RESTORATION OF DEGRADED PHOTOGRAPHIC IMAGES

• US 3,627,920 A
• Filed: 04/03/1969
• Issued: 12/14/1971
• Est. Priority Date: 04/03/1969
• Status: Expired due to Term

• Current Assignee: Manfred R. Schroeder, Man M. Sondhi
• Original Assignee: Manfred R. Schroeder, Man M. Sondhi
• Inventors: Schroeder, Manfred R., Sondhi, Man M.
• Primary Examiner(s): Griffin, Robert L.
• Assistant Examiner(s): Eckert, Jr., Richard K.
• Application Number:
  US04/813,236
• Time in Patent Office: 985 Days
• Field of Search: 178/6.8,7.1AC 179/1SA 355/20,52,68,80,81,84,71 340/146.1,146.3 333/7T 324/78E,77B,77C,77D,77F
• US Class Current: 382/112
• CPC Class Codes: H04N 5/253 Picture signal generating by scanning motion picture films or slide opaques, e.g. for telecine scanning details therefor H04N3/36 ; standard conversion therefor H04N7/0112

Abstract

Photographs which are blurred, for example, by uniform motion of a camera relative to an image during exposure, are restored by identifying certain parameters of the blurring, e.g., direction and displacement, using the parameters to transform the distortion into an additive periodic component in the picture (blur), and by estimating (or identifying) and subtracting the periodic components from the picture. Two-dimensional spectral analysis, or the cepstrum technique, may be employed to identify the blur parameters, and a transversal filter arrangement, adjusted in accordance with parameter values is used to perform the estimation and subtraction.

Claims

1. The method of restoring photographs blurred because of linear motion of a camera relative to an image during exposure, which comprises the steps of:

analyzing a photograph to develop a video signal countErpart thereto, developing a parameter signal to identify the extent of blurring in said photograph, transforming said parameter signal into additive periodic signal components which correspond to blur components in said video signal, identifying the magnitude and period of said periodic signal components, and subtracting said periodic signal components from said video signal, an electrical signal representation of the information in said photograph, means for analyzing said representation in each of two orthogonal directions to produce signals which denote cepstral peaks in said representation, means for selecting the direction which exhibits a series of large cepstral peaks as an indication of the direction of blurring in said photograph, and means for measuring the interval between cepstral peaks in said signal representation to produce an indication of the extent of blurring in said photograph.

2. The method of restoring photographs as defined in claim 1, wherein the analysis of said photograph to develop a video signal takes place by repetitive scanning of said photograph in the direction of blurring.

3. The method of restoring photographs as defined in claim 2 wherein said signal representative of said parameter of blurring is developed by, performing a spectrum analysis on said video signal, and by measuring the interval between highest amplitude spectral signals.

4. The method of restoring photographs as defined in claim 2 wherein said signal representative of blurring is developed by, performing a cepstrum analysis of said signal representative of said photograph, and employing a measure of the interval between major cepstral peaks to identify the extent of blurring.

5. The method of restoring photographs as defined in claim 2 wherein, said parameter signal is transformed into additive periodic components by passing said video signal through a transversal filter arrangement adjusted in accordance with said parameter signal value.

6. The method of identifying the direction and extent of blurring in a photograph blurred because of relative motion between the camera and scene being photographed, which includes the steps of:

scanning a photograph to produce a video signal counterpart thereof, performing a two-dimensional cepstrum analysis of said video signal, identifying the direction of blurring in said photograph from the direction in said two-dimensional cepstrum which exhibits a plurality of cepstral peaks, and employing a measure of the interval between major cepstral peaks to identify the extent of blurring

7. The method of restoring photographs blurred because of uniform linear motion of a camera relative to an image during exposure, which comprises the steps of:

scanning a photograph linearly to produce an electrical signal representation of said photograph, performing a two-dimensional cepstrum analysis on said signal representation, identifying the direction of blurring in said photograph as the direction in said cepstrum analysis in which a plurality of large cepstral peaks are evident, identifying the extent of blurring in said photograph from a measure of the interval between major cepstral peaks in said analysis developing parameter signals to identify the identified direction and extent of blurring in said photograph, transforming said parameter signals into additive periodic components which correspond to blur components in said signal representation of said photograph, subtracting said additive periodic components from said electrical signal representation of said photograph in the direction of the blurring, and developing a visual image from the resulting difference signal.

8. Apparatus for determining the direction and extent of blurring in a photograph blurred because of motion of a camera relative to an image during exposure, which comprises;

means for scanning a photograph to produce an electricAl signal representation of the information in said photograph, means for analyzing said representation in each of two orthogonal directions to produce signals which denote cepstral peaks in said representation, means for selecting the direction which exhibits a series of large cepstral peaks as an indication of the direction of blurring in said photograph, and means for measuring the interval between cepstral peaks in said signal representation to produce an indication of the extent of blurring in said photograph.

9. A system for restoring photographs blurred because of motion of a camera relative to an image during exposure, which comprises:

means for scanning a photograph in the direction of blurring in said photograph to produce an electrical signal representation of said photograph, a transversal filter including a tandem connection of individually adjustable delay elements, means for adjusting the delay exhibited by each of said individual delay elements to an interval proportional to the extent of blurring in said photograph, means for directing said electrical signal representation through said adjusted filter to produce a signal replica of periodic blur components in said photograph, means for synchronously subtracting said replica signal from said electrical signal representation to produce a difference signal, and means responsive to said difference signal for reconstituting said photograph.

10. A system as defined in claim 9, wherein, said means for adjusting the relative delay exhibited by said delay elements includes means for altering the rate of scanning said photograph.

11. The method of restoring pictures blurred because of uniform linear motion of a camera relative to an image during exposure which comprises the steps of:

representing each of a plurality of scans in the direction of blur in a blurred picture by intensity values b(x);

evaluating a blur component Q for each of said scans in accordance with the relation where p represents an average value of a representation of the original unblurred image scene p(x) of said picture, a represents the number of intensity values in a blur interval, K represents the number of blur intervals in one scan in the direction of blur in said picture, and in which f(x) where N is the integer part of x/a,b'"'"''"'"'represents the derivative of b(x), and n represents a selected integer;

evaluating the value of said original unblurred image scene p(x) in accordance with the relation p(x) f(x) +Q (x(mod a)), where x (mod a) is the remainder upon dividing x by a; and

developing a pictorial display in accordance with the intensity values represented by said values p(x).