Update: H+ Technology issued a statement about the limitations of Holus. Read about it in Part 2 of the “holoscam” story.

tl;dr: The Holus “holographic display” appears to be nothing more than a flat computer monitor reflected in a piece of glass, like the old optical illusion known as Pepper’s Ghost (read “not 3D”). The language and CGI used in the Holus campaign might not reflect the limitations of the product and could potentially mislead the backers into thinking they are getting a volumetric display.

Holographic table from Prometheus (2012)

When we talk about a 3D holographic display, we think of a device capable of showing volumetric images in mid-air; a 3D representation we can walk around and look at from every angle.

Recently, there’s been a trove of controversial crowd-funding projects promising such breakthrough technology.

The most recent attempt at crowdfunding a “3D holographic display” is the Holus by H+ Technology. At the time of this writing it raised more than 200.000$. That is four times their initial goal.

Throwing money at holographic technology. An allegory.

The Kickstarter campaign boasts:

“Holus provides a blend between the digital and real world by converting any 2D digital content into a 3D holographic experience”

That is a pretty big claim. You would expect H+ Tech to offer a very convincing demonstration to back it up. At least some kind of scientific explanation of the way they generate a 3D image from 2D content, right? Yet, aside from a couple of pretty animation that don’t tell you much, the Kickstarter page remains surprisingly fuzzy about the details.

In 2013, the Holovision by Provision 3D also surfed on the holographic wave but their Kickstarter got suspended for copyright infringement. This is what the CTO of H+ Tech had to say about Provision3D back then:

“Provision 3D has put up a Kickstarter project and they are planning to make a life sized hologram if I believe correctly and they mentioned that this is without any magic trick or glasses or any of that sort and when I was looking through the comments online, people found that one of their patents actually uses glass at a specific angle to capture the right reflection. Their patent goes against what they are saying on the Kickstarter project. Perhaps they have new technology developed after filing that patent or after getting that patent. In that case, they should have made it clear that, yes, they do have so- and so- technology which is not what they call online Pepper’s Ghost effect, or a reflection based holographic effect.” — Source: this article on H+ Technology’s own website [emphasis mine]

The Pepper’s Ghost Illusion

Remember the Tupac “hologram” back in 2012? It was done using a 19th century stage illusion known as a Pepper’s Ghost; a classic optical trick used to make ghostly shapes appear on stage.

A representation of the original Pepper’s Ghost illusion.

“Pepper’s ghost is an illusion technique used in theatre, haunted houses, dark rides, and magic tricks. It is named after John Henry Pepper, a scientist who popularized the effect in a famed demonstration in 1862.” — source: Wikipedia

The effect works by using a piece of glass or perspex on which the actual object is reflected. If the reflected object is a screen, you can display anything, but the image will appear like a 2D plane floating in the air.

You can see a demonstration of a screen-based Pepper’s Ghost effect in this video by digital artists AdrienM / ClaireB (here using a LEAP motion sensor for input):

How does Holus (probably) work?

According to the Kickstarter page, the Holus display works by reflecting a screen located in the top of the machine onto four pieces of glass. This sounds very similar to the so-called “pyramid holograms”. Four Pepper’s Ghosts in one if you will, like in this demo by Aircord from 2010:

The N-3D by Aircord (2010)

This trick has been around for a long time, and you can build your own with a piece of transparent plastic and your smartphone or tablet.

Smartphone Pepper’s Ghost prototype by Yuri Endo.

It can actually look pretty nice in the right conditions, but it is not a volumetric display, let alone a hologram. It is just a 2D image seemingly floating in mid-air. Similar to looking at the reflection of your phone or tablet in the window of a train at night. To get four viewing angles, you just have to display one different image for each side of the pyramid.

Another DIY “pyramid hologram”. Source: this video

H+ says they wanted to make something “with as many viewing angles as possible”. With a pyramid, that means four. There is only one image on the Kickstarter page where the top of the box is actually visible from the inside.

Can you make out the four images providing the four viewing angles?

If Holus is indeed a Pyramidal Pepper’s Ghost, the reflection can only be seen when sitting in front of one of the four screen and there is no 3D, unless you consider displaying an object four times from four different angles to be 3D. This seems consistent with this image of the Holus prototype from the Kickstarter video.

