How does changes in the twist angle of a twisted nematic display affect its contrast and brightness ratio?

Question

for example instead of a twisted angle of 90degree used in the LCD panel assembly a twist angle of larger or less than 90 was used, how would the brighness and contrast ratio be affected?

Answer 1

you need a twist angle of 90 degrees so that you can have the front and rear polarizers at 90 degrees. If you did not then when you activated the pixel and removed the twist you would still get light coming though both polarizers - if the front polarizer is aligned with the top of the crystal spiral. If it was at 90 degrees to the back polarizer then it would block all the light from an activated pixel, but not let though all the light that got re-polarized by the crystal spiral.


So, if the front polarizer is aligned with the crystal (at an angle =/= 90 degrees to the back polarizer) you get a contrast ratio reduction.

If the front polarizer is at 90 degrees to the back polarizer then you get a brightness reduction