Pepper's ghost gets its name from the 19th century scientist who created an illusion of a ghost in a room using special projection technique. More information is available on Wikipedia. In Pepper's ghost effect a projection surface at 45 degree angle is projected with a high resolution video from an overhead suspended / underneath hidden display medium. The projection surface is a very special purpose surface with coatings on it to allow a certain amount of light to pass through the surface and a certain amount to reflect back. By involving multiple techniques to smartly project the video content on the projection surface a lot of interesting visual experiences that feel like hologram can be created.
The technique has been used by different companies to create various interesting visual effects and many companies have also taken patents on their specific type of projection material, assembly, design etc. The technique is also termed as holography by a lot of people even though these are not real holograms where the image does not turn and is not projected in air like in real holograms, but always need a projection surface to project on. Even though one might feel the technique is simple getting it to work near perfect is a lot of optics experiments at play with smart materials and related work. Hence, if you think you can just build some thing as sophisticated as HOLOFIL at home, you are out of luck unfortunately, as HOLOFIL uses some carefully selected proprietary components and materials to give you the ultimate visual experience with a lot of scientific research behind.
We do not expect real holograms to make an appearance any time in near future. So the future where you will have real life Iron man movie type holograms floating around you in air, are still far far away. Closest what we are getting are head mounted augmented reality types of devices which still need a projection medium near eye to create interesting experience by putting virtual objects in real world thereby blending the physical and the virtual world. The so called Light-field displays also use decades old lenticular strips based technique to create glasses free 3d effect. See more on that in the next blog post in this blog. The others are volumetric displays which use different volume based projection techniques. Most of these displays are very primitive and suffer from issues such as very low resolution, limited types of content that can be visualized, technical challenges in terms of the amount of data that needs to be handled to create a volume etc. These kind of displays will take a good time to be commercially viable in a real sense.
So Peppers ghost based holography will continue to dominate market in various forms and flavors as long as the real life holograms are missing. Pepper;s ghost has relived itself again and again and we expect it to continue in foreseeable future at least. Long live the Pepper's ghost based holography and various holography devices based on it.