File talk:IEC60825 MPE J s.png

Is the graph correct?

It appears from the graph that MPE (max permissible exposure) energy is higher with higher exposure time. This does not seem correct. Should it be the reverse?67.88.183.2 21:42, 12 October 2007 (UTC)

This is not a mistake; the vertical axis is energy, not power. A given amount of energy that is harmful when administered in a short time can be harmless if spread out over a longer time. Han-Kwang (t) 21:46, 12 October 2007 (UTC)

Yes, this graph is wrong. According to the graph, a 3mW/cm^2 green laser has a 1s permissible time, however a laser with 0.000001mW/cm^2 green laser has only a .000000000001s permissible time. This graph should be fixed or preferably, removed.--dudzcom (talk) 09:09, 27 July 2009 (UTC)

This graph technically is correct, but is confusing and, I believe, pointless. It uses joules instead of watts, so you have to divide by time to get laser power. To the general user laser power vs exposure time is a much more meaningful comparison. —Preceding unsigned comment added by 71.188.141.15 (talk) 23:56, 28 August 2009 (UTC)

Qualitatively, this graph may picture a correct relationship between energy density and MPE. The longer exposure time has an influence on the effect on the target: it provides time for the heat propagation mechanism to spread out the incoming energy, thereby saving the tissue from damage, so that the energy isn't confined in space and time into a tiny spot. — Preceding unsigned comment added by 78.92.118.225 (talk) 12:53, 15 October 2011 (UTC)

This graph is not always pointless, as lasers can be operated in impulse mode, and one might want to know if an impulse with a given energy and length in time is safe or not. — Preceding unsigned comment added by 78.92.118.225 (talk) 13:00, 15 October 2011 (UTC)