Patent ID: 7465948

Claim:
A sheet-surface analyser comprising: illuminating means for casting shadows on a sheet-surface; capturing means for capturing an image of the shadows; analysing means for analysing a captured shadow-image to thereby analyse the sheet-surface; and curving means for curving the sheet, wherein the illuminating means and the curving means are configured to enable the illuminating means to illuminate a curved part of the sheet-surface so that features of the sheet-surface cast shadows on the sheet-surface and the capturing means is configured to capture said shadow-image, the analysing means comprising a processor and a computer readable medium storing a computer program which when executed by the processor derives a matrix of rows and columns of light-intensity values from the captured shadow-image and calculates a sheet-surface value from the matrix wherein in calculating the sheet-surface value′ deviation values of respective rows and columns are calculated, the deviation value being a measure of average deviation of the light intensity values in said row or column from a mean value in said row or column, and wherein a selected region of the matrix comprising one row and/or column having a maximum deviation value is weighted to contribute more to the sheet-surface value than a remainder of the matrix.