Avionic Displays are widely used in cockpits of all fixed wing aircraft and helicopters and show a steadily technology improvement over the years. The current avionic displays are using Liquid Crystal Displays (LCD) with LED Backlight assemblies. The benefits for the existing LED backlighting over previous solutions are well known: lower power consumption and more flat display systems resulting in size and weight reduction. The quality of the cockpit display unit is highly determined by the quality of the backlight unit.
In order to overcome the disadvantages of RGB and white LED solutions, the DERPHOSA consortium will develop technology for an avionics displays with a new advanced backlight concept, based on Colour Conversion by Remote Phosphor.
The objective of this project is to achieve substantial benefits on system simplicity, improving quality, reliability, power efficiency and reduction of supplier dependence and cost for development and maintenance/operations over lifetime.
The proposed Advanced Remote Phosphor Backlight concept is an evolution of the current LED backlights based on RGB or white LEDs. By using a blue pump light source (LED) and a dedicated external fluorescent phosphor layer (remote phosphor) the blue light will be converted to a very stable customized white light.
The main scientific objective of the project will be the adaptation of the fluorescent phosphors to the wavelength of the blue pump light source, and the tuning of the fluorescent phosphors to the colour filter of the LCD, together with the total optical behaviour over lifetime.
The project will evaluate and realize the remote phosphor backlight concept for both direct lit and edge lit application. To evaluate the feasibility, advantages and drawbacks of remote phosphor for each application, two test set-ups will be realised, which will be integrated in existing Display Units (hardware/ software).
Remote phosphor debuts in avionics displays
Light-emitting diode (LED) lighting technology continues to make inroads across all areas of aircraft lighting, meeting the aircraft industry's critical demands for low-power, small-size and high-reliability light sources. EU-funded researchers developed new technology that promises to improve LED light quality and distribution in cockpit displays even in bright sunlight.
Current avionics displays use liquid crystal display (LCD) technology that mainly consists of two parts: a liquid crystal glass and a backlight (LED) creating all the necessary light. However, nearly every LCD display suffers from uniformity issues.
With EU funding of http://derphosa.nlr.nl/ (DERPHOSA) (Technology development of remote phosphor for avionic cockpit displays), four European companies joined forces to develop a new backlight concept based on remote phosphor, offering a simpler solution with a more stable colour yield.
The advanced remote phosphor backlight concept is an evolution of the current triple-colour or white LED backlights. A blue LED illuminates a layer of fluorescent phosphor, converting the blue wavelength to very stable, customised white light. The phosphor is layered onto a substrate separate from the LED chip. Reaction losses between phosphors and the LED chip are thus minimised, leading to higher light output and improved colour performance.
By eliminating the use of multiple light sources and complex electronics and control software to correct for colour differences, this technology significantly simplifies the LCD backlight unit. It also offers high reliability and reduced maintenance costs.
Project efforts were mainly devoted to adapting the fluorescent phosphors to the wavelength of the blue pump light source and tuning them to the LCD colour filter.
Researchers implemented the remote phosphor backlight concept for both direct-lit and edge-lit applications. The new displays scored well during validation testing at an altitude of 10 km and with bright sunlight, offering better contrast and greater clarity than the current displays.
In addition to better image quality, the innovative DERPHOSA solution combines higher energy efficiency and lower weight compared to the current triple-colour or white LED backlights. Project results were disseminated through the project website, at conferences and in newsletters. You can view the http://www.youtube.com/watch?v=j2O3sROXRQk&feature=youtu.be (project video here).