Near Infrared Cameras to Capture Full Color Images : A Study of Color Reproduction Methods Without an Infrared Cut Filter for Digital Color Cameras

We propose a color reproduction method without an infrared cut filter (IRCF) for digital color cameras. The infrared cut filter in a camera eliminates infrared rays over 700 nm in order to adjust the spectrum sensitivity of the image sensor to the color-matching functions of the human eye. Without an IRCF, the spectrum sensitivity of the image sensor fails to satisfy the Luther condition. To achieve good color reproduction without an IRCF, we employed two techniques (: 1) a color correction matrix with nonlinear terms and (2) changes to the matrix coefficient according to the color temperature of illumination. Results demonstrate that our techniques enable a better color reproduction than conventional methods without an IRCF.