Optical coherence tomography with balanced signal strength across the depth for pearl inspection

Abstract

Optical coherence tomography (OCT) relies on the reflection of light from structures in different layers to interferometrically reconstruct the volumetric image of the sample. However, light returned from multiple layers suffers from imbalanced attenuation owing to the optical path difference and inhomogeneous tissue absorption. We report an optimization algorithm to improve signal strength in deep tissue for swept-source (SS)-OCT imaging. This algorithm utilizes the attenuation coefficient of consecutive layers within the sample and combines them to compensate for the signal intensity loss from deep tissue. We stacked 170-µm thick cover slides as a standard sample for benchmark testing. The optimized OCT image provides a 30% increase in signal intensity in the deep structure compared with the conventional images. We applied this method for pearl inspection, whose layered structure demonstrates a great application for our optimized OCT imaging. In contrast to X-ray micro-CT scan and scanning electron microscope (SEM) imaging modalities, the optimized OCT imaging provides great potential for pearl quality inspection. The proposed improvement algorithm for SS-OCT could also be applied to diverse biomedical imaging scenarios, including label-free tissue imaging.

An Automated Grading Method of Pearl Roundness based on Optical Coherence Tomography

“…Next year, this research group [16] combined OCT with laser-induced fluorescence spectroscopy to identify the voids left in the pearl after bleaching, measured the average thickness of the nacre layer and the depth of the hollow layer after bleaching. Mao et al proposed an optimization algorithm to compensate the attenuated signals, thereby improving the signal to noise ratio of OCT images [17]. Our research group [18] also proposed a set of automatic algorithms based on OCT technology to distinguish the normal and defective sub-layer inside.…”