Joint spectral and depth domain spectral domain phase microscopy

For the needs of online nondestructive testing method in glass industry, we have presented a large-range line-field parallel spectral domain optical coherence tomography system. Based on fast area scan CMOS camera, the whole cross-sectional image can be acquired by a single shot. Depth-resolved image at different lateral positions can be acquired simultaneously, without the lateral scanning mechanism. The axial resolution is 17.9 μm, the lateral resolutions in parallel direction and scanning direction are 55.7 μm and 24.8 μm, respectively. The system measurement range is 32 mm in lateral direction and 6 mm in axial direction. At 1 mm axial position, the system sensitivity can reach 62 dB at a rate of 128 000 A-scan/s. By using the present system, application in glass defect inspection has been investigated.

Line-field parallel spectral domain optical coherence tomography and its application in defect inspection

Zhao¹,

Chen²,

Ding³

et al. 2014

Ultrahigh-resolution optical coherence tomography and its application in inspection of industrial materials

Tang¹,

Chen²,

Chen³

et al. 2015

Since many industrial materials have micro or submicro structures on the surface or subsurface, utrahigh-resolution is required in the inspection of these materials. Ultrahigh-resolution optical coherence tomography uses broadband light sources to achieve axial image resolutions on the scale of a few microns. We have been investigating an ultrahigh-resolution spectral-domain optical coherence tomography (SD-OCT) system using supercontinuum sources (SC) in free space. The effective SC spectrum has a full width at half maximum of 230 nm centered around 665 nm, and the imaging setup has an ultrahigh axial resolution of 0.9 μm in air, and a lateral resolution of 3.9 μm, with the system measurement range being 0.6 mm in axial direction. At a 50 μm axial position, the sensitivity can be 63 dB with 28600 axial scans per second at 2048 pixels per axial scan. Images of polystyrene microspheres solution with an average diameter of 5 μm and different sizes of industrial abrasive papers are presented to illustrate the performance of the system.

Wavenumber calibration and phase measurement in swept source optical coherence tomography

Shangguan¹,

Shen²,

Peng³

et al. 2016

Based on the phase information in time domain of a Mach-Zehnder interferometer (MZI), a method of calibrating the wavenumber of the source is proposed. Cross-correlation of wrapped phase in time-domain of the MZI is adopted to determine drifts among axial-lines. Owing to non-strictly periodic characteristics of wrapped phase in time-domain of the MZI, the determinable range of shift is unlimited. Synchronization of signals in time domain is then performed to correct their corresponding shifts. The obtained results demonstrate that it is feasible to realize phase measurement with high precision even under unstable swept source for the optical coherence tomography system.