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No image with red laser pointer, complete n00b.

Posted: Mon Sep 11, 2023 6:19 am
by thedom97
Hi all,

I am trying to do a simple reflection hologram. I have purchased several laser pointers on ebay, and 3d printed some jigs to hold the laser pointer and the film upright. The film I am using is the litiholo self developing C-RT20 film.

The laser modules I am using are just from ebay. 5mw red 650nm. They started with a line lens, but it screwed off to give the laser a somewhat flashlight shaped beam, which from my understanding is correct.

Here is an album with my setup as well as results in direct and indirect lighting.

I exposed for 4 minutes, and as you can see from the line across the bottom of the film, it did in fact get exposed (i.e. the darker part was obscured by the holder and didnt get exposed).

Anyone have any tips? Thanks in advance.

Re: No image with red laser pointer, complete n00b.

Posted: Tue Sep 12, 2023 8:47 am
by Din
The jig to hold your laser pointer and the plate holder seem to be on carpet. You need a solid surface - a metal plate, for example - that must be secured so it doesn't rock, ie it sits solidly. The plate holder doesn't seem to have anything securing the plate. The object seems to be sitting on the plate holder with no way of securing it. The laser must not be pointing directly at the plate, it must be offset at some angle (most holographers use about 50 - 60 degrees), otherwise the only way to reconstruct the hologram is from directly behind you. The reconstruction angle must be the same as the recording angle. All these factors will cause motion for a 4 minute exposure, which is relatively long. If there is any relative motion between laser - plate holder - plate to less than half the width of a human hair over a 4 minute interval you won't get a hologram.

I would suggest that you find a solid floor such as a cement basement or garage floor. Then get a metal plate and place laser, plate holder and object on it. Then use hot glue to secure the laser, plate holder and object to the metal plate. If you place the metal plate on a bed of sand the metal plate will also be secure. I would also find a way to secure the plate in the holder - if you tap the plate with your fingernail while in the holder it must not make a ringing noise. Don't forget to offset the laser from directly pointing to the plate.

The final point is that the laser may not be coherent. To test this, I'd suggest simply gluing coins to the back of the plate holder - not too strongly so you can pop the coins after exposure.