of the scanning head
• CPC Class Codes: H04N 1/047 Detection, control or error compensation of scanning velocity or position H04N1/0402 and H04N1/17 take precedence
• 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 2201/0416 Performing a pre-scan
• CPC Class Codes: H04N 2201/0434 specially adapted for scanning pages of a book
• CPC Class Codes: H04N 2201/04787 by changing or controlling the addresses or values of pixels, e.g. in an array, in a memory, by interpolation

Abstract

The present invention pertains to a book scanner that reads the image of an document such as a book or magazine while it is placed open and face up, and more particularly, to an image reader that detects the height distribution of the document prior to performing a pre-scanning to detect the size of the document and the background luminance of the document. Thus, a focal length adjustment is performed in response to the detected height distribution while the pre-scanning takes place in order to prevent defocusing caused by the curvature of the document consisting of an open book or magazine. The book reader also reads the book in at least two spectral regions to detect and eliminate image anomalies.

Claims

1. An image reader for reading a document placed on a document table, said image reader comprising:

an image reading device for reading a document and for outputting image data;

a scanning control means for executing a first pre-scanning, a second pre-scanning and a main scanning;

a first condition detecting means for detecting a first condition of the document based on image data of the document obtained by the image reading device during the first pre-scanning;

a first image reading correcting means for correcting a reading of a document based said detected first condition;

a second condition detecting means, responsive to the first image reading correcting means, for detecting a second condition of the document based on image data of the document obtained by the image reading device during the second pre-scanning, said image data of the document obtained by the image reading device during the second pre-scanning being corrected by said first image reading correcting means based on said detected first condition; and

a second image reading correcting means for correcting a reading of a document based on said detected second condition;

wherein image data of the document obtained by the image reading device during the main scanning is corrected by said second image reading correcting means based on said detected second condition, said first condition being different than said second condition.

2. An image reader in accordance with claim 1, wherein said first condition detected during the first pre-scanning is a document height distribution.

3. An image reader in accordance with claim 2, wherein a scanning speed for at least one of the first and second pre-scannings is higher than a scanning speed for the main scanning.

4. An image reader for reading a document placed on a document table in a face upward condition, said image reader comprising:

an image reading device for reading a document and for outputting image data;

an optical device for projecting an image of the document onto the image reading device;

a height detecting device for detecting a height distribution of a surface of the document before pre-scanning;

a focus adjusting device for adjusting a focus of the image projected onto the image reading device by said optical device based on the detected height distribution; and

a document condition detecting device for detecting a condition of the document based on image data from the image reading device read during pre-scanning, said image data read during pre-scanning being read while said focus adjusting device adjusts a focus of the image projected onto the image reading device based of the detected height distribution.

5. An image reader in accordance with claim 4, further comprising:

a reading operating device for executing a reading operation based on the detected condition of the document and the detected height distribution of the surface of the document.

6. An image reader in accordance with claim 5, wherein said detected condition is a size of the document.

7. An image reader in accordance with claim 4, wherein said detected condition is a luminance of background of the document surface.

8. An image reader for reading a document placed on a document table in a face upward condition, said image reader comprising:

a line sensor which scans a two-dimensional image to generate electronic image data;

an optical device for projecting the image of the document surface and the image of an edge surface of document onto said line sensor;

a scanning control device for executing a first pre-scanning, a second pre-scanning, and a main scanning;

a height detecting device for detecting a height distribution of the surface of the document based on the image of said edge surface that is obtained by said line sensor during the first pre-scanning;

a focus adjusting device for adjusting a focus of the image projected onto the line sensor by said optical device based on the detected height distribution;

a document condition detecting device for detecting a condition of the document, other than said height distribution, based on image data output by the line sensor during the second pre-scanning;

a reading control device for controlling reading by the line sensor during the main scanning;

wherein, during the first pre-scanning, the image of the edge surface is read and the height distribution of the surface of the document is detected by means of reading the edge surface under a condition of a fixed focal length,

wherein, during the second pre-scanning, the image of the document surface is read and the condition of the document is detected while the focus is adjusted in response to the height distribution detected during the first pre-scanning, and

wherein, during the main scanning, the image of the document surface is read based on the condition detected during the second pre-scanning.

9. An image reader in accordance with claim 8, wherein said document condition is a size of the document.

10. An image reader in accordance with claim 8, wherein said document condition is a luminance of background of the document surface.

11. An image reader in accordance with claim 8, further comprising a filter mechanism for selectively positioning first and second optical filters in an optical path between said optical device and said line sensor.

12. An image reader in accordance with claim 11, wherein said filter mechanism selectively positions said first optical filter in said optical path during the first pre-scanning and wherein said filter mechanism selectively positions said second optical filter in said optical path during the second pre-scanning.

