Point-by-point visual enhancement with spatially and spectrally tunable laser illumination

Abstract

Vision is responsible for most of the information that humans perceive of the surrounding world. Many studies attempt to enhance the visualization of the entire scene by optimizing and tuning the overall illumination spectrum. However, by using a spatially uniform illumination spectrum for the entire scene, only certain global color shifts with respect to a reference illumination spectrum can be realized, resulting in moderate visual enhancement. In this paper, a new visual enhancement method is presented that relies on a spatially variable illumination spectrum. Such an approach can target much more dedicated visual enhancements by optimizing the incident illumination spectrum to the surface reflectance at each position. First, a geometric calibration of the projector-camera system is carried out for determining the spatial mapping from the projected pixel grid to the imaged pixel grid. Secondly, the scene is segmented for implementing the visual enhancement approach. And finally, one of three visual enhancement scenarios is applied by projecting the required color image onto the considered segmented scene. The experimental results show that the visual salience of the scene or region of interest can be efficiently enhanced when our proposed method is applied to achieve colorfulness enhancement, hue tuning, and background lightness reduction.