Digital fringe projection is a surface-profiling technique used for highly accurate non-contact measurements. As with any measurement technique, a variety of sources degrade to the measurement accuracy of the method. This paper presents an analytically-derived probability density function that explicitly models the surface height measurement error due to inevitable phase measurement error, and it includes

Light-field imaging technique provides a new approach to non-intrusive temperature measurement, which can achieve 3D measurement via single detector equipment. We consider wave characteristics of radiation rays in the light-field imaging model in this work. We propose an improved light-field imaging model of an emitting and absorbing medium by combining wave optics theory and radiation transfer process

Structural color with polarization sensitivity has been widely studied due to its benefits for improving information storage and dynamic color display capacity. However, large amount and good concealment of information encoding are the major issues to be addressed. Here, we propose the elliptical Al/a-Si/Al (metal-insulator-metal, MIM) nanostructure arrays as the basic building blocks to realize p

In this paper, an absolute position-distance measurement based method for simultaneous measurement of six-degree-of-freedom (6DOF) errors of a precision rotary stage is proposed. This method uses the multi-wavelength phase-shifting interferometry technology and high-speed CCD camera to measure the instantaneous absolute spatial posture of the specially designed micro structure feature following the

The so-called Optical Asymmetric Cryptosystems (OACs) have attracted more and more attention due to the unique mechanism of encryption/decryption and higher security level resulted from the involved nonlinear operations. Meanwhile, several attack methods have also been reported to analyze the security risk of typical OACs. In this work, we first stated our basic views about two famous OACs and then

In this paper, a phase unwrapping method based on Residual Auto Encoder Network is proposed. Phase unwrapping is regarded as a multiple classification problem and it will be solved by the trained network model. Through training and validation stages, optimal network model can be served as a predictor to predict wrap count distribution map of wrapped phase. Then merge wrapped phase and count together

Thermal Wave Radar (TWR) imaging employs the concept of pulse compression in order to obtain an increased probing depth and depth resolution in infrared thermographic testing of materials. The efficiency of the TWR imaging is highly dependent on the nature of the employed excitation signal. Most studies exploit the use of an excitation signal with an analogue frequency modulation (e.g. sweep signal)

A new scan path strategy is presented to reduce the duration of laser processing of geometries consisting of scattered, unconnected processing areas of a small size. We refer to these as fragmented geometries. The novelty of this strategy is to first identify optimized parallel scan lines for the overall shape using the Radon transform, which provides information about the most productive scan line

Fourier ptychographic microscopy (FPM) is a promising phase retrieval algorithm that does not need interferometry. Recently, reflective FPM has been highlighted as a measuring method for surface inspection in the industry, but using it is challenging because of the limited speed of the conventional misalignment correction methods. Here, we propose a new misalignment correction method to overcome this

We present a novel microscopy concept, termed Multi-Aperture Fourier ptychographic microscopy (MA-FPM), to enable implementation of parallel detectors in microscopy to increase the space-bandwidth-time product. MA-FPM is a synthetic aperture technique: an array of objectives together with tilt-shift illumination are used to synthesize high-resolution, wide field-of-view images. Here, the phase is recovered

In recent years, terahertz (THz) imaging technology has attracted much attention in the detection of the integrated circuit (IC). However, limited by the hardware of the imaging system, THz images often contain a significant amount of noise, which impairs the quality of the image details. The THz image is also degraded due to the long wavelength. In this study, we propose a novel method for THz image

Non-destructive evaluation (NDE) of cement hydration was conducted using pulsed and continuous-wave terahertz systems. The transmitted and reflected terahertz (THz) waves passing through the cement were measured and their relationship with the degree of the cement hydration was investigated. For an in-depth study, the chemical constituents and microstructure of the cement were analyzed through a Fourier

In the digital holographic microscopy, accurate phase restoration is essential to quantitatively test microstructure, especially in the case of dislocations and coherent noise. In this paper, a new phase restoration method with an adaptive reliability mask for phase unwrapping is proposed. By using horizontal and vertical projections to segment the unreliability map and performing the adaptive iterative

Marker coordinate recognition (MCR) is widely used in fields such as medical character positioning, artificial intelligence control, and motion and deformation monitoring. Registration algorithms are often applied to improve the accuracy of MCR. However, external conditions such as light and temperature induce a temporal variation in the grey level during image acquisition, thereby reducing measurement

Phase-extraction is important in various fields of optical metrology, for which, many phase-shifting algorithms have been developed. Among them, the advanced iterative algorithm (AIA) can accurately extract phase from fringe patterns with random unknown phase-shifts by iteratively estimating the phase and phase-shifts. However, these iterations make the AIA much slower than traditional phase-shifting

