Originally Posted by Low Tech
Originally Posted by Augerhandle
Coherent light is not the same as focused light. While LEDs can be focused, they do not emit coherent light, nor does the sun. Only lasers emit coherent light. I'm really sorry that you don't understand the difference, but I am satisfied that most everyone else does. Have a nice day.
Really??? LED devices have been producing coherent light commercially since the 70's. IR remotes for example. 900nm is a very narrow wave length compared to visible light. As of recent, LED tech has been producing very narrow wave length visible light spectrum without filtering.
Laser Diodes and LEDs are semiconductor devices, but LEDs are not lasers, just as LEDs are not transistors. The IR blaster in your remote is not a laser, it is just an LED.
...Again lasers is a broad technology, and you should understand a narrowly focused beam is the basics of a laser, whether it is emitted by charged gas or through solid state devices. The type of light does not mean it is a laser.
Focusing does not make light lase. A laser lases well before it is focused by any lens. The type of light is what DEFINES a laser, and that type is coherent light. Laser light is coherent, collimated and monochromatic. LED light is not.
Your class 4 warning label is only needed if the component to the device is not safe when operating disassembled. LED components that are not manufactured as laser diodes, are safe to operate disassembled... So no warning label is needed even though the light intensity is the same or even higher than a similar laser component.
LEDs have no warning because they won't burn flesh and one's retina.
Class 4 lasers will.
Like I said before the Mits lasers are just laser diodes, which are a LED device that have a focusing lens built in.
No, what you said before was that lasers weren't used in Mits TV at all
Originally Posted by Low Tech
...There is no way a real laser would be used in a RPTV...
You said they were just LEDs being marketed as lasers. (a laser diode lases well before it gets to any focusing lens. As shall be shown, it is not the same as an LED with a focusing lens)
From your own link
the LED structure is placed in a tiny reflective cup so that the light from the active layer will be reflected toward the desired exit direction.
As shown above, LEDs emit incoherent
light that is focused like a flashlight.
Laser action (with the resultant monochromatic and coherent
light output) can be achieved in a p-n junction formed by two doped gallium arsenide layers. The two ends of the structure need to be optically flat and parallel with one end mirrored and one partially reflective
. The length of the junction must be precisely related to the wavelength of the light to be emitted. The junction is forward biased and the recombination process produces light as in the LED (incoherent). [The difference being that] Above a certain current threshold the photons moving parallel to the junction can stimulate emission and initiate laser action
LEDs emit incoherent
light that is focused like a flashlight. Lasers (including laser diodes) are built to emit coherent
light. As shown, this happens before any lenses or focusing reflectors come into play. That is the difference. The LEDs in your remotes and your samsung DLP can't do that, because they are LEDs, not laser diodes. They cannot lase.
You may not have an electronic background, so here's a link you may find easier to read. http://en.wikipedia.org/wiki/Laser_diode
A laser diode is a laser whose active medium is a semiconductor similar to that found in a light-emitting diode.
Notice the words "a semiconductor similar to". "Similar" is not "equal to". a regular diode is similar to an LED, and it emits no light at all. A transistor is similar, (with an additional P or N layer), and it emits no light either.
Spontaneous emission gives the laser diode below lasing threshold similar properties to an LED. Spontaneous emission is necessary to initiate laser oscillation
Again, those pesky words "similar to", and then ONLY "similar" when below lasing threshold
, (LEDs can't lase, because they're designed differently).
Here's another basic primer on laser diodes for you. http://www.repairfaq.org/sam/laserdio.htm#diocss2
Edited by Augerhandle - 8/1/12 at 5:31pm
While a laser diode is a true laser and not just a glorified (and expensive) LED, there are major difference compared to a gas or solid state laser...
...Yes indeed, a diode laser is a true laser.