Television – Camera – system and detail – With single image scanning device supplying plural color...
Reexamination Certificate
1999-04-14
2003-10-07
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
With single image scanning device supplying plural color...
C348S272000, C348S277000, C348S280000, C348S223100
Reexamination Certificate
active
06630956
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a color signal processing device and a color signal processing method which are applied to color digital cameras etc.
DESCRIPTION OF THE PRIOR ART
Today, color signal processing devices and color signal processing methods are widely employed in digital cameras which are used as input devices for computers. Especially, digital still cameras for shooting and recording still images are now being widely used to the same extent as the conventional cameras using AgCl films, and video meeting (teleconference) systems using digital cameras and computers are also being used. Also in the field of video cameras for recording moving pictures in magnetic tapes, digital video cameras are prevailing since image deterioration does not occur due to image processing. For processing image signals in such digital cameras, a special-purpose image processing logic circuit or a general-purpose CPU (and software) is utilized.
FIG. 1
is a block diagram showing an example of a conventional color signal processing device and a conventional color signal processing method for processing color signals outputted by a solid-state image pickup device. The conventional color signal processing device and the conventional color signal processing method are employed in video cameras for recording moving video pictures or digital still cameras for recording still images.
In the following, an example which employs a color filter shown in
FIG. 3
on a solid-state image pickup device (CCD)
200
will be explained, for instance. Referring to
FIG. 3
, each area on the color filter with a letter “R”, “G” or “B” corresponds to a pixel (element) of the solid-state image pickup device
200
. The area on the color filter with a letter “R” transmits red light and filters out green light and blue light. The area with a letter “G” transmits green light and filters out blue light and red light. The area with a letter “B” transmits blue light and filters out red light and green light. Each pixel (element) of the solid-state image pickup device
200
receives the red light, the green light or the blue light which passed the corresponding area of the color filter, and outputs an analog image output signal whose level corresponds to the intensity of the light that passed the corresponding area. The analog image output signal outputted by the solid-state image pickup device
200
is supplied to an A/D converter
201
. The AID converter
201
converts the analog image output signal into a digital signal and outputs the digital signal to a color interpolation section
202
. In the color interpolation section
202
, digital signals corresponding to colors (wavelength regions) which the area of the color filter did not transmit (in the case of the pixel corresponding to the area with the letter “R”, a green signal and a blue signal) are obtained by interpolation using digital signals (green signals and blue signals) from adjacent pixels. In the case where the color space of the output of the color interpolation section
202
is the RGB color space (i.e. in the case where the color filter on the solid-state image pickup device
200
has red areas, green areas and blue areas), signals outputted by the color interpolation section
202
are composed of a red signal r
0
, a green signal g
0
and a blue signal b
0
. The signals r
0
, g
0
and b
0
outputted by the color interpolation section
202
are supplied to a matrix operation section (color space conversion section)
203
having a 3×3 matrix. The matrix operation section
203
executes color space conversion to each signal using the 3×3 matrix so as to match a desired color space. The output of the matrix operation section
203
(a red signal r
1
, a green signal g
1
and a blue signal b
1
) can be obtained by the following equation. Incidentally, in the following, matrixes and vectors are represented by capital letters, and scalar quantities are represented by small (lower-case) letters.
(
r1
g1
b1
)
=
M
(
r0
g0
b0
)
M
=
(
m11
m12
m13
m21
m22
m23
m31
m32
m33
)
(
1
)
The 3×3 matrix M includes 9 color separation coefficients m
11
, m
12
, m
13
, m
21
, m
22
, m
23
, m
31
, m
32
and m
33
as its matrix elements. In the case where the color signal processing device is provided with white balance sections
204
,
205
and
206
, diagonal elements m
11
, m
22
and m
33
of the matrix M is set at
1
, and thus the matrix M substantially has 6 unique elements. If the color signal processing device is not provided with the white balance sections
204
,
205
and
206
, the matrix M has 9 unique elements.
The output of the matrix operation section
203
(the red signal r
1
, the green signal g
1
and the blue signal b
1
) is transformed by the white balance sections
204
,
205
and
206
as:
(
r2
g2
b2
)
=
WB
·
(
r1
g1
b1
)
(
2
)
where WB is a 3×3 diagonal matrix having three diagonal elements (white balance coefficients) wbr, wbg and wbb.
Subsequently, the red signal r
2
, the green signal g
2
and the blue signal b
2
outputted by the white balance sections
204
,
205
and
206
are supplied to gamma correction sections
207
,
208
and
209
respectively. The gamma correction sections
207
,
208
and
209
execute gamma correction to the red signal r
2
, the green signal g
2
and the blue signal b
2
respectively, and the output of the gamma correction sections
207
,
208
and
209
(a red signal r
3
, a green signal g
3
and a blue signal b
3
) is supplied to an output device
210
.
The conventional color signal processing device and the conventional color signal processing method described above involve the following drawbacks or problems.
First, in the case where a general-purpose CPU is employed for color image signal processing, a digital camera for recording still images is necessitated to take a long time for executing and completing the color signal processing since the moment the shutter button is pushed. In digital cameras for recording moving pictures, the number of frames can not be set large in comparison with the case where a special-purpose image processing logic circuit is employed for color image signal processing, therefore, it is difficult to obtain enough smoothness of the moving picture. Such problems occur due to processing speed of the general-purpose CPU.
Second, in the case where a special-purpose image processing logic circuit is employed for color image signal processing, the logic circuit has to include a large number of multiplication circuits. Therefore, the number of gates (i.e. the circuit scale) of the special-purpose image processing logic circuit in the digital camera for still images or in the digital camera for moving pictures is necessitated to be large, and thus power consumption of the digital camera is necessitated to be large. Especially in the case of a portable digital camera which is powered by a battery pack or batteries, continuous use (operation) time of the digital camera is necessitated to be short.
The above problems occur since the number of multiplications required in the conventional color signal processing device and the conventional color signal processing method is large (9 multiplications per one pixel in the equations (1) and (2)) and thus the conventional device and method are not suitable for real-time color image signal processing. Even in the case where the color image signal processing is executed by a special-purpose image processing logic circuit, 9 multiplication circuits having large number of gates become necessary, and thus it is difficult to reduce the power consumption of the digital camera.
SUMMARY OF THE INVENTION
It is therefore the primary object of the present invention to provide a color signal processing device, by which necessary circuit scale and power consumption of the logic circuit can be reduced.
Another object of the present invention is to provide a color signal processing device, by which color image signal processing with increased processing speed can be realized.
Another object
Dickstein Shapiro Morin & Oshinsky LLP.
Garber Wendy R.
Hannett James
LandOfFree
Device and method for processing color signals employing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device and method for processing color signals employing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device and method for processing color signals employing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3157095