With many others, I was sitting around on 21 December waiting for the world to end according to the prediction about the end of the Mayan calendar. I went in to work, signed some time cards, passed out some Christmas gifts to people in my division office, and left early to pick up my kids (the 14-year-old triplets). I picked them up around 2 p.m. and started the long drive to the small town of Sylvania outside Savannah, Georgia, to spend Christmas with my family. This town is in a county of roughly 5000 people, and spending a few days there is like stepping back in time 50 years. We arrived at 11 p.m., so the nine-hour drive gave me plenty of time to think about how the world was going to end. My triplets gave me many accounts of how they thought it would end, such as a meteor hitting the earth right on Interstate 95, or global warming causing the atmosphere to trigger a sudden and immediate toxic reaction in the air that humans could not survive. They were much more creative than I was since I thought maybe the sun would just explode taking out the Earth in missile-like chunks. It was a good end-of-the-world driving party.

We propose a novel, low-cost bidirectional optical subassembly (BOSA) that uses a single glass-sealed conventional transistor-outline (TO)-CAN package for passive optical network application. In this BOSA, optical transmitting and receiving functions are incorporated into a silicon optical bench and in a TO-CAN package, respectively. With these features, the optical and electrical crosstalk is efficiently suppressed. The single TO-CAN BOSA has an extinction ratio of 11.69 dB and output power of 2.93 dBm for 1.25  Gb/s operation. The penalty of optical dispersion is 1.2 dB after 20-km single-mode fiber transmission. The receiver sensitivity is less than −30  dBm at a bit error rate of 10−3 for 10.3  Gb/s operation and the signal crosstalk penalty of a single TO-CAN BOSA is 0.8 dB.

We report our research on the development of a gas detection system for environmental application. The CO2 concentration of a remote site is detected with near-infrared laser spectroscopy. Light from a thermal-tuning DFB laser, whose wavelength is close to 1.57 μm, is delivered to/from the remote gas cell via silica optical fiber. The low transmission attenuation of 0.2  dB/km promises long distance CO2 sensing in the length of the gas cell in our experiment is 20 cm only, and detection accuracy of CO2 is 1%.

We propose a deterministic figuring method for fabricating high-precision optical surfaces by combining ion beam material adding (IBA) and material removal [ion beam figuring (IBF)] technology. The IBA is first utilized to improve the accuracy and quality of the optical surface by deterministically adding material to the local pits, and then the IBF is applied to further improve the surface accuracy through removing the local protuberances. Compared with current IBF technology, this combined method can realize the uniform convergence of the surface errors and simultaneously increase the convergence rate of the figuring process.

A review paper was previously published on infrared zoom lenses in the 1980s. Subsequently, a paper was published on infrared zoom lenses in the 1990s. It is timely then to prepare a paper on developments and trends in infrared zoom lenses in the decade since the year 2000. These trends include the shift from scanning systems to charge-coupled device and focal plane arrays, dual-band systems, advances in simulators for target detection, high zoom magnification ratio, off-axis as well as on-axis reflective zoom systems, athermalization, and developments and trends in infrared materials. Examples are presented to illustrate each of these trends. These examples are predominantly mechanically compensated zoom lenses, although one optically compensated zoom lens is also included.

In some circumstances, there is a need for a midwave infrared (MWIR) zoom system with a large zoom ratio. Using traditional four-component mechanically compensated types of MWIR zoom systems cannot achieve a large zoom ratio. To meet this demand, we describe a six-component mechanically compensated type. The thin-lens theory of this type is developed and equations are presented. Using the six-component mechanically compensated type, a MWIR continuous zoom system with a zoom ratio of 45 is designed, and it has high image quality over the entire zoom range.

At present, there are mainly three x-ray imaging modalities for dental clinical diagnosis: radiography, panorama and computed tomography (CT). We develop a new x-ray digital intra-oral tomosynthesis (IDT) system for quasi-three-dimensional dental imaging which can be seen as an intermediate modality between traditional radiography and CT. In addition to normal x-ray tube and digital sensor used in intra-oral radiography, IDT has a specially designed mechanical device to complete the tomosynthesis data acquisition. During the scanning, the measurement geometry is such that the sensor is stationary inside the patient’s mouth and the x-ray tube moves along an arc trajectory with respect to the intra-oral sensor. Therefore, the projection geometry can be obtained without any other reference objects, which makes it be easily accepted in clinical applications. We also present a compressed sensing-based iterative reconstruction algorithm for this kind of intra-oral tomosynthesis. Finally, simulation and experiment were both carried out to evaluate this intra-oral imaging modality and algorithm. The results show that IDT has its potentiality to become a new tool for dental clinical diagnosis.

