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Quality assessment of stereoscopic 3D images is much more complex than that of 2D images. Quality assessment metrics for 3D images have achieved good performance on symmetric distorted 3D images, while given poor performance on asymmetric distorted 3D images. To further improve the perception consistency for symmetric and asymmetric distorted 3D images, this paper presents a machine learning-based full-reference 3D image quality assessment method that learns from multi IQA metrics. Considering that changes in left view, right view and depth information all impact human perception, our method considers the quality of two views and depth information. Since symmetric and asymmetric distortions impact left and right views of a 3D image differently, we propose different features for symmetric and asymmetric distorted 3D images. The experimental results show that our method has better performance than both 2D-based 3D quality assessment metrics and the state of the art specially designed 3D quality assessment metrics.

By deposition of metallic vanadium on FTO substrate in Argon atmosphere at room temperature, the sample was then annealed in furnace for 2 h at the temperature of 410 °C in air ambient. (1 1 0) -orientated vanadium dioxide films were prepared on the FTO surface. A maximum transmittance of ∼40% happened at 900–1250 nm region at room temperature. The change of optical transmittance at this region was ∼25% between semiconducting and metallic states. In particular, vanadium dioxide thin films on FTO exhibit semiconductor–metal phase transition at ∼51 °C, the width of the hysteresis loop is ∼8 °C.

Real-time depth metrology during material removal via laser ablation is useful in many forms of laser machining. Until now, coaxial optical coherence tomography (OCT) metrology was achieved by the coupling of an OCT imaging beam and ablating beams using a dichroic filter. We present an alternative design with all fiber delivery that is more suitable for surgical laser ablation applications. The novel system design integrates a high peak-power pulsed Yb-doped fiber laser (1064nm) coupled directly into the sample arm of a swept-source OCT system (λ(c) = 1310nm). We measured the OCT signal degradation due to dispersion and attenuation through the ablation fiber laser cavity. Ablation progression is measured in real-time using M-mode OCT. The mean depth targeting error was found to range from 10µm to 80µm in phantom ablation experiments and 21µm to 60µm in bone ablation. A number of issues have been solved, including point-spread function (PSF) peak broadening due to signal delay and dispersion, high bending loss due to dissimilar fiber used throughout the design, and problems due to the extremely high ablation power to swept-source power ratio (> 2×10(4) peak to average power). To our knowledge, this is the first demonstration of thermal-mediated laser ablation drilling integrated with coaxial OCT imaging through a single-mode, single-cladded output fiber, without using dichroic beam splitters or free-space optic filters anywhere in the optical path and with this high ablation laser power to OCT source power ratio. The removal of bulk optics compared to existing designs opens a new path for compact integration of the entire system. Also, since the ablation laser and OCT feedback system exist along the same fiber path, the need for maintenance and repair are greatly reduced since spatial beam alignment and the potential open-air contamination of optical surfaces are virtually eliminated. We believe that this integrated system is a great candidate for adoption in depth-controlled surgical ablation applications.

A surgical laser soft tissue ablation system based on an adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser operating in pulsed or CW mode with nitrogen assistance is demonstrated. Ex vivo ablation on soft tissue targets such as muscle (chicken breast) and spinal cord (porcine) with intact dura are performed at different ablation conditions to examine the relationship between the system parameters and ablation outcomes. The maximum laser average power is 14.4 W, and its maximum peak power is 133.1 W with 21.3 μJ pulse energy. The maximum CW power density is 2.33 × 10sup6/supW/cmsup2/supand the maximum pulsed peak power density is 2.16 × 10sup7/supW/cmsup2/sup. The system parameters examined include the average laser power in CW or pulsed operation mode, gain-switching frequency, total ablation exposure time, and the input gas flow rate. The ablation effects were measured by microscopy and optical coherence tomography (OCT) to evaluate the ablation depth, superficial heat-affected zone diameter (HAZD) and charring diameter (CD). Our results conclude that the system parameters can be tailored to meet different clinical requirements such as ablation for soft tissue cutting or thermal coagulation for future applications of hemostasis.

Currently, visual saliency detection has been discovered and widely applied in the field of computer vision and image processing. Recent works have shown that considering human visual system features in image quality assessment will improve the consistence between objective assessment results and subjective visual perception. So we propose saliency-aware image quality assessment through a universal method to combine saliency detection with image quality assessment metrics. Since there is no image dataset used for image quality assessment and saliency detection researches simultaneously, we create a new image database, called TID-2013S, which is inheriting from image quality assessment database TID-2013 and contains 25 manually labeled ground truth images. In this paper, we select 8 representative full reference image quality assessment metrics and 7 state-of-the-art saliency detection algorithms to validate the performance of our proposed method. Experiment results show that when using the appropriate parameter of mapping function, our saliency-aware approach achieves the best performance improvement by 5.41%. And for most of image quality assessment metrics, the MCA saliency detection algorithm works best.

