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Fresnel lenses are important compact optical components, which are comprised of multiple faceted concentric rings. These lenses are the most widely utilized diffractive optical element in the industry and has been extensively applied in various optical systems due to their distinct advantages. These include the reduction in the lens thickness, smaller occupied volume and less material required compared to their conventional spherical and aspherical counterparts. In general, the processes to manufacture Fresnel lenses can be categorized into two distinct groups: subtractive fabrication and precision forming. Precision forming processes, like molding and embossing, are usually used in mass production to replicate the optical features and profiles usually employ the use of lens molds generated by subtractive fabrication processes. Thus, the process of molding Fresnel lenses are not substantially different from that of conventional molding processes for other optical components, still relying on the accuracies of the molds utilized. Unfortunately, there is a lack of a comprehensive study to summarize and evaluate the recent advances of UPM techniques to generate these optical Fresnel lens structures. Fresnel lenses and molds differ from each other in terms of lens design, work material and tool/workpiece geometries, and such variations will then drive the development of different machining and characterization methods in terms of tool setting, tool wear, tool path generation as well as lens measurement. This paper summarizes the existing fabrication techniques to generate these lens structures, excluding molding. In addition, a discussion and analysis of the strengths and future areas of research interest of the reviewed techniques are conducted. This review is believed to be helpful and educational for the progress and further development of machining of ultra-precision Fresnel lens structures for advanced optical applications.

Cataracts and age-related macular degeneration (AMD) are the leading causes of blindness worldwide. The main symptoms of AMD are: a gradual decrease in visual acuity to the hundredth, metamorphosis, the appearance of a central scotoma, which reduces the quality of life of the patients and leads to disability. Prosthetic and stationary means of optical rehabilitation, such as magnifiers for the visually impaired, glasses, video systems are cumbersome and poorly functional. An alternative correction option is intraocular vision devices that improve the patient’s quality of life. The review considers various types of intraocular implants, in particular, the intraocular telescope system (intraocular miniature telescope-IMT, IOL-VIP, IOL-AMD), Fresnel lens, Lipschitz lens, Scharioth macular lens (Scharioth macula lens, SML), EyeMax Mono, LENTIS ® MAX IOL LS-313 MF80. The use of high-tech devices for the correction of visual disturbances in AMD has opened a new direction in the rehabilitation of low vision. Further study and implementation of the latest generation of “macular” lenses will improve the quality of life of patients with advanced stages of AMD.

Solar radiation can be considered as one of the most suitable energy source to be used for cooking food. It is therefore important to promote advancement in solar cooking systems, in particular as concerns their efficiency and cooking times. In this work, we designed, realized and tested a novel low-cost solar cooker that uses a high-performance light-concentrating Fresnel lens, which is able to concentrate onto a small focal area a large amount of solar radiation. The radiation is then reflected by a mirror towards a cooking surface, where a pot can be located. The cooker has a geometrical concentration ratio of 40.97. In order to characterize the thermal performance of the cooker, we carried out several outdoor tests with a dedicated test setup, using water and silicone oil as absorbing media. Respect to other solar cookers, results show that the proposed cooker is able to reach high temperatures with good efficiency and reduced heating times: 3 kg of water can reach 90 °C in around 30 min, while 3 kg of silicone oil can be taken from 40 to 170 °C in less than one hour.

Focusing Fresnel lenses are used in many fields of applied optics. These devices are used in optical sensor systems for imaging and optoelectronic integration. The traditional Fresnel lens concentrates the light intensity on the center of the formed image. We present a microprismatic Fresnel lens that transforms a circular incident parallel light beam into a homogeneous light circle with the necessary diameter at a certain distance from the lens. These transforming Fresnel concentrators can be successfully used, for example, in monitoring devices to automatically adjust the output signal from four-quadrant photodetectors. Traditional focusing Fresnel structures are manufactured by photolithographic methods or adjustable direct laser recording with photoresists. These methods enable the formation of stepped optical structures, which have inherent surface defects, resulting in the formation of images that are not high in quality. The proposed specialized Fresnel concentrators can be easily fabricated via the diamond cutting method, which enables the manufacturing of flat working surfaces with exceedingly high optical quality. We also develop a method for simulating the Fresnel transforming lenses with flat conical working facets and calculate the geometric parameters of the circular concentrators. We then apply the simulation results to the diamond cutting method and fabricate the microprismatic light transforming lens samples. These samples are then investigated experimentally with a collimated laser beam. The obtained data agree with the theoretical predictions.

Crossed electrode arrays address some of the challenges associated with 3-D ultrasound imaging because of the significant reduction in the number of elements ( $2{N}$ versus ${N}^{{2}}$ ). However, creating a two-way focused 3-D image in real time is difficult with these arrays because azimuth and elevation dimensions cannot be beamformed at the same time. This work describes a new 3-D imaging technique that uses the flexibility of bias-sensitive substrates to create a high-quality elevation focus on a crossed electrode array. The principle behind this technique is to perform conventional compound imaging with an azimuth set of electrodes while implementing a bias controllable elevation lens with an elevation set of electrodes. On transmit, the biases are chosen to mimic a Fresnel lens. Then, on receive, the Hadamard coding is implemented along the elevation dimension. After decoding, we gain the RF data for each element across the elevation aperture even though there is effectively only one channel in that dimension. A 30-MHz, 128-element crossed electrode relaxor array was fabricated on a 1–3 electrostrictive composite substrate and was used to demonstrate the performance of the imaging technique. The on-axis −6-dB beamwidths were simulated to be 175 and $150~\mu \text{m}$ in the azimuth and elevation directions, respectively, and the focus remained isotropic in the furthest elevation slice. Images were generated of a wire phantom to confirm the performance of the azimuth and elevational radiation patterns with good agreement between simulation and experiment. High-resolution 3-D volumetric images were generated of an ex vivo rat brain. Images of the cerebellum showed that the white and gray matter tracts could clearly be visualized with isometric resolution in both the azimuth and elevation dimensions.

We propose a new thin and flat virtual reality (VR) display design using a Fresnel lenslet array, a Fresnel lens, and a polarization-based optical folding technique. The proposed optical system has a wide field of view (FOV) of 102°x102°, a wide eye-box of 8.8 mm, and an ergonomic eye-relief of 20 mm. Simultaneously, only 3.3 mm of physical distance is required between the display panel and the lens, so that the integrated VR display can have a compact form factor like sunglasses. Moreover, since all lenslet of the lenslet array is designed to operate under on-axis condition with low aberration, the discontinuous pupil swim distortion between the lenslets is hardly observed. In addition, all on-axis lenslets can be designed identically, reducing production cost, and even off-the-shelf Fresnel optics can be used. In this paper, we introduce how we design system parameters and analyze system performance. Finally, we demonstrate two prototypes and experimentally verify that the proposed VR display system has the expected performance while having a glasses-like form factor.