We optimized the configuration of a hollow-fiber gas cell used in a Fourier-transform infrared spectroscopy system for quantitative analyses of low-concentration gas components with small sample volume. Numerical calculation shows that the signal-to-noise ratio (SNR) of this measurement system is maximized in a condition dependent on a fiber’s bore size and length, transmission loss of the fiber, and absorption coefficient of the objective gas component. From the design calculation, a hollow optical fiber with a large diameter of 2 mm was chosen, and a measurement system was constructed with the fiber. In analyses of measured absorption spectra, evaluation of the total area of multiple peaks with different rotation levels enables precise evaluation of gas components with high SNR. Experimental results with sample gases containing nitric oxide showed that a minimum detection limit <1  ppm is obtained owing to gas-cell optimization and numerical procedures.

Structured light stripe systems are widely used in industrial applications for acquiring three-dimensional (3-D) information. Calibration is the first necessary step and traditional algorithms compute the 4×3 transformation matrix from image to world. Therefore, 3-D information can be obtained with respect to the camera’s coordinate system, and it cannot be transformed into the laser coordinate system. We propose a new calibration algorithm of a structured light system that can compute the relative pose of the laser coordinate system with respect to the camera coordinate system. We can convert 3-D information either to the laser coordinate system or to the camera coordinate system. The proposed algorithm uses two planes where one plane with multiple slits is set perpendicular to the other plane. We can easily compute the position and rotation of the laser coordinate system using proposed calibration structure. Also, we can solve the extrinsic calibration using just one shot of an image while conventional algorithms require more than two images under different poses. Experiments under various configurations show the feasibility of proposed algorithm.

In this paper, an accurate method is proposed for wavelength calibration in grating spectrometers. The analytical calibration model of the Czerny–Turner optical system, which describes the relationship between the wavelengths and the pixel numbers with function of the system parameters, is established on the basis of the grating equation and geometric optics. An optimization fitting algorithm is introduced to calculate the practical system parameter values in this model. Experimental tests are conducted in our manufactured spectrometer. The results show that this method has higher calibration accuracy in a broadband spectrometer system and less dependence on the spectral lines chosen compared to the traditional polynomial method. This novel wavelength calibration method also can be applied to other plane-grating or concave-grating spectrometers.

For the existing monocular vision methods of pose (or position and orientation) measurement based on the Perspective-n-Point problem, camera calibrations and image corrections are complicated and difficult due to the lens distortion. Additionally, as their theoretical models, the pinhole imaging model and the collinear equation only offer an ideal approximation for the imaging process of the area array camera. Thus, the measurement possesses inevitable systematic errors. To avoid these problems, a new pose measuring method is proposed, which replaces the area array camera and its collinear equation with two line array cameras and their incident light plane equations, respectively. For these two line array cameras, their mechanical assembly requirements and calibration steps are also analysed; they only require that the two optical centre lines of their cylindrical lenses be perpendicular to each other, and only need to be calibrated for the relationship between the coordinate of the image line and the incident angle of the incident light plane. The experiment results of P4P pose measurement with the proposed method showed only significant random errors and no significant systematic error, confirming that this method has eliminated the problems caused by the image distortion and model approximation.

Phase-shifting profilometry combining with the two-frequency temporal phase unwrapping is widely used for high-speed, real-time acquisition of three-dimensional shapes. However, when the object is not motionless during the acquisition process, some unreliable results may emerge, especially around the contours of the measured object. The main reason for this is that the same point in the projected pattern sequence can map to different points within the camera images resulting from depth changes over time. We present a novel approach for identifying those invalid pixels affected by such an error. By carefully examining the captured fringe pattern, comparing two modulation maps, utilizing the phase relationship between two neighboring pixels, and employing a Gaussian filter to detect the protruding points, the bad measurement pixels can be detected and filtered out effectively. The whole procedure is of low computational complexity because of the introduced lookup table-based fast data processing method. Some experimental results are presented to verify the validity of our method.

