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Throw ratio of DLP Projection-System

George
Intellectual 440 points

Hello,

I bought a DLP LIGHTERCRAFTER. I replace  the LED source with  a laser one. It can project the pattern loaded onto it ,but the image is magnified with distance by the projection-system,as we know.  What's the Throw ration of the Projection-System?

I wish  the image size is fixed and do not change with distance. I am wondering if it could be achieved by adding a lens or a collimation device?

Regards,

Jin

  • 0
    TI__Genius 9935 points

    Jin,

    The throw ratio of the DLP LightCrafter light engine (as supplied) is 1.66. This means the distance to the projected image divided by the width of the projected image = 1.66

    This is in accord with the laws of optics, and is determined by the focal length of the imaging lens.

    If you wish to project an image which does not increase in size with distance, you will need to design special optics. This would be called a 1:1 transfer lens, and is usually designed for a fixed distance. This is very, very different from normal "projection" lenses used for viewing.

    If you need help with design of such a lens, you may contact one of our DLP Design House partners who have expertise in optical design. See http://ti.com/mems "Getting Started" / "DLP Design Houses".

  • 0 in reply to Pascal DLP
    Intellectual 440 points

    Thank you Pascal.

    The throw ratio of DLP LCR is too big for my application. I have tried to disassemble the light engine with the purpose of changing its throw ratio, but  I failed for fear of destroying  its structure.  

    In addition, the lest focus length DLP user's guide specifies (364mm) is  not suitable ，either. Is it possible for me to add a lens outside the projected lens  to change its focus length? In this case, What the throw ratio will be?

    Jin 

  • 0 in reply to George
    TI__Genius 9935 points

    Jin,

    The throw ratio is a function of the effective focal length of the projection optics. However, the proper design of such an optics is non-trivial. I can only refer you to one of our Design House partners (http://ti.com/mems "Getting Started" "DLP Design Houses").

    Yes - you can modify the throw ratio by external lenses. We do not have a recommendation on how to do this. Some experimentation would be in order, but a well specified design would take some work.