Ahhh i see. Yeah that makes sense.

 

hi
thoday i taken one of my lasers apart, and there was a lenz and a micro led.. the amazing part is that the led bright is too low without the lenzand it can not travel even 30cm so i tried the lenz with a normal Light-emitting Diode(led) but the lenz could not focouss it :?:
does anyone know if the laser pointer distance(more than 700m) is because of its lenz ONLY? if so then i should be able to use from a lamp or led instead of the laser lamp?
what is the story??? :idea:

 

It's not just an LED, it's a Laser Diode, these produce coherent light, which the lens can then focus - a normal LED (or lamp) produces in-coherent light.

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its monochromatic and in phase, if i remember right.

 

i can not understand you!

what "coherent light" means here?

do you think a common led can not be so focused to go very much destance?...

 

Do a Google search on "coherent light".

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Ron

 

"Coherent" means there is only 1 principle wavelength produced, thanks to the quantum properties of the junction material. That's true for all LEDs exept for white, white are blue LEDs with a yellow-emitting phosphor.

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This is why I told him to do a Google search.
While it's true that LEDs produce only one principle wavelength, that is not the definition of coherence. Coherence means all photons are in phase. Lasers produce coherent light, LEDs don't.

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Ron

 

I wonder if the "lens" of a laser diode is part of its internal reflecting mechanism that causes it to oscillate only at the single frequency where all waves are in-phase.

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I don't think so. Here is a good article that explains the semiconductor laser structure.
I actually don't know squat about laser diodes.

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Ron

 

If you connect a variable power supply to a cheap red laser pointer, and gradually increase the voltage from 3 volts, the output power will increase to a peak, then fall as voltage is increased further. It is quite safe from the laser's point of view to run at this peak, but watch the power dissipation in the series resistor. So far, best results are 7mW from a <1mW laser pointer.
While on the subject, if you look at a spot of laser light, you will see a grainy pattern, which will be in focus. If you put a lens over your eye, so that you can't see anything else, the grainy pattern will still be in focus. Only coherent light will do this.