To increase the sensitivity of uncooled thermal sensors in the terahertz (THz) spectral range (1 to 10 THz), we investigated thin metamaterial layers exhibiting resonant absorption in this region. These metamaterial films are comprised of periodic arrays of aluminum (Al) squares and an Al ground plane separated by a thin silicon-rich silicon oxide (SiO_x) dielectric film. These standard MEMS materials are also suitable for fabrication of bi-material and microbolometer thermal sensors. Using SiO_x instead of SiO₂ reduced the residual stress of the metamaterial film. Finite element simulations were performed to establish the design criteria for very thin films with high absorption and spectral tunability. Single-band structures with varying SiO_x thicknesses, square size, and periodicity were fabricated and found to absorb nearly 100% at the designed frequencies between three and eight THz. Multiband absorbing structures were fabricated with two or three distinct peaks or a single-broad absorption band. Experimental results indicate that is possible to design very efficient thin THz absorbing films to match specific applications.

Al_0.5Ga_0.5As/GaAs/Al_0.2Ga_0.8As multiple asymmetric quantum well (AQW) have been investigated based on optical difference frequency in the 9 to 11 μm region. Under an intense resonant excitation from a dual-wavelength CO₂ laser, the saturation intensity of intersubband absorption for pump waves is estimated to be 0.3  MW/cm². As the well width variation, the position of absorption peak for pump waves and the absorption of terahertz (THz) wave by DFG show concomitant changes. For an AQW of 7 nm deep well-width and 27 nm total well-width, the maximum of absorption for the THz wave is 6.01×10⁵  m⁻¹ when the two pump wavelengths are 9.69 and 10.64 μm, respectively. These manipulative transitions in AQW can be applied to tunable optical semiconductor devices and implemented in THz wave devices to achieve additional functionalities.

High-frequency response properties of single and double-quantum-well resonant tunneling diodes (RTD) are examined in a wide frequency range, up to terahertz (THz) frequencies, on the base of proposed quantum theory. Numerical solutions of time-dependent Schrödinger equations with open-system boundary conditions in an external electromagnetic field are performed. The numerical solutions take into account the influence of bias DC voltage on electronic states in RTD with finite height and width of barriers both for monoenergetic and for Fermi-distributed electrons in emitter and collector parts of structures. We show that the presence of an additional level in double-quantum-well structures breaks the response symmetry and leads to selective narrow-band frequency amplification, as well as to the effect of amplification frequency tuning at THz frequencies by variation of applied bias voltage. These phenomena predict an increase of gain coefficient and open new perspectives for engineering of novel types of THz oscillators and other high-frequency units.

Subsequent to its publication in Optical Engineering, SPIE learned that a significant portion of this paper was previously published as “Harmful Proton Radiation Damage and Induced Bit Error Effects on the Performance of Avalanche Photodiode Devices,” in International Journal of Multidisciplinary Sciences and Engineering, Vol. 2, No. 4 (July 2011). Double publication violates SPIE Code of Ethics and consequently the paper has been removed from Optical Engineering by the publisher.The Authors

A new high birefringence terahertz photonic crystal fiber is proposed. The properties of birefringence, confinement loss, and chromatic dispersion are studied by using full-vector finite-element methods with an anisotropic perfectly matched layers absorption boundary condition. The cladding contains several periodically arranged diamond-shaped units, which consists of four elliptical air holes with uniform parameters. The fiber core is formed by employing a solid unit without elliptical air holes in the center of the cross-section. Through adjusting the structural parameters of the photonic crystal fiber, we can achieve birefringence up to 10⁻³ from 180 to 400 μm. The confinement loss can decrease to 10⁻⁹  dB/m at 100 μm. The chromatic dispersion coefficient D_wis near to 0±1.0  ps/(nm km) from 100 to 400 μm.

The coherent addition of multiple beams is one of the great challenges in terms of large-scale lasers. Implementing the capability to generate ultra-high-focus power intensity on the focal plane places stringent requirements on the control of each beam’s pointing and intra-beam phasing. The random beam-to-beam phase jumps, mainly induced by the catoptric elements’ rapid vibration, should be eliminated to realize phase locking. A two-way laser beam’s coherent combination test bed is designed to test the capabilities of phase-locking system. The results show that the closed-loop feedback system achieved a high contrast of the in-phase intensity pattern at the receiving plane after correcting for piston and tip/tilt errors between two adjacent laser beams by the stochastic parallel gradient descent algorithm.

We describe a method of generating physical random numbers by means of a diode laser that has an extremely wide-band frequency-noise profile. Fluctuations in the laser frequency affect the intensity of the light transmitted through the optical frequency discriminator, detected thereafter as random fluctuations. This allows us to simultaneously generate 8 random bit streams, due to the parallel processing of 8-digit binary numbers sampled by an 8-bit analog-to-digital converter. Finally, we generated physical random numbers at a rate of 3  Gbit/s, by combining one data stream with another stream that is delayed by 2 ms, by exclusive-OR.