Conventional high-accuracy three-dimensional (3D) reconstruction methods usually involve complicated and time-consuming system calibration. This paper presents a novel and simple 3D reconstruction model based on a parallel-axis structured light system. Compared to the traditional structured light system, the proposed system contains a perspective projection unit and a telecentric imaging unit. Instead

A spatial carrier fringe pattern analysis technique is proposed for the phase demodulation using the extended complex Kalman filter. A state space model is defined based on the spatial evolution model of the fringe signal in a given row or column of the fringe pattern depending on the direction of carrier fringes. Since the state space model incorporates one of the state associated with the carrier

When looking for any metrological verification of parts manufactured by metal laser printing with optical equipment, it is necessary to ensure the traceability of the measurements that can be obtained. The difficulty of this process lies in the fact that these measurements are obtained on point clouds captured from surfaces with high form errors and poor surface finishes, even when this type of surface

In this paper, we propose a new optical encryption approach based on quantum walks and double random phase encoding technique. Quantum walks have been proven as an excellent tool for designing modern cryptographic mechanisms due to its ability to resist probable attacks from both digital and quantum computers. In the proposed approach, we use the alternate quantum walks (AQW) at two encryption stages

Surface shape and surface displacement measurements for non-planar specimens are obtainable using a stereo vision system with digital image correlation (StereoDIC). The surface measurements can be employed with appropriate local surface fitting methods to extract full-field estimates for surface strains on the specimen surface. Since StereoDIC provides a dense set of 3D surface position measurements

A simply structured full-color holographic three-dimensional (3D) display system using an angular-compensating holographic optical element (ACHOE) is proposed. This system adds an ACHOE into the traditional monochrome display system to realize a full-color display system. The ACHOE can increase the separation angle of color dispersion by increasing the angle difference of different colors, making it

Terahertz radiation has been used to obtain material's internal information because of its penetrability to optically opaque materials. In this paper, terahertz radiation is adopted to characterize the stress in single crystal silicon. Firstly, a theoretical model is established to describe the relationship between the phase retardation of the terahertz radiation and the stresses undergone by silicon

In multi-wavelength lensfree microscopy (MWLM), a laser source is usually replaced with a light-emitting diode for a low-cost and portable configuration. However, the trade-off between noise suppression and resolution enhancement puts a challenging issue for high-quality imaging. Here we propose a noise-robust multi-wavelength phase retrieval to increase the stability of MWLM. To solve the inverse

Digital Image Correlation (DIC) is the heart of the remote deformation measurement techniques using images. It is applied to many different applications from medical imaging to engineering problems for measuring deformation remotely with high accuracy. Whereas it is highly successful in measuring continuous deformation, it has severe limitation of failure in measuring discontinuous deformation. Most

In this paper, we proposed an iterative attacking algorithm to the pure phase asymmetric optical cryptosystem based on unequal modulus decomposition. Furthermore, we have proposed a secure asymmetric cryptosystem based on cascaded unequal modulus decomposition in the Fresnel domain. Fresnel transform and unequal modulus decomposition are highly sensitive to their parameters. An input grayscale image

This paper proposed a method of analyzing the measurement accuracy of a laser tracing system using the deviation of the incident beam from the center of a cat's eye retro-reflector. Based on the laser tracing system's measurement principle, a corresponding model is established to analyze the influence of the incident beam deviation from the center of cat's eye retro-reflector at the initial measurement

This paper studies an image encryption algorithm based on multi-objective particle swarm optimization (MOPSO), DNA encoding sequence and one-dimensional Logistic map. First, the key of this paper consists of the sub-key sequence selected by particle swarm optimization (PSO), a hash value of the plaintext image, and a shuffle mark bit. Create random DNA mask images using Logistic map and DNA encoding

Using digital holography technology to reconstruct the optical information of the calibrated grating, the grating pattern can be magnified without an optical lens. This greatly reduces the volume and complexity of the image angular displacement measurement device. This paper proposes an angular displacement measurement technology based on in-line digital holographic reconstruction. The wavefront recording

Synchronous measurement of full-field temperature and deformation at elevated temperature using non-contact optical methods attracts increasing attention in evaluating the high temperature properties of materials. The current optical methods all face one major challenge, which is the strong light reflection on the surface of the specimen. Such strong light reflection could greatly impair the measurement

Improving the time efficiency of fringe projection profilometry (FPP) is an attractive problem. For FPP using phase-shifting, it is desired to improve the efficiency by reducing the step number for phase retrieval. This paper proposes a two-step phase-shifting algorithm dedicated to FPP. Considering the physical process of FPP, the captured fringe image is formulated with two variables, i.e. surface

An optical color image encryption method based on Hadamard single-pixel imaging (SPI) and Arnold transformation is proposed, in which, optical full-color image encryption with good imaging quality and high security performance can be accomplished by only one bucket detector (BD). In the encryption process, after controlling and modulating the Hadamard matrix by the coefficient matrix key, three different

