Research on hyperspectral light and probe source location on apple for quality detection based on photon transmission simulation

Due to its high nutritional value, strong ecological adaptability and storage resistance, apple has become one of the world's most consumed fruits. At present, most of the tools mostly used in non-destructive testing of apples at home and abroad are hyperspectral instruments, but the hyperspectral apparatus has the following problems: First, the number of samples actually measured is extremely limited, the speed is slow, the cost is high, the coverage is small, and the error is inevitable. Second, the actual collection process consumes a lot of manpower and material resources. In view of the above problems, this paper proposes a new idea of improvement. Firstly, the Monte Carlo simulation of photon transmission on a multi-layer apple model based on ellipsoidal surface equation is implemented. Secondly, the trace of photons in the multi-layer apple model is analyzed. Based on this, the optimal incident position of the light source and the optimal detection position of the probe during the detection of the hyperspectral quality of the apple were analyzed and verified. The main works of this paper are as follows: 1) on the basis of realizing the Monte Carlo simulation algorithm of photon transmission, firstly, the multi-layer apple model based on ellipsoidal surface is studied. The apple model simulation based on ellipsoidal surface is realized by studying the motion behavior of photons on the surface, including normal vector solution, intersection point calculation and inverse refraction calculation. Finally, the two algorithms are optimized to a certain extent, and the parallelization of the two algorithms is realized by using MATLAB parallel computing toolbox, which improves the computing speed of the algorithm. 2) Based on the realization of the apple model photon transmission simulation, the optimal incident position of the apple hyperspectral quality detection source and the optimal detection position of the probe are further analyzed. Firstly, the photon motion of the light source at different positions of the apple model is simulated. The relationship between the incident depth and the different incident positions when photons are transmitted in the apple tissue is analyzed, and the optimal incident position is determined. By statistically analyzing the maximum incident depth of photons under different optical parameters and model sizes, it is found that photons have a better probability for reaching near the equatorial position of the apple to reach a deeper depth. At the same time, the effective photon ratio standard of photon scattering from the surface of apple model is defined, and the optimal range of source and probe distance when using applet to detect apple quality is proposed. The optimal detection range and apple optical parameters and apple model size parameters are analyzed. The correlation determines the factors that influence the change in the optimal detection area. The source distance is related to the optical parameters of the apple, and the shape is a ring. The radius of the inner and outer diameter of the source is 1.5~10.15 mm. The point source hyperspectral collects the spectral information of the red Fuji apple. The photon incident position is the equator, and the source distance is a circle with a radius of 2.7-11.7 mm, which is basically consistent with the simulation data analysis results. The Monte Carlo photon transmission simulation method opens up new ideas for studying non-destructive testing of high-spectrum apple quality.