Towards Understanding the Role of Colour Information in Scene Perception using Night Vision Devices

Aviation Night Vision Devices (NVDs) are used to enable air operations under conditions of low illumination. The current generation of devices uses a single sensitivity band in either the infrared or near-infrared range. The next generation of such devices may include detectors at more than one absorption band. This has the potential to enhance the segmentation of different surfaces and features in the visual scene. Colour can be used to display contrast between sensor bands. Different schemes for representing spectral contrast are described, and are evaluated with respect to human colour sensitivity. Research on the role of colour in object and scene recognition is reviewed. The available evidence suggests that natural colour plays a useful role in scene recognition when objects and surfaces have prototypical colours. Misleading, false or "unnatural" coloration, which is a by-product of colour NVDs, may impair scene recognition and situational awareness. An experimental investigation of the effect of green monochrome imagery with altered surface reflectances, representative of current generation NVDs, showed a clear impairment in the recognition of complex urban scenes. The use of unnatural colour renderings in next-generation NVDs may lead to further impairment in scene recognition with consequences for situational awareness and effective navigation.