Photobiological Safety of Luminaires: Refining the New Approach

Transcription

1 Photobiological Safety of Luminaires: Refining the New Approach Leslie Lyons Bentham Instruments Limited Reading, UK

2 We are all familiar with the visual characteristics of lighting products

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4 What other impact might these sources have? Glare? Flicker? Circadian Disruption (or therapy)? Photobiological Safety Hazards?

5 Since 2006: IEC Photobiological Safety of Lamps and Lamp Systems Electrically powered incoherent broadband sources of optical radiation ( nm) Risk group classification scheme Hazard Wavelength Range (nm) Actinic UV Near UV Blue Light Retinal Thermal IR Radiation Eye Thermal Skin

6 Photobiological Safety Assessment Measurement of Spectral Irradiance ( nm) Evaluate hazards to the skin and front surfaces of eye Measurement of Spectral Radiance ( nm) Evaluate hazards to the retina Measurement distance 200mm/ 500 lux

7 The Case of Lamps and Luminaires The GLS approach led to concerns within the lighting industry Which sources considered GLS? Result of majority of GLS evaluations: Exempt 500 lux may not represent realistic exposure scenario

8 New Approach IEC TC 34 New approach based on lamp type considering:- Actinic UV hazard (2 mw.klm -1 ) IR Hazard (marking only) Blue Light Hazard implementing IEC TR : Application of IEC for the assessment of blue light hazard to light sources and luminaires

9 Photobiological Safety in Vertical Standards Standard UV Blue IR Ed 2.2 Tungsten filament lamps for domestic and similar general lighting N N N purposes Ed.2.2 Tungsten halogen lamps for domestic and similar general lighting N N N purposes Ed 2 Tungsten halogen lamps (non-vehicle) Y N Y 60968:Ed 3 Self-ballasted lamps for general lighting services Y N N Ed 2.2 Double-capped fluorescent lamps Y N N Ed 3.2 Single-capped fluorescent lamps Y N N Ed 2 Discharge lamps (excluding fluorescent lamps) Y Y N Ed 2.2 LED modules for general lighting Y Y N Ed 1 Self-ballasted LED-lamps for general lighting services by voltage > 50 V Y Y N Ed 1 Double-capped LED lamps for general lighting services Y Y N Ed 1 Non-ballasted LED-lamps Y Y N Ed 8 Luminaires Part 1: General requirements and tests Y Y N

10 IEC TR Considers only blue light hazard of component lamps/ LEDs and finished product luminaires RG1 considered safe Determine if blue light hazard RG1 or below at 200mm Significant driver to reduce measurement burden for luminaire manufacturers

11 Factors Impacting Retinal Irradiance Solid angle, Ω, subtended by pupil at viewing distance Ω (Time-dependent) retinal image of angular size, α α α

12 Time Dependence of Retinal Irradiance Increasing Exposure Time Exposure Time (s) Angle of Acceptance (mrad) < (t/10) t >

13 Blue Light Hazard RG1 Risk group definitions from IEC Risk Group No Hazard within (s) Blue Light Hazard Acceptance Angle (mrad) Limit (W.m -2.sr -1 ) Exempt Group Group mrad = 0.063

14 Spatially Averaged Radiance Source of radiance L, considered uniform Measured radiance in 11mrad, L 11 = L. (Area of chip within FOV)/ (Area FOV) 200mm, 11mrad L 11 = L 200mm, 11mrad L 11 < L

15 Blue Light Hazard Weighting Function

16 Blue Light Hazard Efficacy of Luminous Radiation K B,V = E B /E v = L B /L v E B, L B blue light irradiance/ radiance E V, L V illuminance/ luminance

17 Possible Assessment Results Component Lamps or LEDs Finished Products RG0 unlimited (very rare) RG0 (very rare) RG1 unlimited RG1 E thr Threshold illuminance (lx) at which RG1 found d thr Threshold distance (m) at which RG1 found Blue Light Hazard Risk Group No Hazard within (s) Acceptance Angle (mrad) Limit (W.m -2.sr -1 ) Exempt Group

