Image analysis – Color image processing – Color correction
Reexamination Certificate
1999-07-14
2002-11-12
Couso, Yon J. (Department: 2623)
Image analysis
Color image processing
Color correction
C382S274000, C358S518000, C358S461000
Reexamination Certificate
active
06480625
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the technical field of density correction that will be a basis of performing an appropriate color reproduction in accordance with an original image and color correction which is capable of obtaining the appropriate color reproduction by correcting unevenness of spectral sensitivity characteristic and other various characteristics of an image reading apparatus (scanner) when the original image is photoelectrically read.
At present, most of the images recorded on photographic films such as negatives and reversals (which are hereinafter referred to as “films”) are printed onto light-sensitive materials (photographic papers) by a technique generally called “direct exposure” (analog exposure) in which the light-sensitive materials are exposed with the light projected from the films.
Reflection original such as printed matters, photographs or the like have also commonly been reproduced by means of analog exposure.
For the former case, printing apparatus which adopt digital exposure have recently been commercialized. In this “color digital printer”, the image recorded on a film is read photoelectrically and converted into digital signals, which are subjected to various kinds of image processing to produce recording image data; a light-sensitive material is scanned and exposed with recording light modulated in accordance with the image data, thereby recording a (latent) image which is then made to a (finished) print (photograph).
Also for the latter case, an apparatus employing a digital system has been commercialized as in a same manner as in the former case. Moreover, in the above-mentioned color digital printer, a so-called composite printer which can produce a copy (print) from the reflection original such as a printed matter, a photography or the like has recently been commercialized.
This composite printer is basically composed of a transparent original reading scanner for photoelectrically reading an image recorded on a film with an image sensor, a reflection original reading scanner for photoelectrically reading an image recorded on the reflection original such as a printed matter, a photograph or the like with an image sensor, an image processing apparatus for subjecting the image data read with those scanners or image data supplied from a digital camera or the like to preset image processing and making the image data to image data for recording the image, that is, setting an exposure condition based on the image data, a printer (image recording apparatus) for recording a latent image by scanning and exposing a light-sensitive material with, for example, a light beam scanning in accordance with the image data outputted from the image processing apparatus and a processor (developing apparatus) for subjecting the light-sensitive material having been exposed with the printer to development processing and for outputting a print on which the image is reproduced.
In such a composite printer, since the image can be read as digital image data and the exposure condition used in printing can be determined by subjecting the digital image data to image processing, a print of high quality which can not be obtained by the conventional direct exposure can be obtained, for example, from the image on the negative film, by properly executing the correction of a washed-out highlight and a dull shadow due to photography with back light or an electronic flash, sharpening processing and the like. Moreover, a plurality of images can be composited to a single image or one image can be split into segments through the image data processing. As a result, prints can be outputted after images are freely subjected to editing and processing in accordance with applications.
Further, also as to the image of the reflection original, various image processing can be performed to produce a high-quality print.
In the transparent original reading scanner or the reflection original reading scanner of the above composite printer, reading light is incident on an original, and projected light which has passed through the original (film) or reflected light which has been reflected from the original printed matter), is read with an image sensor such as a CCD sensor or the like thereby photoelectrically reading an original image.
In the case of a color original, the projected light or the reflected light of the original is processed with red (R), green (G) and blue (B) color filters or the reading light processed with the R, G, and B color filters is incident on the original, whereby the original image is read by being separated into the three primary colors R, G and B.
In the above situation, when scanners of the same type read the same original, they must obtain the same image signals (image data).
However, instrumental errors exist in light sources, color filters, image sensors and the like which are mounted on scanners. As a result, these scanners have different spectral sensitivity characteristics each other even if they are of the same type. Accordingly, since resultant image signals are influenced by the spectral sensitivity characteristic of each scanner, images having different color tints are produced with each scanner even if visible images are reproduced using the image signals. Thus, appropriate colors can not be always reproduced in accordance with the original, that is, an image of high-quality can not be always reproduced.
Similar problem exists with density. Even in a monochrome image, since the instrumental errors exist in light sources and image sensors installed in the scanner from one another, the image signals to be obtained differ from one scanner to another scanner so that an appropriate density can not be always reproduced in accordance with the original.
SUMMARY OF THE INVENTION
A first object of the invention is to solve the above problems of the prior art and to provide a method for correcting a density characteristic which will be a basis of performing an appropriate color reproduction in accordance with an original image by correcting unevenness of various characteristics of a scanner caused by a light source, an optical filter, an image sensor or the like and reading errors caused by this unevenness.
A second object of the invention is to solve the above problems of the prior art and to provide a method for correcting a color which is capable of obtaining a constant color reproduction by suitably correcting the unevenness of spectral sensitivity of the scanner caused by the light source, the color filter, the image sensor or the like and the reading errors caused by this unevenness.
In order to attain the above-described first object, a density characteristic correcting method according to a first aspect of the invention comprises:a first step of measuring a reference original with a preset measuring instrument to obtain a measured result and storing the thus obtained measured result in a storing means; a second step of reading the reference original with an image reading apparatus (scanner) which is a target to be corrected and obtaining a statistic by analyzing image signal values in a preset position within an image region of the reference original; a third step of reading out the measured result stored in the storing means; and a fourth step of calculating an input density characteristic correction parameter from the static obtained by the second step and the measured result read by the third step.
It is preferable that the density characteristic correcting method according to the invention creates a shading correction parameter before reading in the second step is performed and uses the thus created shading correction parameter when the reading in the second step is performed.
It is also preferable that in the density characteristic correcting method according to the invention, the image signal values obtained by measuring the reference original with the preset measuring instrument and a position information thereof are stored in the storing means as the measured result.
Moreover, it is further preferable that the input density cha
Couso Yon J.
Fuji Photo Film Co. , Ltd.
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