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Applied Optics

APPLICATIONS-CENTERED RESEARCH IN OPTICS

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Early Posting

Accepted papers to appear in an upcoming issue

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September


One-Shot Depth Acquisition with Random Binary Pattern

  • Qin Li, Fu Li, Guangming Shi, Shan Gao, Ruodai Li, Lili Yang, and Xuemei Xie
  • received 06/19/2014; accepted 09/17/2014; posted 09/17/2014; Doc. ID 214340
  • [full text: PDF (1332) KB)]
  • Abstract: In this paper, we propose a new spatial encoding method which integrates the random binary pattern and the improved phase difference matching method to acquire a dense and precise depth map. The adopted binary pattern can simplify the pattern projecting devices compared with the colorful pattern. The density of speckles in the pattern is periodical and the positions of them are random. Based on thes two properties, we propose an improved phase-difference corresponding method which is divided into two steps: the coarse matching step to estimate the approximate coordinates of pixels in the pattern via analyzing the phase values of the image, and the fine matching step to compensate errors of the coarse matching results and to achieve sub-pixel accuracy. This matching method does not require an extra optimization method with a high computation complexity. In the experiment, we show the effectiveness of the proposed method. We also evaluate this method in actual experiments. The results show the advantages of this method compared with the TOF camera and Kinect.

Keywords (OCIS):

  • (110.6880) Imaging systems : Three-dimensional image acquisition
  • (150.5670) Machine vision : Range finding
  • (150.6910) Machine vision : Three-dimensional sensing

X-ray optics of gold nanoparticles

  • Renat Letfullin, Colin Rice, and Thomas George
  • received 07/01/2014; accepted 09/17/2014; posted 09/18/2014; Doc. ID 215102
  • [full text: PDF (489) KB)]
  • Abstract: Gold nanoparticles have been investigated as contrast agents for traditional X-ray medical procedures, utilizing the strong absorption characteristics of the nanoparticles to enhance the contrast of the detected X-ray image. Here we use the Kramers-Kronig relation for complex atomic scattering factors to find the real and imaginary parts of the index of refraction for the medium composed of single-element materials or compounds in the X-ray range of the spectrum. These complex index of refraction values are then plugged into a Lorenz-Mie theory to calculate the absorption efficiency of various size gold nanoparticles for photon energies in the 1-100 keV range. Since the output from most medical diagnostic X-ray devices follow a wide and filtered spectrum of photon energies, we introduce and compute the effective intensity-absorption-efficiency values for gold nanoparticles of radii varying from 5 to 50 nm, where we use the tungsten anode spectral model interpolating polynomials (TASMIP) model to integrate over all spectral energies generated by typical tungsten anode X-ray tubes with kilovolt potentials ranging from 50 to 150 kVp.

Keywords (OCIS):

  • (160.4760) Materials : Optical properties
  • (170.5180) Medical optics and biotechnology : Photodynamic therapy
  • (340.0340) X-ray optics : X-ray optics
  • (350.4990) Other areas of optics : Particles
  • (160.4236) Materials : Nanomaterials

Inverse Analysis of Light Scattered at a Small Angle for Characterization of a Transparent Dielectric Fiber

  • Grzegorz Swirniak, Grzegorz Glomb, and Janusz Mroczka
  • received 07/08/2014; accepted 09/17/2014; posted 09/18/2014; Doc. ID 216550
  • [full text: PDF (1232) KB)]
  • Abstract: The objective of this paper is to discuss the possibility of non-invasive, optical characterization of a transparent (glass) fiber by means of low-coherent light scattering. It will be shown, that by adjusting the coherence properties of incident light, it is possible to select these specific orders of scattering which are related to diffraction. Discussion will be devoted to both the direct scattering and the inverse problem, where an inference about diameter of a multilayered and transparent fiber is accomplished.

