Design and experimental test of a novel surface blackbody with honeycombs

With the development of IR technology, there are increasing needs for surface BB. A novel surface blackbody (BB) with honeycombs for calibrating infrared (IR) imaging ranging 240~450K in the long IR wavelength bands of 3~15μm is developed and its features are experimental tested. Traditional radiant source of BB cavities are often with simple axisymmetrical structure, such as cylinder, cone, cylinder-cone, double cones, cylinder-inner cone etc. and possess small apertures which fit high temperature range application. As to middle-low temperature range, these radiant sources are not satisfied with the requirement of Minimum Resolvable Temperature Difference (MRTD). The honeycombed surface can provide consistent radiant flux with high effective emissivity more than 0.98 estimated theoretically. A circular area in diameter Φ100 mm of the surface is adopted for making surface BB. Around the circumference of the radiant surface, a short cylinder is added as a shield to eliminate the edge effect. Pt100 A resistors are used as temperature measuring sensors, and controlling system with PIC16F876 microprocessor embedded is designed. Since the requirement of temperature controlling precision is high and the system works at temperature near to environment, it is difficult to control the temperature of the system with high heat inertia and being easily interfered by environment. Fuzzy-PID switch control algorithm has been adopted to overcome the issue and to make the system manipulated continuously over large scope of temperature with high precision, stable, robust and convenient to communicate with computer. The process of fuzzy controller is design by using of Matlab fuzzy logic toolbox and the control program is compiled under CCS C compiler. The testing results show the system works well and can satisfy practical requirements.