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DLPLCR65EVM: Use DLPLCR65EVM with NIR pulsed laser

Yuyang Gu
Prodigy 10 points
Part Number: DLPLCR65EVM
Other Parts Discussed in Thread: DLPLCRC900EVM, , DLPLCR65NEVM

Dear Team,

I am trying to use DMD (DLPLCR65EVM with DLPLCRC900EVM controller) with 940 nm pulsed laser (100Hz, 6ns, about 10mJ/cm2 on DMD surface). Based on the DMD power threshold document (DLPA027), I assume it is safe to use this power. However, when I use a 2mJ/cm2 power of 940 nm laser, the DMD surface seems to be damaged (only observable in the off state). So here are my questions:

1. Based on the description, does this mean permanent damage to the micromirrors?

2. If I switch to a NIR version DMD with higher damage threshold, e.g., dlplcr65nevm, will it solve the problem?

  • 0
    TI__Mastermind 45855 points

    Hello Yuyang,

    I need a little bit of clarification about your numbers.  To be clear, the pulsed beam has the following characteristics:

    • 6 ns duration per pulse
    • 100 Hz repetition rate
    • 2 mJ/cm2 per pulse (mJ not nJ)

    Are these values correct?

    I calculate that to be about 333 kW/cm2 during each pulse.

    Is the beam homogenous or Gaussian in profile?

    Fizix

  • 0 in reply to Fizix
    Prodigy 10 points

    Hi Fizix,

    Thank you for your reply! Yes, these values are correct (this is a quite powerful laser from Innolas). I have checked the beam profile, seems homogenous at short range but became fan-shaped at long range. I assume there is a little inhomogenous. Given the short pulse duration of the laser, will it be OK if there is inhomgenuous spot on the DMD?

    Thanks!

    Yuyang

  • 0 in reply to Yuyang Gu
    TI__Mastermind 45855 points

    Hello again Yuyang,

    I cannot say that it will not damage the DMD.  The DLPLCR650NEVM might help some, but be aware that this requires a very different controller EVM. 

    Is the illumination beam expanded onto the entire surface of the DMD or on to a spot?  If it is a spot how big is the spot?  If the beam profile results in hot spots then you could have intensities much higher.

    Are you able to profile the beam at the point where the DMD is?  Even a stray reflection can cause a hotspot that is 4x or more higher in power at a spot than the beam.

    Fizix