Presentation on theme: "Leslie Lyons Technical Support Manager Bentham Instruments Ltd"— Presentation transcript:
1Leslie Lyons Technical Support Manager Bentham Instruments Ltd Beyond IlluminationEvaluating the Non-Visual Emission Characteristics of Lighting ProductsLeslie LyonsTechnical Support ManagerBentham Instruments Ltd
2Optical RadiationOptical radiation is defined as electromagnetic radiation having wavelengths between 100nm to 1mmConsideration typically restricted to nm due to atmospheric absorption <200nm and the negligible effect of low energy photons in the far IRBandWavelength Range (nm)UVC(<180nm, vacuum UV)UVBUVAVisibleIRAIRBIRC
3Lighting Products: Visual Characteristics Lighting Products: Visual CharacteristicsWe are all familiar with the visual characteristics of lighting products
4Sources Having Non-Visual Impact Sources Having Non-Visual ImpactWe are also familiar with sources of light having a non-visual effect…
5What Other Impact Might Lamps Have? What Other Impact Might Lamps Have?It is therefore reasonable that lamps may also have other effects than visual…but what?Photometric Flicker?Circadian Disruption (or therapy)?Photobiological Safety Hazards?
6Photometric FlickerRecent reports have suggested that some SSL systems, particularly those paired with dimming controls, demonstrate significant photometric flickerPhotometric Flicker is defined as the cyclical variation in visual perception of a light source over time thought to cause photosensitive epilepsy, migraines, headaches and non-specific malaiseSeizures thought to result from flicker in 3-70 Hz region, whilst “invisible” flicker effects may occur up to 165 Hz
7Flicker MetricsTwo metrics are currently defined for the evaluation of flicker: percent flicker, and flicker indexThe latter is generally preferred since it takes account of difference in waveform shape or duty cycleAs standards for the evaluation of flicker are developed, account may also be taken of flicker frequency
8Measurement of Flicker Measurement of FlickerWhilst flicker is a luminance-based property, one can use any input optic to perform this measurement (telescope, cosine-corrected input optic, integrating sphere)Light detection by close-match photometric detector, the output of which coupled to an amplifier and data acquisition system fast enough to respond at least to 100 HzTime–resolved source emission captured, flicker calculations performed thereupon
9Examples of Flicker Halogen CFL GU10 LED 1 GU10 LED 2 Frequency (Hz) Examples of FlickerHalogenCFLGU10 LED 1GU10 LED 2Frequency (Hz)100.13100.1100.15100.18FlickerPercent (%)4.961.131.368.4Flicker Index0.0160.0040.0030.026
10Circadian RhythmA circadian rhythm is a ~24 hour cycle in the physiological processes of living beings impacting sleep-wake cycles, alertness, performance, core body temperature and the production of the hormonesWhilst endogenously generated, the circadian rhythm can be modulated, or entrained, by external cues such as light and heatResearch has confirmed existence of melanopsin-based non-visual photoreceptor in eye having inputs to circadian rhythm and pupil responseWhilst light stimulus at the “wrong” time may disrupt the circadian rhythm, light therapy could be used for example to entrain the circadian rhythm of house-bound individuals
11Circadian Disruption Metric Circadian Disruption MetricWhilst most literature cites a 480nm peak response, the only published data in German DIN V pre-standard suggests a 450nm peakA metric, comparing the circadian response to visual response, is proposed
12Evaluation of Circadian Disruption Evaluation of Circadian DisruptionThe spectral distribution of the source is required for this evaluation with subsequent evaluation of acvacvIncandescent0.046CFL0.1023000K White LED0.04310000K White LED0.493Blue LED0.541
13Introduction to Photobiological Safety Introduction to Photobiological SafetyPhotobiology is the study of the interaction of optical radiation with living organismsOptical radiation is strongly absorbed in tissue, with penetration depths of a few microns in the UV to millimetres in the IRIt is the skin and eyes of the human body that are most at risk of exposure
