Total Transmittance Research Articles

Compact athermalized LWIR objective lens

A new compact optical passive athermalized objective lens is designed with a focal length 120 mm and F-number 1.1. Its full field of view is 12.2°. The geometrical aberrations due to the large aperture and the wide field of view are well corrected as well as the chromatic aberration. Hence, the maximum RMS radius of the spot diagram over the full field of view is less than 17 µm and the Strehl ratio is 0.95 at 20 °C. The MTF is nearly limited in diffraction over the full F.O.V. This good correction of aberrations makes the optical system gain high resolution and suitable to work with a focal plane array detector with 17-µm pixel pitch. This performance is stable over a long temperature range from − 40 °C to + 65 °C. Moreover, the optical system is relatively compact “140 mm.” The total transmittance (after absorption consideration) of the optical system is enhanced from 6.6 to 94.07% at λ = 10 µm along the optical axis upon applying an anti-reflection coating.

Total transmittance measurement using an integrating sphere calibrated by a screen image synthesis system

The measurement of bidirectional scattering distribution function (BSDF) and total transmittance (TT) is a complicated issue. We have proposed a screen image synthesis (SIS) BSDF meter that provides high-speed and precise measurement. However, the measurement of TT using integrating sphere cannot offer a precise measurement. Therefore, we propose a calibration method that uses SIS BSDF meter and responsivity of the integrating sphere. It brings us not only precise BSDF function but precise TT measurement.

Design of IR zoom lens system for long-range detection in uncooled LWIR camera

A new compact optical zoom lens system with variable focal length 100–200 mm for uncooled LWIR (8–12 μm) camera is designed. It is used for long-range detection. The optimized IR zoom lens consists of four group elements. The F/# of the zoom system is F/1.4 at all zoom positions. Its performance reaches the diffraction limit at each focal length position. Moreover, optical design and image quality are calculated by ZEMAX optical software. The imaging quality performance is steady during zoom process. In addition to the above benefits, the optimized IR zoom lens is light and compact (200 mm) with 4 lenses and only one of them has diffractive surface to lower production cost. Upon applying anti-reflection coating, the total transmittance of the optical system is enhanced from 2 to 99% at λ = 10 µm.

Improvements of simplified hourly models for the energy assessment of buildings: The application of EN ISO 52016 in Italy

The Italian National Annex (NA) to EN ISO 52016-1 is aimed at improving the simplified hourly calculation method of the building thermal performance assessment by introducing different modelling options. The present work deepens the influence of the Italian NA improved method on the thermal energy needs for heating and cooling of a residential building-type in two different climate zones. In particular, the Italian NA improved options are applied one-at-the-time, and their effect is evaluated in comparison with the EN ISO 52016-1 standard method. The use of solar angle and time dependent correction factors for the total solar energy transmittance of glazing proved to be the most sensitive modelling option, among those analysed. Negligible variations were instead reported for the other tested options.

Methods of Preliminary Estimation of Total Solar Energy Transmittance (TSET) on a Sun Protected Window with Climatic Chamber and Hot Box Apparatus

Abstract The total solar energy transmittance (TSET, g - value) is a parameter of transparent system, which can significantly affect the heat demand for cooling of buildings in the summer. A wide range of progressive transparent and shading systems have been developed and applied to a large number of buildings. Their energy performance and efficiency can be determined using simulation tools or measurements. The methodology for accurate g - value determination is described in ISO 19467: 2017. The aim of the study was to derive and verify an alternative methodology for estimating the total solar energy transmittance of selected specimens of transparent systems in case when the standardized equipment is not available or the aim is not to know the exact TSET value. Window specimens were tested under laboratory conditions, which were retrofitted with elements that improve their original properties in terms of heat transfer coefficient and protection against overheating. In total, three methodologies were designed and described, based on A) monitoring of heat fluxes through glazing, B) monitoring of temperature rise in the hotbox and simulation, and C) determination of the difference in heat fluxes of an irradiated specimen and in the absence of radiation. A solar simulator and a heated hotbox were used for the measurements according to the needs of the chosen methodology. The results from the different approaches for determining g - values differ only slightly but are informative. The conclusion from all measurements is the fact that the tested specimens representing type of windows applicable in building retrofitting showed high potential in terms of reducing heat gains from the sun.

