Microlens Research Articles

Comparison of 1064-nm Nd: YAG picosecond laser with fractional micro-lens array and electro-optical synergy for post-acne erythema: a prospective, randomized, split-face trial.

Comparative data regarding the effectiveness of the 1064-nm Nd: YAG picosecond laser with fractional micro-lens array (P-MLA) versus traditional electro-optical synergy (ELOS) for treating post-acne erythema (PAE) are limited. Therefore, we aimed to compare the efficacy and safety of P-MLA and ELOS in the treatment of PAE. This prospective, randomized, split-face trial enrolled 20 patients with PAE, primarily of darker skin tones (Fitzpatrick skin types III-VI). Patients were randomly assigned to receive P-MLA treatment on one side of the face, and ELOS treatment on the other side. Three treatments were administered at 4-week intervals, with follow-up conducted at weeks 0, 4, 8, and 12. Standardized photographs were obtained using the VISIA system. Efficacy was assessed based on improvements in PAE lesion counts, clinical erythema assessment, VISIA skin analysis data, and patient-reported satisfaction. Adverse events were recorded. Both the P-MLA and ELOS groups showed significant reductions in erythema, with the P-MLA group demonstrating a notably greater decrease in PAE lesion counts and a higher clinical response rate at week 12 than the ELOS group. VISIA analysis revealed a greater reduction in red zone scores for the P-MLA group, alongside significant improvements in wrinkles and pigmentation. Patient satisfaction scores were comparable between the two groups, with an overall satisfaction rate of 94.74%. Adverse events, including erythema duration, edema, and pain, were similar across both groups, with no serious complications observed. P-MLA demonstrates superior efficacy and lower risk of adverse effects than ELOS in PAE treatment among Asian patients.

3D reconstruction of a highly reflective surface based on multi-view fusion and point cloud fitting with a structured light field

In this paper, a three-dimensional (3D) reconstruction method based on multi-view fusion and point cloud fitting is proposed to accurately reconstruct the highly reflective surface, which can effectively restore the highlight regions with only a single shot. A multi-view image fusion method based on the characteristics of microlens array cameras is used to remove unsaturated highlights. A new adaptive method, to our knowledge, based on binary images is designed to quickly extract the highlight regions. Then, what we believe to be a novel B-spline point cloud repair algorithm is proposed to construct geometric features for the highlight regions, and the weighted least squares plane fitting method based on priority is utilized to remove the saturated highlight point by point. More importantly, the 3D reconstruction system based on a structured light field is set up independently to verify the feasibility and effectiveness of the proposed method. The experimental results show that the proposed method can effectively achieve 3D reconstruction with large reflectivity changes and large highlight areas, and its repaired rate can reach 98.44%. Consequently, the proposed method can fully restore all highlight regions and can uniformly, accurately, and smoothly recover different highly reflective surfaces while avoiding hardware complexity.

Observations of Microlensed Images with Dual-field Interferometry: On-sky Demonstration and Prospects

Abstract Interferometric observations of gravitational microlensing events offer an opportunity for precise, efficient, and direct mass and distance measurements of lensing objects, especially those of isolated neutron stars and black holes. However, such observations have previously been possible for only a handful of extremely bright events. The recent development of a dual-field interferometer, GRAVITY Wide, has made it possible to reach out to significantly fainter objects and increase the pool of microlensing events amenable to interferometric observations by 2 orders of magnitude. Here, we present the first successful observation of a microlensing event with GRAVITY Wide and the resolution of microlensed images in the event OGLE-2023-BLG-0061/KMT-2023-BLG-0496. We measure the angular Einstein radius of the lens with subpercent precision, θ E = 1.280 ± 0.009 mas. Combined with the microlensing parallax detected from the event light curve, the mass and distance to the lens are found to be 0.472 ± 0.012 M ⊙ and 1.81 ± 0.05 kpc, respectively. We present the procedure for the selection of targets for interferometric observations and discuss possible systematic effects affecting GRAVITY Wide data. This detection demonstrates the capabilities of the new instrument, and it opens up completely new possibilities for the follow-up of microlensing events and future routine discoveries of isolated neutron stars and black holes.

