3rd Dimension (Knoxville, TN) gave a paper and had a small demo in the AVT Simulation booth at I/ITSEC that showcased its second generation display technology. The company called it a “holographic” display, which is partly true as it uses a holographically-defined screen. 3rd Dimension calls its approach “an electronic form of holographic stereography”. But to implement it, the company uses an “angular slice” method to converge light rays, creating a glasses-free 3D image that does not have accommodation and convergence mismatch. The approach is similar to what Holografika does.
Back in 2010, I had a chance to travel to the company’s facility in Tennessee to see the first generation system. It was still a work in progress but you could see that it had potential. That system used 20+ pico projectors and a flat holographic screen to create the 3D image.
The way it works is to line up all the projectors in a horizontal row in the back of the screen. Because of the physical size of the projectors, they cannot be packed close enough so they are staggered in the vertical direction. The projectors illuminate the screen from the rear. The screen has a very special diffuser that confines the light from each projector into a very narrow 1-degree wide line of light with a 60 degree vertical angle.
As shown in the simple graphic below, rays from the four pico projectors converge on a single point in space in front of the screen. If you are careful to create different perspective of the scene for each projector, then the light converging at any point will show the view of that object from slightly different angles. There is horizontal parallax, so if you move your head from side to side, you can see different information at that point. The system does not have vertical parallax, however.
At I/ITSEC 2014, the company modified this concept. First, it created a front illuminated projector-screen configuration (a linear array of projectors were placed at about a 15 degree angle to the center of the screen). Secondly, the company made the holographic screen curved. The curvature creates a more defined viewing headbox so it becomes a single-person monitor. In the demo at the event, 3rd Dimension used 12 SVGA resolution pico projectors and a 30” curved screen to create a headbox that seemed about 8-10″ wide. The resulting image was said to achieve about 2 arc-minutes of angular resolution (20/20 vision is about 1 arc-minute of resolution so this is pretty good acuity).
On display was a demo of aerial refueling with the boom coming from the tanker extending into the viewer space. The total depth seemed about 8-10″ but was really only about 6”. It did create a decent 3D illusion without the eyestrain caused by the mismatch between convergence and accommodation, which is typical of glasses-based 3D (albeit with much greater depth volumes). The image was a bit soft but almost all of the stitching errors ( vertical lines in the display) were gone from this demo. (The photo shows some horizontal lines that were the result of not frame locking all the projectors.)
The team plans to build a bigger demonstrator that it hopes to show at the 2015 I/ITSEC under a new contract. This is slated to be a 60” curved screen that will use 23 projectors with either 720p or 1080p resolution. Right now, the team is considering two offerings of 720p LED projectors from Optoma or Dell with 500 lumens each, so it will be very bright. The graphic shows how the company envisions using it.
The company is also developing a concept for a 13-foot (4m) screen that will use 30 projectors. This will have a big 13’ (4m) headbox, so the projectors will need to be about 20’ (6m) from the screen.
Display Daily Comments
I will be quite pleased to take a look at future displays from the company. (CC)