PLOTS SPECTROSCOPE

webcam + DVD + slit + case + software

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Digital Spectroscope

Clip on device for smartphone ($10)

Desktop kit uses a webcam ($40)

Public Laboratory (and kickstarter)

Spectral Workshop

•Online (share camera)•Offline (no longer supported, but available)

•Allows calibration of spectra captured by camera•Uses CFL spectra (mercury lines)

CFL spectrum overlaid with intensityCALIBRATION

436nm blue line 546nm green line

Some Captured Spectra

Calibration using CFL – standard spectra Mercury discharge lamp

Solar spectrum Green laser 484nm

Osram Biolux lamp Halogen

Strontium chloride Red Bull (for absorbance)

Photosynthetically Active Radiation (PAR)

http://publiclaboratory.org/notes/cfastie/3-16-2013/par

Absorbance using halogen (probably) as source lamp (baseline) and subtracting light transmitted by chlorophyll solution

Beer’s Law

Does coffee obey Beer’s Law (500nm absorbance)http://publiclaboratory.org/notes/akjeff91/3-28-2013/does-coffee-obey-beers-law-spectrometric-investigation

http://publiclaboratory.org/notes/cfastie/3-2-2013/fraunhofer

Fraunhofer’s Lines in Solar Spectrum

http://publiclaboratory.org/notes/straylight/10-14-2012/classroom-flame-spectroscopy

Flame Emission Spectrography

Injecting metal salt solutions into bunsen venturi and analysing the spectra

Wine Analysis By Absorption

http://publiclaboratory.org/notes/warren/1-19-2012/wine-spectroscopy-adam-hasler

Wine in petri dish over incandescent light source baseline, analysed for absorption characteristics

Energy Drink Artificial Colouring

http://publiclaboratory.org/notes/natalieorms/3-28-2013/qualitative-comparison-percent-transmittance-three-energy-drinks-do-conc

More Applications

• Black Body Radiation• LED colour analysis

• Halogen vs Incandescent vs LED lighting

• Stage 2 physics (Balmer Series)

• Stage 2 chemistryhttp://publiclaboratory.org/wiki/spectral-analysis

Sample Spectra

http://www.ausetute.com.au/emissions.html

(not from spectral workbench)

Building The Spectroscope

• Make a slit for the end of the box• Put some DVD plastic over the camera lens• Put the camera in the box, opposite the slit, at

about 45°• Install the software, plug in the camera• Select view• Calibrate• Use

DVD Plastic Diffraction GratingThe DVD plastic from a blank DVD (+/- R) has almost parallel lines printed at 740nm spacing.

These provide a cheap and effective transmission diffraction grating. First order maxima of interference pattern is at around 60 degrees.

The camera and DVD are angled around 50 degrees to introduce an incident angle, which makes the pattern asymmetric. One side of the pattern is now centred in the middle of the camera field of view.

The DVD “grooves” run vertically

The Slit• Aluminium Foil stuck

to a microscope slide

• Sticky tape !

• Smaller slit = better resolution

• 0.5mm is good

• Any old slit works !

Camera and Slit Arrangement

Cover is off the box

The slit to camera distance is dependant on the minimum focusing range of the camera. The longer the distance, the better the resolution

Camera Angle•About 45-60 degrees works well

•Align with slit opening

•Blu Tak is your friend

•Reversing the angle reverses the spectrum order

•Changing the angle also spreads out the spectrum a bit

Spectral Workbench - Offline• Windows Installation Instructions

• You need Spectral Workbench Master (folder 35MB)Apple Quicktime (Quicktime Installer – Use default settings)WinVDIG_101 (installer – Use default settings note that only

version 1.01 works, not newer versions)

• After installing quicktime, you need to: copy C:\Program Files (x86)\QuickTime\QTSystem\QTJava.zip to C:\Program Files (x86)\Java\jre6\lib\ext\QTJava.zip

• After Installing WinVDIG_101 run QTCap, which is a video or webcam stream that allows spectral workbench to capture your webcam through quicktime (QTCap)

• Follow the instructions for QTCap on the next slide, this gets you a webcam feed

WinVDIG - QTCap

Source should be “USB Video Device WDM”

Preview should be “compressed”

The webcam video should come up in the boxes

Run Spectral Workbench

• “Spectral workbench master/spectrometry_kit/application.windows/spectrometry_kit.exe”

• You should see a grey screen and the QTCap window again

• Select the webcam source and preview “compressed”

• Click 'OK'.• In a few seconds, spectral workbench will fire up

Getting The Picture

Adjust sample row by click and drag vertically. It is clumsy !

Getting a Nice Spectra

• Two green lines + sharp blue + many reds• No overexposure• Small slit = good resolution

Mercury Discharge Lamp

Troubleshooting•Grey Screen of Death means WinVDIG or quicktime aren’t set up properly

•Try using the ‘scope with a big slit to get an idea of where the spectrum lies

•Don’t clean the DVD plastic, the purple layer has the lines on it !

•Use the “Adjust Sample Row” to see everything the camera sees, then angle the camera to get the image.

•Reducing reflections inside the box helps the camera auto exposure work

•Don’t be afraid to play with the apparatus, turn the camera or move stuff around

Want to Know More ?

• http://spectralworkbench.org/capture

• https://github.com/jywarren/spectral-workbench