Mobile Optical Coherence Tomography Sensor for Surface Layers Testing

2012 ◽  
Vol 518 ◽  
pp. 201-210
Author(s):  
Sławomir Tomczewski ◽  
Leszek Salbut
Keyword(s):  
Optical Coherence Tomography ◽  
Measurement Range ◽  
Optical Coherence ◽  
Surface Layers ◽  
Reference Mirror ◽  
Fringe Contrast ◽  
Contrast Analysis ◽  
Smart Pixel ◽  
Compact Design ◽  
Axial Scanning

In the paper the new type of mobile sensor based on optical coherence tomography is presented. For increasing the measurement range the special dynamic focusing system which moves imaging plane during axial scanning process is used. Therefore developed system allows focusing on measured layer. Additionally, for image analysis the special type of CMOS matrix (called smart-pixel camera), synchronized with a reference mirror transducer, is applied. Due to hardware realization of a fringe contrast analysis simultaneously in each pixel with high frequency, the time of measurement decreases significantly. These advantages together with a compact design allow the sensor to be used as the mobile device for measurements of surface topography, thickness of surface layers and subsurface defects detection in laboratory, workshop and out-door conditions. Calibration of the designed sensor and its application to the technological measurements of the sticker label layers are presented and discussed.

Three-Dimensional Reconstruction by Time-Domain Optical Coherence Tomography Microscope with Improved Measurement Range

2017 ◽  
Vol 11 (5) ◽  
pp. 787-794
Author(s):  
Shin Usuki ◽  
Katsuaki Tamaki ◽  
Kenjiro T. Miura ◽  
◽  
Keyword(s):  
Optical Coherence Tomography ◽  
3D Reconstruction ◽  
Time Domain ◽  
Interference Fringe ◽  
Measurement Accuracy ◽  
Three Dimensional ◽  
Measurement Range ◽  
Optical Coherence ◽  
Reference Mirror ◽  
Low Coherence

The objective of this research was to develop a three-dimensional (3D) reconstruction system based on a time-domain optical coherence tomography (OCT) microscope. One of the critical drawbacks of OCT microscopes is that their axial measurement ranges are typically limited by their depths of field (DOFs), which are determined by the numerical apertures of their objective lenses and the central wavelengths of their light sources. If a low-coherence interference fringe is far outside the DOF, the measurement accuracy inevitably decreases, regardless of how well-adjusted the reference mirror is. To address this issue and improve the axial measurement range of the OCT microscope in this study, an object-scanning measurement scheme involving a Linnik interferometer was developed. To calibrate the system in the proposed technique, image post-processing is performed for a well-conditioned state to ensure that a low-coherence interference fringe is generated within the DOF, enabling 3D objects with high-aspect-ratio structures to be scanned along the axial direction. During object-scanning, this state is always monitored and is corrected by adjusting the reference mirror. By using this method, the axial measurement range can be improved up to the working distance (WD) of the objective lens without compromising the measurement accuracy. The WD is typically longer than 10 mm, while the DOF of the microscope is around 0.01 mm in general, although it varies depending on the imaging system. In this report, the experimental setup of a 3D reconstruction system is presented, a series of experimental verifications is described, and the results are discussed. The axial measurement range was improved to at least 35 times that of a typical OCT microscope with identical imaging optics.

Optical coherence tomography image analysis of polymer surface layers in sound-absorbing fibrous composite materials

2017 ◽  
Vol 63 ◽  
pp. 194-203 ◽  
Author(s):  
Eulalia Gliścińska ◽  
Dominik Sankowski ◽  
Izabella Krucińska ◽  
Jarosław Gocławski ◽  
Marina Michalak ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Image Analysis ◽  
Composite Materials ◽  
Fibrous Composite ◽  
Polymer Surface ◽  
Optical Coherence Tomography Image ◽  
Optical Coherence ◽  
Surface Layers ◽  
Tomography Image

Extended measuring depth dual-wavelength Fourier domain optical coherence tomography

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Haroun Al-Mohamedi ◽  
Ismael Kelly-Pérez ◽  
Theo Oltrup ◽  
Alan Cayless ◽  
Thomas Bende
Keyword(s):  
Optical Coherence Tomography ◽  
Wide Spectrum ◽  
Michelson Interferometer ◽  
Dual Band ◽  
Human Model ◽  
Optical Coherence ◽  
Reference Mirror ◽  
Pass Filter ◽  
Wide Range ◽  
Sd Oct

Abstract In this work an enhanced wide range dual band spectral domain optical coherence tomography technique (SD-OCT) is presented to increase the depth and accuracy of the measurement of optical A-scan biometry. The setup uses a Michelson interferometer with two wide-spectrum Superluminescent Diodes (SLD). The emissions of the SLDs are filtered by a long-pass filter (900 nm) in front of the reference mirror. The light is spectrally decomposed using a single reflective diffraction grating (1,800 lines/mm) and the whole spectrum captured with two CCD line sensors. The capabilities of the system have been validated using a self-made human model eye.

scholarly journals Extension and Limits of Depolarization-Fringe Contrast Roughness Method in Sub-Micron Domain

Sensors ◽  
2021 ◽  
Vol 21 (16) ◽  
pp. 5572
Author(s):  
Franziska Pöller ◽  
Félix Salazar Bloise ◽  
Martin Jakobi ◽  
Jie Dong ◽  
Alexander W. Koch
Keyword(s):  
Scattered Light ◽  
Measurement Techniques ◽  
Michelson Interferometer ◽  
Measurement Range ◽  
Quarter Wave Plate ◽  
Contact Method ◽  
Reference Mirror ◽  
Fringe Contrast ◽  
Contrast Technique ◽  
Quarter Wave

To guarantee quality standards for the industry, surface properties, particularly those of roughness, must be considered in many areas of application. Today, several methods are available on the market, but some damage the surface to be tested as they measure it by contact. A non-contact method for the precise estimation of sub-micron roughness values is presented, which can be used as an extension of existing roughness measurement techniques to improve them further considering the depolarized light reflected by the sample. This setup is based on a Michelson interferometer, and by introducing a quarter-wave plate on a half part of the reference mirror, the surface roughness can be directly derived by measuring the fringe contrasts. This article introduces a simple model describing the intensity distortions resulting from the microscopic roughness in divided interferograms when considering depolarization. This work aimed to extend the measurement range of the technique developed in a previous work, in which depolarization effects are taken into account. For verification, the experimental results were compared with the fringe contrast technique, which does not consider the depolarization of the scattered light, especially regarding the extended wavelength interval, highlighting the limits of the technique. In addition, simulations of the experiments are presented. For comparison, the reference values of the sample roughness were also generated by measurements with a stylus profiler.

Spectroscopic optical coherence tomography based on wavelength de-multiplexing and smart pixel array detection

2004 ◽  
Vol 237 (4-6) ◽  
pp. 275-283 ◽  
Author(s):  
Markus Laubscher ◽  
Stéphane Bourquin ◽  
Luc Froehly ◽  
Boris Karamata ◽  
Theo Lasser
Keyword(s):  
Optical Coherence Tomography ◽  
Optical Coherence ◽  
Pixel Array ◽  
Array Detection ◽  
Smart Pixel ◽  
Smart Pixel Array
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