Iterative Kramers–Kronig method for non-interferometric quantitative phase imaging: beyond the first-order Born and Rytov approximations

Traditional non-interferometric quantitative phase imaging (QPI) methods often face challenges in realizing rapid and accurate imaging of large-phase samples, mainly due to slow convergence and dependence on object approximation models. In this Letter, we propose a new, to the best of our knowledge, non-interferometric QPI approach that leverages iterative Kramers–Kronig (KK) relations, named iKK-QPI, to achieve high-accuracy quantitative measurement of objects with large-phase values. In the current KK relations reconstruction framework, we impose real-part constraints on the cepstrum, breaking the restriction of weak scattering condition. With only a few iterations, iKK-QPI extends the phase range that can be reliably retrieved by non-interferometric QPI, exceeding the first-order Born and Rytov approximations. The capability of iKK-QPI is demonstrated by imaging a microlens array and COS-7 cells. We accurately reconstruct objects with large-phase ranges 6 rad (error < ± 5%), three times that of the KK relations-based method, opening up the possibility for non-interferometric QPI to measure biological and industrial samples with large-phase features.

Fabrication and Simulation of Optical Shaping Diffuser to Control Light Patterns

This study utilizes a 532 nm picosecond laser micromachining technique on Schott-B270 glass to fabricate micro-lens array (MLA) with optimized curvature and minimal surface roughness, aimed at achieving an optical shaping diffuser. The research demonstrates a two-step fabrication process that combines picosecond laser processing with wet etching, significantly enhancing optical diffusion. Square-shaped micro-lenses with diffusion angles ranging from 29° to 62° were successfully created, along with hexagonal and rectangular shapes. Optical simulations using LightTools, which employed built-in Bezier curves to design micro-lens parameters, analyzed the impact of micro-lens arrangements on light patterns. The simulations indicated that varying the spacing and overlap ratio of the micro-lenses influenced light intensity distribution, achieving uniform light patterns with intensity variations of less than 10%. Experimental validation through optical measurements confirmed that the fabricated MLA produced well-defined light patterns, demonstrating their effectiveness for various optical applications. This work contributes to advancing the understanding of micro-lens fabrication techniques and their applications in enhancing light distribution.

Piecewise system identification and trajectory acceleration reallocating for diamond turning of microlens arrays

Piecewise system identification and trajectory acceleration reallocating for diamond turning of microlens arrays

Two-photon nanolithography of sub-micrometer thickness microlenses designed by NPCC assisted Rayleigh Sommerfeld diffraction integral

Recent development of artificial neural networks (ANNs) and inverse design methods have demonstrated their prospective significance for planar diffractive lens design, with a plethora of optical lenses designed for wavelengths ranging from visible to Thz wavelengths. However, previous research to design planner diffractive lenses only considers the maximum intensity in the focus area or its derivatives as the optimization function, leaving the intensity outside the focus area unconsidered. We proposed and investigated a two-dimensional (2D) physics-driven ANN method assisted by the negative Pearson correlation coefficient (NPCC) to design microlenses with varied focusing distances, which takes the entire 2D intensity distribution at the focus plane as an optimization function. Taking advantage of 3D two-photon nanolithographic technology, sub-micrometer thickness microlenses with varied focusing lengths are designed and fabricated, achieving an average focusing efficiency of around 35%, and an average focusing spot size of about 1 µm. Furthermore, a microlens array (19 by 19 microlenses with a total size of 4 mm2) with a curved focusing plane was fabricated and integrated into a CMOS sensor, achieving direct object imaging under incoherent white light illumination. Our results demonstrate that the NPCC is a very useful optimization function for designing planar diffractive lenses, and the use of NPCC in ANNs is of great potential for the future design of functional diffractive optical elements in optics and nanophotonics.

