Lens Array Research Articles

Development of optical microneedle–lens array for photodynamic therapy

Recently, photodynamic therapy (PDT) which involves a photosensitizer (PS), a special drug activated by light, and light irradiation has been widely used in treating various skin diseases such as port-wine stain as well as cancers such as melanoma and non-melanoma skin cancers. PDT comprises two general steps: the introduction of PS into the body or a specific spot to be treated, and the irradiation process using a light source with a specific wavelength to excite the PS. Although PDT is gaining great attention owing to its potential as a targeted approach in the treatment of skin cancers, several limitations still exist for practical use. One of the biggest challenges is the limited penetration of light owing to scattering, reflection, and absorption of light inside the skin layers. In addition, accidental light exposure of the target area causes additional cellular damage, which causes unexpected complications. To solve these issues, we introduced an optical microneedle–lens array (OMLA) to improve the efficiency and safety of PDT treatment. We designed and fabricated a novel optical microneedle–lens array with controlled dimensions to optimize light transmission. In addition, PS was coated uniformly over the tips of the OMLA using the dip coating method. Finally, we confirmed that the PS coated on the OMLA was released into the target area and subsequently generated radical oxygen by light irradiation. We expect that our proposed OMLA for PDT treatment can realize a new light-transmission platform optimized for PDT with targeting various types of skin cancers.Graphical abstract

Snapshot infrared Fourier transform imaging spectrometer for transient dynamic sensing

Imaging spectroscopy is an effective method for simultaneously acquiring the spatial information distribution and the spectral fingerprint characteristics of a target. Implementing dynamic target spectral mapping through optical scanning may lead to image artifacts and spectral interference. This paper proposes an innovative structure for a snapshot infrared Fourier transform Imaging spectrometer (SIFTIS), which utilizes a stepped micro-mirror and a lens array, combining the advantages of snapshot imaging spectroscopy and infrared spectral detection. The SIFTIS technology acquires a complete three-dimensional dataset within a single integration time, featuring good stability, strong real-time capability, and high spatiotemporal resolution. It has significant advantages in fields such as camouflage target recognition and harmful and pollutant gas measurement. Firstly, the optical field transmission model of SIFTIS was constructed, and the system's error propagation model was further deduced. The impact of the optical system and core optical components’ aberration residues and positional errors on spectral mapping were analyzed, providing design error tolerance. Subsequently, preliminary experiments combined with simulation analysis were used to calibrate and correct the spectral shifts caused by rotation, pitch, and roll component errors of the stepped micro-mirrors reflective surfaces at various levels. Finally, imaging spectral detection of dynamic plume targets was conducted to demonstrate the desired results and feasibility.

Light-field imaging device based on Fresnel lens array with composite microstructures

Light-field imaging device based on Fresnel lens array with composite microstructures

Liquid lenses for aerospace beam steering and communications: MOSAIC.

Laser communications (lasercom) can enable more efficient and higher bandwidth communications than conventional radio frequency (RF) systems, but requires more sophisticated pointing and tracking (PAT) systems to acquire and maintain links. Liquid lens arrays can provide compact, nonmechanical beam steering as an alternative to fast-steering mirrors and mechanical gimbals. An array of two liquid lenses offset in perpendicular axes along with a third on-axis lens in the array are used for beam steering and divergence control, respectively. The Miniature Optical Steered Antenna for Intersatellite Communications (MOSAIC) project applies liquid lens technology to create a transceiver for laser communications on spacecraft to enable wide field-of-view communications. This work provides analytical models of beam steering in order to inform subsystem sizing, and uses simulation studies along with previous work on space environment evaluation of liquid lenses to produce representative link budgets for a liquid lens based lasercom transceiver. A 25 Mbps link with 4 W transmit power at 1550 nm (optical C band) and 16-ary pulse position modulation (16-PPM) can be maintained up to 175 km separation with 3 dB margin, using larger pressure-actuated liquid lenses from Optotune arranged for hemispherical steering, potentially allowing for high speed optical links between formation flying swarms for applications such as interferometry.