Effect of the TiO2 surface modification with 3-glycidyloxypropyltrimethoxysilane on the aggregation of cresyl violet: Application to a dye-sensitized solar cell

Dye aggregation is a typical phenomenon occurring in dye-sensitized solar cells (DSSCs), which causes a decrease in the electron injection efficiency from the photoexcited dye to titanium dioxide (TiO2). As this results in a decrease in the photovoltaic performance, it cannot be ignored in the study of DSSCs. This paper reports a DSSC involving a TiO2 electrode chemically modified by cresyl violet (CV) covalently attached to 3-glycidyloxypropyltrimethoxysilane (GPTMS). The aim of the study is to understand the influence of silane coupling agents (SCAs) on dye aggregation. Aggregation of CV occurring on the TiO2 surface was prevented by GPTMS treatment on the TiO2 surface. This result was revealed by the decreased absorption intensity of the dimeric band observed in the total transmittance spectra. Density functional theory calculations and fluorescence decay curve measurements indicated that the CV covalently attached to GPTMS acts as a photosensitizing dye in DSSCs. As a result, the photovoltaic performance of DSSCs containing CV was enhanced by preventing its aggregation upon GPTMS treatment onto the TiO2 surface (7-fold increase: 0.0020%–0.014%). We concluded that TiO2 surfaces treated with SCAs can help to prevent dye aggregation, and therefore, enhance the photovoltaic performance of DSSCs.

Fabrication translucent AlN ceramic under the strong magnetic field

The translucent aluminum nitride (AlN) ceramic was fabricated by pressureless-sintering at 1800 °C for 24 h in the flowing nitrogen atmosphere. The pore and different grains size of the sample was eliminated using CaF2 as the sintering additive. The total transmittance of the sample with 2 wt% CaF2 is enhanced 52.51% at 800 nm, which is 55% higher than that of AlN without CaF2. The grain orientation of the samples was adjusted by the slipping casting under the strong magnetic field. The a, b-axes of AlN are arranged from parallel to the direction of the magnetic field, and the c axis is arranged from perpendicular to the direction of the magnetic field due to magnetic susceptibility anisotropic of the grain. The birefringence phenomenon is reduced by the arrangement of the grains to a certain direction. The Lotgering factor and total transmittance of the texture AlN ceramic fabricated under the 9 T magnetic are up to 73.21% and 63.12% at 800 nm, respectively.

Preparation and Evaluation of Liposomes and Niosomes Containing Total Ginsenosides for Anti-Photoaging Therapy.

Ginsenosides are the principal bioactive compounds of ginseng. Total ginsenosides (GS) contain a variety of saponin monomers, which have potent anti-photoaging activity and improve the skin barrier function. To enhance the efficiency of GS transdermal absorption, GS liposomes (GSLs) and GS niosomes (GSNs) were formulated as delivery vehicles. Based on the clarified and optimized formulation process, GSL and GSN were prepared. The structure, cumulative transmittance, skin retention, total transmittance, and bioactivity of GSLs and GSNs were characterized. GSL and GSN were shown to inhibit lipid peroxidation and increase the contents of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in human keratinocytes (HaCaTs). In addition, HaCAT cell migration, proliferation, and GS cellular uptake were significantly increased. The therapeutic effects of GSL and GSN were also evaluated in a rat model of photoaging. Histopathological changes were assessed in rat skin treated with GSL, GSN, or GS by hematoxylin–eosin (H&E) and aldehyde fuchsine staining. Malondialdehyde (MDA), SOD, GSH-Px, matrix metalloproteinases (MMPs), interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) expression levels were determined. Results indicated that the optimal formulation of GSL used soybean lecithin (SPC) as the phospholipid, with a lipid–drug ratio of 1:0.4 and a phospholipid–cholesterol ratio of 1:3.5. The optimal temperature for the preparation process of GSN by ethanol injection was 65°C, with a ratio of the organic phase to aqueous phase of 1:9. It was demonstrated that the cumulative release rate, skin retention rate, and total transmission rate of GSL-7 at 24 h were higher than those of GSN-4 and GS. GSL-7 significantly inhibited skin lipid peroxidation caused by ultraviolet (UV) radiation. In addition, GSL-7 reduced the contents of MMPs and inflammatory cytokines in skin tissue. In conclusion, GSL-7 may reduce skin aging caused by UV radiation and contribute to skin tissue repair.