In this paper, a novel small-decentralized desalination device is presented for increasing the temperature difference between brackish water and glass cover, so as to enhance the solar still’s freshwater productivity. This novel solar still device is based on installing a lens in front of the single slope solar still, and two lenses on still’s both sides, and a reflector over the back side of the solar still. The main objective of such novel still is to concentrate sunrays at the still’s bottom basin, through the refraction function of Fresnel lens. Furthermore, this novel still makes the reflector transferring its reflected sunrays to the solar still’s basin. Experiments are conducted under the climate conditions in Hangzhou city, China, for testing the novel still’s operational performance, and internal heat and mass transfer characteristics. Assessment of the novel still’s feasibility is performed based on energy, exergy, exergoeconomic, and enviroeconomic methodologies, as well as energy payback time. Results show that the productivity of novel still is 32% higher than that of conventional still, and novel solar still enhances the average hourly energy efficiency by 97.73%, compared to conventional solar still. While, the corresponding value of hourly exergy efficiency is also enhanced by 43.713%. Due to the higher energy and exergy outputs of novel still throughout its lifetime, the novel solar still proposed in this study mitigates more CO2 compared to the conventional still. Overall, incorporation three lenses and one reflector with the still is found promising in terms of freshwater yield, cost, and energy payback time compared to conventional one. Exergoeconomic and environmental parameters of the novel solar still are found more effective compared to the conventional one.

This paper evaluates the performance of standalone thermal system and cogeneration PVT system under concentrated two stage linear Fresnel lens (FL) based system with convex lens as Secondary Optic Element (SOE). Experiment for standalone thermal system with two stage concentrator investigates the thermal efficiency of the system with copper plates as thermal collector. The experiments to obtain VI characteristics of PV module were done without lens, then with FL and with both FL/CL. The electrical efficiencies were 12.23%, 11.5% and 9.2% respectively which shows fall in efficiency as a result of concentration. Peak powers were 3.42 W, 3.74 W and 4.23 W respectively which shows there is rise in output power. Increase in output power from no lens to single lens was 9.3% and increase in output power from single lens to two stage lenses was 13.1%. The position of Primary Optic Element (POE) was determined by adjusting distance from 10 cm to 35 cm. At 30 cm max power was obtained so POE was kept at 30 cm. In similar manner, SOE was positioned at 15 cm from POE. The net efficiency of standalone thermal system and PVT system with two stage concentrations was 47.61% and 53.7%.

Besides the prohibitive cost, complexity, and baseband scale, the development of millimeter-wave (mmWave) digital-beamforming fifth-generation (5G) frontends is facing a physical-layer challenge of thermal dissipation. This is caused by the massively integrated power amplifiers (PAs) and the extremely compact volume due to millimeter-scale wavelengths. In this work, we theoretically analyze and experimentally demonstrate a reconfigurable planar Fresnel lens, based on which a new-concept mmWave beamforming frontend can be implemented with significantly reduced number of PAs. It overcomes the inherent shortcomings of analog beamforming solutions relying on massive use of power dividers and phase shifters and can replace the convex lens used in the recently proposed hybrid beamforming solution. The implemented Ka-band lens is simple-structured, cost-effective, and easy to control, providing multiple modes for beamspace massive-multiple-input multiple-output (MIMO) communications. Experimental results verified its potential in different mmWave 5G systems such as base stations and point-to-point links.

This paper describes a novel acoustic transducer with dual functionality based on 1-mm-thick lead zirconate titanate (PZT) substrate with a modified air-cavity Fresnel acoustic lens on top. Designed to let ultrasound waves focus over an annular ring region, the lens generates a long depth-of-focus Bessel-like focal beam and multiple trapping zones based on quasi-Airy beams and bottle beams. With 2.32 MHz sinusoidal driving signal at 150 $\text{V}_{\mathrm {pp}}$ , the transducer produces a focal zone with 9.9 mm depth-of-focus and 0.8 MPa peak pressure at a focal length of 31.33 mm. With 2.32 MHz continuous sinusoidal drive at 30–35 $\text{V}_{\mathrm {pp}}$ , the transducer is able to trap multiple polyethylene microspheres (350–1, $000~\mu \text{m}$ in diameter and 1.025–1.130 g/cm3 in density) in water either simultaneously (when suspended by mechanical agitation or released from water surface) or sequentially (when placed one after another with a pipette). The largest particles the transducer could trap are two 1-mm-diameter microspheres stuck together (1.07 mg in weight, lifted by buoyancy and $0.257~\mu \text{N}$ acoustic-field-induced force). When the transducer is moved laterally, some firmly trapped microspheres follow along the transducer’s movement, while being trapped. When trapped, some microspheres can rotate due to the rotation torque generated by the quasi-Airy beams. [2020-0184]

Fresnel lenses allow the concentration of sunlight that can be employed in different thermal unitary operations or endothermic chemical transformations. A system with Fresnel lenses should also take into account vessel or reactor surface thermal losses (reflection, convection and emission), as well as the thermal energy required to keep the vessel or reactor structure warm. In this paper, a numerical and experimental analysis indicated that the solar radiation incident on the lens, the Fresnel lens area and the specimen mass can be represented by a grouping called Heating Factor (31 ≤ Ψ (W/kg) ≤ 3347). The Heating Factor (Ψ) was strongly correlated with the maximum temperature conductive specimens could reach when inserted at the focal point of a Fresnel Lens. Equilibrium Temperatures were predicted by a physical-mathematical model and validated by experimental tests. The Fresnel lens system has been shown to be able of providing Equilibrium Temperatures from 345 to 1600 K for specimens with Heating Times between 3 and 85 min and Initial Thermal Rates from 1.16 to 312.00 K/min. Numerical-experimental analyses also showed that the heating dynamic was strongly influenced by the nature of the materials that constituted the specimens (specific mass and the specific heat).

