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Original question:

DLP670S: Wavelength-power density curve

DLP670S: impact of NIR light source (800nm) with this DMD

Paul Dawes
Prodigy 10 points
Part Number: DLP670S

Tool/software:

Hi

we are building a robotics/machine vision system and need a 2K or 4K DMD projector subsystem.

Our light source needs to be in the NIR range (~800nm) which is just outside the spec for the DLP670.  TI NIR-rated DMDs don't support a high enough resolution (e.g. WXVGA)

Can you tell me how much impact an 800nm light source will have on the DLP670s?

The transmission curves (https://www.ti.com/lit/an/dlpa031e/dlpa031e.pdf?ts=1741136724359&ref_url=https%253A%252F%252Fe2e.ti.com%252F)_ seem to show about 90% transmission at 800nm, but the spec sheet shows a huge drop in power capability (from 30 W/cm2 to 10mW/cm2).  

In another thread your engineer states that this '10 mW/cm2 number) is untested and for 'historical' reasons to prevent out of spec usage.

So... am I goign to burn the unit up if we run it with an 800nm light source?

thanks

paul

  • 0
    TI__Guru 54285 points

    Hello Paul,

    You did not mention how much power you intend to put on the DMD.  I assume it will be greater than the 10mW/cm^2.

    The next thing to consider is that the mirrors are basically aluminum.  At 830nm the reflectivity of aluminum takes a significant dip to about 85%.  It is already affected at 800nm and is about 87%.  This means that the absorbed light becomes heat.

    Fizix

  • 0 in reply to Fizix
    Prodigy 10 points

    Thanks for the response! Not sure how much power we will be applying but I think its safe to say its more than10s of mW/cm2...

    It sounds like using one of the visible light DMDs with NIR (even at 800nm) is going to be problematic.

    Do you know of any higher resolution DMDs (eg 1080p) that would support NIR light sources?

    thanks

    paul

  • 0 in reply to Paul Dawes
    TI__Guru 54285 points

    Hello Paul,

    Technically it will be outside of the data sheet specifications, so no warranty. 

    That said, if the total is less than 1W/cm^2 you should be OK.  Still, you should at least provide at least a small heatsink.  Some chip coolers may be small enough in footprint.

    Fizix