Novel Polarization-sensitive Spectral Domain Optical Coherence Tomography using Single Camera Spectrometer

We report the use of spectral domain polarization sensitive optical coherence tomography for ex-vivo imaging of human oral mandibular tissue samples. Our results show that compared to the changes observed in the epithelium thickness and the decay constant of A-scan intensity profile, a much larger degree of change was observed in the phase retardation for tissue sites progressing from normal to the malignant state. These results suggest that monitoring of tissue retardance can help in better differentiation of normal and cancerous oral tissue sites.

We introduce a spectral domain polarization sensitive optical coherence tomography system with balanced detection capability. The design relies on polarization optics to split incoming light into reference and sample paths. Modified light returning from these paths creates the co- and cross-polarization channels, which are respectively coupled into two polarization-maintaining fibers. These fibers carry the light to a custom spectrometer, and their orthogonal axes help form the interference. The spectrometer produces two pairs of highly aligned and focused spectral lines on a camera for optimal balanced detection operation. System performance is characterized and demonstrated for biomedical imaging with improved signal-to-noise ratio.

Polarization sensitive optical coherence tomography (PS-OCT) is an imaging technique based on light scattering. PS-OCT performs rapid two- and three-dimensional imaging of transparent and translucent samples with micrometer scale resolution. PS-OCT provides image contrast based on the polarization state of backscattered light and has been applied in many biomedical fields as well as in non-medical fields. Thereby, the polarimetric approach enabled imaging with enhanced contrast compared to standard OCT and the quantitative assessment of sample polarization properties. In this article, the basic methodological principles, the state of the art of PS-OCT technologies, and important applications of the technique are reviewed in a concise yet comprehensive way.

Polarization sensitive Fourier domain optical coherence tomography (PS-FD-OCT) using fiber components with continuous polarization modulation is demonstrated. The incident polarized light is modulated by electro-optic modulator (EO modulator) synchronized with lateral B-scanning. By the incident polarization modulation and the polarization sensitive spectrometer, the depth-resolved Jones matrix image of biological sample can be measured. This method uses both polarization modulation method and Fourier transform method. In this paper, the algorithm is described and the phase retardation image of chicken breast muscle is measured.

Polarization Sensitive Optical Coherence Tomography (PS-OCT) measures the polarization state of backscattered light and provides information regarding its retardation and depolarization caused by propagation through tissue microstructure. Developing molecular contrast agents could enhance the utility of OCT for physiological, cellular, and molecular imaging. In this study, we characterize for the first time the depolarization signature of gold nanobipyramids (GNBPs) and demonstrate how depolarization can be used to enhance Spectral Contrast OCT based detection of GNBPs for multiplexed contrast agent detection.

Single camera spectral domain polarization-sensitive optical coherence tomography based on orthogonal channels by time divided detection

We report a simple implementation to acquire spectral domain polarization-sensitive optical coherence tomography (PSOCT) using a single camera. By combining a dual-delay assembly in the reference arm and offset B-scan in the sample arm, the orthogonal vertical- and horizontal-polarized images were acquired in parallel and spatially separated by a fixed distance in the full range image space. The two orthogonal polarization images were recombined to calculate the intensity, retardance and fast-axis images. This system was easy to implement and capable of acquiring high-speed in vivo 3D polarization-sensitive OCT images.

We report herein an alternative high-speed scanning force microscopy method in the contact mode based on a resonance-type piezoelectric bimorph scanner. The experimental setup, the modified optical beam deflection scheme suitable for smaller cantilevers, and a high-speed control program for simultaneous data capture are described in detail. The feature of the method is that the deflection and friction force images of the sample surface can be obtained simultaneously in real time. Images of various samples (e.g., a test grating, a thin gold film, and fluorine-doped tin oxide-coated glass slides) are acquired successfully. The imaging rate is 25 frames per second, and the average scan speed reaches a value of approximately 2.5 cm/s. The method combines the advantages of both observing the dynamic processes of the sample surface and monitoring the frictional properties on the nanometer scale.PACS07.79.Lh; 07.79.Sp; 68.37.Ps

We have developed a spectral interferometric optical coherence tomography (OCT) system with polarization sensitivity that is able to measure a two-dimensional tomographic image by means of one-dimensional mechanical scanning. Our system, which has an axial resolution of 32 mum , calculates the distribution of each element of the Müller matrix of a measured object from 16 OCT images. The OCT system successfully reveals the birefringent nature of human skin tissue.

