Enhancing Low Light Color Imaging with pixel concept utilizing two vertically stacked detector layers

CMOS image sensor performance in ideal light conditions has been vastly improved over the years. However, for low light operation, there is much room for improvement. Monochrome sensors tend to dominate the field of low light imaging because their lack of color filters enhances their light collection. However, color is essential for proper object identification and target discrimination. Two junction pixels have been widely investigated for the purposes of enhancing sensitivity however, they produce only two color samples and so the use of color filters is necessary to produce at least 3 color samples. This makes them non-ideal for lowlight imaging. In this work, we investigate a two layer pixel concept which avoids the use of absorption color filters and enhances SNR performance. A conceptual illustration of this pixel is shown in fig. 1.