Patent ID: 7535606

Claim:
A method of directly obtaining a luminance (Y) value for a luminance/chrominance representation of a scanline of a color scanned image, the method comprising: determining calibrated on-times of a red light source, a green light source, and a blue light source of a color contact image sensor (CIS), the CIS including a linear sensor array to collect reflected light; wherein the calibrated on-times correspond to obtaining optimal signal voltages by the linear sensor array for a red-green-blue (RGB) color space when measuring the reflected light; illuminating the scanline with the red light source, the green light source, and the blue light source, wherein: illumination time with the red light source is a first fraction of the calibrated on-time determined for the red light source, wherein the first fraction is derived from a known relationship between Y and the red light source; illumination time with the green light source is a second fraction of the calibrated on-time determined for the green light source, wherein the second fraction is derived from a known relationship between Y and the green light source; and illumination time with the blue light source is a third fraction of the calibrated on-time determined for the blue light source, wherein the third fraction is derived from a known relationship between Y and the blue light source; accumulating reflected light from all of the light sources at the linear sensor array, wherein the reflected light is accumulated as a plurality of reflected light voltage values; and obtaining the luminance (Y) value by summing the plurality of reflected light voltage values.