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Thread: Output Comparison Gas Lasers Vs Diode Aser(dpss)

  1. #1
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    Smile Output Comparison Gas Lasers Vs Diode Aser(dpss)

    I have been seeing all diode lasers(DPSS) with laser companies these days.

    So was inquisitive to know,the comparison of output brightness of gas lasers and the diode lasers.

    I mean for example would a 5 watt argon-krypton or He-Ne laser(single green color) be as bright as a 5 watt diode laser.
    OR Can we say approximately how many times more bright a diode laser would be compared to gas laser if both of them are labeled to be of same output wattage.

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    Lightbulb

    It is all based on your eye. 100mW of 532nm is going to have the same brightness no matter what created it, gas or diode, or what ever you get to make it. It is also going to look brighter to your eye that 100mW of 635nm, no matter what created, gas of diode... Just because your eye is more sensitive to green wavelengths, it appears brighter to you than red and blue of the same power.

    So yes, a diode if 100mW, same wavelength, will look as bright as a gas laser, same wavelength.

    Some may argue what can make what will make a little difference. HeNe 632 will be a lil brighter than the 635 diode... what is is 647 krypton will be a lil brighter than 650 diode... 532 diode will look a lil brighter than... 514 argon.

    I say make a small gas projector with HeNe for red, yellow, high green, and argon for low green blue and deep blue... use all the color channels you can squeeze out of your DAC.

    I'd like to see a 5W Green HeNe.
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    What about the difference in beam quality and diameter? A finer beam might have the same total output power, but won't it look brighter because it is more concentrated on a spot?

    James.

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    Yes, but for beamshows, that's exactly what you don't want. A lager more divergent beam looks far more attractive

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    Quote Originally Posted by elvis View Post
    I have been seeing all diode lasers(DPSS) with laser companies these days.

    So was inquisitive to know,the comparison of output brightness of gas lasers and the diode lasers.

    I mean for example would a 5 watt argon-krypton or He-Ne laser(single green color) be as bright as a 5 watt diode laser.
    OR Can we say approximately how many times more bright a diode laser would be compared to gas laser if both of them are labeled to be of same output wattage.
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    5watt AR/KR is full of color lines. You need only 3 maximum 6 lines rest is a waist. So 5W DPSS RGB will be brighter then 5W AR/KR. Will a single line of green out of AR/KR will be brighter then 5W green DPSS?. No not even slightly. 5W green DPSS will be about 3 times brighter.
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    Quote Originally Posted by Dr Laser View Post
    5watt AR/KR is full of color lines. You need only 3 maximum 6 lines rest is a waist. So 5W DPSS RGB will be brighter then 5W AR/KR. Will a single line of green out of AR/KR will be brighter then 5W green DPSS?. No not even slightly. 5W green DPSS will be about 3 times brighter.
    Am I correct in the assuption that the AR/KR's power of say 5W is spread across it's total output spectrum, some colours having a larger wedge of the total 5W than others and a 5W diode 532 DPSS will have it's full output power at one colour only thus a lot more powerful at one colour (532)?
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    Quote Originally Posted by smogthemog View Post
    Am I correct in the assuption that the AR/KR's power of say 5W is spread across it's total output spectrum, some colours having a larger wedge of the total 5W than others and a 5W diode 532 DPSS will have it's full output power at one colour only thus a lot more powerful at one colour (532)?
    Yes it's true that a 5 watt argon laser will have it's power divided among several different lasing lines. (Usually between 5 and 8 lines.) However, you are also correct in that the power is not evenly distributed among those lines. This makes the comparison between an Argon laser and a DPSS rig more complicated.

    488 nm and 514.5 nm are the two main argon lines. Together these two lines will account for around 70% of the total output of a multi-line argon laser. The next most powerful lines will be the 476.5 nm and 496.5 nm lines; together they will account for another 15% of the total power. So with just 4 lines you've already accounted for over 85% of the total power.

    See where this is headed? By the time you get down to the next three most powerful lines (the 501.7 nm, 457.9 nm, and 472.7 nm lines) you've accounted for another 10% of the output power. You're down to the last few percent of available power now, and we've only listed 7 lines.

    So you see, while the power is spread out among various lines, it's not nearly as dramatic an effect as you might think.

    Bottom line - yes it's true that a 5 watt green DPSS laser will output all 5 watts on a single line at 532 nm. By comparison, a 5 watt multi-line argon will only make about 2 watts of green at 514.5 nm However, that argon is also making around 1.7 watts of blue at 488nm, not to mention another half-watt + of deeper blue at 457.9 nm and 476.5 nm. So it's not really fair to compare it to a 5 watt DPSS green.

    A better comparison would be to put a 500 mw single-line green argon laser (lasing at 514.5 nm) against a 500 mw DPSS green laser. In this case, both lasers are making the same power (500 mw), so the only difference in apparent brightness will be due to the human eye's non-linear response to color. And in this case, the DPSS laser will appear brighter in a room with normal light levels, while the Argon laser will appear brighter in a dark room.

    This is because the color sensitivity peak for our eyes is centered at around 555 nm when there is a lot of light entering the eye, but the peak shifts towards the blue spectrum when our eyes become dark-adapted. (So-called scotopic vision) In a dark room, the peak is closer to 510 nm, which is very close to the main green line for Argon.
    Quote Originally Posted by Dr Laser
    So 5W DPSS RGB will be brighter then 5W AR/KR.
    You're splitting hairs here. Technically you do get more lines out of a mixed gas laser, so the power is spread out among more lines, yes. However, with an 8 channel PCAOM you'll be able to modulate the most powerful lines, assuring that you'll be able to use well over 90% of the total output of the laser. (Ignoring losses through the PCAOM.) Thus the difference is *not* that significant. On a 5 watt RGB projector, you're not going to notice a 5-10% difference in power.
    Will a single line of green out of AR/KR will be brighter then 5W green DPSS?. No not even slightly. 5W green DPSS will be about 3 times brighter.
    You're comparing apples to oranges. The 5 watt DPSS green only outputs green, while the mixed gas laser is making white.

    A better comparison would be a 5 watt mixed gas laser (running wide open on all lines) verses a color-balanced 5 watt solid state RGB projector running wide open. And in that case, at that power level you'd never be able to tell the difference in brightness between the two white beams.

    Adam

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    Buffo wrote:

    So you see, while the power is spread out among various lines, it's not nearly as dramatic an effect as you might think.

    end quote-----------------------------

    Buffo is right, there are adavntages to having more then 3 lines.

    You guys are forgtting one other thing, for example, adding just one line, ie going from RGB to RGBV (violet) or RGBY( yellow) can add as much as 40% more color variation in your beams and images.

    Your gonna have a hard time creating browns, gold, silver, and some oranges with just RGB!

    for example, blue + yellow in the right ratio is WHITE to the eye

    Getting a CIE chart and drawing a triangle from 3 RGB points to define your spectrum only tells part of the story, as the eye response VS wavelength is very nonlinear and changes with enviromental brightness. We didnt become top predator with just basic color vision using RGB pixels like a TV camera.

    Steve

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    When I saw rMud's Argon with lots of high end energy in the deep blue and violet lines, the first thing I noticed was how spectacular they looked and that you just can't get that effect any other way. No mixture of red and blue will ever look like true violet. If you've never seen it, it is hard to describe. It's super bright and deep and dark at the same time! It's just intense.

    James.
    Last edited by James Lehman; 06-30-2008 at 21:13.

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