Enhancement of solar intensity is achieved through concentrator which focuses direct normal irradiance to a smaller area. Such redirection necessitates aligned movement of the whole assembly along the apparent motion of the sun. The motion of a bulky system consumes significant power during the operation, thereby reducing the effective energy collection efficiency. Therefore, a static geometry which does not require tracking the sun is desirable as concentrating optics. Here, we propose such a novel static concentrator based on cylindrical Fresnel lens. Only the absorber is given a single axis tracking motion. A systematic optimization is performed to select the geometrical parameters which maximize the solar intensity and minimize the intensity-non-uniformity. For a Silicone glass cylinder of 20 cm diameter, we find an absorber of width 5 cm, placed at a distance of 11 cm from the axis of the concentrator provides the maximum intensity and the minimum intensity-non-uniformity when the vertex angle of the Frensel lens is 37°. The study demonstrates that the procedure to perform such geometry optimization is straightforwardly extendable. We demonstrate that the annual average intensity on the absorber can be enhanced by over ∼50% with lower operational cost and a meagre increase in the initial cost.

In this communication, we experimentally demonstrate a frequency- and beam-reconfigurable lens antenna based on an active second-order bandpass frequency-selective surface (FSS). The FSS lens is composed of three nonresonant metallic layers separated by two thin dielectric substrates. By integrating microwave varactors in FSS unit cells, the center frequency of this bandpass FSS can be tuned from 4.0 to 5.8 GHz by a direct-current (dc) bias voltage. Based on this wideband tunability, the phase-correction technique is used to implement a microwave Fresnel lens. The experimental results show that the proposed 1-D lens antenna can achieve frequency-reconfigurable beam steering within a 1 GHz bandwidth. With advantages of low cost and concise structure, the proposed reconfigurable lens antenna can be potentially used in a wide range of applications.

Injection molding is an ideal technique for the low-cost mass production of plastic optical lenses. However, the optical quality of the lens is significantly dependent on the processing parameters employed in the molding process. In particular, the parameters should be set in such a way as to minimize both the shrinkage displacement-induced warpage (in order to reduce optical aberrations) and the residual stress (in order to reduce the birefringence). However, in practice, the two performance targets are mutually exclusive. That is, a smaller warpage results in a greater residual stress, and vice versa. Thus, in the present study, Taguchi experiments are first performed to determine the processing parameters which individually minimize the warpage and retardation of a symmetric plastic double-convex Fresnel lens, respectively. A grey relational analysis technique is then applied to the Taguchi results to establish the processing parameters which achieve the optimal tradeoff between the two performance objectives. The validity of the proposed method is demonstrated by means of mold-flow analysis simulations. The results show that in simultaneously optimizing both the warpage and the retardation, the injection molding control factors are ranked in order of decreasing influence as follows: packing pressure, packing time, melt temperature, filling time, cooling time and mold temperature. Given the optimal process parameter settings, the warpage and retardation are reduced by 16.42% and 74.74%, respectively, compared to the original design. In other words, the proposed grey-based Taguchi method provides a viable technique for optimizing both performance targets for the considered double-convex Fresnel lens.

A theory of correcting residual change in focal length with wavelength is presented for high-harmonic diffractive lenses. The theory is based on a multiple-order diffractive (MOD) lens in combination with a stepped plate called an Arizona total energy color corrector (AZTECC) lens. Results indicate that best performance in terms of on-axis focused irradiance versus wavelength is found when low-dispersion glass is used for the AZTECC lens. A single-order diffractive Fresnel lens (DFL) in combination with the AZTECC lens makes the system achromatic over a wide bandwidth.

International audience; An important challenge in infrared imaging today consists in addressing the SWaP problem (Size, Weight and Power), for example by simplifying as much as possible the optical system before the sensor. The work presented in this paper takes advantage of recent techniques in femtosecond laser direct writing to imprint optical systems. This work aims at merging a lens array with a filter array by writing gradient index lenses with a femtosecond laser inside a dedicated glass substrate. A classical gradient index lens requires a huge refractive index variation, which cannot be reached today with femtosecond laser processing (Δnmax ~ 0,05). So, we decided to turn towards writing a gradient index Fresnel lens. A first-order Fresnel lens was designed with a Δnmax < 5.10−2 discretised into 8 index levels to guarantee a diffraction efficiency of 85% on the overall spectral bandwidth of the filters. We studied a chalcogenide glass because of his good properties in mid-IR optics. We compared the different laser responses of the material: threshold of permanent changes, quantitative phase and index variation. Finally, we showed that reaching a phase variation of π radians with femtosecond laser writing is possible even for a huge scanning speed (0,01 mm/s up to 25 mm/s). By overlapping the written lines, we were able to implement a maximum phase variation of 8 radians (with only one written layer), demonstrating the possibility to write quickly a GRIN Fresnel lens with a diameter of some millimeters.; Un défi important dans l'imagerie infrarouge consiste aujourd'hui à résoudre le problème SWaP (Size, Weight and Power), par exemple en simplifiant autant que possible le système optique avant le capteur. Le travail présenté dans cet article tire parti des techniques récentes de texturation par laser femtoseconde pour créer des systèmes optiques. Ce travail vise à fusionner une matrice de lentilles avec une matrice de filtres en écrivant des lentilles à gradient d'indice avec un laser femtoseconde dans un substrat dédié. Une lentille classique à gradient d'indice nécessite une variation importante de l'indice de réfraction, qui ne peut être atteinte aujourd'hui avec une fabrication par laser femtoseconde (Δn ~ 0,05). Nous avons donc décidé de nous tourner vers l'écriture d'une lentille de Fresnel à gradient d'indice. Une lentille de Fresnel du premier ordre a été conçue avec un Δn < 5e-2 discrétisé en 8 niveaux d'indice afin de garantir une efficacité de diffraction de 85% sur la bande passante spectrale globale des filtres. Nous avons étudié un verre de chalcogénure en raison de ses bonnes propriétés optiques dans le moyen infrarouge. Nous avons comparé les différentes réponses laser du matériau : seuil de changements permanents, variation quantitative de phase et d'indice. Enfin, nous avons montré qu'atteindre une variation de phase de π radians avec une texturation laser femtoseconde est possible même pour une vitesse d'écriture très élevée (0,01 mm/s à 25 mm/s). En superposant légèrement les lignes texturées, nous avons pu mettre en œuvre une variation de phase maximale de 8 radians (avec une seule couche), démontrant la possibilité d'écrire rapidement une lentille de Fresnel GRIN d'un diamètre de quelques millimètres.

