Molded Lenses Research Articles

Machine learning and design of experiments for optimizing laser-engraved micro fresnel lens mould

This research examines the application of Laser Engraving to produce micro Fresnel Lenses on aluminum plates, a novel application of this non-conventional machining method. The research explores the effects of the scan speed, laser power with number of cycles on the roundness deviation using a L9 orthogonal array. Multiple analytical methods, including the Taguchi method, Random Forest Algorithm with sensitivity analysis, are employed to optimize process and predict the outcomes. In this study, a thorough analysis of the fabrication of a micro Fresnel lens on Aluminum plate (10 mm × 10 mm × 2 mm) using fiber laser of wavelength 1064 nm is presented. The study finds that laser power has most significant effect on the roundness deviation, followed by the number of the cycles and scan speed. Scan Speed ranges from 500 to 700 mm s−1, the Power ranges from 25 to 35 Watts, and the Number of Cycles ranges from 100 to 200. Optimal conditions are identified as 700 mm/s scan speed, 25 W power, and 100 cycles. Microscopic analysis confirms roundness deviation under these conditions. Comparisons between analytical approaches and experimental results reveal that both the Taguchi method and Random Forest Algorithm align closely with experimental outcomes, with the Random Forest Algorithm showing slightly higher accuracy (6.18 percentage points closer to experimental results). This research addresses a gap in comparative studies evaluating traditional statistical methods against modern machine learning algorithms for process optimization in laser machining. It combines knowledge from optics, materials science, and laser machining, utilizing advanced methods and technologies that have only recently become accessible. The findings provide valuable insights for future applications of micro Fresnel lenses on aluminum plates and contribute to the understanding of laser engraving processes for precision optical components. Between the Random Forest Algorithm and the Taguchi method, Random Forest Algorithm fits more closely to the experimental result. Random Forest Algorithm prediction is closer to experimental result by about 6.18 percentage points compared to the Taguchi method prediction.

Co-delivery of Brinzolamide and Timolol from Micelles-laden Contact Lenses: In vitro and In Vivo Evaluation.

Traditional eye drops exhibit a modest bioavailability ranging from 1 to 5%, necessitating recurrent application. Thus, a contact lens-based drug delivery system presents substantial benefits. Nonetheless, pharmaceutical agents exhibiting poor solubility may compromise the quintessential characteristics of contact lenses and are, consequently, deemed unsuitable for incorporation. To address this issue, the present study has engineered a novel composite drug delivery system that amalgamates micellar technology with contact lenses, designed specifically for the efficacious conveyance of timolol and brinzolamide. Utilizing mPEG-PCL as the micellar material, this study crafted mPEG-PCL micelles loaded with brinzolamide and timolol through the film hydration technique. The micelle-loaded contact lens was fabricated employing the casting method; a uniform mixture of HEMA and EGDMA with the mPEG-PCL micelles enshrouding brinzolamide and timolol was synthesized. Following the addition of a photoinitiator, 50 μL of the concoction was deposited into a contact lens mold. Subsequently, the assembly was subjected to polymerization under 365 nm ultraviolet light for 35 min, resulting in the formation of the micelle-loaded contact lenses. In the present article, we delineate the construction of a micelle-loaded contact lens designed for the administration of brinzolamide and timolol in the treatment of glaucoma. The study characterizes crucial properties of the micelle-loaded contact lenses, such as transmittance and ionic permeability. It was observed that these vital attributes meet the standard requirements for contact lenses. In vitro release studies revealed that timolol and brinzolamide could be gradually liberated over periods of up to 72 and 84 h, respectively. In vivo pharmacodynamic evaluation showed a significant reduction in intraocular pressure and a relative bioavailability of 10.84 times that of commercially available eye drops. In vivo pharmacokinetic evaluation, MRT was significantly increased, and the bioavailability of timolol and brinzolamide was 2.71 and 1.41 times that of eye drops, respectively. Safety assessments, including in vivo irritation, histopathological sections, and protein adsorption studies, were conducted as per established protocols, confirming that the experiments were in compliance with safety standards. The manuscript delineates the development of a safe and efficacious micelle-loaded contact lens drug delivery system, which presents a novel therapeutic alternative for the management of glaucoma.

