Presentation is loading. Please wait.

Presentation is loading. Please wait.

LED photobiology János Schanda University of Pannonia Virtual Environment and Imaging Technologies Laboratory.

Similar presentations


Presentation on theme: "LED photobiology János Schanda University of Pannonia Virtual Environment and Imaging Technologies Laboratory."— Presentation transcript:

1 LED photobiology János Schanda University of Pannonia Virtual Environment and Imaging Technologies Laboratory

2 Overview Introduction Introduction Optical radiation Optical radiation LED emission spectra LED emission spectra Human eye transmission Human eye transmission Optical hazards Optical hazards Conclusions and summary Conclusions and summary

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

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

5 Penetration of UV radiation into the eye After Sliney DH, Wolbarsht ML. Safety with Lasers and Other Optical Sources. (New York: Plenum Publishing Corp); After Sliney DH, Wolbarsht ML. Safety with Lasers and Other Optical Sources. (New York: Plenum Publishing Corp); 1980.

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

7 Some photobiological hazard definitions see CIE S 009:2002 Photobiological safety of lamps and lamp systems actinic dose (see ILV ) actinic dose (see ILV ) Quantity obtained by weighting spectrally the dose according to the actinic action spectrum value at the corresponding wavelength. Quantity obtained by weighting spectrally the dose according to the actinic action spectrum value at the corresponding wavelength. Unit: Jm -2 Unit: Jm -2 Note: This definition implies that an action spectrum is adopted for the actinic effect considered, and that its maximum value is generally normalized to 1. When giving a quantitative amount, it is essential to specify which quantity dose or actinic dose is meant, as the unit is the same. Note: This definition implies that an action spectrum is adopted for the actinic effect considered, and that its maximum value is generally normalized to 1. When giving a quantitative amount, it is essential to specify which quantity dose or actinic dose is meant, as the unit is the same. angular subtense (α) angular subtense (α) Visual angle subtended by the apparent source at the eye of an observer or at the point of measurement. Visual angle subtended by the apparent source at the eye of an observer or at the point of measurement. Unit: radian Unit: radian Note: The angular subtense α will generally be modified by incorporation of lenses and mirrors as projector optics, i.e. the angular subtense of the apparent source will differ from the angular subtense of the physical source. Note: The angular subtense α will generally be modified by incorporation of lenses and mirrors as projector optics, i.e. the angular subtense of the apparent source will differ from the angular subtense of the physical source.

8 Some photobiological hazard definitions see CIE S 009:2002 Photobiological safety of lamps and lamp systems blue light hazard (BLH) blue light hazard (BLH) Potential for a photochemically induced retinal injury resulting from radiation exposure at wavelengths primarily between 400 nm and 500 nm. This damage mechanism dominates over the thermal damage mechanism for times exceeding 10 seconds. Potential for a photochemically induced retinal injury resulting from radiation exposure at wavelengths primarily between 400 nm and 500 nm. This damage mechanism dominates over the thermal damage mechanism for times exceeding 10 seconds. erythema (see ILV ) erythema (see ILV ) Reddening of the skin; as used in this standard the reddening of the skin resulting from inflammatory effects from solar radiation or artificial optical radiation. Reddening of the skin; as used in this standard the reddening of the skin resulting from inflammatory effects from solar radiation or artificial optical radiation. Note: The degree of delayed erythema is used as a guide to dosages applied in ultraviolet therapy. Note: The degree of delayed erythema is used as a guide to dosages applied in ultraviolet therapy. ocular hazard distance ocular hazard distance Distance from a source within which the radiance or irradiance for a given exposure duration exceeds the applicable exposure limit. Distance from a source within which the radiance or irradiance for a given exposure duration exceeds the applicable exposure limit. Unit: m Unit: m

9 Some photobiological hazard definitions see CIE S 009:2002 Photobiological safety of lamps and lamp systems general lighting service (GLS) lamps general lighting service (GLS) lamps Term for lamps intended for lighting spaces that are typically occupied or viewed by people. Examples would be lamps for lighting offices, schools, homes, factories, roadways, or automobiles. It does not include lamps for such uses as film projection, reprographic processes, "suntanning", industrial processes, medical treatment and searchlight applications. Term for lamps intended for lighting spaces that are typically occupied or viewed by people. Examples would be lamps for lighting offices, schools, homes, factories, roadways, or automobiles. It does not include lamps for such uses as film projection, reprographic processes, "suntanning", industrial processes, medical treatment and searchlight applications. large source large source Size of the source image on the retina which is so large that radial heat flow in the radial direction from the centre of the image to the surrounding biological tissue is negligibly small compared to heat flow in the axial direction. Size of the source image on the retina which is so large that radial heat flow in the radial direction from the centre of the image to the surrounding biological tissue is negligibly small compared to heat flow in the axial direction.

