Perceptual evaluation of different image fusion schemes

Human perceptual performance was tested with images of nighttime outdoor scenes. The scenes were registered both with a dual band (visual and near infrared) image intensified low-light CCD camera (DII) and with a thermal middle wavelength band (3-5 Pm) infrared (IR) camera. Fused imagery was produced through a pyramid image merging scheme, in combination with different colour mappings. For all (individual and fused) image modalities, small patches of the scenes, displaying a range of different objects and materials, were briefly presented to human observers. The sensitivity of human observers was tested for different recognition tasks. The results show that greyscale image fusion yields improved performance levels for most perceptual tasks investigated here. When an appropriate colour mapping scheme is applied, the addition of colour to greyscale fused imagery significantly increases observer sensitivity for a given condition and a certain task. However, inappropriate use of colour significantly decreases observer performance compared to straightforward greyscale image fusion. This suggests that colour mapping should adapt to the visual task and the conditions (scene content) at hand.