Casing Design of Visible and Long-Wavelength Infrared Coaxial Camera Considering Infrared Reflection by Optical Window

Abstract

Thermal imaging with long-wavelength infrared (LWIR) cameras is used for various applications including human detection and non-invasive measurements by measuring surface temperature of objects. As a camera that can increase the amount of information using both visible and LWIR lights while avoiding parallax, visible and LWIR coaxial cameras have been built that image both wavelengths on a same optical axis. Among them, a miniaturized coaxial camera that was able to be mounted on mobile robots. However, the camera faced a problem with image quality degradation a few minutes after startup. First, we clarified that the cause of the degradation was due to infrared reflections on the optical window of the camera casing. Second, we redesigned the casing lid with an inclined optical window. Finally, we confirmed that the redesign addressed the issue of infrared reflection.