We propose and demonstrate a technique for monitoring the recovery deformation of the shape-memory polymers (SMP) using a surface-attached fiber Bragg grating (FBG) as a vector-bending sensor. The proposed sensing scheme could monitor the pure bending deformation for the SMP sample. When the SMP sample undergoes concave or convex bending, the resonance wavelength of the FBG will have red-shift or blue-shift according to the tensile or compressive stress gradient along the FBG. As the results show, the bending sensitivity is around 4.07  nm/cm −1 . The experimental results clearly indicate that the deformation of such an SMP sample can be effectively monitored by the attached FBG not just for the bending curvature but also the bending direction.

We present a novel light leaking optical fiber liquid level sensor for aircraft fuel measuring systems that is based on the side-emitting optical fiber. In operation, the fiber is bent as a spiral and inserted into the liquid, then the conducting light in the fiber will be scattered and transformed to be cladding mode and radiation mode. The radiation mode power in the scattering light is determined by the ambient refractive index. Since more power is lost in liquids than in the air, the output power of the sensor will monotonically decrease while the liquid level increases. The fiber is bent as a spiral to increase the sensor’s sensitivity. A laboratory prototype with a range of 1 m, a radius of 14 mm, and a screw pitch of 15 mm has been built and successfully demonstrated in water level measurement. The sensor’s response to liquid level is presented and shown to be consistent with the theory.

A fiber Bragg grating (FBG) soil-pressure sensor based on dual L-shaped levers is proposed and demonstrated. Using dual L-shaped levers, the deformation of the diaphragm, which experiences the soil pressure, will be transferred to the longitudinal strain of the FBG. The theoretical analysis on the sensitivity of the proposed sensor is given. The sensor has been calibrated in the laboratory. Experimental results show a good agreement with theoretical expectations. Furthermore, this soil-pressure sensor has been installed in an earth dam in Beijing, China. Drifting of the FBG wavelength has been collected in rainy days from May to July 2012. It has been found that the earth dam has an obvious change of internal stress in the rainstorm.

We report a reflection-based phase-shifted long period fiber grating (PS-LPFG) and demonstrate its capability for simultaneous measurement of temperature and external reflective index (RI). The sensor device comprises a grating directly written by CO2 laser and silver-coated end face. A π-shifted LPFG is presented with two attenuation bands through its reflection spectrum. These two bands have different sensitivity towards temperature and external RI that can be used for simultaneous measurement of the two variables. The experimental results show that this probe-type PS-LPFG performs well in terms of linearity and sensitivity.

In this paper, the surface plasmon resonance sensor, for measuring the absorptive sample’s real part of the refractive index, is studied via numerical simulations. Based on the Kretschmann optical arrangement, wavelength, angular, intensity, and phase interrogations are analyzed by using the Fresnel equation. The results show that, in comparison to the detection of transparent samples, the sensitivity of the wavelength interrogation, angle interrogation, and intensity interrogation improves, changes little, and decreases, respectively. For the absorptive sample, who has a complex refractive index’s imaginary part of 0.01, the sensitivity of wavelength interrogation enhances three times, whereas, that of intensity and phase interrogation reduce to 1/2 and 1/7, respectively. Fortunately, the degradation of the sensitivity, for phase interrogation, can be improved by changing the thickness of the gold film. In addition, the stronger the absorption is, the thinner the optimized thickness. By contrast, it can be found that the phase interrogation, with optimal thickness of gold film, has the highest resolution with the smallest linear measurement range. In order to balance resolution and linear measurement range, the angular interrogation is a better choice.

A novel matching algorithm is presented that can identify stars using raw images of the sky obtained from a CMOS color filter array detector. The algorithm combines geometric information with amplitude ratios calculated from the red, green, and blue color color channels. Conventional algorithms that match stars based solely on inter-star geometry (and sometimes relative brightness), typically require three or more stars for a confident star match. In contrast, the presented algorithms are able to find matches with only two imaged stars in most regions of the sky. The necessary catalog preparation and a simple star-pair matching algorithm based on combined color intensity ratios and the angular spacing are discussed. Results from a large set of simulation trials and initial results from sensor field testing are presented.

