Photobiological Safety for DOMINANT LEDs. Background. Hazard exposure limits (EL)

Transcription

1 Phoobiological Safey for DOMINANT LEDs Background The poenial phoobiological hazard of LEDs was iniially being assessed o be similar o laser in he laser safey sandard by European Sandard Organizaion. However, he assessmen does no ruly represen he LEDs because he radiances difference in boh LED and lasers led o differen applicaions as well as poenial eye hazard levels. The EN (equivalen o IEC 60825) sandard was hen furher revised o accommodae he issues. Finally, he LEDs were removed from he scope of IEC :2007 and published as IEC 62471:2006 Phoobiological Safey of Lamps. The scope of his sandard applies o lamps and lamp sysems safey including he safey of luminaires. Hazard exposure limis (EL) Opical radiaion in general does no penerae very deeply ino biological issues. The blue ligh and infrared irradiaed from LED primarily affecs he eye and skin. Thus he poenial hazards for boh blue ligh and infrared are governed by following disinc exposure limis. a. Reinal blue ligh hazard exposure limi b. Blue ligh (small source) hazard exposure limis for he eye (cornea) c. Infrared radiaion hazard exposure limi for he eye (cornea) d. Reinal hermal hazard exposure limi e. Thermal hazard exposure limi for he skin a. Blue ligh hazard exposure limis For exposure ime 10 4 s, he maximum radiance from blue ligh shall no exceed he level defined by equaions below LB = Lλ ( λ, ) B( Δλ [ Wm sr ] (1) 300 For exposure ime > 10 4 s, he radiance is limied o a consan value: = L B( Δλ 100 [ Wm sr ] L B 300 λ where L λ is he specral radiance in Wm -2 sr -1 nm -1, B λ is he blue ligh hazard weighing funcion, λ is he bandwidh in nm and in seconds. The maximum permissible exposure duraion, max for weighed source radiance, L B ha exceeding 100 Wm -2 sr -1 wihin 10 4 s is compued as follows: 10 6 max = [ s] (3) L B (2) -1- Ver B

2 1.0E+01 Specral efficacy 1.0E E E 02 R( 1.0E 03 B( 1.0E Wavelengh (nm) Figure 1: Blue ligh weighing hazard funcion B( and hermal weighing hazard funcion R( b. Blue ligh (small source) hazard exposure limis for he eye For blue ligh source wih size less han radians, he EL derivaion for exposure ime 100 s can be simplified using specral irradiance: EB = Eλ ( λ, ) B( Δλ [ Wm ] (4) 300 For exposure ime > 100s, he radiance is limied o a consan value: E B 700 = λ 300 e B( Δλ 1 [ Wm where E λ is he specral irradiance in Wm -2 sr -1 nm -1, B λ is he blue ligh hazard weighing funcion, λ is he bandwidh in nm and in seconds. For blue ligh source weigh irradiance, E B greaer han 0.01 Wm -2 wihin 100 s, he maximum allowable exposure duraion is calculaed as followed: 100 max = [ s] (6) E B ] (5) c. Infrared radiaion hazard exposure limis for he eye The exposure of infrared radiaion wihin 1000 s is resriced o: E IR = Eλ Δλ [ Wm ] (7) 2 Ver B

3 For ime > 1000 s, he irradiance becomes independen o duraion of exposure: E IR 3000 = E Δλ 100 [ Wm 780 λ where E λ is he specral irradiance in Wm -2 sr -1 nm -1, λ given in nm and in seconds. In cold environmens, he EL for > 1000 s is increased o 400 Wm -2 a 0 C and 300 Wm -2 a 10 C. ] (8) d. Reinal hermal hazard exposure limis Apparen ligh enering he pupil is focused by he cornea and lens. Then i is projeced a back of he eye where he reina lies and ha defines he opical irradiaion induced sressed region. The angular subsense, α a a viewing disance, d can be deermined by: 1 l + w α = [ rad ] (9) d 2 wih l and w are he lengh and widh of he source respecively. Since he size of he pupil changes wih he level of luminance, he effecive angular subsense, α eff of blue ligh a a given exposure duraion is lised in he able below. Wavelengh, λ (nm) Duraion, (s) α min,eff, γ FOV (rad) α max,eff, γ FOV (rad) Blue Ligh (Addiional remarks) 0.25 < < < < Table 1: Limis of he angular subsense, α and measuremens field of view, γ FOV a differen ime range For irradiance measuremen, he angular subsense, α is defined by field of view, γ FOV given in equaion below. F α eff = γ FOV = [rad] (11) r where F is he size of he field sop and r is he disance source o deecor. The maximum EL o proec reinal from hermal injury is calculaed based on he inegraed specral radiance of he ligh source, L λ and weighing funcion, R(. The EL is a funcion of exposure ime, and angular subsense, α from he source in radians when 10 µs 10 s L R = Lλ R( Δλ [ Wm sr ] (12) α Ver B

