Sensor assembly providing gray scale and color for an optical image

Abstract

A sensor assembly and an optical image color scanner using the sensor assembly. The sensor assembly is of the type having three separate rows of optical sensors. Two of the three sensor rows have color filters and one is unfiltered (receptive to white light). For gray scale scanning, only the unfiltered (white) sensor row is used, thereby maximizing the speed of gray scale scanning. For color scanning, three color values are computed as a linear transformation of values from the two filtered and one unfiltered values. The linear transformation may be as simple as subtracting signals from the two filtered sensor rows from the signal from the unfiltered (white) sensor row. For color scanning, memory buffers are required for two of the three sensor output signals. For highest accuracy in color scanning, the exposure time for the white sensor row is reduced relative to the exposure time for the two filtered sensor rows. An optional white channel bandpass filter (passing all wavelengths within the human visual range and rejecting wavelengths outside the human visual range) provides improved accuracy if the light source has significant wavelengths outside the human visual range.