Optimization of Architectural Thermal Envelope Parameters in Modern Single-Family House Typologies in Southeastern Spain to Improve Energy Efficiency in a Dry Mediterranean Climate

The increasing regulatory requirements for energy efficiency in Europe imply a significant increase in insulation and solar control of buildings, especially in hot and semi-arid climates with high annual insolation such as the Spanish Mediterranean southeast. The consequences in architectural design to optimize compliance with the new technical and regulatory requirements of nearly zero-energy buildings are high. This paper analyzes the energy performance of a modern single-family house on the Spanish Mediterranean coast. The objective is to determine which design parameters most influence the energy improvement of this case study in order to establish design strategies that can be generalized to other new construction or energy retrofit projects, taking into account the specific characteristics of the warm and semi-arid Mediterranean climate. The scientific novelty of the work is to demonstrate that the design criteria of most modern single-family houses built or rehabilitated in the Spanish Mediterranean in the last decade comply with the energy efficiency requirements of Directive 2010/31/EU but are not specifically adapted and optimized for the special characteristics of the dry Mediterranean climate. This is the case of the house studied in this paper. The methodology used consisted of a systematized study of the main construction and geometric parameters that most influence the thermal calculation of this project: the thermal insulation thickness, thermal transmittance of the glazing, solar control of the glazing, total solar energy transmittance of the glazing with the movable shading device activated, size of glazing and the size of façade overhangs. The results obtained show that the use of mobile solar protection devices in summer, such as awnings or blinds, reduces the cooling need in summer up to 44% and the overall annual energy need (Cooling + Heating) up to 20%. This implementation is more efficient than increasing the thermal insulation of facades and glazing, reducing the size of windows or increasing overhangs. The most optimal solution is the simultaneous modification of several parameters. This reduces both heating need in winter and cooling need in summer, achieving an overall reduction in an annual need of 48%. This multiple solution improves the annual energy performance of the house much more than any solution consisting of modifying a single individual parameter. The results determine trends, explanations and deductions that can be extrapolated to other projects.

Effect of Shape, Orientation and Aging of a Plastic Greenhouse Cover on the Degradation Rate of the Optical Properties in Arid Climates

In arid climates, the optical properties of plastic-covered greenhouses deteriorate very quickly. To examine the effect of greenhouse shape and orientation on the degradation rate of cover optical properties, four greenhouse prototypes were constructed in two shapes (duo-pitched roof and tunnel), covered with a 200 µm thick low-density polyethylene film. Two types were oriented in the North–South direction, the other two in the East–West direction, and all were exposed for one year to an arid climate. Samples were taken from the different surfaces of each cover for testing. The total transmittance (Ts) and reflectance (Rs) of the samples were measured and averaged to obtain the whole cover properties (T and R). Measurements were carried out periodically every 30 days for the four prototypes. The degradation behavior of the optical properties of each cover surface (Ts, Rs) and the whole cover (T, R) was investigated for the four film covers during the exposure time. Results show that the degradation rate of Ts depends on the surface location and the cover orientation. Among the different surfaces of the four prototype covers, the maximum difference in the Ts value between the E and N surfaces for the tunnel cover oriented in the N–S direction was 15.5%. Although the variation of the Ts value among the different cover surfaces was found, the time dependences of the whole cover transmittance (T) for the four covers tested were almost similar. Accordingly, the shape and orientation of the small size greenhouses did not significantly affect the degradation rate of the cover optical properties. In the four covers tested, the reduction in the global solar radiation transmittance (T) was 27–31% after one-year exposure compared to the new film. Nonlinear correlation was developed to predict the degradation rate of the cover transmittance as a function of the accumulated solar irradiance.

Assessment of the 20L SODIS bucket household water treatment technology under field conditions in rural Malawi.

