www.bentham.co.uk Beyond Illumination Evaluating the Non-Visual Emission Characteristics of Lighting Products Leslie Lyons Technical Support Manager Bentham Instruments Ltd Optical Radiation www.bentham.co.uk Optical radiation is defined as electromagnetic radiation having wavelengths between 100nm to 1mm Consideration typically restricted to 200-3000nm due to atmospheric absorption <200nm and the negligible effect of low energy photons in the far IR Band Wavelength Range (nm) UVC 100-280 (<180nm, vacuum UV) UVB 280-315 UVA 315-400 Visible 380-780 IRA 780-1400 IRB 1400-3000 IRC 3000-10000 Lighting Products: Visual Characteristics www.bentham.co.uk We are all familiar with the visual characteristics of lighting products Sources Having Non-Visual Impact www.bentham.co.uk We are also familiar with sources of light having a non-visual effect… What Other Impact Might Lamps Have? www.bentham.co.uk It is therefore reasonable that lamps may also have other effects than visual…but what? Photometric Flicker? Circadian Disruption (or therapy)? Photobiological Safety Hazards? Photometric Flicker www.bentham.co.uk Recent reports have suggested that some SSL systems, particularly those paired with dimming controls, demonstrate significant photometric flicker Photometric 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 malaise Seizures thought to result from flicker in 3-70 Hz region, whilst “invisible” flicker effects may occur up to 165 Hz Flicker Metrics www.bentham.co.uk Two metrics are currently defined for the evaluation of flicker: percent flicker, and flicker index The latter is generally preferred since it takes account of difference in waveform shape or duty cycle As standards for the evaluation of flicker are developed, account may also be taken of flicker frequency Measurement of Flicker www.bentham.co.uk Whilst 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 Hz Time–resolved source emission captured, flicker calculations performed thereupon Examples of Flicker www.bentham.co.uk Frequency (Hz) Flicker Percent (%) Flicker Index Halogen 100.13 CFL 100.1 GU10 LED 1 100.15 GU10 LED 2 100.18 4.96 1.13 1.36 8.4 0.016 0.004 0.003 0.026 Circadian Rhythm www.bentham.co.uk A circadian rhythm is a ~24 hour cycle in the physiological processes of living beings impacting sleepwake cycles, alertness, performance, core body temperature and the production of the hormones Whilst endogenously generated, the circadian rhythm can be modulated, or entrained, by external cues such as light and heat Research has confirmed existence of melanopsin-based non-visual photoreceptor in eye having inputs to circadian rhythm and pupil response Whilst 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 Circadian Disruption Metric www.bentham.co.uk Whilst most literature cites a 480nm peak response, the only published data in German DIN V 5031100 pre-standard suggests a 450nm peak A metric, comparing the circadian response to visual response, is proposed Evaluation of Circadian Disruption www.bentham.co.uk The spectral distribution of the source is required for this evaluation with subsequent evaluation of acv Incandescent CFL 3000K White LED 10000K White LED Blue LED acv 0.046 0.102 0.043 0.493 0.541 Introduction to Photobiological Safety www.bentham.co.uk Photobiology is the study of the interaction of optical radiation with living organisms Optical radiation is strongly absorbed in tissue, with penetration depths of a few microns in the UV to millimetres in the IR It is the skin and eyes of the human body that are most at risk of exposure IEC62471 Series Standards www.bentham.co.uk IEC62471-1:2006 “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 200-3000nm - Provides exposure limits and framework for classification including risk groups exempt to RG3 - Intended as a horizontal standard IEC TR 62471-2:2009 “Guidance on manufacturing requirements relating to non-laser optical radiation safety” - Provides further guidance in absence of vertical product standards - Non-normative IEC62471 published as EN62471:2008 and harmonised to low voltage directive (LVD) Scope of IEC62471 www.bentham.co.uk Consideration is given to six hazards to skin and eye: Hazard Wavelength Range (nm) Bioeffect Eye Skin Erythema Elastosis Actinic UV 200-400† Near UV 315-400 Cornea - Photokeratitis Conjunctiva - Conjunctivitis Lens – Cataractogenesis Lens – Cataractogenesis Blue Light 300-700† Retina – Photoretinitis Retinal Thermal 380-1400† Retina - Retinal burn IR Radiation Eye 780-3000 Cornea - Corneal burn Thermal Skin 380-3000 Skin burn General Lighting Service lamp (GLS) sources used to illuminate “spaces”, measure at distance at which source produces illuminance of 500 lux All other sources measured at 200mm from (apparent) source The Case of Lamps and Luminaires www.bentham.co.uk Implementation of GLS classification criterion of IEC62471 has provided little satisfaction in the lighting industry, prompting IEC sub-committee SC34A to take action Publication in 2012 of IEC TR 62778 : “Application of IEC 62471 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 The New Lamp/ Luminaire Approach www.bentham.co.uk A consideration of photobiological safety depends on lamp type In certain instances, consideration of UV hazard will remain, as was hitherto the case, in implementing the 2mW/ klm specific effective irradiance limit IR hazard will be considered by one incandescent lamp vertical standard Blue light hazard will be dealt with, where required, in implementation of IEC TR 62778 A Few Words on Blue Light Hazard www.bentham.co.uk Blue light hazard describes the photochemical damage of photoreceptors and the retinal pigmented epithelium Strong 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 time Exposure time IEC TR 62778 www.bentham.co.uk Applies to the evaluation of component lamps/ LEDs to finished product luminaires Evaluation to be performed at 200mm in an 11mrad FOV Where result yields Exempt/ RG1 no further action required => Exempt / RG1 “Unlimited” Where results yields RG2 (LB > 10000 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-2 Recommended Determination of dthr www.bentham.co.uk From spectral measurement of source 300-780nm, 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 dthr The TR recommended method to determine dthr is to use goniophotometric data and the inverse square law Luminance (cd.m-2) ) 1.55E+07 Blue Light Radiance (W.m-2.sr-1) 19624.5 More Accurate Determination of dthr www.bentham.co.uk In many cases, use of the inverse square law is not valid since dthr is close to the source As an alternative, an illuminance meter may be used to determine the location of dthr For arrays, this procedure is incorrect since does not measure in the required 11mrad FOV resulting in the determination of an overly-conservative dthr Future Prospects www.bentham.co.uk As lamp and luminaire standards are harmonised to the LVD, IEC 62471 will no longer be applied directly The implementation of standards on flicker and circadian disruption a long way off Chronic 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 www.bentham.co.uk Thank You for Your Attention Any Questions?