For the advancement of micro- and nano-technologies, multiaxial material testing at a small length scale is imperative. A novel multiaxial miniature testing system (MMTS) is under development for testing a tubular specimen of outer diameter (OD) as small as 1 mm. Because of the small specimen size of MMTS, stereo-Digital Image Correlation (DIC) is the preferred strain measurement technique. Although

A higher precision optical sensor for coal dust concentration measurement was developed in this study, in order to overcome the deficiencies of current coal mine dust detection (such as their low precision and poor stability). Based on Mie scattering theory, the effects of the dust particle size, refractive index, and scattering angle on the distribution of the scattered light intensity were examined

To evaluate defects on the surface of the materials at the 3D level accurately and quantitatively, a 3D surface defect detection system based on stereo vision is presented, which can extract the precise 3D defect features of the detected object. The proposed detection system consists of two image capture modules and a turntable to capture the complete 3D information and color texture information from

Image sensors based on microchannel plates (MCPs) have important applications as array image sensors owing to their high sensitivity and wide field of view, and because no scanning is required. When MCP-based image sensors, such as ICCD and ICMOS, are used for laser-active imaging, severe diffusion phenomenon occurs due to high electronic gain, and this significantly affects the resulting image quality

Shack–Hartmann wavefront sensor (SHWS) is a traditional method of obtaining the phase information of the incident light. As a classical method, SHWS has the merit of simple structure, good usability, real-time monitoring and wide waveband. Traditional SHWS depends mainly on a lenslet array which can split the incident wavefront and produce an array of distorted foci, which reflect the change of wavefront

When the intensity of light reduces to single-photon level, the shot noise becomes dominant. Random scatter, especially the time-varying media will highly increase the photon-limited imaging challenge that the traditional imaging means are inadequate to cope with. In this paper, we develop a new scalable “one to all” imaging approach which focuses on dynamic scattering imaging under photon-limited

An improved ant colony optimization algorithm has been developed in the present study to control an output scattered light field after an incident beam of light passes through a turbid medium. In this newly developed algorithm, the search rules and pheromone release rules of the basic ant colony optimization algorithm were modified which led to an improved search ability of the algorithm. Through reasonable

In this paper, the effect of non-collimated light path on moiré deflectometry is studied based on scalar diffraction theory. The complex amplitude of non-collimated light path is initially deduced, which shows it has a magnification factor compared with that of the collimated light path. Then, the intensity distribution and fringe equation are obtained, analyzed and discussed under different orders

Optical microscopy techniques have recently been shown to have the capability to exceed the diffraction limit when a microsphere is used. The mechanism involved in super-resolution imaging is theoretically analysed in this paper. A microsphere is also known to generate a photonic nanojet with a waist smaller than the diffraction limit. This nanojet is used as near-field illumination, and interacts

Spectral imaging systems using liquid crystal tunable filters (LCTFs) can be applied to color reproduction. However, the spatially-varying spectral shift caused by inherent LCTF characteristics affects the results’ accuracy. This paper proposes a spectral shift correction method employing high-chroma color patches as calibration targets, which reduces the color difference from 3.67 to 1.98 (CIEDE2000)

This paper reported a general non-interferometric high-accuracy quantitative phase imaging (QPI) method for arbitrary complex-valued objects. Given by a typical 4-f optical configuration as the imaging system, three frames of small-window phase modulation are applied on the object's Fourier spectrum so that redistributed intensity patterns are produced on the image plane, in which the object phase

In this paper, a laser triangulation sensor (LTS) with improved measurement accuracy via integrating a diffraction grating was proved. Compared to conventional LTS that only has the information of one light spot, the diffraction grating generates several diffraction light spots on CMOS image sensor. This enables to obtain multiple results of the object displacement simultaneously during one sampling

For a number of optical methods, including deflectometry, information is encoded in fringe patterns. To extract the phase data from intensity values, a number of phase shift algorithms have been designed. In deflectometry, the nonlinearity of the fringe display implies that the displayed fringe pattern presents a harmonic content even if the input pattern is perfectly sinusoidal. The propagation of

Metasurfaces for multi-band or wideband polarization control are usually achieved by cascading or nesting several elements in a period, which complicate the structure and introduce crosstalk. In this work, independent polarization control is achieved around two terahertz frequencies, 0.14 THz and 0.3 THz, through a simple binary one-dimensional grating. The correlation of the phase retardation with

Three-dimensional (3D) shape reconstruction from a monocular two-dimensional (2D) image has emerged as a highly demanded tool in many applications. This paper presents a novel 3D shape reconstruction technique that employs an end-to-end deep convolutional neural network (CNN) to transform a single speckle-pattern image into its corresponding 3D point cloud. In the proposed approach, three CNN models

