Molded Lenses Research Articles

One-step transfer of diffractive structure from a designed pattern to a replica by use of a hybrid solgel film

A one-step method for microfabrication of a diffractive lens mold with continuous relief, including a solgel process for replication, is presented. The mold is fabricated by focused ion beam milling (FIBM) on a substrate of bulk silicon and is then used directly for replication of the diffractive structure by means of a hybrid solgel glass stamping process. The surface roughness of the replica, Ra, is 4 nm over a 5 m x 5 m area. The measured diffraction efficiency is 86% and is influenced by accumulated mold geometry and solgel process errors. The demonstrated process of direct stamping by use of the master fabricated by FIBM offers the potential for mass production at very low cost.

213 多機能マイクロマシニングシステムによる非球面レンズ金型の創成

In order to meet the demands of high integration in electronic and optical applications, mechanical micro-machining technology [1,2] has been progressing rapidly in recent years for its 3D accessibility to a variety of materials. Newly developed in this research is a multifunctional machining system capable of micro- milling, turning, grinding, buffing, polishing, EDM, ECM, laser machining and their combinations. This paper reports design and development of the system and its application in micro lens mold fabrication.

Dwell time algorithm for computer-controlled polishing of small axis-symmetrical aspherical lens mold

SAMSUNG Electronics Co.Opto-Mechatronics LabDigital Media R&D Center416 Maetan-3Dong, Paldal-GuSuwon City, Kyungki-DoKorea 442-742E-mail: hocheol@samsung.comMinyang YangKorea Advanced Institute of Science andTechnologyDepartment of Mechanical Engineering373-1 Kusong-dong, Yusong-guTaejonKorea 305-701E-mail: myyang@kaist.ac.krAbstract. We describe a dwell time algorithm for the polishing of smallaxis-symmetrical aspherical surfaces. The dwell time distribution of thescanning polishing tool on the rotating workpiece is calculated to reducethe residual surface error. The dwell time at each discrete grid is calcu-lated as an integer multiple of the workpiece rotation period, which isalso useful for the spatially varying case in the local polishing area. Aspherical polyurethane tool with abrasives is adopted for a computer-controlled polishing process. A linear algebraic equation of removaldepth, removal matrix, and dwell time is derived by convolution of theremoval depth at the dwell positions. The nonnegative least-squaresmethod gives a solution to minimize residual error. Parametric effectssuch as the dwell grid interval are simulated. Finally, an experiment fortool mark removal is performed and the dwell time algorithm is evaluatedto be valid.

Novel one-step method of microlens mold array fabrication

We present a novel method for fabricating micro- lens mold arrays. The mold array is fabricated using focused-ion-beam milling (FIBM) on a substrate of bulk SI. The 2-D profiles and surface roughnesses of the fabricated molds are measured using a laser interferometer. Finally, the mold array is used for hot embossed molding. The surface roughnesses of the mold and the replica are 2.5 and 8 nm, respectively. We define surface roughness as the arithmetic mean of the absolute departure of the roughness profile from the mean line. A profile of the replica is acceptable for prac- tical use. The measured size of the replica corresponds well with that of designed array. © 2001 Society of Photo-Optical Instru-

A statistical experimental study of the injection molding of optical lenses

In the injection molding of plastic optical lenses, the processing conditions have critical effects on the quality of the molded lenses. Since there are many process parameters involved in an injection molding process, and more importantly, an optical lens needs precisely controlled surface contours, determination of the processing conditions for lens molding is very complicated. The objective of this work is to investigate experimentally some effects of the molding conditions on the surface contours of injection molded lenses. A spherical lens was molded using polycarbonate. The surface profiles of the lenses molded under different processing conditions were measured using a laser interferometer. The birefringence of the lenses was measured using a specially designed polarimeter to characterize the residual stress in the lenses. Statistical methods were employed in the experimental studies in order to systematically analyze the effects of various process parameters on the lens contour errors. The process parameters studied include injection speed, holding pressure and mold temperature, etc. The contour errors were correlated to the mold shrinkage and the residual stress in the molded lenses. The study shows that in addition to the mold shrinkage the stress also plays a vital role in determining the lens surface contours.

