For subset-based digital image correlation, the random error of second-order shape function roughly doubles that of first-order shape function, termed doubled random error phenomenon. In this work, we suggest that the fundamental cause of this phenomenon is the uniformity and isotropy of speckle pattern. Specially, we prove that the ratio of random error of second-order shape function to that of first-order

The results obtained during a pile test are dependent on a number of factors. However, conventional monitoring systems like vibrating wire strain gauges and the extensometers can only measure the variations of strain and displacement at discrete locations at which they are installed in a pile. In order to identify the behavior of Continuous Flight Auger (CFA) pile, the distributed fiber optic monitoring

Laser biological tissue welding is a potential alternative technology from traditional suturing skills. In this study, we explored the influence laws of laser scanning path on in-vitro skin tissue performance and designed four different scanning paths, including heartbeat, circle, peano20-2, and toothed paths. Then the influence laws of laser scanning paths on temperature distributions, mechanical

This paper presents a compact design for spectral shearing interferometry to reconstruct an ultrafast electric-field (SPIDER) with a high signal-to-noise ratio (SNR) and stability. Compared experimentally with the traditional SPIDER based on a Michelson interferometer (MI), this design can improve the SNR by a factor of 3.7 in a 25 dB BW region. Using the material dispersions of 6 mm BK7 plates as

When an object with a rough surface is illuminated using a coherent laser, the scattered light rays interfere to create a three-dimensional speckle field that fills the adjacent space. If the object is displaced or tilted, the entire speckle field moves in response. Therefore, the motion of an object can be measured remotely by tracking the movements of the objective speckle pattern recorded on a lensless

Digital holography enables the digitization processing of holograms. The resolution of the reconstructed image is greatly limited by the pixelated imaging detectors. To improve the resolution, a bicubic interpolation and extrapolation iteration (BIPEPI) method is proposed to compensate the limited size of the digital holograms. Based on the prior knowledge of the model of Fresnel zone plate with circular

In this study, a new type of structure of optical fiber pressure sensor (OFPS) based on polarization modulation is proposed, which selects a high-birefringence fiber (HBF) as the sensing unit to measure the pressure in the fluid medium. The PM-1550-01 fiber produced by NTK Photonics Inc. is evaluated as the sample in our subject. Firstly, the regularities of birefringence variation on the PM-1550-01

As an indirect imaging technique, computational ghost imaging (GI) obtains the object information by calculating the intensity correlation between a series of computer-generated matrices and the corresponding bucket signals, which thereby offers a potential application in optical encryption. Here, we propose a new steganography scheme, called ghost steganography, based on the principle of computational

The accurate recovery of an n-Dimensional field from observations that are wrapped into a particular interval (e.g., [−π,π]) is a problematic step in many applications, such as holography, interferometry, optical metrology, magnetic resonance imaging and analog-to-digital conversion in digital photography. While methods designed for this purpose abound (mainly in the 2-Dimensional case), most fail

In this paper, we propose and demonstrate a new 3D imaging technique which can simultaneously provide surface shape, color, and polarization information of an object. The system employs a custom color full Stokes polarization camera and a digital color fringe projector. The color and polarization data provide additional surface details not possible using conventional fringe projection 3D imaging techniques

As the first step in manual or automated preimplantation genetic diagnosis (PGD), accurate locating of the blastomere is essential. In order to further improve success rates of the PGD process, it is necessary to obtain three-dimensional information of the blastomeres. In this study, a practical and effective pipeline that allows conventional brightfield microscopy systems to provide 3D imaging feedback

Photogrammetry-based motion tracking systems are widely used in entertainment, medicine, sports, and other industries for low accuracy positioning applications. Camera-based systems track cooperative markers on objects to obtain their real-time positions and poses. There are few detailed studies in the literature on the metrological performance in three-dimensional (3D) space for such systems since

Intelligent driving is an active area of research in both industry and academia. In order to overcome the shortcomings of traditional machine vision such as visibility is easily affected by illumination conditions, the blind area of infrared small field of view (FOV) is too large and could not provide depth information, this paper proposes a method for detecting significant obstacles based on ultra-wide

Herein we present a generalized algorithm for processing activity images. Existing algorithms are applicable only to particular cases, and a new, broader approach is therefore proposed here that is based on a set of tuneable filters for images, using an extension of the addition and subtraction operations. The choice of tuning parameter is determined based on the desired result in each experimental

We propose a configuration of Fourier ptychographic microscopy (FPM) to modulate the focus to a large extent. FPM is widely used to obtain high-resolution images in a wide field of view. A conjugation mirror with an axially scannable mirror is introduced to conventional FPM to extend the focus range. The proposed FPM provides a wider field of view with higher resolution compared to general microscopy