Fabrication and Characterization of Automotive Aspheric Camera Lens Mold based on Ultra-precision Diamond Turning Process

Fabrication and Characterization of Automotive Aspheric Camera Lens Mold based on Ultra-precision Diamond Turning Process

Revolutionizing contact lens manufacturing: exploring cutting-edge techniques and innovations for enhanced vision and comfort

Abstract This review paper delves into the advancements and innovations revolutionizing contact lens (CL) manufacturing, focusing on techniques and technologies aimed at improving vision quality and wearer comfort. The article begins by tracing the evolution of CL fabrication techniques, paying homage to Leonardo da Vinci’s early contributions. It then discusses traditional methods such as lathe-cutting, spincasting, molded lens fabrication, and the recent advent of 3D printing in CL production. The review further explores advanced CL designs, including spherical, aspheric, toric, and bifocal/multifocal CLs, highlighting their specific applications and benefits. Material innovations in lens manufacturing are examined, with an emphasis on silicone hydrogel CL, hybrid lenses combining different materials, and the development of biocompatible and gas-permeable (GP) materials. Evaluation of optical design efficiency is another crucial aspect covered in this paper, encompassing visual acuity, contrast sensitivity, through-focus curves, reading performance, peripheral refraction, and patient-reported outcomes for quality of vision. Additionally, the role of nanotechnology and surface modifications in enhancing lens properties is explored, along with advances in lens coating and surface treatments, including antimicrobial and UV protection coatings. Nanocomposites of polymethyl methacrylate (PMMA) and TiO2 showed refractive indices between 1.52 and 1.59, while combining TiO2 NPs with poly(2-hydroxyethyl methacrylate) (PHEMA) yielded values ranging from 1.47 to 1.53. PGMA-TiO2 nanocomposites exhibited refractive indices between 1.47 and 1.50. Furthermore, nanocomposites of PVP-PVA-Ag with silver (Ag) NPs achieved higher refractive indices within the range of 1.45 to 1.49. This article concludes by discussing the challenges and future directions in CL manufacturing, focusing on addressing lens discomfort, improving oxygen permeability and moisture retention, and enhancing manufacturing efficiency and scalability. Overall, this review offers valuable insights into the cutting-edge techniques and innovations transforming CL production and paving the way for improved vision correction and wearer satisfaction.

Effect of non-contact preheating on fog spots of molded infrared lenses

Effect of non-contact preheating on fog spots of molded infrared lenses

Inhomogeneous thermal analysis of microlayer mold for glass molding of fast-axis collimation lens array

Fast-axis collimation (FAC) lens arrays play a crucial role in laser systems, offering precise beam shaping and focusing for applications such as laser marking, and optical communication. Achieving high precision in these applications requires a FAC lens array with a long Rayleigh range. While precision glass molding with nickel-phosphorus (Ni-P) microlayer molds has revolutionized the mass production of FAC lens arrays, the extreme conditions during the molding process can lead to poor profile accuracy. To address this issue, we developed an optical collimation system to derive the final characteristic parameters and obtain the beam waist radius and Rayleigh range of the collimated laser. Additionally, we conducted a thorough analysis of the inhomogeneous thermal expansion process of the microlayer mold and established a mathematical solution for thermal compensation to modify the mold's shape. We validated the proposed method by fabricating an FAC lens array mold and measuring the profile error and waist radius of a molded FAC lens array. We also calculated the profile error of this method using a finite element (FE) model in ABAQUS. The results indicate that incorporating the inhomogeneous thermal expansion reduces the shape error of the FAC lens array from 0.577 μm to 0.135 μm. Moreover, using inhomogeneous thermal compensation significantly improves the Rayleigh range of the FAC lens array from 1.285 μm to 9.8 × 104 μm.

Analysis on the instability of the surface profiles of precision molding chalcogenide glass aspherical lenses in mass production.

Chalcogenide glass lenses have been widely applied in infrared optical systems for their outstanding optical performance. It is a tendency for complex optical glass elements to be mass-produced with precision glass molding (PGM) technology, of course including chalcogenide glass aspheric lenses. But there is a problem that sometimes the surface profiles of the molded lenses are unstable which leads to a low pass-yield. Precision glass molding experiments and finite elements simulations are carried out to study the reasons for the mentioned problem in this paper. The results reveal that the laying error of the ball chalcogenide glass preform does not have a significant effect on the surface profile of the molded lens. However, in mass production the control of the temperature after forming stage in the PGM process is very important for obtaining the molded lenses with very similar surface profiles. The research results could help relevant researchers design the PGM processing parameters to overcome some errors in the mass production and manufacture precision glass molding machines. The increase in the yield of complex optical glass elements fabricated by PGM technology will further promote the application of such elements in various fields.

