Image reader which can shorten focal length in optical system having optical lens while keeping predetermined image reading width

• US 6,396,648 B1
• Filed: 03/17/2000
• Issued: 05/28/2002
• Est. Priority Date: 03/30/1999
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Yamamoto, Tetsuichiro, Kubo, Shinya
• Primary Examiner(s): Ben, Loha
• Application Number:
  US09/528,100
• Time in Patent Office: 802 Days
• Field of Search: 359/806,663,668,785,776,778,775,740,760,764 250/208.1,205,234,227.11 358/475,483,494 362/297,31
• US Class Current: 359/806
• CPC Class Codes: G02B 13/24 for reproducing or copying at short object distances
• CPC Class Codes: H04N 1/0281 with means for collecting light from a line or an area of the original and for guiding it to only one or a relatively low number of picture element detectors

Abstract

An image reader including a light source irradiating light to a reading object, a reading device reading an image on the reading object based on the radiated light; and a lens focusing the image onto the reading device and having a characteristic by which a distortion rate is increased from the central part to the end part. The distortion rate of the end part is set to a value in which there is no need to complement the read image.

Claims

1. An image reader comprising:

a light source irradiating light to a reading object;

a reading device reading an image on said reading object based on reflected light from said reading object; and

a lens focusing said image onto said reading device and having an optical characteristic in which a distortion rate is increased from a central part to an end part of said lens;

wherein said distortion rate of said end part is set to a value in which a correction of said read image is not needed.

2. An image reader as claimed in claim 1,

wherein said lens is provided by a wide-angle lens or a fish-eye lens.

3. An image reader as claimed in claim 1,

wherein said light source is arranged in a rear side of said reading object,

said reading device is arranged in a front side of said reading object, and

said lens is arranged between said reading object and said reading device such that said image of said reading object is focused on said reading device.

4. An image reader as claimed in claim 1,

wherein said light source and said reading device are arranged in a front side of said reading object and,

said lens is arranged between said reading object and said reading device such that said image of said reading object is focused on said reading device.

5. An image reader as claimed in claim 1,

wherein a resolution for said end part is set to 200 dpi and more, and

a resolution for said central part is set to 300 dpi and more.

6. An image reader as claimed in claim 1,

wherein the reading device comprises a line memory which stores an image data of the read image.

7. An image reader as claimed in claim 1,

wherein the reading device comprises a CCD which can generate a signal based on the read image.

8. An image reader as claimed in claim 1 comprises:

a mirror arranged on a light path between the reading object and the lens and reflecting the reflected light from the reading object to the lens.

9. An image reader as claimed in claim 1,

wherein focus length of the lens is set such that a distance between the reading object and the reading device is set from 30 mm to 250 mm.

10. An image reader as claimed in claim 1,

wherein resolution of the reading device is set to 200 dpi and more.

11. A method of image reading, comprising:

irradiating a light from a light source to a reading object;

focusing an image on said reading object to a reading device by a lens whose distortion rate increases from a central part of said lens to an end part thereof;

wherein said distortion rate of said end part is set to a value in which a correction of said image read on said reading object is not needed.

12. A method of image reading as claimed in claim 11,

wherein said lens is provided by a wide-angle lens or a fish-eye lens.

13. A method of image reading as claimed in claim 11,

wherein said light source is arranged in a rear side of said reading object,

said reading device is arranged in a front side of said reading object, and

said lens is arranged between said reading object and said reading device such that said image of said reading object is focused on said reading device.

14. A method of image reading as claimed in claim 11,

wherein said light source and said reading device are arranged in a front side of said reading object,

said lens is arranged between said reading object and said reading device such that said image of said reading device is focused on said reading device.

15. A method of image reading as claimed in claim 11,

wherein a resolution for said end part is set to 200 dpi and more, and

a resolution for said central part is set to 300 dpi and more.

16. A method of image reading as claimed in claim 11,

wherein the reading device comprises a line memory which stores an image data of the read image.

17. A method of image reading as claimed in claim 11,

wherein the reading device comprises a CCD which can generate a signal based on the read image.

18. A method of image reading as claimed in claim 11 comprises:

a mirror arranged on a light path between the reading object and the lens and reflecting the reflected light from the reading object to the lens.

19. A method of image reading as claimed in claim 11,

wherein focus length of the lens is set such that a distance between the reading object and the reading device is set to 30 mm to 250 mm.

20. A method of image reading as claimed in claim 11,

wherein resolution of the reading device is set to 200 dpi and more.