Contour filter for image sensor output signals
AssigneeKoninklijke Philips Electronics N.V.
InventorCornelis Antonie Maria Jaspers
Life of this patent
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Abstract
The present invention relates to digital image sensors and in particular to an aliasing free contour filter for RGB Bayer sensors. The filter (ZSB, 7) prevents an amplification of back folded aliasing artefacts and further eliminates green-green differences caused in the green color of the image sensor.
Claims8
A contour filter for providing contour information from an array of pixel values representing an image, said array comprises a first and a second group of pixels, the first group of pixels representing part(s) of the image optically filtered with a filter having a first color (G), and the second group of pixels representing part(s) of the image optically filtered with one or more filters having one or more second colors (R, B), each pixel in the first group having a vertical and a horizontal neighboring pixel of the second group, said filter comprising:
- means (ZSB) for converting said array of pixel values to a zero switched array, where the pixel values of the pixels in the second group are replaced by zero,
- means (7) for contour filtering said zero switched array and outputting said contour information, the filtering means comprising:
- means for calculating, for each pixel in the zero switched array, a filtered pixel value, said calculation being performed by using an array of filter coefficients having mutual ratios being substantially defined by:
- 6 −0 ± A −1x ± B −2x ± C −1x ± D −0 ± E −1x ± F −0 ± G +2x ± H −0 ± I −1x ± J −2x ± K +2x ± L +8x ± M +2x ± N −2x ± O −1x ± P −0 ± Q +2x ± R −0 ± S −1x ± T −0 ± U −1x ± V −2x ± X −1x ± Y −0 ± Z
- where x is a real number and the value of each of A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, X, Y, Z is between 0 and 0.25 x, and
- means for multiplying the pixel value of the actual pixel with the 8x+M coefficient and the remaining filtering coefficients with correspondingly positioned pixel values in the zero switched array and finally summing the resulting values.
A method of providing contour information from an array of pixel values representing an image, said array comprises a first and a second group of pixels, the first group of pixels representing part(s) of the image optically filtered with a filter having a first color, and the second group of pixels representing part(s) of the image optically filtered with one or more filters having one or more second colors, each pixel in the first group having a vertical and a horizontal neighboring pixel of the second group, said filter comprises,
- converting said array of pixel values to a zero switched array, where the pixel values of the pixels in the second group are replaced by zero,
- contour filtering said zero switched array and outputting said contour information, the filtering comprising:
- calculating, for each pixel in the zero switched array, a filtered pixel value, said calculation being performed by using an array of filter coefficients having mutual ratios being substantially defined by:
- 7 −0 ± A −1x ± B −2x ± C −1x ± D −0 ± E −1x ± F −0 ± G +2x ± H −0 ± I −1x ± J −2x ± K +2x ± L +8x ± M +2x ± N −2x ± O −1x ± P −0 ± Q +2x ± R −0 ± S −1x ± T −0 ± U −1x ± V −2x ± X −1x ± Y −0 ± Z
- where x is a real number and the value of each of A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, X, Y, Z is between 0 and 0.25 x, and
- multiplying the pixel value of the actual pixel with the 8×±M coefficient and the remaining filtering coefficients with correspondingly positioned pixel values in the zero switched array and finally summing the resulting values.
Dependencies are inferred from the claim text.