Pangolin ? laser not perform at maximum

[mixedgas]

...I don't know about the FB3, but on the QM32 and QM2000, Pangolin's hardware "steals" a little time in each frame to , what I can only assume, as talk to the host PC, transfer point data, perform housekeeping, do math and so forth. Only Pangolin knows exactly what the hardware is doing at this time, but the time occurs before point zero and is blanked. So the average illumination energy is now down a few percent. No problem with most systems, and certainly no problem with gas lasers. But on a few solid state lasers, this blanked period wrecks havoc with thermal stability, people see the falloff and complain.

It is effectively a small amount of PWM modulation, and a few systems seem loose say 15% of delivered power instead of a few percent. The way the eye functions, you'd never know there is a loss unless you suspend blanking or use a power meter, unless you have one of the lasers that suffer from sensitivity to blanking. Pangolin seems to have patches for some affected users.

... For 99% of users, they never notice it, or it is not a problem. There seems to be unwritten rule about not talking about it. At last SELEM Bill had stated that it will no longer bet a issue on newer version of Quickshow, but "pending patent" he would not let me, or anyone else, look at the new, improved, waveforms on a scope.

There are hardware alternatives to Bill's method, but they drive cost up, and image manipulation flexibility down, and you may have to add a second processor etc.

There are hardware cures, changing drivers, color correction boards, boosting the signal to 5.5 volts, using AO blanking, switching lasers,and so forth. The problem is there are so many different models of green laser out there, and no standards for blanking response times.

I'm not surprised there is other controller hardware that uses the same method, it is a very practical method of doing things because it smooths out and reduces uneven software delays that can enhance flickering or affect show timing.

Steve

[badger1666]

@ marc i no longer have the fb3 i gave up with it
not that its not a great peice of hardware.
even when i did use it with it set to 100% i had to layer beams to get anthing sensible
out of it ,and one of my lasers does not like pangos pulse blanking
i fully understand how lasers and blanking affects the power output of lasers scanning
i know where the problem is it just pango likes to spread the beam power out backwards
in that i mean i want to draw beams to get most power out and for every beam i add to the projection all the others will get dimmer the more you add,
but with pangolin its the other way around ,just for example draw one fan it comes out at lets say 20% power ,draw another under neath it and it will give you 20% more and so on,
which is why you end up layering the beams to get a reasonable powered beam
and so there method is just not what i want ,i know bill has his reasons for the way he does it, safety scanners, and all that, its great if you got a multi watt projector thing dont seem so bad, but when you only have a 1w projector and you display an animation
pause it disconnect the scanners and take a power reading and hardly see a 100mw
you kind of think why did i spend all that money
i am just saying it would be nice to see a software switch so you can have it bills way
where the more beams you add they stay the same brightness as you add more
or the other way i mentioned where you go from full power and beams getting dimmer
as you add more. a lot of hobby guys only want to do simple beam shows so it would suit them better ,but that said i do like the software it its great to use ,just dont work right for me
just my 2cent worth

sorry to rant on but i spent to much money finding somthing that works for me

[Pangolin]

Hi all,

There are a few things that bother me about this kind of topic, and those thing have nothing to do with our software.

The first problem is that people tend to measure color signals with a meter instead of a scope. A meter may show you the signal level in a variety of ways, depending on the type of meter you have. For example, if you have something called a "True RMS" meter, it will show you a voltage level that is different from that if your meter doesn't say the words "True RMS". And even with a True RMS meter, it may not show the real and true RMS, depending on something called "Crest Factor". The ******ONLY****** way to measure a color signal is by using an oscilloscope.

The second problem -- and the one that bothers me personally the most -- is one of understanding. People simply do not understand the relationship between output power from a laser and visibility to the eye. Stated briefly, that relationship can be *roughly* described by a formula like this: Laser Power Required = Visibility Desired (raised to the 2.5 power) / 1000. It means that in order for your eye to perceive the light as being "half as bright", you only need around 17% laser power.

When we examine this relationship in reverse, it means that even if QS was really and truly putting out "only" 4 volts (80% of 5 volts), your eye would perceive it as being 91.5% of the maximum power that the laser is capable of. And I can tell you from much experience that an 8.5% drop is imperceptible.

And there is another factor to consider. Many laser manufacturers actually "saturate" the modulation input to around 4.5 volts or even 4 volts. So even if QS was "only" putting out 4 volts, this would not represent an 80% command into the laser, but perhaps rather a 90% command or even 100% command.

This topic bothers me, mostly because there are so many non-qualified opinions. The points raised above are facts, not opinions.

Now, here's where the rubber meets the road. The MAIN PROBLEM people experience is because of the lasers themselves, which may respond to color signals in a way that, well, they really shouldn't. There can be low-frequency phenomenon inside the laser having to do with the heat caused by the modulation, and the power that you get out of a laser may depend entirely on the NATURE of the modulation itself. In my case, I have a Viasho laser inside my Kvant laser that does not give optimal output power under all circumstances. I am sure others on this forum can say the same about yet other laser manufacturers. And not all models are made the same or have the same problems.

