Is there a phase shift associated with twisted nematic LCDs?

  • Thread starter JohnDoes
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Main Question or Discussion Point

Hello,

As it says in the title, I would like to know if the light entering a twisted nematic liquid crystal display experiences any kind of phase shift specifically when applying a voltage to manipulate the polarisation of the light.

If it is the case, could someone point me towards any articles that describe this? I have had a look myself on Google etc., though most of the papers that seem related are only accessible through membership.

Also, if anyone knows the sort of maths behind it e.g. applying x amount of voltage/polarisation induces y amount of phase shift, whether it applies for a specific TN LCD device or in general, that would be great.

Thank you.
 

Answers and Replies

  • #2
K^2
Science Advisor
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Yes. There is almost definitely a shift. Twisting of polarization is equivalent to having difference of refraction index for right-polarized and left-polarized light. (See Faraday Effect for some details.) So I would expect a difference in phase between on and off states. But there might be an overall index of refraction change as well, so I have no idea how you'd go about estimating the total.

I can tell you that people would be looking into this, because there have been applications of liquid crystals in beam steering, where phases are really important. I could probably even point you to people who would know, depending on how important this is.
 
  • #3
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Thank you for the reply K^2. I ask this particular question because it regards a particular design project that I am working on. My project involves finding some programmable "micromirror" device that can create bespoke changes for the phase of light. I happen to have access to a projector that uses a TN device; if it does the stuff I need it to do, with some reverse engineering, it could be just the thing.

If you could point me towards anyone who knows more I'd appreciate it.
 

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