4 For longer exposure ime, > 10 s, he EL is defined by he near infrared range (weak visual simulus, nm) and limied o: L IR = Lλ R( Δλ [ Wm sr ] (13) α 780 Cornea Ligh Source d Reina Figure 2: Angular subsense, α a a viewing disance, d. Apparen Source γ α Deecor /Aperure Sop Field Sop, F r Figure 3: Alernaive radiance measuremen echnique. e. Thermal hazard exposure limi for skin The highes EL of skin for 10s shall be limied o: EH = Eλ ( λ, ) Δλ [ Jm ] (12) where E λ is he specral irradiance in Wm -2 nm -1, λ given in nm and in seconds. For exposure longer han 10 s, EL is no provided because severe pain occurs before he skin can be damaged. 4 Ver B

5 Lamp Classificaion The following able, i summarizes he limis and poenial risk group classificaion of lamps consruced using blue ligh and infrared irradiaed LED. Risk Group Risk Group Risk Group 2 Hazard 1 (Moderae (No Hazard) (Low Risk) Risk) Reinal Blue Ligh L B < 100 L B < 10,000 L B < 4,000,000 Reinal Blue ligh, small source (α < rad) Reinal hermal Risk Group 3 (High Risk) Uni Wm -2 sr -1 E B < 1.0 E B < 1.0 E B < 400 Wm -2 L R < 28000/ α Warning when L R < 28000/ L exceeded α R < 71000/ α limis of Risk Group 2 Wm -2 sr -1 L IR < 6000/ α L IR < 6000/ α L IR < 6000/ α Wm -2 sr -1 Reinal hermal, weak visual simulus (including non-gls source) IR radiaion E IR < 100 E IR < 570 E IR < 3200 Wm -2 Table 3: Emission limis for risks group of coninuous wave lamps. The hazard value for lamps inended for general ligh service (GLS) is repored a disance which produces a luminance of 500 lux. Meanwhile, he measuremen disance for oher ligh sources is fixed a 200 mm. The recommended conrol measure for each hazard risk groups is lised in he following able. Hazard Reinal Blue Ligh ( nm) Reinal Blue ligh, small source Reinal hermal ( nm) Reinal hermal, weak visual simulus ( nm) IR radiaion ( nm) Risk Group (No Hazard) No required No required Risk Group 1 (Low Risk) No required Do no sare a operaing lamp. Use appropriae shielding for eyes Risk Group 2 (Moderae Risk) Do no sare a operaing lamp. May be harmful o he eyes. Do no sare a operaing lamp. Avoid eye exposure. Use appropriae shielding or eye proecion. Table 4: Recommended conrol measure for each hazard risk groups. Risk Group 3 (High Risk) Do no look a operaing lamp. May resul in eye injury. Do no look a operaing lamp. Avoid eye exposure. Use appropriae shielding or eye proecion. 5 Ver B

6 Analysis Majoriy of LED produce by Dominan is visible LED wih wavelengh specrum fall ino range from 400nm o 700nm. Thus by defaul here is no risk of UV or IR radiaion exposure from hese LED. The phoobiological risk of visible LED is hence confined o blue ligh hazard and reinal hermal hazard. Table below summarized he maximum brighness par number from each plaforms of LED produced in Dominan. Blue Whie Plaform Par No. Maximum Luminous Flux [lm] Risk Hazard Plaform Par No. Maximum Luminous Flux [lm] Risk Hazard SPNova NPB JSG 27.0 RG1 KNova NKW RGG PowerDomi DWB LJG 2.7 SPNova NPW RSD Domi DDB HJS 1.3 Primax NAW BSG 39.8 MiniDomi DNB DZJS 1.3 PowerDomi DWW WJG 8.9 MuliDomi D6RTB HJD 1.2 Domi DDW WJG 7.5 Spice SSB HLD 0.4 MiniDomi DNW UJG 2.7 Throughhole LED L5B N RG 1 Spice SSW HLD 1.3 Throughhole LED L5W N RG 1 Table 5: Lis of LED wih he maximum brighness par number from each plaform. Two of he highes brighness LED plaform, SPNova Blue and KNova Whie is seleced as vehicle for phoobiological measuremen and classificaion (Please refer o appendix). Besides ha, he emission from Dominan major LED group, he DomiLED Whie and he narrow beam group of Through-hole LED were also presened. These LEDs are placed a a disance, d = 200 mm and powered up wih I F = 350 ma excep ha he DomiLED/Through hole LED is driven a I F = 20 ma. The resul indicaes ha SPNova Blue is classified under Risk Group 1 (Low Risk). However, KNovaLED Whie falls ino he Group caegory. The emission from DomiLED Whie is also classified under he Group. Boh Through-hole LED of Blue and Whie are classified under Risk Group 1 (Low Risk). Summary Based on he measuremen resul, i is proven ha he wors case exposure scenario in Dominan visible LED produc range is classified under Risk Group 1 (Low Risk). However, his assessmen applies o he LED componens alone. For cusom applicaion ha involves module inegraion and secondary opics, power densiy would be one of he addiional facor o be considered ino he analysis. 6 Ver B

