Safer 100mw Green Projector

[steviobee]

I am looking to possibly get a very small projector that still has ILDA connection for use at home.

My stepdaughter has developed quite an interest for lasers and at only 8 (nearly 9!) she's not allowed anywhere near the 3w RGB.

I was wondering and looking at something like this: http://www.goldenstarlaser.com/g100a-p-191.html

I appreciate it is still dangerous and caution would be taken, perhaps goggles for her, but I would be a lot happier using that with her around and she can get involved with making her drawings come to life, etc.

It seems pointless getting anything more than green and it would be nice with DT30's but what would DT20's be like as fitted as standard? The whole projector is delivered pretty cheap, I would rather that than a plastic cased DJ special from Maplin I think.

I could then think about using it as a second projector for crowd scanning on smaller venues?

What do you reckon?

[White-Light]

100mw works out 26 times MPE @ 2 metres assuming the calc and my usage of it is correct (see below).

One way would be to measure and safety lens it using a Pangolin lens or one of Edison's cheaper lenses given that its for your daughters home use only. I'm sure Edison could test with a laser to determine the correct lens to use if you could give a true power reading.

Another way is to BAM it but this assumes it will still modulate OK at the brightness reduction level you need.

Currently, using McCarrot's online MPE calculator your proposed 100mw Goldenstar comes out at 260mw cm2 at 2 metres compared to MPE which is 10 mw cm 2, so 26 times the safe limit!

(and that assumes its a true 100mw whereas you'd usually expect a higher figure from a reputable manufacturer).

http://mpe.laserextreme.nl/

Pangolin's advice to me was that they wouldn't like to be audience scanned with any laser of less than around what I interpreted to be a 10p piece, so you make of that what you will.

[swamidog]

how about a little <5mW green?

much safer, and still plenty bright in a dark room.

I am looking to possibly get a very small projector that still has ILDA connection for use at home.

My stepdaughter has developed quite an interest for lasers and at only 8 (nearly 9!) she's not allowed anywhere near the 3w RGB.

I was wondering and looking at something like this: http://www.goldenstarlaser.com/g100a-p-191.html

I appreciate it is still dangerous and caution would be taken, perhaps goggles for her, but I would be a lot happier using that with her around and she can get involved with making her drawings come to life, etc.

It seems pointless getting anything more than green and it would be nice with DT30's but what would DT20's be like as fitted as standard? The whole projector is delivered pretty cheap, I would rather that than a plastic cased DJ special from Maplin I think.

I could then think about using it as a second projector for crowd scanning on smaller venues?

What do you reckon?

[The_Doctor]

how about a little <5mW green?

much safer, and still plenty bright in a dark room.

I'd start from that point. Go with single mode diodes. Get green right first. A stronger diode limited to low output can have a long life, and may be immune to dying from reflecting its light back at it (something you can guarantee a young child is going to try).

In a small room, narrow beams make sharper lines, better image despite lower power. You also get easy control of divergence, and a bit of that will make it safer at distances beyond a couple of feet. So go with the green diode, maybe 5 mW. Balance the other colours and choose them closer to the centre of the spectrum. Even with 635 nm you're going to get deeper red and better saturation than the best LCD or CRT display. Use long-wave blue. Avoid colours from the far ends of the visible spectrum because a child won't easily grasp that a dim deep red or blue often has much more power than a bright green.

Apart from the green diodes (and possible longwave blues), most of these things will be easy and fairly cheap to get.

Does anyone know whatever came of those TV-based RGB modules that were small and supposed to revolutionise small laser and TV display? They seem to have sunk without trace, and I can't even remember the name. If those ever show up, they'd be excellent for small safe projectors if run for low output. (But I don't know if such things will ever be single-mode TEM00 diodes, and they should be to work best this way).

In short, don't look for '100mW'. Go for quality. That way you can get away with much safer quantity. It will also be cheaper overall because there's nothign there you can't collimate well with just a single aspheric lens per diode. No need for tricks with PBS cubes and anamorphic prisms, etc..

EDIT:
Re crowd scanning in small venues, I remember that in a dark enough room with not too much smoke, fog or haze, a 20mW argon blue is by far the most dominant light in the room (assuming no other lasers are there), despite a large and well lit bar. You really don't need a lot of light if the beams are sharp. That point may get said a lot, but just seeing the proof tells you better than if everyone shouted it at once.

[mixedgas]

An alternative might be a 90/10 beamsplitter on the front and a OD2 filter.

10% of 1.5 watts is 150 mW from the 90/10 BS. OD2 knocks that down to milliwatts of total power.


Saves a lot of work building a new projector.

Just a thought,

Steve

[steviobee]

Cheers guys, all fair points, I was only thinking of around 100mW as I could also use it for some small gigs as well. But will probably go for a 5mW as suggested. And will just stick with a green for the time being.

I am also looking at probably DT20's for the small unit, what are these like? Are they okay for basic graphics or only really good for beams? Any other suggestions for scanners?

Just to clarify, any young laserists will be completely supervised, I'm not even popping out for the loo... But they do know to be careful with them.

[steviobee]

An alternative might be a 90/10 beamsplitter on the front and a OD2 filter.

10% of 1.5 watts is 150 mW from the 90/10 BS. OD2 knocks that down to milliwatts of total power.


Saves a lot of work building a new projector.

Just a thought,

Steve

mmmm, and I like that thought, could be a good option, where is the best place to get BS's?

[The_Doctor]

Maybe Edmund Optics if you want to avoid importing directly into the UK. Or Stanwax, if he has them.

[mixedgas]

mmmm, and I like that thought, could be a good option, where is the best place to get BS's?

One Stop Laser Shop may have 90-10s, so would Thorlabs or Edmund Optics.

Steve