B&W-tech Spectrometer & 473 module: Setup+Mods+Info

[paul1598419]

Re: B&Wtech 473nm unit / Spectrometer Mods & Info

Did you notice the laser has been removed from these new listings? I can't help but wonder how much else is wrong with these.

Also, on your screen shot of the laser spectra, you are overloading the CCD. Don't do that as it can damage it.

 

[jnrpop]

Re: B&Wtech 473nm unit / Spectrometer Mods & Info

Did you notice the laser has been removed from these new listings? I can't help but wonder how much else is wrong with these.

Also, on your screen shot of the laser spectra, you are overloading the CCD. Don't do that as it can damage it.

Thanks Paul, ill try to avoid it. Would you mind sharing how you direct your lasers output into your Spectrometer, your Ocean optics unit and the B&Wtech unit?

Thanks

 

[paul1598419]

Re: B&Wtech 473nm unit / Spectrometer Mods & Info

I use an Ocean Optics nIR, vis, uv fiber to apply light into the spectrometers. It is best to defocus them before inputting, especially higher power lasers. You have to be aware of overloading the CCD. If the peak is broad and cut off at the top, it is overloaded. The fiber optic I use sets the light entering the spectrometer to the correct angle.

 

[jnrpop]

Re: B&Wtech 473nm unit / Spectrometer Mods & Info

I use an Ocean Optics nIR, vis, uv fiber to apply light into the spectrometers. It is best to defocus them before inputting, especially higher power lasers. You have to be aware of overloading the CCD. If the peak is board and cut off at the top, it is overloaded. The fiber optic I use sets the light entering the spectrometer to the correct angle.

Thanks for the info Paul, i tested the 4 fiber cables you sent with the spectrometers and one was a 'stand out' so im using it for further experiments. Like previous posts, the bandwidth is pretty narrow on these B&W units. i cant pick up ~475nm but 495nm registers fine with moscs software, so im assuming the focusing mirror will need to be adjusted, or the grating. Id be happy with 430nm-650nm with 0.1nm accuracy :crackup:, not sure its possible with these units though ,

In the end, ive spent $160usd on these spectro's, and i only have one that operates , staying positive though :beer:

 

[paul1598419]

Re: B&Wtech 473nm unit / Spectrometer Mods & Info

Sorry to hear you are out $160 on these as they weren't all in the best condition. As I recall, the bandwidth is limited to ~200nm on these, so 430nm to 650nm is unlikely to happen. I would suspect that 475nm is not within the bandwidth as that spectro' is set up. I wouldn't start trying a align it unless you have no other way to get it to work. They are not fun to align, so if you don't have to, I wouldn't.

 

[diber]

Re: B&Wtech 473nm unit / Spectrometer Mods & Info

Hello, I am new here on the forum mainly because of these spectrometers and the 473 lasers delivered with them (interested in raman-spectroscopy). I received 5 of these spectrometers from the ebay seller mentioned above. One had a damaged focusing mirror and the pins of the ventilator swapped, rest seem to be OK. Also 4 out of 5 lasers work OK, the 5th losing power after a short while (thermal issue ?). I use these spectrometers with the Spectrum Studio software mentioned above without problems. Perfect for calibration (it has the coefficient fitting included). Did not manage yet to have the coefficients stored in the spectrometer internal memory though.

There are a few peculiarities with the spectrometer however, which can be expected considering their original use. Important and related to the last posts is the fact that there is a cut-off filter at the entrance (and of course the baffles blocking most of the detector, which have to be removed). It blocks most of the light below approx 480 nm (few nm variation in the ones I received). This is understandable considering they were used as a raman/fluorescence sensor, for which you want to block as much as possible the original laser beam. In addition, I have the impression (but might be wrong) that this filter is fluorescing when having 473 nm laser light at the input. Luckily, the filter can easily be removed: open the spectrometer, unscrew the tiny set screw at the spectrometer input (inside the spectrometer) and remove the small black cylinder from the input (again at the inside of the spectrometer). This opens up the spectrum below 480nm (I get typically a range 380nm to 640 nm with some variation from one spectrometer to the other). I have not yet seen higher order spots appearing, but this can be due to my limited testing with this configuration so far.

Spectrometer noise is for all the ones I received between 1300 and 2200 counts, but when acquiring first a baseline dark signal spectrum and substracting it from the other acquisitions (Spectrum Studio can do this on the fly), the remaining noise level is only a few 100 counts and can be further reduced by avering several spectra (also function in Spectrum Studio). On an total signal of more than 60000, this is perfectly fine for me. All of them have however a few "hot" pixels: pixels with either high dark signal (easily removed by background subtraction) or unstable gain (more difficult to remove).

Straylight internally in the spectrometer is an issue with a high intensity input signals. It causes all kinds of strange features in the spectrum.

