| In astrophysics, atmospheric optics, marine optics, scattering phenomena of turbid media was studied early, and many kinds of theories about it were produced. Here, turbid media mean those media whose non-homogeneous quality of optics is very obvious and can produce intensive scattering phenomena. For example, the atmosphere suspending smoke and dust, the sea water suspending different microbe and impurity are belongs to "turbid media". Now, it is discovered that for light in 600-1300 nm wave range, the majority of biologic tissues were highly scattering and lowly absorbing media, as turbid media do. Furthermore, the light in this wave range has not hazard effect such as ionizing and radiation and so on. As a result it is very-fit for medicinal use. So, the study about scattering phenomena of turbid media is a hotspot of the photobiology.At the beginning of the study, forward scattering was studied widely. It was required by the need of pathologic tissue change imaging. Furthermore, theories in existence show that because of the turbid media's non-homogeneous the qualities of light will be damaged mostly, especially, the polarized quality. But now, more and more experimentation prove that in the direction of 180 degree back scattering, scattering light show a good ability of keeping its polarized quality. So, it carries a lot of information about the turbid media. Furthermore, the direction of 180 degree has the practicability because it can be detected easily. It was studied wildly in other countries, but it hasn't been studied in our country. Because that the experiment system of foreign used PEM-a costly equipment, it is difficult to be generalized. We plan to use our experience accumulated hi the technology of polarization optics measurement, combine the technology of weak signal, design and build our experiment system to study the character of 180 degree back scattering phenomena of turbid media. And, using the system, we plane to measure characteristic parameters, analyze factors thatwill affect scatting character.In this thesis, the first part introduces the significance of scattering, especially the back scatting in the turbid media. The scatting phenomenon is an important subject in atmospheric optics and marine optics. Recently, with the development of photobiology, the transmission window-was founded, so, this subject has big potential values to no-wrear detection or treatment.The second part introduced some basal concept example turbid media, scattering and back-scattering. Generally, the character of scattering can be expressed by scattering coefficient and scattering phase function. But this means to neglect the polarization factor. According "Black-Box" theory, this thesis takes three parameters that reflected turbid media's action to incidence light: optical rotation a, polarization-preserving p and reflectance r as 180?back-scattering character.The third part introduces the experiment system designed by us and its operating-principle. The followed part expresses the principle of measuring the 180?back-scattering characteristic parameters turbid media detailedly. First, the matrix of beam splitter and the matrix of turbid media were deduced. Afterward, using knowledge of matrix optics and measurement of weak signal, we get the expression of Stokes vector So of detected light including three unknown quantities. And, the values of Stokes vector So were got by Lock-in Amplifier. Adjusting polarizer P2,we can get a equations set including three characteristic parameters.Solving the equations set,we can get values of three parameters.In the fifth partwe do the specific measurement to the turbid media simulated by milk and the dehydronium.In the bases of the fifth part,the sixth part measures some turbid medias varied in the concentration of milk.and three characteristic parameters in different concentration are got.These conclusion can be got: (l)The concentration of turbid media canaffect three parameters in different degree. (2)In three parameters,polarization-preserv... |
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