High Luminance LED Research Articles

Thermo-optical coupling applied to high luminance LED used in automotive front lighting

Automotive front lighting evolved towards high definition beams. To create such function, up to several light source per square millimeters are involved. The current trend tends to replace multiple LED designs with only one high luminance LED. The 10W-optical power emitted by this optoelectronic source induces high energy density that requires to be thermally managed. Moreover, when this LED is integrated within its optical system, the radiation concentration can lead to the system self-heating, leading to early damage or failure. The strategy adopted in this paper to avoid the component failure consists in developing an accurate and robust multi-physics simulation to predict heat transfer in a LED lighting system. In this paper, the validation of a high luminance LED thermo-optical coupling model is achieved by comparing numerical simulations with experimental results. The full optical characterization of LED has been performed to build its opto-thermal model. Then, an experimental set-up has been designed and consists in positioning a black plate in front of the LED, to capture its self-heating induced by light energy absorption using infrared thermography. The agreement between thermo-optical simulation and IR thermography is fair, which reinforces the use of the model with an error lower than 10%.

Dynamic Autonomous Identification and Intelligent Lighting of Moving Objects with Discomfort Glare Limitation

The importance of reducing discomfort glare during the dynamic development of high luminance LEDs is growing fast. Smart control systems also offer great opportunities to reduce electricity consumption for lighting purposes. Currently, dynamic “intelligent” lighting systems are a rapidly developing field. These systems, consisting of cameras and lighting units, such as moving heads or multimedia projectors, are powerful tools that provide a lot of opportunities. The aim of this research is to demonstrate the possibilities of using the projection light in dynamic lighting systems that enable the reduction of discomfort glare and the light pollution phenomenon. The proposed system allows darkening or reducing the luminance of some sensitive zones, such as the eyes or the head, in real-time. This paper explores the development of the markerless object tracking system. The precise identification of the position and geometry of objects and the human figure is used for dynamic lighting and mapping with any graphic content. Time measurements for downloading the depth maps, as well as for identifying the human body’s position and pose, have been performed. The analyses of the image transformation times have been carried out in relation to the resolution of the images displayed by the projector. The total computation time related to object detection and image display translates directly into the precision of fitting the projection image to a moving object and has been shown.

Measurements and theoretical estimation of N2-broadening and -shifting coefficients of the water vapor spectral lines in the 22,330-22,590 cm−1 region

The water vapor line broadening and shifting coefficients for 36 strongest water vapor lines in the 22,330-22,590 cm−1 spectral region (6ν1+ν3 and 7ν1 bands) induced by nitrogen pressure have been measured with a spectral resolution of 0.1 cm−1 at room temperature by a Fourier transform spectrometer using a high luminance LED source. A high signal-to-noise ratio (S/N ≈ 10 000) allows one to analyze the lines with intensities from 1.25 × 10−25 to 1.15 × 10−26 cm/molecule. The N2-broadening and shifting coefficients have been calculated by a semi-empirical approach that estimates the line profiles based on anharmonic wave functions; this method explicitly takes into account all scattering channels induced by collisions.

Focus on analytical equipment, spectroscopy, and spectrometry

Focus on analytical equipment, spectroscopy, and spectrometry

Visual Characteristics of Afterimage under Dark Surround Conditions

Three psycho-visual experiments were carried out to investigate visual afterimage characteristics of high luminance LEDs under dark surround conditions. The results show that the luminance of illumination, exposure time and background luminance are the primary factors influencing the afterimage’s duration, the color difference between stimulus and background, and visibility. Besides, visual afterimage characteristics are strongly correlated with the luminance contrast between the stimulus and the background, but not for the color difference with a white background. A third-order polynomial regression model was proposed to accurately estimate the afterimage duration, the color difference between stimulus and background, and visibility. The model performance showed high R-squared, low root-mean-square error (RMSE) and mean absolute error (MAE) values between the predicted and visual characteristics.