The beam splitter delivered in the unit is interesting. It has an dichroic mirror inside, reflecting most light close to the 473nm laser wavelength but much less other (higher?) wavelengths. Again: designed for the original application. I could acquire some raman spectra (although still limited quality) of aceton, alcohol etc, just with the delivered laser, the beam splitter and the spectrometer.

Did not try yet to improve the alignment. Not sure if I will do either. Planning however to change the wavelength range of at least one by rotating the grating in order to have a wider spectral range by combining minimum 2 spectrometers.

In summary: I had quite some "fun" with them so far.

 

[paul1598419]

Re: B&Wtech 473nm unit / Spectrometer Mods & Info

Will have to remove that filter when I get time to work with these again. I knew it was there, but didn't know how it attenuated WL around 473nm. Thanks for that.

 

[diber]

Re: B&Wtech 473nm unit / Spectrometer Mods & Info

Further to my previous post, some examples obtained with this spectrometer (initial testing) using the Spectrum Studio software:
- spark emission spectrum of copper wire, one with and one without cutoff filter. The effect of the filter is clearly visible for wavelengths below 485nm (intensity of spark is different for both spectra)
- raman spectrum for acetone
- raman spectrum for isopropanol
The baseline for both raman-spectra is not perfect yet (note that I subtracted a baseline spectra, but it is clearly not perfectm (baseline spectrum to high for isoprop, while too low for acetone setup). Setup for the raman spectra is using the delivered 473nm laser (output power increased by tuning pot on supply as high as possible while still maintaining stable output), delivered fiber optic cables and delivered/unmodified beam splitter.

 

[paul1598419]

Re: B&Wtech 473nm unit / Spectrometer Mods & Info

Hmm. I see what you are talking about. I didn't notice this when I was actively working with these as I was able to see peaks at 477nm on another laser measured on my USB2000. It has been awhile, so I will have to start over at some point. Since I have a good working spectrometer, it hasn't been a pressing issue for me. Thank you for your insights from working with yours.

 

[jnrpop]

Re: B&Wtech 473nm unit / Spectrometer Mods & Info

So i opened up my faulty unit to see how easy the filter is to remove. I attached some photos for you all

One thing, its easier and safer to remove the whole black "filter" frame. Undo the outside 3 screws, then lift the Lid of the Spec unit, using a pair of pliers gently pull the black frame holding the filter unit straight up, it slides upwards.

I havnt ran another test, but it completely makes sense why i couldnt get <475nm, the filter was blocking this part of the spectrum.

Hoping there's no need to re-adjust the focusing mirror after rmoving the filter.

:beer:

 

[paul1598419]

Re: B&Wtech 473nm unit / Spectrometer Mods & Info

That filter looks suspiciously like a lens, Corey. Is that just the way it looks in the photo? Hopefully, everything lines back up once reassembled. I have some concerns about the slit lining up too.

 

[diber]

Re: B&Wtech 473nm unit / Spectrometer Mods & Info

In my spectrometers, this is definitely only a filter and not a lens.

As mentioned, I removed the filter in a different way: after loosening the setscrew which you can see sticking out on the last picture of jnrpop, you can quite easily remove the black cylinder which is then just held in place by the black silicone visible in the last picture. The filter is mounted inside the black cylinder. I agree with jnrpop that is maybe a bit more risky since you are working close to the grating and the mirrors, but there is no risk of changing the alignment. No idea what is best...

 

[paul1598419]

Re: B&Wtech 473nm unit / Spectrometer Mods & Info

Is it even necessary to install the cylinder that held the filter once that is removed? If not, one could just discard the cylinder and put the slit assy back.

 

[jnrpop]

Re: B&Wtech 473nm unit / Spectrometer Mods & Info

I don't think so Paul, it's empty after the filters removed. I believe dibers way is the easiest :beer: all you need to do is unscrew the tiny hex screw on the round cylinder which holds the filter, and the cylinder should break free noting it's also held on by abit of black silicone, not to leave any silicone behind, that might be the hard part. I'll post back when I can confirm it indeed opens up more of the spectrum

 

[paul1598419]

Re: B&Wtech 473nm unit / Spectrometer Mods & Info

I thought that might be what he meant by removing it from behind. That does sound better than pulling the assy off and taking it apart.

 

[Richard A]

Re: B&Wtech 473nm unit / Spectrometer Mods & Info

I haven't had much time to play around with these lately.
I think should examine the lasers a little more now that diber mentioned loosing power on one of them.
Out of the four units I received, one was missing the shield over the ADC. Never found it.
I grabbed the wrong adapter and fried one of them with 12V .
The CCD still works so I just scrapped the PCB and used a microcontroller to drive it.
Only 12 bits of res now.