14IEC62471 Series StandardsIEC :2006 “Photobiological Safety of Lamps and Lamp Systems”- Gives guidance for evaluating the photobiological safety of lamps and lamp systems emitting optical radiation in the range nm- Provides exposure limits and framework for classification including risk groups exempt to RG3- Intended as a horizontal standardIEC TR :2009 “Guidance on manufacturing requirements relating to non-laser optical radiation safety”- Provides further guidance in absence of vertical product standards- Non-normativeIEC62471 published as EN62471:2008 and harmonised to low voltage directive (LVD)
15Scope of IEC62471Consideration is given to six hazards to skin and eye:HazardWavelengthRange(nm)BioeffectEyeSkinActinic UV†Cornea - PhotokeratitisConjunctiva - ConjunctivitisLens – CataractogenesisErythemaElastosisNear UVBlue Light†Retina – PhotoretinitisRetinal Thermal†Retina - Retinal burnIR Radiation EyeCornea - Corneal burnThermal SkinSkin burnGeneral Lighting Service lamp (GLS) sources used to illuminate “spaces”, measure at distance at which source produces illuminance of 500 luxAll other sources measured at 200mm from (apparent) source
16The Case of Lamps and Luminaires The Case of Lamps and LuminairesImplementation of GLS classification criterion of IEC62471 has provided little satisfaction in the lighting industry, prompting IEC sub-committee SC34A to take actionPublication in 2012 of IEC TR : “Application of IEC for the assessment of blue light hazard to light sources and luminaires”Amendment of lamp and luminaire standards (many of which have already been published) and updated under the LVD
17The New Lamp/ Luminaire Approach The New Lamp/ Luminaire ApproachA consideration of photobiological safety depends on lamp typeIn certain instances, consideration of UV hazard will remain, as was hitherto the case, in implementing the 2mW/ klm specific effective irradiance limitIR hazard will be considered by one incandescent lamp vertical standardBlue light hazard will be dealt with, where required, in implementation of IEC TR 62778
18A Few Words on Blue Light Hazard A Few Words on Blue Light HazardBlue light hazard describes the photochemical damage of photoreceptors and the retinal pigmented epitheliumStrong wavelength dependence, peaking in the blue spectral region (hence the name)The evaluation of the retinal blue light hazard requires taking account of the irradiance of the retinal image and the area of the retina irradiated for a given exposure timeExposure time
19IEC TR 62778Applies to the evaluation of component lamps/ LEDs to finished product luminairesEvaluation to be performed at 200mm in an 11mrad FOVWhere result yields Exempt/ RG1 no further action required => Exempt / RG1 “Unlimited”Where results yields RG2 (LB > W.m-2.sr-1), the distance at which source becomes RG1 should be determined using the RG1 blue light small source limit of 1 W.m-2HazardExemptRG1RG2RG3Blue Light-CAUTION. Possibly hazardous optical radiation emitted from this product. Do not stare at operating lamp. May be harmful to the eyeWARNING. Possibly hazardous optical radiation emitted from this product. Do not look at operating lamp. Eye injury may result.
20Recommended Determination of dthr Recommended Determination of dthrFrom spectral measurement of source nm, can determine ratio of illuminance/ luminance to blue light irradiance/ radiance (numerically the same)Determine illuminance, Ethr, at which blue light small source RG1 limit of 1 W.m-2 obtained (= luminance (cd.m-2)/ blue light radiance (W.m-2.sr-1))For component LEDs, report Ethr, for finished products determine dthrThe TR recommended method to determine dthr is to use goniophotometric data and the inverse square lawLuminance(cd.m-2) )1.55E+07Blue Light Radiance(W.m-2.sr-1)
21More Accurate Determination of dthr More Accurate Determination of dthrIn many cases, use of the inverse square law is not valid since dthr is close to the sourceAs an alternative, an illuminance meter may be used to determine the location of dthrFor arrays, this procedure is incorrect since does not measure in the required 11mrad FOV resulting in the determination of an overly-conservative dthr
22Future ProspectsAs lamp and luminaire standards are harmonised to the LVD, IEC will no longer be applied directlyThe implementation of standards on flicker and circadian disruption a long way offChronic low level exposure should be considered (for example, potential age-related macular degeneration)Lamp technology is still on the move with the use of UV rather than blue LEDs and even laser diodes to pump phosphors- the impact of which is yet to be seen
23Thank You for Your Attention Thank You for Your AttentionAny Questions?