An automatic detection method of crystal defect positions including interface dislocations and a strain imaging method for an arbitrarily oriented atomic array were developed based on the sampling moiré technique. An automatic defect location detection algorithm was proposed by defining a defect detection coefficient. As an application, a transmission electron microscope (TEM) image of a Ge/Si crystal

Phase-shifting is a powerful phase demodulation method for three-dimensional imaging by fringe projection. However, numerous fringe patterns, which encode a single-phase function, are required. In this paper, the use of intensity patterns, which encode multiple phase functions, is proposed. A multi-demodulation phase-shifting algorithm and the intensity pattern projection profilometry approach are

The ablation of thin metal films using ultrafast laser radiation represents a standard processing procedure in laser technology. However, looking closer to the resulting structures, the arising topology deviates strongly from the expected one. Ablation of thin gold films using ultrafast laser radiation with a Gaussian-shaped spatial intensity distribution results in flat topologies. By synergistically

Phase sensitivity plays a vital role in accurately retrieving three-dimensional (3D) shape of diffused objects in fringe projection profilometry (FPP). With regard to traditional means that simply project horizontal or vertical fringe patterns, the fringe frequency and direction may not be the best choice to acquire optimal sensitivity to depth variations. To overcome this problem, this paper proposes

In this paper, a silhouette-free and crosstalk-free multiple-color-image cryptosystem is presented based on unequal modulus decomposition (UMD) in the gyrator transform (GT) domains. To the best of our knowledge, it is the first time that the use of cascaded GT, UMD, and inverse-GT operations is demonstrated which features four-orders-of-magnitude higher sensitivity relative to the known GT-UMD cryptosystems

Compressed sensing (CS) can recover a signal from a small number of observed transforms of that signal. It mainly consists of two complimentary elements including compressed sampling and computational image reconstruction. In this work, we have developed a ghost imaging system and proposed a primal dual interior point compressed sensing algorithm. We also demonstrated the performance of our imaging

The performance of an all fibered near-infrared laser heterodyne radiometer (NIR-LHR) is demonstrated in ground-based solar occultation mode. A 1 × 2 fiber optical switch is employed as an alternative modulator to traditional chopper, which makes the system more stable and compact. Two distribute feedback (DFB) lasers centered at 1.6 μm and 1.65 μm, are employed as local oscillators to probe absorption

Projection-type multiview holographic three-dimensional (3D) display using a single spatial light modulator (SLM) and a directional diffractive device (DDD) composed of pixelated gratings is able to present 3D scenes with wide viewing angle and significantly reduced data volume. However, there are still several limitations on the display performance, such as finite number of viewpoints and low resolution

Dynamics of low-density channel formed by the radial expulsion of electrons and ions due to the ponderomotive force of the q-Gaussian laser is investigated. Under perturbation approximation, an expression for channel density is derived in order to analyze the depletion of density inside the channel. WKB approximation is employed to study the propagation of q-Gaussian laser in the self-formed channel

This study is directed at developing a micro-scale laser scoring process and understanding the laser-material interaction in ultra-thin aluminium foils (160 μm thickness). The research is carried out by the latest generation of nanosecond pulsed fibre lasers manufactured by SPI Lasers. Presented comparative analysis of 70 W and 120 W laser types gives important insights for laser functionality and

In this paper, a novel absolute measurement method based on multisurface interference is proposed for a 600 mm aperture interferometer. Compared to existing 3-flat testing methods, which generally require two transmission flats and one reflection flat, our method does not require the replacement of the transmission flat with another flat and rotation of the reflection flat about the z-axis of the 600 mm

Because light-field and polarization information contain much information of scenes, light-field and polarization imaging-systems can be used, e.g., for target detection, material classification, and biological analysis. However, most conventional systems rely on scanning or camera arrays, which tend to make the system both bulky and unstable. Here, we investigate a novel approach, snapshot polarimetric–volumetric

The surface optical loss in optical windows is primarily attributed to Fresnel reflection at the interface between air and substrate of high refractive index materials such as zinc sulfide (ZnS). In this study, the concave antireflective subwavelength structures (ASS) on ZnS have been numerically and experimentally investigated to obtain high transmittance over a wide bandwidth in the far-infrared

In this study, a high repetition rate laser ultrasonic system is developed for noncontact detection of silicon wafer crack. A high repetition rate pulse laser is used to generate two narrowband ultrasonic waves on a target silicon wafer, whereas a high-speed laser Doppler vibrometer is used to measure the corresponding ultrasonic responses. Nonlinear interaction occurs between the two generated ultrasonic

