Fresnel Lens Array Research Articles

Fabrication of high-performance lens arrays for micro-concentrator photovoltaics using ultraviolet imprinting

Micro-concentrator photovoltaics (micro-CPV) is a cutting-edge CPV approach aimed at increasing the efficiency and reducing the cost and carbon footprint of solar electricity by downscaling concentrator solar cells and optics. The reduced size of micro-CPV provides several advantages over conventional CPV, including shorter optical paths and lower temperature and resistive losses in the cell, resulting in higher electrical efficiencies. This may increase the energy yield per area compared to conventional CPV or silicon modules. Cost reduction is achieved through material savings and the use of continuous manufacturing methods enabled by the tiny size of cells and optics, such as roll-to-roll (R2R) and roll-to-plate (R2P) ultraviolet (UV) imprinting for optics production. However, adapting these processes to large-area arrays of Fresnel micro-lenses with no wasted areas and high efficiency remains a challenge. In this study, we present a comprehensive methodology for the development of micro-CPV optics with full area coverage—from design and mastering to up-scaling, tooling, and replication. The methodology involves designing a non-rotationally symmetric elementary insert tailored to ultraviolet imprinting. Crucially, multiple inserts are originated via precision machining and recombined to form a single array master mold without wasted areas. The master is then replicated into a flexible working stamp for UV imprinting of Fresnel lens arrays, utilizing different UV curable materials. The functional characterization of the lenses demonstrates an optical efficiency of 80% at 178X under collimated white light, representing the highest effective concentration achieved using UV-imprinted Fresnel lenses. Furthermore, initial reliability tests confirm the absence of degradation during thermal cycling or outdoor exposure. This methodology paves the way for continuous high-throughput manufacturing of micro-lens arrays using R2R or R2P methods, presenting a significant step forward in micro-CPV.

A directionally illuminated pixel-selective flickering-free autostereoscopic display

A directionally illuminated pixel-selective flickering-free autostereoscopic display is proposed and demonstrated. The system consists of the U-shaped backlight, the mix-grooves cylindrical Fresnel lens array, a light shaping diffuser film, and a liquid crystal display with a directional light splitting element. Simulation is applied to obtain the crosstalk and the illuminance distribution at each viewpoint, which serves as design guideline for system structure and component parameters. The simulation and experimental results indicate that directional projection of parallax images is achieved for a high-quality flickering-free autostereoscopic display with a large viewing angle and continuous viewing volume. The crosstalk between left- and right-channels can be controlled down to 5.49%, while the resolution for each eye is more than a full HD. Furthermore, the alternative flickering in high refresh rate directional backlight autostereoscopic displays is removed by the proposed system, resulting in a high-quality and flickering-free viewing experience for multiple users.

Bionic Compound Eye Based on a Flexible Fresnel Lens Array

Bionic Compound Eye Based on a Flexible Fresnel Lens Array

Design of a high-power collimating optical system based on Fresnel lenses.

In light-emitting diode (LED) illumination (e.g., LED maritime lighting for ships), creating a uniform light environment for optical systems is an important challenge. In this study, we present a high-power collimating system based on Fresnel lenses, which allows high-brightness LED illumination in the earlier-mentioned remote distance. The work presented in this article focuses on improving the power, compacting the optical structure, and promoting the brightness of the spot. To prove the claims, the system with a total power of 1 kW is designed. The system consists of a 27 W LED array, a freeform surface lens array, and a confocal Fresnel lens array. In comparison with the traditional optical system, the optical structure shortens from 390 to 120 mm, and the divergent angle decreases from 3° to 2 . Meanwhile, the illuminance of the system is obtained as high as 230 lx at the near field of 200 m and 3.0lx at the far field of 1.5 nautical miles. This new method provides a practical and effective way to solve the problem of low power, insufficient illuminance, and long optical structure for LED array illumination, which is suitable for remote illumination and guidance of ships.

Fabrication of the curved Fresnel lens array on the spherical surface by 6-axis diamond ruling

The curved Fresnel lens array on the spherical surface owns exceptional optical performance and meets the growing demand for smart home and security alarm systems. However, the intricate three-dimensional microstructure of such optical component is typically considered impossible to be directly fabricated by diamond machining. In this paper, a novel 6-axis diamond ruling method is proposed to fabricate the complex optics utilizing a commercial 6-axis ultra-precision machine tool. The kinematic principle and tool path generation algorithm of this method are presented. A varying-angle sampling strategy is employed in the proposed algorithm to reduce the acceleration and following error in the rotation of the A-axis. Novel trial cutting processes are introduced to figure out the tool setting errors induced by visual inspection, which need to be compensated in the tool path. Based on the proposed tool path generation algorithm and cutting processes, this method enables the efficient processing of precise curved Fresnel lenses. There is no interference between the diamond tool and the curved microstructure in the 6-axis synchronized motions. Finally, the feasibility and superiority of this method are experimentally verified by analyzing the surface roughness and shape accuracy of the machined component. It can indeed generate high-quality curved Fresnel lenses on the spherical surface by the proposed 6-axis diamond ruling method.