Wavelength-division-multiplexing passive optical network (WDM-PON) has been considered as a promising next generation access network solution. A centralized light-wave colorless WDM-PON architecture based on a single feeder fiber. At the optical line terminal, differential quadrature phase shift keying (DQPSK) modulated signal at 10 Gbps is utilized for downstream transmission is proposed and demonstrated. At the optical line unit, part of the downstream signal is remodulated using an intensity modulated on/off keying technique for upstream transmission. Simulation results show that downstream and upstream signals achieved error-free transmission at 10-Gbps symmetric data rate with negligible power penalties. The proposed scheme exhibit improved tolerance to Rayleigh backscattering over 20 km standard single mode fiber.

We show an analytical and numerical study of dispersive wave (DW) frequency generated by solitons in birefringent fiber optics. We propose some analytical approximations for finding the DW frequency that agrees with numerical results for small normalized third-order dispersion. We also show that a scalar DW frequency equation is not valid for all birefringent optical fiber cases.

We propose and demonstrate a full-duplex dense wavelength division multiplexing (DWDM) radio over fiber (ROF) system transmitting multibands wired and wireless orthogonal frequency division multiplexing (OFDM) signals. In a central station, an optical signal noise ratio (OSNR)-boosted multicarriers generator based on recirculation frequency shifter (RFS) is used to generate multicarriers. Sixty-six frequency-lock and coherent, 25 GHz frequency-spacing subcarriers with OSNR larger than 26 dB with an amplitude difference of 5 dB are generated and used to transmit downstream data. Since these subcarriers are coherent with each other, n-fold frequency optical millimeter-wave signals can be generated. Without using costly W-band components, a 20 Gbps downstream transmission operation at 75 GHz is experimentally validated. The power penalty of less than 3 dB was observed after a 50-km single mode fiber (SMF) and 4-m wireless transmission. In order to realize the full duplex system, a 1.2 GHz bandwidth reflective semiconductor optical amplifier (RSOA) is used to achieve 5 Gbps upstream traffic for 16QAM-OFDM signals. The measured power penalty of 3 dB is observed after a 50-km SMF transmission at the bit error rate of 3.8×10 −3 .

To mitigate the impact of the error between the estimated channel fading coefficient and the perfect fading coefficient on the bit error rate (BER), a priori conditional probability density function averaging the estimation error is proposed. Then, an improved maximum-likelihood (ML) symbol-by-symbol detection is derived for the free-space optical communication systems, which implement pilot symbol assisted modulation. To reduce complexity, a closed-form suboptimal improved ML detection is deduced using distribution approximation. Numerical results confirm that BER performance improvement can be reached by the improved ML detection, and that its suboptimal version performs as well as it does. Therefore, they both outperform classical ML detection, which doses not consider channel estimation error.

Twin-core fiber (TCF) can provide the required spectral response for implementing an optical temporal differentiator. It is shown that the output temporal waveform from one core of the TCF providing full energy coupling is proportional to the first derivative of the optical temporal signal launched at the input. Moreover, TCF can also be used as the first order optical temporal differentiator for multiwavelength optical signals, in which the position and the number of central wavelength can be tunable simply by changing the fiber length. Our numerical results confirmed that the TCF has a good accuracy by calculating the first time derivatives of the input optical signals with temporal features in the picosecond and subpicosecond ranges.

The cyclic period and free spectral range of arrayed-waveguide gratings (AWG) in a wavelength-division multiplexing/optical code division multiple access optical code division multiple access network are exploited. The total optical network unit (ONU) of network capacity is partitioned into groups of different wavelength in accordance with the geographical location of subscribers based on the radial distance of the ONU to the optical line terminal. Combining concentric circles round by round for ONU groups enables a fixed round-trip time in the data transmission and a significant increase in system performance. Using AWG router, the proposed topology of concentric circles retains signature orthogonality and minimizes wavelength collisions on the photo-detector. Furthermore, the adoption of extended M-sequence codes corresponding to the AWG codec provides a simpler, more efficient coding procedure and accommodates more users in a single group.

We perform theoretical analysis of dispersive waves generated by soliton in birefringent photonic crystal fibers. With Lagrangian formulation and Stokes parameters, we study the state of polarization of solitons under various levels of birefringence and third order dispersion. Then we investigate numerically the variation of dispersive wave frequency for different initial polarization angles and further consider the effect of stimulated Raman scattering.