Laser-based 3D printing and optical characterization of optical micro-nanostructures inspired by nocturnal insects compound eyes

Nature offers unique examples that help humans produce artificial systems which mimic specific functions of living organisms and provide solutions to complex technical problems of the modern world. For example, the development of 3D micro-nanostructures that mimic nocturnal insect eyes (optimized for night vision), emerges as promising technology for detection in IR spectral region. Here, we report a proof of principle concerning the design and laser 3D printing of all ultrastructural details of nocturnal moth Grapholita Funebrana eyes, for potential use as microlens arrays for IR detection systems. Optimized computer-aided design and laser writing parameters enabled us to reproduce the entire complex architecture of moth compound eyes, with submicrometric spatial accuracy. As such, the laser-imprinted structures consisted in ommatidia-like microstructures with average diameter of about 14 μm, decorated with nipple-like nanopillars between 200 and 400 nm in height and average periodicity of around 450 nm. The dimensions of moth-eye inspired structures deviated by less than 10% from the natural corresponding structures. The optical properties of the moth eyes-inspired microlens arrays were investigated in the infrared (IR) range, between 1000 and 1700 nm. The optical transmission of microlens arrays with nanopillars was up to 17.55% higher than the transmission through microlens arrays without nanopillars. Moreover, the reflection of nanopillar-decorated microlens arrays was up to 0.91% lower than the reflection for microlenses without nanopillars. In addition, the focal spot diameter at 1/e2 for nanopillar—decorated microlens arrays was of 7.64 μm, representing and improvement of 16.5% of focal spot diameter as compared to microlens arrays without nanopillars. Similarly with the IR region, the reflection measured in the Visible range was higher for microlense arrays with nanopillars than the reflection through microlenses arrays without nanopillars. In contrast, in the Visible range the transmission of nanopillar-decorated microlens arrays was lower than the one for microlense arrays without nanopillars, which could be, most likely, assigned to diffraction losses on the nanopillars.

Refractive epitrochoids sampling for light field measurement using wedge prisms.

Conventional light field measurement using a micro-lens array suffers from grid-like artifacts in the refocused image because the sub-aperture images are sampled at linear and equal intervals like a grid pattern. In this study, we propose a method for measuring light field using a pair of wedge prisms and a method for calibrating the sub-aperture position. The epitrochoids trajectory of rays generated by rotating prisms yields unequal intervals and variable sampling of the sub-aperture position. We designed and calibrated the optical system, and verified the effectiveness of the proposed method on refocused images using the measured light field.

The Microlensing Event Rate and Optical Depth from MOA-II 9 Yr Survey Toward the Galactic Bulge

Abstract We present measurements of the microlensing optical depth and event rate toward the Galactic bulge using the data set from the 2006 to 2014 MOA-II survey, which covers 22 bulge fields spanning ∼42 deg2 between −5° < l < 10° and −7° < b < −1°. In the central region with ∣l∣ < 5°, we estimate an optical depth of τ = [ 1.75 ± 0.04 ] × 1 0 − 6 exp [ ( 0.34 ± 0.02 ) ( 3 ∘ − ∣ b ∣ ) ] and an event rate of Γ = [16.08 ± 0.28] × 10−6 exp [ ( 0.44 ± 0.02 ) ( 3 ∘ − ∣ b ∣ ) ] star − 1 yr − 1 using a sample consisting of 3525 microlensing events, with Einstein radius crossing times of t E < 760 days and a source star magnitude of I s < 21.4 mag. We confirm our results are consistent with the latest measurements from the OGLE-IV 8 yr data set. We find our result is inconsistent with a prediction based on Galactic models, especially in the central region with ∣b∣ < 3°. These results can be used to improve the Galactic bulge model, and more central regions can be further elucidated by upcoming microlensing experiments, such as the PRime-focus Infrared Microlensing Experiment and Nancy Grace Roman Space Telescope.

Quantum Dot Luminescence Microspheres Enable Ultra-Efficient and Bright Micro-LEDs.

