Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1999-09-07
2003-11-11
Rogers, Scott (Department: 2624)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S003260, C382S275000
Reexamination Certificate
active
06646760
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the technical field of an image processing method and apparatus that are suitable for use with digital photoprinters and so forth that obtain image data from pictures taken with cameras, that perform specified processing schemes on the obtained image data and that produce prints (photographs) as output image. The image processing method and apparatus are capable of correcting the distortion, chromatic aberration of magnification and deterioration of marginal lumination that occur in the pictures taken with inexpensive and low-performance cameras such as films with lens and compact cameras.
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 projected onto the light-sensitive material to achieve its areal exposure.
A new technology has recently been introduced and this is a printer that relies upon digital exposure. Briefly, the image recorded on a film is read photoelectrically, converted to digital signals and subjected to various image processing schemes to produce output image data for recording purposes; recording light modulated in accordance with the output 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. The printer operating on this principle has been commercialized as a digital photoprinter.
In the digital photoprinter, images can be processed as digital image data to determine the exposure conditions for printing, so various operations including the correction of washed-out highlights or flat (dull) shadows due to the taking of pictures with backlight or an electronic flash, sharpening and the correction of deteriorated marginal lumination can be effectively performed to produce prints of the high quality that has not been attainable by the conventional direct exposure technique.
If the pictures taken and recorded on the films are distorted, the quality of the output image on the prints cannot always be improved by the aforementioned corrective measures. There are three causes of the distorted pictures and they are chromatic aberration of magnification, distortion and deterioration of marginal lumination , i.e. reduction in brightness at the edge of image field, which are all due to the low performance of the lenses mounted on the cameras used to take the pictures.
Color images are typically formed of three primary colors, red (R), green (G) and blue (B). The refractive index (imaging magnification) of a lens varies subtly with the wavelength of light and R, G and B lights are imaged at different magnifications to cause “chromatic aberration of magnification”. As a result, the image reproduced from the film has a definite color mismatch.
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 have an exact correspondence to the imaging plane, i.e., it must be imaged on the same plane perpendicular to the optical axis. In fact however, a single lens element has the imaging plane displaced along the optical axis and the resulting displacement of the imaging position in the axial direction causes a distortion of the imaged object. As a natural consequence, the reproduction of the image on the film is distorted.
Another problem with the pictures focused through the taking lens is that since the lens has such characteristics that the quantity of light decreases from the center of the image outward according to the so-called cosine
4
law, the quantity of light at the edge of the image becomes insufficient to assure the desired brightness. This phenomenon is generally called “deteriorated marginal lumination”.
Thus, due to the aberration characteristics of each taking lens, the output image becomes distorted and suffers from the problems of color mismatch, distortion and deteriorated marginal lumination.
In cameras such as a single-lens reflex camera that can compete at fairly high price, a plurality of high-precision lens elements are combined to ensure that various aberrations including chromatic aberration of magnification, distortion and deteriorated marginal lumination are effectively corrected to record appropriate images on the film. In contrast, low-performance and inexpensive cameras such as films with lens and compact cameras cannot afford the use of costly lenses and the images recorded on the film suffer from chromatic aberration of magnification, distortion and deteriorated marginal lumination. As a result, the images reproduced on prints become distorted.
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 an image processing method and apparatus that correct image aberrations in accordance with the characteristics of lens aberrations that are obtained by a lens information acquisition device and a typical example of such technology is disclosed in Unexamined Published Japanese Patent Application (kokai) No. 281613/1997. According to this patent, the proposed technology can correct aberrations due to lenses and prevent the deterioration of image quality in the marginal area, thereby ensuring the production of high-quality images at all times.
However, if the information about the taking lens cannot be acquired preliminarily or if the information about the taking lens can be obtained but the aberration characteristics of the lens cannot, the aberrations due to the low performance of the taking lens, namely, the distortion, chromatic aberration of magnification and deteriorated marginal lumination, cannot be dealt with by the aforementioned technology and the deterioration of the output image cannot be prevented. Even if the lens-related information is obtained and corrective values for performing aberration corrections are selected automatically on the basis of this information, the intended aberration corrections cannot be fully performed and it sometimes occurs that the aberrational distortion remains in the corrected image, making it impossible to prevent image deterioration. In this case, the operator who intends to remove the aberrational distortion in the appropriate manner can rely upon his experience to determine the appropriate corrective values manually and perform the appropriate corrections.
In fact, however, the same operator does not always perform manual corrections and the corrective values that are used in manual corrections vary with the operator's experience. This causes the problem that even if the same negative film is asked to be processed at one or more print output service shops, the desired prints cannot necessarily be obtained that have been given uniform and appropriate aberration corrections.
Conventionally, it is impossible for the operator to verify the image on the monitor after it has been corrected for aberrations and satisfactory prints cannot always be obtained unless a print is output from each of the corrected images to determine whether the correction is appropriate or not. However, this is not an efficient practice since it involves a waste of time and print outputs.
A further problem occurs if the information about the taking lens cannot be acquired preliminarily. Since corrective values cannot be obtained on the basis of the aberration characteristics of the lens, it becomes necessary to perform manual correction of the images in all frames of a roll of film. Although the same lens was used in taking the pictures and, hence, the aberration characteristics of the lens are fixed, the corrective values have to be set manually for each frame and the distorted image resulting from aberrations cannot appropriately be corrected in a rapid and efficient manner while assuring uniformity irrespective of which frames are processed.
SUMM
Birch & Stewart Kolasch & Birch, LLP
Rogers Scott
LandOfFree
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