The increase of multimedia applications results in the growing popularity of multicast demands. At the same time, survivability in an optical network is very important because of its very high transmission rate. Therefore, it is necessary to provide survivability for multicast demands in an optical network. Previous works have proposed multicast protection schemes for single-fiber link failure, in which the preconfigured protection cycle, known as the p-cycle, is an efficient method to overcome the long restoration time and the complicated protection switching procedure in comparison with other schemes. However, most previous schemes are applied only to static multicast protection. Although some schemes are extended to dynamic multicast protection, they do not consider the protection for straddle links. To overcome the shortcoming, this paper improves the existing p-cycle-based dynamic multicast protection and proposes an enhanced intelligent p-cycle (EIpC) scheme, in which all working light-trees of multicast demands can be protected by a p-cycle in the network. For each multicast demand, EIpC can compute a set of high-efficient p-cycle to provide dynamic protection. By combining the existing p-cycle for meeting certain conditions, EIpC can reduce the wavelength usage of p-cycle. Simulation results show that EIpC can obtain performance improvement compared to conventional schemes.

We experimentally investigate the effect of pilot power allocation on the performance of baseband direct-detected optical orthogonal frequency division multiplexing system by comparing five pilot power allocation schemes. The results show that the scheme of increased pilot power allocation had the highest receiver sensitivity and frequency fading tolerance of all. Allocating more power on pilots at higher frequencies can improve the accuracy of channel estimation which leads to a better system performance.

The implementation of a novel continuously tunable bandpass filter based on liquid-filled photonic crystal fibers is reported. The filter function is based on the tunable overlapping bandgaps of two photonic crystal fibers resulting from the thermo-optic effect of the filled liquid. The center wavelength and the width of the filter can be easily designed by selecting the refractive indexes of the filled liquid, and the width of the transmission bands can be continuously widened or narrowed by heating different liquid-filled parts.

A combination method to study the drying process of paints, based on digital holography and gravimetric measurement, is proposed. The proposed method allows taking holographic measurement in a simultaneous way to compare the results obtained by the reconstructed image changes with gravimetric data. By directly comparing a phase change in the reconstructed images of a paint surface and weight change of the paint film, it is found that a stationary state of the paint surface detected by the phase change occurs in the last stage of solvent evaporation and corresponds to a dry-hard of the paint film. The proposed technique can also analyze dryness of clear coat having no scattering particle using the phase change. It is shown that the present technique can allow us to further investigate not only a film formation of clear coat but also an estimation of specific gravity of solvents by comparing directly the phase change with weight loss due to solvent evaporation in the simultaneous measurement.

We present a novel approach that utilizes both physical tiling and optical scan-tiling of high-speed electrically addressed spatial light modulator (SLM) for increasing the pixel count of hologram. Twenty-four SXGA (1280×1080) high-speed ferroelectric liquid crystal on silicon are first physically tiled to form an 8(rows)×3(columns) SLM array. This array is further tiled to form a final hologram with pixel count of 377.5 Megapixels through a 1-axis galvanometric scanning mirror. A large computer-generated hologram is calculated and fed into the individual SLMs according to the predefined sequence. Full-color and full-parallax flickless three-dimensional objects are replayed at a rate of 60 frames per second in a 10-in. display window. The launching of the hologram, laser illumination, and scanning mirror are synchronized and controlled by a field-programmable gate array.

We describe and evaluate a practical approach for implementing computer-generated-holography (CGH) using multiple graphic processing units (GPUs). The proposed method can generate high-definition (HD) resolution (1920×1080) digital holograms in real-time. In order to demonstrate the plausibility of our method, some experimental results will be given. First, we discuss the advantage of GPUs for CGH against central processing units (CPUs) by comparing the performance of both. Our results show that use of GPUs can shorten CGH computation time by 2791 times. Then, we discuss the potential of multiple GPUs for generating HD resolution digital holograms in real-time by measuring and analyzing the CGH computational time in accordance with the number of GPUs. Our result shows that the CGH computational time decreases nonlinearly, with a logarithmic-like curve, as the number of GPU increases. Therefore, we can determine the number of GPUs to maximize the efficiency. Consequently, our implementation can generate HD resolution digital holograms at a rate of more than 66 hps (holograms-per-second) using two NVIDIA GTX 590 cards.

To solve the local optimum problem, a modified hill-climbing algorithm based on Zernike modes is presented for wavefront sensorless adaptive optics. This algorithm adopts the Zernike mode coefficients, instead of the actuators’ voltages in a traditional hill-climbing algorithm, as the adjustable variables to optimize the object function. First, the principle of the algorithm is described. Then the efficiency of the modified and traditional hill-climbing algorithms are analyzed numerically and experimentally using a He-Ne laser beam shaping system with a 37-element unimorph deformable mirror. The results of both simulations and experiments demonstrate that the modified hill-climbing algorithm can eliminate the local optimum problem with a fast speed of about 100 iterations.

