Fresnel Lens Structure Research Articles

Hybrid high-concentration photovoltaic system designed for different weather conditions

In this study, we propose a novel high-concentration photovoltaic (HCPV) cell by considering both the light leakage characteristics of the Fresnel-lens-based solar cell modules and the performance issues arising from cloud shading in practical use. We use our self-constructed systems to conduct field measurements for up to half a year under various environmental conditions. According to the acquired results, it was surprising to know that in the area other than the focusing area, the so-called light leakage region, there always bears illuminance of about 20,000–40,000 lx whether it is a sunny day or a cloudy day with different cloud conditions. Such an interesting result is caused by the light scattering of the clouds and the inherent leakage characteristic of a Fresnel lens. To prove this important finding, we simulated the illuminance of the Fresnel lens structure used in the measurement with apertures of different sizes to determine the detected area. In the laboratory, the diffuse plates were used to mimic the situation of varying cloud layer thicknesses. The trend of calculated and measured results fitted well with the field measurements. Also, the experimental and simulation results show that the round angle and draft facet of the Fresnel lens were responsible for light leakage. This finding prompted us to propose a hybrid high-concentration solar module in which more cost-effective polycrystalline silicon solar cells are placed around the high-efficiency wafer of HCPV to capture the dissipated light leakage and convert it into usable electricity.

Ultraprecision machining and on-machine measurement of the radial Fresnel lens structure array of a large-scale roller mold.

Automation and on-machine manufacturing process measurement is essential in increasing product productivity. However, a significant challenge is the radial Fresnel lens structure-array machining and on-machine measurement research for a large-scale roller mold. We present a rotating A-axis machining method for manufacturing an array of a radial Fresnel lens structure, based on an ultraprecision four-axis drum roll lathe system developed by the team. Therefore, based on the principle of a virtual multiprobe, the traditional two-point method is improved and applied to the on-machine measurement of the radial Fresnel lens structure of the roll mold. Through the machining and on-machine measurement experiments of the radial Fresnel lens structure of the roller mold, the feasibility of the machining method and measurement method is verified.

Ultra-precision machining of polygonal Fresnel lens on roller mold

Roll-to-roll (R2R) embossing is a low-cost and high-productivity manufacturing process that replicates the microstructures from a cylindrical impression mold onto flexible films with high resolution and accuracy. However, discontinuous non-rotationally symmetric microstructures are very difficult to fabricate on either planar or cylindrical surfaces. In this paper, a novel machining method, diamond micro-scraping (DMS), is developed to provide a possible solution for the fabrication of polygonal Fresnel lens structure on the roller mold. In the proposed DMS machining method, the tool path is generated according to geometrical calculations considering the structural design of the drum roll lathe, the polygonal Fresnel lens structure designed, diamond tool geometries, and parameters of the roller mold. Through a series of processing experiments, the feasibility of DMS machining method is verified, and polygonal Fresnel lens structure is fabricated on the roller mold. The experimental results show that the profile accuracy of the processed polygonal Fresnel lens structure is at the submicron level and the surface roughness is several nanometers. The proposed DMS machining method can meet the requirement of embossing high-precision optical roller mold.

P‐148: A Continuous Variable Lens System to Address the Accommodation Problem in VR and 3D Displays

The focus cue is a continuing concern within the field of Virtual Reality (VR), Augmented Reality (AR) and 3D displays. Although liquid crystal (LC) based lens is an excellent candidate for tunability, a major problem with VR/3D application is a need for large aperture not inhibiting the field of view, but that also maintains a reasonable switching time. In this paper we discuss results with two systems that can be used for such application. We present the result of user preference for an approach using a Fresnel lens structure, and propose a second design that is a hybrid system comprised of refractive Fresnel and Pancharatnam‐Berry LC lenses. Our study presents a compact, large aperture, fast and tunable optic that can be used in numerous applications including VR/3D systems.

The Design of Freeform Surface Fresnel Lens Used for LED Uniform Illumination

This paper presents a new kind of light emitting diode(LED) secondary light distribution lens which adopts the type of Fresnel lens surface. The research purpose of this paper is to improve the LED heat dissipation efficiency of the secondary light distribution lens and the light efficiency, so as to prolong the service life of the LED. In this paper, we use the numerical method for solving the partial differential equation to establish a freeform surface lens which could produce uniform illumination, then the innovative method of combine the Fresnel lens structure with freeform surface lens was proposed. The design of freeform surface Fresnel lens allows dramatically cut the thickness of the lens (as well as the weight and volume) , it can solve the problem of difficulty in heat dissipation. By comparing the ray tracing simulation results of original freeform surface lens and freeform surface Fresnel lens in optical simulation software, experiments show that the latter not only shows the same degree of illumination uniformity, but also greatly reduced the thickness of the lens.

