Based on Public Lab's Spectrometer 3.0
Python scripts to select, average, and calibrate spectrum data from USB spectrometer. Plotting with Gnuplot. Running on Raspberry Pi.
- Camera, diffraction grating, slit, mounted on magnets and arranged on a metal sheet:
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| Enlarger head with condensing lens and iris to focus light on the diffraction grating |
- Camera should be focused on the collimation slit, approximately 200mm away.
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| Camera with Focusing Aid |
- Over exposure will clip the image and make it difficult to find peaks
- Reduce camera brightness to get a solid black background
$ ./spectrometer/average -h
usage: average [-h] [-x WIDTH] [-y HEIGHT] [-v VIDEODEV] [-a AVERAGEITEMS] [-c PIXELCLIP]
Spectrometer
options:
-h, --help show this help message and exit
-x WIDTH, --width WIDTH
-y HEIGHT, --height HEIGHT
-v VIDEODEV, --video VIDEODEV
-a AVERAGEITEMS, --average AVERAGEITEMS
-c PIXELCLIP, --clip PIXELCLIP
File located at: ./spectrometer/config.ini. Commented entries indicate default values:
| File | Description |
|---|---|
| [Spectrometer] | section header |
| #width=1280 | image width |
| #height=720 | image height |
| #videoDev=/dev/video0 | USB camera device |
| #averageItems=20 | number of frames to average |
| #pixelClip=250 | Out Of Range warning level |
| #calibDefault=',,410,900' | default calibration settings, HG463 and EU611 |
Select a line through the camera spectrum image:
Click AVERAGE, and wait a few moments for the image to settle down. If the value of a pixel exceeds the Out Of Range warning level, a red mark will appear at the top of the column.
Click on prefix to set the file name prefix (e.g. 'cfl'). Click on decription to set the description (e.g. 'CFL 2700K'). Click SAVE.
Output is a JPG of the resulting average, and a CSV with the average of each pixel and the averages of each color.
$ ./spectrometer/calibrate -h
usage: calibrate [-h] CSVfile
Calibrate
positional arguments:
CSVfile
options:
-h, --help show this help message and exit
Calibration uses landmarks to calibrate the output:
- calibrate to landmarks in the spectrum (CFL Calibration)
- calibrate to landmarks in the camera response (CIS Calibration)
| Type | Wavelength | |
|---|---|---|
| CFL | 405nm | mercury |
| 436nm | mercury | |
| 487nm | terbium | |
| 542nm | terbium | |
| 546nm | mercury | |
| 611nm | europium | |
Click CFL. Use the mouse to select the Eu611 peak on the right. The keys Kp7,Kp9 (Q,E) can be used to fine-tune the selection. Select the Hg436 peak on the left with the mouse; fine-tune with Kp1,Kp3 (Z,C):
Click SAVE - the settings are saved in the calibration file.
| Type | Wavelength | |
|---|---|---|
| CIS | 465nm | blue response peak |
| 532nm | green response peak | |
| 596nm | red response peak | |
| 529nm | the red bump | |
Click CIS. Use the mouse to select the red response peak on the right and the blue response peak on the left. Use the keys Kp7,Kp9 (Q,E) and Kp1,Kp3 (Z,C) to fine-tune the selection:
Click SAVE - the settings are saved in the calibration file.
$ ./spectrometer/plot -h
Usage: ./spectrometer/plot [-H] [-I] [-L] [--CFL] [--CIS] [--INT] CSVfile
Plot Spectrum
Options:
-H Show this message
-B -B1 enable background image. -B0 disable
-L -L1 enable landmarks display. -L0 disable
--CFL Plot pixel averages and CFL landmarks
--CIS Plot color averages and CIS landmarks
--INT Plot pixel averages as filled curve
CSVfile Spectrum data to plot
Spectrum data is ploted with the spectrum background image in the range 375nm - 695nm. Plot opens in gnuplot; use menu bar to save image.
You can also combine the plot options for different results:
