16 August 2001 LED flicker pulsing
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There is need to replace hazardous radioluminescent light sources with a means of illumination that is environmentally friendly. This paper describes an electronic source that was developed as a potential candidate to replace low intensity tritium in a military system. It employs an LED for illumination and a 3-volt coin cell battery as a power source. This new light source is electronically invisible, requires minimal maintenance, and provides the lowest practical illumination to preclude detection by optical means. The low intensity requires that the LED be driven at DC current levels resulting in poor luminous efficiency. Therefore, in an effort to maximize battery life, the LED is pulsed into a more optically efficient mode of operation. However, conventional pulsing techniques are not employed because of concerns the electronics could be identified by conspicuous power spectral density (PSD) components in the electromagnetic spectrum generated by a pulsed LED. Therefore, flicker noise concepts have been employed to efficiently drive the LED while generating a virtually undetectable spectral signature. Although ideally the pulse durations, magnitudes, and spacings should be random, a significant reduction in conspicuous PSD components can be achieved when imposing practical constraints. The dominant components of the power spectrum are significantly reduced using fixed pulse durations and magnitudes while varying only the pulse spacing. The mean duty cycle is set to provide the same effective illumination as DC operation while generating a PSD normally associated with natural phenomena.
© (2001) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Mark A. Johnson, Mark A. Johnson, Paul J. Cote, Paul J. Cote, } "LED flicker pulsing", Proc. SPIE 4380, Signal Processing, Sensor Fusion, and Target Recognition X, (16 August 2001); doi: 10.1117/12.436984; https://doi.org/10.1117/12.436984

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