Two billion people worldwide consume unsafe drinking water. The problem is particularly pronounced in Sub-Saharan Africa, where more than a quarter of the population relies on unimproved surface water sources. Based on the principles of solar water disinfection (SODIS), a new household water treatment technology, the SODIS bucket, was developed to improve the microbial quality of water from these sources based on controlled tests in a laboratory setting. This study set out to evaluate the efficacy of the technology in a field setting, in rural communities in the Chikwawa District in southern Malawi. SODIS experiments were carried out in two different vessels (1-L PET bottles and 20-L polypropylene SODIS buckets), over three months using unprotected water sources normally used by community members. Vessels were exposed to direct sunlight for 8h per day in a village setting and were sampled at regular intervals to determine total coliforms, E. coli, turbidity, UV transmittance and UV dose. In these experiments, the SODIS bucket reached inactivation targets for E. coli (<1CFU/100mL) in two of seven experiments and for total coliforms in one of seven for total coliforms (<50CFU/100mL), despite having greater UV doses than were seen in the evaluation carried out under controlled conditions during the bucket's development. PET bottles reached inactivation targets for both E. coli and total coliforms in five of seven experiments. There was no single factor that could be identified as preventing adequate inactivation, but the role of organic matter, inconsistent nature of the water source, and vessel size, when coupled with organic matter, were identified as contributing factors. This study highlights the need for further prototyping to provide a suitable pre-treatment step for unprotected water sources, and the importance of field testing with real-life parameters to ensure new technologies are context appropriate.

SSolar-GOA v1.0: a simple, fast, and accurate Spectral SOLAR radiative transfer model for clear skies

Abstract. The aim of this work is to describe the features of and to validate a simple, fast, accurate, and physically based spectral radiative transfer model in the solar wavelength range under clear skies. The model, named SSolar-GOA (the first “S” stands for “spectral”), was developed to evaluate the instantaneous values of spectral solar irradiances at ground level or at a given altitude of the atmosphere. The model requirements are designed based on the simplicity of the analytical expressions for the transmittance functions in order to be easily replicated and applied by a wide community of users for many different applications (atmospheric and environmental research studies, satellite remote sensing, solar energy, agronomy and forestry, ecology, and others). Although spectral, the model runs quickly and has sufficient accuracy for the evaluation of solar irradiances with a spectral resolution of 1–10 nm. The model assumes a single mixed molecule–aerosol scattering layer where the original Ambartsumian method of “adding layers” in a one-dimensional medium is applied, obtaining a parameterized expression for the total transmittance of scattering. Absorption by the different atmospheric gases follows “band model” parameterized expressions. The input parameters must be realistic and easily available since the spectral aerosol optical depth (AOD) is the main driver of the model. The validation of the SSolar-GOA model has been carried out through comparison with simulated irradiance data from the libRadtran package and with direct and global spectra measured by spectroradiometers. Thousands of spectra under clear skies have been compared for different atmospheric conditions and solar zenith angles (SZA). The SSolar-GOA is validated by a quantitative comparison with libRadtran, showing that it underestimates direct normal, global, and diffuse spectral components with relative differences of +1 % (RMSE % = 4.6–8), +3 % (RMSE % = 5.3–8), and 8 % (RMSE % = 9.3–9.6), respectively, when the SZA varies from 6 to 60∘. Compared with the measured irradiance data of the LI-1800 and ASD spectroradiometers, the relative differences of direct normal and global components are within the overall experimental error, about ±2 %–12 % (RMSE % = 5–8.3), with underestimated or overestimated values. The diffuse component presents the highest degree of relative difference that can reach ±20 %–30 % and RMSE of 25 %–50 %. The relative differences depend strongly on the spectral solar region analysed and the SZA, but the high values of RMSE are due to the artifice generated by the different spectral resolution of the absorption coefficients of both models. Model approach errors combined with calibration instrument errors may explain the observed differences. The SSolar-GOA v1.0 is implemented in Python and open-source licensing.

Substrate-wave-induced antireflection in metasurfaces.

