With the rapid advancement of light-emitting diodes (LEDs), front fog lamps using LEDs have become a main emphasis for vehicle lighting. For vehicle lighting, the front fog lamps should provide a bar-shaped beam of light with a sharp cutoff at the top and are designed to increase the illumination directed toward ground at a sharp angle. In this study, an innovative lens design based on a freeform surface responding to the requirements of the vehicle lighting is proposed. The design of the two-axis asymmetric freeform lens for LED front fog lamp can meet ECE R19 class F3 regulation without any other lens or reflector.
As an application of the PV technology, building integrated photovoltaic (BIPV) technologies have attracted an increasing interest in the past decade. One of these BIPV elements is the luminescent solar concentrators (LSCs). The LSC consists of a transparent plate embedded with luminescent dyes or inorganic particles, and the solar cells are attached on one or more sides. The incoming sunlight absorbed by the luminescent dyes or inorganic particles re-emits at a longer wavelength, and part of the re-emitting light trapped in the transparent plate reaches the PV cell attached on the LSC and convert it to electricity. However, the efficiency of the LSCs is still low at this stage. The surface loss on the top surface of the transparent plate is one of the main losses in LSCs. The prism film in liquid-crystal display (LCD) module is used to collimate the light in the module and enhance the overall brightness, and would be used in the LSCs to enhance the incoming sunlight to the solar cells attached on the end of the transparent plate. Then the design of the prism film is important. In this study, the ray-tracing simulation is used to investigate the optical characteristics of the LSC with the prism film covered on the top surface of the transparent plate. Different structure of the prism film will be considered to enhance the light reaches the PV cell attached on the LSC.
The reabsorbing effect will prevent the receiving energy for the solar cell attached to the edge of a luminescent solar concentrator from increasing with the illuminated area. The conventional solar concentrator adopts a uniform luminescent layer made of only one type of phosphor or dye. When the light generated in the region of the luminescent layer far away from the solar cell propagates to the solar cell by multiple total internal reflections, it will have more chances to be reabsorbed when it enters the region of the luminescent layer near to the solar cell. We investigate how the reabsorption effect can be reduced by using a luminescent layer made of multiple phosphors such that the region with the phosphor absorbing the longer wavelength is arranged to cover the region nearer to the solar cell. Experimental results show that the proper coverage with multiple phosphors can reduce the reabsorption effect in our luminescent solar concentrator under test.
Effects of a coating combination, a prism film and a phosphor layer on the short current of the solar cell in the optical solar concentrator and the illuminance of the sunlight passing through the samples were investigated. The optical solar concentrator was a 50 mm x 50 mm x 5 mm B270 thick glass with its sides connected by a solar cell. The prismatic structure of the prism film had a period of 50 μm. A phosphor Y560 having an absorption band of 390 nm to 500 nm and emitting from 490 nm to 700 nm was prepared. Six coating combinations applied in this study were composed of optical filters and glass. The optical filters included infrared cut-off, magenta, red, green and blue filters. The deflection angle was between 31 and 33 degrees when the incident sunlight passed through the prism film. The short current of the solar cell in the optical solar concentrator with the prism film, the coating combination and the phosphor layer was largest in this study. Experimental results show that the coating is more suitable for enhancing the short current than the phosphor layer in the optical solar concentrator with the prism film. And the phosphor layer can increase the illuminance of the sunlight passing through the samples due to the human eye sensitivity.
The Luminescent Solar Concentrator (LSC) consists of a transparent plate with solar cells on one or more sides. The incoming sunlight is absorbed by the luminescent dyes or particles, which are embedded in the transparent plate or applied in a film on the top or bottom of the transparent plate. The absorbed light is re-emitted at a longer wavelength, and part of the re-emitting light is trapped in the transparent plate by total internal reflection (TIR). Then the solar cells attached to the edges of the transparent plate would collect the light and convert it to electricity. However, the luminescent dyes or particles used in the conventional LSC still suffer from reduced efficiencies and lifetimes, then the inorganic phosphors with relatively high quantum yields, good absorption properties and longer lifetime could be alternative materials used in the structure. In this study, the ray-tracing simulation is used to investigate the optical characteristics of the LSC with the inorganic phosphors embedded film on the top or bottom of the transparent plate. The simulation results will also be used to study the loss mechanisms in the LSC with inorganic phosphors embedded film.
Due to the advantages, such as high efficiency, power consumption reduction, no mercury, pure saturated color, high reliability and long lifetime, the solid-state lighting based on light-emitting diodes (LEDs) has become very popular at this stage. In the lighting applications such as spot lighting, downlighting, architectural and show lighting, the colortunable properties with collimating beam of LEDs are highly demanded. The color–tunable lighting is easily achieved using multi-colored LEDs instead of inefficient color filters. However, the applications of multi-colored LEDs usually appear the undesirable light patterns such as color separation or color fringes. At the meantime, the use of TIR (total internal reflection) lens for multi-colored LEDs to collimate the light from the LEDs with different color will introduce seriously undesirable artifacts. Thus, a periodic microstructure surface on the top surface of the TIR lens would be used to reshape the light from the different colored LED chips in the multi-colored LEDs, and then decrease the color separation and color nonuniformity. In this study, the TIR lens with periodic microstructure surface on the top surface would be used to collimate the light from multi-colored LEDs with low color separation or color fringes. The analysis of color enhancement and collimation features of the multi-colored LEDs with different periodic microstructure on the top surface of the TIR lens is presented.
In this study, the design of the projector type headlamp using LEDs with different structure parameters is proposed. The
ellipsoidal reflector with different major and minor axis would contribute different aperture and focal lengths of the
ellipsoidal reflector, and then collimate the light to the converging lens. With specific converging lens and metal-based
baffle plate in the projector type headlamp system, we systematical analysis of the ellipsoidal reflector in the projector
type headlamp. The systematical analysis of the ellipsoidal reflector can be a reference to design a projector type
headlamp with compact size and high photometry performance.
In this study, multivariate data analysis, especially partial least squares regression (PLSR), is applied to analyze the near infrared absorbance spectra of fruit samples in order to acquire the inner qualities without destroying the samples. The calibration models have been established for the samples with raw data, first order derivative and second order derivative treatments, respectively. In the meantime, the models have been verified by using cross validation method. As anticipated, a model with higher correlation coefficient (r) and lower root mean square error of calibration (RMSEC) is preferred for both calibration and cross validation. The results reveal that the calibration models with second order derivative treatments have higher correlation coefficient, coefficient of determination, as well as lower RMSEC. Furthermore, the calibration models have been optimized by selecting partial wavelengths as new variables based on absorbance spectra and regression coefficient. The reasons why the calibration models are improved might be suitably cutting off partial wavelengths causing noises in the model.
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