Television – Image signal processing circuitry specific to television – Color balance or temperature
Reexamination Certificate
1998-05-18
2001-06-19
Eisenzopf, Reinhard J. (Department: 2614)
Television
Image signal processing circuitry specific to television
Color balance or temperature
C348S223100, C348S656000, C348S713000, C358S518000, C358S519000, C358S520000
Reexamination Certificate
active
06249323
ABSTRACT:
The invention relates to a white balance control method and device, and to a camera comprising such a white balance control device.
U.S. Pat. No. 5,461,429 discloses a white-balance and image-color control device which comprises a white balance coefficient setting unit and a white balance correction coefficient determination unit which determines first and second white balance correction coefficients to be applied to a luminance signal in accordance with the set white balance coefficients. The white balance coefficient setting unit determines a ratio of amplitudes in Red, Green and Blue signals, which will be reflected on the respective white balance coefficients. More specifically, the white balance coefficients can be set by hand with a variable resistor, or they can be set automatically in response to the input signals. How this automatic setting has to be effected is not described in this prior art document.
A luminance signal operation unit obtains first and second correction signals by multiplying the luminance signal by the first and second white balance correction coefficients, respectively. The first and second correction signals are added to first and second color difference signals, respectively.
It is, inter alia, an object of the invention to provide a practical white balance control. To this end, a first aspect of the invention provides a method as defined by claim
1
. A second aspect of the invention provides a white balance control device as defined by claim
5
. A third aspect of the invention provides a camera comprising such a white balance control device. Advantageous embodiments are defined in the dependent claims.
In a white balance control in which correction signals are added to input chrominance signals to obtain output chrominance signals in accordance with the present invention, chrominance sum signals are furnished from chrominance signals and reference chrominance signals, exponential signals are derived from the chrominance sum signals, and the reference chrominance signals are multiplied by the exponential signals to obtain the correction signals.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.
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patent: 6097445 (2000-08-01), Goto et al.
Biren Steven R.
Eisenzopf Reinhard J.
U.S. Philips Corporation
Yenke Brian P.
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