File talk:IEC60825 MPE J s.png

Is the graph correct?[edit]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]