Effect of preform shape on formability and internal stress for glass molded concave meniscus lens

Effect of preform shape on formability and internal stress for glass molded concave meniscus lens

Simulation of the Refractive Index Variation and Validation of the Form Deviation in Precisely Molded Chalcogenide Glass Lenses (IRG 26) Considering the Stress and Structure Relaxation.

Precise infrared (IR) optics are core elements of infrared cameras for thermal imaging and night vision applications and can be manufactured directly or using a replicative process. For instance, precision glass molding (PGM) is a replicative manufacturing method that meets the demand of producing precise and accurate glass optics in a cost-efficient manner. However, several iterations in the PGM process are applied to compensate the induced form deviation and the index drop after molding. The finite element method (FEM) is utilized to simulate the thermomechanical process, predicting the optical properties of molded chalcogenide lenses and thus preventing costly iterations. Prior to FEM modelling, self-developed glass characterization methods for the stress and structure relaxation of chalcogenide glass IRG 26 are implemented. Additionally, a ray-tracing method is developed in this work to calculate the optical path difference (OPD) based on the mesh structure results from the FEM simulation. The developed method is validated and conducted during the production of molded lenses.

Fabrication of high aspect-ratio aspheric microlens array based on local spiral diamond milling

Ultraprecision mold machining combined with precision glass molding is the most promising technology for the mass production of glass microlens arrays (MLAs). However, fabricating an MLA with a high aspect-ratio (AR) (ratio of height to aperture), submicron scale profile accuracy, nanoscale surface finish, and good consistency remains a considerable challenge. A local spiral diamond milling (LSDM) method is proposed to generate a high AR MLA on a nickel-phosphorous (Ni-P) plated mold. A spiral toolpath generation algorithm that considers the tool edge radius and performs profile error (PV) compensation is developed. Each lenslet at any local position can be precisely machined by controlling the servo motions of the three translational axes. Then, the entire MLA can be generated by shifting the toolpath to go through the centers of all lenslets according to the MLA layout. The tool parameters are optimized to avoid local and global tool interference during machining. The generated toolpath provides steady slide axis movements to avoid dramatic changes in cutting speed and acceleration. An MLA with an AR of 0.166 is fabricated. The results show that the fabricated mold and the molded lenses have a profile accuracy (PV) of less than 1 μm and a surface roughness (Ra) of less than 14 nm. The cross-sectional profiles indicate that the fabricated MLA has high machining consistency.

Microscale surface texturing on nonplanar surface of diffusion lens for anti-glare LED light

In this study, we present the fabrication technique and characterization results of a concave-bottom rod lens (CB-RL) covered with microstructures to diffuse the Light-emitting diode (LED) light for anti-glare. The spherical concave bottom of the rod lens was designed based on a basic refraction theory and was fabricated by using the hyper-elastic deformation characteristics of polydimethylsiloxane film to form microstructures on the nonplanar surface. The rod lens mold and microstructure mold were prepared via the metal cutting process and photoresist reflowing process, respectively. In the experimental study, a CB-RL with and without microstructures was fabricated and compared. A CB-RL mounted on an LED effectively changed the isomeric luminous intensity profile into a batwing-shape profile. The reduction in discomfort glare induced by a single LED was characterized by comparing the uniformities of the luminous intensity between the bare and proposed lens-mounted LEDs. The full width half maximum (FWHM) value of the luminous intensity was increased from 50.9% to 71.4%, and the maximum-to-minimum ratio of the luminous intensity was reduced from 3.91 to 1.94. For a light bulb consisting of eight LEDs, the FWHM value and maximum-to-minimum ratio of the luminous intensities were improved from 38.0% to 55.0% and from 10.96 to 6.96, respectively.

