Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1990-12-28
1993-09-21
Groody, James J.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358168, 358169, 358163, 358 37, H04N 5208
Patent
active
052473600
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a contour-emphasizing apparatus disposed in a television camera.
TECHNICAL BACKGROUND
In order to increase the sharpness of an image of an object, a contour-emphasizing apparatus is generally built in a television camera. In this contour-emphasizing apparatus, as shown in FIG. 5A, an image signal [a luminance signal in case of a black-and-white television and a signal of three elementary colors (a signal formed by mixing signals R, G and B) in case of a color television] is differentiated to extract a contour signal as shown in FIG. 5B, and this contour signal is added to the original image signal [an R(red) signal., a G(green) signal and a B(blue) signal in case of a color television] to obtain a contour-emphasized image signal as shown in FIG. 5C.
In this conventional contour-emphasizing process, since the level of the contour signal is determined, as pointed out above, by the differential value of the level of the image signal, that is, the difference of the level between both the sides of the contour, not only in the bright region where the level of the image signal is high but also in the dark region where the level of the image signal is low, the level of the contour signal is the same if the difference of the level between both the sides of the contour is the same, and therefore, the contour-emphasizing degree is the same.
However, it is known that the visual resolving power of a man in the dark region is less than that in the bright region, and the contour-discriminating capacity in the dark region is poorer. Therefore, according to the above-mentioned contour-emphasizing process, the contour of the dark region is obscure and the image is illegible.
If the level of the contour-emphasizing signal is indiscriminately increased so as to clarify the contour of the dark region, the contour of the bright region is excessively emphasized and an image having striking streaks in the bright region is formed and also this image is illegible.
The present invention has been completed under this background, and it is a primary object of the present invention to provide a contour-emphasizing apparatus in a television camera, in which by correcting the level of an image signal before the emphasis of the contour, the contour is appropriately emphasized not only in the dark region but also in the bright region to increase the image quality.
DISCLOSURE OF THE INVENTION
In accordance with the present invention, there is provided a contour-emphasizing apparatus in a television camera, where a contour signal is extracted from an image signal and the contour signal is emphasized and corrected according to the signal level, said apparatus being characterized in that a level-correcting circuit for correcting the image signal non-linearly to the signal level and outputting the corrected signal to a contour-emphasizing circuit is interposed.
In the contour-emphasizing apparatus having this structure, the image signal is corrected by the level-correcting circuit so that the signal becomes non-linear to the signal level, and the corrected image signal is outputted. For example, in the dark region where the level of the image signal is low, the image signal is corrected with a relatively high gain and the corrected signal is outputted. In contrast, in the bright region where the level of the image signal is high, the image signal is corrected with a relatively low gain and the corrected signal is outputted.
Since the level of the image signal is thus increased even in the dark region, the contour-emphasizing degree is increased and an image having a high resolving power and a clear contour can be obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram illustrating the structure of an embodiment of the contour-emphasizing apparatus in a television camera according to the present invention.
FIG. 2(A) is a circuit diagram illustrating an example of the level-correcting circuit used in the embodiment shown in FIG. 1.
FIG. 2(B) is a circuit diagram illustrating
REFERENCES:
patent: 4415920 (1983-11-01), Kato
patent: 4823190 (1989-04-01), Yamamoto
patent: 4843472 (1989-06-01), Shinada
Degawa Katsumi
Fujishima Keiichi
Ioka Shoichi
Kawada Norihiko
Groody James J.
Hsia Sherrie
Ikegami Tsushinki Co. Ltd.
LandOfFree
Contour-emphasizing apparatus in television camera does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Contour-emphasizing apparatus in television camera, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Contour-emphasizing apparatus in television camera will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1054238