Television – Camera – system and detail – With single image scanning device supplying plural color...
Reexamination Certificate
1998-12-23
2004-06-29
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
With single image scanning device supplying plural color...
C348S222100
Reexamination Certificate
active
06757016
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image pickup apparatus that can obtain an image having a high resolution.
2. Related Background Art
In a conventional image pickup apparatus for generating an image signal, object light enters via a color filter (a filter array) and impinges on a light-receiving face composed of a plurality of photodiodes (hereinafter referred to as “pixels” or “light detectors”).
The color filter types available comprise a primary color filter and a complementary color filter. A primary color filter is an array in which filters for the three primary colors, red (R) and green (G) and blue (B), are positioned at individual pixels in a predetermined order on the light receiving face. Similarly, a complementary color filter is an array in which color filers for four complementary colors, cyan (Cy), yellow (Ye), magenta (Mg) and green (G) are arranged in a predetermined order.
The processing performed in accordance with a signal obtained by the image pickup apparatus will now be described, while the color filer used for the apparatus is, for example, the above described complementary color filter.
First, a cyan filter absorbs red light within a visible radiation range, and a yellow filter absorbs blue light within a visible radiation range. Whereas while a magenta filter absorbs green light within a visible radiation range a green filter transmits only green light.
The arrangements used for these color filters will be described later.
The image pickup apparatus, wherein object light enters through the complementary color filter array, obtains a pixel signal Cy that corresponds to the volume of the light that strikes a pixel after passing through the cyan filter, a pixel signal Ye that corresponds to the volume of the light that strikes a pixel after passing through the yellow filter, a pixel signal Mg that corresponds to the volume of the light that strikes a pixel after passing through the magenta filter, and a pixel signal G that corresponds to the volume of the light that passes through the green filter.
The thus obtained pixel signals Cy, Ye, Mg and G are used, as luminance signal Y and color difference signals CB and CR, for adjusting the iris or the white balance for a digital still camera or for a detection process performed during auto focusing, or for an image pickup apparatus that performs compression or decompression processing.
The luminance signal Y and the color difference signals CB and CR are represented by the following equations (1) to (3), in which the pixel signals Cy, Ye, Mg and G are used.
Y=Ye+G+Cy+Mg (1)
CB=(G+Ye)−(Mg+Cy) (2)
CR=(Cy+G)−(Ye+Mg) (3)
In
FIGS. 1 and 2
are shown example arrangement patterns for color filters in a complementary filter used for an image pickup apparatuses.
In the pattern shown in
FIG. 1
for the complementary color filter, color filters are so arranged that they have a cyclic pattern of two pixels horizontally (the direction corresponding to that of C
1
, C
2
, C
3
, . . . ) and four pixels vertically (the direction corresponding to that of L
1
, L
2
, L
3
, . . . ). In the pattern shown in
FIG. 2
for the complementary color filter, color filters are so arranged that they have a cyclic pattern of two pixels horizontally and eight pixels vertically.
With either complementary color filter, the luminance signal Y is obtained by performing the calculations for equation (1), for which are used the pixel signals Cy, Ye, Mg and G (shaded portions in
FIGS. 23 and 24
) for pixels in a four-pixel (2×2) block including two pixels horizontally and two pixels vertically. Similarly, the color difference signals CB and CR can be obtained by performing the calculations for equations (2) and (3) that employ the pixel signals Cy, Y, Mg and G for pixels in a 2×2 pixel block.
However, when a conventional image pickup apparatus, for which object light enters through the color filter shown in
FIG. 1
or
2
, is employed for a digital still camera, for example, the following problems have arisen.
(1) Before the shutter release is pressed, at the cost of resolution, a digital still camera reads pixel signals (in this case the above described image signals Cy, Ye, Mg and G) that are obtained by the image pickup apparatus (fast read mode), and based on these signals, displays images on the screen of a liquid crystal viewfinder or adjusts the iris or the white balance.
When the color filter shown in
FIG. 2
is employed for an image pickup apparatus, image pixels obtained by the image pickup apparatus can be read in the fast read mode, and the white balance can be adjusted based on the signals. However, when the color filter shown in
FIG. 1
is employed for an image pickup apparatus, and when for fast reading, at the cost of resolution, pixel signals for individual pixels are intermittently read vertically, only pixel signals Cy and Ye, i.e., pixel signals for only the two colors cyan and yellow, can be obtained, and the processing for white balance can not be employed.
(2) Recently, an image pickup apparatus, such as a CCD, has been provided wherein, by employing an elaborate signal reading method, object light is received at the light receiving face and pixel signals for two pixels that are perpendicularly adjacent to the light receiving face are added together, the resultant signal being transmitted to the transmission unit of the apparatus. As a result, the image pickup apparatus outputs paired pixel signals.
Specifically, when the color filter in
FIG. 1
is employed for an image pickup apparatus, for lines L
1
and L
2
paired pixel signals Cy, for a pixel that is positioned at (C
1
, L
1
), and Mg, for a pixel that is positioned at (C
1
, L
2
), are output first, and then paired pixel signals Ye, for a pixel that is positioned at (C
2
, L
1
), and G, for a pixel that is positioned at (C
2
, L
2
), are output, the pixel signal pairs being sequentially output in the same way. And when the output of signals for lines L
1
and L
2
has been completed, for the succeeding lines L
3
and L
4
paired pixel signals Cy, for a pixel that is positioned at (C
1
, L
3
), and G, for a pixel that is positioned at (C
1
, L
4
), are output first, and then paired pixel signals Ye, for a pixel that is positioned at (C
2
, L
3
), and Mg, for a pixel that is positioned at (C
2
, L
4
), are output, the pixel signal pairs again being sequentially output in the same way, and the output of signals for the lines L
3
and L
4
is completed.
That is, the pixel signals output for lines L
1
and L
2
are (Cy+Mg), (Ye+G), . . . , and the pixel signals output for lines L
3
and L
4
are (Cy+G), (Ye+Mg), . . . .
However, since luminance signal Y and color difference signals CB and CR are acquired from the above output signals, there are signals that can not be used for the calculations performed using equations (2) and (3) to obtain color difference signals CB and CR.
That is, while equation (2) is set up using (G+Ye) and (Mg+Cy), the output signals for lines L
3
and L
4
are (Cy+G), (Ye+Mg), . . . , and as a result, the calculations for which equation (2) is used can not be performed for lines L
3
and L
4
. Similarly, while equation (3) is set up using (Cy+G) and (Ye+Mg), the output signals for lines L
1
and L
2
are (Cy+Mg), (Ye+G), . . . , and as a result, the calculations for which equation (3) is used can not be performed for lines L
1
and L
2
.
As is described above, a solution for equation (2) can be obtained for the outputs for lines L
1
and L
2
, but no solution can be obtained for the outputs for lines L
3
and L
4
. Likewise, a solution for equation (3) can be obtained for the outputs for lines L
3
and L
4
, but no solution can be obtained for the outputs for lines L
1
and L
2
.
Therefore, color signals CB and CR for the individual colors can be obtained only for the pixel signals for one line, although pixel signal
Hiyama Hiroki
Kochi Tetsunobu
Koizumi Toru
Ogawa Katsuhisa
Sakurai Katsuhito
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Garber Wendy R.
Rosendale Matthew L
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