13. An image reader in accordance with claim 12, wherein said first optical filter is a visible light-shielding filter and said second optical filter is an infrared light-shielding filter.

14. An image reader for reading a document placed on a document table in a face upward condition, said image reader comprising:

an image reading device for reading the document and for outputting image data;

an optical device for projecting an image of the document surface onto said image reading device;

an optical control device for selectably controlling a wavelength distribution of the image projected onto said image reading device;

a scanning control device for executing a first pre-scanning, a second pre-scanning, and a main scanning; and

a height detecting device for detecting a height distribution of the surface of the document based on the image that is obtained by said line sensor during the first pre-scanning;

wherein, during the first pre-scanning, the optical control device controls a wavelength distribution of the image projected onto the image reading device to an infrared wavelength distribution.

15. An image reader in accordance with claim 14, further comprising:

a document condition detecting device for detecting a condition of the document based on the image data output by the image reading device during the second pre-scanning.

16. An image reader in accordance with claim 15, wherein said document condition is a size of the document.

17. An image reader in accordance with claim 15, wherein said document condition is a luminance of background of the document surface.

18. An image reader in accordance with claim 15, further comprising:

a focus adjusting device for adjusting a focus of the image projected onto the line sensor by the optical device based on the detected height distribution;

wherein, during the first pre-scanning, the image of the document is read and the height distribution of the surface of the document is detected under a condition of a fixed focal length;

wherein, during the second pre-scanning, the image of the document surface is read and the condition of the document is detected while the focus is adjusted in response to the height distribution detected during the first pre-scanning; and

wherein, during the second pre-scanning, the optical control device controls a wavelength distribution of the image projected onto the image reading device to a visible wavelength distribution.

19. A three mode image reader for reading a document placed on a document table in a face upward condition, comprising:

a line sensor which scans a two-dimensional image to generate electronic image data;

an optical device for projecting the image of the document surface and the image of an edge surface of document onto said line sensor;

a mode selection device for selecting one of first, second or third modes;

a scanning control device, responsive to said mode selection device, for executing at least one of a first pre-scanning, a second pre-scanning, and a main scanning;

a height detecting device for detecting a height distribution of the surface of the document based on the image of said edge surface that is obtained by said line sensor during the first pre-scanning;

a focus adjusting device for adjusting a focus of the image projected onto the line sensor by said optical device based on the detected height distribution;

a document condition detecting device for detecting a condition of the document based on image data output by the line sensor during the second pre-scanning; and

a reading control device for controlling reading by the line sensor during the main scanning;

wherein in the first mode only the main scanning is executed, in the second mode the first pre-scanning and the main scanning are executed, and in the third mode the first pre-scanning, the second pre-scanning and the main scanning are executed;

wherein, during the first pre-scanning, the image of the edge surface is read and the height distribution of the surface of the document is detected by means of reading the edge surface under a condition of a fixed focal length,

wherein, during the second pre-scanning, the image of the document surface is read and the condition of the document is detected while the focus is adjusted in response to the height distribution detected during the first pre-scanning, and

wherein, for the second and third modes, during the main scanning, the image of the document surface is read based on at least one of the height distribution detected during the first pre-scanning and the condition detected during the second pre-scanning.

20. An image reader in accordance with claim 19, further comprising a filter mechanism for selectively positioning first and second optical filters in an optical path between said optical device and said line sensor.

21. An image reader in accordance with claim 20, wherein said filter mechanism selectively positions said first optical filter in said optical path during the first pre-scanning, said filter mechanism selectively positions said second optical filter in said optical path during the second pre-scanning, and wherein said first optical filter is a visible light-shielding filter and said second optical filter is an infrared light-shielding filter.

22. A method of processing an image of a document placed on a document table in a face upward condition, the method comprising the steps of:

projecting an image of the document onto a image reading device;

detecting a height distribution of a surface of the document before pre-scanning;

adjusting a focus of the image projected onto the image reading device based on the detected height distribution;

detecting a condition of the document based on image data from the image reading device read during pre-scanning, said image data read during pre-scanning being read while said step of adjusting a focus based on the detected height distribution; and

reading the document with the image reading device and outputting image data based on the detected height distribution and the detected condition of the document.

23. A method of processing an image of a document placed on a document table in a face upward condition, the method comprising the steps of:

reading a document and outputting image data by a line sensor;

projecting the image of the document surface and the image of an edge surface of document onto said line sensor;

executing a first pre-scanning wherein the image of the edge surface is read and the height distribution of the surface of the document is detected while the focal length is fixed;

executing a second pre-scanning wherein the image of the document surface is read and a condition of the document, other than the height distribution, is detected while the focus is adjusted in response to the height distribution detected during the first pre-scanning; and

executing a main scanning wherein the image of the document surface is read based on the condition detected during the second pre-scanning.