Notice how the right of the image gets cut off by the edge of the pyramid.

Such displays look much better in a video because you can’t easily notice the absence of depth in the “holographic” image... until you move around the pyramid:

The illusion breaks when you move from one viewpoint to the next. Source: this video

Smoke and mirrors

If the Holus is a Pepper’s Ghost pyramid, calling it a “3D holographic experience” is already problematic, but the real issue here is that H+ Technology is using CGI renderings that don’t reflect the limitations of such a device and make it look much better than a Pepper’s Ghost display can ever hope to be.

In a Pepper’s Ghost display, the part of the image in the green triangle could not be seen from this angle.

With such a setup, you can’t look around to change your perspective. There is no depth, no parallax. In other terms, you can’t move your head to peek behind objects. You also can’t display colors darker than the background. It will not look like a real world 3D object. Merely reflecting a 2D image in a piece of glass doesn’t magically make it 3D.

Pepper’s Ghosts can’t do that, sorry.

If backers understood this, would they still be willing to shell out between 550$ and 8000$ to get their hands on what is most likely a repackaging of a well worn 19th century technology?

Of course, there is always a slim chance that H+ actually made a breakthrough in holographic technology, that the CGI is a faithful representation of their product and that Holus just happens to look exactly like a 150 years old parlor trick… I’ll let them answer that one:

“In that case, they should have made it clear that, yes, they do have so- and so- technology which is not what they call online Pepper’s Ghost effect, or a reflection based holographic effect.” — Dhruv Adhia (CTO, H+Technology)

What Can I do?

You may report this project to Kickstarter for “false claims” using the link a the bottom of the project page. Here’s a possible report message:

H+ Technology’s presents a “Holographic Display” supposed to offer a “3D holographic experience”. The Holus video is using CGI to make it appear like the Holus can display volumetric content providing depth cues and parallax (in particular at the 0:50 and 0:58 mark). This is in clear violation of the rules of the Kickstarter platform concerning photorealistic renderings. These renderings don’t reflect the actual limitations of the product as made clear by this other video from the project creators: https://vimeo.com/130601555 More information can be found in the following articles:

Part 1: https://medium.com/p/c12a861cb8bf

Part 2: https://medium.com/p/6bd4a70d7d9e

If you are a backer please ask this question to the project creators in the comments:

The city at 0:50 and the ring at 0:58 look really impressive! Can you comment on the allegations that they are photorealistic renderings and not images of the actual Holus prototype? Source: https://medium.com/p/c12a861cb8bf & https://medium.com/p/6bd4a70d7d9e

Then, if you do not feel like backing anymore, visit the project page and click the blue “Manage” button that appears next to your pledge amount. At the bottom of the next page you’ll see the “Cancel Pledge” button.

If you want, you can share this article, discuss it on the Reddit, HackerNews, Twitter, crowdfunding forums or even Google Plus… Alert people in the comments on tech blogs or contact the journalists directly.

Read Part 2: Holus: H+ Technology back-pedals in the wake of “holoscam“ backlash.

Note: I haven’t seen a Holus prototype with my own eyes. The opinions presented in this article are based on my research, careful study of the Holus videos and my professional experience with pseudo-holographic displays. It should be considered an educated guess and may not reflect the final Holus product.

June 12th: H+ Technology did not immediately answer my request for comments. I’ll update the article if they do.

June 13th: I contacted the creators of Holus through the Periscope broadcast they held today. They confirmed that the display is not volumetric because no safe technology allows it to this day (but we knew that already). They said that the video is “aspirational” and not a representation of the actual product (This is, by the way, against Kickstarter rules concerning photorealistic renderings) which is indeed based on the Pepper’s Ghost principle. H+ Technology announced that they are preparing a response to this article.

PS: this is what state of the art mid-air volumetric displays look like today. It uses high power lasers to ionize the air. Yes, it’s extremely dangerous. You definitely don’t want that on your tabletop. Other techniques use screens or arrays of LEDs rotating at very high speeds. Not exactly kid friendly.