How are holograms possible?

An explanation of how holograms record 3D scenes on 2D film using wave diffraction and phase differences.

3d scenes on 2d film, and a diffraction lesson along the way. Instead of sponsored ad reads, these lessons are funded directly by viewers: 3b1b.co/support An equally valuable form of support is to share the videos. Hologram credits: The Microscope is by Walter Spierings, 1984 Donations Hologram by Cherry Optical Holography Lucy in a Tin Hat is by Patrick Keown Boyd, 1988 The Star Wars-themed Direct-Write Digital Holograms were produced by Zebra Imaging. The 'Shakespeare' embossed animated integral hologram was made by Applied Holographics. Walter Spierings, who did the microscope, is from Dutch Holographic Laboratory. He wanted me to let you know that anyone should feel free to approach them when it comes to producing holograms, they do a lot of innovative things with the medium: www.holoprint.com Thanks to everyone who helped with this project: Paul Dancstep, for help writing, and for all the 3d modeling Craig Newswanger and Sally Weber, for making the central hologram shown Kurt Bruns, for the artwork of Dennis Gabor Phoebe Tooke, Wayne Grim, and Rick Danielson, for filming at the exploratorium Quinn Brodsky and Mithuna Yoganathan, for footage of lasers through diffraction gratings Vince Rubinetti, for writing the music Cliff Stoll for the Klein Bottle Small correction: After the algebra in the end, I say "We don't even make assumptions about R", but that's not quite true. To treat |R^2| as some scaling factor in the expression |R^2| * O, it matters that the amplitude of R is approximately constant around a given point. Gabor's Nobel Prize lecture: nobelprize.org/uploads/2018/06/gabor-lecture.pdf A few resources we found helpful for this video Seeing the Light, by Falk, Brill, and Stork amzn.to/3Ngdiqh Practical Holography, by Saxby and Zarcharovas amzn.to/3ZR2MNN Principles of Holography by Howard Smith amzn.to/3ZOihFZ Timestamps 0:00 - What is a Hologram? 3:28 - The recording process 11:45 - The simplest hologram 17:12 - Diffraction gratings 25:15 - Reconstructing the simplest hologram 28:24 - Conjugate image 31:11 - More complex scenes 35:58 - The bigger picture of holography 38:27 - The formal explanation SEV1: youtu.be/iBYotKfYRQ0 ------------------ These animations are largely made using a custom Python library, manim. See the FAQ comments here: 3b1b.co/faq#manim github.com/3b1b/manim github.com/ManimCommunity/manim/ All code for specific videos is visible here: github.com/3b1b/videos/ The music is by Vincent Rubinetti. vincentrubinetti.com vincerubinetti.bandcamp.com/album/the-music-of-3blue1brown open.spotify.com/album/1dVyjwS8FBqXhRunaG5W5u ------------------ 3blue1brown is a channel about animating math, in all senses of the word animate. If you're reading the bottom of a video description, I'm guessing you're more interested than the average viewer in lessons here. It would mean a lot to me if you chose to