Tungsten–vanadium (W–V) co-sputtered thin films at a low cost were successfully synthesized on glass substrates by magnetron sputtering at room temperature and annealing under air atmosphere. The microstructures and optical properties of the thin films were characterized by four approaches, such as X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and spectrophotometer. XPS analysis demonstrated that W–V co-sputtered thin films were mostly composed of VO 2 and W 6 + , with a little amount of V 2 O 5 and other tungstovanadic compounds. XRD patterns illustrated that W–V co-sputtered thin films were polycrystal and W–V co-sputtered approach did not change the preferred orientation growth of the thin films. SEM micrographs displayed that VO 2 thin films were irregular in shape and distributed randomly, while W–V co-sputtered thin films had a rod-like morphology. Spectrophotometer spectra showed that W–V co-sputtered approach decreased the phase transition temperature from 68 °C to 40 °C, narrowed the thermal hysteresis loop from 6 °C to 3 °C, and made little influence on the infrared transmittance of pure VO 2 thin films.

A new theoretical model of the dual-FBG external cavity based on the couple-mode theory has been proposed for controlling the output spectral characteristics of the semiconductor laser with dual-FBG external cavity. The output spectral characteristics have been studied through the analyses of the external cavity length, the FBG length and the fiber length between the two FBGs. The results reveal that the side mode suppression ratio (SMSR), the full wave at half maximum (FWHM), the longitudinal mode interval (LMI) and the stability of the central wavelength are mainly determined by the effective external transmissivity, the fiber length between the two FBGs and the external cavity length, respectively. Furthermore, the rising/falling tendencies of the SMSR and the FWHM are exactly opposite. There exist the maximum of the SMSR and the minimum of the FWHM in a semiconductor laser with dual-FBG external cavity. The increase of the fiber length between the two FBGs results in the exponential decrease of the LMI. The increase of the external cavity length leads to the better stability of the central wavelength.

The use of gas assistance in laser machining hard materials is well established in manufacturing but not in the context of surgery. Laser cutting of osseous tissue in the context of neurosurgery can benefit from gas-assist but requires an understanding of flow and pressure effects to minimize neural tissue damage. In this study we acquire volumetric flow rates through a gas nozzle on the spinal cord, with dura and without dura.

This study presents the design of a system used to monitor laser ablation in real-time using Optical Coherence Tomography (OCT). The design of the system involves a high-powered fiber laser (wavelength of 1064nm, 1kW peak power) being built directly into the sample arm of the OCT system (center wavelength 1310). It is shown that the OCT laser light and subsequent backscatter pass relatively unaffected through the fiber laser. Initial results are presented showing monitoring of the ablation process at a single point in real time using m-mode imaging.

This paper presents the development of a compact, desktop laser-cutting system capable of cutting materials such as wood, metal and plastic. A re-commissioned beheaded MakerBot ® Replicator 2X is turned into a 3-DOF laser cutter by way of integration with 800W (peak power) fiber laser. Special attention is paid to tear-down, modification and integration of the objective lens in place of the print head. Example cuts in wood and metal will be presented, as well as design of an exhaust system.

VO 2 thin films were prepared on soda-lime glass substrates by DC magnetron sputtering at room temperature using vanadium target and post annealing in air. X-ray diffraction and FTIR spectroscopy analyses showed that the films obtained at the optimized parameters have high VO 2 (011) orientation. Both low temperature deposition and post annealing method were beneficial to grow the nano-films with pure VO 2 phase-structure and composition. Metal-insulator transition properties of the VO 2 films in terms of infrared transmittance, transmittance variation and film thickness were investigated under varying annealing temperature. Results showed that infrared transmittance variation and transition temperature of the nano-fil ms were significantly improved and redu ced respectively. Therefore, this study was able to develop practical low-cost preparation method s for high-performance intelligent energy-saving thin films. Keywords: VO 2 ; structure; thermochromic; transmittance 1. INTRODUCTION

We report an external stress modulation method for producing a superstructure fiber Bragg grating (FBG) with approximate cascaded resonant cavities composed of different index chirp distributions. The 15 mm uncoated apodized uniform-period FBG is pressed by the vertical stress from the upper 11 pieces of the pattern plate controlled by a piezoelectric ceramic actuator. The piece length is 1 mm, and the interval of the adjacent pieces is 0.4 mm. The reflectivity of the modulated FBG gradually shows six obvious multichannel 75%–85% reflection peaks with the increase of the vertical stress of each pattern-plate piece from 0 to 30 N. The channel spacing is steady at about 10 GHz for a C-band wavelength division multiplexing system.

