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Does anyone know what causes these "ISO Line" stripes on a hologram?

My laser was warm, and my setup was in the usual way that produces bright holograms.
But over the weekend I've been getting stripes in all my exposures, like depth ISO lines into the picture!


Attemp 1:


Attempt 2:


The scene (just because it's spooky):

Cannot see the stripes you mentioned in the pictures and also not how your setup was, but often horizontal stripes occur when light enters the plate through the upper edge and makes internal reflections which lead to horizontal stripes . If that’s the cause it helps to paint the upper edge of the plate with a black marker

Hiyah!
Thanks for replying.

My "setup" looks like this:


Here's a clearer view of the stripey lines - this exposure had the lines closer together, I have no idea why!
Notice how they follow the models within the scene? They're like a window-blinds above shining their slatted light onto the scene!


I tried videoing them, they move in and out of the scene as I pan up and down. It's difficult to video the deep red.
https://www.youtube.com/watch?v=VBKeSCfY754


On this site, directly under the title "Picture of defects" is a picture of Micky Mouse with some glass edge issues. It doesn't look like my stripes, but it could be the light leak I have! I don't know - I wanted to point it out to see what you thought, as the images I posted where so muddy.
https://holowiki.org/wiki/Troubleshooti ... of_Defects

What confused me the most, is this shot - pre-bones and spider....... came out fine!
I think I may have just missed the top of the glass with the beam...


I'm looking forward to your comments!

I've ran out of plates, so I've ordered 10 more, maybe a couple of weeks to arrive.
With everything I've posted I'm hoping you say it's the light coming in from the top of the plate still.
I can fix that! I have black permanent markers at the ready. Other issues may be harder to fix.

Yes it’s obvious. The reference beam hits the plate from above and light is injected inside the plate from above. So you get internal reflections down the plate . Similar to the light guidance in a fiber . So take a black permanent marker like this one

https://www.hygi.de/edding-3000-permane ... -pd-104046

And paint the top side of your plate completely black before exposure.

The distance of the stripes depends on the incident angle of the reference beam. So I assume you altered the angle?

Thank you!

It's such an amazingly strong effect - I had no idea it would destroy the picture all the way to the bottom.

I recreated the laser source using advanced simulation technology, and was able to observe the lines appear just as they did on the hologram, AND the same distance apart which was also based on the angle of light hitting the plate. (Or more formally: The distance of the stripes depends on the incident angle of the reference beam.)
Yes I did alter the angle between exposures.

When my new plates arrive, I'll be drawing a black line on all the edges. I've already got a permanent black marker I use for blacking out the tops of embossed text of 3D printed stuff.

Thank you very much for your help!




Just one unimportant mystery remains...... ( I do like mysteries)
You know the hologram that did expose well - it used the same diverging blob the others did... yet somehow escaped the destructive interference from the edge light. I examined the top edge, and didn't see anything unusual - the emulsion was up to the edge, the glass cut was at what looked t be 90 degrees to the plate's normal, the edge was translucent.
Very odd!

Another question, why do you view it in red laser light? It’s. Denisyuk setup , should be visible in white light . Which film do you use?

Ah, the stock I'm using is 4 year old Litiholo C-RT20 emulsion between acetate sheets mounted on glass.
From what I can tell from my extensive sleuthing online it's (probably really incorrectly) the Bayfol® HX Film Holographic Photopolymer cleanly applied to glass sheets and cut into sections that are about +/-3% in dimensional accuracy. =)

With the age of the film, and to my eye, the image comes out much brighter and clearer with a red torch than using a full-spectrum point light source like a white LED. (my spectroscope shows a fairly smooth band of frequencies for the LED)

I think the orange light in sunlight and LED's reflects a slight smear around the bright parts of these particular old-stock hologram images. Subjectively - my eyes may be doing it?

Sadly - I know the Bayer filter on my smartphone has 2x as many green pixels as red and blue and it would make it more detailed to use a white light.... but with a torch they look kinda washed out.

With the red light - the camera's over-exposing the image and washing out much of the detail too.... I may try with my 12bit Canon camera to get a digital record of them.

I've got new film on the way, so with my marker and all the precautions I'm taking (as I mentioned in the original post...... tons of them!) I'm expecting much much better results.

The instructions that came with the hologram kit I started with never mentioned light bouncing around into the plates edges - and I never gave it any consideration. I'd seen a band across the top on some holograms I've made, but never the entire plate.

Those lines can form from reflections off the bottom edge too.

I like to use cardboard masks to block light from hitting the edges. Nothing to clean.

Really nice to see such good results with that material after four years! Especially with a darkish subject.

I think the "iso lines" you mentioned at the top may be the laser wasn't single mode for the exposures with the lines. I think those more experienced than me with similar laser modules will know if it's indicated by the orientation of the lines.

Personal preference, I prefer 3M 235 black Photographer’s Tape, 1/4” width for blocking edges from laser light scatter. Removes easily without residue and is opaque to laser light. Nothing to wipe off and no risk of diffraction interference from blocking card edges.
https://www.hisco.com/Product/00021200028373-31196

"..........no risk of diffraction interference from blocking card edges."

Ooo, what's that? I thought blocking the edges stops interference.