• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 30 subscribers
  • Views 1249 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Will using laser illumination source by itself improve contrast?

Kenneth Jorgenson
Prodigy 70 points
Other Parts Discussed in Thread: DLP4710, DLP3010

Hello. I would like to know if using a collimated RGB laser beam as the illuminator for the DMD will by itself improve contrast?

Such a light source won't require the beam to be focused by the projection lens, just diverged.

If not, what can be sued to improve contrast?

Do long vs short throw lens by themselves affect contrast?

And do large aperture vs small aperture lenses by themselves affect contrast?

Taking all of the above into account, how much contrast can we expect realistically from the DLP3010 and DLP4710?

Thank you.

  • 0
    TI__Mastermind 30875 points
    Hi Kenneth,
    Please refer to following application notes these may be able to help you provide some answers.

    www.ti.com/.../dlpa022.pdf
    www.ti.com/.../dlpa044.pdf

    For contrast instead of long vs short throw lens; it will be coming from the optical design itself, especially how much of DMD off-state is captured within the light engine (i.e. not to bring it on the projection path).

    For DLP3010 and DLP4710 it depends on the optical engine manufacturers, look at these spulliers www.ti.com/.../buy-optical-engine.html

    Regards,
    Sanjeev
  • 0 in reply to Sanjeev
    Prodigy 70 points
    Sorry to say but I don't think any of those sources answer the question.
    Lasers have very low etendue and light source diameter (may be considered point source) and very good divergence compared to any other light source. As such, for example, I suspect the projection lenses don't even have to be used to focus the light beam but only set the FOV of the beam and do geometric correction and chromatic aberration correction.
  • 0 in reply to Kenneth Jorgenson
    TI__Mastermind 23090 points
    Hi Kenneth,
    Normally our customers have not used collimated RBG laser beam to illuminate DMD for the following reasons:
    1. It is difficult to create large enough spot to cover complete DMD with overfill (10-15%). The efficiency will be low.
    2. Uniformity could be big issue.
    3. Such system also have higher speckle because angular diversity is less.
    4. Diffraction efficiency could be poor due to a very slow optics (f#).

    The preferred approach is to shape the beam to DMD size and aspect ratio using optics.
    The contrast ratio of the optical system could be improved with slower optics and effective management of stray lights. Our customers have been able to achieve 2000:1 contrast ratio with F/2.4 and up to 4000:1 with F/3.5 optics.

    I hope this answer your questions.

    Regards,
    Vivek
  • 0 in reply to Vivek Thakur
    Prodigy 70 points
    I'm not aware of any laser illuminated DLP projector however there is one using LCoS which is very similar to DLP so no reason why it cannot work. The projector is called UO Smart Beam. I have inspected it personally.

    Thank you. Can you please tell me if this contrast is measured from a projection screen or the beam itself? What I mean is , for example, of the DMD is viewed with an eye piece and not using a projection screen, will the contrast also be in the 1000:1 - 4000:1 range?
  • 0 in reply to Kenneth Jorgenson
    TI__Mastermind 23090 points
    Hi Kenneth,
    Contrast ratio were measured on projection screen. You should see similar performance for Eyepiece. However ,actual measured contrast numbers for Eyepiece may vary depending on f/# of the camera used measurement.

    regards,
    Vivek