LED Evenement 2014 Spectroscopy - Straylight. Avantes BV Apeldoorn, The Netherlands

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Natalie Goodman
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1 LED Evenement 2014 Spectroscopy - Straylight Avantes BV Apeldoorn, The Netherlands

2 Content: - Company - Spectroscopy - Spectrometer measuring light - Straylight - How to prevent - Why - conclusion

4 Introduction Since 1993 about spectrometers sold More than 100 different applications Lighting is important market Many options for different applications Modular product design

5 Light

6 UV-C nm UV-B nm UV-A nm violet blue bluegreen green yellowgreen yellow orange red IR-A nm IR-B 1400nm - 3,0µm IR-C 3,0µm - 1mm 100nm 200nm 400nm 600nm 800nm 1000nm 1200nm 1400nm 1600nm 1800nm 3,0µm 1mm Optical Radiation / Light UV: Ultraviolett Radiation VIS: Visible Radiation; Light IR: Infrared Radiation

$spectrometer an optical device for measuring wavelengths, deviation of refracted rays, and angles between faces of a prism, especially an instrument (prism$

8 spectrometer an optical device for measuring wavelengths, deviation of refracted rays, and angles between faces of a prism, especially an instrument (prism spectrometer) consisting of a slit through which light passes, a collimator, a prism that deviates the light, and a telescope through which the deviated light is viewed and examined.

9 Spectrometer the core technology 10

10 Irradiance/Illuminance Unit: W/cm2 or lm/cm2=lx

11 Calibration Convert Raw Data To Real Data

13 CIE 1931 Chromaticity Diagram chromaticity coordinates x,y x = X / (X + Y + Z) y = Y / (X + Y + Z)

14 Spectral quantities for LEDs Peak wavelength λ p Spectral width (at half intensity levels) - also denoted as λ (FWHM). Centroid wavelength λ c center of gravity wavelength 1.0 S( ) p c ² 0.5 (nm)

Colorimetry Dominant wavelength (DW) A straight line from the white point E to the measured color coordinates intersects the boundary of the color diagram at the dominant wavelength.

15 Colorimetry Dominant wavelength (DW) A straight line from the white point E to the measured color coordinates intersects the boundary of the color diagram at the dominant wavelength. Purity: m/(l+m) Is the ratio of the length of the line from the white point E to the chromaticity point and the length of the line from E to the boundary of the chromaticity chart. Purity is always givenin %. DW l S m CDW S Complimentary DW (CDW) A=380nm, B=700 nm

16 AvaSoft Irradiance chart

17 But the results can be negativly influenced by straylight

18 Stray light Sources of stray light Ambient light (black enclosure) Fiber entrance cladding transport (mode stripper) Scattering of grating/mirrors Typ < 0,05% at 435 nm Typ < 0,02% at 600 nm Order overlap Order sorting filters (long pass for V, N and I gratings) Order sorting coating

19 Ambient light

20 AvaSpec-ULS Optical Optical Bench Design: Symmetrical Czerny Turner CPC light traps Detector Focusing mirror Grating SMA connector CPC light traps Collimating mirror Slit, mode stripper 2 nd mode stripper

21 Straylight due to Cladding transport Modestripper Cladding Core

22 Modestrippers

23 Diffractional Gratings: background Grating normal incident light + - diffracted light β 1 α β 0 β 2 nd order -1 β -2 Aluminum coated Ruled lines d Substrate BK7 optical glass

$Diffractional Gratings: background Grating normal incident light + - diffracted light$

24 Diffractional Gratings: background Grating normal incident light + - diffracted light β 1 α β 0 β 2 nd order -1 β -2 Aluminum coated Ruled lines d Substrate BK7 optical glass

25 Scrattering from defects

26 CPC light traps Parabolic shape focussses light into focuspoint - Extinction

27 Diffractional Gratings: background Grating normal incident light + - diffracted light β 1 α β 0 β 2 nd order -1 β -2 Aluminum coated Ruled lines d Substrate BK7 optical glass

28 OSC-UA/OSC-UB/OSC-HS500 Second order overlap 200 nm 350nm 550 nm 850 nm 1100 nm No filter LP filter >350nm LP filter > 600 nm

29 Filter at Spectrometer entrance Placement of a filter at the entrance to prevent unwanted light getting into the spectrometer. For instance:

30 Unwanted reflections causing straylight Black = black? A black object may reflect (invisible wavelengths) instead of absorbing it.? =

31 How is straylight measured? Illuminate with broadband lightsource (Halogen). Place High Pass filter. Light in blocked area is straylight.

32 Effect in result Systems are normally calibrated with a tungsten halogen source. Stray light is in calibration model. A white LED does not have IR wavelengths. -> white LED does create straylight (less) -> Error in calculated data.

33 Calibration error as much as 10% for 1% stray light

34 In the end a measurement device with low straylight gives you better results. Quality counts!

35 Please visit us at booth 8.

Thank you for your attention Ger Loop GerL@avantes.

36 Thank you for your attention Ger Loop Oude Apeldoornseweg 28 NL-7333 NS APELDOORN The Netherlands, Europe Tel +31-(0) Fax +31-(0)

Control of Light. Emmett Ientilucci Digital Imaging and Remote Sensing Laboratory Chester F. Carlson Center for Imaging Science 8 May 2007

Control of Light. Emmett Ientilucci Digital Imaging and Remote Sensing Laboratory Chester F. Carlson Center for Imaging Science 8 May 2007 Control of Light Emmett Ientilucci Digital Imaging and Remote Sensing Laboratory Chester F. Carlson Center for Imaging Science 8 May 007 Spectro-radiometry Spectral Considerations Chromatic dispersion