Scan line queuing for high performance image correction

• US 5,608,538 A
• Filed: 08/24/1994
• Issued: 03/04/1997
• Est. Priority Date: 08/24/1994
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Edgar, Albert D., Penn, Steven C.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): JARDIEU, DEREK
• Application Number:
  US08/295,318
• Time in Patent Office: 923 Days
• Field of Search: 358/302, 358/406, 358/504, 358/448, 358/471, 358/474, 358/486, 358/488, 358/496
• US Class Current: 358/406
• 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 1/12 using the sheet-feed movement or the medium-advance or the drum-rotation movement as the slow scanning component, e.g. arrangements for the main-scanningsheet-feed movement by translatory movement of a flat picture-bearing surface H04N1/1008; main-scanning using oscillating or rotating mirrors H04N1/113; using multi-element arrays H04N1/19
• CPC Class Codes: H04N 1/193 using electrically scanned linear arrays , e.g. linear CCD arrays
• CPC Class Codes: H04N 1/40068 Modification of image resolution, i.e. determining the values of picture elements at new relative positions H04N1/3935 takes precedence
• CPC Class Codes: H04N 2201/02425 Self-adjusting arrangements, e.g. compensating for temperature fluctuations
• CPC Class Codes: H04N 2201/02439 Positioning method
• CPC Class Codes: H04N 2201/03162 Original guide plate
• CPC Class Codes: H04N 2201/0408 Scanning film strips or rolls
• CPC Class Codes: H04N 2201/04708 which remain outside the scanned image area
• CPC Class Codes: H04N 2201/0472 on or adjacent the sheet support
• CPC Class Codes: H04N 2201/04729 in the main-scan direction
• CPC Class Codes: H04N 2201/04731 in the sub-scan direction
• CPC Class Codes: H04N 2201/04732 Detecting at infrequent intervals, e.g. once or twice per line for main-scan control
• CPC Class Codes: H04N 2201/04734 Detecting at frequent intervals, e.g. once per line for sub-scan control
• CPC Class Codes: H04N 2201/04749 Detecting position relative to a gradient, e.g. using triangular-shaped masks, marks or gratings
• 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
• CPC Class Codes: H04N 2201/04789 in the main-scan direction
• CPC Class Codes: H04N 2201/04791 in the sub-scan direction
• CPC Class Codes: H04N 2201/04794 Varying the control or compensation during the scan, e.g. using continuous feedback or from line to line

Abstract

An image on a substrate is scanned by moving the substrate relative to a sensor array. As the raw scan lines are stored, a position reference for each raw scan line is established. First, the raw scan lines are prescaled between a raw resolution between raw scan lines as they are received from the sensor element to an intermediate resolution between scan lines. The position references for the raw scan lines are used during the prescaling step as well as the following scaling steps to accurately determine the position of the raw scan line within the image despite the distortions created by the inexpensive transport mechanism. Next, the prescaled scan lines are scaled "crosswise", that is between pixels in the scan line from a raw resolution sensed by the sensor elements in the sensor array to a chosen pixel resolution. Next, the prescaled scan lines which now have the chosen pixel resolution are scaled "lengthwise", that is in the direction of the scan, from the intermediate resolution to a chosen scan line resolution between the scan lines. The image is stored in an output buffer at the chosen pixel and scan line resolutions for transmission to an attached computer system for further image processing.

Claims

1. A scanner for copying a substrate image comprising:

a photosensor for converting the substrate image to a plurality of pixels positioned in an irregular grid pattern forming a raw image;

means for receiving a chosen grid pattern;

means for scaling the pixels in the raw image into a plurality of pixels positioned according to the chosen grid pattern to form a chosen image; and

means for outputting the chosen image.

2. The scanner as recited in claim 1 wherein the photosensor comprises a line array of individual sensors oriented in a first direction, and further comprises a transport mechanism which moves the substrate in a generally perpendicular direction to the first direction.

3. The scanner as recited in claim 2 wherein the pixels forming the raw image are arranged in a plurality of substantially parallel raw scan lines as sequentially sensed by the line array and the scaling means scales at least one raw scan line to form each corresponding scaled line of pixels according to the chosen grid pattern.

4. The scanner as recited in claim 2 wherein the scaling means for scaling the raw image to the chosen image further comprises:

means for prescaling the raw scan lines from the raw grid pattern to prescaled scan lines in an intermediate grid pattern; and

means for scaling the prescaled scan lines at the intermediate grid pattern to scan lines at the chosen grid pattern.

5. The scanner as recited in claim 4 further comprising means for establishing a position for each of the raw scan lines and wherein the positions are used by the scaling means for scaling the raw image to the chosen image.

