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DLP650LNIR: spectral range of the DMD

Gerald
Genius 9575 points
Part Number: DLP650LNIR

Hi Experts,

May I ask for help? Our customer have a concern:

I have a question about the spectral range of the DMD, DLP650LNIR,
its range claims to be in NIR2, 800-2000 [nm] optimized, and the curve is cut in the range of 2000-2500 [nm], is it possible to obtain this efficiency?
It is for educational purposes as we will acquire a DMD with this board and this efficiency is of interest

I hope you can help us. Thank you so much in advcance.

Kind regards,
Gerald

  • +1
    TI__Mastermind 43095 points

    Hello Gerald,

    Are you referring to the Wavelength Transmittance Considerations document [DLPA031E]?  Please understand that this document is a chart of the window only and a single pass.  Using the DMD means that light will experience a pass through the window on the inbound and on the outbound.  I addition, there  will be some reflective and diffractive losses at the active array also.

    Please see table note 13 on page 19 of the DLP650LNIR data sheet [DLPS136].  This note will help to understand how to estimate efficiency based on the optical system you anticipate using.

    Fizix

  • 0 in reply to Fizix
    TI__Genius 9575 points

    Hi Fizix,

    Our customer really appreciate your answer. He said: forgive me but I don't understand the conditions on page 19, they are too many to quantify and I foresee a reflectivity percentage in the range of 2000-2500 [nm],
    Don´t you have an estimate of percentage of effectiveness? It is just to see how much noise it will introduce us into an IR range spectrometer for a Single Pixel system.
    As it was estimated up to 2500 for the NIR1 range, is it possible to reach 2500 using the DLPs for NIR2?

    Kind regards,
    Gerald

  • +1 in reply to Gerald
    TI__Mastermind 43095 points

    Hello Gerald,

    For the NIR2 window we do not have measured data past 2000.  It does drop below 90% shortly past 2000.

    Using the numbers it lists on page 19 for 1064 nm based on the optical system described:

    The specified nominal DMD optical efficiency is based on the following use conditions: (a) NIR illumination (1064nm selected as reference example) (b) Input illumination optical axis oriented at 24° relative to the window normal (c) Projection optical axis oriented at 0° relative to the window normal (d) ƒ / 3 illumination aperture (e) ƒ / 2.4 projection aperture

    The numbers shown are:

    Based on these use conditions, the nominal DMD optical efficiency at 1064 nm results from the following four components: (a) Micromirror array fill factor: nominally 94% (b) Micromirror array diffraction efficiency: nominally 88% (c) Micromirror surface reflectivity: nominally 94% (d) Window transmission: nominally 98% (single pass, through two surface transitions)

    Then the calculation would be: Single pass * Fill Factor * Diffraction Efficiency * Reflectivity * Single Pass.  This would be [ (0.98) * (0.94) * (0.88) * (0.94) * (0.98) ] = ~0.747.  That is an estimate at 1064 nm of about 75%.

    Please note that changing the wavelength, and optics will change this estimation.  It is very dependent on system properties.  As wavelength increases the effective fill factor goes up slightly, but the diffraction efficiency goes down. 

    Fizix