Tradeoffs With RGB-IR Image Sensors

Cameras with RGB-infrared (IR) image sensors are advantageous for applications that can benefit from simultaneous capture of color and near-IR (NIR) images. High quantum efficiency (QE) in NIR is desired for RGB-IR image sensors because it allows to reduce power of NIR illuminants, however, there is a tradeoff. As imaging with RGB-IR sensors is often done with visible/NIR dual bandpass filters, high NIR signal can lower the dynamic-range and the signal-to-noise ratio (SNR) of the color images. This work studies the effect of the NIR signal on the dynamic-range and the SNR of color and NIR images of RGB-IR image sensors. It presents a model that allows to evaluate these metrics using image sensor, camera, and scene parameters. The model is applied for the case of varied illuminant NIR content and for the case of varied pixel QE in NIR. Both cases are evaluated theoretically and experimentally, and experimental results are in good agreement with simulations.