Dual-Band Imaging With an Integrated CMOS Image Sensor—Liquid Crystal Shutter Device

Dual-band imaging in the visible and near infrared (NIR) bands is used for remote sensing, surveillance, automotive, and other fields. CMOS image sensors (CISs), which are widely used in many imaging applications, can be used for dual-band imaging in visible and NIR because silicon is sensitive to light in these bands. There are various approaches for implementation of dual-band imaging systems. This article presents a single-sensor dual-band imaging approach that is based on integration of a CIS and a liquid crystal (LC) shutter. The proposed method is compared to dual-band imaging with an RGB-IR CIS, a single-sensor single-frame dual-band imaging approach that is commonly used at present. The comparison covers aspects that are related to image acquisition and image processing as well as image quality metrics and image artifacts. Signal and noise metrics are explained using a theoretical model and are evaluated from actual images. The still images in this work were captured with a camera that included an RGB-IR image sensor and a camera that included an integrated CIS and a LC shutter device. Images were captured in a controlled laboratory environment and outdoors. The images were used for a qualitative evaluation of the effects of relative resolution, stray light artifacts, and noise on end-user image quality, in addition to a quantitative evaluation of signal and noise properties. Advantages with each approach are summarized to highlight the system value-add of the two single-sensor dual-band imaging methods for certain applications.