My situation : The purchased hardware corresponds with the performance edition with solid add-on (2022) with the exception of a Daheng camera (MER2-302-37GM-P). The used camera software is called GalaxyView instead of Spinakker for FLIR cameras. Automatic spectrum extraction was not possible yet but Luc’s Matlab code was already helpful in extracting the paracetamol spectrum. I did not have accessories such as a lens tube, fiber or stage frame at my disposal, so I had to be a little creative and I am very thankful to Luc for his support.
These are my experiences before I retrieved my first spectrum:
- Alignment (1) : The initial mechanical alignment of the lens group I did by elongating the bottom steel bars until they could reach the camera (and later the powder cell fixator). I used the powder-cell-bars for that. Around the camera lens I fixated a card board ‘cage plate’ and two CP33B’s for sturdiness. This way, all lenses were aligned just fine without additional accessories. In case you want to do this as in the Youtube tutorial, I think you’ll need the additional CP36 cage plate, SM1L05 lens tube and SM1A36 adapter.
- Alignment (2) : With the sample holder in place, I was able to manually align the green laser spot in the aluminum cup. However, as it turned out later, the reflected beam didn’t point to the slit. So, I purchased the long rods (ER8-P4), 2 frosted disks (DG10-1500-H1-MD) and 2 threaded cage plates (CP33/M) to align the incoming beam. By putting a simple mirror behind the last disk, I could aim the outgoing beam for the center of the slit.
- Alignment (3) : After removing the disks and installing the solid add-on, I adjusted its tilted mirror (BB1-E02) for centering the laser spot in the sample holder with a frosted disk below it. Again, when you take away the sample holder tray and flush mount a simple mirror below it, the reflected beam can be visibly directed towards the slit to confirm all your tuning as you go (without the edge filter installed of course).
- Alignment (4) : I found out that, even with the bright white paracetamol sample in place, the reflected beam spot was visible on the slit (even for 5 mW). This was a useful confirmation, as the paracetamol’s large variation in Raman intensity made me fly blindly software wise and made me doubt all my mechanical tuning so far. But, as I could visually verify that my alignment was OK, I focused successfully on the powder positioning (@250ms,24dB) and the laser power (30mW).
- Connecting (1) : When I tested the neon lamp with the GalaxyView software, I first had to switch the X-axis direction in the software. This means putting the ImageFormatcontrol\ReverseX parameter to true. In the same ‘ImageFormatControl’ tab, you might also want to change the ‘PixelFormat’ to ‘mono 12’ (i.e. ‘Bpp16’) before you press the camera’s play button. Afterwards, you read the wavelength as the cursor’s X-coordinate in the bottom line of the screen.
- Connecting (2) : The only two other tabs I needed were ‘AcquisitionControl’ (for the ‘ExposureTime’ and ‘AAROIOffset’) and ‘AnalogControl’ (for the ‘Gain’, FYI: max. 24dB).
- Calibrating (1) : Because the solid add-on already contains an achromatic doublet (AC127-019-A), it is sufficient to put the neon or fluor lamp below the powder cell (without sample holder in place). This allowed me to put a light beam on the slit (visible in a dark room). So, a sufficient alignment procedure, with the rotation and rectification of the spectra, occurs completely similar to the bread board instructions without the need for fibers or stage frames.
- Calibrating (2) : I tried an old and fresh fluor compact lamp as described on the webpage but I did not find the demo spectrum. Luc confirmed that it might be due to his lamp’s nature as also other people have found other spectra. Regardless, the pixel trim job can also be done neatly with a cheap white led.
- Calibrating (3) : In absence of the fluor spectrum, the calibration procedure would become something like this :
- Rotate the grating with the bottom knob so that the neon spectrum fills the width of your screen as much as possible (i.e. aim for 2048 pixels).
- In my case, the peak @703nm crossed the right border of the screen and the peak @585nm almost touched the most left border, let’s say its center is at pixel 11.
- Compute the dispersion. In my case (703-585)/(2048-11) = 118/2037= 0.05793 nm/px.
- Determine at which pixel position you need to put the first peak so that pixel ‘0’ is at 540 nm. In my case, 585-540 = 45nm. So, at 45/0.05793 = 776pixels I should put my most left selected peak (i.e. @585nm). This is close to the 779px on the breadboard web page.
(FYI, my @703 peak was far less pronounced than my @692 peak, which is a little odd but especially confusing.)
- You can then use a white LED to adjust the FEL550 edge filter such that you can see it clipping the first few pixels.