Thick plates with different gauges have increased their use in various industries such as the shipyard and offshore industries. The arc welding techniques are the common ways to join the thick plates, which usually requires multi-pass and interlayer control. In addition, high heat input during arc welding also leads to the large distortion in the weld. Industries have shown increasing interest in using the hybrid laser-GMAW welding techniques to join different types of thick plates due to their high productivity, low distortion and excellent synergy of laser welding advantages and arc welding advantages. In this study, a 4 kW fiber laser is combined with gas metal arc welding (GMAW) to hybrid welding of half-inch mild steels. A 4 kW fiber laser, which leads a GMAW, is used to join the root of weld groove. Then, the following GMAW fills the groove. By using this welding procedure, the weld with full-penetration is achieved by one pass. In addition, a high-speed CCD camera is used to real-time monitor the welding process. Influences of different welding parameters such as the distance between laser power and GMAW torch and the gap on the weld quality are investigated.Thick plates with different gauges have increased their use in various industries such as the shipyard and offshore industries. The arc welding techniques are the common ways to join the thick plates, which usually requires multi-pass and interlayer control. In addition, high heat input during arc welding also leads to the large distortion in the weld. Industries have shown increasing interest in using the hybrid laser-GMAW welding techniques to join different types of thick plates due to their high productivity, low distortion and excellent synergy of laser welding advantages and arc welding advantages. In this study, a 4 kW fiber laser is combined with gas metal arc welding (GMAW) to hybrid welding of half-inch mild steels. A 4 kW fiber laser, which leads a GMAW, is used to join the root of weld groove. Then, the following GMAW fills the groove. By using this welding procedure, the weld with full-penetration is achieved by one pass. In addition, a high-speed CCD camera is used to real-time monitor the w...

We proposed and developed an optical system for imaging of the surface profiles of biological cells and tissues with nanometer resolution. The system is a low-cost system which can perform the imaging of the surface morphology in a large area and large depth range without any special preparation of the sample. The system consists of two interferometers in which one is in the configuration of a Michelson interferometer and the other is in the configuration of a Mach-Zehnder interferometer. The former is used for scanning of the surface profile of the sample, and the latter is used to compensate the phase shift due to the different traveling ranges of the reference mirror in successive scannings. The phase difference between the interferograms detected in both interferometers is proportional to the surface height of the sample at that point. The system was demonstrated to possess the axial resolution within ±5 nm and its lateral resolution is at the diffraction limit. We used the system for the imaging of various samples including biological cells and tissues. The system was also used for dynamic imaging to observe the morphological change of the surface of biological cells.

Acquisition time and optical sectioning capability are critical factors in fluorescence imaging. Confocal microscopy is a vital optical imaging method to inherently observe volumetric tissues with fine optical sectioning capability; however, point‐by‐point scanning is time‐consuming. Metasurfaces, a type of flat optics utilizing nano‐scale structures, provide diverse functionalities and extensive flexibility in controlling light wavefronts. Here, meta‐microlens‐array (meta‐MLA) for multifocal confocal fluorescence microscopy to enhance acquisition speed is introduced, reduce photo‐bleaching, and improve energy efficiency while remaining compatible with existing commercial scanning configurations. Point spread function (PSF) in the meta‐MLA confocal lateral and axial directions has been evaluated. Fast optically sectioned images of various samples, including pollen grains and biological tissue phantoms, are performed. Image quality is further enhanced by the Richardson–Lucy (RL) deconvolution method with total variation (TV). The trade‐off between spatial resolution and acquisition speed is overcome using deep neural network models, comparing performance metrics with a conventional confocal microscope. The combination of meta‐MLA confocal and deep learning with superior image quality and fast acquisition will likely extend the clinical applications of miniaturized optical imaging.

Low frequency vibrations (< 200cm^(-1)) contain the structural information of molecules or the crystal lattice - making low frequency Raman imaging an ideal candidate to analyze heavy molecules, crystal formation etc. The longer integration times of spontaneous Raman spectroscopy, however, limits the study of dynamic structural changes. In our work, we have built a stimulated Raman scattering (SRS) pump probe scheme combining impulsive excitation with a fast acousto-optics delay line. With a pixel dwell time of 25μs, we have acquired, on a shot noise limited detection system, sub second low frequency (< 200cm^(-1)) hyper-spectral SRS images of various samples.

Confocal Raman microscopy enables 3D imaging of various samples solely based on chemical contrast. However, optical artifacts impair resolution and image quality in subsurface imaging. With serial section Raman tomography, we show that serial ultrathin and semithin sectioning by ultramicrotomy can successfully be combined with subsequent confocal Raman imaging. This new 3D Raman imaging technique reaches a depth resolution of up to 100 nm, which is about 10‐fold better than in confocal Raman microscopy. Structurally complex and optically inhomogeneous samples can not only be imaged, but also be used to quantify structural parameters. Serial section Raman tomography is a promising method for materials science and possibly also for life sciences.

Walking robots have high adaptability for terrain variation, and thus, have been expected as effective moving platform on uneven terrain, stairs, forest, marshy surface, and on ice.On the other hand, mobile robots that perform several hazardous tasks such as mine detection or the inspection of an atomic power plant are typically controlled by operators from distant places. For a teleoperation system, use of visual information from a camera mounted on a robot body is very useful. However, unlike wheeled vehicles, the camera mounted on the walking robot oscillates because of the impact of walking, and the obtained unstable images cause inferior operation performance.In this paper, we introduce an image stabilization system for teleoperation of walking robots using a high speed CCD camera and gyrosensors. The image stabilization is executed in two phases, that is, the estimation of the amount of oscillation by the combination of the template matching method and gyrosensors, and change of the display region. Pentium MMX instruction is used for template matching calculation, and the estimated amount of oscillation is given in every 12 [msec] . Furthermore, developed image stabilization mechanism can be used an external attitude sensor from the visual information, and the damping control of the robot body while walking is also possible.Experimental results showed stabilized images that eliminates the oscillation component are taken even when the robot moves dynamically or in long distance, and verified that the performance of attitude control using the developed image stabilization system is almost same as the case using an attitude sensor.