6. The scanner as recited in claim 2 wherein the irregularity of the raw grid pattern is caused by variation in speed of the transport mechanism.

7. The scanner as recited in claim 2 wherein the irregularity of the raw grid pattern is caused by jitter in the transport mechanism.

8. A scanner for copying an image on a substrate comprising:

scanning means for converting the substrate image into a plurality of pixels positioned in an irregular grid pattern forming a raw image, the irregular grid pattern formed of a plurality of substantially parallel raw scan lines;

transport means for moving the substrate relative to the scanning means;

reference means for establishing a position for each of the raw scan lines;

means for scaling the raw image into a plurality of pixels positioned according to a chosen grid pattern to form a chosen image, the scaling means calling the reference means for the positions of the raw scan lines; and

means for outputting the chosen image.

9. The scanner as recited in claim 8 further comprising:

scan line scaling means for scaling spacing between scan lines from a raw spacing between raw scan lines to a chosen spacing between scaled scan lines, the scan line scaling means calling the reference means for the positions for the raw scan lines.

10. The scanner as recited in claim 9 wherein the scan line scaling means further comprises:

scan line prescaling means for scaling spacing between scan lines from a raw spacing between raw scan lines to an intermediate spacing between scan lines, a set of raw scan lines being scaled into a single prescaled scan line; and

scan line final scaling means for scaling spacing between scan lines from the intermediate spacing to the chosen spacing between scan lines.

11. The scanner as recited in claim 8 wherein the scaling means further comprises a pixel scaling means which scales scan lines from a raw spacing between pixels within a scan line to a chosen spacing between pixels in a scan line.

12. The scanner as recited in claim 8 wherein the reference means comprises a reference track disposed to a side of the substrate and means for interpreting a pattern sensed in the reference track as a position.

13. A method for copying a substrate image comprising:

converting the substrate image to a plurality of pixels positioned in an irregular grid pattern forming a raw image;

receiving a chosen grid pattern;

scaling the pixels in the raw image into a plurality of pixels positioned according to the chosen grid pattern to form a chosen image; and

outputting the chosen image.

14. The method as recited in claim 13 wherein a photosensor used for converting the substrate image comprises a line array of individual sensors oriented in a first direction, and the method further comprises the step of moving the substrate in a generally perpendicular direction to the first direction.

15. The method as recited in claim 14 wherein the pixels forming the raw image are arranged in a plurality of substantially parallel raw scan lines as sequentially sensed by the line array and the scaling step scales at least one raw scan line to form each corresponding scaled line of pixels according to the chosen grid pattern.

16. The method as recited in claim 13 wherein the scaling means for scaling the raw image to the chosen image further comprises the steps of:

prescaling the raw scan lines from the raw grid pattern to prescaled scan lines in an intermediate grid pattern; and

scaling the prescaled scan lines at the intermediate grid pattern to scan lines at the chosen grid pattern.

17. The method as recited in claim 16 further comprising the step of establishing a position for each of the raw scan lines and wherein the positions are used by the scaling step for scaling the raw image to the chosen image.

18. The method as recited in claim 13 wherein the irregularity of the raw grid pattern is caused by variation in speed during the step of moving the substrate.

19. The method as recited in claim 13 wherein the irregularity of the raw grid pattern is caused by jitter during the step of moving the substrate.

20. A method for copying an image on a substrate comprising the steps of:

converting the substrate image into a plurality of pixels positioned in an irregular grid pattern forming a raw image, the irregular grid pattern formed of a plurality of substantially parallel raw scan lines;

moving the substrate relative to the scanning means;

establishing a position for each of the raw scan lines;

scaling the raw image into a plurality of pixels positioned according to a chosen grid pattern to form a chosen image, the scaling means calling the reference means for the positions of the raw scan lines; and

outputting the chosen image.

21. The method as recited in claim 20 further comprising the steps of:

scaling spacing between scan lines from a raw spacing between raw scan lines to a chosen spacing between scaled scan lines; and

during the scaling spacing between scan lines step, calling for the positions for the raw scan lines.

22. The method as recited in claim 21 further comprising the steps of:

scaling spacing between scan lines from a raw spacing between raw scan lines to an intermediate spacing between scan lines, a set of raw scan lines being scaled into a single prescaled scan line; and

scaling spacing between scan lines from the intermediate spacing to the chosen spacing between lines.

23. The method as recited in claim 20 further comprising the step of scaling scan lines from a raw spacing between pixels within a scan line to a chosen spacing between pixels in a scan line.

24. The method as recited in claim 20 wherein the step for establishing a position for each of the raw scan lines uses a reference track disposed to a side of the substrate and interprets a pattern sensed in the reference track as a position.