This paper presents a low-cost silicon unimorph deformable mirror (DM) that will be used for astronomical adaptive optics. The device has a simple construction consisting of a 400-μm-thick silicon wafer and a 200-μm-thick lead zirconate titanate film, with 214 actuators and 50-mm active aperture. The actuator displacement of the fabricated device is about 1 μm at 50 V. And the resonance frequency is 550 Hz. The simulation and experimental generation of Zernike mode shapes indicate that the fabricated DM has an excellent correction performance for both low order and high order aberrations.

A new technique for image fusion based on nonsubsampled shearlet transform (NSST) and improved pulse-coupled neural network (PCNN) is proposed. NSST, as a novel multiscale geometric analysis tool, can be optimally efficient in representing images and capturing the geometric features of multidimensional data. As a result, NSST is introduced into the area of image fusion to complete the decompositions of source images in any scale and any direction. Then the basic PCNN model is improved to be improved PCNN (IPCNN), which is more concise and more effective. IPCNN adopts the contrast of each pixel in images as the linking strength β , and the time matrix T of subimages can be obtained via the synchronous pulse-burst property. By using IPCNN, the fused subimages can be achieved. Finally, the final fused image can be obtained by using inverse NSST. The numerical experiments demonstrate that the new technique presented in this paper is competitive in the field of image fusion in terms of both fusion performance and computational efficiency.

This paper proposes an efficient four-stage approach that automatically detects fire using video capabilities. In the first stage, an approximate median method is used to detect video frame regions involving motion. In the second stage, a fuzzy c-means-based clustering algorithm is employed to extract candidate regions of fire from all of the movement-containing regions. In the third stage, a gray level co-occurrence matrix is used to extract texture parameters by tracking red-colored objects in the candidate regions. These texture features are, subsequently, used as inputs of a back-propagation neural network to distinguish between fire and nonfire. Experimental results indicate that the proposed four-stage approach outperforms other fire detection algorithms in terms of consistently increasing the accuracy of fire detection in both indoor and outdoor test videos.

According to the characteristic of range images of coherent ladar and the basis of nonlocal means (NLM), a nonlocal probability statistics (NLPS) algorithm is proposed in this paper. The difference is that NLM performs denoising using the mean of the conditional probability distribution function (PDF) while NLPS using the maximum of the marginal PDF. In the algorithm, similar blocks are found out by the operation of block matching and form a group. Pixels in the group are analyzed by probability statistics and the gray value with maximum probability is used as the estimated value of the current pixel. The simulated range images of coherent ladar with different carrier-to-noise ratio and real range image of coherent ladar with 8 gray-scales are denoised by this algorithm, and the results are compared with those of median filter, multitemplate order mean filter, NLM, median nonlocal mean filter and its incorporation of anatomical side information, and unsupervised information-theoretic adaptive filter. The range abnormality noise and Gaussian noise in range image of coherent ladar are effectively suppressed by NLPS.

Visible and infrared video cameras are the most common imaging sensors used for video surveillance systems. Fusing concurrent visible and infrared imageries may further improve the overall detection and tracking performance of a video surveillance system. We performed image fusion using 13 pixel-based image fusion algorithms and examined their effects on the detection and tracking performance of a given target tracker. We identified five fusion methods that produced significantly better performance, three of which also managed to achieve that with a relatively high efficiency.

The dictionary-based super-resolution (SR) method has received much attention in recent years because sparse representation is very effective for image restoration tasks. By sparse representation, original image patches are represented as a sparse linear combination of atoms in an over-complete dictionary. However, the dictionary-based SR approach has some disadvantages in that it produces annoying ringing artifacts, especially along the object boundaries and is not effective in reconstructing images that contain patterns with strong edges. We enhance the dictionary-based SR using nonlocal total variation regularization. In the training stage, we jointly train two dictionaries, D_h and D₁, from the low-resolution (LR) and high-resolution (HR) training image patches by using the K-singular value decomposition (KSVD) algorithm as in conventional methods. In the synthesis stage, we obtain the sparse coefficient vector from the LR test image over the LR dictionary, and reconstruct SR patches using the coefficient vector over the HR dictionary. Then, we employ nonlocal total variation regularization to remove annoying ringing artifacts and recover the patterns with strong edges in images. Experimental results on various test images demonstrate that the proposed method is very effective in enhancing the dictionary-based SR approaches in terms of quantitative performance and visual quality.

