Image analysis – Image enhancement or restoration – Artifact removal or suppression
Reexamination Certificate
1997-12-29
2002-08-27
Lee, Thomas D. (Department: 2624)
Image analysis
Image enhancement or restoration
Artifact removal or suppression
C382S254000, C358S463000, C358S487000, C356S237100, C356S239100, C250S330000, C250S341800, C250S339110
Reexamination Certificate
active
06442301
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to electronic image enhancement and recovery, and more particularly to a method and apparatus which compensate for the effects of defects of the media on which the image is stored.
BACKGROUND OF THE INVENTION
Ever since the first image of an object was captured on film, a serious problem became apparent: imperfections in and on the recording medium itself which distort and obscure the original image that was sought to be captured. This non-image imperfection problem continues to plague the field of image capture and reproduction to the present day. These imperfections occur in many forms including dust, scratches, fingerprints, smudges, and the like.
The film industry has been concerned that the problem caused by these non-image imperfections may jeopardize the long term future of analog images. Notwithstanding the significant efforts that have been made to solve the problem, it nevertheless persists. This is particularly true with respect to enlargements and high resolution scans. Thus, the problem is becoming even more acute and recognized as resolutions increase. Furthermore, multimedia applications have brought widespread attention to the problem with the increase in film scanning for computer applications.
The non-image imperfection problems occur more frequently with negatives than with transparencies because (1) viewing the negative requires a light to dark ratio gain (also known as a “gamma”) of about two to one; whereas viewing a transparency is less demanding and (2) filmstrips are subject to more contact than are mounted transparencies. Some imperfections may be present in fresh photographic film, for example, media surface waves or microbubbles in the emulsion. Improper processing may also introduce non-image imperfection problems, for example mild reticulation or residual unbleached silver. Some non-image imperfection problems are introduced through improper handling of the image media which may leave oily fingerprints and other surface contaminants or cause physical damage such as scratches which distort the view of the image. Improper storage may also leave the film further exposed to defect inducing environmental influences such as dust and chemicals. Archival polypropylene sleeves employed to protect negatives contribute to the problem by leaving hairline surface scratches as the negatives are pulled out and replaced into the sleeves. As illustrated by the above examples, non-image imperfections may arise out of one or more of the following: film emulsion defects; improper processing; and improper handling or storage which may cause extraneous matter accumulation or scratches on the image media.
Numerous measures have been developed in the art in an attempt to address these problems, particularly with respect to captured high resolution images. Generally speaking, these measures are in the nature of prevention and labor intensive minimization of non-image defects. One approach has been that of preventing introduction of non-image defects in the development process itself. Expensive anti-static equipment, including spray machines to neutralize dust attracting charges, are employed by some photo finishers. Photo finishers also attempted to solve some of the problems by employing diffuse light source enlargers that help reduce the effects of refraction of the light due to imperfections in the photo finishing processes.
Another approach used in the art involves minimizing the effects of these imperfections once they are present by various correction techniques, most of which are manual and thus highly labor-intensive and expensive. For example, during the photo finishing process, a highly trained individual might spend a great deal of time using various spotting dyes and an extremely small spotting brush in an effort to essentially paint out the imperfections in a reproduced or printed image. Another technique is to wipe on or immerse the negatives in a light oil in an attempt to optically fill scratches.
As the art has developed, various attempts have been made to automate the correction process, particularly with respect to digital image systems. In such systems, once an imperfection has been detected, various “fill” algorithms are used to correct the image at the imperfection site. Nevertheless, heuristics or human intervention has been required to detect the imperfections with a subjective threshold. Typically the area identified to be corrected in this manner is much larger than necessary, in part due to application of these subjective criteria for detecting defective areas.
Automated methods have also been developed for detecting imperfect areas in recording media, as described in German patent 2821868.0 published Nov. 22, 1979, and entitled “Method and Device for Detecting Recording and Counting of Mechanical Damage to Moving Bands, for Example Films.” The approach discussed focuses on determining the quantity of defects and shutting down processing if that measured quantity exceeds some predetermined maximum level of defects. In this system a source of infrared energy impinges upon the film medium. A scanned infrared image of the film in question is then taken by sensors detecting reflection of the infrared energy from the film surface. However, several limitations are present in the system disclosed by the patent.
First, its purpose is not to correct the effects of such detected film defects present on the film image. Instead, the system is implemented simply to monitor the prevalence of these defects in an automated photographic development process whereby the process can be automatically shut down if the defect rate exceeds a prescribed level. The optical infrared path is a reflective one from the infrared source to the infrared sensor which is typically different from the other sensors utilized for image processing. The infrared image is not recorded in registry with any other scanned images from the visual portion of the electromagnetic spectrum. Registry refers to the precise alignment of two related images, plates, or impressions so that they are held in position relative to each other. The fact that this prior art system does not record the infrared image in registry with any other images taken of the film is a disadvantage which in and of itself renders it extremely difficult to subtract out the effect of such imperfections noted in the infrared image from similar defects present in the visual record of the image.
In another prior system disclosed by the present inventor, a method which compensates for the effects of storage media defects on image data is disclosed by deriving from the medium separate images in the red, green, blue and infrared portions of the electromagnetic spectrum, each corresponding to the image stored therein As disclosed in U.S. Pat. No. 5,266,805 issued to the present inventor on Nov. 30, 1993, red, green, blue and infrared light is sequentially directed at one side of the film by means of a light source and color filter wheel. Corresponding red, green, blue, and infrared images formed by that portion of the light being transmitted through the film are digitally captured from the opposite side of the film. The images are preferably captured in registry to facilitate subtracting out the effect of imperfections at locations in the infrared record from corresponding locations in the red, green, and blue images. The imperfections may either substantially reduce or totally occlude the infrared light. However, remaining portions of the medium having the desired image without such imperfections are essentially uniformly transmissive to infrared light. These imperfection-free portions have variable transmissivity in the visual spectrum which is determined by the image developed on the film. Accordingly, the infrared image may serve as an indicator or map of the spatial position of these non-image imperfections on and in the medium, thereby allowing determination of the location and removal of the defects so that the underlying desired image may be recovered.
In order to remove film de
Applied Science Fiction Inc.
Baker & Botts L.L.P.
Lee Thomas D.
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