A performance comparison of backlights containing a tubular serpentine fluorescent lamp (TSFL), a flat fluorescent lamp (FFL), and an array of LEDs as light sources is presented. Factors such as efficacy, color rendering capability, temperature dependence and dimmability are discussed. Additionally, key parameters considered include the mechanical configuration and overall depth of the backlight system (including filters/diffusers); shock and vibration susceptibility; manufacturing complexity; and optical performance, such as luminance and uniformity.
When considering the operating conditions of an aerospace flight deck, avionics displays have extremely stringent requirements. To comply with this environment, LCD Lighting, Inc. has recently introduced new fluorescent lamp technology that improves the overall performance of AMLCD backlights. This advancement, called Ultra-BrightTM, permits AMLCDs to consistently meet the demanding standards of the avionics display industry. In this paper, we will review fluorescent lamp construction, operating principles and physics, and then describe our recent innovation that has notably enhanced fluorescent lamp performance.
Active Matrix Liquid Crystal Displays (AMLCDs) used in avionics applications require high luminance, high efficacy, and long-life backlights. Currently, fluorescent lamps are the favored light sources for these high performance avionics backlights. Their spectral characteristics and high electrical efficiency are well suited to illuminating AMLCDs used in avionics applications. Fluorescent lamps, however, suffer gradual reduction in luminance output caused by various degradation mechanisms. Korry Electronics Co. recently developed a mathematical model for predicting fluorescent lamp life. The model's basis is the well characterized exponential decay of the phosphor output. The primary luminance degradation mechanism of a fluorescent lamp is related to the arc discharge. Consequently, phosphor depreciation is proportional to the discharge arc power divided by the phosphor surface area. This 'wall loading' is a parameter in the computer model developed to extrapolate long-term luminance performance. Our model predicts a rapidly increasing decay rate of the lamp output as the input power is increased to sustain constant luminance. Eventually, a run-away condition occurs -- lamp arc power must be increased by unrealistically large factors (greater than 5x) to maintain the required luminance output. This condition represents the end of the useful lamp life. The lamp life model requires the definition of several key parameters in order to accurately predict the useful lamp life of an avionics backlight. These important factors include the construction of the lamp, lamp arc power, a decay constant based on the phosphor loading, and the operational profile. Based on the above-mentioned factors, our model approximates the useful lamp life of an avionics backlight using fluorescent lamp technology. Comparisons between calculated and experimental lamp depreciation are presented.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.