RGV build, (first),lots of questions

[ramsoh]

Pressing Questions
alright i have been researching the last few weeks about making a RGV laser.

i mainly researched crowd scanning, MPE tables and the like.
which brings me to my first pressing question, i understand that lasers can have analogue modulation, and that some software can do attenuation mapping. but, how low can you dim down a laser before it "cuts out"? (if it does even do that )

say i had a 200mw laser how dim can you tune it down?

i also here you want to cause you beam to diverge more if you are crowd scanning, what lens should i use then?

Down to Business

for the actual laser,i believe what i need is
the lasers
there drivers
galvos
and there amps
optics (dichroic mirrors)
and a DAC

first of all i dont know where to get any of these things, i know theres lots of websites that ive been to but im not sure what is good, or good for the money. etc

let me still go over what i was thinking

lasers,

i have been playing with chroma and it said for a .4 watt laser

50mw of 532
150mw of 656
200mw of 405

it showed that this combination gave good white balance.

then again im not sure about these colors or powers

ive heard controversy over 405 that it give deeper colors but is dim on its own ? is there truth in that? is 473 or something in between better?

do these wavelengths look good,i see them on chroma but is that an accurate representation? do lasers mix well?

ideally i would have analogue modulation so ive been told to just buy the most powerful lasers i can afford and play with the white balance after. good idea? (on a budget)

What about the beam width? whats the best i thought the smaller the better but i could be wrong

also when ive been looking around, the drivers for these lasers look huge are there specific ones which have smaller drivers?

on the topic of cotroler/drivers i want analogue,and when i look at the specs it will say something like 1-15000 Hz analogue, is that sample rate of the controller, cause im pretty sure i wouldn't be pulsing a analogue signal (unless they mean pwm)

Galvos

this is a topic i am lost in.
i dont even know if your dac directly connects to the amps or if there is an in between part that i need

but mainly i dont know what is good, cause ive seen the numbers for the ilda test pattern like 60,000 but thats at 8 degrees, id like to use alot more deflection

also thell say somthing like 80 degree max when you can see that the frame there in doesn't even allow for that range, not to mention the size of the mirrors

so what is the max defection i should expect form a galvo setup, ideally id like a wide angle for indoors, or can i use some sort of optic to widen the swept angle?

also with .4 watts , going down to 50 mw of a single color, how fast should i expect to be able to scan? (i was thinking of doubling the powers to allow for better scanning)

also if im limited to slow scan speeds for wide angles, can i still do beam shows, will it look good?

on top of that the amps, im assuming i buy the ones that work with the galvos and i should be safe.

Optics

this i thought might be the easyest, i just find out the mirrors i need, for the right wavelengths, find the best quallity ones i can and buy them(and a way to mount them)

actually i do have a question, what am i exactly looking for in optics? (other than transmittance)

DAC

all i know is that i could make one out of a sound card and also pangolin makes good ones.
so any info would help.

lastly i was going to mount everything on a nice thick plate of aluminium and put a box around it with a fan.

Conclusion
so basicly i was looking for a guide for me to follow so that i know what im looking for. i know theres a lot of questions but trust me i have been looking.

also if there is something i havnt considered that you have knowledge on let me know (ex dmx board)

any links to good places to pick these parts up would be nice along with any advice.



edit(i do realize i havnt mentioned software, didnt think it important till i decided on a DAC although info on software would be nice as well)

[Things]

Hey, I'll try answer a few of these questions for you.

i understand that lasers can have analogue modulation, and that some software can do attenuation mapping. but, how low can you dim down a laser before it "cuts out"? (if it does even do that )

say i had a 200mw laser how dim can you tune it down?

Analog modulation these days is done simply by varying the power to the laser diode. However, there are limitations.

Green lasers are DPSS, and involve using sensitive crystals to produce the wavelength you see. If you try to bring down the power of the laser diode too far, the laser can become unstable when being modulated. This is called "jellybeaning", and is most evident in cheap laser modules, and looks like the laser is being pulsed when it shouldn't.

There are not really any guide on how far you can turn it down. That all depends on the quality of the laser, the laser drivers resolution, your DAC's resolution etc.

first of all i dont know where to get any of these things, i know theres lots of websites that ive been to but im not sure what is good, or good for the money. etc

This depends on where you live. Maybe fill in a bit more details in your profile and we can help out more with places to buy.

ive heard controversy over 405 that it give deeper colors but is dim on its own ? is there truth in that? is 473 or something in between better?

This is true, 200mW of 405 by itself in a scanner would be barely visible, well, compared to your other colours anyway. Some people add a tiny bit of green to the 405 at all times, which moves the colour up to a nice cyan. 473 is much better for brightness, but may stretch your budget!

do these wavelengths look good,i see them on chroma but is that an accurate representation? do lasers mix well?

