Laser optics producing images?

[ojwhc]

I was looking on AIXIZ and I noticed in the lenses section they had lenses that produced images, not just geometric shapes, from laser beams? Examples would be the no smoking sign

and the peace sign

Does anyone have any idea how this works? I'm just really intrigued. Also apologies if this has been previously covered, i did search and have a look through but i couldn't find anything.

Thanks in advance

 

[ojwhc]

No one got any idea?
Cheers

 

[WizardG]

Those are essentially holographic diffraction gratings. They're very similar to the 'star cap' diffraction gratings but instead of a regular (in the orderly and repetitive sense) pattern these have a pattern generated from the interaction of a reference beam and an 'image' beam. When you shine your laser through them it acts as the reference beam which is diffracted to reproduce the image beam originally used thereby projecting a pattern or 'image'. This is a quick-n-dirty explanation. For more and more detailed information try searching wikipedia for holography, hologram, diffraction grating, etc.

 

[ojwhc]

Ahhh amazing cheers. Yeah I understand the basic principle of diffraction gratings, but i thought they were always regular shapes and distributions. Thank you, i'll read up on it

 

[ojwhc]

Do you know of anyone who will produce custom holographic diffraction gratings?

 

[BShanahan14rulz]

Now we're talking! How do we go about making custom versions of these with a DIY process?

I've read up a wee bit on very simple transmission holography, aka shoebox holography, could we do this using typical hologram films/plates and a similar setup?

 

[WizardG]

"could we do this using typical hologram films/plates and a similar setup? "

The short answer is yes. But it gets a little involved. A normal hologram produces a 'real' image. You'll need to make a second order 'hologram of a hologram' to produce one of these gratings which produces a virtual image.

 

[ojwhc]

I don't want to create my own 3d hologram though, just project my own 2d shape?

 

[BShanahan14rulz]

http://physastro.pomona.edu/wp-content/uploads/2012/09/Wendt.pdf < found this nifty link, with nifty pictures! Not dumbed down enough for me, but it does a good job explaining generally how interference creates a wavefront, almost like a virtual wavefront that traces back to where the imaged object was originally (or something like that). Well, it makes sense in my head (As much sense as a thought in my head can make.)