Television – Camera – system and detail – With single image scanning device supplying plural color...
Reexamination Certificate
1998-10-16
2003-05-27
Christensen, Andrew (Department: 2615)
Television
Camera, system and detail
With single image scanning device supplying plural color...
C348S237000, C382S205000
Reexamination Certificate
active
06570616
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of the following priority application is herein incorporated by reference: Japanese Patent Application No. 9-285536, filed Oct. 17, 1997.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an image processing method and device used, for example, in a color imaging device, and also to a recording medium on which is recorded an image processing program, and especially relates to pixel interpolation processing technology.
2. Description of Related Art
Generally, when a color image is photographed by using, for example, a video camera, a digital still camera or the like, incident light is passed through a filter and specified wavelength components in the incident light are extracted. In this way, for example, the light of each basic color component of R (red), G (green) and B (blue) is obtained.
Various methods of color image photography are known, such as a single plate method, a two-plate method, a three-plate method and a multiple-plate method, depending on the number of installed imaging units, e.g., CCD image sensors, in a device. However, in lower cost devices, often a single imaging unit is used.
When light from an object is separated into the three color components, R, G and B and all the color components are simultaneously photgraphed with a single imaging unit, three kinds of filters corresponding respectively to red, green and blue are arranged in a plane. The incident light which passes through the filter is directed at the imaging unit.
The two-dimensional image which is transmitted to the imaging unit is formed of many pixels that are arranged in the vertical and horizontal directions. Each pixel of the two-dimensional image includes only red, green or blue color light since the light has passed through one of the three kinds of filters corresponding respectively to red, green and blue.
For example, when the type of filter is changed for every pixel, and the filters are cyclically aligned in the order of R, G, B, R, G, B . . . in a horizontal direction, the color of pixels that are aligned in the horizontal direction become R, G, B, R, G, B . . . .
Accordingly, the information of the photographed object can be obtained only once every three pixels for any color component for red, green or blue. In other words, the object cannot be photographed other than in units of three pixels.
For all the pixels of the two-dimensional image, a pixel interpolation is implemented in order to obtain the color components of the red, green and blue colors. Therefore, information corresponding to color components of a missing pixel is created based on, i.e., interpolated from, information corresponding to pixels in the vicinity of the missing pixel.
Generally, when this kind of pixel interpolation is performed, a value corresponding to the interpolated pixel is formed by simply averaging values corresponding to a plurality of pixels that exist around the position of the pixel which is to be interpolated. Moreover, there is also a case in which the interpolated pixel is formed from two pixel values that remain when the maximum and minimum value pixels are removed from 4 pixels that exist around the position of the pixel to be interpolated.
Technology for detecting an edge of an image with reference to surrounding pixels of different color components based on a color component of an interpolated pixel is well known.
Additionally, Japanese Laid-Open Patent Application 6-339145, U.S. Pat. No. 5,373,322, U.S. Pat. No. 5,053,861 and U.S. Pat. No. 5,040,064 disclose methods and devices in accordance with what is known in the art.
However, when an interpolated pixel is formed by simply averaging the values of the plurality of pixels existing around the interpolated pixel, a high frequency component of a spatial frequency of an image is easy to overlook. In other words, the edge component is easy to miss. Accordingly, resolution of a photographed image is decreased.
Moreover, when an image edge is detected with reference to surrounding pixels with color components different from the color component of the interpolated pixel, image shifting occurs in image areas where a luminance change and a color change do not match.
Further, in order to form an interpolated pixel with a comparatively high quality, processing including various complicated calculations is necessary. Accordingly, a resulting device becomes incredibly complicated and processing speeds become slow.
SUMMARY OF THE INVENTION
Accordingly, aspects of the present invention are directed at realizing formation of a high quality interpolated pixel by comparatively simple processing.
The present invention relates to image processing in which, for example, pixels of a first color component of an image are arranged at every other pixel in vertical and horizontal directions on a two-dimensional pixel array. Pixels of second color component and third color component are arranged uniformly throughout remaining positions in the two-dimensional pixel array. At each pixel position, an interpolated pixel is generated by interpolation when a pixel color component does not exist at that position. When a pixel at a target position where the given color component does not exist is interpolated, a value associated with one of primary reference pixels of the given color component located adjacent to the target position at the top and bottom or left and right of the target position is compared to values respectively associated with secondary reference pixels of the given color component existing in the vicinity of the primary reference pixel to detect an image edge component. When an image edge component is detected, an interpolated pixel is formed based on reference pixels of the given color component at the top and bottom or left and right of the target pixel. Interpolation is further performed by applying a weighting coefficient for reference pixels at the top and bottom of the target position and a weighting coefficient for reference pixels to the left and right of the target position. The top-bottom weighting coefficient is set to a different value than the left-right weighting coefficient.
According to one aspect of the present invention, image processing with improved image edge component detection may be performed by forming an interpolated pixel based on reference pixels of a given color component existing at positions adjacent to the top, bottom, left and right of a target position. A weighting coefficient of reference pixels on a detected image edge may be set to be larger than the other reference pixels. Additionally, a total sum of weighting coefficients of reference pixels may be normalized.
According to an aspect of the present invention, image processing with improved image edge component detection may be performed by forming an interpolated pixel based on two reference pixels of a given reference color component existing in positions on a detected image edge and adjacent to the top, bottom, left or right of a target position. The weighting coefficient of the reference pixels that do not exist on the edge may be set to zero.
According to an aspect of the present invention, image processing with improved image edge component detection may be performed by comparing each of two primary reference pixels of a primary color component existing at the top and bottom or left and right of a target position with four secondary reference pixels of the given color component existing in the vicinity of the primary reference pixels. An image edge component is detected when comparison of the primary color components and the given pixel color components fulfills a predetermined condition.
Additionally, the present invention provides an image processing apparatus that provides the above-described image processing with the improved image edge component detection.
Further, another aspect of the present invention provides a recording medium on which is recorded an image processing program, to be carried out by a computer, which performs the above-described image processing with the impro
Christensen Andrew
Harris Tia M
Nikon Corporation
Oliff & Berridg,e PLC
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