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Nowadays, the industry requires automatic production for high-speed manufacturing. However, the products must also maintain high quality and reliability. An efficient inspection technique should be conducted for the improvement in the manufacturing quality. In order to achieve high inspection rate, optical inspection based on machine vision often raises the threshold of the judgment and this will worsen false detection. In this study, we propose a high-accuracy optical inspection system based on deep learning technology. Various defects in screw head are precisely detected and analyzed, which include surface damage, unprocessed, and stripped surfaces. An industrial camera and microscope system are employed to collect the raw images of metal screws with different defect types. The raw images of 3200 are utilized to train the designed convolutional neural networks. The experimental results indicate that the proposed system reaches a detection accuracy of 92.8% and the average detection speed is 0.03 second per image. In comparison with conventional machine vision methods, the proposed measurement system is more suitable for the inspection of industrial production line.

In general, manual methods are often used to inspect defects in the production of metal screws. As deep learning shines in the field of visual detection, this study employs the You Only Look At CoefficienTs (YOLACT) algorithm to detect the surface defects of the metal screw heads. The raw images with different defects are collected by an automated microscopic camera scanning system to build the training and validation datasets. The experimental results demonstrate that the trained YOLACT is sufficient to achieve a mean average accuracy of 92.8 % with low missing and false rates. The processing speed of the trained YOLACT reaches 30 frames per second. Compared with other segmentation methods, the proposed model provides excellent performance in both segmentation and detection accuracy. Our efficient deep learning-based system may support the advancement of non-contact defect assessment methods for quality control of the screw manufacture.

The purpose of this study is to develop low-cost real-time digital fringe projection measurement to detect the three-dimensional shape of the back in patients with scoliosis. The measurement system consists of a digital projector and a digital camera. The seven fringe patterns are used to illuminate a patient’s back while the digital images are captured by a camera. The height of the back shape is calculated using the seven-step phase-shifting calculation and path-independent phase unwrapping. The back topography with an accuracy of 1 mm can help the clinician to estimate the spinal deformity at baseline and monitor variations over time. The measurement results can be applied to clinical use and reduce the dependence on serial radiography for monitoring spinal deformity.

Various optical components employed in biomedical applications have been fabricated using spider silk because of its superior properties, such as elasticity, tensile strength, biodegradability, and biocompatibility. In this study, a highly sensitive fiber optic sugar sensor is fabricated using metal-nanolayer-coated spider silk. The spider silk, which is directly collected from Nephila pilipes, a giant wood spider, is naturally a protein-based biopolymer with great flexibility, low attenuation, and easy functionalization. The surface of the spider silk-based fiber is coated with a metal nano-layer by using the glancing angle deposition technique. This fiber optic sugar sensor is based on the principle of the change in the refractive indices of sugar solutions. The attained experimental results show that the proposed sugar sensor is highly sensitive in the detection of fructose, sucrose, and glucose concentrations. This work may provide a new way to realize precise and sensitive online sugar measurements for point-of-care diagnostics.

Low-molecular-weight chitosan (LMWCS) damaged cell membranes in zebrafish showed its possibility to release reporter proteins for detection. In this study, we developed a simple fluorometric-based assay for the evaluation of clinical antiangiogenic drugs using LMWCS and Tg(fli1:EGFP) transgenic zebrafish, which expressed green-fluorescence protein (GFP) in the endothelial cells of blood vessel. In vitro stable and transiently transfected cell lines was released luciferase and green fluorescent protein (GFP) for intensity evaluation upon LMWCS fluorometric-based assay. In vivo Tg(fli1:EGFP) transgenic zebrafish was also released GFP from endothelial cells of blood vessels and show an increase of fluorescent intensity upon LMWCS fluorometric-based assay. Treatment with the clinical antiangiogenic drug sorafenib and analyzed by LMWCS fluorometric-based assay showed significantly reduction of angiogenesis. Furthermore, treatment with 2 μM sorafenib showed a significant reduction in angiogenesis of the intersegmental vein (ISV) and dorsal longitudinal anastomotic vessels (DLAV) in Tg(fli1:EGFP) transgenic zebrafish. Fluorescence intensity reduction from 2 μM sorafenib was used as a factor in the LMWCS fluorescence-based assay for relative antiangiogenic evaluation. Relative angiogenesis evaluation of the clinical drugs axitinib, cabozantinib, and regorafenib showed a significant reduction. Collectively, this study provided a simple, convenient, and rapid LMWCS fluorometric-based assay for evaluating angiogenic drugs using transgenic zebrafish.