For low, close powers like these, it will give you an idea of if its gonna be too green etc, but this all depends on your eyes perception of white. For example, your version of white might have more of a greenish tinge than mine, which could be more blueish. If it says you'll get white, you should be able to achieve it in some form.

ideally i would have analogue modulation so ive been told to just buy the most powerful lasers i can afford and play with the white balance after. good idea? (on a budget)

Yes! However, make sure your balance isn't too far off. Don't buy a 1W green, then a 100mW red and hope you can mix for a good yellow. You may be able to, but you then have barely any more room for dimming the laser, since it's already almost at its lowest power!

What about the beam width? whats the best i thought the smaller the better but i could be wrong

This is highly subject to your lasers. For example, DPSS greens have really tight beams, and if you were to combine it with a 635nm red, the green beam would look like a yellow beam, with a red halo!

With beam sizes, lowest is best. Also keep in mind, you want to shove as much light onto your galvo mirrors and not have a huge amount of spillage off the side of the mirrors.

However, it is important to match your beam sizes if you wish to do graphics! If you have a green beam that may be 1cm wide at 3 metres, and a red beam thats 10cm wide at 3 metres, your graphics wont look very good! By the nature of your post, it looks like you are more into beams though.

also when ive been looking around, the drivers for these lasers look huge are there specific ones which have smaller drivers?

This depends on the brand of laser. The new laser-wave drivers are quite small in comparison to many other companies!

n the topic of cotroler/drivers i want analogue,and when i look at the specs it will say something like 1-15000 Hz analogue, is that sample rate of the controller, cause im pretty sure i wouldn't be pulsing a analogue signal (unless they mean pwm)

This rating is just purely how fast the laser can turn on and off. Since analog modulation isn't PWM, this doesnt really apply (Although, you can still turn an analog laser on and off like a TTL laser)

15Khz analog just means that the laser can handle being turned on and off at 15000 times a second.

i dont even know if your dac directly connects to the amps or if there is an in between part that i need

This is correct! However, between your DAC and the projector you typically have some DB25 (Printer) cable, so your DAC doesn't have to be built into the projector.

but mainly i dont know what is good, cause ive seen the numbers for the ilda test pattern like 60,000 but thats at 8 degrees, id like to use alot more deflection

These seem like some high end galvo's you are looking at there! However, 60Kpps just means that the galvo's can "draw" 60,000 points per second, but at only 8 degrees scan angle. You can decrease the scan speed and increase the scan angle if thats what you want. There are also scanners available designed for extremely wide scanning (DT40 WIDE's)

also thell say somthing like 80 degree max when you can see that the frame there in doesn't even allow for that range, not to mention the size of the mirrors

These may have been a set of wide scanning galvo's. Typical galvo's have a max scan angle of around 60 degree's.

so what is the max defection i should expect form a galvo setup, ideally id like a wide angle for indoors, or can i use some sort of optic to widen the swept angle?

If you are looking for wide angles, regular galvo's may be enough for what you want. But like I said before, if you really wanna scan WIDE, then look into some DT40 wides.

also with .4 watts , going down to 50 mw of a single color, how fast should i expect to be able to scan? (i was thinking of doubling the powers to allow for better scanning)

Not sure what you mean here, but how fast your galvo's can scan and the powers of the lasers don't really have a relationship.

lso if im limited to slow scan speeds for wide angles, can i still do beam shows, will it look good?

Sure! The trick here is to only use simple frames. Lines, waves etc are all nice beam effects and typically only require low scan speeds.

on top of that the amps, im assuming i buy the ones that work with the galvos and i should be safe.

Both of the galvo's SHOULD have matching amps. The amps and galvo's have been tuned for each other, and using other amps could damage your galvo's in the worst case. You can retune the amps, but it's not a quick process!

actually i do have a question, what am i exactly looking for in optics? (other than transmittance)

This depends on your lasers once again. With dichro's, you need to specify what you want. ie, pass green (532nm), reflect red(640nm) for instance. Transmission and reflectance efficiency wont effect your scanning, but will drop some laser power from your lasers. With highly inefficient dichro's, this means your 50mW green could end out coming out of your scanner at maybe 30mW.

all i know is that i could make one out of a sound card and also pangolin makes good ones.
so any info would help.

lastly i was going to mount everything on a nice thick plate of aluminium and put a box around it with a fan.

There are many more DAC options out there! ie, Riya, Mamba, Easylase just to name a few.

This depends on your budget. If you want to focus more on good lasers, then it may be beneficial to build a soundcard DAC, but if your budget stretches enough, you may want to buy a FB3 from Pangolin. I (and many others) use the FB3, and will all tell you it's a great DAC with heaps of features, however will cost a fair lot more than a soundcard

Most DAC's come with their own software. Pangolin DAC's all come with software, RIYA DAC's come with software (And have support from many others like Spaghetti), Easylase has a lot of home-made applications for it, etc.

Knowing your budget would help.

