Television – Camera – system and detail – Combined image signal generator and general image signal...
Reexamination Certificate
2000-10-25
2004-11-09
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
Combined image signal generator and general image signal...
C348S235000, C348S625000, C348S712000
Reexamination Certificate
active
06816193
ABSTRACT:
This application claims benefit of Japanese Application No. Hei 11-304875 filed in Japan on Oct. 27, 1999, the contents of which are incorporated by this reference.
BACKGROUND OF THE INVENTION
The present invention relates to image processing apparatus, and more particularly to an image processing apparatus having a digital image processing section including enhancement of edges in image to be displayed.
When an image is processed for edge enhancement, a technique is generally used to extract edge components within the image so as to add the extracted edge components to the original image. In such case, the edge components to be added are obtained by extracting high-frequency components of luminance signals of the image. In image pickup devices using RGB primary-color filter, the techniques for generating luminance signal to extract such high-frequency components include: (1) technique for generating luminance signal by using only G (green) signals out of all the color signals of RGB within the image; and (2) technique for generating luminance signal by using all the color signals of RGB in the image.
An example of construction of conventional image processing apparatus will now be explained by way of
FIG. 1
in which such two techniques are used to generate luminance signal to perform edge enhancement processing. Referring to
FIG. 1
, numeral
101
denotes an image pickup means; image signals of Bayer RGB array are obtained from the image pickup means
101
. The Bayer RGB array image signals are subjected to white balancing at a white balancing section
102
. Luminance data are then generated from 2G or (R+
2
G+B)/2 at a luminance data generating section
103
where R, G, B represent the outputs of the color signals of R (red), G (green), B (blue), respectively. The luminance data are then passed through a high-pass filter
104
to extract edge components and the degree of edge enhancement is adjusted at an edge enhancement adjusting section
105
to form edge signals.
On the other hand, image signals after the white balancing are separated of colors by pixel as a unit into RGB signals at color separation circuit
106
and then subjected to color correction and &ggr; correction at a color correction/&ggr; correction circuit
107
. The RGB signals are converted into Y, Cr, Cb signals at YC conversion section
108
. The above described edge signals are then added to the luminance signal Y outputted from YC conversion section
108
at an adder circuit
109
to obtain edge-enhanced luminance signal Y.
The above two techniques have their respective merits and demerits. In particular,
FIG. 2A
shows a part of image consisting of pixels of Bayer RGB array. In such image of Bayer RGB array, two times of image signals S are used in the case of generating luminance signal Y from
4
pixels of RGB (R+2G+B) as shown in
FIG. 2B
as compared to the case of generating luminance signal Y as shown in
FIG. 2C
from two pixels of G. The resulting noise N, on the other hand, is only 2
1/2
times from the theory of noise reducer. For this reason, supposing S/N at the time of generating from two pixels of G as 1/1=1, that at the time of generating from 4 pixels of RGB becomes 2/2
1/2
=2
1/2
. The case of generating from 4 pixels of RGB becomes 2
1/2
times better. Since, however, the signals of R, B, which contain not much genuine luminance information, are used as luminance signal when 4 pixels of RGB are used, excessively emphasized edges are generated and defects occur especially at the portion of boundary between two highly saturated colors.
As has been described, there are merits and demerits in both the case of using only G signal and the case of using all the color signals of RGB in generating luminance signal. These are summarized in Table 1.
TABLE 1
Luminance signal
Edge noise of high
Edge noise of low
generation method
S/N
saturation portion
saturation portion
From only G
Bad
Small
Large
From RGB
Good
Large
Small
Prior-art techniques according to some specific documents will now be described. Japanese patent application laid open Hei-10-108208 for example discloses a technique in which contour signals (edge components) are extracted from G signals to perform edge enhancement. Further, Japanese patent laid open application Hei-9-261513 discloses a contour (edge) enhancing method in which two types of contour extracting methods, i.e., MIX (mix) mode and NAM (non-average mix) mode are switched to each other according to the saturation of image. Here, MIX mode refers to generation of contour enhancement signal after addition of a plurality of signals corresponding to the three primary colors of RGB, etc., in the light of image to be displayed; NAM mode refers to generation of contour enhancement signal by adding one selecting the signal emphasized most in the direction of black and one selecting the signal emphasized most in the direction of white out of the respective contour enhancement signals of the above described plurality of signals.
Thus the problem is that there are respective merits and demerits as described above of the technique for generating luminance signal by using only G signals in the image to extract edge components and the technique for generating luminance signal by using all the color signals of RGB in the image to extract edge components. Further, the contour enhancement technique as disclosed in the above Japanese patent laid open application Hei-9-261513 has a problem that, if Bayer RGB array is used as the color filter array of image pickup device, the mere switching between the two types of contour extracting methods according to saturation alone may, depending on the colors of image, fall short of suitable processing due to lack of information. Furthermore, there is a problem of complicated construction in the NAM mode, since it is necessary to perform addition by respectively selecting one emphasized most in the direction of black and one emphasized most in the direction white out of the contour enhancement signals.
SUMMARY OF THE INVENTION
To eliminate the above problems in the conventional methods of edge enhancement processing of an image, it is an object of the present invention to provide an image processing apparatus having a digital image processing section including edge enhancement processing of simple construction having only the respective merits of the prior-art techniques.
In accordance with a first aspect of the invention, there is provided an image processing apparatus having a processing section for enhancing edges in an image, including: image pickup means for converting an object light into image signals of Bayer RGB array; color information detection means for obtaining color information of the object from the image signals obtained by the image pickup means; a first luminance data generation means for finding luminance data for use in edge enhancement processing from G signals out of the image signals obtained by the image pickup means; a second luminance data generation means for finding luminance data for use in edge enhancement processing from all color signals of the image signals obtained by the image pickup means; and luminance data switch means for providing an output by switching between outputs of the first and second luminance data generation means based on the color information obtained at the color information detection means.
By such construction, an output is provided on the basis of color information obtained at the color information detection means by switching between output of the first luminance data generation means for finding luminance data from G signal and output of the second luminance data generation means for finding luminance data from all color signals of the image signals. Hence edge enhancing components can be extracted on the basis of an optimal luminance data corresponding to the color information, an edge enhancement processing is possible with a favorable S/N and with less edge noise in high saturation regions and low saturation regions. The above object is thereby achi
Kohashi Atsushi
Sakurai Junzo
Garber Wendy R.
Olympus Optical Co,. Ltd.
Westerman Hattori Daniels & Adrian LLP
Ye Lin
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