Keywords (OCIS):

  • (060.2270) Fiber optics and optical communications : Fiber characterization
  • (290.3200) Scattering : Inverse scattering
  • (290.5850) Scattering : Scattering, particles
  • (290.2558) Scattering : Forward scattering

Common-path and compact wavefront diagnosis system based on cross grating lateral shearing interferometer

  • Tong Ling, Yongying Yang, Xiumei Yue, Dong Liu, and Yifang Ma
  • received 08/07/2014; accepted 09/17/2014; posted 09/18/2014; Doc. ID 220528
  • [full text: PDF (1118) KB)]
  • Abstract: A common-path and compact wavefront diagnosis system for both continuous and transient wavefronts measurement is proposed based on cross grating lateral shearing interferometer (CGLSI). Derived from the basic CGLSI configuration, this system employs an aplanatic lens to convert the wavefront under test into a convergent beam, which makes it possible for CGLSI to test the wavefront of collimated beams. A geometrical optics model for grating pitch determination and a Fresnel diffraction model for order selection mask design are presented. Then a detailed analysis about the influence of the grating pitch, the distance from the cross grating to the order selection mask and the numerical aperture of the aplanatic lens on the system error is made, and a calibration method is proposed to eliminate the system error. In addition, the differential Zernike polynomials fitting method is introduced for wavefront retrieval. Before our experiment, we have designed several grating pitches and their corresponding order selection mask parameters. In the final comparative experiment with ZYGO interferometer, the wavefront diagnosis system exhibits both high precision and repeatability.

Keywords (OCIS):

  • (050.1950) Diffraction and gratings : Diffraction gratings
  • (120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
  • (120.3180) Instrumentation, measurement, and metrology : Interferometry
  • (120.5050) Instrumentation, measurement, and metrology : Phase measurement

Research on object-plane constraints and hologram expansion in phase retrieval algorithms for CW terahertz inline digital holography reconstruction

  • Jiaqi Hu, Qi Li, and Shanshan Cui
  • received 07/22/2014; accepted 09/16/2014; posted 09/17/2014; Doc. ID 217516
  • [full text: PDF (1503) KB)]
  • Abstract: In terahertz inline digital holography, the zero-order diffraction light and conjugate image cause reconstructed image misty. In this paper, three phase retrieval algorithms with different object-plane constrain are applied to conduct reconstruction under the same near-field diffraction propagation conditions and image-plane constraint. The impacts of different object-plane constraints on terahertz inline digital holographic reconstruction are studied. The results show that it is not suitable for phase retrieval algorithm to impose restriction on the phase when the object is a little complicated in the terahertz inline digital holography. In addition, the effects of zero-padding expansion, boundary replication expansion and apodization operation on reconstructed images are studied. The results indicate that the conjugate image can be eliminated and a better reconstructed image can be obtained by adopting appropriate phase retrieval algorithm after the normalized hologram extending to the minimum area which meets the applicable range of angular spectrum reconstruction algorithm by means of boundary replication.

Keywords (OCIS):

  • (090.1995) Holography : Digital holography
  • (110.6795) Imaging systems : Terahertz imaging

Arrange & Average algorithm for the retrieval of aerosol parameters from multiwavelength HSRL/Raman lidar data

  • Eduard Chemyakin, Detlef Muller, Sharon Burton, Alexei Kolgotin, Chris Hostetler, and Richard Ferrare
  • received 07/18/2014; accepted 09/15/2014; posted 09/16/2014; Doc. ID 213875
  • [full text: PDF (913) KB)]
  • Abstract: We present the results of a feasibility study in which a new, simple, automated and unsupervised algorithm, which we call the Arrange & Average algorithm, is used to infer microphysical parameters (complex refractive index, effective radius, total number, surface-area and volume concentrations) of atmospheric aerosol particles. The algorithm uses backscatter coefficients at 355, 532, and 1064 nm, and extinction coefficients at 355 and 532 nm as input information. Testing of the algorithm is based on synthetic optical data that are computed from prescribed monomodal particle size distributions and complex refractive indices which describe spherical, fine mode pollution particles. We tested the performance of the algorithm for the “3 backscatter (fiβ) + 2 extinction (α)” configuration of a multiwavelength aerosol HSRL or Raman lidar. We investigated the degree to which the microphysical results retrieved by this algorithm depend on the number of input backscatter and extinction coefficients. For example, we tested “3β + 1α”, “2β + 1α”, and “3βfi” lidar configurations. This Arrange & Average algorithm can be used in two ways. First, it can be applied for quick data processing of experimental data acquired with lidar. Fast automated retrievals of microphysical particle properties are needed in view of the enormous amount of data that can be acquired by the NASA Langley Research Center’s airborne “3β + 2α” high-spectral-resolution lidar (HSRL-2). It would prove useful for the growing number of ground-based multiwavelength lidar networks, and it would provide an option for analyzing the vast amount of optical data acquired with a future spaceborne multiwavelength lidar. The second potential application is to improve the microphysical particle characterization with our existing inversion algorithm that uses Tikhonov’s inversion with regularization. This advanced algorithm has recently undergone development to allow automated and unsupervised processing; the Arrange & Average can be used as a pre-classifier to further improve its speed and precision. First tests of the performance of Arrange & Average algorithm are encouraging. We used a set of 48 different monomodal particle size distributions, 4 real parts and 15 imaginary parts of the complex refractive index. All in all we tested 2880 different optical data sets for 0%, 10%, and 20% Gaussian measurement noise (one-standard deviation). In the case of the “3β + 2α” configuration with 10% measurement noise, we retrieve the particle effective radius to within 27% for 1964 (68.2%) of the test optical data sets. Number concentration is obtained to 76%, the surface-area concentration to 16%, and the volume concentration to 30% precision. The “3fiβ” configuration performs significantly poorer. The performance of the “3fiβ + 1α” and “2β + 1α” configurations is intermediate between the “3β + 2α” and the “3βfi”.

