Handmade holograms are really weird

Summary by Krater

This video explains the optical mechanics of scratch-based holograms on acrylic sheets, demonstrating how depth, viewing angles, and image distortion are controlled by the arc of the scratches and light source positioning. The video concludes that creating complex 3D holographic shapes by hand requires precise curve geometry, which can be simplified by CNC machining.

From the video

Answers: How do scratch-based holograms work and how can you make them?

• scratch holograms
• acrylic etching optics
• stereogram holography
• Borromean rings geometry
• CNC etching vs hand scratching

What it concludes

• Scratch holograms create a 3D illusion because left and right eyes see glints from different points on the scratched surface.
• Straight scratches cause glints to appear at the same depth as the light source, while curved scratches create varying depth perception.
• The arc of a circle is the wrong shape for etching most hologram shapes, except under specific circumstances where the image rotates once per full circle rotation.
• Using CNC machining to generate the etchings based on a 3D software model overcomes the immense difficulty of calculating complex manual scratch depths and pivot points.