Building of THOR has begun

[vk2fro]

Yes exactly - also I wasnt suggesting a green diode, just trying to explain a few things about DPSS.

Even some of the <1W greenies are tec stabalised.

oh yes the good ol 635 - more like a torch/flashlight than a laser - 660's are almost as bad, some with really horrible 5x8mm beams - try getting all of that onto your galvo mirrors

 

[Leodahsan]

@vk2fro
I knew you weren't suggesting a green diode. I just did a joke to remember that no green laser is available, only DPSS or diode. There is no choice, or you use DPSS on your projector or laser, or you don't use green at all (unless you have a 'happy' budget available).

horrible 5x8mm beams

WITHOUT fast axis correction. With such lens, they work very fine IMO...
The 635 is preferable, as 500mW of it looks like 2W of 660... it is worth

 

[goninanbl00d]

It's just a common side effect of DPSS lasers- none of them will have a true linear curve when modulated through the pump diode.

Remember, you've got a separate laser system running inside, with it's own needs. As Leodahsan said, the crystal assembly (both Nd:YVO4 and KTP) are temperature and wavelength sensitive. Even a small shift in either temperature or wavelength will cause a noticable power fluctuation.

Remember, the heat output of the pump diode will change as it's modulated; this change must be compensated for. Simple modulating of the diode won't do, for example, changing from CW to 5kHz TTL can cause a temperature change of a few degrees within seconds, along with the accompanying wavelength shift.

Before I begin explaining the next bit: get this into your heads. Most <300mW labbies have a TEC on the pump diode, most >300mW units have TWO TECs, each with their own sensor/driver, one on the pump, one on the crystal assembly. Some higher-power assemblies (2+W) even have three TECs, one on the pump, one on the gain medium (Nd:YVO4) and one on the KTP (As a heater, KTP likes heat).

As a result of this, the TECs are modulated alongside the pump diode. You ever seen threads about lasers going 'out of tune'? This is where they go wrong- there's an issue with TEC drive tuning, which in turn, causes instability issues when the laser is modulated. All the DPSS I know out there have a modulated TEC, an unmodulated TEC is asking for mode-hopping and power fluctuations.

On that note, if you want anything even resembling remotely stable power, TEC stabilisation is an absolute must. I've seen 50mW lightshow-style modules with TEC, a 1W needs a TEC if you don't want your laser to turn into a TEMwtf projection device.

And if you think 532nm's bad? 457nm has an even slower response time, and even less stable.

The only way to get something even remotely linear using the laser only is to use optical feedback, this adjusts output on-the-fly using a power reading taken from an optical pickup.

The other way, that requires complex and fidgety equipment external to the laser is to use an AOM.

So, there. That's it; there's really not much to it. Every DPSS green will be non-linear to an extent, except some are better, much better, than others. There's nothing we can do about it, just be glad the beam specs aren't like our 445s

As for the reds, I have one of these 'flashlight' reds sitting on my desk next to me. It's a CNI unit, OEM, 655nm at 500mW. 5x8mm beam at aperture, with 2.5mRad divergence (measured, confirmed).

It's a 8x8cm blob at 20m, and it's visibly divergent. It's not ideal, of course, but it's the only cheap option. It's either that, or throw down $$$$ for a 640. Yes, it's fine and dandy if you can afford it, but most times, 655 is still the way to go.

Even with a FAC, you won't get any better. These diodes are multi-mode and multi-emitter, you simply can't get any better out of them even with corrective optics. 2.5mRad is good, 4 to 5mRad is not unheard of. At this point, even with the rectangular beam profile, I'm just glad they aren't like the 445nm diodes, with a distinct fast and slow axis.

Inevitably, you'll lose a *bit* (ahem) of power, I'm estimating 100mW of my red to disappear. But $250 for 500+mW of red? It's hard to beat, especially when you're on a tight, tight budget. I'm not complaining.

And on a final note, DHOM is one of the better manufacturers out there, in the same league as CNI or Viasho. I'd definitely go for them, one of my regrets with my build is not going all-DHOM (with a CNI scanset*). But that's kinda hard to do when 3/4s of your budget go flying out the window. Oh well, long story.

I'd definitely go for DHOM. Thumbs up, that's for sure.

*Yes, I know it goes against everything I've said about Sonima being absolute bulldust. But the SS2800s (ScanPro50s) are one of their better galvos, and at 60 degrees at close to 20kpps, it isn't too bad of a beamshow solution. Not to mention it has an angled X-galvo mount, which is essential when working with oversize beams, meaning more of a given beam will fit after your first bounce.