The three-dimensional (3-D) micro-scale surface imaging system based on the digital fringe projection technique for the assessments of microfiber and metric screw is presented in this paper. The proposed system comprises a digital light processing (DLP) projector, a set of optical lenses, a microscope, and a charge coupled device (CCD). The digital seven-step fringe patterns from the DLP projector pass through a set of optical lenses before being focused on the target surface. A set of optical lenses is designed for adjustment and size coupling of fringe patterns. A high-resolution CCD camera is employed to picture these distorted fringe patterns. The wrapped phase map is calculated by seven-step phase-shifting calculation from these distorted fringe patterns. The unwrapping calculation with quality guided path is introduced to compute the absolute phase values. The dimensional calibration methods are used to acquire the transformation between real 3-D shape and the absolute phase value. The capability of complex surface measurement for our system is demonstrated by using ISO standard screw M1.6. The experimental results for microfiber with 3 μm diameter indicate that the spatial and vertical resolutions can reach about 3 μm in our system. The proposed system provides a fast digital imaging system to examine the surface features with high-resolution for automatic optical inspection industry.

The fringe projection profilometry with sinusoidal patterns based on phase-shifting algorithms is commonly distorted by the nonlinear intensity response of commercial projector. In order to solve this issue, sinusoidal width modulation is presented to generate binary sinusoidal patterns for defocusing the projection. However, the residual errors in the phase maps are usually notable for highly accurate three-dimensional shape measurements. In this paper, we propose the fringe patterns of the sinusoidal, square, and triangular periodic waveforms with seven-step phase-shifting algorithm to further improve the accuracy of three-dimensional profile reconstruction. The absolute phase values are calculated by using quality guided path unwrapping. We learn that by properly selecting fringe patterns according to the target shape, the undesired harmonics of the measured surface have negligible effect on the phase values. The experiments are presented to verify the imaging performances of three fringe patterns for different testing targets. The triangular fringe patterns are suitable for the shape measurements of complex targets with curved surfaces. The results provide a great possibility for high-accuracy shape measurement technique with wider measuring depth range.

In this Letter, we report on a numerical study, fabrication, and experimental observations of photonic nanojet (PNJ) shaping by control of a tangential electric field component. Here the PNJs are generated by a single mesoscale micro-cube that is fabricated from polydimethylsiloxane, deposited on a silicon substrate and placed on thick metal screen at illuminating wavelengths of 405, 532, and 671 nm. It is shown that the length, focal length, and width of the PNJ can be significantly reduced in the presence of the metal masks along the side faces of the micro-cube. Experimental measurements of the PNJ imaging are performed by a scanning optical microscope with laser sources. Our experimental results are in reasonable agreement with simulation predictions of the finite-difference time-domain method. Due to the appearance of the metal masks, the PNJ focal length decreases 1.5 times, the PNJ decay length decreases 1.7 times, and the PNJ resolution increases 1.2 times. Such PNJs possess great potential in complex manipulation, including integrated plasmonic circuits, biosensing, and optical tweezers.

