(The Thought Emporium) has long been fascinated with holograms in many different ways. His current ultimate goal is to create holograms out of chocolate, but along the way he has found another interesting way to manipulate light. On his way to the chocolate hologram, he is exploring a unique way to project hologram-like images using special diffraction gratings, a laser and a few lines of code.
There is a lot of background information that (The Thought Emporium) has to go through before explaining how this project actually works. In short, it is a type of “transmission hologram” that does not use a physical object as a model. Instead, it uses diffraction gratings, which are materials shaped to split light in specific ways. After some discussion, he demonstrates the creation of diffraction gratings using film. Certain diffraction patterns, including blocking the entire light source, can actually be used as a lens, as the light bends around the blockage into the center of the shadow, where there can be focal points. From there, a special diffraction lens can be built.
The diffraction lens can be shaped into any pattern using a bit of computer code to calculate the diffraction pattern for a particular image. It is then transferred to film and when a laser is pointed at it, the image appears on the projected surface. Diffraction gratings like this have a number of other uses too; the video also shows a specific pattern being used to focus a telescope for astrophotography and some others have used them in the past to create the illusory holographic chocolate that (The Thought Emporium) is working on.
