Apparatus and method of increasing scanner resolution

• US 6,459,823 B2
• Filed: 10/28/1998
• Issued: 10/01/2002
• Est. Priority Date: 10/28/1998
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Altunbasak, Yucel, Taubman, David S.
• Primary Examiner(s): Boudreau, Leo
• Assistant Examiner(s): PATEL, KANJIBHAI B
• Application Number:
  US09/181,346
• Publication Number:
  US 20010046331A1
• Time in Patent Office: 1,434 Days
• Field of Search: 250/234, 250/235, 250/208.1, 250/208.3, 382/254, 382/260, 382/266, 382/279, 382/284, 382/299, 382/312, 382/317, 382/321, 348/154, 358/474, 358/475, 358/481, 358/497, 355/53
• US Class Current: 382/299
• CPC Class Codes: H04N 1/3935 with modification of image resolution, i.e. determining the values of picture elements at new relative positions

Abstract

Hardware resolution of a scanner is increased without improving the quality of the scanner'"'"'s sensor array or imaging optics. A first low-resolution representation of an image is generated during a first scan and a second low-resolution representation of the image is generated during a second scan. The scanner is configured to intentionally induce a motion error in either the first or second representation. A composite representation of the first and second representations is generated from the first and second representations, and a super resolution technique is used to generate a third representation of the image from the composite representation. The third representation has a higher resolution than the first and second representations.

Claims

1. A method of scanning an image, the method comprising:

performing a first scan of the image to produce a first representation of the image;

performing a second scan of the image to produce a second representation of the image, a motion error having been intentionally induced between the first and second representations so that different portions of the image are detected;

using a super resolution technique to generate a third representation of the image from the composite representation, the third representation having a higher resolution than the first and second representations.

2. The method of claim 1, wherein a scanner is used to perform the first and second scans, the scanner having a known optical transfer function, and wherein the optical transfer function and the amount of the motion error are used to generate the third representation from the composite representation.

3. The method of claim 2, wherein the optical transfer function is an estimate of a Point Spread Function of the scanner, the estimate being based on Line Spread Functions of the scanner.

4. The method of claim 1, further comprising configuring the scanner to shift the second scans to cause the motion error, the scanner being configured between the first and second scans.

5. The method of claim 4, wherein the scanner includes a sensor array and a light source, and wherein the scanner is configured by changing an optical path between the light source and the sensor array.

6. The method of claim 4, wherein the scanner is configured by starting the second scan at a different initial position than the first scan.

7. The method of claim 1, wherein the motion error is a subpixel displacement.

8. The method of claim 7, wherein the motion error is between fractional values of 0.35 and 0.65 pixels.

9. The method of claim 1, further comprising taking at least one additional scan of the image to produce at least one additional representation of the image, a motion error having been intentionally induced in each additional scan, each additional representation being used to generate the third representation of the image.

10. The method of claim 1, wherein the super resolution algorithm includes one-pass linear filtering of the first and second representations.

11. The method of claim 10, wherein the composite representation is produced by interleaving the first and second representations;

and wherein the third representation is produced by convolving the composite representation with an N×

M filter.

12. A scanning system comprising:

a sensor array movable along a scanning plane;

means for selectively inducing a motion error in a representation produced by the sensor array; and

a processor for generating a composite representation from a first representation and a second representation, the means having created a motion error between the first and second representation so that the first representation is different than the second representation, the processor using a super-resolution algorithm to generate a high resolution image from composite representation.

13. The system of claim 12, wherein the scanning system has a known optical transfer function, wherein the optical transfer function is an estimate of a Point Spread Function of the scanner, the estimate being based on Line Spread Functions of the scanner, and wherein the amount of the motion error and the estimate of the Point Spread Function are used to generate the high resolution representation from the composite representation.

14. The system of claim 12, wherein the scanner includes a sensor array and a light source, and wherein the means includes at least one optical element moveable to change an optical path between the light source and the sensor array.

15. The system of claim 12, wherein the scanner further comprises a light source, a first optical light path being between the light source and the scanning plane, a second optical path being between the scanning plane and the sensor array, and wherein the means includes an optical element disposed along one of the first and second optical paths, the optical element being operable to cause a change of the second optical path relative to the sensor array and thereby induce a subpixel motion error in a representation generated by the scanner during a scanning operation.

16. The system of claim 12, wherein the processor generates the high resolution representation by interleaving the first and second representations into a composite representation;

and convolving the composite representation with an N×

M filter to produce the high resolution representation.

17. A scanner comprising:

a sensor array movable along a scanning plane;

a light source for generating a scanning beam during a scanning operation, the scanning beam following a first optical path between the light source and the scanning plane;

imaging optics disposed along a second optical path between the scanning plane and the sensor array; and

an optical element disposed along one of the first and second optical paths, the optical element being operable to cause a change of the second optical path relative to the sensor array and thereby induce a subpixel motion error in a representation generated by the scanner during a scanning operation.

18. The scanner of claim 17 wherein the optical element includes a beam-transmissive plate;

and wherein the scanner further includes an electromechanical actuator for moving the plate to change the second optical path.

19. The scanner of claim 17, further comprising a processor for generating a composite representation from the first and second representations and using a super-resolution algorithm to generate a high resolution representation from the composite representation.

20. The scanner of claim 19, wherein the processor generates the high-resolution representation by interleaving the first and second representations into a composite representation;

and convolving the composite representation with an N×

M filter to produce the high resolution representation.