Large-aperture liquid crystal lens array based on layered combined electrodes for 2D/3D switchable display.

This work proposes a large aperture liquid crystal lens array based on a novel layered combined electrode (LCE) structure. A large aperture (800µm) is achieved by strategically positioning pixel electrodes on either side of the LC lens and auxiliary electrodes at its center. This design effectively doubles the LC lens aperture compared to conventional structures, achieving this at a significantly lower voltage. Concurrently, the voltage applied to the auxiliary electrode is maintained at a lower level than the pixel electrode voltage to optimize the electric field distribution. To assess the operational efficiency of the proposed structure, a comparative simulation is conducted against a conventional model. Simulation results demonstrate that the proposed LC lens array achieves a remarkably short focal length of 2.2 mm at a low operating voltage (∼4.8Vrms). Compared with the method of enlarging the aperture by adding multiple auxiliary electrodes, the proposed LC lens array simplifies the electrode structure and thus reduces the electric field crosstalk between electrodes. Furthermore, this configuration enables seamless 2D/3D switching functionality.

Spatially Selective Imaging in Color: What You See is What You Want.

Spatially selective imaging (SSI) involves sampling a group of pixels from different positions on an encoded object to display a decoded image. Here, SSI is achieved by using off-axis cylindrical Fresnel lens arrays to decode multiple images from an encoded print of structural color pixels. Each image is optically retrieved by separately placing different "keys" (arrays of lenses in different pseudorandom configurations) over the same encoded print, and then each image is digitally reconstructed for visualization. In addition, a detailed analysis is presented on the designed lenses and pixels, which are all fabricated by two-photon polymerization lithography. Though Fresnel lenses are susceptible to chromatic aberrations, the results show that they can be used for imaging pixels that produce a wide range of colors at low numerical aperture (NA ≈0.2). The images have acceptable color contrast, corresponding to a simulated normalized modulation transfer function (MTF) of ≈0.6 averaged across wavelengths in the visible spectrum. This work can find applications in optical information security devices.

Millimeter Lens Array on Flexible Polymer for Lensing, Imaging and Bi-directional Beam Shaping Applications

Millimeter Lens Array on Flexible Polymer for Lensing, Imaging and Bi-directional Beam Shaping Applications

Histologic Effects of Fractional Lasers and Energy-Based Devices on Intradermally Injected Hyaluronic Acid Filler for Improving Skin Smoothness.

Prior studies have shown that energy-based devices (EBDs) over pre-injected hyaluronic acid (HA) fillers do not significantly affect clinical outcomes. However, the impact of EBDs over newly FDA-approved HA filler for improving skin smoothness is still undetermined. To evaluate the immediate histologic changes after various popular EBDs are performed over pre-injected, newly FDA-approved intradermal HA filler. Abdominoplasty skin was injected with HA superficially. Zone 1 was used as untreated control, while the other zones treated with the 755-nm picosecond laser with diffractive lens array, 1064-nm picosecond and 1064-nm Q-switched lasers, radiofrequency with insulated microneedles, volumetric directional thermal impact ultrasound (VDTI), and thermomechanical fractional injury (TMFI) devices. Histology shows HA in the superficial to mid dermis. Treatment with fractional Q-switched and picosecond lasers showed expected laser-induced optical breakdown in the epidermis and dermis. RF microneedling, VDTI, and TMFI devices caused thermal damage of collagen bundles with dermal dehydration. No immediate morphological changes to HA were noted following device treatment. However, the effect of heat-generating devices on the molecular integrity of HA fillers, which are composed of HA and water, remains uncertain.

