Correct spherical aberration from DVD-RW lens

[alessnilsen]

Hi! I'm working in a powerfull 650nm laser made from DVD-RW LD and optics. I have many beam splitters, some aspherical lens and spherical lens (the objective lens) and concave lens.

In my search for a lens that uses all the output light from the laser diode (to improve performance) I found the objective lens perfect for this, it have a small focus distance, but as all spherical lenses, it have the spherical aberration "bug", in my last test I got this:

I wanna get something like this:

How I can correct this? Thanks! :beer:

 

[JLSE]

If im not mistaken, those rings are part of the lens. To get a decent beam,
use that lens with the near flat PCX located under the pickup. I have a tutorial
here which is the same idea, obviously lens sizes will vary, but you get the idea :beer:

 

[alessnilsen]

Sure? I took off one of that lenses, it is perfectly spherical, I can't see rings on it.

I have that lenses here, I've tested it, but it has a big focal distance, some of the output from LD goes away from the lens:

I need collimate the beam better before it passes into that lens. But I don't know how.

 

[JLSE]

Most sled optics produce 'rings' when the small asphere is used, ive seen this in many
types for a few years. Looking at the first pic you posted...

This if im not mistaken is the smaller lens only on the diodes output.. Follow the steps
I show in that video, and you will get good power and lower divergence.

 

[alessnilsen]

Thanks for the info.

I think is a bit complicated, since english isn't my primary language, he uses a combination of the two lenses, can you make a simple picture illustrating what he did? So, I can reproduce here.

 

[JLSE]

Replicate what you see in the video which will most likely require that you experiment
with your individual set of lenses. Work at low power, and you'll figure it out.

There are also additional comments below the video where some questions were
answered on the lenses used.

 

[The Lightning Stalker]

It was pretty long winded, but this is the lens arrangement as I understand it:

 

[alessnilsen]

Thank you!

I'll play with my lens to see the result.

One small question, what is the glue used in the sleds? I think is epoxi resin.

 

[SKeeZ]

buck up and by a g series or even a 3 element. thats my suggestion. there is no real good way to remove those rings.

 

[alessnilsen]

Yes! No way!

Here, I found a patent about those rings: Objective lens with the diffractive surface for DVD/CD compatible optical pickup - Samsung Electro-Mechanics Co., Ltd.

Quite frustrating!

 

[alessnilsen]

So, a DVD lens have the rings to work with 780nm and 650nm, a CD player lens that work only with 780nm will have those rings too?

 

[The Lightning Stalker]

Yes. I don't think they bother with aspherics in optical drives.