P‐52: Higher Brightness Mini‐LED Displays: Optimizing Collimation and Uniformity in a Thinner Form Factor

We propose a novel method for improving brightness and efficiency of BEF‐less mini‐LED displays in a thinner form factor. In place of BEFs an array of Fresnel lenses positioned over each LED followed by micro lens array diffusion films create a uniform light output. Best practices and backlight design recommendations will be discussed.

“4+2” axis ultra-precision diamond shaping for partially overlapping Fresnel lenses based on an ultra-precision machine tool and two additional rotational axes

Optical surfaces and microstructures with high form accuracy and excellent surface quality are widely utilized nowadays and the diamond machining technology is still preferable for the fabrication of these workpieces. However, when machining surfaces featuring a high aspect ratio or intricate microstructures like monolithic microstructural optics, the machining efficiency is quite low and the cutting tool interference is inevitable for the existing diamond turning techniques. Hence, a novel method is proposed to machine such microstructures by introducing two additional rotational motions into the traditional ultra-precision machine tool. In this way, the arbitrary adjustment of the tool posture may be achieved in the machining process and intricate microstructures like monolithic microstructural optics can also be machined by the side cutting edge with high efficiency. The whole mechanical system and machining principle are presented firstly. Next, the tool path planning and the compensation for the tool tip offset are introduced. Then, the partially overlapping Fresnel lens array consisting of two segmented Fresnel lenses are fabricated and inspected. Finally, the measurement data are analyzed and the proposed method is validated to be able to fabricate such complex microstructures with high profile accuracy and surface quality successfully.

Viewing zone expansion of a dual-viewer autostereoscopic display with inclined interleaved linear Fresnel lens arrays and a time-division quadruplexing directional backlight.

A novel autostereoscopic display with a directional backlight unit using a pair of inclined interleaved linear Fresnel lens arrays is designed and evaluated. Different high-resolution stereoscopic image pairs are provided to each of the two viewers simultaneously by applying time-division quadruplexing. The viewing zone is enlarged in the horizontal direction by inclining the lens array, which enables two viewers to have specific views corresponding to the positions of their own eyes without interfering with each other's view. Thus, two viewers with no special goggles on can share the same 3D world, which enables direct-manipulation style interaction and collaboration maintaining eye contact with each other.

Multi-Degree-of-Freedom for Underwater Optical Wireless Communication with Improved Transmission Performance

Underwater optical wireless communication (UOWC) has great potential to provide high-speed and intensive communications over short ranges underwater. However, the mobility of the UOWC system is limited by the strict alignment requirements between the transceivers. In this paper, a multi-degree-of-freedom (MDOF) UOWC system with high flexibility and improved transmission performance is proposed and experimentally demonstrated based on the off-the-shelf light-emitting diode (LED) source. A hardware pre-equalization circuit is employed at the transmitter to extend the modulation bandwidth from 5.03 MHz to 50 MHz. At the receiving end, a Fresnel lens array is constructed to achieve efficient convergence of multiple incident optical signals from different directions. To improve the underwater signal transmission quality, we designed an additional digital signal recovery module after the trans-impedance amplifier. Finally, an experimental system is established with a 460 nm blue LED. The communication reliability of the system is verified by the measurement of the eye diagram and the bit error rate of the recovered signal at the receiving end. The experimental results show that optical signals from three different incident directions with a maximum data rate of 100 Mbps are reliably transmitted over a 1.2-m-long water tank using the non-return-to-zero on-off-keying modulation format.

