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DLP2010NIR: VIS vs NIR -- Window Material?

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Replies: 4

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Part Number: DLP2010NIR

What precisely is the difference between DLP2010NIR and DLP2010AFQJ? Since the aluminum finish on the micromirrors has a wide reflectance band, is it fair to say that the optical bandwidth of the DLP itself is primarily limited by the window material?

The DLP2010NIR and DLP2010AFQJ datasheets both specify the window material as Corning Eagle XG. If the material is the same, how can they for NIR and VIS applications, respectively? Is the thickness of the window material specified anywhere?

  • Hello Michael,

    I will have to look into this to see what we are able to share. Could you elaborate a little bit more your concerns related to these questions? If I'm not able to provide the exact answer, perhaps I can still address the overall concern.

    Thanks,

    Kyle

  • In reply to Kyle Rakos:

    Hi Kyle,

    The NIR versions of DLP cost roughly 100% more than the equivalent VIS DLP. Other than the fact that a broader band of transmittance above a certain % is guaranteed for the NIR DLP, there otherwise seems to be no material difference between the two, according to the datasheets.

    The NIR datasheet shows a spectral transmittance graph for the window. It would be nice if the charted band was extended further in both (long and short) directions, though. For example, DLP2010NIR has a Figure 18 in Section 6.14 that shows transmittance over 700 to 2500 nm. Throughout that spectrum, nominal is consistently above 95%, and drops to 90% at the far right end, at 2500 nm. Since it's still over 95% at 700 nm, what happens below that? Is it still >90 for most of the visible spectrum? How is it when it reaches UVA? If it's even at 30%, for example, it could still be usable for some applications.

    The VIS datasheet shows no spectral transmittance graph. All it provides in Section 6.12 is a "guaranteed minimum" 97% reflectance between 420 and 680 nm--that doesn't even fully cover the full visible spectrum, let alone into UV/NIR! What's the reflectance at 300 nm? How about in NIR?

    If the optical bandwidth of the DLP is limited by window transmittance, and you're using the exact same window glass for both, then what is limiting bandwidth on the VIS vs. NIR DLP, assuming that's even the case? For example, are there coatings used on the window glass that aren't listed on the datasheet?

    Of course, the reason I am asking this is because there are applications that aren't restricted strictly to the bands listed in the datasheet. If I'm using a NIR DLP to make a spectrometer, for example, and I want to go from 650 to 2500 nm, that leaves 650-700 nm transmittance uncharacterized by the datasheet. Should I assume that since transmittance is still above 95% at 700nm, that it might still be above 80% at 650nm? Should I have to assume that?

    Does TI have extended spectral transmittance available, or provide a comprehensive list of transmittance-limiting materials in the DLP optical path (which I am assuming is only the window)? Otherwise, can TI provide any information on why their NIR DLP is better suited for use in NIR than the VIS DLP?

  • In reply to Michael Barger:

    Michael,

    TI has a published application report, document number DLPA031, Wavelength Transmittance Considerations for DLP DMD Window, which has much or all of the information you need.  Figure 4 shows the transmittance for the different Corning Eagle XG windows from 350-2000nm.

    - Layne

    Layne Jenkins
    Applications Engineer
    Keynote Photonics

     

  • In reply to Layne Jenkins:

    Layne,

    The application report DLPA031 that you recommend is exactly what I was looking for!

    Thank you very much,
    Michael

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