This work proposes a novel design in which an LED is mounted on the side wall of a multi-segment reflector, breaking the conventional symmetry of headlamp optics for the application of vehicle such as bicycle where the headlamp is always requested compact and light. Monte Carlo ray tracing was used to optimize the reflector, which was divided into 16 segments to generate a hot spot for the cut-off line. A cylindrical lens array (CLA) was then introduced to laterally spread and homogenize the pattern, ensuring symmetry and uniformity. A CNC-machined aluminum mockup with 80% reflectivity was fabricated and tested using an automated measurement system at 10m. The measured illumination patterns of both low and high beams were symmetrical and met all regulatory checkpoints. The results demonstrate the feasibility of side-mounted LEDs with segmented reflectors and CLAs for compact bicycle headlamp designs.

Super multi-view (SMV) display offers a promising solution for three-dimensional (3D) displays by projecting dense views directly into the single pupil. However, conventional SMV architectures face a trade-off between view density and spatial resolution for individual views. Here, we propose a view density enhancement method based on a polarization-multiplexed metasurface. The metasurface contains two sets of cylindrical lens array phase profiles with opposite lateral focal shifts under orthogonal polarization states. A proof-of-concept prototype was fabricated and characterized, and the experimental results demonstrate that the proposed device generates two groups of interleaved views and reduces the angular separation between adjacent views from 6° to 3°, thereby doubling the view density without compromising the spatial resolution of individual views. This work offers a promising strategy and compact route for view-density enhancement in advanced SMV displays.

3D light field display with enhanced reconstruction accuracy based on distortion- suppressed compound lens array and pre-correction encoded image

ABSTRACT A broad-focal-range liquid crystal (LC) lens array enabled by partitioned electric field modulation is proposed, featuring a simple design and low operating voltage. By combining zonal electrodes and a central electrode, the structure improves electric-field regulation in both the edge and central regions, enabling a smooth refractive-index distribution, effective focusing, and a wide focal tuning range. Simulation results show that, at 2 Vrms on the central electrode and 7.9 Vrms on the pixel electrodes, the lens achieves a near-ideal gradient refractive-index profile at a 500 μm aperture, with a minimum focal length of 1.601 mm. In addition, the phase distribution closely matches the ideal parabolic profile, and the centre-to-edge phase difference reaches approximately 71π, indicating strong phase-modulation capability, low spherical aberration, and good imaging potential. Therefore, the proposed structure shows potential for applications in 2D/3D switchable displays.

Terahertz hot electron bolometer (HEB) mixers, which offer the highest sensitivity in the frequency range above 1.5 THz, are equipped on space observatories to detect the terahertz radiation emitted from the interstellar medium within galaxies. To increase the mapping speed, it is essential to develop large HEB mixer arrays. However, conventional quasi-optical coupling methods, including single large silicon lens approaches and silicon lens array approaches, suffer from the conflict of achieving high filling factor and uniform illumination on the HEB mixer array. This paper reviews the research progress on quasi-optical coupled HEB mixer arrays and proposes an innovative array coupling scheme to overcome the existing limitation. We designed a metasurface beam shaper based on the Gerchberg–Saxton algorithm and COMSOL simulation to transform an incoming Gaussian beam into a flattop beam in the focal plane, thereby forming uniform illumination for an antenna-coupled HEB mixer array. The metasurface is intended primarily for uniform local oscillator (LO) distribution across the array. The simulation of the metasurface beam shaper at 0.6 THz demonstrates a flattop beam with a flat region approximately 3 mm wide, and the intensity across this region varies by only 4.2%. The same simulation is also performed at 1.6 THz, and the flat region is 1.5 mm wide with a 5.5% intensity variation. This work demonstrates the feasibility of using a metasurface to convert a Gaussian beam into a flattop beam at terahertz frequencies as well as a pathway for array-level coupling schemes for HEB mixer arrays with high filling factor and uniform illumination.

