Coherence characteristics of light-emitting diodes

Mehta, Dalip Singh; Saxena, Kanchan; Dubey, Swapnil; Shakher, Chandra

doi:10.1016/j.jlumin.2009.07.027

Cited by 35 publications

(16 citation statements)

References 23 publications

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“…In the past, holographic displays based on partially coherent light sources, such as the light emitting diodes (LEDs), has been reported 20 – 22 . The low temporal coherence of LEDs could reduce the speckle, but the low spatial coherence of LEDs requires additional spatial filter such as pinholes or microscopic objectives to be used to select the emitted light from a local area of an LED in order to increase the spatial coherence and obtain reconstructed images with acceptable sharpness.…”

Section: Introductionmentioning

confidence: 99%

Coherence properties of different light sources and their effect on the image sharpness and speckle of holographic displays

Deng

Chu

2017

Sci Rep

159

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Coherence properties of different light sources and how they affect the image quality of holographic display are investigated. Temporal coherence is related to the intrinsic spectrum bandwidth of the light source, while spatial coherence can be affected by the size of the light source and propagation distance in use. These two coherence properties are measured for various light sources of diode-pumped solid-state (DPSS) laser, laser diode (LD), light emitting diode (LED), super luminescent light emitting diode (sLED) and micro light emitting diode (mLED) in different settings, together with the quality of the holographic reconstructed images. Although the image sharpness and speckle are related to both coherence parameters, our results and subsequent analysis show that the spatial coherence can be linked directly to the image sharpness and the temporal coherence to the speckle. This will provide a quantitative way not only to optimize the image quality between uniformity and sharpness but also to determine the safety power level for different light sources when viewing the produced images by human eyes directly.

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Section: Introductionmentioning

confidence: 99%

Coherence properties of different light sources and their effect on the image sharpness and speckle of holographic displays

Deng

Chu

2017

Sci Rep

159

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“…In recent years, there has been tremendous progress in LED lifetime, illumination efficiency and total lumen output [15]. This new generation high-bright UV-LEDs can be electronically controlled, allowing variable on and off times on a millisecond time-scale.…”

Section: Introductionmentioning

confidence: 99%

Effect of controlled periodic-based illumination on the photonic efficiency of photocatalytic degradation of methyl orange

Tokode

Prabhu

Lawton

et al. 2012

Journal of Catalysis

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The use of controlled periodic illumination with UV LEDs for enhancing photonic efficiency of photocatalytic decomposition processes in water has been investigated using methyl orange as a model compound. The impact of the length of light and dark time periods (TON/TOFF times) on photodegradation and photonic efficiency using a UV LED illuminated photoreactor has been studied. The results have shown an inverse dependency of the photonic efficiency on duty cycle and a very little effect on TON or TOFF time periods, indicating no effect of rate limiting steps through mass diffusion or adsorption/desorption in the reaction. For this reactor, the photonic efficiency under controlled periodic illumination (CPI) matches to that of continuous illumination, for the same average UV light intensities. Furthermore, under CPI conditions, the photonic efficiency is inversely related to the average UV light intensity in the reactor, in the millisecond time regime. This is the first study that has investigated the effect of controlled periodic illumination using UV LED sources. The results not only enhances the understanding of the effect of periodic illumination on photocatalytic processes but also provides a greater insight to the potential of these light sources in photocatalytic reactions.

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“…As we did not use a laser source, but instead applied a LED source that can be considered to be halfway between a perfect laser source and a thermal light [ 72 , 74 , 75 ], we considered the possibility that the Poisson probability distribution did not apply to our experimentation, because of the occurrence of photon bunching [ 76 , 77 ]. In S2 Appendix (Supporting Information), this problem is analyzed and overcome.…”

Section: Methodsmentioning

confidence: 99%

Human Visual System as a Double-Slit Single Photon Interference Sensor: A Comparison between Modellistic and Biophysical Tests

2016

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This paper describes a computational approach to the theoretical problems involved in the Young's single-photon double-slit experiment, focusing on a simulation of this experiment in the absence of measuring devices. Specifically, the human visual system is used in place of a photomultiplier or similar apparatus. Beginning with the assumption that the human eye perceives light in the presence of very few photons, we measure human eye performance as a sensor in a double-slit one-photon-at-a-time experimental setup. To interpret the results, we implement a simulation algorithm and compare its results with those of human subjects under identical experimental conditions. In order to evaluate the perceptive parameters exactly, which vary depending on the light conditions and on the subject’s sensitivity, we first review the existing literature on the biophysics of the human eye in the presence of a dim light source, and then use the known values of the experimental variables to set the parameters of the computational simulation. The results of the simulation and their comparison with the experiment involving human subjects are reported and discussed. It is found that, while the computer simulation indicates that the human eye has the capacity to detect the corpuscular nature of photons under these conditions, this was not observed in practice. The possible reasons for the difference between theoretical prediction and experimental results are discussed.

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Coherence characteristics of light-emitting diodes

Cited by 35 publications

References 23 publications

Coherence properties of different light sources and their effect on the image sharpness and speckle of holographic displays

Coherence properties of different light sources and their effect on the image sharpness and speckle of holographic displays

Effect of controlled periodic-based illumination on the photonic efficiency of photocatalytic degradation of methyl orange

Human Visual System as a Double-Slit Single Photon Interference Sensor: A Comparison between Modellistic and Biophysical Tests

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