I think that, in order to put this topic to bed, we should have tests at the upcoming SELEM meeting. There we can measure the color signals with a scope, and measure output power with a real laser power meter and perhaps even do side-by-side comparisons of various kinds (with various lasers, various software, etc.)

I am 100% confident in our software -- especially QS 2.0, for which testers report delivers so much power that it burns holes in their walls. And yes, it does put out 100% power if you ask it to put out a single beam, contrary to what Badger wrote above (I guess he gave up before testing our latest version...)

Also, just the other night I was scoping the color signals as we refine what we are doing for RGV lasers. I can say with 100% confidence that our color signals do go all the way to 5 volts, and that the "off time" is really very minimal.

Bottom line: Stop complaining to Pangolin and start complaining to your laser manufacturer! And tell them that Pangolin will gladly help them and give them advice on how to improve their own product.

Best regards,

William Benner

PS: QS 2.0 offers three methods of laser modulation. One of them is TTL, and it doesn't work by simple thresholding (which does not yield optimal results). If you have TTL lasers, QS 2.0 will deliver a true optimal experience from low-cost TTL lasers.

[badger1666]

well what can i say to that
if qs2.0 offers so much more power then that clearly shows we had good reason to complain , before that.
after all three other dacs and software i tried work just fine
sold them to go back to pangolin only to be dissapointed
moved to lds and all fine, then you go and update to qs with all this extra power
the only thing i am going to do is stop wasting my money

[norty303]

Hi Bill

Just to add a little here, based on my recent emails with you - although you sent me 'fixed' versions, this appeared to be related to static beams, not general output, and I let it go after that as the email thread was running on, somewhat!

On the old thread 'FB3, worth it?' where this all came up originally, I think you acknowledged that you'd seen 'something' that didn't look right and were going to have it investigated. Some of this may have been in relation to output comparisons between different Pangolin products (e.g. QM and FB cards)

If you are going to do some investigation at SELEM, could you do some side by side comparisons between different Pango platforms and let us know if there are indeed (or indeed, not!) differences inherent, and whether thats by design or not?

Cheers

[Pangolin]

@ Badger,

We strive for 100% customer satisfaction. That's why we offer the money-back guarantee. In your case, you weren't satisfied, and we weren't able to meet your needs at the time, despite attention from myself and Francesco -- two very qualified people, so we gladly refunded your money. No problem and life is good. There are many choices for laser software. As long as your happy Badger, that's all that matters.

Regarding your implication that people complaining "proved there was a problem with 1.0", well I would say that the word "problem" is in the eye of the beholder. QS worked in a way we designed it to work, for the audience intended (and remember, this is intended for an unsophisticated audience). Nevertheless, a few customers complained so we looked into it and made a change for 2.0. It shows that we are responsive to customers, even when they are a minority...

I will say (and also said to Norty in a private email if memory serves) that the change represents a sacrifice. Yes, now you will get more power from a single, or small number of beams being displayed, but there are laser safety implications to all of this. In QS 2.0 we try to abate the implications by providing additional information for users, and the users must also make additional steps to enable the beams.

I will point out that our priorities might be different from competitors. Of those selling laser software into this industry, only Pangolin has patents on laser scanning, shaping laser beams, projecting laser beams, and protecting humans from laser beams (and lasers from humans too). Scanner longevity and laser safety are two very important things to us whereas our competitors seem largely oblivious to these things...

@ Norty

I get an air of "conspiracy theory" from you. I even got this in our private email discussions. Here's the whole story:

People on PL complained about power within that thread you mentioned. I had three separate people on the Pangolin team look into this, and when they did, they discovered that indeed, LivePRO for the FB3 (and I think LiveQ too, I can't remember) gave timing that was not expected.

As a result of the analysis, we made changes in the beam system of LivePRO and also the information lead to changes being made in other software such as QS 2.0 and even LiveQ. We also put a special mode into LiveQ (also carried through to QS) in which if you hold the CTRL key while clicking a single point, you will indicate to the software that it is your intention to "place a beam" and not just a single point. That "beam" has special behavior in our software, and allows much higher power.

Regarding "other than beams" (what you called "general output"), well I just think there is a great deal of confusion over this whole topic. I think people are acting on emotions, or the reading of volt-meters rather than cold hard facts. That's why I offer to put this topic to bed at SELEM -- to try to push out all of the emotions, and get a room full of people who will agree to what they saw with their own eyes and using real test equipment...

As far as I know, everything is working as expected now. But if credible information is presented to us that there is a problem, we'll investigate and make changes, just as we have in the case of LivePRO and QS.

Best regards,

William Benner

[DMills]

I second the fact that a scope is the ONLY tool for measuring this sort of thing, all multimeters are without exception too slow (You need peak readings on 20 microsecond pulses).

The short dead time is a reasonable way of handling it if the IO processor is not quite fast enough or if there is no double buffering (which has issues of its own), it is just unfortunate that it interacts so badly with the known modulation issues in the common cheap DPSS sources.