Tubular components are indispensable in manufacturing industry, but when its size decreases to micro level, the formability of micro tube will become undesirable. To improve the formability of micro tube, this study suggested a novel laser shock hydroforming method. This method used laser-induced shock wave as energy source and liquid as medium to transmit pressure wave. It was the pressure wave that

The micron-sized metallic droplets have been commonly encountered in the utilization of liquid metallic materials. The size of metal droplet is a critical parameter that needs to be determined. This work goes insight into a dual-beam interferometric particle imaging (DIPI) method, which is proposed for the size measurement of opaque micron-sized metallic droplets. Three typical DIPI configurations

A new superposition based multiple-image encryption using Fresnel-domain high dimension chaotic phase encoding is proposed. In this method, each color image of an authenticated user is decomposed into R, G, and B channels. The amplitude of each channel is independently normalized, phase encoded and then modulated by corresponding high-dimension chaotic random phase mask (HDCPM). The modulated R, G

The fractional-order chaotic systems have characteristics of the all chaotic systems, however, the improper fractional-order chaotic systems have more complexity random sequences, which more suitable for chaotic cryptosystems. To investigate the application of improper fraction order chaotic system in chaotic cryptography, in this paper, an improper fractional-order laser chaotic system is constructed

This paper focuses on solving the diffractive phase retrieval problem of arbitrary complex objects by modulating the object phase. Unlike classical diffraction interferometry such as point-diffraction and phase-shifting interferometry, this method does not require precise location, size, information on the phase shifting area, or direct reference waves. By considering regional division and small area

Owing to their good mechanical properties, titanium based alloys are used for machine parts and devices that operate in demanding regimes and environmental conditions. Laser shock peening (LSP) is an innovative technique for improvement of the surface and mechanical characteristics of the material. In this paper, LSP is employed for additional improvement of already good characteristics of Ti- alloy

Freeform surfaces are widely used in advanced optical systems. In order to accurately measure freeform surfaces, an adaptive interferometer with deformable mirror (DM) has been developed for the freeform surface metrology. To ensure the efficiency, a stochastic parallel gradient descent (SPGD) and Newton iteration mixed algorithm to drive the DM has been proposed, it can achieve the minimum value of

Directly using wrapped phases may cause a problem of phase ambiguity in fringe-projection-based three-dimensional (3D) imaging. In our previous work, the phase ambiguity was addressed by introducing light-field imaging to associate a wrapped phase-encoded field in the image space with several candidates of spatial points in the object space to identify the correct fringe orders for absolute phase unwrapping

Narrow Gap Multi-Layer Welding (NGMLW) using a laser as the main heat source and metal wire for material addition has been a growing topic of interest in the last decade. This is in part due to its potential for joining much thicker sheets of steel than what is usually considered possible when using autogenous laser welding. The process has shown great potential but improvements can still be made,

Phase contrast microscopy enables the label-free visualization of “phase-only” objects such as unstained biological cells. This approach produces a contrast in image intensity that relates qualitatively to the phase delay introduced by the specimen. Quantitative phase imaging refers to an emerging set of methods that naturally extend phase contrast microscopy. These methods enable the quantitative

We developed a collinear reflection Mueller matrix microscope by adding polarization state generator (PSG) and polarization state analyzer (PSA) into the illumination and detection optical paths of a commercial metallurgical microscope. It is found that specific efforts have to be made to reduce the artifacts due to the intrinsic polarizations of the optical system, particularly the dichroism due to

When the terminal position and shape detection properties of a fiber Bragg grating (FBG) curve sensor are used in medicine, the positioning accuracy of the FBG curve sensor is critical in the prediagnosis and treatment of diseases. To improve the shape reconstruction accuracy, two updated reconstruction algorithms are proposed based on the error accumulation of a single-point recursive reconstruction

Laser confocal tomography faces severe challenges in weak signal detection such as biological tissue imaging and low-reflection interfaces measurement. An ultra-high sensitive optical confocal tomography based on laser frequency-shifted feedback imaging technology is presented, whose theoretical magnification can reach 106 notably without using high-gain detectors. In addition, this achievement possesses

Various sensors in Internet of things capture many images, and there is growing concern about their secure storing and sharing. Compressed sensing (CS) is a promising solution for this problem. However, traditional CS-based security frameworks only provide computational secrecy with high reconstruction complexities. In this paper, we propose a low-complexity privacy preserving scheme based on CS and

A distributed fiber optic vibration sensing system with high frequency response and multi-points accurate location is proposed and demonstrated by combining a feedback loop-based interferometer (FLI) and a phase sensitive optical time domain reflectometer (φ-OTDR). The FLI and the φ-OTDR are merged together based on a wavelength division multiplexing (WDM) scheme. Assisted by the feedback loop, the