This study aims to resolve the trade-off between the constraints and capabilities of ultra-precision machining to achieve ophthalmic Fresnel lenses. A general Fresnel lens pattern has a narrow variable pitch and curved grooves. However, we obviate the limitations of the tool nose radius constraint and the long tool path via ultra-precision machining of the modified Fresnel lens, ensuring a constant pitch of 0.1 mm and varying the height of straight grooves from 0 to 11 µm. Photorealistic raytracing visualization and MTF simulation verified the compatibility of the lens pattern with human perception sensitivity. Copper-coated mold was fabricated using a diamond tool with a tool nose radius of 5 µm. The replicated flexible Fresnel lens demonstrated a relative MTF imaging performance of 89.1% and was attached to the goggles for the qualitative assessment. The proposed Fresnel lens design and fabrication approach can be extended to applications in the visual and infrared ranges as well.

Freeform optics are used to create complex application-adapted illuminance distributions due to their high number of adjustable degrees of freedom. As with conventional optics, this can result for some applications in large optics that exceed the available installation space or lead to high production costs. While the use of Fresnel lenses is common in such cases for conventional optics, the Fresnelization step in the design process of freeform optics is more complex due to the lack of rotational symmetry and only done for specific cases. Therefore, this paper presents a method to examine different segmentation strategies on freeform lenses and to optimize Fresnelization parameters. In this work, the method will be demonstrated using a head-up display (HUD) as example, in which the combination of a Fresnel lens and a display creates a moire pattern in the illuminance distribution. In order to accelerate the simulation of complex Fresnel freeform optics considerably, a special ray tracing algorithm is developed, which takes advantage of the segmentation characteristics. The simulation approach of the illuminance distribution and the optimization of the Fresnelization are shown and discussed on a lens with about 300 segments visibly reducing the moire pattern.

A virtual prototype focussed ultrasound surgery (FUS) transducer has been developed with finite element analysis (FEA) (OnScale, Redwood City, CA, USA) comprising a single piezocermic element and an acoustic Fresnel lens. The piezoceramic is supported by microbaloon filled epoxy to approximate an air backing. The transducer housing and Fresnel lens materials are photopolymer resins of the type used in mask stereolithography (mSLA) printers. The design is optimised in FEA for the materials used in the Fresnel lens and the active piezoceramic layer. Six piezoceramic materials produced by Meggitt A/S (Kvistgaard, Denmark) were characterised in FEA and the acoustic properties of the photopolymer resins were measured using a standard pulse-echo approach to find their sound speed and frequency-dependent attenuation. The piezoceramic materials characterised spanned four major types: soft (PZ29); hard (PZT4); a specialised composition for high intensity focused ultrasound (HIFU) (PZ54); and low acoustic impedance, porous (PZ36HD). Acoustic impedance matching between the active material and the lens allowed the porous piezoceramic with lower piezoelectric and coupling coefficients to reach a higher intensity, spatial peak temporal average, (I SPTA ) at the focus (3.6 kWcm−2) than the hard PZT (2.46 kWcm−2). The focal intensity improved when HIFU and soft PZT were used, producing 5.69 kWcm−2 and 6.35 kWcm−2respectively.

The most common neurostimulation method is the stimulation of the focal point by using a focused ultrasound transducer. In the field of particle manipulation using ultrasound, research using acoustic vortices is ongoing and presents promising characteristics. In neurostimulation using ultrasound, the acoustic radiation force is a leading candidate for a physical mechanism. In this study, the acoustic radiation forces generated by a general-focused transducer and a vortex transducer were compared. For the experiment, a 70 mm diameter transducer with a center frequency of 1 MHz was fabricated using a piezoceramic plate. The ultrasound transducer frame was made of aluminum, and air backing was used to maximize the output pressure. A large-scale Fresnel focused lens and focused vortex lens were fabricated using polydimethylsiloxane (PDMS). A mold of an 8-step Fresnel lens with a diameter of 70 mm was developed using 3-D printing. We compared the pressure field and radiation force according to the two manufactured lenses to determine whether there was any difference in neurostimulation.

High-efficiency concentrator photovoltaic modules have been developed and fabricated. The modules include a lens panel based on 32 Fresnel lenses (12 × 12 cm each), 32 multi-junction solar cells with secondary concentrators in the form of phocons, and heat-removing electrically insulating boards based on an aluminum oxide ceramic placed on the backside aluminum base. Efficiency measurements of a 0.46-m2 module under a pulsed sunlight simulator (AM1.5D, 1000 W/m2) yielded a value of 32.3%. An efficiency of 33.9% was obtained for a subunit with an area of 144 cm2.

Fresnel-based concentrated photovoltaic (CPV) solar power systems have been proven effective to significantly enhance the photoelectric conversion efficiency, but a standard-size solar plant will require an extremely large amount of polymer radial Fresnel lenses. Roll-to-roll (R2R) manufacturing is a high-throughput technology to mass produce high-quality functional optical polymer film. In this paper, we have firstly studied a complete manufacturing cycle for R2R embossing of radial Fresnel lens polymer film for CPV systems, in terms of polymer lens design, roller mold machining, R2R embossing and optical performance test. Instead of wrapping an electroplated metal sheet onto the roller in conventional R2R process, the lens pattern array is directly machined using a 5-axis ultra-precision machining system to guarantee its surface quality and accuracy. Optical performance evaluation for the manufactured polymer film using a reference solar cell is conducted, and results have shown that radial Fresnel lens on the polymer film can achieve a sunlight concentration ratio 3.9 × times that of linear lenses with a much smaller receiving area. This study has explored the feasibility for R2R embossing of optical polymer film, an industry-applicable and cost-effective technology for mass production of high-quality Fresnel lenses to be used in high-efficiency CPV systems.

In order to meet the requirements of the high gain and wide field of view (FOV) for indoor visible light communication (VLC) system, a new optical receiving system is proposed, which integrates a Fresnel lens with a hemispherical lens. The effects of the two lenses’ spacing and the radius of the hemispherical lens on the optical gain at different FOV are investigated. As the FOV increases, the designed antenna displays enhanced reception performance compared with the traditional receiving optical antenna. The optical gain of the designed antenna is 6.88 in the condition of FOV of 40°. To further verify the rationality of the designed antenna, a model of VLC system is established based on the designed antenna in a room with a size of 5 m×5 m×3 m. The results show that the received average power using the designed antenna increases by 22.81 dBm, and the average signal to noise ratio (SNR) is 2.3 times of that without any optical antenna. The designed antenna is promising for the application in indoor VLC systems.

