What would be the result if we replace the vertical polarizing filter in LCD device (screen) with a horizontal filter, what could we see exactly? Would we see the same if we use only one horizontal filter? Please give me a precise answer.
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$\begingroup$ is it a homework question? $\endgroup$– gigacyanCommented Apr 8, 2015 at 7:56
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$\begingroup$ no it is just a question $\endgroup$– Fawzi BelalCommented Apr 8, 2015 at 13:51
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2 Answers
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The LCD panel consists of elements shown in the figure below. The unpolarized light from backlight panel travels through polarizer, after which the light is linearly polarized. TFT panel controls the voltage on the liquid crystal, voltage applied will cause the liquid crystals to "twist" and thus rotate the polarization of the light. Light then passes the color filter and another polarizer. This polarizer is orthogonal to the first one in normal case, and thus light will pass it. If LC does not rotate the light, it will be blocked by the polarizer.
If the polarizers are parallel, the behavior is reversed, light that has not been rotated by LC will pass the stack and pixel is seen lit, and vice versa.
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We would expect the screen to display bright images as dark (and vice versa) as one of the polarisers has changed 90degs
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3$\begingroup$ It would be much more useful if you explained why we would expect that. $\endgroup$– ACuriousMind ♦Commented Apr 8, 2015 at 10:36