Visible light communication (VLC) is a promising solution to the increasing demands for wireless connectivity. Gallium nitride micro-sized light emitting diodes (micro-LEDs) are strong candidates for VLC due to their high bandwidths. Segmented violet micro-LEDs are reported in this work with electrical-to-optical bandwidths up to 655 MHz. An orthogonal frequency division multiplexing-based VLC system with adaptive bit and energy loading is demonstrated, and a data transmission rate of 11.95 Gb/s is achieved with a violet micro-LED, when the nonlinear distortion of the micro-LED is the dominant noise source of the VLC system. A record 7.91 Gb/s data transmission rate is reported below the forward error correction threshold using a single pixel of the segmented array when all the noise sources of the VLC system are present.

/pdf/towards-10-gb-s-orthogonal-frequency-division-multiplexing-rknocqdbal.pdf

Towards 10 Gb/s orthogonal frequency division multiplexing-based visible light communication using a GaN violet micro-LED

Phosphor-in-glass (PiG) is a mixture of a transparent glass and ceramic phosphors and has been recently commercialized for its various advantages as an inorganic color converter for white light emitting diodes (wLEDs). Since the successful demonstration of the wLED and its improved stability over the conventional phosphors in silicon or organic resins, extensive studies have been reported to improve its color conversion and resultant LED properties, such as luminescence efficacy, chromaticity, correlated color temperature and color gamut, as well as its long term stability. Various attempts have also been made to fabricate a PiG structure and to extend its applications. This study reviews the recent progress of PiG and discusses various approaches that have been proposed to overcome the technical issues related to PiG.

https://iopscience.iop.org/article/10.1149/2.0142001JSS/pdf

Review—A Review on Phosphor in Glass as a High Power LED Color Converter

This paper presents a theoretical framework for incorporating the non-image-forming effects of light into daylighting design in the built environment. The framework includes human performance indicators to measure the magnitude of the non-image-forming effects of light as well as light factors to quantify these effects. In addition, architectural (daylighting) design parameters are included to control the magnitude of the light factors reaching indoor environment. To assess the magnitude of the non-image-forming effects of light in daylighting design process, threshold values for every light factor are discussed. A distinction is made between luminous and temporal characteristics of every light factor and the application of their thresholds in daylighting design process. The proposed framework enables stakeholders in the field of daylighting to incorporate the non-image-forming light requirements in design and to evaluate the potential of indoor spaces with regard to these requirements.

Implementing non-image-forming effects of light in the built environment

A proposed lighting-design space: circadian effect versus visual illuminance

Evaluating and optimising human comfort within the built environment is challenging due to the large number of physiological, psychological and environmental variables that affect occupant comfort preference. Human perception could be helpful to capture these disparate phenomena and interpreting their impact; the challenge is collecting spatially and temporally diverse subjective feedback in a scalable way. This paper presents a methodology to collect intensive longitudinal subjective feedback of comfort-based preference using micro ecological momentary assessments on a smartwatch platform. An experiment with 30 occupants over two weeks produced 4,378 field-based surveys for thermal, noise, and acoustic preference. The occupants and the spaces in which they left feedback were then clustered according to these preference tendencies. These groups were used to create different feature sets with combinations of environmental and physiological variables, for use in a multi-class classification task. These classification models were trained on a feature set that was developed from time-series attributes, environmental and near-body sensors, heart rate, and the historical preferences of both the individual and the comfort group assigned. The most accurate model had multi-class classification F1 micro scores of 64%, 80% and 86% for thermal, light, and noise preference, respectively. The discussion outlines how these models can enhance comfort preference prediction when supplementing data from installed sensors. The approach presented prompts reflection on how the building analysis community evaluates, controls, and designs indoor environments through balancing the measurement of variables with strategically asking for occupant preferences in an intensive longitudinal way.

Humans-as-a-sensor for buildings: Intensive longitudinal indoor comfort models.

Optimization of solid-state lighting spectra is performed to achieve beneficial and tunable circadian effects. First, the minimum spectral circadian action factor (CAF) of 2700 K white light-emitting diodes (LEDs) is studied for applications where biologically active illumination is undesirable. It is found that white-LEDs based on (i) RGB chips, (ii) blue & red chips plus green phosphor, and (iii) blue chip plus green & red phosphors are the corresponding minimum-CAF solutions at color-rendering index (CRI) requirements of 80, 90, and 95, respectively. Second, maximum CAF tunability of LED clusters is studied for dynamic daylighting applications. A dichromatic phosphor-converted blue-centered LED, a dichromatic phosphor-converted green-centered LED, and a monochromatic red LED are grouped to obtain white spectra between 2700 K and 6500 K. A maximum CAF tunability of 3.25 times is achieved with CRI above 90 and luminous efficacy of radiation of 313 - 373 lm/W. We show that our approaches have advantages over previously reported solutions on system simplicity, minimum achievable CAF value, CAF tunability range, and light source efficacy.

Circadian-effect engineering of solid-state lighting spectra for beneficial and tunable lighting

https://ira.lib.polyu.edu.hk/bitstream/10397/78287/1/Cai_Room_Corneal_Illuminance.pdf

The impact of room surface reflectance on corneal illuminance and rule-of-thumb equations for circadian lighting design

Spatial and spectral illumination design for energy-efficient circadian lighting

Spectral optimization simulation of white light is studied to boost maximum attainable luminous efficacy of radiation at high color-rendering index (CRI) and various color temperatures. The photopic eye-sensitivity curve V(λ) is utilized as the dominant portion of white light spectra. Emission spectra of a blue InGaN light-emitting diode (LED) and a red AlInGaP LED are added to the spectrum of V(λ) to match white color coordinates. It is demonstrated that at the condition of color temperature from 2500 K to 6500 K and CRI above 90, such white sources can achieve spectral efficacy of 330–390 lm/W, which is higher than the previously reported theoretical maximum values. We show that this eye-sensitivity-based approach also has advantages on component energy conversion efficiency compared with previously reported optimization solutions.

Spectral optimization simulation of white light based on the photopic eye-sensitivity curve

The invention discloses a medical lighting method and system. The medical lighting method includes the steps: acquiring patterns customized by a user; combining the patterns to form a combined pattern; acquiring a selected control mode; according to the control mode, determining the lighting parameters of the combined pattern, wherein the lighting parameters include a color parameter, a luminance parameter and a change cycle parameter; according to the determined lighting parameters, manufacturing the combined pattern into a video or an image; converting the video or image into the control parameters of LED, wherein the control parameters include the luminescence pattern, the color control parameter, the luminance control parameter and the change cycle control parameter; and according to the control parameters, controlling the lighting state of the LED. The medical lighting method also includes the steps: detecting the physiological characteristic of the user in real time during the using process; according to changes of the physiological characteristic of the user, adjusting the lighting parameters in real time; and performing iterative optimization on the system through adjustment. The medical lighting method and system can utilize lighting to adjust the physiological characteristic, and can indirectly adjust the mood of the user, and has the effect of auxiliary treatment.

Yi Lin

Papers

Circadian-effect engineering of solid-state lighting spectra for beneficial and tunable lighting

The impact of room surface reflectance on corneal illuminance and rule-of-thumb equations for circadian lighting design

Spatial and spectral illumination design for energy-efficient circadian lighting

Spectral optimization simulation of white light based on the photopic eye-sensitivity curve

Medical lighting method and system