Television – Camera – system and detail – Combined image signal generator and general image signal...
Reexamination Certificate
2000-01-27
2004-04-13
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
Combined image signal generator and general image signal...
C348S273000, C348S208600, C348S252000, C358S525000, C382S300000
Reexamination Certificate
active
06721003
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus and storage medium storing an image processing program.
FIG. 22
is a view showing a representative electronic still camera system. Image data obtained by photographing an object with an electronic still camera
804
shown in (a) of
FIG. 22
is normally stored in a memory card
805
shown in (b) of FIG.
22
. When a color printer
801
shown in (c) of
FIG. 22
is connected via a connection cable, a color image can be printed on a medium of a size as small as about A6.
The memòry card
805
stored in a predetermined adapter can be inserted into a docking station
802
shown in (d) of FIG.
22
. An image can be observed on a TV monitor
800
shown in (e) of FIG.
22
through the docking station
802
. When an MO drive
803
shown in (f) of
FIG. 22
is connected to the docking station
802
, image data can be stored in an MO disk
806
shown in (g) of FIG.
22
.
Image data obtained by the electronic still camera
804
can be transferred to a desktop personal computer
809
shown in (h) of
FIG. 22 through a
connection cable. When the memory card
805
is stored in a predetermined adapter, image data can be loaded into a notebook personal computer
810
. In addition, image data in the MO disk
806
can be transferred to the notebook personal computer
810
through a predetermined MO drive. The monitor of the desktop personal computer
809
or the liquid crystal screen of the notebook personal computer
810
is capable of more precise display than the TV monitor
800
. An image can be printed by connecting a color printer
811
shown in (j) of
FIG. 22
, which is larger than the color printer
801
, to the desktop personal computer
809
or notebook personal computer
810
via a connection cable.
In the above electronic still camera system, the number of pixels of the electronic still camera is generally about 640×480 (about 300,000 pixels) to 1,280×1,024 (about 1,300,000 pixels). A TV monitor requires about 300,000 pixels, the monitor of a personal computer requires about 1,000,000 pixels, printing at 300 dpi on A6-sized paper requires about 1,300,000 pixels, and printing on A4-sized paper requires about 5,000,000 pixels. Even in the electronic still camera, the number of pixels relatively decreases upon digital zoom or photographing in a size ½×½ the number of pixels in accordance with the image quality mode. In the entire system, the number of pixels for input does not match that required for output in many cases.
Such an electronic still camera generally uses an imaging system using a one CCD, two CCD, or three CCD with spatial pixel offset. As a technique of improving resolution by spatial pixel offset, a general description is given in, e.g., Yuji Kiuchi, ed., “Handbook of Image Input Technique”, 1st Ed., Nikkan Kogyo Shimbun, Mar. 31. 1992, pp. 143-145 and pp. 259-260.
In this imaging system, one pixel is comprised of a plurality of color signals, and at least one color signal is often missed in accordance with the pixel position.
FIG. 23
shows the layout of complementary color mosaic filters of cyan (Cy), magenta (Mg), yellow (Ye), and green (G) generally used in a one CCD imaging system. Referring to
FIG. 23
, for the nth line and (n+1)th line of an even field, luminance signals are represented by Y
e,n
and Y
e,n+1
, respectively, and color difference signals are represented by C
e,n
and C
e,n+1
, respectively. For the nth line and (n+1)th line of an odd field, luminance signals are represented by Y
o,n
and Y
o,n+1
, respectively, and color difference signals are represented by C
o,n
and C
o,n+1
, respectively. These signals are given by
Y
o,n
=Y
o,n+1
=Y
e,n
=Y
e,n+1
=2R+3G+2B (1)
C
o,n
=C
e,n
=2R−G (2)
C
o,n+1
=C
e,n+1
=2B−G (3)
where Cy, Mg, and Ye are represented, using G, red (R), and blue (B), by
Cy=G+B (4)
Mg=R+B (5)
Ye=R+G (6)
As is represented by equation (1), luminance signals are generated in correspondence with all lines of even and odd fields. However, two color difference signals are generated only every other line, and each missing line is compensated by linear interpolation. After this, matrix calculation is performed to obtain three primary colors of R, G, and B. In this method, the color difference signal has an information amount only ½ that of the luminance signal, so an artifact called color moire is generated at an edge portion. Generally, to reduce color moire, a low-pass filter using a quartz filter is arranged on the front side of the imaging element. However, when the low-pass filter is inserted, the resolution becomes low.
Instead of simple interpolation using only the color difference signal, methods of correcting the color difference signal using the luminance signal component have been proposed. As one method, a luminance signal Y is prepared by linear interpolation. A color difference signal C is compensated by linear interpolation in a region where the change amount of the luminance signal Y is small. In a region where the change amount is large, the luminance signal Y is rearranged as
C′=
a
Y+
b
(7)
where a and b are constants to obtain a restored color difference signal C′.
In a technique disclosed in Jpn. Pat. Appln. KOKAI Publication No. 5-56446, the luminance signal Y is prepared by linear interpolation. For the color difference signal C, the luminance signal Y and color difference signal C are processed by a low-pass filter constructed by an electrical circuit to obtain their low-frequency components Y
low
and C
low
. The color difference signal C′ in which missing information is restored can be obtained by
C
′
=
Y
C
low
Y
low
(8)
This amounts to replacement of the color difference signal with a corrected luminance signal. In the above prior art, the color difference signal is corrected with reference to the luminance signal, though the luminance signal has an information amount only ½ that of the three CCD imaging system. In these techniques as well, a low-pass filter using a quartz filter must be used to reduce color moiré. For this reason, the resolution of the luminance signal serving as a reference further lowers, and an image quality equivalent to that of the three CCD imaging system cannot be realized.
As described above, in the prior art, a color difference signal is compensated by linear interpolation or on the basis of a luminance signal, and a missing color signal cannot be accurately restored at a high speed. Under the circumstance, the present invention has as its object to provide an image processing apparatus capable of accurately restoring a missing color signal at a high speed.
In the prior art, a luminance signal or color difference signal is generated by simple addition/subtraction in units of lines independently of edges or color boundaries in an image. Hence, false colors generated at edges or color boundaries cannot be reduced without sacrificing resolution. Under the circumstance, the present invention has as another object to provide an image processing apparatus capable of reducing false colors generated at edges or color boundaries without decreasing resolution.
In the prior art, a signal is processed without considering the relationship between the number of pixels of the imaging system and that of the output system, and therefore, an appropriate image quality cannot be obtained in an appropriate processing time. Under the circumstance, the present invention has as still another object to provide an image processing apparatus capable of obtaining an appropriate image quality in an appropriate processing time.
In the prior art, a signal is processed without considering the relationship between the number of pixels of the imaging system and that of the output system, and the
Tsukioka Taketo
Tsuruoka Takao
Frishauf Holtz Goodman & Chick P.C.
Olympus Optical Co,. Ltd.
Villecco John M
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