Measurements of N2-broadening and -shifting parameters of the water vapor spectral lines in the 19,560–19,920 cm−1 region using FT-spectrometer with LED source

The water vapor line broadening and shifting coefficients for about 91 strongest water vapor lines in the 19,560–19,920 cm−1 spectral region induced by nitrogen pressure are measured with a spectral resolution of 0.05 cm−1 at room temperature by a Fourier transform spectrometer using high luminance LED light source. A high signal-to-noise ratio (S/N ≈ 10 000) allows one to analyze the lines with intensities from 1.54 × 10−23 to 2.0 × 10−26 cm/molecule. The multi-spectrum fitting procedure was used to fit line broadening and shift parameters of the 5ν1+ν3, and 6ν1 bands using the Voigt, Speed dependent Voigt and HTP profiles. Line width and shift values are calculated using a semi-empirical approach extended by the use of empirical data to determine some fitting model parameters. The method was further developed by using anharmonic wavefunctions in the estimates of line profile parameters.

Study of the HD16O absorption in the 14,800–15,500 cm−1 range using LED-based Fourier transform spectroscopy

The spectrum of HD16О vapor has been recorded between 14,800 and 15,500 cm−1 by a Fourier transform spectrometer with a spectral resolution of 0.05 cm−1 using a high luminance LED light source and a 60-cm multipath cell with a path length of 3480 cm. A high signal-to-noise ratio (S/N ≈ 10,000) has allowed us to record the lines with intensities of 1.0 × 10−24 to 1.0 × 10−27 cm/molecule. More than 740 lines have been recorded in the spectrum of natural abundance water vapor and over 1210 lines in the spectrum of the vapor enriched with D. 316 rotation-vibration energy levels of the HD16O molecule have been assigned to nine vibrational states. The majority of these energies was attributed to the (014), (600), (142) and (302) states. One hundred two energy levels have been obtained for the first time. The recorded spectra have been compared with the simulations based on the HITRAN-2016 database and variational lists.

Study of Н2О line broadening and shifting by N2 pressure in the 16,600–17,060 cm−1 region using FT-spectrometer with LED source

N2 pressure broadening and shifting coefficients are presented for about 300 strongest water vapor lines in the 16,600–17,060 cm−1 spectral region. The spectra have been recorded with a spectral resolution of 0.05 cm−1 at room temperature by a Fourier transform spectrometer using a high luminance LED light source. A high signal-to-noise ratio (S/N ≈ 10 000) permits the analyses of the lines with intensities from 1.54 × 10−23 to 2.0 × 10−26 cm/molecule. The multi-spectrum fitting procedure was used to fit line parameters of the ν1 + 4ν2 + 2ν3, 3ν1 + 2ν2 + ν3, 4ν1 + ν3, 4ν1 + 2ν2, 5ν1 bands for the temperature T = 297 K. Line broadening and shifting calculations are performed using a semi-empirical method, which is based on the impact theory of broadening, and includes the correction factors whose parameters were determined by fitting the broadening coefficients of 12 lines to the experimental data. The method was further developed for the estimate of line profiles using the an harmonic wave functions.

Study of H216O and H218O absorption in the 16,460–17,200 cm−1 range using LED-based Fourier transform spectroscopy

The spectra of the Н216О and Н218О vapor have been recorded between 16,460 and 17,200 cm−1 by a Fourier transform spectrometer with spectral resolution of 0.05 cm−1 using high luminance LED light source and 60 cm multipath cell with a path length of 3480 cm. A high signal-to-noise ratio (S/N ≈ 5000) enable us to register the lines with intensities of 1.54 × 10−24 to 2.0 × 10−27 cm/molecule. More than 1300 lines were recorded in the spectrum of the natural abundance water vapor and over 1800 lines in the spectrum of the vapor enriched by 18O. 422 rotation-vibration energy levels of the H218O molecule have been assigned to twenty vibrational states. The majority of these energies was attributed to the (241), (321), (340), (420), (401), (500), and (123) states. 43 energy levels were tentatively assigned to the (043), (142), (302), (161), (260), and (062) states. Eleven energy levels were labeled as belonging to the (280), (081), (190), (0 10 0), (1 10 0), (0 11 0), and (0 12 0) states. The recorded spectra were compared with the simulations based on the HITRAN2016 database and variational lists.