Keywords (OCIS):

  • (000.3860) General : Mathematical methods in physics
  • (010.1100) Atmospheric and oceanic optics : Aerosol detection
  • (010.1110) Atmospheric and oceanic optics : Aerosols
  • (010.3640) Atmospheric and oceanic optics : Lidar

Multi-band localized spoof plasmons in closed textured cavities

  • Bingzheng Xu, Zhuo Li, Changqing Gu, Pingping Ning, Liangliang Liu, Zhenyi Niu, and Yongjiu Zhao
  • received 07/14/2014; accepted 09/15/2014; posted 09/16/2014; Doc. ID 216983
  • [full text: PDF (867) KB)]
  • Abstract: In this work, we explore the existence of multi-band localized spoof plasmons (LSPs) in closed textured cavities with multiple groove depths. It is interesting to note that the spoof LSPs in each band resemble those generated by the textured two-dimensional (2D) cavities of the same periodicity with the corresponding single groove depth. And the field distributions and confinement characteristics of the plasmon-like modes in such a corrugated cavity are different with the conventional cavity. Hence, this multiple resonance band structures can find potential applications in the microwave and terahertz frequencies.

Keywords (OCIS):

  • (140.4780) Lasers and laser optics : Optical resonators
  • (240.6680) Optics at surfaces : Surface plasmons
  • (070.5753) Fourier optics and signal processing : Resonators

Application of Sub-Doppler DAVLL to the laser frequency stabilization in atomic cesium

  • Dian-Qiang Su, Teng-Fei Meng, Zhong-Hua Ji, Jin-Peng Yuan, Yan-Ting Zhao, Lian-Tuan Xiao, and Suo-Tang Jia
  • received 07/09/2014; accepted 09/14/2014; posted 09/15/2014; Doc. ID 216461
  • [full text: PDF (864) KB)]
  • Abstract: We achieve laser frequency stabilization by a simple technique based on Sub-Doppler dichroic atomic vapor laser lock (DAVLL) in atomic cesium. The technique that combines saturated absorption spectroscopy (SAS) and Zeeman splitting of hyperfine structure allows us to obtain a modulation-free dispersion-like error signal for frequency stabilization. For the error signal, the dependence of peak-to-peak amplitude and the slope at zero-crossing point on magnetic field is studied by simulation and experiment. Base on the result, we obtain an available Sub-Doppler DAVLL error signal with a high sensitivity to the frequency drift by selecting an appropriate strength of magnetic field. Ultimately, the fluctuation of locked laser frequency is confined below 0.5 MHz in a long term exhibiting an efficient suppression of frequency noise.

