Engraving laser machine with a lens

[sml2010]

Hi
I have a laser beam(engraving laser machine) and then use a lens for focus the beam but my lens has a crack on the center of lens and when i use my laser in high power the beam diameter will bigger and burning area zone is bigger so:
1- Does the crack doesn't let the maximum focus?in law or high power?
2-1- I if i use two lenses with a exact distance, does the final beam diameter will be smaller than one lens?
2-2- Does the focus distance will be double?
2-3- Does the power will be double?
2-4- does a real distance(focus distance) between two lenses is necessary? if i put the second lens in focus distance of first lens, it will broken or not?

I am wait for your help.

Thank you

 

[CWatters]

The crack will probably be full of air which has a different refractive index to the glass the lens is made of. So it's possible to get reflections and scattering off the surface of the crack.

 

[mfb]

1- Does the crack doesn't let the maximum focus?in law or high power?

The crack is always a deviation from the ideal shape. Sure.

2-1- I if i use two lenses with a exact distance, does the final beam diameter will be smaller than one lens?

Not necessarily, but it is possible.

2-2- Does the focus distance will be double?

Depends on the lenses (in general: no).

2-3- Does the power will be double?

Energy conservation? ...

2-4- does a real distance(focus distance) between two lenses is necessary? if i put the second lens in focus distance of first lens, it will broken or not?

If the laser intensity is sufficient, you can even heat lenses (which are designed to let most light through it), sure.

 

[Andy Resnick]

Hi
I have a laser beam(engraving laser machine) and then use a lens for focus the beam but my lens has a crack on the center of lens <snip>
I am wait for your help.

You should replace the lens.