Image interpolation system

• US 4,303,947 A
• Filed: 04/28/1980
• Issued: 12/01/1981
• Est. Priority Date: 06/21/1978
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Stoffel, James C.
• Primary Examiner(s): Bookbinder, Marc E.
• Assistant Examiner(s): Coles, Edward L.
• Application Number:
  US06/144,710
• Time in Patent Office: 582 Days
• Field of Search: 358/133, 358/135, 358/136, 358/166, 358/260, 358/261, 358/289, 358/287, 358/77, 358/138, 358/140, 364/515, 364/577
• US Class Current: 358/426.03
• 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 1/403 Discrimination between the two tones in the picture signal of a two-tone original
• CPC Class Codes: H04N 1/411 for the transmission or storage or reproduction of two-tone pictures, e.g. black and white pictures

Abstract

Analog image data pixels are sampled and held to produce a box car wave representative of the image data. Wave height differences are bridged by linear interpolation, with frequency enhancement imposed at the bridge junctures. The modified image wave is thresholded and sampled at a multiple of the original frequency to provide an image pixel stream comprised of both original image pixels having one or more interpolated image pixels therebetween. One or more intermediate image lines are interpolated by comparing binary image data, portions of which may be interpolated, on a pixel by pixel or multiple pixel basis one line pair at a time. The pixel comparison produces an address used to identify a specific image pixel pattern from multiple image pixel patterns stored in memory. The image pixel pattern taken from memory is used to form the interpolated intermediate line or lines.

Claims

1. The method of handling data representative of an image in pixel form to provide an output image having increased resolution while reducing image date storage requirements and transmission bandwidth, the steps comprising:

(a) providing a minimal number of original image pixels representative of an image on a line by line basis;

(b) interpolating extra image pixels from said original image pixels; and

(c) interpolating at least one additional line of image pixels from both said original image pixels and said extra image pixels to provide said output image with increased resolution.

2. The method of handling data representative of an image in pixel form to provide an output image having increased resolution while reducing image data storage requirements and transmission bandwidth, the steps comprising:

(a) providing a minimal number of original image pixels representative of an image on a line by line basis;

(b) interpolating extra image pixels from said original image pixels;

(c) transmitting the original image pixels together with extra image pixels interpolated therefrom to a remote output, and

(d) interpolating at least one additional line of image pixels for each line of image pixels from the image pixels comprising said line at said remote output.

3. An imaging method, the steps comprising:

(a) line scanning an original at an input station to provide an analog signal in serial pixel form representative of each line of said original scanned;

(b) interpolating additional image pixels for each line of said original scanned from the scanned image pixels at said input station; and

(c) interpolating at least one additional line of pixels between each scanned line pair of said original from corresponding pixels of said scanned line pairs at an output station.

4. The method according to claim 3 including the step of converting said analog signal to a binary signal before interpolating said one additional line.

5. The method of interpolating from analog image data additional image data to provide enhanced image output resolution, said analog image data being in the form of a serial pixel stream, the steps comprising:

(a) sampling the voltage level of said image pixels in succession;

(b) forming a box car signal wave representative of said analog image data by holding the voltage level sampled for a preset interval;

(c) interpolating linearly between different voltage levels along said signal wave over said preset interval;

(d) frequency enhancing said signal wave;

(e) thresholding said signal wave to convert the analog signal wave to a binary signal wave; and

(f) sampling said binary signal wave at a frequency greater than the input frequency of said input pixel stream to provide an output pixel stream having a greater number of pixels than the input pixel stream.

6. The method according to claim 5 including the step of sampling said binary signal at a frequency twice that of said input frequency.

7. The method according to claim 5 including the step of sampling said binary signal at a frequency at least three times that of said input frequency.

8. The method according to claim 5 including the step of sampling said binary signal at a frequency at least four times that of said input frequency.

9. The method according to claim 5 including the step of sampling said binary signal at a frequency at least five times that of said input frequency.

10. The method according to claim 5 including the step of interpolating at least one additional output pixel stream from said output pixel stream.

11. The method according to claim 5 in which said output pixel stream is segregated into lines, the steps of comparing the output pixel stream of one line with the output pixel stream of an adjoining line, and

interpolating a pixel stream for at least one intermediate line from said output pixel streams.

12. The method of processing a stream of image pixels to increase the number of image pixels in said stream and enhance resolution of the image represented by said pixels, the steps comprising:

(a) sampling and temporarily holding the voltage level of said image pixels in succession whereby to form a signal wave representative of said pixel stream;

(b) interpolating linearly between different voltage levels along said signal wave over said preset interval;

(c) thresholding said signal wave; and

(d) sampling the thresholded signal wave at a frequency greater than the input frequency of said pixel stream to provide an output pixel stream having increased numbers of pixels.

13. The method according to claim 12 including the step of frequency enhancing said signal wave after interpolating said signal wave linearly.

14. The method according to claim 12 including the step of interpolating at least one additional pixel stream from said output pixel stream.

15. In an apparatus for processing a stream of image pixels to provide increased image resolution, comprising in combination:

holding means for temporarily holding the voltage level of said image pixels in succession;

interpolator means for interpolating the output of said holding means, said interpolator means interpolating linearly between successive pixels output by said holding means;

thresholding means for thresholding the output of said interpolator means;

sampling means for sampling the output of said thresholding means to provide a succession of discrete image pixels therefrom; and

clock means for driving said sampling means at a frequency greater than the frequency at which said image pixels are input whereby to provide a stream of image pixels having an increased number of image pixels.

16. The apparatus according to claim 15 including means to frequency enhance said interpolator means output.

17. The apparatus according to claim 15 including second interpolator means for interpolating at least one additional stream of image pixels from said first mentioned stream of image pixels following processing thereof.