Whitelight DPSS - doing it the right way...

Hi guys,

I've seen a fair few pics of 'professional' white light projectors floating around now.....

One thing that is apparent from some of them is that the manufacturers have not taken into account the different divergences and beam sizes of each colour...

In experimenting with mixing our arctos red and lambdapro green, it was horribly obvious that the green laser had a much smaller beam (with higher divergence - the green caught up to the red at about 13 metres away from the lasers)

I believe all thats really required to fix this is a couple of lenses to expand the green beam so that its divergence is lowered... however thorlabs charge US$500 for a beam expander, hb-laser charge a few hundred euro for one...

does anybody know of a cheap, easy, reliable way to provide adjustable expansion on an already collimated beam ? Do u have any sources/manufacturers i should be checking out ?

Thanks,

Aijii

What i do is cheap but it works:

I get all the lasers with matching 1 or 1.5mrad divergence. The way i see it no ones going to notice the 1mm size difference at 20 feet. Sadly with lasers your lucky to get anyone to really notice. Name the last time you got a gig from somoene in the audience. heh.

Had an idea about installing a small piece of fiber (< 1 meter) inside the head and mix the red blue and green through a trichro and recollimate at the end for a "perfect" white spot however the power loss was completely unacceptable.

Thorlabs pricing is a joke only rivaled by edsci and newport. Almost makes me want to buy the machinery to coat my own optics. Wants aside: Ive had pretty good luck with chinese manufacturers. Be careful with them though. Make sure you list every single specification down to the individual coatings and scratch/dig otherwise they will save money everywhere they can and you get a really terrible piece of glass.

They are good at fallowing directions and taking money. Thats about it. ;)

Yeah i thought about that..... however i haven't really found the chinese specifications on divergence to be that true either.....

I have no idea what sort of specs i'd need to specify... short of focal length and ar-coating wavelength...

Most chinese manufacturers list divergence as <Xmrad. anything less than X is still classified as "acceptable" I always measure everything when i get it in to make sure everything works out allright and if i absolutely have to ill go inside the laser head and make adjustments to the final optical stages to get everything to match up better. Its a pain, but its better than the alternative.

When looking at chinese manufactures for optics see their catalog and look for specifics listed. scratch/dig 20/10 is pretty damn good. also flatness is helpful, its usually listed in (lambda symbol)/X. where X is how flat is is compared to the source wavelength(usually 632.8nM) And remember if its listed as "option" its not included. Makes me wonder who buys polarized beam splitting cubes without coatings... Strange place these manus are.

IF you need any help with this stuff feel free to ask and/or send the manus page my way. Im pretty good at decrypting "Marketing ciphers"

;)

does anyone know the correct ratio for RGB color balance and what the best frequencies for each color are. Obviously 532nm is the best option for green, but how about blue (488nm ?) and red (658nm ?)

Since posting I have found this document which describes colour balance well.

http://www.laserfx.com/Backstage.Las...Archives4.html

Hi, Stormy, and welcome aboard on the boards....glad to have ya.

Also glad you found that article again...I keep losing track of where I put what on this machine :oops: ...

At any rate: thanks, and welcome.

hi stormy... fancy seeing you here ;)

i'd say you'd need at least 4 or 5 times the amount of 532nm for a 650nm red source... more if its any deeper. I'd use the same for blue.. and 457nm is so much nicer than 473nm...

Hiya . I havent seen you for ages.