Many challenges, such as virus infection, extreme weather and long cultivation periods, during the development of fish larvae have been observed, especially in aquaculture. Gene delivery is a useful method to express functional genes to defend against these challengers. However, the methods for fish larvae are insufficient. In our earlier report, low-molecular-weight chitosan (LMWCS) showed a strong positive charge and may be useful for polyplex formulation. Herein, we present a simple self-assembly of LMWCS polyplexes (LMWCSrNPs) for gene delivery into zebrafish larvae. Different weight ratios of LMWCS/gamma-polyglutamic acid (γ-PGA)/plasmid DNA were analyzed by gel mobility assay. Delivery efficiency determined by green fluorescent protein (GFP) expression in zebrafish liver (ZFL) cells showed that delivery efficiency at a weight ratio of 20:8:1 was higher than others. Zeta potential and transmission electron microscopy (TEM) analysis showed that the round shape of the particle size varied. In our earlier reports, IRF9S2C could induce interferon-stimulated gene (ISG) expression to induce innate immunity in zebrafish and pufferfish. Further delivery of pcDNA3-IRF9S2C-HA plasmid DNA into ZFL cells and zebrafish larvae by LMWCSrNP successfully induced ISG expression. Collectively, LMWCSrNP could be a novel gene delivery system for zebrafish larvae and might be used to improve applications in aquaculture.

In this study, we present the simulations and experimental observations of photonic jet (PJ) shaping by control of tangential electric field components at illuminating wavelengths of 405 nm, 532 nm, and 671 nm. The PJs are generated by a single dielectric 4-micrometer cube that was fabricated from polydimethylsiloxane (PDMS). The dielectric cube is deposited on a silicon substrate and placed on two aluminum masks with a width equal to the side length of the cube. Due to the appearance of the metal masks, the focal length and decay length of the generated PJs decreased almost twice, while the PJ resolution increased 1.2 times. Thus, PJ shaping can be controlled by the presence of the metal mask along the lateral surface of the cube without changing the external shape or internal structure of the cube. This effect is based on the control of the tangential components of the electric field along the lateral surface of the cube. In the case of a one-sided metal mask, the effect of optical deflection and bending is predicted to form a photonic hook. Due to the low cost of these dielectric cubes, they have potential in far-field systems to better meet the requirements of modern optical integration circuits and switches.

The photonic nanojet is a non-resonance focusing phenomenon with high intensity and narrow spot that can serve as a powerful biosensor for in vivo detection of red blood cells, micro-organisms, and tumor cells in blood. In this study, we first demonstrated photonic nanojet modulation by utilizing a spider-silk-based metal–dielectric dome microlens. A cellar spider was employed in extracting the silk fiber, which possesses a liquid-collecting ability to form a dielectric dome microlens. The metal casing on the surface of the dielectric dome was coated by using a glancing angle deposition technique. Due to the nature of surface plasmon polaritons, the characteristics of photonic nanojets are strongly modulated by different metal casings. Numerical and experimental results showed that the intensity of the photonic nanojet was increased by a factor of three for the gold-coated dome microlens due to surface plasmon resonance. The spider-silk-based metal-dielectric dome microlens could be used to scan a biological target for large-area imaging with a conventional optical microscope.

The characterization of surface micro-roughness is investigated by using off-specular measurements of polarized optical scattering. In the measurement system, the detection angles of optical scattering are defined by the vertical and level scattering angles. The rotating mechanism of angles is controlled by stepper motors. Waveplate and polarizer are used to adjust light polarization and detection. We conduct the optical scattering measurements by using four standard metal sheets of surface roughness. The nominal values (Ra) of standard micro-roughness are 1.6 μm, 0.8 μm, 0.4 μm, and 0.1 μm, respectively. Samples with different surface roughness are evaluated with the utilization of laser sources at three incident wavelengths. These polarized images are analyzed using a computer program to obtain the distribution of light intensity. The results show great correlation between the metal surface roughness and polarization states. This measurement system can be used to quickly and accurately distinguish between different surfaces and properties.