I'd have liked a pair of EMS4000s, but $1500 for galvos is too much for me, even if it does mean getting a pair of indestructible galvos. You can't actually wreck them, even grabbing one of the mirrors and holding it while scanning (which would kill most galvos and amps) won't hurt it. Overspeed, underspeed, it's one tough set of scanners.

 

[vk2fro]

Thanks Goninan - that was an interesting read. Still waiting for my processor buffer to empty out on the second half

Yeah I've read up on the DHOM's - definatly getting one for my greeny.

As for my red, yes I know its going to sting the wallet, but I am getting the kvant 640 for my projector - yes its going to cost me a small fortune, but it's going to fit on my galvo mirrors, which might be hard with a 655 even with corrective optics.

 

[goninanbl00d]

Thanks Goninan - that was an interesting read. Still waiting for my processor buffer to empty out on the second half

Yeah I've read up on the DHOM's - definatly getting one for my greeny.

As for my red, yes I know its going to sting the wallet, but I am getting the kvant 640 for my projector - yes its going to cost me a small fortune, but it's going to fit on my galvo mirrors, which might be hard with a 655 even with corrective optics.

Problem is, the nature of these multi-emitter diodes results in a rectangular beam profile at aperture, and there's nothing that can be done about that. All the FAC does is ensure both axes have the same divergence value, the FAC cannot 'squish' the beam into a square at aperture.

There are 'beam-squishing' lenses available, but they're lossy, and expensive enough to make 640, or even 671, a viable option.

That, or use a spatial filter to 'crop' parts of the beam off. You'll still get a square beam at a distance, but you end up losing whatever power was in the rectangular 'segment'.

So, in the end, red still is the limiting factor in our projectors, and unfortunately, there doesn't seem to be a red revolution any time soon. So, we're pretty much stuck with downright terrible options, with little to no hope in sight.

UPDATE: I put my red into the projector, and turns out, I'm not losing as much as I thought I would off the galvo mirrors.

Although it says 5x8mm at aperture, there's a narrow band in the middle of the beam profile (like this: [-]) that has most of the power in it. This is around 2x5mm, and this fits onto the galvo mirrors fine, although I am losing at least 50mW onto the roof at this point.

 

[borgqueenx]

im thinking of buying this:
meierlight
watch it says DIODE, not DPSS.
But i have no idea if im really going to buy this since the dimensions on the link are a really tight fit but acceptable, but if i contact them they say the laser is bigger. unfitable.

and this:
1W/1000mW Red laser module/TTL and Analog modulation [OL-R-1W] - $369.99 : Welcome to O-Like.com, Your source for laser products
wich has a smaller beam size then the others i found for desame price range.

or can you guys reccomend me something else?

i already have a analog 445nm laser, wich goes to 700mw. Going to install the analog driver within the hour.

 

[vk2fro]

Borg - many sellers mislabel their stuff on ebay like that, either through ignorance, because they don't know what they have (I once saw a green labby labelled as a green argon laser), or deliberatly (to increase the hit count). That laser is definatly a dpss. (its a DHOM optical one so your purchase decision is good.

Goninanbl00d you may have just saved me a tonne of cash. I'm willing to take the risk on a flashlight red if all i am going to loose is 50 to 100mw, considering you can get them in multi watt power levels, who cares about a paltry 50mw (well most of us do, we want all those mw going out the aperature!)

If I end up with a less than satisfying performance I might even cube in the 640 at a later date (provided it can be done and the 640 isnt internally cubed)

edit: 500mw of 635 is half the price of the kvant 640, with a not so terrible 5x6mm beam (almost symmetrical). Its a DHOM as well. Just reinstalling chroma to get an idea of how the colours will blend up...

 

[qumefox]

Keep in mind chroma only shows you what the 'dot' on a white surface will looks like. The output it gives you won't be for what the 'beam' will look like. You have to take reiligh scattering, etc into account for that. You can have the output tuned for white on a wall, and the beams will look blue heavy.

 

[goninanbl00d]

Chroma is horribly inaccurate, and as qumefox said, it doesn't take beam visibility into account.

@vk2fro, don't forget, there's always the divergence issue. A divergence of 2.5 (compared to 1-1.5 for a corrected 445 or 532nm beam) will be clearly noticable, not to mention an average value of 3mRad is to be expected.