The technology of small point-focusing concentrator of solar energy has been developing rapidly in recent years owing to its compact structure and high collecting efficiency. This report presents important developments of small point-focusing concentrator in the past decade. This kind of solar concentrator refers to the parabolic dish concentrator, the point-focusing Fresnel lens, and the Scheffler reflector. Technological advances of these concentrators and the related performances have been presented. There are three main mirror fabrication technologies for dish concentrator, which are high polishing metal, silver-glass mirror and vacuum-membrane. Polymethyl methacrylate is widely used as material in Fresnel lens. Many scholars have proposed new lens shape to improve the uniformity of focusing. The Scheffler reflector has a characteristic of fixed focus, but its design parameters are not perfect so current research focuses on the theoretical calculation of the mirror. In addition, typical applications of the small point-focusing concentrator in photovoltaic system, solar thermal system, solar chemical system, and day-lighting system are summarized. Upon listing the important publications in open literature, a category of main applications of such kind of solar collector is provided based on the working characteristics of the system.

A fraxicon is a stepped phase plate lens designed to be a discrete approximation of the axicon, a refractive cone-shaped lens. Both lenses generate minimally diffractive Bessel beams with long depths of focus. Here the characteristics of broadband pulses modified by these lenses to compare and contrast the dynamics of the propagating wave packets were examined. Pulses from a spherically focused Fresnel lens are also examined to provide the context of a conventional design. The wave packets generated through the fraxicon exhibit many of the same characteristics of those from the axicon such as lateral compactness and axial integrity, although the fraxicon packets do exhibit noticeable dispersion in comparison. Both the fraxicon and axicon wave packets have a much tighter lateral extent than those of the Fresnel throughout the propagation region. The most significant difference between the fraxicon and axicon is with the group speeds of the packets with the fraxicon group subsonic and the axicon supersonic across a 50 mm path. Supplemental movies are provided for direct visualization of the propagation (for movies of the waveforms and energy profiles of the wave packet propagation that was experimentally obtained). To assess the conformity of the low profile lenses to their design parameters, frequency domain comparisons of measurements with simulations are also presented and are in good agreement.

The driving motive of this work is to enhance the tolerability of a flat Fresnel-lens concentrator to tracking errors, without the use of secondary optics or sophisticated, and normally costly, meticulous tracking equipment. This is achieved by optimizing the prismatic geometry of the Fresnel lens through a statistical approach that incorporates laws of light refraction and trigonometry. The proposed design produces high focal heat flux that is more suitable for thermal applications. A comparative simulation analysis was conducted for two case studies from literature, each with a different design method for the Fresnel lens. On basis of equivalent geometric concentration ratio and f-number, the flat-spot lenses, designed by this study, returned higher values of the concentration acceptance product ( $$CAP$$ ). In case #1 of a 212× cylindrical lens with an f-number of unity, an equivalent flat lens by this work almost doubled the $$CAP$$ from 0.165 to 0.34. For the design case #2 of a 559× aspheric Fresnel lens made by simple geometrical optics, a 60.7% enhanced $$CAP$$ was achieved by this work’s lens, from 0.206 to 0.331, at an f-number of 0.83.

Ultrathin Fresnel lens may revolutionize current optical imaging system, leading to thinner and lighter optoelectronic devices with a myriad of technical applications. To date, evaporated bulk metal films and top-down grown graphene represent viable material choices toward the design of ultrathin Fresnel lenses. Despite recent advances, it is still lack of a scalable fabrication strategy to achieve ultrathin lens with high focusing efficiency. Here, we report a new self-assembled metamaterials-based strategy to design ultrathin Fresnel lens using our recently reported plasmene nanosheets. With comparable thickness, our plasmene-based Fresnel lens offers a much better focusing efficiency than that based on continuous metallic films. This may be attributed to the dual Huygens’ effects from both slits and plasmene-constituent nanoparticle building blocks. Importantly, internal structural features of plasmene can be precisely tuned simply by adjusting sizes and shapes of its constituent building blocks, allowing for maximizing the focusing efficiency at a desired operating wavelength – a capability impossible to achieve with continuous metal films or graphene. Our plasmene-based strategy opens a new route to design tailor-made flat lens with finely tunable internal and overall structural properties, which offers new dimensionalities in controlling light-matter interactions for a myriad of technological applications.

Large three-dimensional (3D) scene reconstruction is a challenge for current colour holographic displays. In this study, we develop a compact display system to reconstruct a large 3D scene using a 21-inch liquid crystal display (LCD) panel that serves as a spatial light modulator (SLM). We utilise a Fresnel lens instead of a conventional lens to reduce the complexity of the system. A spatial multiplexing colour filter attached to the SLM is used to simplify the structure of the colour display. Additionally, an independent block holographic algorithm is developed to record accurate depth information. Numerical simulations and optical experiments are performed to verify the proposed system. The optically reconstructed 3D colour scene is 480 mm × 300 mm × 500 mm in size. Therefore, the proposed display system represents development toward a commercial product for its low device requirements.

In this paper, an autostereoscopic display system based on a time-multiplexed directional backlight using a large aperture Fresnel lens is proposed. High-resolution stereoscopy for multiple viewers positioned at different distances from the screen is achieved in the proposed system by layering polymer dispersed liquid crystal screens behind the Fresnel lens. The screens with segmented electrodes are electrically controlled to change the position of light diffusion, while the time-multiplexed backlight is projected by a digital mirror device projector at a high refresh rate. The light is diffused at the conjugate focal points of the observers’ eyes to deliver directional light to each eye. The right-eye image and the left-eye image are alternated on the LCD panel in front of the lens to synchronize with the backlight.

Additive manufacturing (AM) and rapid prototyping process (RPP) have revolutionized the production of 3D objects in the last few decades. RPP has considerably increased the rate of production and the possibility of manufacturing prototypes in the fields of electrical, optical, and mechanical engineering. The manufacturing of optical prototypes including spherical, aspheric, and special kinds of lenses and lens arrays has reformed the fabrication of optical components. In this paper, specifically designed lens array prototypes for application in visible light communication (VLC) are introduced. These lens array prototypes are manufactured using the stereolithography apparatus (SLA) process. These lens arrays are designed to achieve optimal transmission of the light beam for VLC systems. One of the prototypes from the lens arrays contains primarily four spherical lenses and one thicker convex lens and the other contains one fresnel lens as a substitute for thicker convex lens. These lens arrays are further post-processed to achieve the required transparency. These lens array prototypes are tested using laser and LEDs. The ON-OFF keying modulated light beam was transmitted through the lens array at the sender side and focused on the photo-receiver using another lens array at the receiver side which is 200 cm apart. After evaluating these lens prototypes, it can be concluded that with appropriate post-processing and high-resolution stereolithography based manufacturing, a low data rate VLC link can be formed.

