Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers



Anyone remember the liquid fan diffraction grating at NOVA LASERS ?

paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
16,043
Points
113
This is from three days ago. If you take a photo of the beams coming at you from the same distance as BowtieGuy did you will see more than three beams. It is only because you limit the aspect of the photo that only three beams are seen. The fact is you can see beams for nearly 180 degrees as they are coming at YOU (the camera). It is hilarious that you show three dots on a wall with the outer edges cut off so the rest are not there. I am done with this. Post all the nonsense you wish, I will no longer respond.
 



smallfreak

Member
Joined
Aug 14, 2018
Messages
94
Points
18
Maybe I can throw in my 2ct here. While I'm new to LPF, I'm not new in the physics involved.

Take a quick look at *this explanation of the diffraction grating formula*. It breaks down the complicated looking math into some easy triangulation. The essence is: The lower the spacing (higher number of lines/mm) the wider the angle of the diffraction orders.

The diffraction angle certainly cannot exceed 90°, even with a theoretically perfect grating with a totally flat surface profile. If you use the *calculator on this page*, you can see that a 1000 lines/mm grating "should" produce a second order spot as long as the wavelength is below 500nm - where this spot would be exactly 90° to the incomming beam. With 488nm this second order beam should be 77° off axis.

It now depends on the physical parameters of the actual grating, whether a beam at this angle may be blocked geometrically. A square shaped photographic grating surface hardly gets a fan angle wider than 90° in total, so every higher order with deflections greater than 45° get lost. The same is true for a symmetric triangular surface.

A high quality etched sawtooth (Echelle) grating will give you more usable angle as the harmonics are favored asymmetrically in one direction.

With above linked calculator you can find that a 250 lines/mm grating gives you one beam roughly every 7° off axis with a 488nm Laser, which fits 5 harmonics into ~45 degrees to each side totalling 11 rays.
 
Last edited:

diachi

Well-known member
Joined
Feb 22, 2008
Messages
9,741
Points
113
This is from three days ago. If you take a photo of the beams coming at you from the same distance as BowtieGuy did you will see more than three beams. It is only because you limit the aspect of the photo that only three beams are seen. The fact is you can see beams for nearly 180 degrees as they are coming at YOU (the camera). It is hilarious that you show three dots on a wall with the outer edges cut off so the rest are not there. I am done with this. Post all the nonsense you wish, I will no longer respond.
Paul, *you* are wrong. Cyp is correct. You don't need pictures to prove it. Pure math alone proves that he's right.



1000l/mm is a line spacing of 1um of course.


Now, will you accept that you're wrong and move on?
 
Last edited:

Cyparagon

Well-known member
Joined
Sep 12, 2007
Messages
9,595
Points
113
you will see more than three beams.
Can you prove it?

I've got half a mind to start pay-palling people money for gratings so they can ALL post pictures and tell you you're wrong. The longer your arrogance and stubbornness resists this basic fact, the sillier you look in the end.
 

RedCowboy

Well-known member
Joined
Jul 10, 2015
Messages
8,160
Points
113
Can you prove it?

I've got half a mind to start pay-palling people money for gratings so they can ALL post pictures and tell you you're wrong. The longer your arrogance and stubbornness resists this basic fact, the sillier you look in the end.
Don't be so hard on yourself there Cybergoon, you have at least 3/4 of a mind I would bet. ;)
 

Cyparagon

Well-known member
Joined
Sep 12, 2007
Messages
9,595
Points
113
Eh, some days. I take what I can get.

At least I can count to three.
 

RedCowboy

Well-known member
Joined
Jul 10, 2015
Messages
8,160
Points
113
ha ha ha

I can count to three, watch.........one, two.............what was I saying ?




Oh yes, one......one......

 
Last edited:




Top