Shaping of the Fresnel lens array on roller molds by 6-axis diamond machining

The Fresnel lens arrays are rapidly developing with the increasing demand for better optical performances and capabilities. For the roll-to-roll embossing of optical films, direct diamond machining of the Fresnel lenses on roller molds has been realized by installing an additional goniometer on the 5-axis ultra-precision machine tool in the previous study. However, this method owns two shortcomings, i.e., the communication delay between the machine tool and the goniometer and the poor positioning accuracy of the goniometer. In this paper, a 6-axis diamond shaping method is proposed to fabricate the Fresnel lens array on the roller periphery by utilizing a commercial 6-axis ultra-precision machine tool. It is ensured that the side cutting edge of the diamond tool matches the Fresnel lenses profiles during shaping. Also, the tool rake face is always perpendicular to both the roller tangent plane at the cutter location point and the cutting velocity relative to the roller via the synchronized rotations of the A-, B- and C-axes to avoid the tool–workpiece interference. The process to calibrate installation errors is introduced and utilized. The tool path is generated according to the cutting tool geometry, the lens parameters and the machine tool configuration. Experiments are carried out by machining the designed Fresnel lens array on a roller mold, which consists of lenses with different feature heights. The surface qualities of the lens arrays are evaluated and the influence of the block time to run the CNC code are also analyzed. The experimental results verify that the proposed method is effective and flexible for machining of the Fresnel lens array on roller molds.

A polarization modulated directional backlight autostereoscopic display

AbstractA polarization modulated directional backlight autostereoscopic display is proposed and demonstrated. The system consists of the orthogonally polarized backlight, the Fresnel lens array, a light shaping diffuser film, and a liquid crystal display (LCD) with a microphase retardation film. The autostereoscopic image pair carried by the directional light with different polarization directions is simultaneously projected to different spatial directions. The simulation and experimental results show that the directional projection of parallax images is realized for a high‐quality autostereoscopic display with large viewing angle and continuous viewing volume, hence making it suitable for practical applications.

Programmable plenoptic function for high-quality directional backlight autostereoscopy

A directional backlight autostereoscopy is characterized with well-collimated illumination directionality but generating a homogeneous distribution over the entire display screen over large viewing volume presents significant technical challenge. By taking advantage of the freedom to optimize the backlight, imaging optics and display panel, the adoption of plenoptic function is proposed and applied to the directionally illuminated autostereoscopy to provide viewers to perceive high-quality glass-free three-dimensional display at various viewing locations. With the programmable light-emitting diode arrays and liquid crystal display panel in conjunction with composite Fresnel lens array, an ideal autostereoscopic display is demonstrated. Assisted by retina-tracking and plenoptic function harnessing, high-quality autostereoscopy can be perceived within a large viewing volume with a conventional directional backlight autostereoscopic system but without using extra hardware component.

Optimizing optical fiber daylighting system for indoor agriculture applications

Optical fiber daylighting technology offers an effective path to deliver sunlight to an indoor farm that requires high energy consumption for illumination and a total visible spectrum for plant growth. However, the high cost of this technology can be seen as a drawback. In this study, the optimized daylighting system based on plastic optical fiber for indoor farm application is devised toward large-scale illumination with high efficiency and low cost. The proposed system comprises of a Fresnel lens array as a sunlight concentrator and plastic optical fiber bundles as a light transportation medium. Rather than previously common designs, we investigated the concentration properties of a non-imaging optics device – the Fresnel lens to find the optimal configuration of the system. Optimizing concentration ratio, optical efficiency, and overheating of an optical fiber daylighting system (OFDS) for the indoor farm application is carried out by simulation (LightTools software) and verified by experiments. The system design allows replacing the costly and sophisticated heat dissipation in conventional OFDS with only a UV-IR filter. The OFDS prototype is fabricated and tested in outdoor conditions. Results show that the proposed system archive concentration ratio of 140, the optical efficiency of ∼19 % by simulation, and ∼16 % by practice. Daylighting performance investigation on the installation of the prototype in the indoor farm demonstrates that energy saving can reach 54.3 % on a sunny day and 38.9 % on a cloudy day. Using proposed OFDS helps the plant to grow better than using LED only. Reliability tests and cost analyses show that our results provide an essential breakthrough for the application and commercialization of large-scale optical fiber daylighting technology for indoor agriculture.

A Drying system for Rhizoma et Radix Baphicacanthis Cusiae Based on multi-source coupling and efficient energy storag

The traditional Chinese Herbal Medicine Rhizoma et Radix Baphicacanthis Cusiae mostly grows in Southwest China. However, due to the lack of technology, the key drying process in the production of Rhizoma et Radix Baphicacanthis Cusiae has the problems of low efficiency, long time and uneven quality. The paper designed a drying system of Rhizoma et Radix Baphicacanthis Cusiae based on multi-source coupling and efficient energy storage by investigating the production of Rhizoma et Radix Baphicacanthis Cusiae in southwest China and studying the natural effects of geographical advantages and light conditions in the region. The main body of the system is composed of a two-position water tank heat circulation system, a hemispherical Fresnel lens array, an air source heat pump, a dehumidification and waste heat recovery device, a temperature and humidity sensor, and a heat exchange tube group. The drying system can better meet the drying needs of Chinese herbal medicine Rhizoma et Radix Baphicacanthis Cusiae. It has the advantages of high efficiency, energy conservation and environmental protection, stable operation, and can independently adjust according to the drying temperature. It has strong practicability. While saving energy, it saves high drying cost for farmers, and meets the special requirements of building intelligent agriculture and enriching rural economic business forms.

