Mini-Axial Box V.2 Troubleshooting

Light is somehow getting in, probably from reflection from within the box or maybe from another source. Can you show a pic of the box? How are you absorbing the light that goes through the glass (on first pass) to keep it from reflecting back and shining up to the sensor?

The old box (first) is super narrow, fitting only a nickel. Everything is lined with black felt, even the top. Nothing is set on the new box yet. I am still getting the cardboard rails even and set to 45 degrees. I made it from the black cardboard backing of a picture frame. There is a slight gap on the side, but draping a dark cloth over the assembly produced no change in the picture. The front is wide open, unlike the other box, but it fits right up against the light tunnel.

Could it really be just the reflection of light from the back of the box?

Better. Probably still too much reflection from the inside of the box. I'd suggest removing the side opposite the light source and adding a bigger/longer "black box" to absorb the light transmitted through the glass that can then reflect back to the glass and up to the lens.

Edited to add: what is your light source? You can improve the size and uniformity of the sweet spot by using a small ringlight instead of a spot light.

I can't think why there would be a negative effect. A long tunnel with absorbing material is an ideal absorber.

Don't worry about polarization. That's a rabbit hole few have emerged from.

You might try covering the opening in front of the coin with tissue. Then move the light farther away from the box. This will give a lot better diffusion and uniformity versus covering the light itself.

I did experiment with the light bulb uncovered, and the filter closer to the box opening. I noted a ring light as a possibility for my next Amazon order.

The long tunnel isn't feasible on this build of the box—the sides were held together by gluing four folded flaps into the back. I decided to do a new build of the box in the coming weeks. It wasn't wide enough to accommodate a 2x2. It's also a pain to remove the coins without touching them repeatedly or scuffing them on the felt. I think what I really want is just a pane of glass at a 45 degree angle, held by stiff hanger wire anchored to a base, and a top target hole to obscure the iPad/camera behind black felt. That cuts all side and rear reflections by not having a side and rear.