CNI and DHOM both offer 2.5mRad and 3mRad models, you may wish to consider them. Just bear in mind that 2.5mRad is a LOT put into perspective, and will be very noticable, even during beamshows.

Not to mention, you have DT40 Wides- and the amount of beam are lost off the Y galvo is dependant on the scan angle at which the X galvo is running at.

Remember- the Y galvo is perpendicular to the X galvo- and not everything that fits onto the X galvo will fit onto the Y galvo. The amount that fits will decrease the larger the deflection angle, and pushed far enough, I wouldn't be surprised if you'd lose half your power because it didn't fit on the Y galvo mirror.

I'd still shoot for the KVANT 640, if you can afford it. For most of us, 635 is a 'cheap' (har har, it's more expensive than 532 in terms of mW/$ as you start looking at the higher-power units) fix when we need red.

 

[vk2fro]

I knew there had to be a catch. So i guess its going to be

500mw DHOM green
1W 445nm blue (adjusted down (flexmod) to suit the other 2 lasers)
600mw kvant red

 

[goninanbl00d]

I knew there had to be a catch. So i guess its going to be

500mw DHOM green
1W 445nm blue (adjusted down (flexmod) to suit the other 2 lasers)
600mw kvant red

The amount of power you lose depends on the scan angle. As I was saying earlier, here's an exaggerated example, but nonetheless, shows why you lose more power the higher the scan angle.

This is also one of the reasons for wanting the ScanPro50s, they have an angled scan block, as well as being able to do 60 degrees optical at a decent speed.

 

[vk2fro]

Thanks GB - it makes sense to me to just save up for the kvant with its 2mm beam and low divergance; as my projector will a lot of the times be running in a small environment. Since it will be doing beams, having the scan angle up around 80% will cover most of the venue. This same issue would not exist in a bigger venue, and scanning at 50 or 60% one might be able to get away with the fatter beam of a 635, provided the laser is orientated correctly to assure most of it hits the mirrors.

But in my case, the one size fits all (uber expensive kvant) looks like the way to go. For my next projector (yes I am planning on building more), i'll get slower galvos with bigger mirrors, in order to be able to use the cheaper 635 without losing half the output off the mirrors

So this beasty which I am building in this thread will be my top of the line projector. Then I'll be building a couple of half watt greens, and then some smaller RGB's

 

[vk2fro]

YA SEE!!!!! this is whats keeping me motivated to build this thing!!!!



Thats one awesome show. I'll need to build a couple more projectors tho! If I hear that tune close up at the local pub though (like right next to me), I'll be able to buy them. The Strauss piece thats playing is the radetsztky march, the same tune an aristocrat slot machine plays when you score a big win

 

[borgqueenx]

YA SEE!!!!! this is whats keeping me motivated to build this thing!!!!



Thats one awesome show. I'll need to build a couple more projectors tho! If I hear that tune close up at the local pub though (like right next to me), I'll be able to buy them. The Strauss piece thats playing is the radetsztky march, the same tune an aristocrat slot machine plays when you score a big win

indeed. but those projectors also have divergence control. i guess thats also pretty expensive

I wanna do crowd scanning one day but i cant control the laser focus point

I hope there will be more laser shows soon around here....its been like 10 months since i saw a real laser show besides the builded-in itrust show in my projector

 

[vk2fro]

teehee just set up my DT40W's and the 150mw green laser for a test run after finding where I'd put my frame streamer. Darn things cover my entire living room in laser show - the widest my 500 mw laser projector would go is just covering wall between the servery and the hallway

Couldnt run em for long though, as theyre not mounted on a heatsink, so only ran it for a a minute.

I scanned at 16,000 pps, full setting on the knobs on the frame streamer. I didnt want to push them - the beam never left the x mirror or the y mirror so I guess I wasnt overdriving (and they werent squealing like miss piggy)

Since the frame streamer is tempermental for some reason with my setup, I'm going to now concentrate on getting the pangolin FB3 and Quickshow from Dave at LSP - This also means no more non laser parts to buy apart from screws, bolts etc.

 

[vk2fro]

After feeling how toasty warm the galvo amps get when running for 30 seconds, I decided they needed some cooling...

(yes I cant drill to save my life, but the bolts hold them firmly there). Attached complete with heatsink compound. If tuning is nessecary, every pot is right there in plain view.

I'm going to need a 3U case, and mount all my psu's vertically. Thats ok, I'll stuff a single green or RGY into this case