This paper presents a novel method that can accurately calibrate structured light system requiring only one directional structured patterns. This method leverages the existing flexible camera calibration to extract each calibration pose for three-dimensional coordinate determination for each pixel, and then establish pixel-wise relationship between each coordinate and phase. The phase artifacts caused

A real-time three-dimensional(3D) shape measuring method based on dual-frequency spatial phase-shifting measuring profilometry (SPSMP) is proposed. To combine the low-frequency and high-frequency gratings into one single composite pattern, each individual grating is modulated along orthogonal direction with a distinct carrier frequency. Since the spectrum components are staggered in the spectrum of

A novel asymmetric image encryption method is developed by integrating with hyper-chaotic system (HCS), deoxyribonucleic acid (DNA) level operation, Arnold transform (ART) and phase-truncated fractional Fourier transform (ptFrFT). In this method, all the initial values and/or control parameters of HCS, DNA, Arnold transform and ptFrFT are generated from a plaintext image by utilizing the SHA-256 hash

We report an innovative method for early monitoring of the Opto-thermal health of laser-driven phosphor-converted white light source using low coherence spectral interference technique. A phosphor layer was irradiated using a high-power laser source in reflection mode and the broadband light generated from the phosphor layer was made incident onto a common path interferometer. The interferometer was

Two-wavelength digital holography (TWDH) can extend the unambiguous range of phase measurements. However, state-of-the-art TWDH is achieved either by using the on-axis or off-axis layout to create interference or by using a Bayer mosaic-filtered color CCD camera to record the hologram. This leads to a tradeoff among the acquisition rate, detector bandwidth, and measurement depth. To solve this issue

Fringe projection profilometry is widely used for three-dimensional (3D) measurements. System calibration is crucial to fringe projection systems, since it determines how the phase is converted into 3D geometry. Many methods and studies on calibration have been presented in the last few years. However, a comparative overview on the accuracy and the implementation details is still lacking. In this work

The nonlinear effect in phase shifting profilometry (PSP) is an essential source of phase error in 3D measurement. In this paper, we propose a universal phase error compensation method with a three-to-three deep learning framework (Tree-Net). Perfectly meeting the phase error compensation requirements, Tree-Net can construct six-step phase-shifting patterns from three-step. As a result, this compact

In the traditional optical cryptosystems based on computational ghost imaging, a large number of phase-only masks or speckle patterns are generated to reconstruct the object image with high visual quality. At the same time, this kind of massive data, which is usually considered as the security keys to enhance the security of the cryptosystem, needs to be stored and transmitted and leads to low efficiency

Limited by the field of view of the computer-generated hologram (CGH), full-aperture measurement of long cylindrical mirror with large curvature have been challenging. This paper reports a stitching interferometry based on sub-aperture adjustment with an aberration model represented by 2D Chebyshev polynomials. Firstly, a mathematical model under null measurement between the sub-aperture adjustment

As a novel volumetric velocimetry technique, the light field particle image velocimetry (LF-PIV) based on a single light field camera benefits from its single perspective configuration and has great potential applications in the space-constraint flow measurements. However, the severe particle elongation effects and relatively heavy computational load in the volumetric reconstruction of the tracer particles

In this work, spectral characteristics and temperature sensing characteristics of an in-line microfiber Mach-Zehnder interferometer (MZI) with an embedded microfiber knot resonator (MKR) is investigated. The microfiber MZI with an MKR (MZIKR) has a dual-effect composite spectrum with comb-like spectrum of the MKR loaded on the dominant interference spectrum. Vernier effect is generated by the MKR via

The phase retrieval problem, usually known as reconstructing an estimate of phase object from its diffraction intensity patterns, exists widely in the optical imaging field. In this paper, a deep convolutional neural network (CNN) framework is developed to accomplish the phase reconstruction given a single-shot Fourier measurement, without the requirement of prior knowledge (like nonnegativity and

Benefiting from the merits of low cost, high accuracy and high resolution, fringe projection profilometry has been developing rapidly over the past decades. However, recovering the absolute phase with high accuracy and robustness effectively has always been significant challenge in fringe projection profilometry. In this paper, an intelligent Multi-code Deep Learning (MCDL) technique is developed to

Misalignment measurement is a fundamental but challenging issue in optical lithography. Unfortunately, even with research efforts spanning a few decades, sub-nanoscale misalignment measurement remains a challenge. Through as a promising strategy, the high-accuracy moiré-based misalignment measurement is influenced by unfavorable factors and can only achieve accuracy on the nanoscale with regularly-manufactured

Multiplexed Structural Image Capture (MUSIC) technique uses modulation of light from a scene prior to imaging to encode the temporal evolution of target into spatial frequency shifts, with each shift corresponding to a unique time and resulting in individual distinct snapshots. Computational-processing of the multiplexed single-shot image can recover the nanosecond-resolution scene evolution. One of