Fabrication of Thin-Film Fresnel Optics by Combining Diamond Turning and Photolithographic Processes

A novel fabrication process is proposed for manufacturing thin-film metal Fresnel lenses for X-ray applications. This process combines diamond turning technology and photolithographic processes. To prevent thin-film lens substrates from deflection during diamond turning, films were prepared on single crystalline silicon wafers by electrolytic plating. After the Fresnel lens structure is generated on the metal thin films by diamond turning, the silicon substrate was then removed selectively by reactive ion etching. Experimental results demonstrated that the proposed hybrid fabrication process achieves submicron form accuracy and nanometer surface roughness.

UP SCALING AND TEST RESULTS OF AN ADVANCED FRESNEL GREENHOUSE

A greenhouse with Fresnel lenses in the south facing roof and a receiver for concentrated Photovoltaics with water cooling (CPVT system) will result in electrical and thermal energy output from the solar energy excess entering a greenhouse. The PV system converts about half of the direct radiation into heat and electricity. During periods with direct radiation this will significantly reduce the heat load on the greenhouse. For an optimal performance the roof elements must be asymmetric with a steep inclination at the north side (the exact angle of course depends on the latitude of the building site). The Fresnel lens structure is best oriented in upwards direction. In the current design, two lenses are placed in the inner space of a double glass. This prevents pollution and condensation on the lenses. By the upward facing of the lens structure, the focus quality is preserved over a much broader range of angles of incidence compared to a lens with downward facing structures. Each PMMA lens with a size of 1.20×1.52 m is composed of 12 ‘tiles’ for easy production. The focal distance of the lens is 1,875 m and the geometrical concentration factor is 50×. This means that in most cases the focus line is thinner than 3 cm. The performance of the lens with respect to the shape of the focal area and the position of the focal line has been analyzed with ray tracing techniques. From this analyses and by the development of a smart tracking system only two motors can bring the receivers in the required positions. One motor controls the distance between lens and receiver and the other controls the translocation of the receivers parallel to the lens. The second conclusion was that the positions of the focal line are within the bounds of the greenhouse construction for almost the whole year. Only in winter, in the early morning and at the end of the day, the focal line will be unreachable. The 480 m2 greenhouse, with the LCPVT system based on Static Fresnel lenses and a 40 m CPVT-module and a 200 m CT-module, is designed by Bode Project Engineering and constructed by Technokas in Bleiswijk the Netherlands.

Stop grating for perfect replication of micro Fresnel lens by thermal imprinting

A stop grating concept is proposed to improve polymer filling in the thermal imprinting of a micro Fresnel lens structure. The stop grating consists of line and space structures outside the Fresnel lens pattern zone area. The experimental results have proved that the stop grating can help to achieve the complete filling of a mold, at the same time acting as a stop to prevent possible damage to the mold surface relief structures during imprinting press. A computer simulation was carried out to identify the phenomena of micro-holes at the edge of imprinted pattern. By removing the cavity between the pattern area and stop grating, perfect imprinting results have been achieved.

Fabrication of Thin-Film Fresnel Optics by Combining Diamond Turning and MEMS Techniques

A novel fabrication process was proposed for manufacturing thin-film metal Fresnel lenses for X-ray applications, which combines MEMS technologies and diamond turning technology. To prevent thin-film lens substrates from deflection during diamond turning, the thin films were prepared on single crystalline silicon wafers by electrolytic plating. After the Fresnel lens structure has been generated on the metal thin films by diamond turning, the backside supporting silicon substrate was selectively removed by reactive ion etching. Experimental results demonstrated that submicron level form accuracy and nanometer level surface roughness could be achieved by the proposed hybrid fabrication process.

Microplasma object imaging spectroscopy by using zone plate surface structure on mica crystal

A new method is proposed for obtaining spatially resolved multicharged ion spectra of microplasma sources with resolution better than 0.5 μm. The method is based on making a Bragg–Fresnel lens structure on a mica crystal surface. The lens was formed in a direction normal to the direction of dispersion and was used for the investigation of plasma created in nanosecond X pinch. The method may be used in studies of plasma heated by pico- and femtosecond laser radiation.