JEOS:RP - Journal of the European Optical Society Rapid publications
Not a member yet
545 research outputs found
Sort by
Simple quasi-common path point diffraction interferometer with adjustable fringe contrast and carrier frequency
Full text linkThis paper presents a simple quasi-common path point diffraction interferometer (PDI) that allows fringe contrast and fringe spatial frequency to be adjusted conveniently. The novel aspect of this PDI is the use of a polarizer with pinhole as the PDI mask - and then, with a compact circular optical setup, reference and measurement waves are obtained. Furthermore, a linear tilting modulation is added into two interfering waves and adjusted easily by tilting the polarizing beam splitter - and hence the Fourier transform method can be perfectly applied to extract the wavefront phase from the captured fringe pattern, with the highest fringe contrast and suitable carrier frequency. Detailed theoretical analysis and experimental results are presented
Fourier ellipsometry – an ellipsometric approach to Fourier scatterometry
Full text linkAn extension of Fourier scatterometry is presented, aiming at increasing the sensitivity by measuring the phase difference between the reflections polarized parallel and perpendicular to the plane of incidence. The ellipsometric approach requires no additional hardware elements compared with conventional Fourier scatterometry. Furthermore, incoherent illumination is also sufficient, which enables spectroscopy using standard low-cost light sources
Coded access optical sensor (CAOS) imager
Full text linkHigh spatial resolution, low inter-pixel crosstalk, high signal-to-noise ratio (SNR), adequate application dependent speed, economical and energy efficient design are common goals sought after for optical image sensors. In optical microscopy, overcoming the diffraction limit in spatial resolution has been achieved using materials chemistry, optimal wavelengths, precision optics and nanomotion-mechanics for pixel-by-pixel scanning. Imagers based on pixelated imaging devices such as CCD/CMOS sensors avoid pixel-by-pixel scanning as all sensor pixels operate in parallel, but these imagers are fundamentally limited by inter-pixel crosstalk, in particular with interspersed bright and dim light zones. In this paper, we propose an agile pixel imager sensor design platform called Coded Access Optical Sensor (CAOS) that can greatly alleviate the mentioned fundamental limitations, empowering smart optical imaging for particular environments. Specifically, this novel CAOS imager engages an application dependent electronically programmable agile pixel platform using hybrid space-time-frequency coded multiple-access of the sampled optical irradiance map. We demonstrate the foundational working principles of the first experimental electronically programmable CAOS imager using hybrid time-frequency multiple access sampling of a known high contrast laser beam irradiance test map, with the CAOS instrument based on a Texas Instruments (TI) Digital Micromirror Device (DMD). This CAOS instrument provides imaging data that exhibits 77 dB electrical SNR and the measured laser beam image irradiance specifications closely match (i.e., within 0.75% error) the laser manufacturer provided beam image irradiance radius numbers. The proposed CAOS imager can be deployed in many scientific and non-scientific applications where pixel agility via electronic programmability can pull out desired features in an irradiance map subject to the CAOS imaging operation
Accuracy of the subsurface damage parameters calculated by the finite difference algorithm
Full text linkAn important approach to characterize the full three-dimensional information of subsurface damage is to simulate the etching process of a sample reversely. The simulation starts from the morphology of the sample after the subsurface damage micro cracks being opened totally. During the etching experiment, it is possible for us to get the surface morphology at any moment. This paper presents a finite difference algorithm to simulate the morphology evolution during the etching process and then the surface’s morphology of the sample at a specific time can be obtained. Comparison between the simulated morphology and the measured one provides the clue of improving the precision of the finite difference algorithm. This method is kind of the fast calculation. In addition, the accuracy of this calculation of the corrosion model needs to be ensured. In order to improve the precision of calculation, the time interval should be set as the appropriate value by comparison and analysis. In this paper, the accuracy can be calculated through comparing the simulated result with the experimental result, and the maximum error of this method can be gained
High-speed, high-accuracy 3D shape measurement based on binary color fringe defocused projection
Full text linkA widely used method in high-speed 3D shape measurement, color-code fringe projection requires the projection of only one image. In traditional color-code method, the projected fringe is compounded by sinusoidal fringes, grayscale value distribution ranges from 0-255, and projection speed is limited to 120 frames/s. Consequently, measurement speed is restricted, and a nonlinear gamma of the projector exists, as well as high harmonics, which have a great influence on measurement accuracy. Binary color-code fringe defocused projection is proposed to solve the abovementioned problems. With the proposed method, projection speed can switch to tens of K frames/s because it only has two grayscale values (0 and 255). A standard sinusoidal color-code fringe can be generated by properly defocusing the binary color-code fringe, thereby overcoming the influence of nonlinear gamma and ultimately improving measurement accuracy. Experiment results verify the feasibility and superiority of the proposed method
