LED PWM dimming application for large scale LED video displays is analyzed. The need for short light pulse duration is outlined. PWM dimming with short driving pulses is investigated experimentally. The LED response time skew introduces the nonlinearity for PWM dimming. For LED response time skew estimation, a method is suggested that has been successfully applied to measure some of today’s mar...

Dimming fluorescent lamps is an attractive feature that provides mood and brightness effects as well as having tremendous energy savings potential. Designing a dimmable electronic ballast, however, is a complicated and challenging task. This paper presents an overview for designing a dimming electronic ballast for a T5 35W lamp. Lamp requirements, dimming control methods, and resonant output st...

A sudden depletion or intensity “dimming” of the X-ray corona sometimes accompanies a solar eruptive flare or coronal mass ejection (CME). We have identified a dimming that occurred just prior to a “halo” CME, observed on 1997 April 7 using the Soft X-ray Telescope (SXT) on Yohkoh. Halo CMEs are prime candidates for “space weather” effects. The dimming occurred in compact regions near a flare o...

Variable pulse position modulation (VPPM) is a new modulation scheme that supports simultaneously illumination with dimming control and communication. In this paper, the transmitter, optical wireless channel, and receiver structure of VPPM were modeled mathematically, and their error performance for examining the communication performance according to dimming level and data rate was analyzed. T...

As modem society has been reshaped rapidly into the multimedia information society, large size of display devices is required. Thin-film-transistor liquidcrystal-displays (TFT-LCDs) are one of the most popular display devices from small to large size. TFT-LCDs need backlight source, because they are not a self luminance device. Backlight for LCDs is becoming more important with growth of the LC...

Dimming is an important and necessary feature for light sources used in general lighting applications. An experimental study was conducted to quantify the spectral and luminous efficacy change of high-power colored and pc-white LEDs under continuous current reduction (CCR) and pulse-width modulation (PWM) dimming schemes. For InGaN-based blue, green, and pc-white LEDs, the peak wavelength shift...

LEDs lights have numerous advantages as compared to conventional lighting sources and are becoming popular these days. Depending upon the application requirement brightness of the LEDs needs to be controlled. The brightness is controlled by controlling the forward current flowing through the LED. In this paper, different techniques used for dimming the brightness of LED lamps are reviewed. DC-D...

Carson King 8/2/17 Title: A Comparison of Coronal Dimming Behavior Between XRT and AIA Data Authors: Carson King, Mark Weber, Patricia Jibben A coronal dimming is an event that takes place in the sun’s atmosphere, in which a patch of bright plasma seemingly disappears leaving a dark spot. These events are often associated with other solar phenomena such as flares and coronal mass ejections. Ove...

Defense and security surveillance scenarios typically involve the detection and classification of targets in complex and dynamic backgrounds. Imaging systems deployed for this purpose should therefore provide imagery that enables optimal simultaneous recognition of both targets and their context. Here we investigate the recognition of semi-hidden targets, which are targets that are embedded in ...