Fiber-integrated hybrid achromatic microlenses by combined femtosecond laser 3D printing

Compact achromats for visible wavelengths are crucial for miniaturized and lightweight full-color endoscopes. Emerging femtosecond laser 3D printing technology offers new possibilities for enhancing the optical performance of miniature imaging lenses on fibers. In this work, we combine refractive and diffractive elements with complementary dispersive properties to create thin, high-performance hybrid achromatic lenses within the visible spectrum, avoiding the use of different optical materials. Using a fiber-integrated hybrid achromatic lens array, clear images are captured across different wavelengths. The fabrication process is carried out using femtosecond laser direct writing (DLW) assisted by femtosecond projection lithography based on a digital micromirror device (DMD). Our work is expected to significantly contribute to the advancement of integrated and miniaturized biomedical imaging devices.

Learned Multi-aperture Color-coded Optics for Snapshot Hyperspectral Imaging

Learned optics, which incorporate lightweight diffractive optics, coded-aperture modulation, and specialized image-processing neural networks, have recently garnered attention in the field of snapshot hyperspectral imaging (HSI). While conventional methods typically rely on a single lens element paired with an off-the-shelf color sensor, these setups, despite their widespread availability, present inherent limitations. First, the Bayer sensor's spectral response curves are not optimized for HSI applications, limiting spectral fidelity of the reconstruction. Second, single lens designs rely on a single diffractive optical element (DOE) to simultaneously encode spectral information and maintain spatial resolution across all wavelengths, which constrains spectral encoding capabilities. This work investigates a multi-channel lens array combined with aperture-wise color filters, all co-optimized alongside an image reconstruction network. This configuration enables independent spatial encoding and spectral response for each channel, improving optical encoding across both spatial and spectral dimensions. Specifically, we validate that the method achieves over a 5dB improvement in PSNR for spectral reconstruction compared to existing single-diffractive lens and coded-aperture techniques. Experimental validation further confirmed that the method is capable of recovering up to 31 spectral bands within the 429--700 nm range in diverse indoor and outdoor environments.

Resolution Improvement in Near-Virtual-Image-Mode Light-Field Display Using Resolution-Priority Technique

A light-field display with a near-virtual-image mode, which employs both a lens array and an aperture array, was previously proposed to provide a wide viewing zone angle and bright three-dimensional (3D) images. However, it is desirable to enhance its resolutions, which are presently equal to those of conventional displays. Thus, we proposed a technique for increasing the resolutions of 3D images generated by the light-field display with the near-virtual-image mode. The gap between the flat-panel display and lens array is reduced to decrease the magnification of the virtual images of the pixels and to enable the observation of multiple virtual pixel images through each lens. Further, we imaged the aperture array using the lens array to eliminate the gaps between the multiple pixels observed through adjacent lenses. We constructed a prototype display based on the proposed technique and verified the increase in the resolution of the prototype display compared to the original near-virtual-image light-field display.

Low-cost, high-volume, manufacturable 0.88 NA multi-wavelength diffractive lens array for optical document security

We design, manufacture, and characterize a high-numerical-aperture (NA=0.88, f/0.27), multi-wavelength (480 nm, 550 nm, and 650 nm) multilevel diffractive microlens array (MLA). This MLA achieves multi-wavelength focusing with a depth of focus (DoF) twice the diffraction-limited value. Each microlens in the array is closely packed with a diameter of 70 µm and a focal length of 19 µm in air. The MLA is patterned on one surface of a polymer film via UV casting, positioning the focal plane at the distal end of the polymer film. Each microlens focuses light at three design wavelengths into a focal spot with an estimated FWHM of ∼310nm. By placing this MLA directly on a standard high-resolution banknote print (minimum feature width of 10–15 µm), we demonstrate color-integral imaging for anti-counterfeiting. In contrast, refractive MLAs cannot achieve high-NA, multi-wavelength focusing or extended DoF. The extended DoF of our MLA ensures reliable performance despite variations in the polymer film’s thickness. Our MLA, produced via UV casting, enables extremely low-cost, high-volume production, making it ideal for flat optics in banknotes and document security.