10 Some photobiological hazard definitions see CIE S 009:2002 Photobiological safety of lamps and lamp systems photokeratoconjunctivitis photokeratoconjunctivitis Inflammatory response of the cornea and conjunctiva following exposure to ultraviolet (UV) radiation. Wavelengths shorter than 320 nm are most effective in causing this condition. The peak of the action spectrum is approximately at 270 nm. Inflammatory response of the cornea and conjunctiva following exposure to ultraviolet (UV) radiation. Wavelengths shorter than 320 nm are most effective in causing this condition. The peak of the action spectrum is approximately at 270 nm. Note: Different action spectra have been published for photokeratitis and photoconjuctivitis (CIE 106/2 and CIE 106/3– 1993); however, the latest studies support the use of a single action spectrum for both ocular effects (CIE 106/1–1993). Note: Different action spectra have been published for photokeratitis and photoconjuctivitis (CIE 106/2 and CIE 106/3– 1993); however, the latest studies support the use of a single action spectrum for both ocular effects (CIE 106/1–1993). retinal hazard region retinal hazard region Spectral region from 380 nm to 1400 nm (visible plus IR-A) within which the normal ocular media transmit optical radiation to the retina. Spectral region from 380 nm to 1400 nm (visible plus IR-A) within which the normal ocular media transmit optical radiation to the retina. exposure limits exposure limits Individuals in the vicinity of lamps and lamp systems shall not be exposed to levels exceeding the limit Individuals in the vicinity of lamps and lamp systems shall not be exposed to levels exceeding the limit exposure limits apply to continuous sources where the exposure duration is not less than 0,01 ms and not more than any 8-hour period. exposure limits apply to continuous sources where the exposure duration is not less than 0,01 ms and not more than any 8-hour period.

11 Eye hazard spectra after CIE TC 6-55 draft report

12 Actinic UV hazard spectrum for skin and eye

13 Blue light hazard Retinal blue light hazard exposure limit Retinal blue light hazard exposure limit To protect against retinal photochemical injury from chronic blue- light exposure, the integrated spectral radiance of the light source weighted against the blue-light hazard function, B(λ), i.e., the blue light weighted radiance, L B, shall not exceed the levels defined by: To protect against retinal photochemical injury from chronic blue- light exposure, the integrated spectral radiance of the light source weighted against the blue-light hazard function, B(λ), i.e., the blue light weighted radiance, L B, shall not exceed the levels defined by: where: L(λ,t) is the spectral radiance in Wm -2 sr -1 nm -1, B(λ) is the blue-light hazard weighting function, B(λ) is the blue-light hazard weighting function, λ is the bandwidth in nm, λ is the bandwidth in nm, t is the exposure duration in seconds. t is the exposure duration in seconds.

14 Blue light hazard Retinal blue light hazard exposure limit - small source Retinal blue light hazard exposure limit - small source For a light source subtending an angle less than 0,011 radian the limits lead to a simpler equation. Thus the spectral irradiance at the eye E λ, weighted against the blue-light hazard function B(λ) shall not exceed the levels defined by: For a light source subtending an angle less than 0,011 radian the limits lead to a simpler equation. Thus the spectral irradiance at the eye E λ, weighted against the blue-light hazard function B(λ) shall not exceed the levels defined by: where: E λ (λ,t) is the spectral irradiance in Wm -2 nm -1, where: E λ (λ,t) is the spectral irradiance in Wm -2 nm -1, B(λ) is the blue light hazard weighting function, B(λ) is the blue light hazard weighting function, λ is the bandwidth in nm, λ is the bandwidth in nm, t is the exposure duration in seconds. t is the exposure duration in seconds. For a source where the blue light weighted irradiance, E B For a source where the blue light weighted irradiance, E B exceeds 0,01 Wm -2, the maximum permissible exposure exceeds 0,01 Wm -2, the maximum permissible exposure duration shall be computed: s, for t 100 s duration shall be computed: s, for t 100 s t max is the maximum permissible exposure duration in seconds, t max is the maximum permissible exposure duration in seconds, E B is the blue light hazard weighted irradiance. E B is the blue light hazard weighted irradiance.

