5/7/2023 0 Comments Polarized screens for mac t![]() ![]() The display now shows white numbers on a dark background. The outer polarizer has been removed, and replaced after turning it 90 degrees. Shown above is an inexpensive calculator with an LCD display that normally displays dark numbers on a white background. ![]() ![]() Interesting things happen when one changes the orientation of the final polarizer. Rotating the outer polarizer of an LCD causes the display to show negative images (Photo: Gerd Kortemeyer As the level of the voltage is changed, the pixel can let any amount of light pass through, from bright to dark. This light cannot pass through the vertical polarizer P1, so this appears as a dark pixel. In that configuration there is no structure to alter the polarization of the light, so the light leaving the liquid crystal is still horizontally polarized. The voltage causes the liquid crystal's rodlike molecules to line up with the applied field. What happens when there is an applied voltage across the liquid crystal is shown in the right hand of the figure. Finally, the light passes through P1, and appears as a bright pixel. This converts the horizontally polarized light leaving polarizer P2 into vertically polarized light ready to enter vertical polarizer P1. The thickness of the liquid crystal is set so that it rotates the polarization of the light by 90 degrees in the no voltage state. While the pixel can apply a voltage across the liquid crystal through transparent electrodes E1 and E2, on the left the voltage is switched off. The light is polarized horizontally by horizontal polarizer P2, then passes through a liquid crystal LC. Light L is coming up from beneath, usually from a set of LEDs in newer displays or CCFL (Cold Cathode Fluorescent Lamps) in older ones. On the left side of the figure above appears an LCD pixel with no applied voltage. On and off states of an LCD pixel (Image: mschadt) ![]()
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