I have this single beam transmission hologram made on litiholo photopolymer. It is the most basic bypass configuration, no mirrors to get lighting from the right position, no care at all on polarization/Brewster angle, plate edges not covered... All of which surely would improve the results.
But it does not look bad at all, but there are two features that bother me, and I'd like to understand what is causing them so that (1) I can avoid them and (2) I can better understand the underlying processes going on here... If possible I'd like you to help me learn if the features displayed below are caused by any of the above factors, by movement, by the laser...
This is the setup, light coming from the right:
This is the hologram as lit with the recording laser beam:
This is what I find that bothers me (other than the shadow cast by the object over the plate!) and I'd like to find the cause for those:
1) In the first photo there is a clear horizontal lines pattern, most visible on the bottom right of the hologram.
2) In the first photo there is a less clear but more disturbing horizontal lines pattern with lower frequency (wider dark/light bands)
3) In the second photo a vertical pattern similar to (1)
Could someone help me reason where do they come from? Vibration, internal reflections on the plate, mode hopping...? Thanks!
. As you can see in the first picture there is a grove along the base where the plate is 'inserted'. It is also resting on the left side onto the 'mirror' as you suggest; I think the set-up is pretty stable: the plate is secured on the grove, and leaning down about 20 degrees resting on the left support by gravity.