Pulsed lasers

It seems like the majority of the laser pointers are used as a continuous wave (CW), but for the normal non-laser show laser pointers wouldn´t it be a better choice to run the laser diodes as pulsed wave, since
#1 Would allow to extract more power (actually double) from the same laser diodes, raising the appeal of the laser.
#2 Human eye perceptivity of frequency cannot capture a frequency of higher than 60 Hz (not sure about the real Hz data), so there is quite no difference in visual appealing by running Cw or >60hz pulsed
#3 Diodes would run cooler


Do i need a special driver for running diodes at pulse wave, or do i need to add something more to the CW drivers for them to run at pulse.

So with pulsed lasers i can get more power without compromise too much the beam visual characteristic

Heh... I was thinking about the same thing earlier today and I would be interested as well!

#2 Human eye perceptivity of frequency cannot capture a frequency of higher than 60 Hz (not sure about the real Hz data), so there is quite no difference in visual appealing by running Cw or >60hz pulsed

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But it will look like a dotted line when you move it fast , even though if you look at the spot you won't notice any difference.And I thought the human eye works at 24FPS. :-/

As for the driver , not many bothered in building a pulsed driver.I would imagine you would use a timer chip like the 555. :-/ And the power increase is only an illusion, you'll get a higher peak , but since the diode is also shutting off, the average will be the same or even lower than CW.

Anyway, it's for out electronics experts here to answer how we would go about building a pulsed driver.

i thought it was 24fps also....think i read that in a gammer mag some time ago

f22warzone said:

i thought it was 24fps also....think i read that in a gammer mag some time ago

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Yea but I think it makes some kind of a difference with motion. I mean You can clearly tell if your monitor is on 50Hz or 120Hz when moving a window around.Besides, all the shooter gamers b!tch about how they can't play at 50fps and they need 100. :-/

IIRC, television and movies are shown at 24fps, while the human eye can only detect up to 30fps... All that I'm truly certain of is that I once played Marathon: Durandal at 60fps and it gave me a headache.

I don't play video games or watch TV so I couldn't care less what fps my computer/TV works in.
As long as it works for my research projects, photoshop, movies and music, I'll be fine .

Would a pulsed laser have decreased burning ability?
I would think so considering it is off half the time it's operating...

As a pointer I think It would be cool to have a pulsed laser. Those Aquarius lasers make some cool effects with the spinning mirror. The dashed line looks pretty cool too, in my opinion at least.

Well , I would think it would burn better for the following reason:
A 200mW CW laser constantly delivers 200mW , that is, a total of 200mJ every second and a maximum of 200mW peak.
A 200mW pulsed laser , let's say 50Hz, with a pulse duration of 1/100th of a second(that would give it half on , half off) would still deliver 200mJ every second, but the maximum peak would be 400mW.So instead of 200mW constant , it would be 400mW for 1/100th of a sec then nothing for the next, and so on.
I would think this could burn better because maybe the material can disipate heat created from 200mW with 0 damage, but 400mW would do faster damage.The material would have time too cool, but not "heal" since damage has already been done.

So if you think about it, it's like hitting a 2x4 really hard compared to putting a small weight over the 2x4 and leaving it there for a long time.The really hard hit has a chance to break it, or at least soften it for the next hit, while the weight simply doesn't do anything even if you leave it for 1000 years. :-/


Or it could also burn worse, and I guess it depends on how crucial the power difference is to cause damage to the material within the pulse duration.

Does anyone know were I could get one of the old style CNI pulsed greenies?

What if you pulsed a 200mW so that it was only on for 1/100 of the time? Would the pulses be 100 times the power? That would look pretty cool, like a laser gun, and if it was really producing 20 watts per pulse, that would be insane.

-Mark

It would probably die, and produce 20W of heat in the process. Besides, you would need a rather large capacitor to do that. :

Switch said:

It would probably die, and produce 20W of heat in the process. Besides, you would need a rather large capacitor to do that. :

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It would probably 'instasuffer' COD... Thats what I think...

ArRaY

COD, hah.Big flying sparks more like it! You could calculate what kind of massive cap you would need to discharge for a theoretical 20W for 1/100th of a second taking into account the laser's normal efficiency.But it's just not gonna happen.

Switch said:

COD, hah.Big flying sparks more like it!   You could calculate what kind of massive cap you would need to discharge for a theoretical 20W for 1/100th of a second taking into account the laser's normal efficiency.But it's just not gonna happen.

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You´re right. The little wires would be likely to be atomised, if COD does not appear fast enough.

its all about the RMS of the pulse width.

at 100mw and 24hz if your diode is on for 0.0208 seconds and off for 0.0208 seconds it will look like its 50mw RMS (half the brightness).

Take it from me, i work with nano second pulsed Excimer lasers. the energy density of an Excimer is upwards of a few kilowatts/cm^2 peak power (when photons are being emitted). we run these at over 100hz and they really dont look very bright (if hitting white paper or a highlighter) because of the such short on-time.

we use energy meters to measure the output power of the Excimers and get an RMS of 150 milijoule/sec which is about the same as my blu-ray measures.

so a pulsed laser will not look much brighter than a CW unless your pulse width has a long on time, but the intensity of the pulse is much greater and can inturn do more damage to your eye...

I have a pulsed YAG laser, and like an excimer, the beam is of course invisible. For burning, a pulsed laser (well, this is true of a laser like mine, where you can only fire it once every 30 seconds at the most) is about the worst thing you can use (other than a very low-powered CW laser, of course).

A huge amount of energy is dumped into each pulse, but the duration is so brief that there really is no chance for any heat to be deposited. A hit from my YAG is barely enough to light a match (and only when focused, otherwise it simply ablates some of the material off the match head). However, if you had a laser with a very rapid pulse rate, then the effect on a target would be more akin to that of a CW laser. There were a couple of pulsed YAGs at the laser shop I worked at that could be run at 200 pulses per second. At that rate, they could be used to cut metal just like the CW CO2 lasers.