Progress in high-luminance LED technology for solid-state lighting

Increasing the luminance of white LEDs to the 200 Mnit level and beyond, opens a completely new design space for a wide range of lighting applications, by allowing significant reductions in optics and luminaire size as well as costs. Moreover, new applications, such as dynamic beam steering, are enabled by the ability to create arrays of densely packed, individually addressable high-luminance emitters. The development of such high-luminance LEDs requires improvements in all LED technology elements. In this paper, we discuss recent advances in epitaxy, die, phosphor, and package technology that are critical to achieving these benefits.

수공냉 대류방식을 이용한 1.2kW급 LED 조명등 개발

As the development of high efficiency and high flux density LEDs, the trend of illumination lamp industry transfers from conventional-lamps to the LED-lamps. For energy efficiencies, LED lamps are superior to the conventional lamps, but they have heat problems. Especially, the heat problems are severe for the high luminance lamps. They degrade the soldering point of the metal PCB, and shorten the life cycle of LEDs. So, the solution of the heat sinking is very important to develop high luminance LED lamps. This study suggested a new method to solve the heat problems for high luminance LED lamps, and developed a LED lamp which has 1200W power. In this study, a water jacket is installed to the LED lamp, and the cooing water is circulated by a water pump.

LED-based Fourier transform spectroscopy of H218O in the 15,000–16,000 cm−1 range

The spectrum of Н218О has been recorded between 15,000 and 16,000cm−1 by a Fourier transform spectrometer with spectral resolutions of 0.03cm−1 and 0.05cm−1 using high luminance LED light sources and a 60-cm multipath cell with a path length of 1920 and 3480cm. A high signal-to-noise ratio (S/N=10,000) enabled us to register more than 1500 water vapor lines with intensities 1.0×10–27 to 2.2×10−24cm/molecule at 296K. 426 rotational-vibrational levels of the H218O molecule were assigned to eleven vibrational states: (014), (033), (052), (113), (132), (151), (212), (231), (311), (330) and (410). 72 Rotational-vibrational levels of the H217O molecule were assigned to six vibrational states: (014), (033), (113), (212), (311) and (410). An extended set of H218O transitions in the 15,000–16,000cm−1 range was generated using the obtained energy level list and the results of a variational intensity calculation.

Highly sensitive Fourier transform spectroscopy with LED sources

It is shown that the use of high luminance LED emitters as a light source for Fourier transform spectrometers permits to enhance their threshold sensitivity in the visible range by orders of magnitude. Using a 2.5W Edixeon EDEI-1LS3 emitter in the range of 11,350−11,700cm−1 as a light source for the spectrometer with a 60-cm multipass cell during a 24-h measurement time, we have achieved a signal-to-noise ratio of 4.5×104 which corresponds to the minimal detectable absorption coefficient of 1.2×10−8cm−1.Such enhanced sensitivity spectrometer has been used to measure the transition frequencies of CO2 vibrational bands 00051−00001 and 01151−01101 in the range of 11,400−11,500cm−1.

Spectral morphological analysis of skin lesions with a polarization multispectral dermoscope

Dermoscopy is the conventional technique used for the clinical inspection of human skin lesions. However, the identification of diagnostically relevant morphologies can become a complex task. We report on the development of a polarization multispectral dermoscope for the in vivo imaging of skin lesions. Linearly polarized illumination at three distinct spectral regions (470, 530 and 625 nm), is performed by high luminance LEDs. Processing of the acquired images, by means of spectral and polarization filtering, produces new contrast images, each one specific for melanin absorption, hemoglobin absorption, and single scattering. Analysis of such images could facilitate the identification of pathological morphologies.

LED 조명 방열 환경에서 진동형 히트파이프의 작동 특성

An efficient cooling system is essential for the electronic packaging such as a high-luminance LED lighting. A special heat transport technology, Pulsating Heat Pipe (PHP), can be applied to the cooling of LED lighting. In this paper, the operational characteristics of the PHP in the imposed thermal boundary conditions of LED lighting were experimentally investigated. The experimental PHP was made of copper tubes of internal diameter of 2.1 mm. The working fluids of ethanol, FC-72, water, acetone and R-123 were chosen for comparison. The results showed that an optimum range of charging ratio exists for high cooling performance; 50% for most of the fluids. Among the five working fluids, water showed the highest heat transfer rate of 260 W. Two distinguished characteristics of pulsating direction were identified. It is also identified that high vapor pressure gradient is one of key parameters for better heat transfer performance.

