We demonstrate the use of optical coherence tomography (OCT) as a non-destructive diagnostic tool for evaluating laser-processing performance by imaging the features of a pit and a rim. A pit formed on a material at different laser-processing conditions is imaged using both a conventional scanning electron microscope (SEM) and OCT. Then using corresponding images, the geometrical characteristics of the pit are analyzed and compared. From the results, we could verify the feasibility and the potential of the application of OCT to the monitoring of the laser-processing performance.

We designed and fabricated a telecentric f-theta imaging lens (TFL) to improve the imaging performance of spectral domain optical coherence tomography (SD-OCT). By tailoring the field curvature aberration of the TFL, the flattened focal surface was well matched to the detector plane. Simulation results showed that the spot in the focal plane fitted well within a single pixel and the modulation transfer function at high spatial frequencies showed higher values compared with those of an achromatic doublet imaging lens, which are commonly used in SD-OCT spectrometers. The spectrometer using the TFL had an axial resolution of 7.8 μm, which was similar to the theoretical value of 6.2 μm. The spectrometer was constructed so that the achromatic doublet lens was replaced by the TFL. As a result, the SD-OCT imaging depth was improved by 13% (1.85 mm) on a 10 dB basis in the roll-off curve and showed better sensitivity at the same depth. The SD-OCT images of a multi-layered tape and a human palm proved that the TFL was able to achieve deeper imaging depth and better contrast. This feature was seen very clearly in the depth profile of the image. SD-OCT imaging performance can be improved simply by changing the spectrometer’s imaging lens. By optimizing the imaging lens, deeper SD-OCT imaging can be achieved with improved sensitivity.

We proposed novel phase-shifting interferometry using a fiber-optic vibration sensor. The Doppler shift in the coiled fiber caused by vibrations can be used to detect the vibrations by using a...

We have developed a surgical microscope-integrated optical coherence tomography (MI-OCT) system based on an active feedback method to obtain uniform optimal OCT image contrast along the depth of focus (DOF) of a surgical microscope. Conventional MI-OCT systems use a shorter DOF objective lens than those of surgical microscopes for OCT imaging. The existing MI-OCT system was developed to overcome sensitivity roll-off by using an electrically tunable lens (ETL). However, active change in the focus position through the ETL cannot cope with the sensitivity decrease due to optical path length difference (OPD) mismatch. The proposed active feedback method was able to maintain high sensitivity by actively performing OPD matching using a linear motor in the reference arm while tuning the focal position in the sample arm using the ETL. The optical system designed to maintain the OCT resolution and a retroreflector used for ensuring regular reflection intensity in the reference arm during OPD compensation contributed to the uniform sensitivity and stable OCT imaging performance. The simultaneous and automatic actuation of the ETL and linear motor provided sensitivity variation of 3 dB from 17 dB for 10-mm sample displacement corresponding to the DOF of the surgical microscope used in the MI-OCT system. By using an infrared detection card and a mouse brain tumor model, it was demonstrated that the proposed MI-OCT system could acquire OCT images with optimal sensitivity without the limitations due to short OCT DOF.