Release characteristics of a high-hardness DLC coating on an aspherical glass lens mold

In this paper, we investigated the changes in the shape precision of a diamond-like carbon (DLC)-coated surface of an aspherical glass lens mold. The press molding process of the experiment involved placing a bulk material made of glass in an ultra-precision mold and applying cylinder pressure at a high temperature. Thermally stable tungsten carbide was used as the mold material. DTM grinding with a resolution of 0.1 [Formula: see text]m was performed to precisely process the tungsten carbide aspherical lens mold. HiPIMS–DLC and ta-C DLC coatings having excellent anti-stiction and hardness were applied on the polished mold. The hardness of the thin film was measured using nanoindentation. For the composition of the DLC, the [Formula: see text]/[Formula: see text] peak values were detected through Raman spectroscopy. Furthermore, the friction coefficient of the DLC thin film was measured using a tribology tester, and the friction coefficients of HiPIMS–DLC and ta-C were 0.018 and 0.014. Using FTS measurements, we confirmed that the precision of the aspherical lens shape (Peak to Valley) of the aspherical lens was 1.5 [Formula: see text]m and 0.5 [Formula: see text]m, respectively.

ELID Mirror Surface Grinding for Concave Molds by Conductive Elastic Wheel Containing Carbon Black

Elastic grinding wheels have previously been adopted for the development of the mirror surface finishing method for concave spheres. In this study, new conductive elastic grinding wheels, to which electrolytic in-process dressing (ELID) can be applied, are developed; the aim of the study is to address the challenge of maintaining a constant removal rate for rubber bond wheels. When ELID grinding is performed using a non-diene (isobutane isoprene rubber, IIR)-based wheel, a larger removal amount is achieved, and a higher-quality surface is also achieved compared to a diene (acrylonitrile-butadiene rubber, NBR)-based wheel. In addition, to investigate the effect of grinding wheel bond hardness on the removal amount and ground shape accuracy, grinding wheels with various levels of hardness are prepared by controlling the amount of carbon black contained in them, and grinding experiments are conducted. Thus, a larger removal amount is achieved using a harder grinding wheel, but the roughness of the ground surfaces deteriorates. Therefore, in practice, it is necessary to select an appropriate grinding wheel that can achieve both productivity and surface quality. Finally, to obtain a high-quality mirror finish on a concave spherical surface, ELID grinding is performed on the workpieces as is done for spherical lens molds. Thus, high-quality mirror surfaces with roughness Ra < 10 nm were generated. When the work pieces are ground using a grinding wheel of the same radius, excessive removal occurs at the edge of the concave spherical profile, decreasing the form accuracy. Numerical simulation demonstrates that chamfering of the grinding wheel is effective for improving the shape accuracy. The results of this study are expected to contribute to automation and cost reduction in the mirror-finishing process for concave molds.

Correction of temperature influences on plastic lenses for applications in laser material processing

Today, the use of plastic lenses in processing optics for laser material processing is fundamentally limited to laser powers lower than 1 W. This is due to thermo-optical effects in the plastic material which primarily lead to a shift in the focus position. To overcome this laser power limitation, a design routine was developed for injection molded lenses, which simulates the optical properties of the lens in thermal equilibrium state during laser irradiation and which iteratively adapts the lens design for the manufacturing process in this way that the lens is compensated for thermal effects and manufacturing errors like shrinkage. The approach is demonstrated for an injection molded focusing lens used at an average laser power of 15 W. The focusing properties of the compensated manufactured lens are compared with the underlying simulations as well as with an uncompensated lens geometry used at the same laser power.

Analysis of lens fracture in precision glass molding with the finite element method.

Precision glass molding (PGM) technology has recently emerged as a promising fabrication method for mass-fabricating optical glass lenses with complex surfaces. However, lens fracture as a common problem has not been analyzed in detail. In this paper, the divergent cone cracks in the molded lens were analyzed using the finite element method, because crack propagation cannot be seen in the molding process. A three-dimensional model was established in MSC Marc software for analyzing the temperature, stress components, and principal stress of the glass in different molding stages. The crack paths were analyzed using the simulation results and the fracture basis. Based on the analysis, PGM experiments with different processing parameters were carried out. The appearance of the molded lenses demonstrated the rationality and correctness of the analysis. Thus, analyses of other types of lens fractures can use the analysis method proposed in this paper rather than relying on trial and error.

Three-dimensional measurement for spherical and nonspherical shapes of contact lenses.

