Design and Research of a Color Discrimination Method for Polycrystalline Silicon Cells Based on Laser Detection System

In this paper, a method of color discrimination based on sample sensitivity to light wavelength is proposed based on the reflection spectra of a large number of samples and the statistical calculation of the measurement data. A laser detection system is designed to realize the color discrimination. For the color discrimination of polycrystalline silicon cells, the most sensitive wavelength, 434 nm, and the least sensitive wavelength, 645 nm, of polycrystalline silicon cells is obtained according to this method. A laser detection system was built to measure the polycrystalline silicon cells. This system consists of two lasers, optical shutters, collimating beam expanding systems, an optical coaxial system, sample platform, collecting lens, and optical power meter or optical sensor. Two laser beams of different wavelengths are beamed coaxially through the optical coaxial system onto a polycrystalline silicon cell and are reflected or scattered. The reflected or scattered lights are collected through a lens with a high number aperture and received separately by the optical power meter. Then the color value of the polycrystalline silicon cell in this system is characterized by the ratio of light intensity data received. The system measured a large number of previous polycrystalline silicon cells to form the different color categories of polycrystalline silicon cells of this system in the computer database. When a new polycrystalline silicon cell is measured, the color discrimination system can automatically classify the new polycrystalline silicon cell to a certain color category in order to achieve color discrimination.

The use of single-crystal cuvettes with the properties of an optical shutter in X-ray diffractometers

The atomic structure of substances can be studied using X-ray diffraction methods. X-ray diffractometers contains X-ray source and goniometer with a detector of scattered radiation. A sample holder (a cuvette) with the material under study is placed in the center of the goniometer. The diffraction spectrum which represents the structure of the sample under study is recorded upon angular scanning of the sample and detector. Study of crystalline powders, amorphous substances, nanocrystalline and partially crystalline objects is often based on the Bragg-Brentano scheme (θ – 2θ-scanning) with divergent X-ray beams irradiating the entire sample surface. Scattered radiation from the cuvette can also enter the detector and affect the recorded diffraction spectrum. The aforementioned distortion is rather weak for polycrystalline samples due to strong intensity of crystalline reflections. However, when studying amorphous substances, nanocrystalline and partially crystalline objects, contribution of the scattered radiation can be compared with the radiation from the sample and thus interfere with an unambiguous determination of the sample structure. The results of using standard cuvettes for X-ray diffractometers D500, D5000 (Siemens), D8 ADVANCE (Bruker) and DRON are analyzed with a special attention paid to distortion of X-ray spectra attributed to the use of cuvettes made of plastic or amorphous quartz when studying amorphous, nanocrystalline and partially crystalline samples. Special cuvettes, being a kind of optical shutters for background scattering, which do not distort the diffraction spectra of the objects under study are developed: single crystal plates of a special orientation with cylindrical cavities for the samples. The advantages of a single-crystal silicon cuvette compared to plastic cuvette usually supplied for D500 diffractometer are estimated when studying an amorphous sample.