At present three main mechanisms of optical propagation with periodically focused modes in the chains of dielectric spherical particles with a refractive index near n = 1.59 are considered in the literature: evanescent whispering gallery mode coupling, photonic nanojet-induced modes, and the propagation of transverse magnetic modes under conditions close to Brewster angle geometry. In this paper we show that quasi-periodical focusing modes exist in a range of near unity refractive indices for chains of dielectric particles in both spherical and cubic forms. We also show that such a medium can be considered a gradient index waveguide with a parabolic law of refractive index variation.

The purpose of this study is to examine an optimal configuration of optical bottle beam generation. The proposed bottle beam is generated by casting a laser beam through an elliptical aperture and then through an axicon optical system. Simulation is performed by using multiphysics-capable wavefront technique, and the distance between the axicon and the focus lens can be adjusted. Two-dimensional Poincaré maps are employed to show the distribution of light. By combining Poincaré maps and expected position of the bottle beam, the relationship between the beam intensity and range is obtained. The simulated results can act as a reference for positioning optical components and expecting the effective zone of the bottle beam.

Islet transplantation (IT) is considered the most effective endocrine replacement therapy for diabetes mellitus (DM). Studies have demonstrated that IT can repair testicular structural injury caused by inflammatory and oxidative stress in a diabetic rat model. However, highly effective exogenous antioxidant and anti-inflammatory drugs can achieve this effect. Testicular interstitial fibrosis caused by long-term hyperglycemia is however difficult to reverse or recover. Thus far, there are no effective drugs that prevent or relieve testicular interstitial fibrosis. Therefore, it is necessary to explore the potential benefit of IT on testicular interstitial fibrosis induced by DM and its underlying molecular mechanisms. In the present study, Wistar rats were used to establish a DM model by intraperitoneal injection of streptozotocin. The diabetic models then underwent IT or received insulin treatment after 12 weeks. IT was more effective than insulin treatment in ameliorating diabetic-induced testicular interstitial fibrosis, Leydig cells apoptosis, testosterone deficiency and poor sperm motility. IT and insulin treatment both significantly inhibited the upregulation of TGF-β1 and phosphorylated Smad2 in DM, with IT being more effective than insulin. The present study's findings proved that IT effectively protects diabetic-induced testicular interstitial fibrosis probably by inhibiting the TGF-β1/Smad2 signaling pathway, which offers hope in male patients with DM complicating with testicular interstitial fibrosis.

We demonstrate the concept of fiber-based terahertz hook. The subwavelength photonic hook is obtained in the vicinity of a shaped fiber tip with asymmetric radiation. A 193 THz continuous-wave source, commonly used for medical imaging, has been required. Photonic hook with a lateral feature size less than the half-wavelength is achieved using a hemispherical shaped fiber tip with metallic mask. This breakthrough is carried out in ambient air by using a 2.58λ - diameter fiber with a shaped tip (λ is a radiation wavelength). A good correlation is observed between the computed intensity distribution of photonic hook and the tip sizes. Photonic hook generated with a shaped fiber tip, easier to manipulate, shows far-reaching benefits for potential applications such as ophthalmic laser surgery, super-resolution microscopy, photolithography, and material processing.

Structured light have made deep impacts on modern biotechnology and clinical practice, with numerous optical systems and lasers currently being used in medicine to treat disease. We demonstrate a new concept of fiber-based optical hook scalpel. The subwavelength photonic hook is obtained in the vicinity of a shaped fiber tip with asymmetric radiation. A 1550 nm continuous-wave source, commonly used for medical imaging, has been required. Photonic hook with a lateral feature size less than the half-wavelength is achieved using a hemispherical shaped fiber tip with metallic mask. This breakthrough is carried out in ambient air by using a 4-μm-diameter fiber with a shaped tip. A good correlation is observed between the computed intensity distribution of photonic hook and the tip sizes. Photonic hook generated with a shaped fiber tip, easier to manipulate, shows far-reaching benefits for potential applications such as ophthalmic laser surgery, super-resolution microscopy, photolithography and material processing.