Keywords (OCIS):

  • (140.0140) Lasers and laser optics : Lasers and laser optics
  • (300.6260) Spectroscopy : Spectroscopy, diode lasers
  • (140.3425) Lasers and laser optics : Laser stabilization

Calculation of the finesse of an ideal Fabry-Pérot resonator

  • Martin Suter and Peter Dietiker
  • received 08/06/2014; accepted 09/14/2014; posted 09/15/2014; Doc. ID 220398
  • [full text: PDF (474) KB)]
  • Abstract: A new derivation of an exact finesse F for the description of an optical resonator is reported. The finesse is derived using the superposition principle of plane waves in an ideal Fabry-Pérot resonator in combination with the standard definition of the quality factor Q which relates the energy loss of a resonator cycle to the energy stored in the resonator. The derived exact expression of the finesse is compared to equations found in the literature and show that they are based on approximations. The exact finesse is then used to convert an infinite series of Lorentz-functions into the well-known Airy-equation in the case of neglected absorption. The derived expression provides a framework for the discussion of the finesse in terms of decay times, free spectral ranges and resonator line widths. The provided expression for the finesse is valid for any value of the intensity relfectivity and gives insight into the underlying physical principles of resonators.

Keywords (OCIS):

  • (230.5750) Optical devices : Resonators
  • (260.5740) Physical optics : Resonance
  • (300.6360) Spectroscopy : Spectroscopy, laser

Scalable pumping approach for extracting the maximum TEM00 solar laser power

  • Dawei Liang, Joana Almeida, and Cláudia Vistas
  • received 06/12/2014; accepted 09/14/2014; posted 09/15/2014; Doc. ID 214013
  • [full text: PDF (1106) KB)]
  • Abstract: A scalable TEM00 solar laser pumping approach is composed of four pairs of first-stage Fresnel lens-folding mirror collectors, four fused silica secondary concentrators with light guides of rectangular cross-section for radiation homogenization, four hollow two-dimensional compound parabolic concentrators (2D-CPC) for further concentration of uniform radiations from the light guides to a 3 mm diameter, 76 mm length Nd:YAG rod within four V-shaped pumping cavities. An asymmetric resonator ensures an efficient large-mode matching between pump light and oscillating laser light, 59.1W TEM00 laser power is calculated by ZEMAX© and LASCAD© numerical analysis, revealing 20 times improvement in brightness figure of merit.

Keywords (OCIS):

  • (140.0140) Lasers and laser optics : Lasers and laser optics
  • (140.3410) Lasers and laser optics : Laser resonators
  • (140.3530) Lasers and laser optics : Lasers, neodymium
  • (140.5560) Lasers and laser optics : Pumping
  • (350.6050) Other areas of optics : Solar energy
  • (350.6830) Other areas of optics : Thermal lensing

Frequency response and bandwidth in low-NA step-index plastic optical fibers

  • Svetislav Savovic, Branko Drljaca, Milan Kovacevic, Alexandar Djordjevich, Jovan Bajic, Dragan Stupar, and Grzegorz Stepniak
  • received 08/06/2014; accepted 09/12/2014; posted 09/15/2014; Doc. ID 220428
  • [full text: PDF (448) KB)]
  • Abstract: By experimental measurement and from a numerical solution to the time-dependent power flow equation, the frequency response, bandwidth, mode coupling, and mode-dependent attenuation are determined for a low-NA plastic optical fiber. Frequency response and bandwidth are specified as a function of fiber length. Numerical results are verified against experimental measurements. Mode coupling and modal attenuation are found to differ substantially between two fiber varieties of the same type (both low-NA, step-index, plastic), implying their preferential suitability that is application-specific.

Keywords (OCIS):

  • (060.2270) Fiber optics and optical communications : Fiber characterization
  • (060.2300) Fiber optics and optical communications : Fiber measurements
  • (060.2310) Fiber optics and optical communications : Fiber optics

Development of a UV laser-induced fluorescence lidar for monitoring blue-green algae in Lake Suwa

  • Yasunori Saito, Kengo Takano, Fumitoshi Kobayashi, Kazuki Kobayashi, and Ho-Dong Park
  • received 06/05/2014; accepted 09/11/2014; posted 09/12/2014; Doc. ID 213453
  • [full text: PDF (1111) KB)]
  • Abstract: We developed a UV (355-nm) laser-induced fluorescence lidar for monitoring the real-time status of blue-green algae. Since fluorescence spectrum of blue-green algae excited by 355-nm showed the specific fluorescence at 650 nm, the lidar was designed to be able to detect the 650 nm fluorescence as a surveillance method for the algae. The usefulness was confirmed by observation at Lake Suwa over 4 years (2005 to 2008). The detection limit of the LIF lidar was 16.65 mg/L for the blue-green algae, which is the range of concentrations of the safe level set by the WHO.