We address the antireflection (AR) properties of periodic surfaces, or metasurfaces, supporting substrate waves. The work is motivated by recent literature where AR bands formed by substrate-wave propagation are incorrectly attributed to Mie scattering. In contrast, as clearly shown here, substrate-wave generation with corresponding AR signatures is a diffractive effect due to a periodic lattice and is not due to particle scattering as in Mie resonance. Treating both 1D and 2D surfaces, we demonstrate a clear quantitative connection between major AR loci and corresponding total substrate transmittance loci via maps in period versus wavelength. As shown, this holds for fully dispersed, lossy surfaces as well. The results presented here serve to elucidate the physical properties of periodic metasurfaces placed on substrates admitting propagating diffraction orders and may inform the design and implementation of grating-based AR structures.

Highly Transparent, Colorless Optical Film with Outstanding Mechanical Strength and Folding Reliability Using Mismatched Charge‐Transfer Complex Intensification

AbstractThe development of flexible displays and electronics is hindered by the disadvantages of polymeric window films, such as low mechanical strength, poor optical properties, and lack of folding and rolling reliability. To overcome these critical limitations, a novel colorless polyimide window film is prepared in this study using the concept of charge‐transfer complex (CTC) intensification. The resulting window film has a tensile modulus of 8.4 GPa, total transmittance of ≈90%, and yellow index below 3, which is the best recorded balance between mechanical strength and optical properties for a highly flexible optical film. Unlike commercially available optical‐grade engineering plastic films and glass substrates, the prepared window film has both pencil hardness grade over 2H and folding reliability over 200 000 folding/unfolding cycles. These remarkable properties are attributed to the unique supramolecular structure with multiple hydrogen bonding and salt complexation interactions, which exhibits CTC intensification. The CTC intensification mechanism is also proposed in this study.

Estimation of Total Solar Transmittance for Twin-Wall Polycarbonate Sheet with Rectangular Structure on the Basis of Experimental Research

The consumption of heat energy as well as electric power in an exploitation process of a building construction depends among others on properties of materials applied to construct its partitions. Increasingly, glass is being replaced by plastics in transparent partitions, including multi-wall polycarbonate sheets. Light transmission and solar radiation transferred to the object’s inside through transparent partitions are decisive factors for its lighting and energy balance. The present paper presents an analysis, on an experimental basis, of the changes of total solar transmittance (TST) for a clear twin-wall polycarbonate sheet with a rectangular structure applied as a swimming pool enclosure. Research shows that values of the above parameter do not depend meaningfully on cloudiness but on time of day. Values of TST can change in the daytime depending on incidence angles and on shares of direct and diffusive solar radiation in global solar radiation. TST values are in the range 0.6–0.7, and they are lower than the value of 0.8, which is given by the producer in the product card.

Reconciling the Conflict between Optical Transparency and Fouling Resistance with a Nanowrinkled Surface Inspired by Zebrafish's Cornea.

Surface topography has been demonstrated as an effective nonchemical strategy for controlling the fouling resistance of a surface, but its impact on optical transparency remains a barrier to the application of this strategy in optical materials. To reconcile the conflicting effects of surface topography on optical transparency and fouling resistance, here we study the optical properties and antifouling performance of nanowrinkled surfaces inspired by the corneal surface of zebrafish (Danio rerio). Experimental and numerical analyses demonstrate that a good compromise between optical transparency and antifouling efficacy can be achieved by wavy nanowrinkles with a characteristic wavelength of 800 nm and an amplitude of 100 nm. In particular, the optimal wrinkled surface under study can reduce biofouling by up to 96% in a single-species (Pseudoalteromonas sp.) bacterial settlement assay in the laboratory and 89% in a field test while keeping the total transmittance above 0.98 and haze below 0.04 underwater. Moreover, our nanowrinkled surface also exhibits excellent resistance against contamination by inorganic particles. This work provides a nonchemical strategy for achieving the coexistence of optical transparency and fouling resistance on one single material, which implies significant application potential in various optical devices and systems, such as antibacterial contact lenses and self-cleaning solar panels.