7 Appendix I LED Type SPNova BLUE Luminous flux 27.0 lm a I F = 350 ma, T = 25 C Peak Wavelengh 455 nm Color Blue Small Source Yes Peak Irradiance measured, E λ Wm 2 a T = 25 C (Refer o char below) Risk Group Caegories for Coninuous Wave Risk Facor Risk Group Resul Acinic UV, E S ( nm) ** Near UV, E UVA ( nm) ** Blue Ligh, L B ( nm) Risk Group 1 (Low Risk) Blue Ligh Small Source, E B ( nm) Reinal Thermal, L R ( nm) Reinal Thermal Weak Simulus, L R ( nm) ** Infrared Radiaion for eye, L IR ( nm) ** **No emission in he wavelengh range of he lised risk caegory. Irradiance Profile a 200 mm 1.5 Irradiance vs. Angle of Incidence (Disance source o deecor =200 mm) 0 90 Irradiance (Wm 2) Specrum E Angle from cenral axis ( ) Specral Radian Inensiy (Disance source o deecor = 200 mm ) 1.2E 03 Inensiy (Wsr 1nm 1) 1.0E E E E E E Wavelengh (nm) 7 Ver B

8 Appendix II LED Type KNovaLED Luminous flux lm a I F = 350 ma, T = 25 C Peak Wavelengh 455 nm Wavelengh measured nm Color Whie Small Source No Peak Irradiance measured, E λ Wm 2 a T = 25 C (Refer o char below) Risk Group Caegories for Coninuous Wave Risk Facor Risk Group Resul Acinic UV, E S ( nm) ** Near UV, E UVA ( nm) ** Blue Ligh, L B ( nm) Blue Ligh Small Source, E B ( nm) Reinal Thermal, L R ( nm) Reinal Thermal Weak Simulus, L R ( nm) ** Infrared Radiaion for eye, L IR ( nm) ** **No emission in he wavelengh range of he lised risk caegory. Irradiance Profile a 200 mm 1.5 Irradiance vs. Angle of Incidence (Disance source o deecor =200 mm) ) m (W ce n ia d 0.5 Ira 0 90 Specrum Angle from cenral axis ( ) 5.0E 04 Specral Radian Inensiy (Disance source o deecor = 200 mm ) 4.0E 04 Inensiy (Wsr 1nm 1) 3.0E E E E Wavelengh (nm) 8 Ver B

9 Appendix III LED Type DomiLED Luminous flux 7.5 lm a I F = 20 ma, T = 25 C Peak Wavelengh 445 nm Wavelengh measured nm Color Whie Small Source No Peak Irradiance measured, E λ Wm 2 a T = 25 C (Refer o char below) Risk Group Caegories for Coninuous Wave Risk Facor Risk Group Resul Acinic UV, E S ( nm) ** Near UV, E UVA ( nm) ** Blue Ligh, L B ( nm) Blue Ligh Small Source, E B ( nm) Reinal Thermal, L R ( nm) Reinal Thermal Weak Simulus, L R ( nm) ** Infrared Radiaion for eye, L IR ( nm) ** **No emission in he wavelengh range of he lised risk caegory. Irradiance Profile a 200 mm 0.10 Irradiance vs. Angle of Incidence (Disance source o deecor =200 mm) 0.08 ) 2 m 0.06 (W ce n ia 0.04 d Ira Specrum Angle from cenral axis ( ) 2.5E 05 Specral Radian Inensiy (Disance source o deecor = 200 mm ) 2.0E 05 Inensiy (Wsr 1 nm 1 ) 1.5E E E E Wavelengh (nm) 9 Ver B

10 Appendix IV LED Type Through hole LED Luminous flux 1.0 lm a I F = 20 ma, T = 25 C Peak Wavelengh 465 nm Color Blue Small Source Yes Peak Irradiance measured, E λ Wm 2 a T = 25 C (Refer o char below) Risk Group Caegories for Coninuous Wave Risk Facor Risk Group Resul Acinic UV, E S ( nm) ** Near UV, E UVA ( nm) ** Blue Ligh, L B ( nm) Risk Group 1 (Low Risk) Blue Ligh Small Source, E B ( nm) Reinal Thermal, L R ( nm) Reinal Thermal Weak Simulus, L R ( nm) ** Infrared Radiaion for eye, L IR ( nm) ** **No emission in he wavelengh range of he lised risk caegory. Irradiance Profile a 200 mm Specrum 10 Ver B

11 Appendix v LED Type Through hole LED Luminous flux 4.0 lm a I F = 20 ma, T = 25 C Peak Wavelengh 460 nm Wavelengh measured nm Color Whie Small Source Yes Peak Irradiance measured, E λ Wm 2 a T = 25 C (Refer o char below) Risk Group Caegories for Coninuous Wave Risk Facor Risk Group Resul Acinic UV, E S ( nm) ** Near UV, E UVA ( nm) ** Blue Ligh, L B ( nm) Risk Group 1 (Low Risk) Blue Ligh Small Source, E B ( nm) Reinal Thermal, L R ( nm) Reinal Thermal Weak Simulus, L R ( nm) ** Infrared Radiaion for eye, L IR ( nm) ** **No emission in he wavelengh range of he lised risk caegory. Irradiance Profile a 200 mm Specrum 11 Ver B