taustavalolähde

A taustavalolähde, translating to "backlight source" in English, is a component responsible for illuminating a display from behind. This illumination is crucial for making the images or text on the screen visible to the user. Historically, cathode ray tube (CRT) displays did not require a separate backlight as the electron beam directly excited phosphors on the screen. However, with the advent of flat-panel display technologies like Liquid Crystal Displays (LCDs), a backlight became a fundamental necessity.

LCDs themselves do not emit light. Instead, they manipulate light passing through them to create images. The liquid crystals, when subjected to an electric field, alter their orientation and thus control the passage of light. The taustavalolähde provides the light that is then modulated by these liquid crystals. Early backlights often utilized Cold Cathode Fluorescent Lamps (CCFLs). These lamps offered a relatively uniform light output but had drawbacks such as a slower warm-up time, a mercury content that posed environmental concerns, and limitations in controlling brightness and color spectrum precisely.

More recently, Light Emitting Diodes (LEDs) have largely replaced CCFLs as the dominant taustavalolähde in LCDs. LED backlights offer several advantages, including lower power consumption, longer lifespan, faster response times, and the ability to achieve thinner display designs. Furthermore, LEDs allow for more sophisticated control over brightness, leading to improved contrast ratios and deeper blacks, particularly with technologies like local dimming. The color of the LED backlight can also be precisely controlled, impacting the overall color reproduction of the display.