Diverging lens

[-bart-]

How consistent is the divergence over the entire scan area ?
Does the second lens expand the scanangle ?
Is there any distortion of the scanned graphics ?
Just wondering, because the distance between the telescope-lenses change proportional with the scan angle, which makes the mpe-circus a bit more compliated.

[mccarrot]

Totally. I have just changed the scanners to DT40s too, and I'm in the process of installing my scanner safety board.

Next week I'll do some new MPE comparisons to see how much more power I can safely use.

I have dome some measurements MPE measurements with the -2.7 lens

Test 1
Used equipment: RGB projector with 400mW whitelight after aperture with a averidge divrigence of aprox 1,5mrad

at 5 meter distance with NO lens in front of aperture I have to dim to 30% to be below 10MPE

With the lens in front of aperture I could got to 100% to be below 10 MPE

Test 2
Edisons RGY 500mW laserwave green 2 mrad, and kvant 600mW 640nm, balanced to yellow (so probbably 700mW after aperture but not measured)

At 5 meter distance to be below 10MPE we had to set it at aprox 25%, with the lens in front of camera we could go upto 65% in power.

So after 5 meter we could use aprox 3x the power with the lens applied.

[mccarrot]

How consistent is the divergence over the entire scan area ?
Does the second lens expand the scanangle ?
Is there any distortion of the scanned graphics ?
Just wondering, because the distance between the telescope-lenses change proportional with the scan angle, which makes the mpe-circus a bit more compliated.

Q: Does the second lens expand the scanangle ?

A: I have not noticed this


Q: Is there any distortion of the scanned graphics ?

A: there are 2 problems, 1. a laser with a bigger divrigence will get a much bigger beam as you can see in DOC's foto's, 2 a white line will be a RGB line after a distance. But when watching beamshows both problems are not really vissible.

Also remember, you will only use the lens in smal venues.

[ElektroFreak]

Sorry for the possibly dumb question, but if there is no gain in terms of scan angle, why are you using a lens? Are you looking for increased divergence for audience scanning?

[FourDee]

Bingo!
15characters

[ElektroFreak]

hmm. Makes sense! cool idea..

[mccarrot]

Sorry for the possibly dumb question

This does explain your laser-pointer fetish...

[ElektroFreak]

Really douchebag? Maybe it's time to drop that shit and move on like I did.. Unless of course you want me to follow you around the forum and post stupid shit whenever you ask a perfectly valid question? For being a super-suave, all-knowing laser "guru", you act like a 12 year old. Grow up..

I'm pretty sure I've proven myself here. If you don't like me, that's fine by me. The feeling is mutual, believe me. Maybe you could step up, be a man, and accept the fact that I'm here, I contribute, and I'm not going anywhere. Now I'll ask that you not respond to any of my posts, don't PM me, just don't talk to me and I'll do the same with you. Fair enough?

[Doc]

How consistent is the divergence over the entire scan area ?
Does the second lens expand the scanangle ?
Is there any distortion of the scanned graphics ?
Just wondering, because the distance between the telescope-lenses change proportional with the scan angle, which makes the mpe-circus a bit more compliated.

The negative lens does have the added bonus effect of a larger scan angle.

I haven't notice any distortion in the scanned pattern though I guess there must be, however this lens is for audience scanning with fans, cones and and shapes, not graphics; therefore slight distortion is inconsiquential.

The telescope effect is a none issue, in fact the divergence doesn't visibly change even if one holds the negative lens some distance from the projector (though the image size does).

Ian

[mccarrot]

@ -bart- I will take some of these lenses to the upcomming LEM to play with them, I have about 6pcs spare so if you are interested...

I will also use them in my audience scanning workshop.