An asymmetric optical cryptosystem to encrypt images using devil’s vortex Fresnel lens (DVFLs) phase masks and lower upper decomposition with partial pivoting (LUDPP) is proposed in gyrator transform domain. The proposed cryptosystem utilizes DVFLs which are the complex phase masks designed using the combination of a phases of devil’s lens (DL), vortex lens(VL), and Fresnel lens (FL). LUDPP is an operation used to decompose the matrix and is utilized to supersede the phase-truncation (PT) task in the traditional phase-truncated Fourier transform (PTFT). Hence, the proposed method is immune to the attacks to which the PTFT-based cryptosystems are vulnerable. The cryptosystem is asymmetric as both the encryption and decryption processes are different along with different keys. The private keys generated during the encryption process are utilised in the decryption process to retrieve the original image. The encryption and decryption process can be realised with both the digital and the modified optical architecture. In order to show the strength and robustness of the proposed encryption, a conspire numerical simulation was performed.

A slotted dielectric Fresnel lens antenna designed to work in the 60 GHz band is designed. The antenna consists of a feed structure and a lens structure. Using the HFSS microwave simulation software, a half-wave dipole feed structure was first designed, and a slotted dielectric Fresnel lens antenna was designed based on the half-wave dipole feed structure. Then, through simulation and comparison of the effect of different full-wave periods w on the focusing performance of the slotted dielectric Fresnel lens antenna when the sub-region P = 4, it is concluded that the full-wave period of 3 is the optimal number of full-wave periods. After the half-wave dipole antenna is focused by the slotted dielectric Fresnel lens antenna with sub-region P = 4 and full-wave period w = 3, the antenna gain is increased by 18.27 dB and the beam angle is reduced by 73°.

In this paper, we propose a technique using the conservation of optical path length and edge ray theorem to design a Fresnel lens, which can achieve high concentration ratio, high uniform irradiance, and small f-number. The structure of the Fresnel lens consists of three parts: Inner part, middle part, and outer part. The design process is carried out by solving the equations of the conservation of optical path length in Matlab™ program. In addition, a wide range of wavelengths is applied to do rays tracing so that the system becomes more suitable in real conditions. In this technique, the Fresnel lens is constructed by many grooves that are built by the ideal Cartesian oval surface. Thus, the optical efficiency of the designed lens is improved. The simulation results by LightTools™ software show that the Fresnel lens has good optical properties such as a high concentration ratio of 900x, f-number = 0.46, high uniform irradiance distribution, and optical efficiency larger than 85%.

A scheme of a compact holographic wavefront sensor based on combination of computer-generated hologram and computer-generated Fresnel lens is presented. This scheme allows optical aberration measurement with high precision. The presented optical scheme is tested and compared to a scheme with physical Fourier lens.

Electrical lighting design is usually based on the illumination design. Its main task is to ensure that the electricity and optical system can be normal, safe, reliable, and economically viable. In this paper, we propose a design and optimization method for outdoor illumination systems to generate relatively powerful light beams for far distances. The illumination systems are based on highly integrated LED modules instead of high intensity discharge lamps. The size of the LED light-emitting surface is 2.5 m m × 2.1 m m , and the secondary optical elements are composed of a basic plano-convex lens and a Fresnel lens. The results of simulation demonstrate that the emission angle of the system is 1.1°, and the central illumination at 2500 m away is more than 1 lx. The total system is simple but practical, and several groups can be combined into a larger system. Two proof-of-concept prototypes producing acceptable illuminance are developed, and one is composed of four groups whose light is visible from 5000 m away. Both are fully waterproof and in a high degree of protection. The systems can provide up to 12 h of continuous lighting, and the operating temperature rise is less than 25°C. The results indicate that our design can be applicable for practical wild working sites.

Real-time quantitative PCR technology has been an active filed since it has excellent performance of the ability of quantitative analysis for initial DNA template evaluation and detection on fluorescence signal. This paper basically pay attention on the features of system and optimize the original parts of the device. Using OLED as light source and nonlinear optics device in the light path to optimize the effect of the device. According to simulation results, the uniformity of the excitation in this device has a marked improvement. Furthermore, with the addition of the filed lens, the collection effect of the fluorescence would be better.

Due to the light attenuation in water, underwater image qualities are affected and various in different imaging systems. In this paper, a modulation transform function (MTF)- inspired image quality assessment method is proposed and in which a point-by-point slanted-edge algorithm is introduced to evaluate the underwater systems. Four systems with different light sources are installed to verify the method at different distances in the same water quality. The light sources of these systems are a customized 500W lamp, biconvex lens cluster (BILC) light, Fresnel lens cluster (FNLC) light and digital light processing (DLP) compensated floodlighting, respectively. Then, experiments demonstrate the superiority of DLP compensated floodlighting than the other systems and the obtained MTF curves show that when the spatial frequency is 0.5 cy/pixel, the MTF value of the DLP imaging system at the imaging distance of 1m and 3m are 0.05 and 0.1, respectively. The experiments show that the proposed method can be used to evaluate imaging quality effectively.

Using a focused ultrasound transducer is one of the most preferred methods for neurostimulation. Due to its high spatial resolution, high penetration depth, ultrasonic property, and its ability to be combined with other methods, a focused ultrasound transducer is suitable for non-invasive brain neurostimulation and is widely used. Generally, only one transducer is used or all transducers face one direction for focusing. Unlike previous cases, neurostimulation using a pattern interface radiation force (PIRF) uses more than two focused transducers and makes standing wave patterns inside the brain for neurostimulation. This paper presents the fabrication and application of a large-scale focused transducer using a Fresnel lens for PIRF application. The focused transducer is made with polydimethylsiloxane (PDMS) and a hybrid-type piezoelectric (PZT) ceramic plate similar to PZT-4 with a size of 100 mm × 80 mm × 2.2 mm. The lens was designed for a 1-MHz frequency, which is the center frequency of the PZT plate. Using these two transducers, a standing wave pattern was created inside the skull, and the radiation force was calculated using the measured pressure field.

