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LED photobiology

LED photobiology. János Schanda University of Pannonia Virtual Environment and Imaging Technologies Laboratory based on the paper by W. Halbbritter , W Horak and J Horak :. CIE Conference Vienna , 2010. Overview. Introduction Optical radiation LED emission spectra

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LED photobiology

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  1. LED photobiology JánosSchanda University of Pannonia Virtual Environment and Imaging Technologies Laboratory basedonthepaperby W. Halbbritter, W Horak and J Horak: CIE ConferenceVienna, 2010

  2. Overview • Introduction • Opticalradiation • LED emissionspectra • Human eyetransmission • Opticalhazards • Conclusions and summary

  3. Optical radiaton - photobiology • UltraViolet radiation: actinic radiation • UV-A: 315 m – 400 nm • UV-B: 280 nm – 315 nm • UV-C: 100 nm – 280 nm • Visible radiation: 380 nm – 780 nm • Infrared radiation • IR-A: 780 nm – 1400 nm • IR-B: 1.4 mm – 3 mm • IR-C: 3 mm – 1 mm

  4. LED emission • LEDs now available from 245 nm • Visible wavelengths + white • Near infrared – optical communication • LED spectrum bandwidth: 20 nm – 40 nm

  5. Penetration of UV radiationintotheeye AfterSliney DH, Wolbarsht ML. Safety with Lasers and Other Optical Sources. (New York: Plenum Publishing Corp); 1980.

  6. Ocularhazards • Photokeratitis, photo-conjuntivitis • Redening of theeye, disaperswithin 24 – 48 hours

  7. Optical hazards • Chemical – biochemical hazards • Photon energy in the range of energy of chemical bonds • Skin damages • Ocular damages • Thermal hazards • Skin damages • Ocular damages

  8. Eyehazardspectraafter CIE TC 6-55 draftreport

  9. Lampriskcathegories-acceptanceangles Eyemovement, timedependentsmeareffecttakenintoconsideration

  10. Lampsafetymeasurementconditionsof • Measurementdistance: • Minimum viewingdistance: 200 mm • GSL lamps: 500 mm • Measurementaperture: • Maximum human pupilsize: 7 mm • Sourcesize and angularsubtense: • Thermalretinalhazarddependsonirradiatedsurface (heat flow) • 380nm-1400nm: eyefocuses- minimum angularsubtense: amin=1.7mrad • Maximalangularsubtense: amax=100mrad

  11. „Physiological” radiance/irradiance and timeaverage • Radianceweightedaccordingtotheactionspectum of thegivenhazard • Thermaleffects: importanttheheatconduction of thetissueawayfromtheirradiation site, theirradiatedtissuevolume and theirradiance – local burn. • Size of irradiationimportan!, irradiancedependent, W/m2. • Photochemicaleffects: strongwavelengthdependence, followsBunsen-Roscowlaw. • Radiantexposure, J/m2, dependence.

  12. Ocularhazards • Radiationbetween 380 nm and 1400 nm reachesthe retina. • Lightsourcefocusedon retina • Retinalirradiance: Er= pLstde2/(4f 2) where: • Er: retinalirradiance • L s: sourceradiance • f: : effectivefocallength of eye • De : pupildiameter • t : transmittance of ocularmedia • A worst-caseassumption is: Er= 0.12 L s • Thislineardependence of retinalirradianceofsourceradiancebreaks down forsmallsources, lasers. • Thusretinalsafetylimitsfor 300/380 nm – 1400 nm aregivenin W/m2or J/m2

  13. Lampsafetyregulationmeasurements • Physiological (timeintegrated) radiance:Radiantpowerpassingthrough a definedaperture stop (pupil) at a defineddistance • ApertureareadefinessolidcollectionangleW(sr) and measurementarea: field of view:FOV (m2), measuredbytheacceptanceangle: g

  14. Time dependence of acceptanceangleto be used • Duetoeyemoventsforshortdurationssmallacceptanceangleshaveto be chosen • FOV can be over- orunder-filled

  15. Productsafety standard conditions • Measurementdistance • 200 mm meas.distance • (GSLs: 500 lxdistance) • Measurementaperture: maximum pupilsize, 7 mm diameter • Sourcesize & angularsubtense • Thermalhazardsource image sizedependent: • = 2 arctan(apparentsourcesize/2 sourcedistance) • Butamin=1.7mrad, amax=100 mrad • Apparentsourceposition

  16. Productsafetyissues • CIE S 009/IEC 62471: Photobiological Safety of Lamps and Lamp Systems • Lamp and lampsystemmanufacturerrequirements • Ifapplicable FOV<sourcearea (overfilled)-> ->LED radiancedata hold forluminaire • Ifunderfilled, multiplesmallsourcescanfallintothe FOV area and averagedradiancewill sum up! • Forsuchapplicationsthetruweightedradiance of thesource is needed, acceptanceangleshouldnot be smallerthan 1.7 mrad. • But LED assembieswithbeamshapingopticshavetobemeasuredaccordingtothe standard. • P-LEDs(and blueLEDs) mightexceedthelow-riskgroup

  17. Example: p-LED, individual LED

  18. LED-lampbasedon LED componentevaluation

  19. CIE S009/IEC62471 requirements, 1

  20. CIE S009/IEC62471 requirements, 2

  21. Thanks for your kind attention!

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