Perfect RGB‐IR Color Routers for Sub‐Wavelength Size CMOS Image Sensor Pixels

Abstract

High‐resolution image sensing technologies have exploded over the past decade. A critical capability of all image sensors is to separate light into its individual color components. In most technologies today, this is done via color filters. Filters, however, intrinsically waste a large fraction of the light by absorption or scattering. This affects image sensor performance, because the amount of light incident on each image sensor pixel reduces quadratically with linear scaling of pixel size. This is particularly detrimental to the performance of (sub‐)wavelength size pixels. Herein, a conceptually novel approach is provided for color functionality in image sensors, by designing a color router that achieves perfect RGB‐IR color routing for sub‐wavelength size pixels. In a color router, all incident light for each color channel is routed directly and without loss to the photodetector of the corresponding color channel pixel. It is shown that color routers can be designed to near‐perfectly match a prescribed spectral shape, which is important for color image processing. It is further shown that these routers are designed to achieve specific spectral bandwidth and to meet angular as well as fabrication constraints.

Keywords

• CMOS image sensors
• color router
• optimization
• pixel scaling