Recently I was interested in building a hologram projector to view the restaurant menu in 3D. This quest began when I ordered some fancy named food in the restaurant and ended up having rice and some boiled vegetables for dinner. :D. So basically that got me thinking is there a more cool way to display the food in 3D and make the experience more appealing.
The below image is one of the commercial grade hologram projectors in the markets priced from (2000$- 8000$). In technical terms is not a true hologram projector but an illusion of reflection.
In this article, I’ll talk about how to make something similar and the challenges on the way.
The above image shows the final device built. In this article, I’m going to talk about the technical difficulties I faced when building this hologram projector.
1. The Material to use.
There were specialized hologram glasses commercially available but I could not get a hold of those from Sri Lanka. So initially I resorted to a CD cover. But using such material did not give a good look. Then I resorted to mirrors, but those are very fragile. I wanted something transparent and strong and finally found that magic material, which is perspex glass.
2. The lighting condition.
One of the biggest problems of making a commercially viable hologram projector is the lighting condition. In order to get the holographic look the glass(pyramid) should be transparent as possible. But when the glass is fully transparent for even a small surround light, the hologram fully disappears. So the solution is to use a tint.
This astonishing effect will get lost if the brightness of the surrounding light increases. So it’s hard to keep these devices in a fully lighted environment.
3. How much tint to use?
First I wanted fully tint the glass, so I bought a perspex sheet with almost 80% tint, which means 20% transparent, and from the video, you can see the effect, it works like a black mirror.
The appealing nature of the hologram comes when the glasses are more transparent, but at this point, it’s like watching a mirror. And I could not find a perspex sheet with 20% transparency so I got the car window tint sheet and pasted on the perspex and it was very effective. We were able to observe the hologram in normal lighting conditions too.
4. So how does the commercial hologram projectors solve this issue?
They also use this selective tinting and they use specialized perspex/glass made for this exact purpose. Some tackle the issue by designing the hologram stand in a way that will give less light inside the pyramid. Some have added spotlight inside the pyramid and used tint in the range of 80%. The spotlight tactic is good for product marketing (showcase a product in 3D etc).
The below image shows a commercial hologram projector. It uses slightly tinted glass and a spotlight from the top to tackle the lighting issue. The hologram projector also uses the structure of the device to gain more artificial darkness.
5. The height (View Area / Height of the pyramid).
Another main problem is the height of the hologram projector. If you want a considerable view angle then you must use a display similar to 42 inches. So if we want to make a tabletop version then the view area will be really small because of the way the pyramid should be placed.
From the above image, you can see how much of a space it consumes to give a proper view-able angle. To tackle this issue I ignored the best angle for the pyramid and made a bigger pyramid and I morphed the video so the reflection will be good in the pyramid.
Adobe premier pro was used for the bootstrapping works. The following video will show how to create a simple holographic video with the help of Adobe premier pro. In addition to that, I have used the 3D option in the adobe premiere pro to slant the video in the z-axis (12 degrees) so when it is projected in the high slanted pyramid it will look in a normal way without any distortions.
6. How do we make the pyramid?
As I used the perspex glass I initially tried cutting the glass manually, but that ended up in an imperfect finish. Then I resorted to laser cutting. I drew the template shown below in a Corel-Draw file and used the laser to soften the edges and finally bend the glass to form the pyramid. Correct laser specs should be used, otherwise, we’ll end up burning the material.
7. How do we control what is projected in the pyramid?
For simplicity, we used a mobile app to change the projection from the top display. We used a tab as the display option, but for cost benefits, we can use a simple led display which is controlled by the raspberry pie.
8. How do we make the structure that holds the pyramid and the display?
The above image shows the blueprint of the hologram stand. Thick perspex glass was used to provide extra stability to the stand.
Therefore these are the lessons I learned by making the hologram projector for commercial use. If you have any questions please reach me out at sshniro AT gmail.com
This is the final promo video we took for the hologram projector.