Quantum dot (QD)-converted micrometer-scale light-emitting diodes (micro-LEDs) are regarded as an effective solution for achieving high-performance full-color micro-LED displays because of their narrow-band emission, simplified mass transfer, facile drive circuits, and low cost. However, these micro-LEDs suffer from significant blue light leakage and unsatisfactory electroluminescence properties due to the poor light conversion efficiency and stability of the QDs. Herein, the construction of green and red QD luminescence microspheres with the simultaneously high conversion efficiency of blue light and strong photoluminescence stability are proposed. These luminescence microspheres exhibit high external photoluminescence quantum yields exceeding 46% under 450nm excitation, along with excellent reliability against blue light, heat, and water-oxygen degradation, owing to the waveguide and spatial confinement effects of the microspheres. The microsphere-based green and red micro-LEDs achieve world-record external quantum efficiencies of 40.8% and 22.1%, respectively, and high brightness values of 1.7×108 and 7.6×107cdm-2, respectively. Finally, 0.6inch red, green, and blue monochrome micro-LED displays are demonstrated by integrating microsphere-converted micro-LED arrays with thin-film transistor backplanes, which show a pixel resolution as high as 1700 PPI and brightness exceeding 10000cdm-2.

Fabrication of Artificial Compound Eyes with Biplanar Focal Planes on a Curved Surface.

Inspired by ancient trilobites, novel curved microlens arrays (CMLAs) were designed. Direct, fast, and low-cost CMLAs with two focal planes were fabricated using ultraprecision machining technology and hot embossing technology. We designed four pairs of artificial compound eyes (ACEs) composed of large and small lenses with four different curvatures to achieve focusing and imaging on two focal planes. A test system was constructed to capture the first-order and second-order images for each level of the ACEs. Additionally, we analyzed the deformation patterns in the first-order and second-order images. The wide field of view (FOV) value was 68°, which aligns with the theoretical prediction. The focusing performance was also investigated, and the experimental results indicate that each lens achieves uniform focusing within the FOV range. These results confirm that microlens arrays with two focal planes possess advanced imaging and focusing capabilities, enabling a wide depth-of-field function. This opens new avenues for the development of advanced detectors and optical imaging devices.

Continuously focus tunable 2D/3D switchable cylindrical liquid crystal microlens arrays for autostereoscopic displays.

Cylindrical microlens arrays are important optical elements for autostereoscopic display. Conventional fixed focal length cylindrical microlens arrays do not allow switching between 2D mode and 3D mode when constructing a 3D viewing zone. In contrast, cylindrical liquid crystal microlens arrays with zoom characteristics allow switching between 2D and 3D states, as well as adjusting the width of the sub-viewing zone. Therefore, based on the quantitative analysis of the geometrical structure of the viewing zone in different states, this paper proposes a continuous zoom type cylindrical liquid crystal microlens array structure, which is a liquid crystal cell composed of an array of plano-concave glass substrates and planar glass substrates. Theory and experiments show that it is close to a favorable parabolic phase profile at different driving voltages, and at the same time, it can realize a zoom range of 1.6mm-36 mm at a smaller driving voltage. The wide zoom range and excellent zoom effect make this structure particularly suitable for autostereoscopic display, and this characteristic can achieve the effect of switching between 2D and 3D by adjusting the shape of the central viewing zone.

Graphene/TiO2 Heterostructure Integrated with a Micro-Lightplate for Low-Power NO2 Gas Detection.

Low-power gas sensors that can be used in IoT (Internet of Things) systems, consumer devices, and point-of-care devices will enable new applications in environmental monitoring and health protection. We fabricated a monolithic chemiresistive gas sensor by integrating a micro-lightplate with a 2D sensing material composed of single-layer graphene and monolayer-thick TiO2. Applying ultraviolet (380 nm) light with quantum energy above the TiO2 bandgap effectively enhanced the sensor responses. Low (<1 μW optical) power operation of the device was demonstrated by measuring NO2 gas at low concentrations, which is typical in air quality monitoring, with an estimated limit of detection < 0.1 ppb. The gas response amplitudes remained nearly constant over the studied light intensity range (1-150 mW/cm2) owing to the balance between the photoinduced adsorption and desorption processes of the gas molecules. The rates of both processes followed an approximately square-root dependence on light intensity, plausibly because the electron-hole recombination of photoinduced charge carriers is the primary rate-limiting factor. These results pave the way for integrating 2D materials with micro-LED arrays as a feasible path to advanced electronic noses.