With the continued development of multi-order diffractive engineered (MODE) lenses that consist of both multi-order diffractive surfaces and a diffractive Fresnel lens surface, it is becoming more realistic that these components may be used as an ultralight large aperture primary for space telescopes. As conceptual designs for these large primaries push the size limits of optics manufactured by compression molding, it becomes necessary to make a segmented MODE lens primary rather than a monolithic one. We use the Kinematically-Engaged Yoke System (KEYS) to align the segments of a 0.24-m, PMMA, monochromatic, MODE-like lens (having no diffractive Fresnel lens features). The KEYS alignment system consists of modified ultra-fine alignment screws with ball bearings on the end that kinematically engage with the step-like features of the MODE lens surface (similar to a Fresnel lens) to constrain the segments in 5 degrees of freedom, leaving rotation about the optical axis unconstrained. The alignment of the segments is verified using multiple methods including a scanning white light interferometer and deflectometry. Such an alignment system has the capability of fixing the segments together in order to bond them with adhesive while aligned. These tests offer a proof of concept for a system that can be used for an eventual 0.24- m, compression molded, glass, segmented MODE lens.

Most work in the field of freeform lens design has been focused on finding design algorithms for continuous freeform lens surfaces which transform an arbitrary ingoing light distribution into an arbitrary outgoing distribution. The shape of the resulting continuous lens surfaces depends fully on the source and target light distribution for which the lenses are tailored. In some cases this results in large, voluminous optical components which depending on the application are not practical. Fresnel lenses can have a much smaller volume, but are not straightforward to design in the case of freeform lenses. This paper demonstrates a new method to design freeform Fresnel lenses based on concentric freeform segments. Such lenses have a much lower number of discontinuities compared to already existing Fresnel-type freeform lenses which are based on an array of facets. Less discontinuities means less stray light due to the unavoidable rounding errors with current manufacturing processes. The new design method is first explained, and then illustrated for a freeform Fresnel lens with a rectangular target distribution in the far-field ispartof: Optics Express vol:28 issue:17 pages:24489-24500 ispartof: location:United States status: Published online

The paper proposes using a two-zone different level Fresnel lens to increase the depth of field. On the one hand, such a diffractive optical element can reduce the weight of the device compared to, for example, cubic phase and binary axicon apodization. On the other hand, such an element has a simpler structure compared to a harmonic lens or free-form DOE. A neural network is used to restore the image. Optimization of the surface relief of the proposed two-zone lens is performed.

Superior performances, such as high processing speed and resolution, make galvano-mirror-based fabricating strategy widely applied, particularly for micro/nano-scale femtosecond laser direct writing (FsLDW). However, the optically limited processing area restricts its applications. Here, we report a simple, low-cost, and universal pre-compensation method that corrected the off-axis optical aberrations to considerably expand the processing area of galvano-mirror-based nano-FsLDW with 3D nano-resolution maintained. A high-quality continuous-surface Fresnel lens was one-step fabricated with a 550- $\mu \text{m}$ diameter, which surpassed the effective range (~150- $\mu \text{m}$ ) of the high-numerical aperture objective lens used for high resolution. It provides a significant approach for novel high-speed/efficiency micro/nano-FsLDW of diverse micro/nano-elements/systems.

Although within the group of countries with the highest solar irradiation index in the world, Brazil still underuses its natural power. Brazil’s hydropower energy today makes up 68,5% of the total energy produced, in contrast however, photovoltaic energy production is still only 0.01%. As an effort to open up new frontiers for solar energy uses, the main objective of this project was to use solar energy in form of light to reduce the power consumption required for continuously lighting any kind of environment as well as to propose a new technology for illuminating a conventional window-type photobioreactor (PBR) in the cultivation of microalgae for biofuel production in order to reduce their associated costs. The system is composed by a solar tracker, an electromechanical control, a Fresnel lens and a plastic optical fiber (POF) bundle, in which tip the lens concentrates the solar radiation. Therefore, at the other end of the bundle, the POFs can be distributed homogeneously in any local where one wants to illuminate. The solar tracker is able to track the Sun from sunrise to sunset using an algorithm whose function is to calculate the Sun position according to the local time and latitude using an equatorial mount structure. In addition, some sensors are employed for monitoring relevant parameters, for instance, the light intensity inside the POF bundle, the right ascension and declination angles of the tracker and the solar radiation. These parameters can be downloaded in real time through a specially designed mobile application. As application of the solar tracker, two projects were developed and described in this paper: two kinds of solar luminaires for illumination of internal ambiences and a closed photobioreactor by POF illumination, with nontransparent material, free of outside contamination with low cost and the study of the produced biomass through the lipid content. Both applications were compared in performance with their conventional counterparts and, as a conclusion, it is shown that in both cases they can substitute their conventional counterparts with advantages.

We report here significant progress in solar-pumped laser collection efficiency with a grooved bonding Nd:YAG/YAG crystal rod. A Fresnel lens was used as the primary solar radiation concentrator. A gold-plated conical pump cavity with a water filled quartz tube lens was used to concentrate the solar radiation from the focal zone of the primary concentrator into a 6-mm-diameter, 95-mm-length bonding Nd:YAG/YAG crystal rod. To the best of our knowledge, it is the first time of a bonding Nd:YAG/YAG crystal pumped by Fresnel lens solar energy collection and concentration system. For 1.03 m2 effective solar radiation collection area, 32.1 W/m2 collection efficiency was obtained, corresponding to a total slope efficiency of 5.4% and an optical-to-optical efficiency of 3.3%. The performance of the grooved bonding crystal rod was compared with the grooved non-bonding crystal rod. The maximum output power from the grooved bonding crystal rod was 22.6% higher than the value from a grooved non-bonding rod. The M2 beam quality factor was also improved from 126 to 61.

We have developed a new, fast, and simple 3-D imaging approach referred to as Simultaneous Azimuth and Fresnel Elevation (SAFE) compounding using a bias-sensitive crossed-electrode array. The principle behind this technique is to perform conventional plane-wave compounding with a back set of electrodes, while implementing a reconfigurable Fresnel elevation lens with an orthogonal set of front electrodes. While a Fresnel lens would usually result in unacceptable secondary lobe levels, these lobes can be suppressed by compounding different Fresnel patterns. The azimuthal and elevational planes can be simultaneously compounded to increase the beam quality with no loss in frame rate. A 10-MHz, $64 \times 64$ element crossed-electrode relaxor array was fabricated on an electrostrictive one-to-three composite substrate to demonstrate the SAFE compounding approach. The electrostrictive composite array has a measured electromechanical coupling coefficient ( $k_{t}$ ) of 0.62 with a bias voltage of 90 V and a measured two-way pulse bandwidth of 60%. The electrical impedance magnitude of array elements on resonance was measured to be $90~\Omega$ with a phase angle of −35°. Radiation patterns were simulated showing a −6-dB beamwidth of $330~\mu \text{m}$ with secondary lobe levels suppressed more than −60 dB in the azimuth dimension, and a −6-dB beamwidth of $450~\mu \text{m}$ with secondary lobe levels suppressed to −50 dB in the elevation dimension after 64 compounds. Experimental radiation patterns were collected and found to be in good agreement with simulations. Experimental 3-D images of wire phantoms were collected using a Verasonics experimental ultrasound system.

