445nm lensing options - discuss them all here!

[mccarrot]

Doesn't this increase the divergence?

[buffo]

As pictured in the link, yes it would. However, my idea is to build a 1:1 collimator. That is, the two lenses have the same diameter and focal length, and they are positioned exactly double the focal length apart. The pinhole is initially positioned in the center, and then you move it towards the first lens to begin masking the beam.

With this arrangement you don't change the divergence at all, you just "punch out" the center portion of the beam (which, presumably, has most of the power anyway). Thus you have good divergence and a smaller initial beam diameter (so it will fit on your scanners).

Adam

[badger1666]

the diode spec on the blues from what i have read so far is about the same as a 635nm getting that beam small ain't easy, they all still have a fat beam so i dont think we can expect to get any better with these blue's unless you got alot of $$$$ to spend on optics
i think the best us hobby guys will get is a 5x2mm beam @ 2mrad , but i could be wrong
unless someone finds new combination of lens that dont cost an arm and leg

[mccarrot]

looks like we definitely have to do some beam shaping. I'm trying to get the cylindrical lenses asap.

[taggalucci]

Not that I know much about optics, but having searched around and read various threads here about correcting fast axis divergence...

I found this post from "survey", though I couldn't see how successful this was.

From something "yaddatrance" mentioned later in the thread (here), I wondered whether a GRIN cylindrical lens array would be suitable e.g. like this.

Additionally, correction of the elliptical beam profile using anamorphic prism pairs looks to be quite successful in Andy's setup

Does anyone yet have the exact specs of the diode window dimensions and the divergence angle for each axis? I take it these are the important factors in determining focal length and NA values. Anything else?

[rfourt]

im a real noob in optics but wouldnt the same techniqe i used for my bluray combine´s work to impromve the beams width.

These lenses i bought from Edmunds and didnt cost much and also the lost was perhaps 3-5% per lens.

[Doc]

What about using a tilted lense to square up the beam?

[dave]

In reading about the 405-G-2 lenses on LPF, it appears they don't do too bad a job, but have a lot of 'noise' on the beam in the form of stray artefacts and haze (they surmise this is from internal reflections). In a projector I don't think this would be too much of a problem as this would never even make it onto the galvos.

The 405-G-2's gave me about 3mrad divergence.. A little on the high side to me, although, they will probably work fine if used in a projector with 635nm red..

[norty303]

The 405-G-2's gave me about 3mrad divergence.. A little on the high side to me, although, they will probably work fine if used in a projector with 635nm red..

Was that on 405 or 445? What sort of beam shape did you manage to get?

I did have a 650 with high divergence and I didn't find it too bad, so I might live with 3mrad for a bit. I guess at some point someone will find the optimal solution of specs vs cost, and then everyone will jump on it. It's just getting to that stage in the meantime!

I don't have space for exotic telescopes so a very compact solution is going to have to suit me.

[dave]

Was that on 405 or 445? What sort of beam shape did you manage to get?

It was with a 445nm diode - one of these. Beam at aperture was around 4 x 1 ish mm.. The 405g-2 is great with 405 and 660 for that matter

And I managed to remove the diode from the lens tube without damage either