Innovation of Human Body Positioning System and Basketball Training System.

With the development of information management of sports events, basketball teams have higher requirements for the management of training data. The development of data visualization technology has provided convenience for information management which evolves from a digital management model to an efficient graphical management model. In this article, we will mainly design a human body positioning system based on wireless sensor networks. The weak signal from the sensor is tuned by the circuit, and the cylindrical Fresnel lens array is selected to modulate the field of view to ensure an effective response to the infrared signal of the moving human body. The wireless sensor network is used to integrate the human body detected by each pyroelectric sensor node, and the infrared signal is sent to the upper computer for analysis and processing. Through the host computer interface, observe and analyze the relationship between the detection signal of a single pyroelectric sensor and the position, speed, and movement of the moving human body, and deeply explore the operating process of the wireless pyroelectric infrared sensor network system. With the development of the new era, Chinese basketball training and teaching methods generally have some drawbacks, which have seriously affected the quality and effect of college basketball training and restricted the development of college basketball. Therefore, the focus of research is to solve these problems in order to achieve more effective college basketball training and education effects. This article mainly through the research of 5G technology wireless sensing human body positioning shows that wireless sensing technology has made great progress in its aspects, systematically analyzes basketball training, and proposes better training methods.

P‐65: Autostereoscopic Display for Two Viewers Providing Images Specific to Each Viewpoint

This paper proposes a novel autostereoscopic display with a directional backlight unit using a linear Fresnel lens array. In the proposed system, different stereoscopic image pairs can be provided to each of the two viewers simultaneously, and the viewing zone where two viewers can see the specific views for their own eyes without interfering with each other's view is enlarged.

Multi-user, high-resolution, high-quality directional backlight autostereoscopic display

Autostereoscopy with multi-user, high-resolution, homogeneous luminance, low crosstalk is realized with a directional backlight system consisting of specially tailored backlight and composite Fresnel lens array. Numerical simulation is applied to obtain the viewing zone distribution, which is found to be in good agreement with experiment. The dense-distribution of the backlight array allows the system to provide well-controlled directional illumination for multi-viewers while keeping high-resolution for each viewer. The experimental challenge for small crosstalk between left- and right-eyes for individual viewer, and minimized crosstalk between different viewers are fulfilled with high-quality optics design to allow the multi-viewers to simultaneously perceive 3D image. The crosstalk is controlled below 5%, and the homogeneity is above 85% while the resolution for each eye is kept at 1920*1080.

Harnessing and cloaking optical boundary in lens-array based display

Optical boundaries are basic structures for optical system and they become visible where reflection and refraction occur. The visible boundary is very often presented as a nuisance to optical systems in imaging recording or in display. Harnessing the optical boundaries up to a complete carpeting is scientifically interesting and technologically important. This work describes the concept, design, fabrication and testing of novel Fresnel lens array with tailored microstructures to carpet the optical boundaries while the functionality such as focusing and deflection can be retained. A gradually interleaved and periodically arranged micro-structured Fresnel lens sheet acting as low band pass filter lens array is proposed, fabricated and tested. The novel Fresnel lens array is demonstrated to remain the optical features for perfect planar display. When it is applied to a backlight illuminated display system, tailored illumination with local dimming further helps improving the visual homogeneity. The combined use of these new techniques allows the boundary cloaked completely over a large viewing directional range for broad visible spectra. The cloaking technique is applied as an immediate example to an autostereoscopic display system and is shown to be practical and valid for imaging and display optics.

Backlight system using an interleaved Fresnel lens array that attains a uniform luminance and two-dimensional directional light control.

A novel (to the best of our knowledge) Fresnel lens array is proposed to realize a uniform directional backlight with two-dimensional directionality. Autostereoscopic display with the proposed lens array improves image output quality and relieves the viewer's posture restriction without the need for any additional eye aid. In the proposed lens array, tiny prisms composing two adjacent linear Fresnel lenses are interleaved so that the two lenses may be virtually overlapped and work independently. The widths of the elemental prisms vary depending on the distance from the center of each lens. Thus, the light passing through the two lenses is mixed, which results in higher and more uniform luminance intensity. A prototype of an autostereoscopic display based on the time-multiplexed directional backlight method and made with the proposed lens array attained uniform luminance as well as low cross-talk between left-eye and right-eye images.

Design and fabrication of composite polygonal Fresnel lenses.

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.