We introduce a generalized camera calibration model that is able to determine the camera parameters without requiring perfect rectangular road-lane markings, thus overcoming the limitations of state-of-the-art calibration models. The advantage of the new model is that it can cope in situations where road-lane markings do not form a perfect rectangle, making calibration by trapezoidal patterns or parallelograms possible. The model requires only four reference points—the lane width and the length of the left and right lane markings—to determine the camera parameters. Through real-world surveying experiments, the new model is shown to be effective in defining the 2D/3D transformation (or vice versa) when there is no rectangular pattern on the road, and can also cope with trapezoidal patterns, near-parallelograms, and imperfect rectangles. This development greatly increases the flexibility and generality of traditional camera calibration models.

Gesture recognition is useful for human-computer interaction. The difficulty of gesture recognition is that instances of gestures vary both in motion and shape in three-dimensional (3-D) space. We use depth information generated using Microsoft’s Kinect in order to detect 3-D human body components and apply a threshold model with a conditional random field in order to recognize meaningful gestures using continuous motion information. Body gesture recognition is achieved through a framework consisting of two steps. First, a human subject is described by a set of features, encoding the angular relationship between body components in 3-D space. Second, a feature vector is recognized using a threshold model with a conditional random field. In order to show the performance of the proposed method, we use a public data set, the Microsoft Research Cambridge-12 Kinect gesture database. The experimental results demonstrate that the proposed method can efficiently and effectively recognize body gestures automatically.

A fast mode decision algorithm is proposed to reduce the computation complexity of adaptive inter layer prediction method, which is a motion estimation algorithm for video compression in scalable video coding (SVC) encoder systems. SVC is standard as an extension of H.264/AVC to provide multimedia services within variable transport environments and across various terminal systems. SVC supports an adaptive inter mode prediction, which includes not only the temporal prediction modes with varying block sizes but also inter layer prediction modes based on correlation between the lower layer information and the current layer. To achieve high coding efficiency, a rate distortion optimization technique is employed to select the best coding mode and reference frame for each MB. As a result, the performance gains of SVC come with increased computational complexity. To overcome this problem, we propose fast mode decision based on coded block pattern (CBP) of 16×16 mode and reference block of best CBP. The experimental results in SVC with combined scalability structure show that the proposed algorithm achieves up to an average 61.65% speed up factor in the encoding time with a negligible bit increment and a minimal image quality loss. In addition, experimental results in spatial and quality scalability show that the computational complexity has been reduced about 55.32% and 52.69%, respectively.

A scalable system to achieve large-sized light field three-dimensional display using multi-projectors and directional diffuser is presented. The system mainly employs an array of mini-projectors projecting images onto a special cylindrical directional diffuser screen. The principle of light field reconstruction, configuration of multi-projectors style, and characteristics of directional diffuser are explicitly analyzed, respectively. A prototype of a piece of equipment in mini-cinema class is proposed, with 100 mini-projectors and a special cylindrical directional diffuser performing different diffuse angles in horizontal and vertical directions. Bright and large-sized three-dimensional images displayed by the system can be observed at different horizontal viewing positions around the cylindrical display area with stereo parallax and motion parallax.

Monte Carlo (MC) method is generally used as a “gold standard” technique to simulate photon transport in biomedical optics. However, it is quite time-consuming since abundant photon propagations need to be simulated in order to achieve an accurate result. In the case of complicated geometry, the computation speed is bound up with the calculation of the intersection between the photon transmission path and media boundary. The ray-triangle-based method is often used to calculate the photon-boundary intersection in the shape-based MC simulation for light propagation, but it is still relatively time-consuming. We present a fast way to determine the photon-boundary intersection. Triangle meshes are used to describe the boundary structure. A line segment instead of a ray is used to check if there exists a photon-boundary intersection, as the next location of the photon in light transports is determined by the step size. Results suggest that by simply replacing the conventional ray-triangle-based method with the proposed line segment-triangle-based method, the MC simulation for light propagation in the mouse model can be speeded up by more than 35%.

This article [Opt. Eng.. 51(4 ), 047001 (2012)] was originally published on 6 April 2012 with one of the authors’ names misspelled. Jianping Qiao was mistakenly printed as Qianping Qiao. The paper was corrected online on 9 January 2013.

This article [Opt. Eng.. 52, (1 ), 019001 (2013)] was originally published on 3 January 2013 with Figs. 12–3 out of order. The corrected figures and captions are reprinted below.