Research Of Emissivity Of Multi Rectangular Cavity Array

Infrared imaging technology has been widely used in military and civilian fields.High sensitivity infrared imaging system puts forward higher requirements for performance testing methods.The classical MRT test method is faced with the limitation that target and blackbody combinations can't achieve a continuously adjustable temperature difference.Due to the cumbersome test steps,many equipments required,high cost and other reasons,accurate performance testing can't be widely popular.A multi-rectangular cavity array was designed for the problems in the current performance of infrared imaging system.It consisted of a number of cavity elements,each element having a rectangular cavity with a defined depth and width ratio.Using an infrared camera to take a thermal image,each element would appear as a set of light and dark stripes.The apparent temperature of different elements was different on the thermal image.And the magnitude of the apparent temperature was determined by the normal emissivity of each element,and the magnitude of the normal emissivity of each element was determined by the shape factor r.The experimental samples of multi-rectangular cavity arrays were fabricated,and the radiant energy of each element was analyzed theoretically.The radiation model of the composite surface of the element was established,and the emissivity was calculated based on the theoretical formula.The normal emissivity was measured using the matching method,and the calculated value was compared with the actual measured value.The results showed that when r was large,the calculated value was close to the measured value,and the error was larger when r is small.Further research showed that with the increase of the shape factor r,the change of the apparent temperature tended to be stable.The minimum temperature difference was only 0.3 ? within 200?,and the maximum temperature did not exceed 2.1?.Therefore,the real surface temperature changes could produce the required temperature difference and the temperature difference was stable and controllable.It was proved that this kind of cavity array could be used to test the performance of infrared imaging system and could be used in the emissivity measurement comparison of most kinds of materials in industry.This was of great significance for the establishment of emissivity standard materials,emissivity standard data,and establishment of emissivity measurement traceability services.