Texturing of polydimethylsiloxane surface for anti-reflective films with super-hydrophobicity in solar cell application

This study utilized a Cu metal assisted chemical etching (MACE) method to produce an anti-reflection texture on poly dimethyl siloxane (PDMS). We measured the diffuse and total transmittance, total reflectance, and haze ratio to analyze the optical properties of the textured PDMS films, which were confirmed using finite-difference time-domain (FDTD) calculations. The anti-reflection textured PDMS films exhibited improved optical performance in the visible light region, owing to the light scattering and trapping effect, by improving the lateral surface area and aspect ratio of the micro/nanostructures. The average reflectance was 2.86% under optimal conditions. The optimized structures of the films also showed super-hydrophobicity (θCA≈155.2°). We applied the optimized film to perovskite photovoltaic solar cell devices and observed an enhanced short-circuit current density (Jsc) from approximately 21.95 to 24.06 mA/cm2 (∼9% increase). The improved Jsc increased the PCE to 17.11% (∼11% increase) in the MAPbI3 p-i-n structured devices. Based on the results, we confirmed that the superhydrophobic anti-reflection PDMS film can be used to overcome the limitation of light absorption in solar cell applications.

Influence of growth temperature on light trapping properties of ZnO:Al nanorods grown on seed layers with crater-like structures

We report the growth and characterization of textured ZnO:Al (AZO) films with excellent optoelectronic properties. The surface morphology depended strongly on growth temperature; in particular, the effect of hydrothermal growth temperature on the optoelectronic properties and light trapping abilities of AZO nanorods grown on the crater-like AZO seed layers was investigated systematically. The AZO nanorods grown at 110°C were relatively dense, indicating that hydrothermal growth temperature can promote the growth of AZO nanorods along the direction perpendicular to the substrates. The difference in the height and orientation of AZO nanorods prepared at 100°C resulted in significant enhancement of light trapping abilities. In addition, the textured AZO films maintained low sheet resistance and high total transmittance.

High strength holocellulose paper from bamboo as biodegradable packaging tape

As the fast-growing of package business in express delivery industry, replacing traditional scotch tapes with degradable materials has attracted extensive attention. Herein, holocellulose paper (H-paper) was prepared by an efficient delignification and papermaking process from bamboo. The structure and properties of resultant holocellulose fibers and H-paper were characterized and compared with those from other pulping methods, such as Kraft pulping, enzyme treated, sulfite and alkaline sulfite process. The yield of holocellulose pulp (55%) increased by about 10% compared with that of other fibers. Compared to that of Kraft paper (38 MPa), the strength of H-paper increased by nearly 60% at similar density, reaching a maximum of 65 MPa. The total transmittance of H-paper was about 20% higher than Kraft paper. Moreover, H-papers displayed high mechanical properties, good printability, and degradability, which was important for the application as paper tape.

Accuracy of retrieving optical properties from liquid tissue phantoms using a single integrating sphere.

Using integrating spheres (ISs) in conjunction with the inverse adding-doubling algorithm (IAD) offers a well-established, rigorous protocol for determining optical absorption (μa) and reduced scattering (μs') coefficients of thin, optically homogeneous, turbid media. Here, we report the performance and use of a single IS system for experimentally retrieving optical properties in phantom media whose optical properties were well controlled. The IS system was used to measure the total reflectance and transmittance between 500 and 800 nm in liquid phantoms that were prepared to span a wide range of optical scattering and absorption coefficients. Measurements on phantoms were sequentially made using one of two broadband light sources-a halogen lamp or a supercontinuum laser. We report on the accuracy of IAD-derived optical coefficients using IS measurements made on phantoms-directly or by employing one of two previously reported correction methods. The first (sample-substitution error) correction was experimentally achieved while the second used Monte Carlo-based corrections with IAD. When experimentally calibrated reflectance and transmittance values were directly used as inputs to the IAD, mean absolute errors in recovered optical coefficients were larger than 0.4cm-1 for absorption and more than 6cm-1 for scattering across all phantoms and wavelengths measured. These errors reduced to 0.06-0.17cm-1 and 0.7-2cm-1 for μa and μs', respectively, with the use of corrections. Choice of light sources used, sample geometry (relative to optical coefficients), signal-to-noise of measurements, and the selection of correction methods are discussed.