As is widely known in the field of laser self-mixing interferometry (SMI), a commercial laser diode (LD) under linear injection current modulation can serve as a low-cost laser rangefinder, whose self-mixed signal exhibits a beat frequency proportional to the distance to be measured. So exact frequency extraction becomes a significant issue in this measurement scheme. In order to obtain better frequency

Pancreatic cancer has one of the worst survival rates of all major cancers, with pancreatic cystic lesions accounting for one in three pancreatic surgeries. The current gold-standard for diagnosis of pancreatic cyst malignancy is based on the endoscopic ultrasound guided fine-needle aspiration (EUS-FNA) procedure, which suffers from a low accuracy in detecting malignancy. Here we present the design

A general framework of a phase unwrapping procedure based on extended information filter is built. Two phase unwrapping algorithms with different observed models, are proposed by combining an extended information filter with an efficient phase gradient estimator, and an efficient quality-guided strategy based on heap-sort. The extended information filter that is a new type of filter with high efficiency

Conventional compressive light field (CLF) displays reconstructing three-dimensional (3D) scenes generally use stacked liquid crystal displays (LCDs). However, the low transmittance of LCD limits the number of stacked layers (usually three) and the image quality. In this paper, the realization of the CLF display with multi-plane projection is proposed by using polymer stabilized cholesteric texture

In this paper, the security of the cryptosystem with three phase-only masks (POMs) based on the interference has been evaluated. The security strength of the classical interference-based cryptosystem with two POMs has been enhanced by employing a random phase distribution to generate three POMs. This random phase distribution is utilized not only to replace the partial part of two POMs which could

The ability to non-destructively visualize transient phenomenon via spatial and temporal statistics of fluctuating speckle patterns is determined primarily by the contrast between regions of differing activity levels. We demonstrate a singular value decomposition-based method for extracting spatio-temporal correlation parameters from temporal sequences of dynamic speckle patterns. Each pattern in the

High-speed three-dimensional (3D) shape measurement techniques based on fringe projection profilometry (FPP) have undergone huge advances over the past two decades. However, accurate 3D displacement mapping and deformation analysis of dynamic scenes using FPP remains an unsolved problem. Because fringe patterns are projected rather than attached on the tested surfaces, the full-field point-to-point

Quick, easy and accurate measurements of the geometry of numerically controlled industrial machines have always been problematic for several reasons. Achieving high accuracy usually means considerable complexity of measurements, long measurement time and not negligible cost of the device. In addition, because users are interested in different geometry parameters, many measuring instruments are usually

In practical applications, the target objects or cameras are usually moving during the exposure time of the camera array in synthetic aperture integral imaging. Thus, the elemental images we captured are all blurred and can not be used to 3D reconstruction. The existing deblurring methods are most designed for single-image deblurring and just a few for multi-image deblurring. Nevertheless, all of these

Digital holographic measurement of rod-shaped particle size from inline holograms using a single-pixel of Wigner-Ville distribution (WVD) coefficients is proposed. The proposed sizing method detects only the spatial frequency coordinate of the single WVD output coefficient with a minimum amplitude to measure the particle size. The proposed method has advantages over conventional numerical reconstructions

Binary holography has been applied with fast switching digital masks, e.g., digital micromirror device (DMD), to modulate light in recent years for a wide range of optical and scientific applications, such as trapping of cold atoms and 3D random-access two-photon fluorescence microscopy. However, the binarized modulation errors associated with the effect of discrete sampling, finite pixels, and intrinsic

Shaping the optical wavefront utilizing spatial light modulators (SLMs) is a valuable methodology for modification of a focal spot. It has numerous applications in microscopy, particularly in scattering media. Optical lithography techniques, i.e. multiphoton lithography, can also benefit from wavefront shaping. In this contribution, we present focus optimization in multiphoton lithography through a

In order to compensate the lens axial position error in macrolens array based integral imaging display system, a calibration method of the reconstruction degradation caused by the lens axial position error is proposed. The dispersive spot size of a reconstructed point is employed as a measurement metric to investigate the characteristic of the reconstruction degradation, and further calibration of

The surface reflectance at micro scale is mainly dominated by wave effect and cannot be explained by geometric ray model. In this paper, we use wave optics to analyze the incoherent reflectivity and gained important insights into the establishment of the diffraction BRDF model of scratched material surface. In order to confirm the model given, we improve the BRDF measurement method into the sub-aperture

Copper-graphene composites have potential applications in flexible electronics due to their unique three-dimensional porous structure, high specific surface area, high electrical conductivity and electrochemical properties. Here, a simple room temperature fabrication method for conductive copper-graphene composites on different substrates, such as glass and polycarbonate, using direct laser writing