Projection Mapping (PM) is a technology that projects images onto the surfaces of physical objects, allowing multiple users to share an augmented reality experience without special devices. However, its practical use has been constrained by the need for dark environments to ensure high-quality projection. To overcome this "dark-room constraint," we propose a novel target-excluding lighting method that selectively illuminates the surrounding environment while avoiding the PM target. Our system achieves light-field illumination by combining an LED display panel with an optimized aperiodic lens array. The key contributions include a compact form factor that provides a large effective light source area, reproducing natural soft shadows comparable to typical lighting, while maintaining the spatial controllability needed to precisely avoid the target. We also introduce a computational technique for optimizing aperiodic lens placement to suppress undesired dark spots caused by crosstalk, and efficient methods for computing LED luminance patterns that enable dynamic PM. Experiments with a prototype system demonstrate that our approach achieves high-contrast PM even in bright environments.

Hydrogen generation from renewable energy sources allows balancing the intermittent nature of solar and wind power. The chemical energy stored in hydrogen can be efficiently converted back to electricity using fuel cells or hydrogen can be used in chemical processes or as secondary energy carrier in heat and gas markets. Several approaches have been investigated but most of them have a low conversion efficiency. Here we present a high-performance photovoltaic/electrolysis module that splits water molecules using the photovoltage of multi-junction solar cells. A Fresnel lens array concentrates direct sunlight onto photovoltaic cells with an open-circuit voltage above 4 V. These solar cells are electrically interconnected to the cathode and anode of two series-connected polymer electrolyte membrane electrolysis cells. A demonstrator with a lens area of 64 cm2 was measured outdoors, converting up to 31.3% of sunlight energy into chemical energy according to the higher heating value of hydrogen.

The spatio-temporal coupling effect can temporally and spatially distort the ultrashort laser pulses after focusing, resulting in temporal stretching and decreased power density, and its characterization is of great significance for processes such as light field modulation, and pulse compression, and focusing. A single measurement of the spatio-temporal coupling effect of ultrashort laser pulses is technically challenging. In this paper, a global three-dimensional phase retrieval technique based on lens array and compressive sensing is proposed and applied to the quantitative measurement of spatio-spectral coupling distortion of ultrashort laser pulses. The known amount of pulse-front tilt (PFT) in ultrashort pulses is introduced with a wedge plate, and then compressive sensing is carried out through a deformed CASSI (coded aperture snapshot spectral imaging) system. The grating is the dispersion element of this system. In experiment, this method can fully characterize the spatio-spectral coupling effect of ultrashort laser pulses in a single-shot measurement, with good consistency between theoretical and measured results, which reveals potential applications in the field of ultrafast dynamics.

ABSTRACT A thin virtual reality near‐eye display is proposed that provides a Maxwellian view using a holographic optical element (HOE) and a mini‐Fresnel lens array (MLA). A point light source array (PLSA) is holographically recorded into an HOE attached directly to the display panel, enabling reconstruction of a virtual PLSA without a physical module. This approach eliminates the intercomponent gap and significantly reduces optical thickness while maintaining vergence‐accommodation conflict (VAC) mitigation. Both transmission‐ and reflection‐type HOE configurations are experimentally demonstrated. Display experiments confirm constant image sharpness over a wide accommodation range (0–3.3 D), verifying successful Maxwellian‐view operation. This architecture provides a high‐performance optical solution for immersive displays by reducing center‐of‐mass shift and visual fatigue.

