100mW vs 300mW

[norty303]

Camera is my Sony Ericsson K850i 5mp

Ok, have had another response from Martin at Laserworld. They have confirmed that its ok for users to service and tune their lasers without affecting warranty. He's also agreed to take the laser back and test it. If it gives the rated power they're going to replace the switch and return it along with an output report, if it doesn't meet the minimum power then they're going to send me a new unit. So all good! (bar establishing who pays postage - but that can be resolved )

I've just come across the term 'jellybeaning' and think that this may be what i'm experiencing here. As I've packed up the laser to go back i can't test now, but am i right in thinking that if i decrease the kpps and i see an increase in brightness that i am seeing the effects of jellybeaning?

Would this be the case, even with a single point (assuming the software/dac modulates the laser in this state?)

In that case, am i stuck with it, or is there a possibility that a different unit may not suffer so badly (or worst case, more) from this effect? Is there anything that can be done from a software/hardware point of view to lessen the effects?

thanks everyone for your input so far

[gottaluvlasers]

norty-

i have always heard that perceived brightness with light (especially lasers) is usually around-
4X the power= double the brightness.

so, 300mW compared to 100mW under normal everyday circumstrances (NOT a ton of smoke, or scattering effects in the air) is NOT going to be very noticeable.

i have seen 3W next to 5W yags and the difference was *almost* non existent. would an average person notice?? probably not. would a laserist here notice?? probably.

but 300mW vs. 100mW with very similar beam characteristics IMHO is going to be VERY VERY hard to discern the differences with.

-Marc

[norty303]

I suppose it begs the question, why would anyone buy 300mW lasers if they are no better visually than 100mW?

I come from a sound related background and see people buying speaker drivers that are 1000w power handling because 'the numbers are bigger, so it must be better', where the power handling really needs to be considered alongside other factors such as sensitivity.

Is it the same with lasers, that a lot of the visible output is dependant on how well the laser handles modulation?

I ask because you've said that there won't be much difference, whereas someone earlier said it should quite noticeable.

I have some 250w MSD250/2 powered scans and also some HMI575 scans and the 575's just blow the 250's away from a visual point of view.

[Pangolin]

I'm still curious 'why' the metered average signal was 0.17vdc/0.34vac on a single point in a frame, but as you've said you're not revealing more, i'll not press you! (not that it would do any good anyway!)

I just don't even want to discuss measuring color signals with a meter, because it just isn't the right thing to do. It's like measuring water temperature with your finger. MAYBE you get some kind of relative indication, but that's all you get. If you want to measure a color signal, you need a scope.

Could this effect be anything to do with why both my lasers appear to be the same brightness?

I don't want to seem like an ass, but I guess you have to re-read what I wrote. Different lasers will react differently to differing modulation waveforms. So, if I have to use only one word to answer your question, that word would be "maybe".

Would 3 1.5v AA batteries (4.5v) be ok to test the modulation line?

Unfortunately, this is another "maybe". It depends on the laser diode driver manufacturer. Spec in this industry is "full output with 5 volts input". But a safer way to design a laser diode driver would be to deliver full output before 5.0 volts. How much before? Well, it depends on the driver. I would rather see you get closer to 5V somehow. Actually, a PC power supply has a great 5 volt source which can be found on any red wire on a disk drive connector.

Could low average voltage on some frames/patterns upset TTL lasers, if they happen to fall on or around the switching point?

Well, it wouldn't be low average voltage, but rather low peak voltage. And again, unfortunately this depends on the design of the laser diode driver manufacturer.

As an aside, I must say I haven't seen even so much as a single laser diode driver in this industry that I liked...

Would there be any practical use for having a software feature that provided a binary type (TTL) output over the analogue output? Again, i don't even pretend to know about these things but i'm trying to apply the logic that i do know, so any clarification is useful.

LiveQ does provide some adjustability for the color setup. LAStudio (if memory serves) provides far more.

Best regards,

William Benner

[norty303]

Actually, a PC power supply has a great 5 volt source which can be found on any red wire on a disk drive connector.

Ooo, hadn't thought about that, and I do have a handily wide open PC right on my workbench!

[buffo]

I've just come across the term 'jellybeaning' and think that this may be what i'm experiencing here. As I've packed up the laser to go back i can't test now, but am i right in thinking that if i decrease the kpps and i see an increase in brightness that i am seeing the effects of jellybeaning?

It appears this part of your question was lost in the replies. But to answer your question, yes, decreasing the Kpps *should* reduce the jellybeaning. I'd ramp it down to around 12K or so and see what you get.

Would this be the case, even with a single point (assuming the software/dac modulates the laser in this state?)

Jellybeaning is *worse* when you have only a few lit points in the frame. The problem is that it takes the laser a certain amount of time to ramp up to full power. If the blanking signal is only "on" for a very short time, then the laser doesn't have time to get up to full power before it gets shut off again. So you'll notice it more when you have a few "points" of light in a frame.

If you have a longer line segment in the frame, then the laser will be on long enough that it will be able to get all the way up to full power, and at best you might notice that one end of the line segment appears a little dim. (This is really easy to tell with a white line, because the tail of the line will be red... That's because direct injection red diodes don't suffer from jellybeaning like DPSS blue and green lasers do.)

In that case, am i stuck with it, or is there a possibility that a different unit may not suffer so badly (or worst case, more) from this effect? Is there anything that can be done from a software/hardware point of view to lessen the effects?

As a general rule, you're stuck with it. If replacing the laser with another brand is an option, then you can shop around and try to find a laser that exhibits less jellybeaning.

Another fix that will help with the "red tail" problem (for RGB rigs) mentioned above is to put a delay on the blanking line feeding your red laser. Basically you want to slow the red laser down to match the delayed response speed of the other two lasers in your projector (assuming an RGB rig).

But if you only have a single color laser, then you have to live with the jellybeaning... You can try to play with the color speed adjustment on your controller, but it won't have a large effect on the problem.

Adam

[aijii]

Umm, in our experience, our 300-350mw green lasers look LOTS brighter than our 150mw greens.

If you can't tell the difference obviously, with them sitting next to each other, then either the 100mw is overpower, or the 300mw is under power.

[mliptack]

Or a mixture of the both

[norty303]

See now my seller review for the full story....