The phase measuring deflectometry is a promising method for the high precision measurement of optical freeform surfaces. However, it fails to measure the double surfaces of transparent lenses, because the fringes reflected from both the upper and the lower surfaces are superimposed in the captured images. An effective method is proposed to solve this problem by displaying a set of fringe patterns with

In this work we present a secure selective recovery protocol for multiple optically encrypted data based on sampling with orthogonal random binary masks. In this protocol, every single object is encrypted using a single arm free-space cryptosystem, filtered and multiplied by an orthogonal random binary mask, then all the encrypted, filtered and sampled objects are multiplexed. Under this protocol,

Well-aligned zinc oxide nanorods (ZnO NRs) array have been grown by wet chemical method on seeded substrates at low temperature. Gold nanosheet has been deposited by DC magnetron sputtering on the surrounding of the ZnO NRs array at glancing angle, thus creating a three-dimensionally (3D) plasmonic hetero-nanostructure (HNS). The localized surface plasmon resonance (LSPR) is tuned and blue-shifted

A polarization-sensitive full-field optical coherence tomography (PS-FFOCT) system was developed, which is capable of revealing both the reflectivity and phase-retardation caused by the anisotropic samples simultaneously with the lateral resolution of 0.98 µm and the axial resolution of 2.4 µm. The system was used to generate depth-resolved en face isotropic intensity images and birefringent images

A compact and low-cost system capable of Digital Holographic Microscopic (DHM) imaging of immobilized micro-particles is presented. The proposed design, integration, and manufacturing can lead to wider use and increased accessibility of this device for research, education, and biomedical applications. The optical tweezer system for particle immobilization is built using the optical pickup unit taken

Planar laser-induced phosphorescence (PLIP) has been used for the temperature measurement of suspended phosphor aggregates. Two-dimensional surface temperature of fluidized phosphor aggregates was measured through a pair of spatial and wavelength resolved images in an environment where phosphors are heated by high-flux radiation. The heating was supplied by a multi-diode laser system which provides

White-light dispersive interferometry (WLDI) is an instantaneous, high-resolution optical metrological technique for measuring precise and complicated surfaces. This method enables nondestructive inspection of transparent-film-structure devices that are widely used in semiconductor packaging. We propose in this paper to use a home-built WLDI system with line-by-line spectral calibration, phase-shifting

Dual-wavelength fiber lasers have become an attractive candidate for the last few years in the area of optical imaging, optical communication, optical sensing, microwave, and terahertz signal generation. It offers small size, inexpensive, and simple fabrication along with high scalability to the existing state-of-the-art microwave-photonics networks. In this paper, we demonstrate experimentally a switchable

The Talbot effect of the finite phase grating is theoretically, computationally and experimentally investigated. The diffraction of finite periodic phase arrays in the Fresnel region is analyzed according to the scalar diffraction theory. The simulations can be performed with any PC using a MATLAB program developed by authors. Talbot images are generated for any light wavelength, grating period and

The present work deals with the depth of field characterization in a complex flow with strong curvature effects: the bubbly Taylor Couette flow. Measurements were carried out in a 2D (axial and radial) plane with a large contribution of the azimuthal velocity on radial and axial velocity. Ombroscopic imaging technique coupled with a Particle Tracking Velocimetry have been used to accurately measure

Due to residual stress effects in final parts, researchers have always been interested to measure residual stress in different structures as well as comparing and analysing different methods in order to increase the accuracy and select the best method to measure it in different conditions and materials. The hole-drilling by applying the rosette strain gauge is one of the most commonly used methods

A method is proposed to detect and correct the phase unwrapping error (PUE). Phase edge is defined to help detect points potential with PUEs. Then, phase derivatives of points crossing phase edges are used to inspect whether the phase edges are from surface discontinuity or PUE. This makes it possible to dismiss phases at discontinuous regions during the PUE correction. Hence, the proposed method evidently

In this paper, a new generating technique of sinusoidal fringes for 3D shape measurement is presented. Specifically, a sinusoidal fringe is generated by expanding the inverted image of a filled binary sinusoidal pattern in a specified direction, and further, the phase shift is realized by switching the backlight sources of a set of sinusoidal patterns. In theory, sinusoidal fringes can be formed whether

In the high frequency laser system, the internal defects of optics will affect their damage threshold and downstream modulation, and even lead to subsequent surface damage. In order to efficiently and reliably evaluate the internal defects in optics, an automatic evaluation method of scattering defects in optics is proposed, and the corresponding three-dimensional (3D) precision measurement system

Since a slight variance in production processes can make the entire production run defective, defect inspections are indispensable procedures in manufacturing processes to ensure high quality of each item before entering the next manufacturing step. Three-dimensional (3D) optical shape measurement technologies are widely applied for surface defect inspection of complex workpieces because of its high-accuracy

