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Telecentric DLP without TIR prism

Brian58581
Intellectual 270 points

I have been looking at DLPs for a while now for a custom projection system, and the 6500 EVM probably would suit my needs well.


The issue is getting a hold of a TIR prism. 


Thinking about it simplistically, I don't see why I need to use a prism at all to have a telecentric design.


Considering figure 4:

http://www.ti.com/lit/an/dlpa022/dlpa022.pdf

Is there a reason not to simply fold the light path with mirrors to bring the optical refection from the DMD to the vertical axis?


Have I missed an obvious disadvantage? (Other than size which is not critical to me).

  • 0
    TI__Guru 54390 points

    Hello Brian,

    You have correctly understood the primary advantage which is reduced size of the system and optical elements in a projection system.

    There is one aspect of size advantage that may not be obvious.  If you wish to maintain F3.0 or faster optics, then by spacing things out so that your optical elements don't interfere, you will need larger optical elements. 

    I hope this helps.

    Fizix

  • 0 in reply to Fizix
    Intellectual 270 points

    Thanks for the prompt and helpful answer!

    If I read the application note correctly the light at the DMD is just colimated? It seems like under ideal conditions the lens distance would not matter at all in that case? Is the light not just some uniform colimated circle? ("chief rays essentially parallel").

    I realize that longer f means bigger D for equal f number. But I am having trouble understanding why the focal length matters here if I am just building a collimator and then folding it to hit the mirror at the correct angle.