Colorimetric characterization of novel multiple-channel sensors for imaging and metrology

This paper describes a new type of multichannel color sensor with the special property of having all channels per pixel at the same spatial location. This arrangement is accomplished by stacking three amorphous thin film detectors on a substrate (glass or silicon), one on top of the other. It has the advantage that the color aliasing effect is avoided. This effect produces large color errors when objects of high spatial frequency are captured using multichannel imaging sensors with color filter arrays. The new technique enables the design of a three-channel sensor as well as a six-channel sensor, the latter being valuable even as a single-pixel device for metrology. In the six-channel case, color is captured in two ‘‘shots’’ by changing the bias voltages. The sensors are characterized colorimetrically, including methods such as multiple polynomial regression both for tristimulus and spectral reconstruction, and the smoothing inverse for spectral reconstruction. The results obtained with different types of regression polynomials, different sensors, and different characterization methods are compared. The results show that the new amorphous three-channel sensors perform comparably with commercial charge coupled device cameras under the conditions tested, while the six-channel’s performance is striking.