In OLED panel repair process, femtosecond laser ablation has been adopted for last 10 years. Because femtosecond laser process can be performed with negligible thermal effect, it is suitable for modifying the organic materials whose lifetime is negatively affected by heat. Because of it, femtosecond laser ablation process has been applied to repair process of OLED panel such as elimination of internal

For establishing an accurate and reliable distributed optical fiber perimeter security system, this paper proposes a novel abnormity detection solution to security using Recurrent Plot (RP) and deep learning technology. Take advantage of the temporal correlation of intrusion signals, we encode the sensing signals into two-dimensional images through the RP algorithm. The RP algorithm can extract the

We investigated the relationship between composite multiscale entropy (CMSE) and absorption coefficient, refractive index within the terahertz (THz) region by using six concentrations (5000, 1000, 500, 50, 10, and 5 µg/ml) of bovine serum albumin (BSA) aqueous solutions. Variational mode decomposition (VMD) method served as a preprocessing tool was attempted to introduce to decompose THz signal into

Compared with monochromatic or RGB imaging technologies, multi-spectral imaging technology is beneficial for obtaining more information details from images of different wavelengths with better contrast. A novel portable and cost-effective multispectral microscope is proposed, whose highlights are firstly imaging by a special designed singlet lens with only controlled rotational symmetric aberrations

A novel chaotic cryptosystem for hyperspectral image, in this paper, is proposed by using a 4D hyperchaotic system in gyrator transform domains. In encryption process, a random spiral phase function (RSPF) is designed to generate variable spiral phase mask, which can be used for phase encoding with the hyperspectral image. Subsequently, the 4D hyperchaotic system is utilized to generate the chaotic

A blind optical color watermark scheme is proposed with single-pixel imaging (SPI), redistributed invariant lifting wavelet transform (RILWT) and singular value decomposition (SVD), in which, the watermark is first encrypted by the SPI and then embedded into host image with SVD in redistributed invariant wavelet domain. Bayer array is introduced into SPI to complete full color imaging of target scene

Brillouin optical time-domain analysis (BOTDA) based on optical chirp chain (OCC) has been proved that it is capable of fast and long range measurement. However, the performance of OCC-BOTDA is also limited by the issues of polarization fading and relative low signal-to-noise ratio due to transient stimulated Brillouin scattering (SBS) interaction. In this work, we propose a single shot OCC-BOTDA based

We report on femtosecond laser direct writing of electrically conductive copper structures on transparent cyclic olefin copolymer based planar optical chips. The process is based on a laser-induced reduction of CuO nanoparticles dissolved in a water-soluble resin. Thus generated conductive copper structures are characterized with respect to their chemical composition and electrical resistivity. In

A novel method, which is based on the phase difference between the filtered spectrum and simulated spectrum, is proposed to compensate for the optical path difference (OPD) demodulation error of the interferometer sensors. With applying the phase difference technology, large dynamic range OPD demodulation with high accuracy is realized. Its principle is deduced by theoretical analysis. The numerical

An original experimental setup, dedicated to the measurement of the dynamic response of structures, is presented. Called the Robotized Laser Doppler Vibrometer (RLDV), it consists in the assembly of a fixed point Laser Doppler Vibrometer (LDV) on a 6-axis industrial robot arm. This allows to measure the 3D velocity on the surface of objects with a wide range of shapes and sizes. In comparison with

As a combination of the annular laser beam and gaussian laser beam, adjustable ring mode (ARM) laser is a promising technology for stabilizing laser-based welding process. Process status and fusion efficiency of laser-materials processing was investigated experimentally under different shape of laser modes, including ring laser mode, center laser spot alone, and ring/center dual spots, with welding

An optical infinite-target generator is a key component utilized in the point-spread function (PSF) measurement of an optical camera. The traditional optical infinite-target generator uses a collimator that adopts an optical focal plane of single-aperture light lead-in. The measurement accuracy is relatively low and only a viewpoint PSF is obtained at a measurement. Moreover, the traditional optical

This work aims to demonstrate the possibility of using laser technology to seal compostable coffee capsules in engineered, poly(lactic acid) (PLA) based, bioplastic material with thermoplastic starch (TPS) toplids. The welded joints were characterized by peel-off tests to evaluate the adhesion energy of the toplid to the capsule body as the laser process parameters vary, i.e. the power of the laser

A single-shot procedure to reduce speckle noise in numerically computed unwrapped phase maps is proposed. The method is supported on the possibility of expressing the computed phase maps as phasors in the complex plane to understand the phase denoising as a pointwise iterative operation of phasor tuning. Notwithstanding in this work the method is applied in digital holographic microscopy, it could