ISM can effectively enhance the signal strength and spatial resolution of traditional confocal microscopy. However, its maximum resolution is limited to √2 times higher than confocal. On the other hand, stimulated emission depletion (STED) microscopy has been proven to be able to greatly improve the spatial resolution of confocal and has been widely used in practical applications. In this article,

To overcome the imaging speed and resolution of traditional imaging lidar, we propose a spatial and temporal multiplexing array imaging lidar technique. Based on optical orthogonal code division multiple access (OOCDMA), square laser beam with 22N-order code division multiple access coding are divided into 2N×2N, then they are projected to the targets without scanning. Finally, the backscatters are

Laser surface melting (LSM) is an important laser processing technique that can be used in laser conduction welding, laser remelting, and defect elimination. Penetration depths are essential to determine LSM qualities. To enhance the ability to predict penetration depths, a real-time prediction method based on coaxial visual characteristics and the convection state of a molten pool is reported. First

Emergence of products that feature functional surfaces with complex geometries, such as freeform optics in consumer electronics and augmented reality and virtual reality, requires high-accuracy non-contact surface measurement. However, large discrepancies are often observed between the measurement results of optical methods and contact stylus methods, especially for complex surfaces. For interference

A high-efficiency terahertz (THz) wave amplification approach by coupled cascaded optical parametric processes (CCOPP) with orientationally patterned gallium phosphide (OP-GaP) is introduced. The CCOPP comprises two cascaded optical parametric processes (COPP) which are intensely coupled by THz waves and cascaded optical waves via setting a precise periodic vector of OP-GaP. A simulation model that

The key challenge in laser butt-welding of dissimilar Al/steel metals, i.e., unevenly-distributed brittle intermetallic compounds (IMCs) along the interface, was solved via the beam oscillation under optimized laser offset (∆D). The IMCs thickness variance from top to bottom (δ) was adopted to quantitatively evaluate the uniformity of IMCs layer. The smaller the δ, the better the uniformity. The δ

Quantitive infrared thermography like active thermography is a non-destructive testing technique that is used to inspect surfaces of components for defects. A problem with infrared-based defect detection is that misclassifications based on geometrically dependent measurement characteristics can occur. This problem becomes more problematic with the inspection of complex 3D shapes. In this paper, a new

An optical image encryption scheme based on chaotic fingerprint phase masks (CFPMs) and pattern-illuminated Fourier ptychography (FP) is proposed. During the encryption process, the primary image that is under the non-uniform intensity patterns’ illumination can be encrypted into multiple low-resolution intensity images with the CFPMs placed respectively at the input plane and the Fourier plane. And

An MC (M: Ti,Nb) carbide-reinforced 316 L coating was synthesized in-situ via laser cladding. A strong relationship between the (Ti,Nb)C content and the microstructure and tribological properties of the resulting components was established. This relationship helped explain the influence of the (Ti,Nb)C content on the phase evolution, microstructure characteristics, and exothermic reaction behavior

Binary defocusing technique has been widely used in fringe projection profilometry for high-speed measurement. This technique projects designed binary patterns with a defocused projector to generate fringes for wrapped phase calculation, and n-ary simple codes (nSC) or n-ary gray codes (nGC) for phase unwrapping. The unwrapped phase reflecting the object surface profile is calculated by a phase-shifting

Rays hit droplets in the transmission path on severe weather conditions such as rain and fog during the target optical detection process. The presence of droplets causes the directions of rays and the amount of energy to change after rays pass through droplets, leading energy that eventually enters the detector to change, affecting target detection. This study establishes an energy distribution model

We report a computational 3D microscopy technique, termed Fourier ptychographic diffraction tomography (FPDT), that iteratively stitches together numerous variably illuminated, low-resolution images acquired with a low-numerical aperture (NA) objective in 3D Fourier space to create a wide field-of-view (FOV), high-resolution, depth-resolved complex refractive index (RI) image across large volumes.

Phase-shifting profilometry (PSP) has been widely used in three-dimensional (3-D) shape measurement because of its attributes of high-accuracy and high-resolution. However, PSP typically works under fluorescent light, flickering with a double frequency of the alternating current frequency, which may generate a non-ignorable phase error, and result in a PSP's measurement error, especially for PSP using

The moisture diffusion process in balsa wood was monitored using the terahertz time-domain spectroscopy (THz-TDS) technique. The reflective THz signals were measured during the drying and the absorption phase of the moisture in the balsa wood. Measurements were conducted along the direction of the wood grain (longitudinal) and perpendicular to the direction of the wood grain (tangential). From the