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TIDA-00554: strange peak around 1350nm using a NIR spectrometer

Clotilde Rossignol
Prodigy 10 points
Part Number: TIDA-00554

Hi, 

I want to use a TIDA-00554 spectrometer (NIR spectrometer). But whatever the source I use (black body from 2700K to 4200K), I have some strange peaks around 1300nm in the spectrum.

First I just took the spectrometer and I searched for the spectrum with all the light reflected (a lambertian surface in front of the glass) and I get the following spectra : 

Here we can notice a strange peak around 1350nm. so I tried to normalized this spectrum with the InGaAs spectral response but it didn't change anything.

So I tried to take spectra with other illumination lamps. (known black body in order to compare the results with the expected values) and I get : 

For an halogene lamp with a color temperature of 2700K : 

and for an halogene with a temperature color of 4200K I have : 

So I always have a strange peak around 1350nm and I have no idea why. 

Do you have any idea ? Do I have to normalized the spectrum with other parameters ? 

Thank you very much 

  • 0
    TI__Genius 12575 points

    Hello User,

    Welcome to the E2E forum and thank you for your interest in DLP technology.

    Would you be able to say what firmware (flash) version is on your system? This can be found in the NIRScanNano GUI's Information page.

    Regards,

    Austin

  • 0 in reply to Austin Snyder
    Prodigy 10 points

    I use NIRScanNano GUI's v2.1.0 

    Tiva SW version 1.1.8

    GUI version 2.10

    DLPC Flash version 1.1.0

  • 0 in reply to Clotilde Rossignol
    TI__Mastermind 22830 points

    Hello Clotide,

    You are observing  the effect of lamp's intensity profile over wavelength. For a typical NIR application, you need to use the Absorbance spectrum for analysis, not intensity.

    The lamps light output is not flat across whole wavelength. It also changes with time , temperature and humidly.  It is recommended  to take white point reference  calibration using a 99% NIR reflective standard periodically.

    Please use absorbance plot of sample for analysis. The absorbance plot is calculated using intensity and white reference. The absorbance plot will compensate for  notnflat output from lamp and variability over time.

    Hope this addresses your questions.

    Regards,

    Vivek

  • 0 in reply to Vivek Thakur
    Prodigy 10 points

    Hello Vivek, 

    In my set up, I want to get an absolute measure of the spectrum of a lamp. 

    For this I removed the illumination module and my point is to illuminate the slit with another light source in order to get its spectrum. 

    First, I tried with a halogen lamp because it spectra should be like the black body spectra.  

    So I should have this kind of spectrum : 

    (here for a 2700K black body (intensity as a function of wavelength) (decreasing exponential between 900 and 1700nm) 

    But I have : (second graph : original message)

    When using the illumination module with the two tungsten lamps, I clearly understand that the best is to illuminate a 99% NIR reflective standard periodically. And then to work only with absorbance.

    But here I have no reference. I want to calibrate my spectrometer in order to be able to analyse different light sources. So I need to know the response in intensity of the spectrometer for each wavelength. 

    Do you know why there is a bump at 1350nm ? 

    Can I please have a calibration curve with the response of the spectrometer at each wavelength for different light intensities ? 

    Regards, 

  • 0 in reply to Clotilde Rossignol
    TI__Mastermind 28005 points

    Clotide,

    We will need some time to evaluate and give you a response. The team should be able to get back to you within the next couple of days.

    Regards,

    Philippe

  • +1 in reply to Philippe Dollo
    TI__Mastermind 22830 points

    Hello Clotilde,

    It is very difficult to guess the reason of bump at 1350 nm. Interesting is in the middle of operating range 900nm to 1700nm.

    I understand that you removed the illumination module and directly shining  a light source through the slit.  I do see few potential issues with this approach:

    1. In a normal use case there is collection lens between incoming light and slit. When you illuminate without this optics, there is a high chance of  stray light which could impacts the spectrum result.

    You may want to keep the illumination module and remove the connecting wire to module so that lamp are not ON. Now scan the external lamp source by placing over window. See if this helps. I have never tried this .

    2. Output wavelength form external source - The optics are designed for 900 nm to 1700 nm. If the light source generates any light outside this wavelength  then it will corrupt the result. You may wanto puit a filter between lamp and window to cut wavelength outside the operating range.

    Hope this helps.

    Regards,

    Vivek

  • 0 in reply to Vivek Thakur
    Prodigy 10 points

    Thank you very much. 

  • 0 in reply to Clotilde Rossignol
    TI__Mastermind 28005 points

    Clotilde,

    Not a problem. Let us know if you need additional assistance.

    Best Regards,

    Philippe Dollo