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Automated Internal Classification of Beadless Chinese ZhuJi Fleshwater Pearls based on Optical Coherence Tomography Images

View Article: PubMed Central - PubMed

ABSTRACT

Optical coherence tomography (OCT) has been applied to inspect the internal defect of beadless Chinese ZhuJi fleshwater pearls. A novel fully automated algorithm is proposed to classify between normal and defective sub-layer in nacre layer. Our algorithm utilizes the graph segmentation approach to estimate the up and down boundaries of defect sub-layers from flattened and cropped image, and also proposes the strategy for edge and weight construction in segmentation process. The vertical gradients of boundary pixels are used to make grading decision. The algorithm is tested by typical pearl samples, and achieves 100% classification accuracy. The experiment result shows the feasibility and adaptability of the proposed approach, and proves that the OCT technique combined with proposed algorithm is a potential tool for fast and non-destructive diagnosis of internal structure of beadless pearl.

No MeSH data available.


OCT images of beadless Chinese ZhuJi fleshwater pearls that retained no defects and cracks (a), and the rest (b–f) contained internal defective sub-layer with various shape, angel and depth.
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f1: OCT images of beadless Chinese ZhuJi fleshwater pearls that retained no defects and cracks (a), and the rest (b–f) contained internal defective sub-layer with various shape, angel and depth.

Mentions: The beadless freshwater peal was wrap up by nacre that built up in layers. Figure 1 shows the OCT image of pearl samples with normal nacre layer (a) and with defective sub-layers (b)–(f). Chinese ZhuJi fleshwater pearls were prone to generate silts or plaques fulfilled with calcite or other organic matters. Lustre and transparency were key parameters of pearl quality, and they were decided by the reflection, interfere and refraction when light penetrated the nacre sub layers. Crystalline and alignment of aragonite crystal were related to the lustre and transparency, in principle, high crystallinity and ordered alignment meant higher values of pearls. But the calcite layer always mixed with organic composition that lowed the reflection of light. Excessive organic composition was the cause of irregular structure and caused the scatter of light. The OCT image was based on light interfere and revealed micromorphology and microstructure of pearls. Besides the inspection of internal structure of nacre, the OCT images could be used for detecting the defect layers. As shown in Fig. 1, the normal sample consisted of sub layers as the annual rings. The samples from Fig. 1(b–f) had amorphous crevices and blemished in nacre layer with larger pixel grayscale. From visual presentation of those samples in OCT image, we drew a conclusion that the OCT technique could identify the internal defect of beadless pearls.


Automated Internal Classification of Beadless Chinese ZhuJi Fleshwater Pearls based on Optical Coherence Tomography Images
OCT images of beadless Chinese ZhuJi fleshwater pearls that retained no defects and cracks (a), and the rest (b–f) contained internal defective sub-layer with various shape, angel and depth.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5036028&req=5

f1: OCT images of beadless Chinese ZhuJi fleshwater pearls that retained no defects and cracks (a), and the rest (b–f) contained internal defective sub-layer with various shape, angel and depth.
Mentions: The beadless freshwater peal was wrap up by nacre that built up in layers. Figure 1 shows the OCT image of pearl samples with normal nacre layer (a) and with defective sub-layers (b)–(f). Chinese ZhuJi fleshwater pearls were prone to generate silts or plaques fulfilled with calcite or other organic matters. Lustre and transparency were key parameters of pearl quality, and they were decided by the reflection, interfere and refraction when light penetrated the nacre sub layers. Crystalline and alignment of aragonite crystal were related to the lustre and transparency, in principle, high crystallinity and ordered alignment meant higher values of pearls. But the calcite layer always mixed with organic composition that lowed the reflection of light. Excessive organic composition was the cause of irregular structure and caused the scatter of light. The OCT image was based on light interfere and revealed micromorphology and microstructure of pearls. Besides the inspection of internal structure of nacre, the OCT images could be used for detecting the defect layers. As shown in Fig. 1, the normal sample consisted of sub layers as the annual rings. The samples from Fig. 1(b–f) had amorphous crevices and blemished in nacre layer with larger pixel grayscale. From visual presentation of those samples in OCT image, we drew a conclusion that the OCT technique could identify the internal defect of beadless pearls.

View Article: PubMed Central - PubMed

ABSTRACT

Optical coherence tomography (OCT) has been applied to inspect the internal defect of beadless Chinese ZhuJi fleshwater pearls. A novel fully automated algorithm is proposed to classify between normal and defective sub-layer in nacre layer. Our algorithm utilizes the graph segmentation approach to estimate the up and down boundaries of defect sub-layers from flattened and cropped image, and also proposes the strategy for edge and weight construction in segmentation process. The vertical gradients of boundary pixels are used to make grading decision. The algorithm is tested by typical pearl samples, and achieves 100% classification accuracy. The experiment result shows the feasibility and adaptability of the proposed approach, and proves that the OCT technique combined with proposed algorithm is a potential tool for fast and non-destructive diagnosis of internal structure of beadless pearl.

No MeSH data available.