Heat Dissipation of Sealed LED Light Fixtures Using Pulsating Heat Pipe Technology

An efficient cooling system is an essential part of the electronic packaging such as a high-luminance LED lighting. A special technology, Pulsating Heat Pipe (PHP), can be applied to improve cooling of a sealed, explosion-proof LED light fixture. In this paper, the characteristics of the pulsating heat pipes in the imposed thermal boundary conditions of LED lightings were experimentally investigated and a PHP device that works free of alignment angle was investigated for cooling of explosion-proof LED lights. Five working fluids of ethanol, FC-72, R-123, water, and acetone were chosen for comparison. The experimental pulsating heat pipe was made of copper tubes of internal diameter of 2.1 mm, 26 turns. A variable heat source of electric heater and an array of cooling fins were attached to the pulsating heat pipe. For the alignment of the heating part at bottom, an optimum charging ratio (liquid fluid volume to total volume) was about 50% for most of the fluids and water showed the highest heat transfer performance. For the alignment of the heating part on top, however, only R-123 worked in an un-looped construction. This unique advantage of R-123 is attributed to its high vapor pressure gradient. Applying these findings, a cooling device for an explosion-proof type of LED light rated 30 W was constructed and tested successfully.

칼라 CCD 영상을 이용한 고휘도 LED 전구의 빔 열화 분석

VLC (Visible Light Communication) is a wireless communication method using light that is visible to the human eye. It has a major advantage that it causes no interference to RF-based devices. This makes wireless communication possible in RF hazardous areas such as nuclear facilities. In order to apply VLC communication in harsh environment of nuclear power plant, the high luminance LEDs, which are key components of the VLC communication, have been gamma-ray irradiated at the dose rate of 4kGy/h during 72 hours up to a total dose of 288 kGy. The radiation induced color-center was formed in the LED housing cap made of transparent plastic or acryl material. The beam degradations of high luminance LEDs by high dose-rate gammaray irradiation are analyzed using color CCD image processing technology.

압전 변압기를 이용한 고주파 DC-DC 컨버터 구동에 관한 연구

Recently, as the piezoelectric transformer technology develops, piezoelectric transformer may become a variable alternative to magnetic transformers in various applications. Because it was have to favorable characteristics such as electromagnetic-noise free, compact size, higher efficiency, and superior power density, linkage flux, noiseless, etc. its resonance frequency was used to output waveform of a sine wave. In this paper, the switching mode power supply of about 87.2[KHz] is driven by the multilayer thickness vibration mode piezoelectric transformer and the DC to DC converter drive circuit using an electrical equivalent circuit is proposed. Also, it was possible to drive power source device of the high-luminance LED by propose circuits.

VLC Wireless Data Transmission of High Luminance LED Irradiated by the High Dose-Rate Gamma-Ray

In order to apply VLC (visible light communication) in harsh environment of nuclear power plant in-containment building, the high luminance LEDs, which are key components of the VLC system, have been gamma irradiated at the dose rate of 4 kGy/h during 72 hours up to a total dose of 288 kGy. The radiation induced coloration effect in the high luminance LED bulb made of acryl or plastic material was observed. In the VLC wireless data transmission experiment using the high luminance LEDs irradiated by high dose rate gamma-ray, the radiation induced coloration effect of the high luminance LED bulb extended the communication distance compared to non-irradiated LEDs.

LED backlight system with double‐prism pattern

Abstract— A LED backlight system with a double‐prism pattern for use in mobile phones to achieve thin and high luminance LED backlight systems is proposed. The double‐prism pattern is formed on the light guide of the proposed LED backlight system and simultaneously exhibited two optical functions: shifting of the light from the direction of the guided light toward the radiated light and controlling the directivity of the radiated light. Therefore, using the double‐prism pattern eliminates two prism sheets and a diffusive sheet, which are indispensable optical elements to exhibit the optical function that controls the directivity of light in conventional LED backlight systems. Consequently, the thickness of the proposed LED backlight system is reduced to 0.75 mm compared to that of the conventional system. A luminance of 3115 nits and a full‐width half maximum of 35° for radiated light, which are comparable to conventional LED backlight systems, were obtained.