Lense/Optics Simulator

Here is a screenshot I took when using the 'optical bench simulator'.
I'm not sure whether this has already been posted or not, and I wasnt sure wether to put this in the 'Help&Tutorials' or 'Optics' section of the forum. However, I have been searching for something like this for ages and it helped me alot.

As you can see, you dont need to expand the beam to decrease the divergence.
In fact - theoretically - you can align lenses so they decrease beam diameter as well as divergence. A beam with 1mm diameter and 0,01mRad would be pretty awesome on a normal laser.
Unfortunatly I have never seen anybody do this - maybe I could inspire somebody.



However, here is the little programm:
Optische Bank - Physlet Applet by W.Christian

And for more professional users there is a freeware called WinLense3D Basic which you can find here. It is very complex - if you take time and learn how to use it:
OpticalSoftware.NET

If you are more interested in optics and beam divergence then check out the LPC Laser Parameter Calculator.

Nice looking program and all, but you're missing out on some physics if you think you can use a lens to decrease both beam diameter and divergence simultaneously.

pullbangdead said:

... but you're missing out on some physics if you think you can use a lens to decrease both beam diameter and divergence simultaneously.

Click to expand...

I never said that. I think you have to use two lenses.

However, I know its not a professional programm. Unfortunatly I dont have conkave lenses to try out the experiment myself.

I don't care how many lenses you use. If you decrease beam diameter, you will increase the divergence. They are inversely proportional to one another, and that inverse relationship can't be broken with lenses.

Don't get me wrong, it's a cool little applet for learning about lenses, I'm enjoying playing with it.

It's a neat applet, but it doesn't actually make any inference about the divergence of the beam*. But your example shows how you can make your own beam expander or condenser, and that's pretty nifty!




*(well, actually, it infers that the smaller beam diameter results in a more divergent beam, as the top two rays are rendered as a stairstep, while the input rays are all parallel)

Does the program just use geometrical optics, or does it consider wave optics? 1mm beam diameter and 0.01mrad sounds impossible unless your wavelength is deep in the UV.

Bluefan said:

Does the program just use geometrical optics, or does it consider wave optics? 1mm beam diameter and 0.01mrad sounds impossible unless your wavelength is deep in the UV.

Click to expand...

Geometrical optics.

divergence can only be explained by wave optics. Geometrical optics considers light to be like rays with point like precision, just as the name says: geometrical. For systems much larger than the wavelength, this straightforward line behaviour is fine.

One step deeper is considering light as a wave, just like waves in water. Taking a finite size aperture will cause the waves to bend around that aperture. The waves will slowly (or fast for a small aperture) expand and become larger than the aperture. You can't make a wave in the ocean and expect it to keep it's size across the ocean. The smaller your wave, the sooner it will end up everywhere.

So an aperture will limit the area were a light wave can emerge from, and the larger your aperture, the more straight your beam will travel. A finite beam size will act like an aperture in the same way. A larger beam thus will mean a lower divergence. A tiny aperture will spread out fast. This typical wave effect is called diffraction.

Fourier optics is very usefull to get a feeling for what light does, you get a sense for spatial/angular behaviour of light. More complicated theories also consider the electromagnetic properties of light, and even more thorough is quantum optics, but that stuff usually isn't needed for simple optical system. But for now, see the attachment, it's from a ripple tank to demonstate the effect of the wavelength vs aperture size. In this case the wavelength is made larger relative to the aperture, but the aperture also could have been made smaller. It's copied from the book Optics by Hecht, a very nice book.

The beam used in the program likely has zero divergence to begin with.