Marketing Strategy Analysis of Three-dimensional Attitude and Angle Measuring Instrument

With long-standing defects in China's technology of the measuring instrument, there are many gaps in the market of measuring instruments. Under this background, as a tiny three-dimensional attitude angle measuring instrument based on a lens array, the three-dimensional attitude angle measuring instrument fills the drawbacks of many measuring instruments on the market. However, this product has not been put into the market on a large scale at present. Thus, it is critical to push this instrument into the market with suitable marketing methods. Firstly, this paper makes a concrete analysis of the instrument market. Then the possible problems of the three-dimensional attitude angle measuring instrument after entering the market are analyzed. On this basis, a solution is provided and the exclusive marketing strategy of a three-dimensional attitude angle measuring instrument is proposed.

Improving Viewing Angle Characteristics of Top-Emission Micro-Cavity OLEDs with Randomly Distributed Micro Lens Arrays

Improving Viewing Angle Characteristics of Top-Emission Micro-Cavity OLEDs with Randomly Distributed Micro Lens Arrays

3D OPC method for GLV parallel scanning lithography microstructure topography control based on SinCUT.

A 3D optical proximity correction (OPC) optimization method based on single image contrastive unpaired translation (SinCUT) is proposed for the precise fabrication of 3D microstructures in GLV parallel scanning digital 3D lithography. This method is applied to the optimized fabrication of hyperbolic micro-convex lens arrays. Its fabrication accuracy is demonstrated, showing a significant reduction in the mean square error (MSE) of the morphology. When the lens height is 8.5 µm, the average height error of the lens shape is less than 5%, and the MSE is reduced from 0.727 to 0.0329, resulting in a reduction rate of 92.79%.

Compact Partially End-Pumped Innoslab Laser Based on Micro-Cylindrical Lens Array Homogenizer

We demonstrate a compact, partially end-pumping Innoslab laser based on a micro-cylindrical lens array homogenizer. A dimension of 12 × 0.4 mm2 flat-top pumping line with a Gaussian intensity distribution across the line was simulated by the ray tracing technique. The rate equations considering the asymmetric transverse spatial distributions are theoretically developed. The simulation results are in good agreement with the experimental results. Preliminary data shows that for a pump power of 260 W, a maximum pulse energy of 15.7 mJ was obtained with a pulse width of 8.5 ns at a repetition frequency of 1 kHz. The beam quality M2 factors in the unstable and stable directions were 1.732 and 1.485, respectively. The technology has been successfully applied to temperature and humidity profiling lidar and ozone lidar and has been productized, yielding direct economic value.

Picosecond Alexandrite Laser With Diffractive Lens Array Combined With Long-Pulse Alexandrite Laser for the Treatment of Facial Photoaging in Chinese Women: A Retrospective Study.

Facial photoaging is a type of facial skin aging induced mainly by exogenous factors (ultraviolet radiation) and often manifests itself in the form of hyperpigmentation, telangiectasia, roughness, increase in fine lines/wrinkles, and enlarged pores. Recently, picosecond lasers have become an emerging option for the treatment of facial photoaging, and long-pulse alexandrite lasers (LPAL) have demonstrated promising potential in the treatment of photoaging-related symptoms. This study aimed to evaluate the efficacy and safety of picosecond alexandrite laser (PSAL) with diffractive lens array (DLA) combined with LPAL for facial photoaging. This is a retrospective study of 20 Chinese female patients with facial photoaging who received PSAL with DLA combined with LPAL during a 1-year period. All patients were treated every 4weeks for a total of three treatments. Objective indicators of facial photoaging and patient satisfaction were evaluated before each treatment, and pain scores and adverse effects were recorded after each treatment. Compared with baseline, patients showed significant differences in all facial photoaging indices (p<0.01). After receiving three treatments, there was a 20.1% decrease in the pigmentation index, a 23.9% decrease in the erythema index, a 34.5% decrease in the texture index, a 28.4% decrease in the fine lines index, a 56% decrease in the pore index, a 9.3% elevation and a 17.1% decrease in elasticity R2 and F4, respectively, and a 55% decrease in sebum content. The mean satisfaction score for the three treatments was 4.67 (3.33, 5.00), and the mean visual analogue scale (VAS) pain score was 7.00. No serious adverse effects such as post-inflammatory hyperpigmentation (PIH), hypopigmentation, or blistering were observed at the treatment site during the treatment period. PSAL with DLA combined with LPAL for the treatment of facial photoaging with significant efficacy, high patient satisfaction, and minimal adverse effects.