Micro-Spherical Lens Mold Fabrication by Cup-Type Metal-Bond Grinding Wheels Applying ELID (Electrolytic In-Process Dressing)

Micro-Spherical Lens Mold Fabrication by Cup-Type Metal-Bond Grinding Wheels Applying ELID (Electrolytic In-Process Dressing)

Two Novel Applications of Adhesives for Optical Microelectronics

Most of HEI’s custom and standard optical switches require one lens to focus light from an LED and another to collect and concentrate that light onto a photoelectric diode. Plastic lenses are typically glued into apertures in polycarbonate housings using a two ‐part room temperature cured adhesive. To reduce cost and increase productivity, lenses are fabricated in the apertures using an ultraviolet cured clear adhesive. This process eliminates the cost of moulded plastic lenses and reduces cure time from 24 hours to less than a minute. One of the custom optical applications requires bonding a coated glass cover over a cavity containing optical sensors and circuitry. Gas expansion causes ‘blow‐outs’ when heat cured adhesives are used and room temperature cured adhesives add a day to turnaround time. An ultraviolet cured adhesive increases productivity by eliminating blow‐outs and reducing turnaround time. A unique process has been developed in which the glass cover is placed over the cavity in a vacuum bell jar.

Polymer microlens arrays

The manufacture and study of micro-optics has developed into a major topic area as lasers have penetrated telecommunications, information technology and audio-visual services. Microlens arrays can be both high volume and high value articles. After reviewing the topic of microlenses made in both inorganic and plastic materials, this paper describes a new and inexpensive technique of hot pressing for converting a sheet of polymer into one that contains a high quality lens array. The technique is particularly appropriate for lens diameters of about 1-2 mm, where current technologies are either not applicable or prohibitively expensive for trial devices. The optical performance of polycarbonate lens arrays made by this method is compared to presently available moulded plastic lenses of comparable dimensions.

非球面プラスチックレンズ金型の樹脂収縮変形補正に関する一手法

非球面プラスチックレンズ金型の樹脂収縮変形補正に関する一手法

22 dB gain semiconductor optical amplifier module using high numerical aperture aspheric lenses

A polarisation-insensitive semiconductor optical amplifier (SOA) module with a net gain of 22 dB is demonstrated. High numerical aperture, low aberration aspheric glass moulded lenses are efficiently used for optical coupling between the SOA chip and singlemode fibres.

Low-loss laser diode module using a molded aspheric glass lens

The fabrication and characteristics of a 1.3- mu m laser diode (LD) module for single-mode fiber using a molded aspheric glass lens is discussed. An average coupling loss of 2.2 dB with a standard deviation of less than 0.5 dB after thermal heat cycling tests was achieved. The average assembly loss was 0.24 dB. The LD module demonstrated stability during thermal and heat cycling tests from -10 to 60 degrees C. >

Low-wavefront aberration and high-temperature stability molded micro Fresnel lens

A high-diffraction efficiency (>50%), small lens diameter (0.5 mm phi ), short focal length (1 mm), and thin (0.25 mm) molded micro Fresnel lens suitable for compact optical devices is discussed. The device is fabricated by means of a photopolymerization process using a UV-curable resin. By adopting glass as the substrate, low-wavefront aberration ( >

Development of the gas‐permeable impression‐moulded scleral contact lens

Although superceded by corneal hard and soft contact lenses for the correction of simple refractive error, the scleral lens still has numerous medical applications in modern ophthalmological practice. However, a major problem with scleral lenses has been the limited wearing time due to corneal occlusion and consequent hypoxia. We present two alternative methods for the production of moulded gas permeable scleral contact lenses.

Plastics Lens Molding by Vibro-Thermoforming

This paper describes a new method of manufacturing plastic lenses. Injection molding is the process usually employed to produce plastic lenses. In spite of its popularity, this method presents some problems such as long molding times, adverse optical influence due to molecular orientation near the gate zone and the high cost of the mold. In order to solve these problems, we have developed a new technique to manufacture plastic lenses-called Vibro-Thermoforming-which is a derivation of Vibro-Punching. This is based on a reciprocating half-blanking process with a concentration of thermal energy produced by local deformation. Lenses are then formed from the thermo-softened material. This process can be used for manufacturing lenses from PMMA sheets in 31.5 seconds. The interference fringe number is about 0.3, the resulting surface roughness in Rmax is 0.04μm and the birefringence index is approximately the same as for injection molding.

プラスチックレンズ成形形状歪みの有限要素法解析

射出圧縮成形で製造されるプラスチックレンズの成形状歪み (ひけ, そり) を解析した. 成形過程における成形収縮開始時点を, 樹脂が冷却され, 圧縮圧力に対して塑性変形不可能となり樹脂補給が絶える時点と定めた. 解析手順は非定常温度解析. 成形収縮開始時点を求めるための固相領域の成長過程の計算, ならびに熱応力歪み解析からなる. 温度解析と熱応力歪み解析を有限要素法で行ったので, ひけとそりを合成した形で成形形状歪みが求められる. 凹レンズと凸レンズの例にっいて, 実験結果と計算結果の比較を行い満足しうる一致を得た.

