The Circuit Design And Data Analysis Of Photothermal Interferometer

The propagation of light in the atmosphere is often affected by atmospheric aerosol,atmospheric aerosol leads to the attenuation of light, by measuring the absorptioncoefficient of atmospheric aerosol can estimate the the strength of this effect. Themethod of photothermal interference measuring the absorption coefficient ofatmospheric aerosol is high accuracy and low uncertainty, designing a high accuratesystem to measure the atmospheric aerosol absorption coefficient is very urgent.In this paper, based on photothermal theory, deduce the mothod of measuringaerosol absorption coefficient. The paper research the method of photothermalinterference and the composition of system. By using improved Jamin interferometerreduces system cost and improves the control precision. A photoelectric convertingcircuit and a differential amplifier circuit are designed, and completed the design ofhardware and the system of set up. Using resistance wire and modulated lasers simulatephotothermal effect, and generate ideal interference fringe. This interference signal wassubdivided into360parts by using tangent mothod, the mothod can improve theaccuracy of measurement. At last, using the software of MATLAB process theexperimental data, calculate the amount of change of refractive index of air, andanalysis related factors of influence the change of refractive index of air.The research and experiment of this paper show that the measurement of theamount of change of refractive index of air can be achieved by Photothermalinterferometer, and it is high accuracy and low cost. In the conventional measurementenvironment, the minimum resolution of the system of measurement is one degree, andthe minimum amount of change of refractive index of air is3.51×(?). Using themethod of calculate the average of multiple measurements, analysis the errors ofexperimental method, the quality of signal and the system of measurement, and proposesome measures of reducing errors.