IR Spectrometer Project: Is This Project Within My Reach?

[poormystic]

Hi Everyone
I'm considering a project, and wondering whether you think my approach would work.
(I also have to consider expense.)

I think that I can make a diffraction grating suitable for mid infrared spectroscopy. I'm thinking of the range between 2.5 microns wavelength and 7 microns. The people who work with this stuff usually talk about "wavenumbers" instead of wavelengths - the range can also be expressed as between 4000 and 1500 per centimeter. (Obviously a European standard

If I can really make a diffraction grating, the hardest part of the work remaining is the sensor.
The sensor, in my design, would need to read a slit of infrared light only hundreds of nanometers wide.
It mightn't need much of a linear response - the presence/absence of certain wavenumbers signals the existence/non-existence of certain kinds of bonds.

So, it looks like I would need a very sensitive infrared sensor.

I haven't any particular use for this btw. It's just that I'm nearing the end of my diffraction grating making project, and I'm wondering what to do with gratings.

Anyway...

Merry Extremely Happy Years End To All!

​

 

[danadak]

Take a look at Melexis for IR sensors, might be a possibility there.

Temperature sensor ICs

We offer a broad range of contactless solutions with our single point infrared thermometers and infrared sensor arrays.

www.melexis.com

 

[bertus]

Hello,

Have a look at the following pages about ir ranges:

Understanding Infrared Spectrum Frequencies - NLIR

Explore the fundamentals of infrared spectrum frequencies, from near to mid and far-infrared regions. Learn how NLIR powers real-time MIR analysis!

nlir.com

https://www.sciencedirect.com/topics/physics-and-astronomy/infrared-spectrum

Wich specific range are you looking for?
What do you want to measure?

Bertus

 

[poormystic]

Hi @bertus
The near infrared would be easiest.
Physics suggests that the longer the wavelength, the more noise - I don't have much of a clue when this starts to matter with modern components.
That's the kind of question that lurks behind my ear and makes me wonder.
Thanks

 

[bertus]

Hello,

What kind of spectrometer do you want to make?
There are absorbtion and reflection types.

Bertus

 

[poormystic]

mmm, well
It turns out that the really quite far infrared is very interesting. Deep infrared that shines through a solution can be spectrographically analysed, and the results fed to a "fingerprint recognition engine", please. Tables of the fingerprints of millions of molecules are available online.
Fingerprint analysis in a portable machine is desired by festival drug testing services.
I did not say that I would build such a machine... I really do wonder if this is within home workshop capabilities.

Still, as for absorption/reflection, I choose absorption, for organic solutions.

 

[Delta Prime]

Your thread title:”

IR Spectrometer Project: Is This Project Within My Reach?”​

No.

Quantum Physics Forum

Join in expert discussion on quantum physics. Quantum physics is the mathematical description of the motion and interaction of subatomic particles. Quantum Mechanics and Field Theory.

www.physicsforums.com

I’ll see you there…

 

[poormystic]

Thanks for that opinion @Deltaprime.
I was coming to the same conclusion, in the matter of the far i.r. stuff.
Near i.r. - just a bit longer than the wavelengths of visible light - is a lot more accessible because there's no need for a vacuum, and no need for ultra-cooled thermistor detectors. Et cetera.
Even for near i.r., a lot of work.

Rather than starting out in quantum physics I think I'll concentrate on finishing my diffraction grating making machine. Lest I make unwitting contributions to somebody's comedy thread

Mark

 

[Delta Prime]

I'm wondering what to do with gratings.

I think I'll concentrate on finishing my diffraction grating making machine

I haven't any particular use for this btw.

Marshall your thoughts occurring suddenly in your mind & we can help.

Electrical Engineering Forum

Join the expert discussion on electrical engineering topics. Topics like the uses of electricity and the equipment for power generation. Circuits, Fiber, Signals and Systems, Semiconductor Devices...

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[rvatassery]

Interesting project, here's my 2c, even on a thread that's potentially settled.

The IR region you're looking for is best to be detected by MCT-A (HgCdTe detector) and these need to be cooled with N2(l). They're also not super cheap. There are other detectors which can be used which operate at STP, but they're less accurate. The issue, as you might already know, is that IR frequencies match thermal vibrations and those thermal vibrations at STP will overwhelm a sensitive detector. Thus the N2 cooling.