15 Blue light hazard (B) and retinal burn (R) hazard spectrum

16 Retinal burn hazard Retinal thermal hazard exposure limit Retinal thermal hazard exposure limit To protect against retinal thermal injury, the integrated spectral radiance of the light source, L λ, weighted by the burn hazard weighting function R(λ), i.e., the burn hazard weighted radiance, shall not exceed the levels defined by: To protect against retinal thermal injury, the integrated spectral radiance of the light source, L λ, weighted by the burn hazard weighting function R(λ), i.e., the burn hazard weighted radiance, shall not exceed the levels defined by:where: L λ is the spectral radiance in Wm -2 sr -1 nm -1, L λ is the spectral radiance in Wm -2 sr -1 nm -1, R(λ) is the burn hazard weighting function, R(λ) is the burn hazard weighting function, t is the viewing duration (or pulse duration if the lamp is pulsed), in seconds, t is the viewing duration (or pulse duration if the lamp is pulsed), in seconds, λ is the bandwidth in nm, λ is the bandwidth in nm, α is the angular subtense of the source in radians. α is the angular subtense of the source in radians.

17 Physiological radiance/irradiance and time average Physiological radiance/irradiance and time average Radiance weighted according to the action spectrum of the given hazard Radiance weighted according to the action spectrum of the given hazard Thermal effects: important the heat conduction of the tissue away from the irradiation site, the irradiated tissue volume and the irradiance – local burn. Thermal effects: important the heat conduction of the tissue away from the irradiation site, the irradiated tissue volume and the irradiance – local burn. Size of irradiation important!, irradiance dependent, W/m 2. Size of irradiation important!, irradiance dependent, W/m 2. Photochemical effects: strong wavelength dependence, follows Bunsen-Roscow law. Photochemical effects: strong wavelength dependence, follows Bunsen-Roscow law. Radiant exposure, J/m 2, dependence. Radiant exposure, J/m 2, dependence.

18 Ocular hazards Radiation between 380 nm and 1400 nm reaches the retina. Radiation between 380 nm and 1400 nm reaches the retina. Light source focused on retina Light source focused on retina Retinal irradiance: Retinal irradiance: E r = L s D e 2 /(4f 2 ) E r = L s D e 2 /(4f 2 )where: E r : retinal irradiance E r : retinal irradiance L s : source radiance L s : source radiance f: : effective focal length of eye f: : effective focal length of eye D e : pupil diameter D e : pupil diameter transmittance of ocular media transmittance of ocular media A worst-case assumption is: E r = 0.12 L s A worst-case assumption is: E r = 0.12 L s This linear dependence of retinal irradiance of source radiance breaks down for small sources, lasers. This linear dependence of retinal irradiance of source radiance breaks down for small sources, lasers. Thus retinal safety limits for 300/380 nm – 1400 nm are given in W/m 2 or J/m 2 Thus retinal safety limits for 300/380 nm – 1400 nm are given in W/m 2 or J/m 2

19 Lamp hazard groups Exempt group Exempt group the lamp does not pose any photobiological hazard if it does not pose: the lamp does not pose any photobiological hazard if it does not pose: an actinic ultraviolet hazard (E s ) within 8-hours exposure (30000 s), nor an actinic ultraviolet hazard (E s ) within 8-hours exposure (30000 s), nor a near-UV hazard (E UVA ) within 1000 s, (about 16 min) nor a near-UV hazard (E UVA ) within 1000 s, (about 16 min) nor a retinal blue-light hazard (L B ) within s (about 2,8 h), nor a retinal blue-light hazard (L B ) within s (about 2,8 h), nor a retinal thermal hazard (L R ) within 10 s, nor a retinal thermal hazard (L R ) within 10 s, nor an infrared radiation hazard for the eye (E IR ) within 1000 s. an infrared radiation hazard for the eye (E IR ) within 1000 s. Low risk group Low risk group an actinic ultraviolet hazard (E s ) within s, nor an actinic ultraviolet hazard (E s ) within s, nor a near ultraviolet hazard (E UVA ) within 300 s, nor a near ultraviolet hazard (E UVA ) within 300 s, nor a retinal blue-light hazard (L B ) within 100 s, a retinal blue-light hazard (L B ) within 100 s, …. ….

