Experimenting from a distance: optical spectrometry via the Internet Lars-Jochen Thoms.

Experimenting from a distance:optical spectrometry via the Internet

Lars-Jochen Thoms


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Munich, Bavaria, Germany

Workshop on Remote Experiments for HE, Milton Keynes, 17.04.2015

Lars-Jochen Thoms


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physics

spectrometry

biophysics astrophysics

chemistry

eligible curriculum inBavarian higher education


Lars-Jochen Thoms


remotely controlled laboratory (RCL)

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user

server

webcam

outline

educational POV

physical POV technical POV


Lars-Jochen Thoms


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physical POV

light source spectrometeroptical fiber

350 450 550 650 750 850 9500

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wavelength in nm

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nsi

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specifications• linear silicon CCD array• 650 enabled pixels• 350-1000 nm• 12 bit A/D resolution• 75 photons/count

@400nm• 25 µm entrance slit• ~2.0 nm FWHM


Lars-Jochen Thoms


350 450 550 650 750 850 9500

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wavelength in nm

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physical POV

problems• especially advanced

learners identify the acquired spectrum asblack-body radiation

• Mind spectral sensitivity!

• knowledge about the measurement processcritical attitude

• no energy information given

• absolute irradiance measurement needed

350 400 450 500 550 600 650 700 750 800 850 900 950 10001

10

100

1000

10000

spectral sensitivity

wavelength in nmmeg

ap

hoto

ns p

er

cou

nt

lg

x 1000


Lars-Jochen Thoms


obtain calibration data

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radiometric calibration standardcalibrated tungsten halogen light source

fit sample spectrum toknown spectral power

distribution

calibrationfactor

in µJ/count per pixel


Lars-Jochen Thoms


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350 450 550 650 750 850 9500

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from apparent to true spectrumsample [count]dark [count]sample-dark [count]absolute irradiance [µW/cm²/nm]

wavelength in nm

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nsi

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ab

solu

te i

rrad

ian

ce i

n µ

W/c

m²/

nm

spectralirradianc

e

darkspectru

m

acquired sample

calibration

factor A Δt Δλ: : :sample - dark


Lars-Jochen Thoms


cosine-corrected probe

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light source spectrometer

true spectral irradiance needs 180° field of view

optical fiber

diffusing material:opaline glass~180° FOV

© Ocean Optics, Inc


Lars-Jochen Thoms


pusher.com

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technical POV

client

WebSocket service (RESTful)• distribute spectral data• distribute control data• user information• authenticated users

web server

http service (PHP)• authentication• provide

website

RCL spectrometer serverwindows service (C#)• acquire spectrum• calculate irradiance• push data via

WebSocket• listen for control data• control experiment

IP cam

• capture video stream

spectral irradianc

e

acquired sample

HTML5 browser (JS)• display spectra• control experiment• ask for authentication• display webcam

control ?

special challenge:very high restrictionsin German schools!

no static ip needed!

DATABASEdatabase

assessment


Lars-Jochen Thoms


control

# 11GIREP-MPTL 2014, Palermo, 08.07.2014Lars-Jochen Thoms, Raimund Girwidz

technical POV

light source


optical fiber

spectrometer• set acquisition

parameters• integration time• boxcar width• samples to average

• choose light source• tungsten lamps• tungsten halogen

lamps• compact fluorescent

lamps• light emitting diodes• light bulbs• reflector lamps

carousel


control


technical POV

light source


spectrometer

• set acquisition parameters• integration time• boxcar width• samples to average




carousel

optical fiber


control


technical POV





• move probe• ca. 1.5 m x 1.0 m


control

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technical POV







Lars-Jochen Thoms


control

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technical POV






• rotate probe• - 90° to 90°• (360° possible)• automatic available

many different parameters

a lot of opportunities

authentic experimenting


Lars-Jochen Thoms


# 16Workshop on Remote Experiments for HE, Milton Keynes, 17.04.2015

Lars-Jochen Thoms

predefined setups


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educational POV


Lars-Jochen Thoms

context based anchored instruction

objectives:• compare and rate spectra from

different light sources


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objectives:• compare and rate spectra from

different light sources• assess color temperature and

color fault • compare with color sensitivity

of the human eye• distinguish between physical

and physiological quantities

educational POV


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objectives:• analyze energy efficiency

educational POV


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objectives:• measure -decrease of radiation

with growing distance

educational POV

Compact Fluorescent Lamps:differences can be noticed betweenthe light coming from the gas dischargeand light coming from the fluorescent layer


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objectives:• examine, distinguish, classify,

and rate the directional characteristics of radiation from different light sources

educational POV

Schultz (2010)

from introductory school physicsto advanced university courses


Lars-Jochen Thoms


# 22Workshop on Remote Experiments for HE, Milton Keynes, 17.04.2015

Lars-Jochen Thoms


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educational POV


Lars-Jochen Thoms

multiple representations

augmented reality


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educational POV


Lars-Jochen Thoms

augmented reality


feedback

free formula input


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educational POV


Lars-Jochen Thoms

augmented reality


feedback

scaffoldingcross-linking multiple representations

linking theory and practice


Thank you for your attention!

Lars-Jochen Thoms

myrcl.org

Experimenting from a distance: optical spectrometry via the Internet Lars-Jochen Thoms.

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