Keywords (OCIS):

  • (010.3640) Atmospheric and oceanic optics : Lidar
  • (280.0280) Remote sensing and sensors : Remote sensing and sensors
  • (280.3640) Remote sensing and sensors : Lidar
  • (300.2530) Spectroscopy : Fluorescence, laser-induced
  • (010.0280) Atmospheric and oceanic optics : Remote sensing and sensors

Effects of spatio-temporal average processes on the estimation of spectral reflectance in color digital holography using speckle illuminations

  • Hideki Funamizu, Shohei Shimoma, Tomonori Yuasa, and Yoshihisa Aizu
  • received 07/09/2014; accepted 09/11/2014; posted 09/12/2014; Doc. ID 216560
  • [full text: PDF (2794) KB)]
  • Abstract: We present the effects of spatio-temporal average processes on an estimation of spectral reflectance in color digital holography using speckle illuminations. In this technique, speckle fields emitted from a multi-mode fiber are used as both a reference wave and a wavefront illuminating an object. The interference patterns of two coherent waves for three wavelengths are recorded as digital holograms on a CCD camera. Speckle fields are changed by vibrating the multi-mode fiber using a vibrator, and a number of holograms are acquired to average reconstructed images. After performing an average process, which we refer to as a temporal average process in this study, using images reconstructed from multiple holograms, a spatial average process is applied using a smoothing window function. For the estimation of spectral reflectance in reconstructed images, we use the Wiener estimation method. The effects of the average processes on color reproducibility are evaluated by a chromaticity diagram, the root-mean-square error (RMSE), and color differences.

Keywords (OCIS):

  • (100.2000) Image processing : Digital image processing
  • (300.6170) Spectroscopy : Spectra
  • (330.1690) Vision, color, and visual optics : Color
  • (330.1730) Vision, color, and visual optics : Colorimetry
  • (090.1995) Holography : Digital holography

Simplified phase recovery method in temporal speckle pattern interferometry

  • Pablo Etchepareborda, Arturo Bianchetti, Ana Laura Vadnjal, Alejandro Federico, and Guillermo Kaufmann
  • received 08/06/2014; accepted 09/11/2014; posted 09/17/2014; Doc. ID 220496
  • [full text: PDF (768) KB)]
  • Abstract: A simplified method for object phase recovering is implemented in temporal speckle pattern interferometry when the employed interferometer admits the introduction of a temporal carrier and the well known two-beam interferometry equation is verified. The spatio-temporal evolution of the object phase is isolated by modulating the acquired interferometric intensity signals with a known temporal carrier in order to carry out its analysis by using a bivariate empirical mode decomposition framework that avoids the usual application of the Hilbert transform. The advantages and limitations of this technique are analyzed and discussed by comparing with well known phase retrieval methods by means of numerical simulations and experimental data.

Keywords (OCIS):

  • (100.2000) Image processing : Digital image processing
  • (100.3010) Image processing : Image reconstruction techniques
  • (100.5070) Image processing : Phase retrieval
  • (120.6150) Instrumentation, measurement, and metrology : Speckle imaging
  • (120.5475) Instrumentation, measurement, and metrology : Pressure measurement

Surface evaluation and evolution during hydrodynamic effect polishing for quartz glass

  • Wenqiang Peng, Chaoliang Guan, and Shengyi Li
  • received 06/23/2014; accepted 09/11/2014; posted 09/11/2014; Doc. ID 214314
  • [full text: PDF (4505) KB)]
  • Abstract: Hydrodynamic effect polishing (HEP), a non-contact machining process, can realize the processed surface roughness as small as atomic level. To investigate the subsurface structure, the HEP processed quartz glass surface was etched by the hydrofluoric (HF) acid solution. It has been proved that HEP is a polishing method with the ability to process the surface with atomic-level flatness and damage-free surface/subsurface. It has been found the micro plastic scratches on the lap prepolished glass have been obviously exposed when the thin redeposition layer was removed. Then the scratches were gradually removed and surface roughness decreased quickly as the removal depth increased. The surface becomes very smooth and the surface roughness maintains at an atomic level when the subsurface damage has been removed clearly. The experimental results demonstrated that the defects such as the scratches parallel to the rotational axis of the wheel were prior to be removed during the polishing process and then were the defects vertical to the wheel rotational axis.