Laser beam used as a visualizing measuring axis has emerged as a major candidate technology for 3D shape measurement. Until now, a prime limitation has been the highly-accurate positioning of laser beam in the whole measurement space. A multi-position calibration method for laser beam based on the cyclical error of harmonic turntable is proposed in this paper. A flexible calibration field constructed

This work focuses on determining the optimal design for field widening, and thermal and achromatic compensating a static Mars wind imaging Michelson interferometer (MWIMI). The target lines of MWIMI are emission lines in the 1.27 µm band of the O2(1Δg) airglow. These emissions allow the dynamics of the Martian atmosphere from ~5 km to ~60 km to be observed. Two designs, a three-layer (consisting of

The overexpression level of Midkine (MDK) indicates the malignant degree of cancer cells, being a potential indicator and biomarker for cancer diseases. However, traditional biological methods such as Enzyme-Linked ImmunoSorbent Assay (ELISA) suffers inevitable disadvantages of long measurement time and false positive problems. In this study, the metasurfaces with electromagnetically induced transparency

An advanced phase-tilt iteration method is proposed for accurate and robust phase extraction from the interferograms with random tilt shift. The method constructs a system of linear equations about the tilt parameters via the spatial vector transform-based decoupling, and then establishes a least-squares alternate optimization. Using the two steps of initial estimation and fine iteration in the orthogonal

The strain error analysis is greatly concerned recently as digital image correlation (DIC) is used to measure the heterogeneous deformation. This paper focuses on the estimation of random error and under-matched error caused by two strain calculation methods, i.e. the point-wise least squares (PLS) and the regularized polynomial smoothing method (RPS). Two assumptions are put forward on the noise error

We proposed a new method for the radius of curvature (ROC) of spherical wave measurement based on vortex beam interference and Fermat's spiral fitting, which can not only provide a large measurement range but also have high precision. Theoretical analysis showed that the maximum distribution of the interference light intensity is in accordance with the Fermat's spiral, and the spiral coefficient is

In a smoke environment, target recognition is a pivotal problem faced by imaging-guided weapons and reconnaissance equipment. In fact, the transmittance of smoke is the main hindrance to recognition. In this study, a numerical method for extracting pixel radiance to calculate infrared (IR) smoke transmittance is proposed. First, a description of the field test and the equation governing the transmittance

The present study focuses on controlling the antireflective (AR) characteristics of one-dimensional moth eye structures on a high-resistivity silicon substrate by adjusting the profile (i.e., refractive index distribution) of its micro-tapers using femtosecond laser processing. Moth eye structures that comprise periodically arranged tapers with varying sizes and profiles (triangle, parabola, stair

Halogenated hydrocarbons are one of the main causes of atmospheric environmental pollution. The online detection of atmospheric halogenated hydrocarbons is a valuable and challenging research area. In this work, Laser-induced breakdown spectroscopy (LIBS) was used for the direct detection of halogenated hydrocarbons in air and the characteristic lines of the related halogens can be observed by the

We propose a multipath distributed acoustic sensing (MP-DAS) system based on phase-sensitive optical time-domain reflectometry (Φ-OTDR) and frequency division multiplexing (FDM) technique. With FDM introduced to Φ-OTDR, simultaneously monitoring of multipath vibration is realized with flexible functionality. In the proposed MP-DAS system, the parameters of each path can be adjusted individually according

Multi-layer hollow-core PMMA tube waveguides with varying grating structures were theoretically and experimentally investigated for the terahertz (THz) chemical material sensor applications. Compared with single-layer tube, the multi-layer cases can produce a delayed response in the time domain with an improved extinction ratio. A double tube combination consisted of a thick double-groove chirped grating

Measurement of surface shape and refractive index for moving transparent objects is critical in various fields. A parallel phase-shifting digital holography system that can record and reconstruct the phase information of moving transparent objects using two high-resolution polarization imaging cameras was presented. In the developed system, two polarization imaging cameras with 3.45 µm pixel pitch

A wavefront aberration causes focal spot distortion leading to loss of resolution and efficiency in laser processing. Therefore, aberration compensation is important for ensuring sub-micron resolution in laser processing. In this paper, femtosecond laser processing with adaptive optics based on a convolutional neural network was demonstrated. The aberrations existing in the laser processing system

3D shape measurement using phase shifting profilometry (PSP) has been extensively studied by the researchers in the past few years. With the recent binary defocused method, the measurement speed of these systems have been increased significantly. Yet, measurement errors are inevitable while imaging dynamic scenes. This is mainly because PSP methods require the object to be static for a short period

A new multiple-image encryption method based on a light-field imaging system and the gravity model is presented in this paper. An inverse process of light-field imaging was used for multiple-image encryption. The method first combined multiple images into one light-field image. It was then encrypted using the gravity model, which further improved the security. The structural parameters of the light-field