Image analysis – Image enhancement or restoration – Image filter
Reexamination Certificate
2001-04-17
2004-10-19
Patel, Kanji (Department: 2625)
Image analysis
Image enhancement or restoration
Image filter
C382S232000
Reexamination Certificate
active
06807316
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image processing method and apparatus for reproducing a visible image from an image signal obtained by photoelectrically reading an image recorded in a reflective original such as a photographic print or any of other printed matters, or a transparent original such as a film, or from an image signal obtained by photographing an original image with a digital camera or the like using an image pickup device such as a charge-coupled device (CCD).
2. Description of the Related Art
Presently, the dominating method of printing on a photosensitive material (photographic paper) an image photographed on a photographic film such as a negative film or a reversal film (hereinafter referred to simply as a film) is a direct exposure (analog exposure) method in which an image formed on a film is projected onto a photosensitive material to perform surface exposure on the photosensitive material.
On the other hand, digital photoprinters have recently been put to practical use as a printing apparatus using digital exposure. That is, in the digital photoprinters, an image formed on a film is photoelectrically read and converted into a digital signal, which is processed by various kinds of image processing to generate a recording image signal, and an image (latent image) is formed on a photosensitive material by exposing the photosensitive material to a scanning beam of recording light which is modulated with the image signal, thereby obtaining a printed image (finished image).
The digital photoprinter is capable of determining exposure conditions at the time of printing by processing a digital image signal generated from an image. Therefore, it can suitably perform correction of an excessive light or dark condition of an image resulting from a flash photography condition or a strongly backlighted condition, sharpness (sharpening) processing, correction of a color failure and a density failure, correction of a result of underexposure or overexposure, correction of a reduction in peripheral light quantity, etc., to obtain a print at high quality level not attainable by the conventional direct exposure. The digital photoprinter can also perform synthesis of a plurality of images, division of an image, and synthesis of letters by image signal processing, and can output prints controllably edited and processed according to uses.
Moreover, the digital photoprinter can not only output an image in the form of a print (photograph) but also supply an image signal to a computer or the like or store the image signal on a recording medium such as a floppy disk to use the image signal in various uses as well as in photographic uses.
Basically, the above-described digital photoprinter is constituted by a scanner (image reader) which photoelectrically reads an image recorded on a film, an image processor which processes the read image to generate a recording image signal (exposure conditions), and a printer (image recorder) which forms a print by performing scanning exposure of a photosensitive material according to the image signal and by performing development on the photosensitive material.
In the scanner, light emitted from a light source is made incident on a film to be formed into, projected light carrying the image recorded on the film, and the projected light is imaged on an image sensor such as a CCD sensor and is photoelectrically converted into an electrical signal, thereby reading the image. The electrical signal undergoes various kinds of image processing according to one 's need to be obtained as a film image signal, which is supplied to the image processor.
The image processor sets image processing conditions from the image signal read by the scanner, processes the image signal under the set conditions to generate an output image signal (exposure conditions) for image recording, and sends the signal to the printer.
If the printer is, for example, a unit for performing light beam scanning exposure, it performs two-dimensional scanning exposure (printing) of a photosensitive material with a light beam by modulating the light beam according to the image signal sent from the image processor, thereby forming a latent image. The printer then performs a predetermined development process, etc., to output a print (photograph) in which the image recorded on the film is reproduced.
Ordinarily, the photographic conditions of images photographed on films vary and there are many cases where the difference between the maximum and minimum levels of light (density) is considerably large in photography using flashlight or in the presence of backlight, in other words, the dynamic range of an image is extremely wide.
If an image photographed on a film under such a condition is printed by performing an ordinary exposure process, there is a possibility of a light (highlighted) or dark (shadow) image portion becoming so light or dark that details thereof are lost. For example, in a case where a human figure in a backlighted state is photographed, a light portion, e.g., an image of a sky is so light that details thereof are lost if exposure is controlled so as to optimize the image of the human figure, or the image of the human figure is so dark that details thereof are lost if exposure is controlled so as to optimize the image of the sky.
For this reason, so-called dodging is performed when exposure of a photosensitive material is performed for printing of an original image which is a film image having a large variation from a highlighted portion to a shadow portion (a wide dynamic range).
Dodging is a technique for correcting the large variation from highlight to shadow in an image photographed on a film to obtain a print in which the image is suitably reproduced throughout the entire image area so that the image is closer to a viewer's impression of the original image. Correction of the variation from highlight to shadow is performed such that ordinary exposure is performed on a portion having an intermediate density, the amount of exposure of a light portion from which an excessively light image with loss of detail can result easily is increased, and the amount of exposure of a dark portion from which an excessively dark image with loss of detail can result easily is reduced. That is, dodging is a technique for compressing the dynamic range of an original image.
Various ideas of processing corresponding to the conventional dodging have been proposed with respect to the above-described digital photoprinter that reproduces an image on the basis of a digital image signal. Examples of such ideas are image processing methods and apparatuses disclosed in Japanese Patent Application Laid-open Nos. 09-18704, 09-182093, and 10-13679.
Japanese Patent Application Laid-open No. 09-18704 discloses a method of reducing the dynamic range of an original image such that an image signal representing the original image and a signal representing an unsharp image obtained from the original image (unsharp image signal) are processed to obtain a signal representing the difference therebetween, and this difference signal is processed by predetermined image processing to obtain a processed image signal, which is reproduced as a visible image.
Japanese Patent Application Laid-open No. 09-182093 discloses a method in which the unsharp image described in Japanese Patent Application Laid-open No. 09-18704 is formed by filtering through an infinite impulse response (IIR) filter. Japanese Patent Application Laid-open No. 10-13679 discloses a method in which a plurality of low-pass filters are provided, one of the plurality of low-pass filters having the mask size determined according to the pixel density of the reproduced image is selected to form an unsharp image of a varying mask size, and an unsharp image is formed by using the selected low-pass filter.
Each of these processing methods comprises a process in which a setting of the ratio of compression of the dynamic range of the whole of an image, a setting of compression of the dynamic range acc
Birch & Stewart Kolasch & Birch, LLP
Fuji Photo Film Co. , Ltd.
Patel Kanji
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