Television – Camera – system and detail – With single image scanning device supplying plural color...
Reexamination Certificate
1997-08-13
2003-02-18
Moe, Aung S. (Department: 2612)
Television
Camera, system and detail
With single image scanning device supplying plural color...
C348S275000
Reexamination Certificate
active
06522356
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color solid-state imaging apparatus, and more particularly to a color solid-state imaging apparatus capable of providing high color resolution in progressive scan reading.
2. Description of the Related Art
In recent years, there has been an increasing demand for a two-dimensional solid-state imaging apparatus used in an image input device for a personal computer and an electronic still camera. Conventionally, a two-dimensional solid-state imaging apparatus has been developed mainly for a video camera. Such a two-dimensional solid-state imaging apparatus basically uses an interlace reading method in which every other pixel is read in a vertical scanning direction. However, unlike the case of being used in a video camera, etc., in the case of being used in a personal computer and a still camera, a two-dimensional solid-state imaging apparatus is required to use a progressive scan reading method in which all the pixels are sequentially read at a time. The progressive scan reading method has the advantage of providing higher vertical resolution of an image obtained by one reading, compared with the interlace reading method.
Various single chip coloring methods for performing a color display using one two-dimensional solid-state imaging apparatus in the progressive scan reading method have been proposed. Various color filter arrangements applicable to the various simple plate coloring methods have also been proposed. Particularly in the case of attaching importance to color reproducibility, it is desired to use primary colors for color filters.
FIG. 17A
shows a color filter arrangement
500
including three primary colors of green (G), red (R), and blue (B) used in a two-dimensional solid-state imaging apparatus (progressive scan reading type charge coupled device (CCD)). The color filter arrangement
500
as shown in
FIG. 17A
is known as a Bayer arrangement, which is described, for example, in “A ⅓-inch 330 k-pixel Progressive Scan CCD Image Sensor” by Nakagawa et al., Technical Report of the Institute of Television Engineers, Sep. 22, 1995; “Color imaging array”, B. E. Bayer, U.S. Pat. No. 3,971,065, etc.
As shown in
FIG. 17A
, in the color filter arrangement
500
, twice as many pixels as those assigned to each of R and B are assigned to G, and G pixels are arranged in a checkered pattern. R and B pixels are arranged in an orthogonal lattice (i.e., lattice in horizontal and vertical directions) at a two-pixel period both in the horizontal and vertical directions. A luminance signal requires high resolution. Therefore, G pixels to which human eyes have high sensitivity are placed so as to occupy a half of all the pixels, whereby the resolution of a luminance signal can be increased.
FIG. 17B
shows spatial resolution characteristics (i.e., resoluble regions in each direction in a two-dimensional space) of the respective G, R, and B pixels in the color filter arrangement
500
. G pixels which largely occupy the luminance signal are arranged in a checkered pattern, whereby the luminance signal with relatively high resolution is obtained in the horizontal and vertical directions, as shown in FIG.
17
B. However, sufficient resolution cannot be obtained in oblique directions.
FIG. 18A
shows a color filter arrangement
510
including G, R, and B primary colors used in a two-dimensional solid-state imaging apparatus (CCD which operates in the same way as in a progressive scan reading type CCD). The color filter arrangement
510
as shown in
FIG. 18A
is described, for example, in “Digital card camera” by Soga et al., Technical Report of the Institute of Television Engineers, Mar. 4, 1993. In the same way as in the color filter arrangement
500
shown in
FIG. 17A
, twice as many pixels as those assigned to each of R and B are assigned to G which largely occupies the luminance signal in the color filter arrangement
510
. However, the G pixels are arranged in a stripe pattern, unlike the color filter arrangement
500
. In the color filter arrangement
510
, R and B pixels are arranged on a diamond lattice (i.e., skew lattice) at a two-pixel period in the horizontal direction and at a one-pixel period in the vertical direction.
FIG. 18B
shows spatial resolution characteristics of the respective G, R, and B pixels in the color filter arrangement
510
. As shown in this figure, the resolution of the luminance signal is relatively high in the vertical and oblique directions; however, the resolution of the luminance signal is not sufficient in the horizontal direction.
The two-dimensional solid-state imaging apparatuses using the above-mentioned color filter arrangements
500
and
510
are of a progressive scan reading type or an equivalent type thereof, and the pixels are arranged in the horizontal and vertical lattice. Therefore, there is a limit to spatial resolution characteristics in any color filter arrangement.
In the case of using an X-Y scan reading type apparatus as a two-dimensional solid-state imaging apparatus in place of a CCD, the degree of freedom of the pixel arrangement becomes larger. For example,
FIG. 19A
shows a color filter arrangement
520
of an amplifier-type two-dimensional solid-state imaging apparatus of a progressive scan reading type using an X-Y scan reading method. The color filter arrangement
520
as shown in this figure is described, for example, in “BCMD—An Improved Photosite Structure for High-Density Image Sensors” by J. Hynecek, IEEE Trans. on Electron Devices, Vol. 38, No. 5, May, 1991.
As shown in
FIG. 19A
, assuming that an arrangement in a horizontal line represents a “row”, the odd-number row (as counted from the topmost row) and the even-number row (as counted from the topmost row) in the vertical direction are shifted from each other by a 1/2 pixel pitch in the horizontal direction in the color filter arrangement
520
. The respective G, R, and B pixels are arranged in each row in the order of R-G-B at a three-pixel period. Furthermore, the respective G, R, and B pixels are arranged in such a manner that identical color pixels are shifted by a 3/2 pixel pitch in the odd-number row and the even-number row. Thus, as shown in
FIG. 19B
, the spatial resolution characteristics of each color pixel match with each other. Relatively balanced resolution is obtained in the G, R, and B pixels. However, the horizontal resolution is not sufficient.
In the case where a color image obtained in a two-dimensional solid-state imaging apparatus is taken in a personal computer, luminance signal pixels or G pixels are desirably placed in a square lattice (i.e., an orthogonal lattice in which a horizontal pitch is equal to a vertical pitch). However, the color filter arrangements
510
and
520
shown in
FIGS. 18A and 19A
cannot satisfy this requirement. If a horizontal pixel pitch L is prescribed to be ½ of a vertical pixel pitch M (i.e., L=M/2) in the color filter arrangement
510
shown in
FIG. 18A
, the above-mentioned requirement can be satisfied. However, when the horizontal pixel pitch L is substantially decreased, the performance of the two-dimensional solid-state imaging apparatus becomes likely to degrade. For example, in the case of a CCD type two-dimensional solid-state imaging apparatus, the amount of transferable signal charge is decreased, making it difficult to maintain a dynamic range.
In the case of an X-Y scan reading type solid-state imaging apparatus, the performance is more easily maintained as the pixel configuration becomes closer to a square or a circle as in the color filter arrangement
520
shown in FIG.
19
A.
SUMMARY OF THE INVENTION
The color solid-state imaging apparatus of this invention includes: a plurality of pixels conducting photoelectric conversion arranged in a matrix and color filters disposed so as to correspond to the plurality of pixels, wherein the color filters include first filters of a first kind, second filters of a second kind, and third filters of a third kind, each kind of filter having spectr
Conlin David G.
Dike Bronstein Roberts & Cushman
Moe Aung S.
Sharp Kabushiki Kaisha
Tucker David A.
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