Electronic Displays
Technologies
A CRT fires an electron beam at a phosphor screen, requiring deflection coils, a high-voltage supply of several kilovolts and leaded glass for shielding; phosphor persistence affects smear. LCDs are non-emissive: they modulate light from a backlight using polarisers and liquid crystals, with thin-film transistors forming an active matrix that improves contrast and response. LEDs and OLEDs are emissive; plasma panels use gas cells.
Parameters
Resolution is the pixel count; dot pitch and screen size set pixel density. Brightness is quoted in nits, contrast is the ratio of white to black, and viewing angle, response time and NVIS compatibility matter on a flight deck. Older LCD backlight inverters produce high voltage, dimming may use pulse-width modulation, and aircraft displays are often heated and cooled.
Traps
Confusing brightness with contrast; assuming LCDs emit light; blaming the display unit when the fault is a backlight or inverter; and forgetting that one display can be fed from several sources, so losing a screen is not the same as losing the data.
Worked example
A 6 x 6 inch display with 600 x 600 pixels gives 100 pixels per inch. The same count spread over 8 x 8 inches gives 75 per inch - noticeably coarser. Resolution alone does not make a display readable; brightness and contrast matter as much.