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07102012, 09:03 PM  #17  
 
Class 3R Laser Join Date: Jun 2011
Posts: 2,111
Rep Power: 520 
That experiment sounds iffy: 8ft after 5.2km is less than 0.5mRad. Very unlikely for a regular green pointer. An 8ft dot of 5mW power should be very, very dim. Unfortunately I don't have a focusable one here to test but I seriously doubt it'd be painful to look at. It's possible they measured wrong and had a way overspec laser, though.
__________________ 405nm: NewWish (29.1mW avg5mW rtd)  Dilda (81.5mW avg200mW rtd)  501B by Blord (633mW pk) low 445nm: C6 from Survival Lasers (1351mW pk1289mW avg1100mW rtd) high 450nm: NewWish (12.6mW pk5mW rtd)  Dominator by Blord (3010mW pk2779mW avg during 5min) 462nm: 501B by Atomic (1507mW avg) 473nm: BWB10OEM labby by CNI (10mW rtd) 520nm: MXDL pen by DTR (31.6mW pk28.8mW avg) 532nm: NewWish (28.6mW pk26.8mW avg10mW rtd)  Dapper (30.3mW pk)  Classic (120.0mW pk103.1mW avg100mW rtd)  "The Green Box" by Atomic (176.7mW pk140.0mW avg) 589nm: Spartan from Dragon Lasers (58.4mW pk37mW avg50mW rtd) 632.8nm: HeNe pointer by Atomic (0.68mW rtd) 635nm: NewWish (4.6mW avg5mW rtd) 638nm: Classic from Lazerer (409.3mW pk389.4mW avg415mW rtd) 650nm: NewWish (10.6mW pk5mW rtd)  Dilda (216.3mW avg200mW rtd) 685nm: laserinabox by Atomic (30.4mW pk29.3mW avg)  501B by Atomic (32.4mW avg) 780nm: module (2.7mW avg5mW rtd) 808nm: Classic modded from a 532nm (162mW avg) 850nm: module (8.8mW avg7mW rtd) 980nm: NewWish (81mW pk5mW rtd)  2nd line around 490nm 5W Ophir LPM HV: Flyback, Plasma Speaker, The Arcsynth and SSTC Last edited by Atomicrox; 07102012 at 09:03 PM.  
07112012, 12:20 AM  #18  
 
Class 1M Laser Join Date: Feb 2011 Location: arizona
Posts: 191
Rep Power: 6 
And if you look at the picture with the beam on the ground..that was taken in daylight how can a 5Mw laser do that? And the the other pictures seem to be taken at nighttime.
__________________ My lasers 2. 5mw 405nm pen 1. Arctic spyder 3 1. 1w Spartan 1. 100mw hulk 532nm 1. 250mw hulk 532nm 1. 30mw 532nm pen 2. 250mw 650nm olike cute 1. 5mw 650nm radio shack. Pen 2. 5mw 635nm olike pens Amazon 3 pack (red,green,violet) over spec!!  
07112012, 02:18 AM  #19  
 
Class 3R Laser Join Date: Jun 2007
Posts: 1,204
Rep Power: 340   
07112012, 03:02 AM  #20  
 
Class 3R Laser Join Date: Jun 2011
Posts: 2,111
Rep Power: 520 
More info: http://safety.uchicago.edu/files/Las...lculations.pdf I'll make some more calculations tomorrow to have a better idea of the danger of diffuse reflections but at a first glance it seems to follow an inverse square law.
__________________ 405nm: NewWish (29.1mW avg5mW rtd)  Dilda (81.5mW avg200mW rtd)  501B by Blord (633mW pk) low 445nm: C6 from Survival Lasers (1351mW pk1289mW avg1100mW rtd) high 450nm: NewWish (12.6mW pk5mW rtd)  Dominator by Blord (3010mW pk2779mW avg during 5min) 462nm: 501B by Atomic (1507mW avg) 473nm: BWB10OEM labby by CNI (10mW rtd) 520nm: MXDL pen by DTR (31.6mW pk28.8mW avg) 532nm: NewWish (28.6mW pk26.8mW avg10mW rtd)  Dapper (30.3mW pk)  Classic (120.0mW pk103.1mW avg100mW rtd)  "The Green Box" by Atomic (176.7mW pk140.0mW avg) 589nm: Spartan from Dragon Lasers (58.4mW pk37mW avg50mW rtd) 632.8nm: HeNe pointer by Atomic (0.68mW rtd) 635nm: NewWish (4.6mW avg5mW rtd) 638nm: Classic from Lazerer (409.3mW pk389.4mW avg415mW rtd) 650nm: NewWish (10.6mW pk5mW rtd)  Dilda (216.3mW avg200mW rtd) 685nm: laserinabox by Atomic (30.4mW pk29.3mW avg)  501B by Atomic (32.4mW avg) 780nm: module (2.7mW avg5mW rtd) 808nm: Classic modded from a 532nm (162mW avg) 850nm: module (8.8mW avg7mW rtd) 980nm: NewWish (81mW pk5mW rtd)  2nd line around 490nm 5W Ophir LPM HV: Flyback, Plasma Speaker, The Arcsynth and SSTC  
07112012, 01:12 PM  #21  
 