I think a basic flow of an IR detector, for anyone who is looking to dig into this further, is to sent the IR light through a beam splitter. Half goes to sample, half to the reference. After interacting with the sample, the sample beam interacts with the reference beam in an interferometer (leaving this intentionally vague, as I am unsure of the exact details). The output of the interferometer is then sent to a Fourier transform and the result is what you reference as being plotted in terms of cm-1 (reciprocal cm, or wavenumbers).

 

[poormystic]

Thanks
Yes that's one way to do it - by using a Michelson interferometer.
Because I am prejudiced against common sense, and because I like to test myself all the time to see if my insights are real, I had been considering another way to do the detection.
I think your insights are real enough @rvatassery, and thanks for your "2c".

However time moves quickly - I've been seconded to teach an autistic child maths, which will do me for an impossible project for a while.
This project can wait until next life if need be.

 

[ahsrabrifat]

A home-made grating can work in mid-infrared. You do not need nanometer-scale slits for spectral resolution. Resolution depends on illuminated grooves and optical geometry. The main difficulty is obtaining a suitable mid-infrared detector.

 

[olivia_49]

That sounds like an awesome project! The grating part seems doable, but the sensor will be tricky, you’d need something really sensitive like a thermopile, MCT, or pyroelectric detector. Even just detecting the presence or absence of certain wavenumbers could give you interesting results, and it’s a great way to explore IR spectroscopy.

Hi Everyone
I'm considering a project, and wondering whether you think my approach would work.
(I also have to consider expense.)

I think that I can make a diffraction grating suitable for mid infrared spectroscopy. I'm thinking of the range between 2.5 microns wavelength and 7 microns. The people who work with this stuff usually talk about "wavenumbers" instead of wavelengths - the range can also be expressed as between 4000 and 1500 per centimeter. (Obviously a European standard

If I can really make a diffraction grating, the hardest part of the work remaining is the sensor.
The sensor, in my design, would need to read a slit of infrared light only hundreds of nanometers wide.
It mightn't need much of a linear response - the presence/absence of certain wavenumbers signals the existence/non-existence of certain kinds of bonds.

So, it looks like I would need a very sensitive infrared sensor.

I haven't any particular use for this btw. It's just that I'm nearing the end of my diffraction grating making project, and I'm wondering what to do with gratings.

Anyway...

Merry Extremely Happy Years End To All!

​

 

[poormystic]

Thanks @olivia_49
I've been through a bit of a cooling-off with my machine design - but maybe I'm warming up again. Perseverance is often a virtue - don't I like being virtuous?
The diffraction grating making machine (DFGM) isn't finished yet - there's still maybe a grand or $1500 to spend, and I haven't been very sure of making a profit. (Also it's been Christmas and dealing with a.h. family members always knocks me back a bit!)
I'll return to this "add-on" project - the infrared spectrometer - once the main machine gets running... surely not more than 3 months? I've put nearly 2 years into it so far.

Where I'm at
The DFGM started out in my mind as a purely mechanical design, but I saw that its output would be too, too slow. I kept thinking about it pretty obsessively until I got a design I much preferred, and started to build it.
However before I got far I had a better idea, and then a better one still, and the process of having new ideas before I could deal with the old ones continued for a long time. Yet I could tell I was making progress, because my designs kept getting simpler.
I eventually settled on a piezoelectric technology to make gratings electromechanically. The work of designing an acceptably cheap, mechanically adequate carriage for the piezoelectric actuators (PZT's) took quite some time - I haven't had much experience with mechanical engineering.
The machine I have designed uses very few parts, because the needs of modern electronics are nearly all catered for in the catalogues of RS, Mouser, and lots of other little suppliers and manufacturers.
I'm a bit shy about saying exactly how it all works because I expect to make money out of this... I'm close enough now to letting out my own commercial secret.
So why am I telling you about it at all?
My intention, in letting others know about this dream I'm on the verge of fulfilling, is to encourage those who visit this forum looking for something to take up for themselves... to give themselves some hope. This project has helped me lots.
I'm an old pensioner without family living in a foreign land, and my friends have mostly passed away. Yet I can dream! This project has been a dream to carry me through 2 years, and is a dream which will be realised soon.
Regardless of the eventual outcome, the work of trying to accomplish this project has been much better than having no direction in life.

 

[Delta Prime]

Jesus Christ brother, personal message me…my superiors have already read our discussions on this site and I’ve asked them if I’m authorize to help you on my own time and use the laboratory equipment to assist you! The answer is yes…
I say this only because you’re a respected fellow member of this community
Regards-Delta Prime