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Spectroscopy using DLP technology

Trane
Intellectual 435 points

Thefollowing link …

http://focus.ti.com/analog/docs/memsmidlevel.tsp?sectionId=622&tabId=2454

… makes reference to spectroscopy using DLP technology.

Is there any details of how this works and the level of performance (ie resolution and speed) which can be expected?

 

Thankful for reply!

  • 0
    TI__Guru 54705 points

    Hello Trane,

    The resolution of a such a spectroscopic solution is very dependent on the level of dispersion provided by the grating chosen for the application.  The tradeoff is between resolution and how much of the spectrum you can cover.  If we consider an XGA for example then there can be as many as 1024 divisions of the spectral region covering the DMD.

    The switching speeds of various DMDs vary, but using the XGA with a D4100 chipset can potentially realize about 32,000 binary patterns per second.  The limiting factor is usually the speed of the detector used in conjuction with the system.

    I hope this helps.

    Fizix.

  • 0 in reply to Fizix
    Prodigy 20 points

    Hello Fizix,

    My understanding is that a DMD can be used to create a programmable optical filter to selectively reflect a particular range of light.  Is that correct?  If so, I am looking for an explanation of the "theory of operation" behind such a use.  In other words, how can a DMD be controlled to perform optical filtering and why does it work?    Can you possibly provide such an explanation or point me to one?

    Thanks in advance,

    Chester

     

  • 0 in reply to Chester Boltax
    TI__Genius 9935 points

    Chester,

    I told Fizix that I would try to answer your question.

    The DMD is an array of mirrors. So - how can it filter different wavelengths of light? Ah! The light has to be dispersed into different wavelengths BEFORE it strikes the DMD. This task is usually accomplished by a diffraction grating, though it could be a prism.

    After being dispersed by the diffraction grating, the different wavelengths of light (different colors of the rainbow, if you will) are spread out across the DMD's array of mirrors, with different regions of the DMD illuminated by different wavelengths. Then, using the ability to set patterns of mirrors on the DMD, only the mirrors corresponding to the desired wavelengths are activated (set, or turned on) to reflect just that wavelength into the collection optics where it is measured, or otherwise used. Of course, since any pattern of mirrors can be set, multiple wavelengths can be selected (and selectively attenuated) simultaneously - if desired.

    Perhaps this is enough to give you an insight into the "theory of operation" of a DMD as a wavelength selective filter.

    Best regards,

    Pascal

     

  • 0 in reply to Pascal DLP
    Prodigy 20 points

    Perfect!  Thank you, Pascal.

    -- Chester