Keywords (OCIS):

  • (160.2750) Materials : Glass and other amorphous materials
  • (220.0220) Optical design and fabrication : Optical design and fabrication
  • (220.4610) Optical design and fabrication : Optical fabrication
  • (220.5450) Optical design and fabrication : Polishing

Multiwall Carbon Nanotube-Polyvinyl Alcohol based Saturable Absorber In Passively Q-Switched Fiber Laser

  • H. Ahmad, M. F. Ismail, S. N. M. Hassan, F. Ahmad, M. Zulkifli, and S. W. Harun
  • received 07/21/2014; accepted 09/10/2014; posted 09/11/2014; Doc. ID 217211
  • [full text: PDF (802) KB)]
  • Abstract: In this work, we demonstrated compact Q-switched erbium doped fiber laser capable of generating high energy pulses using a newly developed multi-wall carbon nanotube polyvinyl alcohol (PVA) thin film based saturable absorber. Q-switched pulse operation is obtained by sandwiching the thin film between two fiber ferrules forming a saturable absorber. Saturable absorber with 1.25 wt. % of PVA concentration shows a consistency in generating pulsed laser with a good range of tunable repetition rate, shortest pulse width and produce a high pulse energy and peak power. The pulse train generated has a maximum repetition rate of 29.9 kHz with a corresponding pulse width of 3.49 μs as a function of maximum pump power of 32.15 mW. The maximum average output power of the Q-switched fiber laser system is 1.49 mW, which translates to pulse energy of 49.8 nJ. The proposed method of multiwall CNT/PVA thin film fabrication is low in cost and involves uncomplicated processes.

Keywords (OCIS):

  • (060.2410) Fiber optics and optical communications : Fibers, erbium
  • (140.3540) Lasers and laser optics : Lasers, Q-switched
  • (140.3560) Lasers and laser optics : Lasers, ring
  • (140.3538) Lasers and laser optics : Lasers, pulsed
  • (060.3510) Fiber optics and optical communications : Lasers, fiber

(LC2014) Photographic observation of a natural fifth-order rainbow

  • Harald Edens
  • received 07/10/2014; accepted 09/10/2014; posted 09/10/2014; Doc. ID 211166
  • [full text: PDF (6261) KB)]
  • Abstract: A photograph has been obtained of a natural fifth-order (quinary) rainbow. The photograph was acquired on 8 August 2012 with a digital camera and a polarization filter to maximize contrast of the rainbows with the background. The quinary rainbow, together with its first supernumerary, appears in a contrast-enhanced version of the photograph as broad green and blue-violet color bands within Alexander's dark band between the primary and secondary rainbows. The red band of the quinary rainbow is obscured by the much brighter secondary rainbow. A comparison with a numerical simulation using Debye series confirms that the color bands of the quinary rainbow appear at the expected location. The numerical simulation produces a good match with the photograph for a droplet radius of 0.46 mm. The green band of the quinary rainbow is even faintly discernible in the unprocessed photograph, suggesting that under exceptional viewing conditions the green band of the quinary rainbow may be observed visually with the aid of a polarization filter.

Keywords (OCIS):

  • (010.1290) Atmospheric and oceanic optics : Atmospheric optics
  • (010.1310) Atmospheric and oceanic optics : Atmospheric scattering
  • (100.2000) Image processing : Digital image processing
  • (110.5200) Imaging systems : Photography
  • (010.7295) Atmospheric and oceanic optics : Visibility and imaging
  • (010.1690) Atmospheric and oceanic optics : Color

Speckle-insensitive fringe detection method based on Hilbert transform for self-mixing interferometry

  • Antonio Luna Arriaga, Francis Bony, and Thierry Bosch
  • received 07/30/2014; accepted 09/10/2014; posted 09/12/2014; Doc. ID 217631
  • [full text: PDF (1048) KB)]
  • Abstract: A robust phase measurement method to detect self-mixing signals from rough surface targets is addressed. Using the Hilbert transform to create the analytic signal of the monitored optical output power, an accurate instantaneous phase can be extracted without being affected by amplitude variations induced by speckle phenomenon. In case of fringe fading, a running average filter removes the local bias offset improving the calculations. This also allows to observe the phase at dynamic feedback levels within the same calculation, avoiding the need of adding external optical, mechanical or electronic components. This method provides confidence for fringe detection required in subsequent steps to reach sub-wavelength precision of a reconstructed displacement or for velocimetry applications.