In this Letter, we report the experimental observations of a tunable curved photonic nanojet (photonic hook) generated by a 5 µm polydimethylsiloxane microcylinder deposited on a silicon substrate and illuminated by 405 nm laser beam. A moveable opaque aluminum-mask is mounted in front of the microcylinder implementing partial illumination and imparting spatial curvature to the photonic nanojet. Experimental results of main parameters (tilt angle, width, and intensity) of emerging photonic hooks exhibit close agreement with numerical predictions of the near-field optical structures. The experimentally measured full widths at half-maximum of photonic hooks are 0.48 λ , 0.56 λ , and 0.76 λ for tilt angles of θ = 0 ∘ , 5.7°, and 20.1°, respectively. Photonic hooks possess great potential in complex manipulation such as super-resolution imaging, surface fabrication, and optomechanical manipulation along curved trajectories.

In this work, we experimentally demonstrate that a thin rectangle dielectric-metal structure can have a function of a flat focusing mirror based on photonic jet effect in reflection mode. Using polydimethylsiloxane (PDMS) rectangle with size length of 10 μm and wavelength-scale thickness of 1 μm on the top of a silicon wafer, we have built a flat mirror which focuses an incident beam at the focal length changing from 1.38 μm to 11.67 μm upon tuning the beam incidence angle from 30° to 75°. The focusing properties of such a mirror persist in the wavelength range of 405 nm to 671 nm. Our approach can be extended to realize other optical functionalities by properly controlling rectangle dimensions and materials. This flat focusing mirror is able to guide the incident beam in free space without perceptible diffraction at the distance equal to the photonic jet length and suitable for small-scale photonic circuits.

In this Letter, we propose a new, to the best of our knowledge, proof-of-concept of optical nano-tweezers based on a pair of dielectric rectangular structures that are capable of generating a finite-volume in-plane optical capsule. Finite-difference time-domain simulations of light spatial distributions and optical trapping forces of a gold nanoparticle immersed in water demonstrate the physical concept of an in-plane subwavelength optical capsule integrated with a microfluidic mesoscale device. It is shown that the refractive index of and the distance between the two dielectric rectangular structures can effectively control the shape and axial position of the optical capsule. Such an in-plane mesoscale structure provides a new path for manipulating absorbing nano-particles or bio-particles in a compact planar architecture, and should thus lead to promising perspectives in lab-on-a-chip domains.

A photonic hook (PH) is a high-intensity, curved focusing beam with a subwavelength waist based on the photonic nanojet effect. It is generally created by illuminating mesoscale transparent particles using optical plane waves. In this work, we numerically explore the generation of the PH supported by the Janus microcylinder under point-source illumination. To simulate the photonic intensity distributions near the shadow surface of the Janus microcylinder, a finite-difference time-domain technique is used. The power flow distributions near the Janus microcylinder are examined for working in the visible spectrum. Due to the asymmetric vortices of Poynting vectors, the PH with a large bending angle can be produced. By changing the location of the point-source illumination, the shape and curvature of the PH can be adjusted efficiently. Moreover, when the point-source illumination is located close to the Janus microcylinder, a long focal length PH can be present. Based on the numerical results, we propose a practical modeling scheme for optical imaging using a microscope where the light source is close to the target.

Probe rheology experiments, in which the dynamics of a small amount of probe chains dissolved in immobile matrix chains is discussed, have been performed for the development of molecular theories for entangled polymer dynamics. Although probe chain dynamics in probe rheology is considered hypothetically as single chain dynamics in fixed tube-shaped confinement, it has not been fully elucidated. For instance, the end-to-end relaxation of probe chains is slower than that for monodisperse melts, unlike the conventional molecular theories. In this study, the viscoelastic and dielectric relaxations of probe chains were calculated by primitive chain network simulations. The simulations semi-quantitatively reproduced the dielectric relaxation, which reflects the effect of constraint release on the end-to-end relaxation. Fair agreement was also obtained for the viscoelastic relaxation time. However, the viscoelastic relaxation intensity was underestimated, possibly due to some flaws in the model for the inter-chain cross-correlations between probe and matrix chains.