Class 1M Laser Join Date: Feb 2011 Location: arizona
Posts: 191
Rep Power: 6  Looks likes blue sky though the trees to me but I could be wrong.
__________________ My lasers 2. 5mw 405nm pen 1. Arctic spyder 3 1. 1w Spartan 1. 100mw hulk 532nm 1. 250mw hulk 532nm 1. 30mw 532nm pen 2. 250mw 650nm olike cute 1. 5mw 650nm radio shack. Pen 2. 5mw 635nm olike pens Amazon 3 pack (red,green,violet) over spec!!  
07152012, 03:04 PM  #22  
 
Class 3R Laser Join Date: Jun 2011
Posts: 2,111
Rep Power: 520 
Sorry for the late reply, didn't have time to read the whole PDF till today. The safe distance formula on the PDF is slightly different (and gives different results) than other NOHD formulas out there. I'm not sure how much we can actually trust those formulas :/ It also has an interesting formula to compute "The flux of energy through a point at a given distance and angle from a diffusely reflecting surface": H = Pλ*Q*cos(Φv) / π*r^2 where Pλ is the reflectance at the wavelength in question, Q is the energy of the incident beam, Φv is the angle of observation with respect to the normal, and r is the distance from the point of reflection to the point of observation. For safety calculations this equation can be greatly simplified by assuming Pλ = cos Φv = 1. According to their example it's safe to view a diffuse reflection of a 2W visible laser from 40cm away for the duration of the blink reflex (0.25s). If we do the calculation in W using the MPE for continuous exposure (1mW/cm^2) the minimum safe distance for a visible 5W laser would be 40cm. If this is true looking at the diffuse eflection of even the highest power visible lasers from at least that distance should be safe. I'd take the calculation with a grain of salt because the equation is for energy (J), not power (W). It would make sense to assume it holds for power but since this is a safety calculation it would be better to confirm. Also beware that most surfaces also have at least a bit of specular reflection. Edit: that also means using lasers to burn stuff from short distances without goggles isn't safe even if the surface is completely matte.
__________________ 405nm: NewWish (29.1mW avg5mW rtd)  Dilda (81.5mW avg200mW rtd)  501B by Blord (633mW pk) low 445nm: C6 from Survival Lasers (1351mW pk1289mW avg1100mW rtd) high 450nm: NewWish (12.6mW pk5mW rtd)  Dominator by Blord (3010mW pk2779mW avg during 5min) 462nm: 501B by Atomic (1507mW avg) 473nm: BWB10OEM labby by CNI (10mW rtd) 520nm: MXDL pen by DTR (31.6mW pk28.8mW avg) 532nm: NewWish (28.6mW pk26.8mW avg10mW rtd)  Dapper (30.3mW pk)  Classic (120.0mW pk103.1mW avg100mW rtd)  "The Green Box" by Atomic (176.7mW pk140.0mW avg) 589nm: Spartan from Dragon Lasers (58.4mW pk37mW avg50mW rtd) 632.8nm: HeNe pointer by Atomic (0.68mW rtd) 635nm: NewWish (4.6mW avg5mW rtd) 638nm: Classic from Lazerer (409.3mW pk389.4mW avg415mW rtd) 650nm: NewWish (10.6mW pk5mW rtd)  Dilda (216.3mW avg200mW rtd) 685nm: laserinabox by Atomic (30.4mW pk29.3mW avg)  501B by Atomic (32.4mW avg) 780nm: module (2.7mW avg5mW rtd) 808nm: Classic modded from a 532nm (162mW avg) 850nm: module (8.8mW avg7mW rtd) 980nm: NewWish (81mW pk5mW rtd)  2nd line around 490nm 5W Ophir LPM HV: Flyback, Plasma Speaker, The Arcsynth and SSTC Last edited by Atomicrox; 07152012 at 03:09 PM.  
07182012, 03:08 AM  #23  
 
Class 2M Laser Join Date: May 2012 Location: Caledonia, WI
Posts: 587
Rep Power: 54 
Matt.
 
07232012, 09:25 PM  #24  
 
Junior Member Join Date: Jun 2012
Posts: 15
Rep Power: 0 
This is a great chart. Thanks. I thought buying a blue laser. But according to this chart, there is no point if the purpose is to point on distant objects.  
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