In recent years, with the development of precise lathe-cutting equipment, special shaped contact lenses (CL) have been crafted. However, while it is possible to manufacture such a lens, its shape evaluation has not been well-established. We conducted a basic optical experiment using special lenses to measure a spherical lens and nonspherical mold. As the measurement sample, a metal ball, special CL, and a toric-shaped mold were adopted. In order to accurately measure those real shapes, we proposed an algorithm in which the probe light is vertically incident to the sample surface within a numerical aperture of the optical probe. For this algorithm, we developed the specialized time-domain optical coherence tomography (TD-OCT), which was designed to conduct circular scanning while maintaining vertical incidence by driving a two-axis (vertical and horizontal) micro-electromechanical system mirror with a phase difference of 90°. The shape, thickness distribution, and curvature radii of both front and back surfaces of a CL were estimated with this OCT signal analysis and sphere fitting. The shape and curvature radius were evaluated by using the simulated data under the same experimental conditions. They were sufficiently accurate based on the resolution of this OCT. Also, a toric-shaped mold was evaluated by comparing the relationship between each coordinate and intensity of the interference signal. As a result, it is confirmed that the experimental result and the simulated matched well.

Is soft toric contact lenses fitting a feasible option to improve optical quality and visual performance in corneal ectasia?

ObjectivesTo assess the feasibility of fitting soft toric contact lenses (STCL) in corneal ectasias and their impact on optical quality and visual performance. MethodsA total of 22 eyes were fitted with a molded STCL: 11 eyes/9 subjects with corneal ectasia and 11 healthy eyes/11 subjects. Wavefront aberrations were analyzed using a Hartmann-Shack aberrometer. Visual performance was measured under photopic (85 cd/m 2) and mesopic (≤3 cd/m 2) conditions. High-(96 %) and low- (10 %) contrast VA (HCVA and LCVA respectively) were assessed using the ETDRS charts and contrast sensitivity (CS) using the Pelli-Robson chart. ResultsAfter STCL fitting in the ectatic corneas, oblique astigmatism increased 0.15±0.17 μm and 0.34 ± 0.36 μm for 3 mm- and mesopic pupil diameters, respectively.Mean defocus decreased 1.41 ± 0.36 μm and 2.17 ± 0.85 μm for the same pupil diameters. More positive values of vertical coma were found with a change of 0.05 ± 0.06 μm and 0.12 ± 0.10 μm for 3 mm and mesopic pupil diameters, respectively. Comparing changes between both groups, with a 3 mm pupil aperture, statistically significant differences (p < 0.05) were detected in oblique astigmatism, defocus, vertical secondary trefoil and horizontal secondary coma. In the group with corneal ectasia, photopic HCVA and LCVA improved 0.09 ± 0.11 logMAR and 0.12 ± 0.15 logMAR respectively. In mesopic conditions, HCVA, LCVA and CS improved 0.11 ± 0.12 logMAR, 0.18 ± 0.15 logMAR and 0.11 ± 0.07 log. units, respectively. ConclusionsThe analyzed molded soft toric contact lens is a feasible option for good vision in corneal ectasia with moderate irregularity and negative vertical coma.

A Study on the Release Characteristics During Wafer-Level Lens Molding Using Thermosetting Materials

A Study on the Release Characteristics During Wafer-Level Lens Molding Using Thermosetting Materials

Hot embossing of aspherical Fresnel microlenses: design, process, and characterization

Hot embossing is a technique used to fabricate high-precision and high-quality polymeric components that combines low costs with high aspect ratio fidelity replication. In this study, we manufactured two aspherical Fresnel molds employing the single-point diamond turning process on an electrolytic copper workpiece, one with 10 μm constant height 30 zones and the other with 250 μm constant width 40 zones. The micromachined mold reproduced PMMA convex-plane lens optical quality replicas through the micro hot embossing technique. We used a scanning electron microscope (SEM), spectrophotometry, and non-contact optical profilometer to evaluate the replication fidelity qualitatively: the lens mold and the fine three-dimensional microstructures on the PMMA substrate surfaces. The results of the surface finish of the diamond machined mold sample are in the range of 4.92 nm (areal average surface roughness Sa) and 6.04 nm (areal root-mean-squared roughness Sq), respectively, and the values for the replicas being 4.73 nm and 5.94 nm, respectively. The results demonstrated that the geometry form accuracy obtained of the microfeatures was at the submicron level with little viscoelastic recovery. The surface roughness in the nanometer level got successfully replicated.

Effect of preform shape on formability and residual stress for glass molded concave meniscus lens

Effect of preform shape on formability and residual stress for glass molded concave meniscus lens