P73 and 2FL lens

[neutrino]

Hi all,

I am getting some stuff ready in preparation for the cylindrical lenses arriving from Dave.

I have his adjustable mounts with the P73s in them. I have glued (carefully) the 2FL lenses in to their barrels and mounted everything with attached Flexmod P3.

Does any one have any photos of what the beam should look like coming from the 2FL lens before going through the cylindrical setup? I'd love to get this dialed in ready for when the rest of the bits arrive.

Thanks in advance

Rich

[planters]

The best end result, when you later add the cylinder pair, will be to produce the most symmetrical far field stripe. The diode should be rotated to produce a horizontal stripe with the multimode stripes evenly distributed above and below the main central stripe and the lateral wings extending the same distance each side of the stripe. Focus to the highest contrast lines, but you will need to tweak this when you add the extra glass later. The effect of a movement of the diode will be to produce an opposite shift of the far field components. This takes time because the effect of apparently small adjustments and small changes of the raw far field will be significant improvement in the final result. The cylinders are easy in comparison.

[neutrino]

The best end result, when you later add the cylinder pair, will be to produce the most symmetrical far field stripe. The diode should be rotated to produce a horizontal stripe with the multimode stripes evenly distributed above and below the main central stripe and the lateral wings extending the same distance each side of the stripe. Focus to the highest contrast lines, but you will need to tweak this when you add the extra glass later. The effect of a movement of the diode will be to produce an opposite shift of the far field components. This takes time because the effect of apparently small adjustments and small changes of the raw far field will be significant improvement in the final result. The cylinders are easy in comparison.

Awesome, just what I needed. Thanks

[CDBEAM]

All optical adjustments associated with the P73 take some time to dial in.....but the result is very much worth the effort !!!!!! Some of this is a repeat of Planters very good post !!

Yes...the first thing you must do is set the collimation lens to infinity. Thus results in a bar geometry....with some wings on both sided of the bar. The wings are of about equal length to the bar. Adjust the collimation lens to produce the thinnest bar possible.

Next....rotate the diode so that the bar is parallel with your optical plane/mounting platform. This takes some time as the bar really needs to be parallel so the cylinderical lenses can magnify the slow axis correctly. You need to be adjusting the diode so the bar is parallel to the horizon...in the far field !!

Next you are ready to add the cylinderical lenses. The distance between the Plano Concave and Plano Convex needs to be spot on !!! .25mm plus or minus will deliver a more divergent beam !! I only have experience with the 6X Cylinderical set.....so I cannot tell you what the placement between the Plano's will be!! Take your time with this placement as it will reward you with less than 1.0 mRad in the farfield.

The final decision is how far to place the set of cylinderical lenses from the output of the collimation lens. This distance involves a trade-off !! The closer you place the cylinderical lens set...the greater the farfied divergence....but the smaller the nearfield geometry becomes. And....the further away from the collimation lens you place the cylinderical lens set...the lower the farfield divergence...but the greater the nearfield geometry becomes. Life is full of trade off's !!! It all depends on the size of your scanner mirrors. That will drive your positioning !!

Another point...the beam should enter the Plano Concave Plano at a 90 degree angle and dead centre of the lens. Also, the beam should the dead centre of the plano Concave
as it leaves the lens.

If done correctly, the resulting beam is beautiful....just needs a little masking to clip the wings.

Have fun !!!


Beam Out

[neutrino]

Thanks for that detailed description CD. It will help massively, I can picture it all in my head so now just need the parts to put it into practice!

Cheers
Rich

[planters]

CDBEAM is correct, but you will find the cylinders to be much easier and intuitive. One major trick and you must try this. Do the optical alignment of all the optics after the 2mm collimnator with a lot of fog. I mean thick fog. If you use very thick fog and observe from dead on above (use only one eye) then you will do a much better job and quickly. To test this just try it first without the fog and see how good you did once the fog is added.

[neutrino]

Thanks for the tip. I'll give it a go. TNT should be here in a week or so.
I'll report back with my progress.

Cheers
Rich

[CDBEAM]

Two additional points; IMHO...the " Holder " that you use for the cylinderical lenses needs to have a channel for the Plano Concave lens to slide ft to back. If you are using Dave's Cylinderical lens holders...perhaps mount two parallel bars/strips of Ally on either side of both lens holders. With such a simple add-on...you will be able to retain the Convave lens holder centering relative to the Plano Convex lens/lens holder. Then you can slide the Concave lens and holder +/- along the optical path....and not be dancing all around with it.

Next comes the challenge of adjusting the LD in the LSP adjustable diode mount. A method here is to have the four (4) bolts that place pressure on the LD capture plate...just with a very SMALL amount of pressure. This allows the LD to be positioned in both the radial direction and the X-Y location....and NOT have it move back to where gravity wants to move it !! The tension on the bolts must be JUST right....not too much and not too little.

Have Fun !
Beam Out

[neutrino]

So my lenses and holders arrived from Dave so it was time for a little play.

This is what I managed to knock together so far.

My mini breadboard:


Two Flexmod P3's. One for the red diode and one for the blue diode. I am using a 3 element lens on the blue and Dave's correction optics on the red. The micro flexmount will hold a piece of dichroic glass reflecting red and passing blue:


This is the output at about 18 feet. The blue is 25mm across. I didn't have time to do any further tweaking but am pretty impressed so far:


I need to fire the fog machine up and do some more adjustments to fine tune it. This is only going to be for beams with 20K scanners. I am going to build two identical units.

Cheers
Rich

[planters]

Thanks for the pics, they help a lot in clarifying the discussion. First of all, if you are impressed with these results then you're hooked. With a few maneuvers you will be able to improve on this by nearly an order of magnitude! Without beam shaping optics or serious defocus the blue should be a stripe with an aspect ratio of around 6 to 1. The red shows the multimode stripes on only one side and so yo need to reposition the diode to better balance these.

What are the near field beam measurements?
You might want to put a small piece of heat shrink tubing on the exposed solder joints near the diode because as you manhandle these with alignment adjustments these may cross.

Your build looks neat and stout. I can't wait to see more.