Optical Description Of Fruit Tissue And Study Of Optical Transmission Discipline

With the human has more stringent requirements for fruit because of their living standard's improving, so the non-destructive inspection and grading technology has attracted more and more attention. Traditional non-destructive inspection technologies includes near infrared spectroscopy, hyper-spectral imaging, dielectric characteristics method and so on. Although these methods have achieved good results, the study of the on non-destructive testing equipment which based on these methods is still not mature enough, so this paper takes the apple as the example, measuring the absorption coefficient,reduced scattering coefficient, refractive rate and other basic optical parameters both of fruit skin and fruit flesh, establish realistic double layer(skin- flesh) fruit tissue model in three-dimensional coordinate axis, to simulate the optical characteristics at a wavelength of 808 nm light transmission in the fruit tissue using Monte Carlo method, it reveals the influence of different position of photon's incident point, fruit skin thickness to the light transmission characteristics in the fruit tissue, including distribution of the photon energy,the depth of the photon reached, the diffuse reflection and transmission, the detection sensitivity, establishing mathematical models between fruit tissue diffuse reflection and transmission, detection sensitivity and fruit skin thickness respectively. Provide theoretical basis for designing more effective optical detection equipment(such as the intensity of the light source, detector size and position, etc.) of fruit quality inspection,classification and grading of different types of fruit free design. Here are brief summaries about the main content and experimental conclusions of this paper.Research content:(1) Building a absorption coefficient and reduced scattering coefficient measurement system of fruit skin tissue and flesh tissue, based on the principles of single integrating sphere and reverse doubling method(inverse adding double method, referred to IAD method), obtained 100 sets of data both diffuse reflection and diffuse transmission, which is measured from the experiment in fruit skin tissue and flesh tissue respectively,calculated the final absorption coefficient and reduced scattering coefficient of the fruit skin tissue and flesh tissue. The refractive index of the fruit tissue was measured by an automatic Abbe refractometer.(2) Describing the whole procedures of Monte Carlo simulation, including the launch of a photon, the step's generating, the scattering direction's determination, the boundary's analysis and the processing methods of a photon's termination. Establishing a double(skin- flesh) layer fruit tissue model in a three-dimensional coordinate axis,analyzed the implementation of Monte Carlo simulation code, and the key technology of the simulation, then introduced the main functions of the Monte Carlo simulation.(3) Simulating the process of light propagation in the fruit tissue, studying the effect of the distribution of photons in the tissue when the incident angle and fruit skin thickness varies, including the max depth photon can reach, diffuse reflectance and diffuse transmittance, detection sensitivity, then creating math models about relation between penetration depth and fruit skin thickness, and relation between detection sensitivity and fruit skin thickness, respectively.Studies have shown that 2mm is the desirable thickness of samples of fruit tissue in measuring its basic optical parameters, if the samples are too thin, the scattering times will be too less to reflect the real case of photons transport in fruit tissues, if the samples are too thick, there will be too less photons can penetrate the samples., so the result won't be accurate. Results shown that 45 degree is the best incident angle when simulate the transmission properties of photons in the fruit tissue, and about the thickness of fruit skin,if the skin is thicker, the diffuse reflection and diffuse transmission is lower, and so are the penetration depth and detection sensitivity, there is a liner relationship between the penetration depth and the skin thickness, and also a linear relationship between detection sensitivity and the fruit skin thickness.