Analysis on the Luminous Efficiency of Phosphor-Conversion White Light-Emitting Diode

Due to the difficulty in measuring very low out-of-band cutoff depths of solar blind UV filters, we propose a cutoff depth adjustable measurement system (CDAM) to test deep cutoff filters with a large dynamic range. The CDAM utilizing the substitution method is elaborately composed of several parts, including narrow-band LED light sources, standard reflective neutral attenuators with known attenuation coefficients, and a photomultiplier (PMT). This paper also presents an attenuator combination method ensuring that the PMT works within its linear response range. In addition, numerical simulation testifies to the method, and experiment shows that the CDAM system can achieve an extension of dynamic range from 0-6 OD to 0-10 OD, which is sufficient for the measurement of out-of-band cutoff depths of solar blind UV filters. Above all, the CDAM system, being easily implemented, of wide dynamic range, and highly precise, could be widely used in the measurement of filter cutoff depth.

Section: Introductionmentioning

confidence: 99%

Out-of-Band Measurement of LED-based Solar Blind UV Filters

Muhan¹,

Zhou²,

Xue³

et al. 2014

“…The temperature dependence of the WPE of the blue LED and that of PCE are determined separately from spectral analyses, which are used to explain the temperature dependence of LE in the white LED. It is not easy to evaluate the absolute value of PCE for the phosphor material in the white LED [6]; nevertheless, it will be shown that the relative change of PCE with temperature can be obtained through the analysis of the LED's efficiency and spectrum.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the Temperature Dependence of Phosphor Conversion Efficiency in White Light-Emitting Diodes

Ryu

2015

Self Cite

We investigate the temperature dependence of the phosphor conversion efficiency (PCE) of the phosphor material used in a white light-emitting diode (LED) consisting of a blue LED chip and yellow phosphor. The temperature dependence of the wall-plug efficiency (WPE) of the blue LED chip and the PCE of phosphor are separately determined by analyzing the measured spectrum of the white LED sample. As the ambient temperature increases from 20 to 80 o C, WPE and PCE decrease by about 4.5% and 6%, respectively, which means that the contribution of the phosphor to the thermal characteristics of white LEDs can be more important than that of the blue LED chip. When PCE is decomposed into the Stokes-shift efficiency and the phosphor quantum efficiency (QE), it is found that the Stokes-shift efficiency is only weakly dependent on temperature, while the QE decreases rapidly with temperature. From 20 to 80 o C the phosphor QE decreases by about 7% while the Stokes-shift efficiency changes by less than 1%.

“…The CRI value of the high power white LEDs has been increased due to development of phosphors that convert the blue LED lights into white light. [2,3] Besides the high CRI values, high illuminance is also required in the dental astral lamp. More specifically, the dental astral lamps require 10,000 lx for diagnosis and 2~40,000 lx for dental surgery.…”

Section: Introductionmentioning

confidence: 99%

Optical Design of Multimedia-Embedded LED Dental Astral Lighting using the Reverse Dual Reflector Method

Kwon¹,

Hwang²,

Jun³

et al. 2015

Light-emitting diodes (LED) have many advantages for dental astral lighting because of their high color rendering index (CRI), low power consumption, light weight and longer life. A dental astral lamp is specially designed and simulated for securing the extra space for installing a multimedia display that will be helpful for treating young patients. The optical system using the reverse dual reflection method consisted of four illumination modules disposed at the four corners of the dental astral lamp, and each module comprises a high power LED, an elliptical mirror, and a multifacet reflector assembly using eight cylindrical mirrors. It is shown that the required illuminance, illumination pattern, and the illumination uniformity are well satisfied.