Image analysis – Image enhancement or restoration – Image filter
Reexamination Certificate
1999-04-29
2003-08-05
Lee, Thomas D. (Department: 2724)
Image analysis
Image enhancement or restoration
Image filter
C382S199000
Reexamination Certificate
active
06603885
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the field of digital image processing method and apparatus technologies. More particularly, the invention relates to image processing methods and image processing apparatus which can apply this image processing methods for typical use with digital photoprinters that read film images photoelectrically to produce prints (photographs) reproducing the images and which are capable of achieving one of the following results: producing a high-quality image even if the input image is taken with low-performance lenses as in films with lens, inexpensive compact cameras and low-cost digital cameras; correcting aberrations such as chromatic aberration of magnification and distortion that develop in the images taken with those low-performance lenses; producing a high-quality image free from the image deterioration due to lens aberrations even if the input image is taken with those low-performance lenses; and particularly performing image processing on the image data representing the image recorded on an image recording medium.
Heretofore, the images recorded on photographic films such as negatives and reversals (which are hereunder referred to simply as “films”) have been commonly printed on light-sensitive materials (photographic paper) by means of direct (analog) exposure in which the film image is optically projected onto the light-sensitive material to achieve its areal exposure.
A printer which relies upon digital exposure has recently been commercialized as a digital photoprinter, in which the image recorded on a film is read photoelectrically, converted to digital signals and subjected to various image processing operations to produce image data for recording purposes; recording light that has been modulated in accordance with the image data is used to scan and expose a light-sensitive material to record a latent image, which is subsequently developed to produce a finished print (photograph).
In the digital photoprinter, images are handled as digital image data and the exposing conditions for printing can be determined by image (data) processing. Hence, processing operations such as the correction of washed-out highlights or flat (dull) shadows due to the taking of pictures with rear light or an electronic flash and sharpness enhancement (sometimes referred to simply as “sharpening”) can be effectively performed to produce prints of the high quality that has not been attainable by the conventional direct exposure technique. In addition, the synthesizing of images and characters can be accomplished by image (data) processing and, as a ,result, prints can be output after editing and/or processing operations have been performed freely in accordance with specific uses.
Aside from the images recorded on films, the digital photoprinter can also output prints of images recorded with digital cameras or processed with computers. Other than being output as prints, images can be supplied to computers and so forth or stored in recording media such as floppy disks; hence, the image data can be put to various non-photographic uses.
Having these features, the digital photoprinter is basically composed of the following units: a scanner (image reading apparatus) that illuminates the film with reading light and captures the projected light to read the image on the film photoelectrically; an image processing apparatus that performs specified image processing on the image data captured with the scanner or the image data supplied from a digital camera or the like, thereby producing image data for image recording and exposing conditions; a printer (image recording apparatus) that scans and exposures a light-sensitive material to record a latent image on it, for example, by scanning with optical beams in accordance with the image data output from the image processing apparatus; and a processor (developing apparatus) that performs development processing on the printer exposed light-sensitive material to produce a print reproducing the input image.
Users in general who intend to take ordinary pictures seldom use expensive, high-performance cameras such as a single-lens reflex camera but they normally use so-called “compact cameras” that are inexpensive and which are capable of automatic exposing and focusing. Most recently, there are a lot of users who prefer using so-called “films with lens” by the reason of easy handling.
In cameras such as a single-lens reflex camera that needs a cost to some extent, high-precision lens elements are used, and a plurality of lens elements are combined to record images of very high quality.
In contrast, films with lens and inexpensive compact cameras cannot afford the use of costly lenses and only one or two lens elements may be adopted. With such lens design, images of adequate quality cannot be taken and the image reproduced on prints does not necessarily have high quality.
If the image recorded on films is deteriorated in quality, there is a case that the quality of the output image on prints cannot be adequately improved by the aforementioned corrections. Major causes of the deterioration of the image reproduced from films to be output on prints are lens aberrations such as “chromatic aberration of magnification” and “distortion” that, originate from the low performance of the lenses mounted in the camera used to take the input image.
Color images are formed of three primary colors, for example, red (R), green (G) and blue (B). The refractive index (imaging magnification) of a lens, even if it is a single element, varies subtly with wavelength and differing refractive indices occur with R, G and B lights. In other words, even though the same position in a particular scene, a focused position on a film are slipped off and differ among the R, G and B lights. This is the phenomenon generally called “chromatic aberration of magnification” and the image reproduced from the film has a definite color divergence.
In order to obtain a satisfactory and appropriately recorded image, a plane of a scene of interest that is perpendicular to the optical axis must be focused on the same plane as the imaging plane perpendicular to the optical axis. In fact however, ordinary lenses have the imaging plane displaced along the optical axis and the resulting displacement of the focused position in the axial direction causes a distortion of the focused object. As a natural consequence, the reproduction of the image on the film is distorted.
Other causes of the image deterioration are the reduction of the brightness at the edge of image field which means a phenomenon in which the peripheral area of the image looks darker than the central area which is closer to the optical axis corresponding to the performance of the lens used, and the point spread function (PSF) which is attributable to differing focal positions in the plane of the film.
As noted above, if one uses a camera such as a single-lens reflex camera that needs a cost to some extent, high-precision lens elements may be used and a plurality of lens elements combined to correct various aberrations including chromatic aberration of magnification, distortion, deterioration of marginal lumination and PSF and an appropriate image can be recorded on the film.
However, cameras such as films with lens and compact cameras required to be a low cost can not use high-cost lenses and aberrations will develop in the images recorded on films. As a result, the images reproduced on prints will eventually have color divergence and distortion.
To deal with this problem of image deterioration involving the difficulty in improving the quality of output images on prints, techniques have been proposed in connection with image processing methods and apparatus that correct image aberrations in accordance with the characteristics of lens aberrations that are obtained via certain image acquisition means and two typical examples of such technology are disclosed in Unexamined Published Japanese Patent Application (kokai) Nos. 311425/1994 and 281613/1997, the latter being assigned to the present Applicant. Acc
Brinich Stephen
Fuji Photo Film Co. , Ltd.
Lee Thomas D.
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