For achieving uniform near-field illumination, this paper is based on the theory that each LED is non-perfect Lambertian emitter, whose irradiance distribution obeys the power law. Using the theory of sparrow's criterion, two methods to realizing near-field uniform irradiance of LED arrays are discussed by taking into account of the production process of LED array, a conclusion can be made that adjusting the curve to achieve uniform near-field irradiance is impossible but adjusting the space could. The structural characteristics of three typical LED arrays are analyzed. The equations of the relationship between illumination and space, as well as the optimal arrangements of the LED arrays are given. The nearfield optical properties for LED arrays with the optimal arrangement structure are simulated by MATLAB. By using a photometer we measure the irradiance intensity of the LED arrays, and make comparisons between experimental results and theoretical results, the result shows it works well.

The analytical expression of transmittivity and reflectivity of dual fiber Bragg grating (FBG) and the gain equations of the laser are obtained by the coupled mode theory. The laser gain curve is studied through the length of dual FBG and optical fiber length between two gratings under coherence collapse. The relative parameters have been optimized to get the best mode-stabilizing characteristics. The output spectral characteristics and the output power of the laser with dual FBG are practically measured. At the temperature of 0°C~70°C, the wavelength shift is 0.5nm. The side mode suppression ratio (SMSR) is more than 45dB. The Full Width at Half Maximum (FWHM) is less than 1nm.

Dispersion theory for refractive index and extinction coefficient of vanadium dioxide thin film is studied, and its temperature-dependence dispersion formula of optical constants is presented by numerical fitting with Sellmeier dispersion model. The optical transmittance and reflectance at different temperature and wavelength is calculated using film matrix theory. Vanadium dioxide thin films with different thickness are deposited by magnetron sputtering on glass, sapphire and silicon dioxide substrates, and the optical transmittance and reflectivity of the films are measured, and the experiment curve agrees well with that of simulation.

Much attention has been paid to the semiconductor-metal phase transition in vanadium dioxide nanomaterials, accompanied with an abrupt change in its resistivity and near-infrared transmission. The phase transition and optical properties of vanadium dioxide nanoparticles were studied by the mathematical model based on the complex refractive changing with the temperature and wavelength. The optical properties of nano-array were investigated by using the discrete dipole approximation and Mie scattering theory, as well as the absorption and scattering properties of small particles. The results show that the main contribution to the optical response with variational wavelength in the infrared is from absorption cross section comparing with the scattering cross section. It is obvious that the absorption peak of metal phase occurs near 980nm. With the change of temperature, the variation of extinction coefficient is larger in the infrared region than in the visible region. The largest change of extinction coefficient occurs in the near-infrared region. The extincition coefficient is very small in the visible region and there is a maximal value in the infrared region in the nano-array.

Gas assisted laser machining of materials is a common practice in the manufacturing industry. Advantages in using gas assistance include reducing the likelihood of flare-ups in flammable materials and clearing away ablated material in the cutting path. Current surgical procedures and research do not take advantage of this and in the case for resecting osseous tissue, gas assisted ablation can help minimize charring and clear away debris from the surgical site. In the context of neurosurgery, the objective is to cut through osseous tissue without damaging the underlying neural structures. Different inert gas flow rates used in laser machining could cause deformations in compliant materials. Complications may arise during surgical procedures if the dura and spinal cord are damaged by these deformations. We present preliminary spinal deformation findings for various gas flow rates by using optical coherence tomography to measure the depression depth at the site of gas delivery.

We investigate filter properties of chirped fiber Bragg grating (CFBG) (Fabry-Perot) F-P cavity through analyzing the coupled wave equation from one-dimensional Helmholtz equation. We derive an approximate formula of the reflectivity of a CFBG F-P cavity, simulate the central wavelength detuning, and calculate the central wavelength shift with the increase of ambient temperature. In the experiments, we measured the spectra of a diode laser with an FBG/CFBG F-P cavity at 0°C-110°C. The experimental results show that the CFBG F-P cavity can help a diode laser to obtain a less central wavelength shift and a narrower 3 dB reflection bandwidth, compared with the FBG F-P cavity at 0°C-110°C. The research results indicate that the CFBG F-P cavity is a potential wavelength stabilizer of uncooled diode laser.