Simultaneous measurement of magnetic field and temperature based on magnetic fluid-clad long period fiber grating
Full text linkSimultaneous measurement of magnetic field and temperature is proposed and experimentalized with a magnetic fluid-clad long period fibergrating structure. Magnetic fluid is used as the surrounding material of the long period fiber grating. Both of the wavelength and intensityof the spectral resonance valley of the proposed structure can be influenced by the applied magnetic field and ambient temperaturevariation. A two-parameter matrix method is proposed and utilized to measure the magnetic field and temperature simultaneously. Thelinear relationship between the corresponding wavelength shift/intensity variation and magnetic field/temperature change is obtained atcertain ranges of magnetic field and temperature, which is favorable for sensing applications
Polarization imaging over sea surface - a method for measurements of Stokes components angular distribution
Full text linkThis article describes a method for determining the angular distribution of light polarization over a roughened surface of the sea. Our method relies on measurements of the Stokes vector elements using a polarization imaging camera that operates using the Division of Focal Plane (DoFP) method. It uses special monochrome CCD array in which the neighbouring cells, instead of recording different colours (red green and blue), are equipped with micropolarizers of four directions (0, 45, 90 and 135 degrees).We combined the camera with a fish-eye lens of Field of View (FoV) > 180 deg. Such a large FoV allowed us to crop out the fragment of the frame along the circular horizon, showing a view covering all directions of the hemisphere. Because of complicated optical design of the fish-eye lens (light refraction on surfaces of parts of the lens) connected to the sensor we checked the accuracy of the measurement system. A method to determine the accuracy of measured polarization is based on comparison of the experimentally obtained rotation matrix with its theoretical form. Such a comparison showed that the maximum error of Stokes vector elements depended on zenith angle and reached as much as 24% for light coming from just above the horizon, but decreased rapidly with decreasing zenith angle to the value of 12% for the angles 10° off the edge of FoV.Moreover we present the preliminary results prepared over rough sea surface. These results include total intensity of light, Degree of Linear Polarization (DoLP) and their standard deviations. The results have been averaged over one thousand frames of a movie. These results indicate that the maximum polarization is observed near the reflection of the sun, and the signal coming from below the surface may be observed at zenith angles far from the vertical direction
Applying the data fusion method to evaluation of the performance of two control signals in monitoring polarization mode dispersion effects in fiber optic links
Full text linkWith increasing distance and bit rate in fiber optic links the effects of polarization mode dispersion (PMD) have been highlighted. Since PMD has a statistical nature, using a control signal that can provide accurate information to dynamically tune a PMD compensator is of great importance. In this paper, we apply the data fusion method with the aim of introducing a method that can be used to evaluate more accurately the performance of control signals before applying them in a PMD compensation system. Firstly, the minimum and average degree of polarization (DOP_min and DOP_ave respectively) as control signals in monitoring differential group delay (DGD) for a system including all-order PMD are calculated. Then, features including the amounts of sensitivity and ambiguity in DGD monitoring are calculated for NRZ data format as DGD to bit time (DGD/T) varies. It is shown that each of the control signals mentioned has both positive and negative features for efficient DGD monitoring. Therefore, in order to evaluate features concurrently and increase reliability, we employ data fusion to fuse features of each control signal, which makes evaluating and predicting the performance of control signals possible, before applying them in a real PMD compensation system. Finally, the reliability of the results obtained from data fusion is tested in a typical PMD compensator
Design and development of Binary Diffractive Germanium Lens by thin film deposition
Full text linkThe design and development of infrared (λ: [8]–[12] µm) binary diffractive germanium lens (BDGL) by two - steps thin film deposition (Physical vapor deposition (PVD) technique) is presented. The optical design of the required elements using the optical design code Zemax, the design of the 4 steps binary surface and its required metallic masks using the programming language Delphi, the procedures of fabrication, and the measurement of the resulting profile, were presented. The comparison between the refractive/diffractive lenses by measuring the minimum resolvable temperature difference (MRTD) shows the advantages of binary diffractive surface
Using dispersion-induced group delay to solve the integer ambiguity problem: a theoretical analysis
Full text linkThis paper describes a novel approach for solving the integer ambiguity problem when the adjacent pulse repetition interval length (APRIL) from a femtosecond optical frequency comb (FOFC) is used as a length scale. This approach is inspired by the two-color method, which indicates that there is a one-to-one relationship between the integer part of the APRIL and the group delay distance between the two different wavelengths. Accordingly, we numerically investigate the possibility of using dispersion-induced group delay to solve the integer ambiguity problem. The results of theoretical analyses and numerical investigations demonstrate the feasibility of the proposed method. Our results should contribute toward the further development of APRIL-based length measurement methods