18 Origin of E thr Consider blue light radiance in 11mrad FOV as irradiance, E 11 =L 11. Ω 11 RG1 blue light irradiance limit = 1 W.m -2 Use K B,V = E B /E V, set E B = 1 W.m-2, E V = E thr E thr = 1/ K B,V

19 Conditions for Transfer of Data Component Lamps or LEDs RG0 unlimited (very rare) RG1 unlimited Small source, <2.2mm, FOV under-filled Large source, >2.2mm, FOV over-filled E thr Threshold illuminance (lx) at which RG1 found

20 One TR, Two Methods In order of accuracy and effort Method A Minimum Input Method B Highest Accuracy CCT CCT and luminance Source dimensions Spectral radiance (300 nm to 780 nm) E thr RG0 (unlimited) RG1 (unlimited) E thr RG0 unlimited RG1 (unlimited) E thr Includes safety factor 2 Over estimation of the hazard None

21 Limits and Classifications- Source 2.2mm Spectral Radiance in 11mrad FOV at 200mm nm Result (W.m -2.sr -1 ) Assessment Component Lamp/ LED Finished Product L B <100 RG0 Unlimited RG0 L B < RG1 Unlimited RG1 L B Report E thr Report d thr

22 Limits and Classifications- Source < 2.2mm Spectral Irradiance at 200mm nm Result (W.m -2 ) Assessment Component Lamp/ LED Finished Product E B < 1 Report E thr RG1 E B >1 Report E thr Report d thr In practice no luminaires will be so small!

23 Technique to Find d thr Find the peak intensity, I p (cd), (obtained from goniophotometric data) Ensure normalised intensity data (cd/klm) multiplied by luminaire luminous flux to obtain intensity Determine d thr from d thr = ( I p /E thr ) Validity of use of inverse square law in question

24 Consideration of Reported d thr

25 Determination of Realistic d thr Annex D attempts to guide user towards a validation/ refinement of d thr Includes guidance to determine d thr for one emitter of an array- how to realise this? Determination of a realistic d thr will represent a significant challenge

26 Factors Impacting Retinal Irradiance Solid angle, Ω, subtended by pupil at viewing distance Ω Narrow spot 6 Spot 14 Flood 28 Wide Flood 53

27 Factors Impacting Retinal Irradiance (Time-dependent) retinal image of angular size, α α α

28 Reduction Factor Required Given typical radiance of current LED technology Source Blue Light Radiance (W.m -2.sr -1 ) 6500K White PC-LED ~2x 10 4 Blue LED ~8x 10 4 Spatially averaged radiance reduction factor typically 2-8 times Considering overlap of FOV and LED emission area, require from 2 to 8 distance Increased distance where multiple emitters fall within FOV Reduction due to proportion of beam falling in pupil solid angle to be considered

29 Omni-Directional Sources It is likely that the computed value of d thr be overly conservative Repeat spectral radiance measurement at 400mm and where required 600mm It is not expected that d thr exceed this value except for blue LEDs Report as d thr the minimum distance at which L B < W.m -2.sr -1

30 Directional Sources The narrower the beam angle, the greater d thr Evaluate whether or not the source extends beyond circle of diameter d thr Repeat spectral radiance measurement at multiples of 0.5m below d thr

31 Treatment of Laser Lamps Will laser lamps come to lighting applications? Clause 4.4 of IEC : 2014 applies Currently not in scope of IEC TR 62778

32 Evolution of LED Techology Some propose violet LED pumped PC-LEDs in lieu of blue LED pump ostensibly to render objects as sunlight Consideration should be given to the aphakic eye Pump Blue Light Radiance (W.m -2.sr -1 ) Aphake Radiance (W.m -2.sr -1 ) 405nm ~1.1x 10 4 ~1.9x nm ~1.5x 10 4 ~1.5x 10 4

33 The Last Word Product standards in lighting applications now consider photobiological safety The measurement procedure is simplified. until RG1 limit exceeded! A measurement-based refinement of d thr will avoid excessive over-estimation Any Questions? Please fire away... Or llyons@bentham.co.uk Thank You for your attention