Keywords (OCIS):

  • (030.6140) Coherence and statistical optics : Speckle
  • (120.3180) Instrumentation, measurement, and metrology : Interferometry
  • (120.5050) Instrumentation, measurement, and metrology : Phase measurement
  • (280.3420) Remote sensing and sensors : Laser sensors

Local stereo matching with adaptive shape support window based cost aggregation

  • Yafan Xu, Yan Zhao, and Mengqi Ji
  • received 05/01/2014; accepted 09/09/2014; posted 09/10/2014; Doc. ID 210714
  • [full text: PDF (1628) KB)]
  • Abstract: Cost aggregation is the most important step in a local stereo algorithm. In this paper, a novel local stereo matching algorithm with cost aggregation method based on Adaptive Shape Support Window (ASSW) is proposed. Firstly we compute the initial cost volume, which uses both absolute intensity difference and gradient similarity to measure dissimilarity. Secondly we apply ASSW based cost aggregation method to get the aggregated cost within the support window. There are two main steps: At first we construct a local support skeleton anchored each pixel with four varying arm lengths decided on color similarity, as a result, the support window integral of multiple horizontal segments spanned by pixels in the vertical neighboring is established; then we utilizes extended implementation of guided filter to aggregate cost volume within the ASSW, which has better edge-preserving smoothing property than bilateral filter independent of the filtering kernel size. In this way, the number of bad pixels locating in the incorrect depth regions can be effectively reduced through finding optimal support window with an arbitrary shape and size adaptively. Finally, the initial disparity value of each pixel is selected using WTA optimization, and post processing about symmetrically considering both the reference and the target image is adopted. The experimental results demonstrate that the proposed algorithm achieves more outstanding matching performance compared with other existing local algorithms on the Middlebury stereo benchmark, especially in depth discontinuities and piecewise smooth regions.

Keywords (OCIS):

  • (120.2440) Instrumentation, measurement, and metrology : Filters
  • (150.0150) Machine vision : Machine vision
  • (150.1135) Machine vision : Algorithms
  • (110.3010) Imaging systems : Image reconstruction techniques

Enhancement of fluorescence molecular tomography with structural-prior-based diffuse optical tomography: combating optical background uncertainty

  • Linhui Wu, Huijuan Zhao, Xin Wang, xi Yi, Weiting Chen, and Feng Gao
  • received 05/21/2014; accepted 09/09/2014; posted 09/10/2014; Doc. ID 211901
  • [full text: PDF (1568) KB)]
  • Abstract: The common approach in fluorescence molecular tomography (FMT) assumes homogeneous distributions of the optical properties and normally results in reconstructions of low sensitivity. A natural enhancement is to incorporate diffuse optical tomography (DOT) to FMT. However, the traditional pixel-based DOT has been a severely ill-posed inverse problem and cannot retrieve the optical property distributions accurately. We present a structural-prior-based DOT method to effectively acquire the heterogeneous optical background with the aid of some imperfect structural priors from X-ray computed tomography (CT) and/or magnetic resonance imaging (MRI) anatomical imaging modalities, and quantitatively compare its hard- and soft-prior schemes for achieving an improved recovery of the fluorescence distribution. Numerical simulations are conducted on a region-labeled three-dimensional (3-D) digital mouse model to investigate the performance of this method. Physical experiments on a cylindrical phantom are also conducted to assess this methodology. Our simulated and experimental reconstruction results indicate that the structural-prior-based DOT guided FMT approach can significantly improve the sensitivity of FMT reconstruction, as well as its imaging resolution and quantitative accuracy.

Keywords (OCIS):

  • (170.0170) Medical optics and biotechnology : Medical optics and biotechnology
  • (170.3010) Medical optics and biotechnology : Image reconstruction techniques
  • (170.3660) Medical optics and biotechnology : Light propagation in tissues
  • (170.6960) Medical optics and biotechnology : Tomography

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