Piss poor modulation on cheap DPSS is the real story here, not a few tens of microseconds of drop out in a modulation signal.

In real show use of course the mod line is all over the shop and the power from the DPSS green will bear at most a loose relationship to that implied by the modulation voltage, so this will only be obvious with constant full power beams.

Does anyone know if the modulation problems with cheap DPSS are down to the pump diode, laser medium, SHG or just cavity alignment?

Regards, Dan.

[mixedgas]

Does anyone know if the modulation problems with cheap DPSS are down to the pump diode, laser medium, SHG or just cavity alignment?
Regards, Dan.

OK, what I have seen:

I. Bad thermal management in the laser. KTP and vandate/yag are temperature sensitive, LBO even more so. All are insulators with poor thermal conductivity, so cooling them is difficult. Non linear crystals change their phase matching angle with temperature. Really good lasers heat the KTP and cool the vandate/yag.
Laser output tends to depend on recent history in the poorer lasers.

II. Poor choice of the logic input structure on the TTL diode driver. Many of them, as so called "TTL" need enough current sunk that only 100 ohms or less to ground will start them to blank. Some have a TTL spec, some are CMOS with a pull up, some have a comparator, some wink if you couple 60 hertz in with your finger. Some have horrible hysteresis. I'm not sure about the current ILDA standard, but the input impedance in the old standard was 600 ohms. I've seen some at infinity, and I've been told about some at 50-100 ohms. I have one laser where the input device is a LED in a very slow optocoupler with 200 ohms in series. If there is one laser out there that is on at 2.4 volts or higher and off at .6 volts or lower per the TTL standard, I have yet to find it.

III Analog inputs, ditto on the impedance issues. Some lasers are biased internally so that any voltage above 0 volts adds to diode current set at just below lasing current. Some have the diode at zero current and threshold is a few volts up, cramming all the output into the last volt. Some are very good, fast, and linearized. Again, impedance is all over the place. I've seen lasers that need a analog opamp follower driving the input.

IV, There is no standard for linearity. There is no standard for threshold. There is no standard for rise and fall time. Last but NOT least there is no standard for how a laser is supposed to behave for a single blanked point in a train of illuminated points, nor a standard for how to respond to a single illuminated point in a train of blanked points.

VI, The laser tuning is often set up to favor long trains of constant illumination, being off for long periods of time results in a dim laser for a few seconds until it reaches steady state again.

Yet I have also seen lasers that are nearly perfect. The 808 nm diodes can easily follow to 150-250 Khz or more. The doubling is instant. The laser material has a long upper state storage time, and this can be a problem.

DPSS Blue is even worse then green, for a variety of other reasons. LBO in a 473 nm blue needs held to about +/- .1' C. 473 blue often has 5% low frequency noise riding on the cw beam

All of this needs hashed out to be a standard. It would somewhat help if control software/hardware had independent blanking delays for each color.

This is not new, there were complaints on early PCAOMs that they would not saturate at just 5 volts, and that they would not 100% extinguish, a leakage signal when off 30 dB down still being visible in a very dark room.

There is a dormant portion of the ILDA test pattern dealing with blanking. It is there for tuning galvo blanking, but how it was chosen is a mystery to me. There is someone I can ask, if he knows. I'll call him tomorrow.

Steve

[gottaluvlasers]

Steve-

WTF man. lol, your intelect never ceases to amaze me! Remind me at SELEM to sit down with you and have a nice cold drink (im buyin).

Sorry, i dont want to derail this thread. Just wanted to toss this in here.

-Marc

[rfourt]

Oki... This got bigger then i thought.

Thank you so much for your input Pangolin. ANd all other.. And As the poster before me said.. Damn Steve, would love to share an hour and a cold one with you.

Anyway.

I think it has not really been cleared after all. or perhaps it has but ive missed it in all the long foregin lanugage posts here.

What i mean is. And the problem still is.
Ok Lets say my VIasho PSU (VD-III-N) isnt good enough for the modulation sent out from the FB3 when i draw a single white circle. How come it then works if i draw 3-4 Circles at the same spot? Just like badger said.

When i draw a single circle my PSU shows me 2.03 on the Display, wich is no way near the maximum but when i draw 3-4 circles and place them over eachother the PSU shows about 5.50 on the display.. Not max but close anyway. (perhaps there is an patch that can fix this??? )

I mean this tells me clearly there is something in the software or the Dac that is not putting out maximum on a single circle. Atleast not my version and to my laser anyway. If i draw a Targeted beam it gets me about 4.75 on the display.. I know i shouldent trust those numbers for what they are on my PSU display.. But i can atleast see that 2.03 is lower output light power then 5.00.

I will try and do some more testing and do some testing with an osc. And im sorry i made the test before with a normal Multimeter, i dint know that couldent be done.

Pangolin.. Do you have perhaps an estimate on when the QS 2.0 will be released?
As i said. i really like QS and LivePro and would like to continue to using it although this bugs me alitle.

Thank you.
/Rickard