Self‐Assembled Biconvex Microlens Array Using Chiral Ferroelectric Nematic Liquid Crystals

AbstractRecently, it is shown (Popov et al, Sci. Rep, 2017, 7, 1603) that chiral nematic liquid crystal films adopt biconvex lens shapes underwater, which may explain the formation of insect eyes, but restrict their practical application. Here it is demonstrated that chiral ferroelectric nematic liquid crystals, where the ferroelectric polarization aligns parallel to the air interface, can spontaneously form biconvex lens arrays in air when suspended in submillimeter‐size grids. Using Digital Holographic Microscopy, it is shown that the lens has a paraboloid shape and the curvature radius at the center decreases with increasing chiral dopant concentration, i.e., with decreasing helical pitch. Simultaneous measurements of the imaging properties of the lenses show the focal length depends on the pitch, thus offering tunability. The physical mechanism of formation of the self‐assembled ferroelectric nematic microlenses is also discussed.

Conformal Ordered Solid–Liquid Coupled Piezoelectric Units for Programmable Adaptive Optics

AbstractOrdered piezoelectric units are designed to achieve unnaturally large strains and artificial vibrational modes, owing to the synergistic effects of multiple units. However, when interfacing with another physical field, the challenge for ordered piezoelectric units is to achieve precise control of individual unit independently while maintaining a large manipulation range. In this study, conformal ordered solid–liquid coupled piezoelectric units are introduced, which effectively reduce stress transfer by as much as 84% between units via incorporating a liquid phase into each unit. This design allows for the generation of considerable strain levels (up to ɛZ = 1.13%) when used with a flexible layer and optimized structure. Hence, these conformal ordered piezoelectric units achieve simultaneous production of large strains and independent electromechanical control for each individual unit. As a practical illustration, a biomimetic piezoelectric adaptive lens and a lens array based on solid–liquid coupled piezoelectric units are designed and fabricated. They offer an extensive zoom range from 100.3 mm to infinity, ultra‐high diopter sensitivity of 70 D mV−1, ultra‐rapid response time of 50 µs, and programmable optical focusing through individual manipulation of each unit. This research paves the way for inspiring new designs for piezoelectric metamaterials and devices for intelligent electromechanical systems.

Bioinspired ultrathin photonic color convertors for highly efficient micro‐light‐emitting diodes

AbstractPixelated color convertor plays an immensely important role in next‐generation display technologies. However, the inherent randomness of light propagation within the convertor presents a formidable challenge to reconcile the huge contradiction between excitation and outcoupling. Here, we demonstrate a bioinspired photonic waveguide pixelated color convertor (BPW‐PCC) to realize directional excitation and outcoupling, which is inspired by an insect visual system. The lens array of BPW‐PCC enables a focusing photonic waveguide that guides the excitation light and converges it on colloidal quantum dots; the directional channel provides a splitting photonic waveguide to enhance the outcoupling of photoluminescence light. Consequently, the excitation and outcoupling efficiency can be simultaneously improved at this judiciously designed pixelated color convertor with a thickness of 50 μm. By this strategy, ultrathin BPW‐PCCs with 4.4‐fold enhanced photoluminescence intensity have been demonstrated in micro‐light‐emitting diode devices and achieved a record‐high luminous efficacy of 1600 lm W−1 mm−1, opening a new avenue for efficient miniaturized displays.