Authentic colour replication in adaptive LED-camouflage panels
A Proof of Concept (POC) demonstrator focusing on colour reproduction was designed to investigate the associated principles in the visible spectral range for adaptive camouflage. Consequently, this demonstrator was set up to deliver a fair replica of uniformly specified coloured backgrounds in various background light conditions using a controlled LEDmatrix- panel. For the panel adaption a camera monitors the predefined background colour whilst a regulator-circuit programme simultaneously processes this camera-signal to adjust the LED-colours. Extensive spectrometer measurements carefully quantify the colour replication accuracy. During these measurements the demonstrator and its regulator-circuit-programme were continually developed to handle the following three major concerns: RGB-channel-saturation, RGBchannel- cross-response and background-reflection-correction. The second (RGB-channel-cross-response) concern was mainly considered, which is caused by a mismatch between the spectral sensitivity of the measuring camera (CSS) and emitted spectral range of the LED-panel (SEP) and is relevant in darker environmental conditions. This disagreement causes a complex non-linear interaction behaviour between changes in the set RGB-values of the LED-panel and the camera measuring these changes for regulator circuit programme processing. So, changes in one RGB-component inadvertently affects other RGB-components. If not properly handled, this leads to an erroneous RGB-signal generation for the LED-matrix-panel and eventually to problematic colour-deviations between the panel and background. By spectrometer measurements investigating these emission and sensitivity components, specific white balance settings in the camera were determined to avoid such RGB-channel-cross-response. This replaces in a more elegant way the extensive characterization of the cross-response by response functions. The background was corrected by established standard procedures and worked correctly at the mainly considered darker surrounding illumination, where potential colour-deviations could be better examined. The application of such correction principles, especially with the here developed strategy for a careful chosen white balance setting (WB) wrt. the used regulation circuit method, allows a significantly improved colour-replication.