Fabrication of graphene oxide lens arrays via ultraviolet light reduction

Photoaging represents a significant clinical challenge with limited effective therapeutic interventions capable of reversing established UV-induced damage. While conventional laser therapies rely on thermal mechanisms with associated complications, picosecond laser-induced optical breakdown (LIOB) offers a revolutionary photomechanical approach. This study provides the first comprehensive molecular characterization of photoaging reversal mechanisms following consecutive 755 nm Alexandrite picosecond laser treatments. Thirty female BALB/c nude mice underwent validated UV irradiation protocols to induce photoaging, followed by randomization into five groups (n=6 each): control, UVA-exposed without laser, UVB-exposed without laser, UVA-exposed with consecutive laser treatments, and UVB-exposed with consecutive laser treatments. Three consecutive picosecond laser sessions (755 nm, 0.71 J/cm², 500 pulses with diffractive lens array) were administered post-induction. Comprehensive assessments included wrinkle scoring, erythema quantification, transepidermal water loss measurement, collagen intensity evaluation, histological analysis, and immunohistochemical molecular characterization. Consecutive picosecond laser treatments produced remarkable photoaging reversal across multiple biological systems. Wrinkle scores decreased from 2.11±0.78 to 0.78±0.67 in UVB-treated groups. LIOB simultaneously activated TGF-β/Smad pathways, enhanced collagen synthesis, reduced matrix degradation (decreased MMP-9 expression), restored barrier function (increased filaggrin and aquaporin 3 expression), and resolved inflammation (reduced NF-κB signaling). Histological analysis confirmed significant collagen regeneration and normalized epidermal architecture. This investigation establishes consecutive LIOB as a paradigm-shifting therapeutic approach that reverses photoaging through coordinated activation of repair pathways while avoiding thermal damage. The comprehensive molecular mechanisms elucidated provide robust scientific foundation for clinical translation, positioning consecutive picosecond laser technology as a transformative advancement in photoaging treatment with unprecedented efficacy and safety profiles.

This work experimentally investigates a solar and laser-diode hybrid-pumped Nd-doped fiber laser enabled by a port-matched aspheric lens array. A seven-element aspheric lens array is designed and constructed for solar end coupling, in which each lens concentrates sunlight into an individual pump fiber, and a standard 7 × 1 multimode pump combiner aggregates the seven channels into a single pump delivery path. An 808 nm LD is used as a reference pump to quantify the net gain of the solar end-pumping stage by comparing the 1064 nm output with and without the solar channel under otherwise identical cavity conditions. A single-pass bandpass-filter method isolates the 1064 nm laser component, indicating a net slope efficiency increase of 48.77% under hybrid pumping and an average output power enhancement of approximately 1.67 mW. Although solar-only pumping does not yet reach the oscillation threshold, the array-based solar channel provides a measurable positive gain at 1064 nm. The prototype relies exclusively on standard commercial fiber components. It requires neither sensitizers nor complex water-cooling infrastructure, which is attractive for mass- and complexity-constrained deployments such as spaceborne platforms. The array architecture further supports cascaded pump-power scaling by expanding the collection area and increasing the number of pump channels, providing a practical engineering pathway toward solar-only fiber-laser operation.

In this paper, we propose an all-diffractive, direct method for calibrating the phase response of liquid crystal on silicon spatial light modulators. This approach uses a single-phase mask comprising an array of binary phase Fresnel lenses, each of which samples a specific gray level across the full available range. Consequently, the complete phase calibration curve can be derived from a single recorded irradiance pattern, significantly reducing acquisition time and experimental complexity compared to conventional sequential phase calibration techniques, which require repeated measurements and additional optical components. The phase calibration method demonstrates accurate results under continuous-wave laser illumination and remains effective under periodic laser power oscillations (∼6.8 Hz). Thanks to its efficiency and adaptability, it enables rapid calibration and optimization under varying illumination conditions, making it particularly valuable for multispectral imaging and optical metrology applications.

This paper proposes an integral three-dimensional (3D) display that combines time-division multiplexing (TDM) and eye-tracking (ET) technologies to enhance the maximum pixel density and viewing-zone angle of 3D images. TDM synthesizes integral 3D and two-dimensional (2D) images using a lens array that can switch between lens-array and transparent modes, while ET expands the viewing-zone angle without degrading the maximum pixel density. Additionally, a method for generating elemental image arrays and 2D images optimized for ET was developed. The prototype display apparatus produced 3D images with a maximum pixel density of 510 pixels per inch and viewing-zone angles of 86.5° horizontally and 54.5° vertically.