We first numerically and experimentally report large-area super-resolution optical imaging achieved by using core-shell microfibers. The particular spatial electromagnetic waves for different core-shell microfibers are studied by using finite-difference time-domain and ray tracing calculations. The focusing properties of photonic nanojets are evaluated in terms of intensity profile and full width at half-maximum along propagation and transversal directions. In experiment, the general optical fiber is chemically etched down to 6 µm diameter and coated with different metallic thin films by using glancing angle deposition. The direct imaging of photonic nanojets for different core-shell microfibers is performed with a scanning optical microscope system. We show that the intensity distribution of a photonic nanojet is highly related to the metallic shell due to the surface plasmon polaritons. Furthermore, large-area super-resolution optical imaging is performed by using different core-shell microfibers placed over the nano-scale grating with 150 nm line width. The core-shell microfiber-assisted imaging is achieved with super-resolution and hundreds of times the field-of-view in contrast to microspheres. The possible applications of these core-shell optical microfibers include real-time large-area micro-fluidics and nano-structure inspections.

The photonic nanojet is a highly concentrated beam with low divergence on the shadow side of dielectric microparticles. In this Letter, we first theoretically and experimentally investigate the formation of high-quality photonic nanojets by decorating spider silk. The dragline silks are directly extracted from cellar spiders and capable of efficiently collecting ultraviolet cure adhesive. The liquid-collecting capacity of the captured silk is the result of a singular fiber structure with periodic spindle knots. Using a scanning-optical-microscope system, we show that high-quality photonic nanojets are generated by silk fiber with spindle knots. With the variation in spindle-knot dimensions, the properties of photonic nanojets, such as intensity distribution, focal length, and full width at half-maximum, are able to tune flexibly. By combining the unique biocompatibility, flexibility, and tensile strength, the silk filaments with spindle knots pave a potential way for original bio-photonic applications.

In this study, we investigate an optical modulation of the focusing mirror based on photonic jet effect working in the reflection mode The photonic jet effects excited by surface plasmon polariton (SPP) in the near-field on the front-side of different core–shell micro-cuboids positioned on a substrate are presented. The core–shell micro-cuboid consists of a metallic shell (silver or gold) and a dielectric core (polydimethylsiloxane). The specific localized intensity distributions of the generated photonic jet at different core–shell micro-cuboids are simulated by using finite-difference time-domain technique. The experimental observations of focusing modulation are performed by a scanning optical microscope with oblique illumination. Due to the nature of SPP, the highly focused electric field near the metal–dielectric interface of the gold-coating micro-cuboids is enhanced by about 4 times. The generation of the focusing mirror based on SPP photonic jet can be flexibly controlled by varying the metallic shell. The controllable focusing mirror is a great possibility for integrated plasmonic circuits, surface optical tweezers, and biosensing.

We experimentally report the geometric effect on photonic nanojet generated by dielectric microcylinders with non-cylindrical cross-sections. The non-cylindrical cross-sections include truncated microcylinders and elliptical microcylinders. The truncated microcylinder is formed with the cutting thickness. The elliptical microcylinder is defined by ratio of minor to major axes. The specific spatial electromagnetic fields for microcylinders with different non-cylindrical cross-sections are studied by using finite-difference time-domain calculation. The direct imaging of photonic nanojets for microcylinders with different non-cylindrical cross-sections are performed with a scanning optical microscope system. The field distribution and location of photonic nanojet depending on the various spatial shapes are experimentally demonstrated. The photonic nanojet with long focal length and low divergence could be used to scan over a target to obtain a large area image when the non-cylindrical micro-media are coupled with a conventional optical microscope.