Alignment Question

[Jerry]

Hi all,

I'm am currently selecting a camera and camera lens for my Raman spectroscopy setup. About the camera lens, would a longer focal length or shorter focal length be better? For the camera, I am quite low on budget so I'm planning to buy from Taobao...

The specific model I am looking at is JHEM504UM from JingHang (a Chinese brand) which uses a IMX264 sensor. There is another model JHEM1200UM which uses a IMX226 sensor which is significantly cheaper. I'm not sure why as IMX226 seems to have better resolution. Another model using IMX178 is half the price.

Which one would be better?

[Luc]

Hi Jerry,

You may want to have a look at the articles I wrote on the topic:

https://www.thepulsar.be/article/dynami ... ctrometer/

https://www.thepulsar.be/article/diy-ca ... nch-setup/

https://www.thepulsar.be/article/raman- ... s-upgrade/

[Jerry]

Hi Luc,

Thank you for your advice, I went ahead with the camera and it just got delivered. But even though I could capture the spectrum of fluorescent lamp, I could not capture any Raman spectrum. It's quite strange because with a phone camera placed in front of the diffraction grating, pointing towards the small slit, I could see the orange Raman scattered light (which is quite bright), but there is no Raman spectrum captured. Do you have any suggestions for this?

[Luc]

Hello Jerry,

It's common during the first alignment. Laser steering is usually the problem so check with the frosted disks that you get proper centering on each aperture.

[Jerry]

Hi Luc,

Thank you for your reply. I tried some more times and managed to find the Raman spectrum. I'll be looking to try to improve the quality of the spectrum (it's weak and quite noisy). I have attached the Raman spectrum of a polyethene sample below (I am using the solid cuvette version). Could you help to advise on how to improve the spectrum?

[Luc]

You can try different substrate to check if it's the polyethylene that has lower signal or if alignment can still be improved. Urea is (relatively) safe to handle, cheap, and has a very clean and intense spectrum for instance.

[Jerry]

Hi Luc,

I don't have urea with me now. I tried using styrofoam but no Raman spectrum was captured. Could it be the styrofoam was too fluffy? I used polyethene crystals. Is it important to use powder or crystals?

Also, if I want to improve the alignment, what would you suggest I adjust?