High reflectivity surface highlight removal technology based on light field polarization imaging.

This paper proposes an imaging technique to remove strong reflections from specular surfaces using polarization characteristics combined with light field imaging. Firstly, the correct strong reflection region is found by studying the reflected light characteristics, and the strong reflection region highlights are filtered out using Stokes parameters based on polarization information. Then, a system of microlens arrays with different transmittances was built for imaging, and the system was image-corrected to enable more information about the scene to be captured. Finally, the color statistics are corrected according to the color characteristics, and then the color adjustment is performed to enhance the local color transfer results to obtain a high-quality true color image. The results of the experiment suggest that the method proposed in this paper is effective in restoring the actual texture contours of large highlight regions on strongly reflective surfaces.

Liquid Crystal Microlens Arrays Based on Aluminum-doped Zinc Oxide Oriented Microstructure Facilitate Light Field Image Resolution Enhancement

Liquid Crystal Microlens Arrays Based on Aluminum-doped Zinc Oxide Oriented Microstructure Facilitate Light Field Image Resolution Enhancement

ASSEMBLY COUPLING TECHNOLOGY OF MICROLENS ARRAY AND OPTICAL FIBER BUNDLE

Continuous improvements in high-resolution infrared remote sensing imaging technology have led to important applications in various fields; however, the low filling rate of optical fiber and degradation of the focal ratio of the image end remain problems that restrict further development. The coupling technology of the microlens array and optical fiber bundle assembly is the key to solving these problems. In this work, we studied the coupling technology of microlens array and optical fiber bundle assembly. Specifically, six degrees-of-freedom coupling assembly and infrared radiation energy measurement subsystems were built, and based on this a high-precision mechanical alignment coupling efficiency measurement system was designed. After kinematic analysis, it was found that the maximum positioning error was within the allowable error range, making the system suitable for the requirements of precision assembly. Finally, the alignment coupling efficiency of the system was tested, and the results showed that the coupling efficiency reached 92.65&amp;#37;, which was only 6.01&amp;#37; lower than the assumed theoretical value and affirmed the feasibility of the system design for improving the performance of optical fiber image transmission systems.

Privacy-preserving face recognition with a mask-encoded microlens array

Privacy-preserving face recognition with a mask-encoded microlens array

Integral imaging 3D display using triple-focal microlens arrays for near-eye display with enhanced depth of field

Integral imaging 3D display using triple-focal microlens arrays for near-eye display with enhanced depth of field

Primordial black holes in SB SUSY Gauss-Bonnet inflation

Here, we explore the formation of primordial black holes (PBHs) within a scalar field inflationary model coupled to the Gauss-Bonnet (GB) term, incorporating the low-scale spontaneously broken supersymmetric (SB SUSY) potential.The coupling function amplifies the curvature perturbations, consequently leading to the formation of PBHs and detectable secondary gravitational waves (GWs).Through the adjustment of the model parameters, the inflaton can be decelerated during an ultra-slow-roll (USR) phase, thereby augmenting curvature perturbations. Beside the observational constraints, the swampland criteria are investigated.Our computations forecast the formation of PBHs with masses around 𝒪(10)M ⊙, aligning with the observational data of LIGO-Virgo, and PBHs with masses 𝒪(10-6)M ⊙ as potential explanation for the ultrashort-timescale microlensing events recorded in the OGLE data.Additionally, our proposed mechanism can generate PBHs with masses around 𝒪(10-13)M ⊙, constituting roughly 99% of the dark matter.The density parameters of the produced GWs (ΩGW 0) intersect with the sensitivity curves of GW detectors. Two cases of our model fall within the nano-Hz frequency regime. One of them satisfies the power-law scaling as ΩGW(f) ∼ f 5-γ, with the γ = 3.51, which is consistent with the data of NANOGrav 15-year.