Novel fiber-based integrating sphere for luminous flux measurements

2006 ◽  
Vol 77 (6) ◽  
pp. 063102 ◽  
Author(s):  
Martin Szylowski ◽  
Michele Mossman ◽  
David Barclay ◽  
Lorne Whitehead
Keyword(s):  
Luminous Flux ◽  
Integrating Sphere ◽  
Flux Measurements

Luminous-flux measurements by an absolute integrating sphere

1996 ◽  
Vol 35 (22) ◽  
pp. 4385 ◽  
Author(s):  
Maria Luisa Rastello ◽  
Elio Miraldi ◽  
Paolo Pisoni
Keyword(s):  
Luminous Flux ◽  
Integrating Sphere ◽  
Flux Measurements

Multifunctional integrating sphere setup for luminous flux measurements of light emitting diodes

2010 ◽  
Vol 81 (2) ◽  
pp. 023102 ◽  
Author(s):  
Tuomas Poikonen ◽  
Pasi Manninen ◽  
Petri Kärhä ◽  
Erkki Ikonen
Keyword(s):  
Light Emitting Diodes ◽  
Luminous Flux ◽  
Integrating Sphere ◽  
Light Emitting ◽  
Flux Measurements

Convenient integrating sphere scanner for accurate luminous flux measurements

Metrologia ◽  
2009 ◽  
Vol 46 (4) ◽  
pp. S248-S251 ◽  
Author(s):  
S Winter ◽  
M Lindemann ◽  
W Jordan ◽  
U Binder ◽  
M Anokhin
Keyword(s):  
Luminous Flux ◽  
Integrating Sphere ◽  
Flux Measurements

Prognostics Health Management Model for LED Package Failure Under Contaminated Environment

2015 ◽  
Author(s):  
Pradeep Lall ◽  
Hao Zhang ◽  
Lynn Davis
Keyword(s):  
Health Management ◽  
Luminous Flux ◽  
The State ◽  
Remaining Useful Life ◽  
Integrating Sphere ◽  
State Estimator ◽  
Acceptable Error ◽  
Color Shift ◽  
Useful Life ◽  
The Impact

The reliability consideration of LED products includes both luminous flux drop and color shift. Previous research either talks about luminous maintenance or color shift, because luminous flux degradation usually takes very long time to observe. In this paper, the impact of a VOC (volatile organic compound) contaminated luminous flux and color stability are examined. As a result, both luminous degradation and color shift had been recorded in a short time. Test samples are white, phosphor-converted, high-power LED packages. Absolute radiant flux is measured with integrating sphere system to calculate the luminous flux. Luminous flux degradation and color shift distance were plotted versus aging time to show the degradation pattern. A prognostic health management (PHM) method based on the state variables and state estimator have been proposed in this paper. In this PHM framework, unscented kalman filter (UKF) was deployed as the carrier of all states. During the estimation process, third order dynamic transfer function was used to implement the PHM framework. Both of the luminous flux and color shift distance have been used as the state variable with the same PHM framework to exam the robustness of the method. Predicted remaining useful life is calculated at every measurement point to compare with the tested remaining useful life. The result shows that state estimator can be used as the method for the PHM of LED degradation with respect to both luminous flux and color shift distance. The prediction of remaining useful life of LED package, made by the states estimator and data driven approach, falls in the acceptable error-bounds (20%) after a short training of the estimator.

ACCURATE MEASUREMENT OF ULTRAVIOLET LIGHT-EMITTING DIODES

2021 ◽  
Author(s):  
C. Yuqin Zong ◽  
Cameron Miller
Keyword(s):  
Ultraviolet Light ◽  
Light Emitting Diodes ◽  
Luminous Flux ◽  
Junction Temperature ◽  
Integrating Sphere ◽  
Light Emitting ◽  
Type D ◽  
Uv Led ◽  
Uv Leds ◽  
Ultraviolet Light Emitting Diodes

We have developed a new calibration capability for 200 nm to 400 nm ultraviolet light-emitting diodes (UV LEDs) using a Type D gonio-spectroradiometer. The recently-introduced mean differential continuous pulse (M-DCP) method is used to overcome the measurement difficulty associated with the initial forward voltage, VF, anomaly of a UV LED, which makes it impossible to use VF to infer junction temperature, TJ, during pulsed operation. The new measurement facility was validated indirectly by comparing the measured total luminous flux of a white LED with that measured using the NIST’s 2.5 m absolute integrating sphere. The expanded calibration uncertainty for the total radiant flux is approximately 2 % to 3 % (k = 2) depending the wavelength of the UV LED.

LED Lumen Degradation and Remaining Life Under Exposure to Temperature and Humidity

2013 ◽  
Author(s):  
Pradeep Lall ◽  
Hao Zhang
Keyword(s):  
Solid State ◽  
Particle Filter ◽  
Luminous Flux ◽  
Remaining Useful Life ◽  
Integrating Sphere ◽  
Harsh Environment ◽  
Forward Voltage ◽  
Acceptable Error ◽  
Forward Current ◽  
Useful Life

The development of light-emitting diode (LED) technology has resulted in widespread solid state lighting use in consumer and industrial applications. Previous researchers have shown that LEDs from the same manufacturer and operating under same use-condition may have significantly different degradation behavior. Applications of LEDs to safety critical and harsh environment applications necessitate the characterization of failure mechanisms and modes. This paper focuses on a prognostic health management (PHM) method based on the measurement of forward voltage and forward current of bare LED under harsh environment. In this paper experiments have been done on single LEDs subjected to combined temperature-humidity environment of 85°C, 85% relative humidity. Pulse width modulation (PWM) control method has been employed to drive the bare LED in order to reduce the heat effect caused by forward current and high frequency (300Hz). A data acquisition system has been used to measure the peak forward voltage and forward current. Test to failure (luminous flux drops to 70 percent) data has been measured to study the effects of high temperature and humid environment loadings on the bare LEDs. A solid state cooling method with a peltier cooler has been used to control the temperature of the LED in the integrating sphere when taking the measurement of luminous flux. The shift of forward voltage forward current curve and lumen degradation has been recorded to help build the failure model and predict the remaining useful life. Particle filter has been employed to assess the remaining useful life (RUL) of the bare LED. Model predictions of RUL have been correlated with experimental data. Results show that prediction of remaining useful life of LEDs, made by the particle filter model works with acceptable error-bounds. The presented method can be employed to predict the failure of LED caused by thermal and humid stresses.

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