nanometers (was: AW: Uranus phaser)

[Magnus Danielson]

>>>>> "HJ" == Haible Juergen <Juergen.Haible at nbgm.siemens.de> writes:

Hi!

In my habbit of talking about subjects I know too little of...

 >>> - Typical CdS LDR's are most sensitive to green light, just like
 HJ> the
 >>> human eye. Using a green LED, especially an ultra-bright green
 HJ> LED,
 >>> will make the current used to drive the LED much lower. 
 >>> 
 >> ??
 >> I have seen sensitivity measurement diagrams that show two peaks of
 >> equal hights for CdS:  at green 540nm AND orange/red 640nm. 

 HJ> I think CdS is only one of several materials for LDRs.
 HJ> There's CdSe (sp?), and probably mixtures of both.
 HJ> I have no idea what these surplus parts are made of.

There are many semiconductors with diffrent properties to use for this
purpose, and surely is CdS and CdSe just a few of them.

 >> So these
 >> very bright orange/red diodes should be sufficient, they are much
 >> brighter then any green led I've ever seen, indeed one should not
 >> directly look into the light source, danger of eye damage !

 HJ> Is this really true? I think that even if there would be danger
 HJ> when you look at it with an optical device (telescope ...),
 HJ> it would have to be labelled so. (At least in Germany)
 HJ> Just wondering.

Eh... I can understand that my 35 mW laserdiode might hurt my eyes
since the light is in phase and all that, but a 35 mW LED? No...
In that case would a glimp at the clock in the morning be disasterous.

I think it is a matter of confusing laser diodes and normal diodes.

Cheers,
Magnus