Nondestructive measurement device and method for thickness of pearl layer

Abstract

The invention relates to a nondestructive measuring device and method for thickness of a pearl layer. The device is composed of a terahertz time-domain spectral system host, a terahertz transmitting probe, a terahertz receiving probe, a pearl testing platform and the like, wherein the host is used for achieving the terahertz time-domain waveform measurement function, the terahertz transmitting probe is used for generating pulse terahertz waves and emitting the waves to to-be-measured pearls in a focusing mode; the terahertz receiving probe is used for collecting a terahertz time-domain waveform signal reflected by the to-be-measured pearls, the waveform signal comprises reflection peaks which are formed by reflecting the terahertz waves on the outer surface of the pearls and the internal bead core interface respectively, and the thickness of the pearl layer can be measured and calculated by measuring the time interval of the two reflection peaks. The device and the method have the remarkable technical advantages that the thickness of the pearl layer can be measured under a nondestructive condition, the precision can reach the micron order, and no radiation damage is caused to operators. The device and the method can be applied to quality evaluation of pearls.

Description

technical field [0001] The invention relates to a non-destructive measurement device for pearl beads, in particular to a device and method for non-destructive measurement of pearl layer thickness by using terahertz time-domain spectroscopy technology. Background technique [0002] The thickness of the pearl layer is an important index for evaluating the quality of pearls in the national standard of "Pearl Grading" (GB / T18781-2008). The method for measuring the thickness of the nacre indicated in this standard is a direct measurement method, that is, the cut and prepared pearl sample is placed under a microscope to measure its thickness. This is a destructive measurement, which cannot meet the needs of non-destructive testing of the pearl layer thickness in pearl trading activities. [0003] In order to realize the non-destructive measurement of pearl thickness, there are mainly two methods: X-ray detection and optical coherence tomography. Among them, the X-ray detection m...

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Problems solved by technology

The advantage of this method is that it can quickly scan the whole pearl, but the disadvantage is that for pearls with thinner nacres (such as: marine cultured pearls), X-ray imaging cannot clearly distinguish the dividing line between the nacre and the bead nucleus ; In addition, because X-rays have ionizing radiation damage to the human body, it is not suitable for long-term measurement

The advantage of the optical coherence tomography method is that the measurement process is safe and has no radiation damage, but the disadvantage is that it is limited by the penetration depth of light inside the pearl, and it is impossible to effectively measure the thickness of the pearl with a thick bead layer.

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