Hope that helps Welcome to PL also.

-Damn, thats gotta be the longest post I've ever made. Buffo, watch out! :P

[White-Light]

For red try 640nm. Tighter beam and much brighter (will have to run the chroma prediction again though).

For blue try 473 if you can afford it. There will be a world of difference. As you're planning on doing beams, brightness is probably more important than true colour so 473nm (cyan blue) is probably the best option. If you want a truer deeper blue for graphics then you probably want 458nm (ask McCarrot as he stocks these) or 445nm but the penalty is brightness.

For 640, 532 and 473 chroma predicts:

532 @ 100mw
640 @ 200mw
473 @ 100mw

Thats a perfect white according to the prediction and will be much brighter than your originally proposed set up.

(Please check the figures yourself in Chroma in case of user error!)

For diverging beams, on here its usually suggested you try with a -3 diopter lens.

For audience scanning, you want a power meter and I suggest you use the simple method as MPE tables, calculations etc are extremely complicated - the effects are cumulative so it means calculating every effect and knowing in advance what you're going to be doing.

With the simple method, provided the laser is set to a safe level and you make proper measurements (note meter sensor masking and a conversion to mw/cm2 still required) , you can simply do a display without further worry of exceeding mpe this side of a galvo failure or similar.

[Doc]

405nm adds another problem if you are planning to audience scan. As already mentioned above; it is barely visible even at relatively high power and just because it is less visible doesn't make it less dangerous. In fact it makes it more dangerous. Because it doesn't look very bright, the known .25 second bright light aversion response is less likely.

In summary mW are mW and they will still cook retinas whether you can see them or not.

405 is great for graphics as it makes many surfaces fluoresce brightly, but you need dangerous amounts to be usefull for beams.

[ramsoh]

First of all, thankyou for all the info you have shared with me thus far. Second, a clarification:

also with .4 watts , going down to 50 mw of a single color, how fast should i expect to be able to scan? (i was thinking of doubling the powers to allow for better scanning)

Not sure what you mean here, but how fast your galvo's can scan and the powers of the lasers don't really have a relationship

What i meant was with a relatively low power how fast could i scan without making it too dim?

[Doc]

First of all, thankyou for all the info you have shared with me thus far. Second, a clarification:



What i meant was with a relatively low power how fast could i scan without making it too dim?

Modulation issues aside; scan speed shouldn't affect the apparent brightness.

[ramsoh]

first id like to say, that the reason i wanted to go for the wavelengths i did was for a broader color range.

I like the deep magentas and reds that chroma showed me.

Because it doesn't look very bright, the known .25 second bright light aversion response is less likely.

then again i never thought of the quarter second aversion rule

so i may go for a slightly higher wavelength, such as 457 or 435, ill play around with it till i like what i see.

[ramsoh]

three things,

first ive been told, to purchase a powersupply that can offer more power than i need so i will not need to replace it if i ever bump up my power. this makes sense to me, however most of the time i see lasers with there own power supply sold together or suggested that they be used together, or is this person suggesting i buy a separate psu more powerful than i currently need?


just quick, im assuming for analogue, your plunging the analogue signal into the psu for the laser amirite?

and about DAC, i dont see why ppl want there DAC outside their laser, if you get a usb DAC why not put it inside the laser, and connect your computer to your laser via usb?

[edison]

This person that ramsoh is talking about is me to make it clear for everyone I suggested to buy a heavy powersupply like a traco top 100-105 to power all your lasers. Most lasers come with their own 5v powersupply but if you building a rgb projector you have 3 powersupplies and they all do 5v. They take heaps of room and if you want to upgrade your projector with heavier lasers you dont have enough juice to power the new one. Some members have build a projector and half the room of the case they use is take by powersupplies. But they saved 50 euro,s...............on a projector that costs about 2000 S
Same as building a quad that can deliver 1,0 watt with good specs. Its possible because companies like kvant and arctos do it. But they do it right because everything is precisly manufactured so the result is perfect. If someone is building a projector and do it right you can save heaps of money by building it your self if use quality parts. If you dont have the kind of money start with a green projector that way you save money but you can use the money to build a quality projector. After a while you can ad red and blue because you already have the room and the heavy 5v/20 amps traco powersupply for it. So if you ask me build a quality projector and ad red and blue

Just for the record a PSU is a powersupply and where you plunging the analog signal in is the driver.

[LEDpaint]

and about DAC, i dont see why ppl want there DAC outside their laser, if you get a usb DAC why not put it inside the laser, and connect your computer to your laser via usb?

You could do that, but you'd probably want to go USB over Ethernet. Some people here have even gone wireless this way. USB cables, themselves, generally aren't well shielded (if at all) and you can't make run that's very long or you'll suffer bad attenuation (16 feet, I believe, is the max). USB extenders are very dodgy and have a lot of latency, from what I've read. If you search the forum, there's some good info on this.