Design and performance of a small—scale diamond turning machine

Machining with single-point diamond tools is an area of increasing interest in the manufacture of optics, lens moulds, hard discs and other products Although many materials have been machined with impressive results, questions remain regarding the science of diamond turning. These questions concern the suitability of certain materials for turning, the properties of the tool and machine structure which limit the quality of the final product, and the modelling of the cutting process. To study these phenomena, a laboratory-scale diamond turning machine has been designed and built at the Precision Engineering Center. This machine, PAUL, although simple and compact, has produced excellent results on a variety of static and dynamic cutting experiments. The key points of its design, as well as an evaluation of PAUL's performance, are given in this paper.

Lens and Optics for Optical Disk System

Various types of pick-up lenses and optical systems for pick-ups are discussed. We evaluated optical performances of objective lenses. Aspherical lenses for CD player pick-ups have wider field angle compared to the conventional triplet objective lens. We also evaluated reliability of both plastic and glass molded lenses which are designed in the same way. Plastic lens caused spherical aberration due to temperature change. Optical pick-ups for CD players are remarkably simplified by means of aspherical lens or holographic element. On the other hand, pick-ups for write once or erasable optical disk system consist of many optical components. For these pick-ups, we developed a single bi-aspheric molded glass lens which has high NA (0.55) and remarkable light weight (85mg).

Method for Quantitative Evaluation of Corneal Shape Changes by Contact Lens Molding

Method for Quantitative Evaluation of Corneal Shape Changes by Contact Lens Molding

Optical performance of a diffraction-limited molded-glass biaspheric lens

Optical performance results are reported for a molded-glass biaspheric lens. The 6-mm optical diam lens is intended for use in a laser-based optical disk application. The design with fabrication tolerances has an expected on-axis transmitted wave-front performance of 0.06-wave rms optical path difference (OPD) when tested at 0.6328 ,4m and a numerical aperture of 0.45. Transmitted wave-front aberrations were measured on actual molded lenses using a heterodyne interferometer. Typical performance was 0.05-0.08-wave rms- OPD. Experimental results involving mold rotation indicate that lens performance is primarily limited by a surface figure accuracy of one of the molds.

The design of the back surface ofgas permeable lenses

The introduction of gas permeable contact lenses into general practice has opened up a new era for practitioners, and the advantages over hard PMMA and soft lenses are well documented. For many new patients it will be quite possible to fit the standard hard lens designs which are favoured by the individual practitioner. However, for those wearers who subsequently suffer from flare, lens instability or lid irritation it is necessary to consider lenses with larger back central optic diameters and/or overall size and less edge lift. Similarly the soft lens wearer who is having to be refitted with a hard type lens will prefer immediate flare free stable vision which is not always immediately available with the standard hard lens constructions. In order to fulfil these requirements there have been several new designs offered for gas permeable lenses. To date these have received a mixed reception from practitioners and it is the purpose of this paper to compare these designs with the familiar PMMA constructions and offer new constructions which practitioners may find useful as an adjunct to those already available. Historically the initial interest with gas permeables goes back to CAB, but the lack of stability of lathe cutting reduced the effectivity of the material and forced us to consider moulded lenses such as the Hartflex from Wohlk. The edge lift of these lenses is, however, as little as 0.045mm, to 0.06ram,' and when fitted in the standard British fashion would lead to a very tight lens although giving often an amazing amount of tear interchange. Satisfaction is only really obtained utilizing a flatter than 'K' approach or by adding a flat edge curve about 0.5mm wide and blended into the lens periphery. The second lens introduced, the Menicon 02 works in a similar fashion. The lens like the Hartflex has a very reduced edge lift, varying from 0.06mm on steeper radii. These figures the manufacturers will not vary. Fitting this lens with apical clearance gives absolutely no edge lift, but fitted 0.15mm flatter than 'K' as suggested by the manufacturers means again we depart from conventional methods of fitting. At the same time as these lenses were introduced to Great Britain a similar investigation was being undertaken by Williams in the USA 2. He designed for the Syntex Corporation two series of lenses made from Polycon. The first set of lenses (Table 1) had an overall size of 9.50mm with a BCOD of 8.40ram, and an axial edge lift of about 0.12mm. No mention was