Method for the correction of video signals
View Patent ↗The invention relates to a method for the correction of video signals which are produced by pixel-by-pixel reading of picture cells from an optoelectronic sensor via two or more channels which have different transmission characteristics. In this case, the video signal is supplied to a processing circuit and is converted to digital pixel values. Estimated values for pixel values of another transmission channel are calculated from the digital pixel values of one transmission channel, and the estimated values and pixel values of one transmission channel are used to derive correction values, which correct differences between the estimated values and the pixel values of the relevant transmission channel, if necessary.
1. A method for the correction of video signals which, for each element of a transducer, are transmitted pixel by pixel as digital pixel values alternately via at least two channels having different transfer characteristics, where from the pixel values transmitted via a first of the channels, estimated values for each of the pixels of a second of the channels are formed by means of interpolation from the values of two linear adjacent pixels, and where correction values for the pixel values of the second channel are derived from differences between the estimated values and the pixel values of the second channel.
2. The method according to claim 1 , where the correction values are only formed from those differences which are less than a predetermined value.
3. The method according to claim 1 , where further estimated values are formed from pixel values which are transmitted by interpolation by means of the second channel, where further differences are formed from the further estimated values and the pixel values of the first channel, where an average value is in each case formed from the differences and the further differences, and in that the correction values are derived from the average values.
4. The method according to claim 2 , where further estimated values are formed from pixel values which are transmitted by interpolation by means of the second channel, where further differences are formed from the further estimated values and the pixel values of the first channel, where an average value is in each case formed from the differences and the further differences, and where the correction values are derived from the average values.
5. The method according to claim 3 , where the differences and the further differences are in each case subtracted from one another, and where the respective average value of the differences is only used for correction if the value produced by subtraction of the difference and the further difference is less than a further predetermined value.
6. The method according to claim 4 , where the differences and the further differences are in each case subtracted from one another, and where the respective average value of the differences is only used for correction if the value produced by subtraction of the difference and the further difference is less than a further predetermined value.
7. The method according to claim 1 , where the differences and the further differences, for the purpose of forming the correction values, are averaged separately according to the magnitude of the pixel values, where the correction values are written to a memory, and where the correction values are read from the memory depending on the respective magnitude of the pixel values and are added to the pixel values of the first and/or the second channel.
8. The method according to claim 3 , where the averaging is in each case effected separately according to the magnitude ranges of the pixel values, and where correction values are obtained for the individual pixel values by interpolation and low-pass filtering of the mean values within the various magnitude ranges.
9. The method according to claim 7 , where the averaging is in each case effected separately according to magnitude ranges of the pixel values, and where the correction values are obtained for the individual pixel values by interpolation and low-pass filtering of the mean values within the various magnitude ranges.
10. The method according to claim 1 , only pixel values which are evaluated are those which change at a rate which is below a cut-off frequency.
11. The method according to claim 1 , where only pixel values which are evaluated are those which change at a rate which is below the Nyquist frequency.
12. The method according to claim 10 , where the cut-off frequency depends on the predetermined value or on the further predetermined value.