In this paper, the design of a curved Fresnel lens applying to the concentrator photovoltaic system is proposed by using the edge ray theorem, the Snell’s law, and the conservation of optical path length. The new structure of the curved Fresnel lens can improve significantly the uniformity of sunlight distribution over the solar cell while the concentration ratio can reach a high value of 900 times. The good uniform distribution can be obtained by using the novel idea. The novel idea is based on the uniform sunlight distribution of every groove of the lens so that the whole lens also distributes uniformly the sunlight beam over the receiver. The structure of the lens is built by two surfaces: input surface (or upper surface) as a part of spherical surface and output surface (or lower surface) that consists all grooves of the lens. Matlab program is used to design the input and the output surfaces of the lens. The input surface and the output surface are independent to each other in construction in Matlab. LighttoolsTM software is used to optimize the structure of the novel lens. Furthermore, LighttoolsTM is also used to perform a simulation to examine the efficiency of the lens in concentrator photovoltaic (CPV) system by using the light source with a wide spectrum of 380 – 1600 nm. The results show that the lens has an acceptance angle of 0.80 and good optical efficiency (>85%).

In roll-to-roll (R2R) manufacturing of high-quality optical Fresnel lens films, a high-precision roller mold with fine surface finish is essential to precisely transfer the functional microstructures from the periphery roller surface onto the flexible substrate. Unfortunately, direct diamond turning of deep circular grooves on the periphery surface of a roller mold was thought to be infeasible. Hence, a novel 4-axis interactive tool-workpiece motion, rotating-tool diamond turning (RDT), was proposed as a solution to overcome this challenge. In this paper, R2R embossing of optical film patterned with both linear and radial Fresnel lens array using directly machined roller mold is firstly conducted. Multi-axis dynamics during the RDT process is thoroughly studied and essential factors are sourced and analysed, followed by a comprehensive study of these parameters in terms of cutting performance in the RDT setup. Then, a combination of optimized machining parameters is applied to directly machine both radial and linear Fresnel lens arrays on the same roller. Material shrinkage of resin during R2R process is considered in design of the lens feature on the mold, and tool path is generated considering the roller dimensions, lens specifications and the shrinkage compensation. The machined roller mold is then installed on an in-house developed R2R UV embossing system to conduct continuous manufacturing of optical Fresnel lens film at a large throughput. To evaluate the machining performance of RDT and replication performance of R2R embossing, lens profile and surface quality of both the machined roller mold and the embossed film have been studied with different orientations. Measurement results have shown that the profile accuracy and surface finish of machined linear Fresnel lenses have better performances than the radial lenses. Both linear and radial Fresnel lens features can be precisely replicated from the roller mold onto the film without significant differences at different orientations. Proper compensation for the shrinkage of resin in designing the machining pattern on roller has been proved to be necessary and important to achieve desired film quality for this R2R embossing process. This study on R2R embossing of radial Fresnel lens film has proven that RDT is a qualified and reliable machining process to enable high-throughput continuous manufacturing of high-quality Fresnel lens film.

Based on a unified approach in the ray approximation, the focusing properties of Fresnel lenses and kinoform lenses are considered and compared. Particular attention is paid to the energy efficiency, chromatic focal shift and resolving power of these elements. It is shown that the Fresnel lens with same-depth segments is an analogue of the harmonic kinoform lens operating in high diffraction orders. A mechanism of the formation of the diffraction pattern in the focal plane of a Fresnel lens with equidistant annular segments is analyzed. It is shown to differ from the corresponding diffraction pattern formed by a conventional refractive lens by a smaller amount of energy coming to the main maximum and a significant proportion of energy transferred to the side maxima. The target audience of this article is students and graduate students, as well as specialists in the fields of science and technology where optical methods and instruments play an ever increasing role.

High fill factor for Fresnel lens arrays has been achieved with the aid of polygonal lenses. This has been done for both circular trimmed lenses and full polygonal lenses, both of which present some optical drawbacks. The composite polygonal Fresnel lens (CPFL) avoids these issues with its unique design – a radial symmetric Fresnel center filling into a polygon, avoiding any intersecting facets within the lens by introducing fillets. To manufacture the CPFL, diamond shaping is applied to not only meet the strict standards required for optical fabrication but also maneuver around the curvilinear features that cannot be fabricated using conventional turning techniques. As such, direct diamond shaping (DDS) was employed to generate an array of CPFLs on a PMMA substrate. Optical simulation was used to validate the performance of the CPFL before production of the lens array, followed by testing of the fabricated lenses, showing less overall noise with better focus compared to conventional polygonal lenses.

Fiber-optic solar hybrid lighting for mobile application such as military shelters in remote areas is appealing since high initial costs of such systems appear to be justified. This paper addresses the aspect of two-stage optics for a fiber-optic solar lighting system for the mobile application. More specifically, the focus of this paper is on the design and development of a second stage or secondary concentrator. Two-stage optics offers a distinct advantage of higher sun angle tolerance and hence a low-accuracy tracker can be used for the mobile application. The objective of this study was to design and develop a secondary concentrator that yielded a minimized peak illuminance on the fiber-optic inlet and achieved uniformity, to avoid localized heat damage to the fiber inlet. In addition, the overall goal was to increase the lumen output from the two-stage optics. Specifications for the design of the two-stage concentrator were: (1) the primary stage concentrator was a 10-in. diameter Fresnel lens; (2) solar tolerance angle or the half-angle of acceptance was ±1.75°; (3) the fiber half-acceptance angle was ±40°; and (4) the fiber optic cable diameter was 0.5-in. Raytracing was used to determine the optimum geometry for the secondary lens. Among various geometries simulated included a conical secondary, a Compound Parabolic Concentrator (CPC), and a combination of conical and Compound Elliptical Concentrator (CEC). The analysis showed that a combination design comprising conical/CEC geometry was better than the conical and CPC geometries in terms of greatest overall light output and most reduced peak illuminance on the fiber optic cable. Prototype secondary lenses based on the design were fabricated from acrylic and optical silicones. Testing of the prototype lenses revealed that acrylic secondary performed better than the silicone lenses in terms of the measured lumen output. Testing also showed that the fiber-optic cable temperature was within the maximum operating temperature of acrylic and didn’t suffer any high temperature damage during the five month long outdoor testing.