This work presents a design method for creating second-order smooth (C2-continuous) freeform lens arrays. In particular, it introduces a design method of a single lens tile that can be seamlessly tiled to form a globally smooth array. Conventional freeform lens arrays rely on sharp transitions or discontinuities between tiles, which correspond to infinite curvatures that cannot be perfectly manufactured and are therefore a source of stray light. The proposed algorithm demonstrates that by introducing saddle-shaped lenses between convex and concave elements, a C2-continuous surface can be achieved while maintaining control over the target irradiance pattern. Because the surfaces contain no kinks or discontinuities, they minimize glare and stray light in illumination applications and are considerably easier to manufacture.

In this paper, we propose a fast-switching two-dimensional/three-dimensional (2D/3D) display based on a liquid crystal planar lenticular lens array (LCPLLA) with an ultra-thin functional layer. The LCPLLA enables rapid switching between focusing (3D) and transparent (2D) states through electrical control of the in-plane orientation of liquid crystal (LC) molecules. This design utilizes Pancharatnam-Berry phase principle rather than geometric curvature, thereby significantly reducing the thickness of the LC functional layer. Experimental results demonstrate that the device achieves a total switching time of 14 ms between the 2D and 3D modes, operates at a driving voltage of 8 V, and exhibits uniform focusing with well-defined focal spots, where the focal spot size variation across the lens array is below 1%. At the optimal viewing distance of 370 mm, the system provides high-resolution 2D images and distinct 3D visual effects. The proposed approach offers a compact, high-quality, and fast-responding solution for switchable 2D/3D displays.

Conventional methods for microlens array (MLA) fabrication suffer from high costs, long prototyping time, and limited geometric control. To address these problems, this study introduces an air-expansion-induced molding method for soft lens array fabrication. This method works by heating the air trapped in 3D-printed photoresist microcavities. The photoresist becomes convex due to the thermal expansion of the trapped air and is then solidified after UV curing as a mold for Polydimethylsiloxane (PDMS) casting. The deformation of the photoresist is theoretically analyzed and experimentally verified. It is found that the fabricated MLAs exhibit sub-10nm surface roughness and their curvature scales with both microcavity depth and temperature. The MLAs achieve an imaging resolution of 228.1 line pairs per millimeter and enable multi-focal plane imaging of microalgae in a microfluidic chip.

The interleaved linear Fresnel lens is known to improve image quality in autostereoscopic displays with time-multiplexed directional backlight. In this paper, we propose a method to reduce crosstalk by narrowing the width of the elemental lenses in the interleaved linear Fresnel lens array, thereby decreasing the width of the directional light. Furthermore, to address the luminance non-uniformity that stands out when using a fine-pitch interleaved linear Fresnel lens array, we propose a technique in which an adaptive mask pattern is displayed on a liquid crystal display (LCD) panel and superimposed on the lens array. The proposed method reduced the crosstalk level approximately by half and improved luminance uniformity regardless of the viewing angle by applying an adaptive mask pattern.

High-resolution coarse integral imaging (CII) utilizes a fine-pitch interleaved Fresnel lens array; however, the smaller lens pitch dramatically increases the number of views to be rendered, hindering real-time performance. Moreover, extending the viewing zone requires elemental images to be generated in real time to match the viewer's eye position, making high frame rates indispensable. To address these challenges, we introduce a cluster-level culling technique that accelerates multi-view rendering for CII and sustains real-time frame rates even for scenes with millions of polygons. We further implement the technique in a prototype system on an iPad and an iPhone, both of which achieve real-time performance, demonstrating that CII can be realized with an exceptionally simple mobile-device setup.

Applicability of projection lithography using a gradient-index lens array to patterning of 50–150 micron thick resist