Flame Light Field Imaging And Temperature Field Reconstruction Based On Wave Optical Theory

The temperature measurement technology of high temperature flame has always been an important research direction in the field of combustion,which is of great significance for combustion state diagnosis,fuel combustion process optimization,energy saving and emission reduction.Light field imaging temperature measurement technology has been widely developed as a new flame three-dimensional temperature measurement technology.However,there is still a lack of complete mathematical model of flame light field imaging.Most of the existing imaging models are simple combinations of radiation transfer equations and geometric optics,and lack systematic optical imaging theory.Therefore,this paper studies the flame field imaging and temperature field reconstruction based on the basic theory of wave optics.The main research contents are as follows:Based on the basic principle of light field imaging,combined with the theory of wave optics,the point spread function(PSF)of the light field camera is derived.Taking PSF as the optical transmission parameter,a Light Field Convolution Imaging Model of flame is proposed to realize the light field imaging simulation of the flame from the optical point of view,and the light field image of flame conforming to the optical imaging law is obtained.The method takes into account many physical parameters and their interrelationships,including units in radiation and optics and their conversion relationships.The effects of wavelength,optical transmission parameters,important structural parameters of the camera,and exposure time on the light field imaging results of the flame are fully considered.The light field imaging results show that the model can solve the problem of light field imaging of anisotropic flame well.Based on the Light Field Convolution Imaging Model,the strength calibration theory applied to the model is proposed.the temperature field reconstruction strategy is proposed,and the corresponding temperature field reconstruction strategy is further developed.Aiming at the need of inverse problem of temperature field reconstruction,a numerical solution algorithm with high computational efficiency and high precision and robustness is sought.Finally,the Landweber linear optimization algorithm is used to realize the three-dimensional temperature field reconstruction of the flame,the feasibility of the proposed Light Field Convolution Imaging Model and temperature field measurement method is verified.The results show that the Landweber linear optimization algorithm can still maintain high robustness when adding large calibration errors.