20 Emission limits for risk groups of continuous wave lamps

21 Lamp risk categories- acceptance anglesLamp risk categories- acceptance angles Eye movement, time dependent smear effect taken into consideration Eye movement, time dependent smear effect taken into consideration

22 Differences betwen the CIE and IEC regulations

23 Lamp safety measurement conditions of Measurement distance: Measurement distance: Minimum viewing distance: 200 mm Minimum viewing distance: 200 mm GSL lamps: at a distance where it produces 500 lx GSL lamps: at a distance where it produces 500 lx Measurement aperture: Measurement aperture: Maximum human pupil size: 7 mm Maximum human pupil size: 7 mm Source size and angular subtense: Source size and angular subtense: Thermal retinal hazard depends on irradiated surface (heat flow) Thermal retinal hazard depends on irradiated surface (heat flow) 380nm-1400nm: eye focuses- minimum angular subtense: min =1.7mrad 380nm-1400nm: eye focuses- minimum angular subtense: min =1.7mrad Maximal angular subtense: max =100mrad Maximal angular subtense: max =100mrad

24 Lamp safety regulation measurements Physiological (time integrated) radiance: Radiant power passing through a defined aperture stop (pupil) at a defined distance Physiological (time integrated) radiance: Radiant power passing through a defined aperture stop (pupil) at a defined distance Aperture area defines solid collection angle (sr) and measurement area: field of view: FOV, measured by the acceptance angle: Aperture area defines solid collection angle (sr) and measurement area: field of view: FOV, measured by the acceptance angle:

25 Time dependence of acceptance angle to be used Due to eye movements for short durations small acceptance angles have to be chosen Due to eye movements for short durations small acceptance angles have to be chosen FOV can be over- or under-filled FOV can be over- or under-filled

26 Product safety standard conditions Measurement distance Measurement distance 200 mm meas. distance 200 mm meas. distance (GSLs: distance, where illuminace is 500 lx) (GSLs: distance, where illuminace is 500 lx) Measurement aperture: maximum pupil size, 7 mm diameter Measurement aperture: maximum pupil size, 7 mm diameter Source size & angular subtense Source size & angular subtense Thermal hazard source image size dependent: Thermal hazard source image size dependent: = 2 arctan(apparent source size/2 source distance) = 2 arctan(apparent source size/2 source distance) But min =1.7mrad, max =100 mrad But min =1.7mrad, max =100 mrad Apparent source position Apparent source position

27 Product safety issues CIE S 009/IEC 62471: Photobiological Safety of Lamps and Lamp Systems CIE S 009/IEC 62471: Photobiological Safety of Lamps and Lamp Systems Lamp and lamp system manufacturer requirements Lamp and lamp system manufacturer requirements If applicable FOV ->LED radiance data hold for luminaire If applicable FOV ->LED radiance data hold for luminaire If underfilled, multiple small sources can fall into the FOV area and averaged radiance will sum up! If underfilled, multiple small sources can fall into the FOV area and averaged radiance will sum up! For such applications the true weighted radiance of the source is needed, acceptance angle should not be smaller than 1.7 mrad. For such applications the true weighted radiance of the source is needed, acceptance angle should not be smaller than 1.7 mrad. But LED assemblies with beam shaping optics have to be measured according to the standard. But LED assemblies with beam shaping optics have to be measured according to the standard. P-LEDs (and blue LEDs) might exceed the low-risk group P-LEDs (and blue LEDs) might exceed the low-risk group

28 Example: p-LED, individual LED Blue light hazard exemptLow riskModerte risk unit Accept. angle ,7mRad Limit, W.m -2 sr -1

29 LED-lamp based on LED component evaluation Risk group : low

30 White and coloured LEDs

31 Comparison: halogen incandescent lamp Risk group: low

32 Comparison: CFL

33 Comparison: MetalHalid Risk group: moderate

34 Effective blue light hazard radiance of different light sources allocation of conventional light sources as well as of retrofits LED in terms of their (dose- dependant) blue light hazard. Upper scale: effective B( )-weighted radiance; lower scale: corresponding maximum duration for direct viewing from 200 mm distance (which define the particular RG-limits as indicated by the vertical lines)

35 Comparison of different light sources, relative action (equal luminance) Light sourceaCaC a BL aLaL standardstandard illuminant B (direct sunlight)illuminant standardstandard illuminant D65 (natural daylight)illuminant standardstandard illuminant A (incandescent Tc=2856K)illuminant Halogen HALOLUX CFL DULUX standard Xenon Fluorescence lamp SKYWHITE (Tc=8000 K) Fluorescence lamp (Tc=14000 K) pc-white LED (Tc=3000 K) pc-white LED (Tc=5500 K) pc-white LED (Tc=6500 K) Action spectra weighting: a c : circadian; a B : blue light; a L :lipofuscine-mediated age-related adverse effects

36 CIE S009/IEC62471 requirements, 1

37 CIE S009/IEC62471 requirements, 2

38 Thanks for your kind attention! This publication has been supported by the TÁMOP-4.2.2/B-10/ project.


Download ppt "LED photobiology János Schanda University of Pannonia Virtual Environment and Imaging Technologies Laboratory."

Similar presentations


Ads by Google