Infrared isolation effectiveness of car windows film tester

This paper introduces the circuit and working principle of the infrared isolation effectiveness of car windows film tester. The circuit of the tester was constituted mainly by frequency modulating infrared light source, silicon photovoltaic cells, I/V convertor, A/D convertor and so on. The infrared wavelength range of the infrared light source is broader than the single infrared LED testing, which use two different wavelengths of infrared LED light sources to form composite wavelength light source. The methods which the circuit uses based on frequency domain is to suppress the interference of the stray light signal. When the light path is open, the actual measurement show that, the maximum difference is only 0.8% between the test result in sunlight and that in the darkroom. This paper also gives the test results and its analysis of which the 25 kinds of car windows films which are tested by the prototype machine.