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I’ve had The DJI Goggles for a few weeks now and have been looking through them almost every day since I got them. One day, I decided to take a look inside of them to see how they work. I also wanted to know why they are so big compared to something like Fat Shark goggles.
Before taking them apart, I thought I knew exactly how they worked, but after seeing the inside, I realized that I had no idea. Finally, five days after taking them apart I had an epiphany. I discovered how they work and was able to confirm it. Before talking about how the DJI Goggles work, let’s look at some of the cool things I discovered while taking them apart.
This isn’t something you haven’t seen before, but I thought I would show it anyway. These are the connections that go from the main part of the DJI Goggles to the headband. Those gold cylinders are coaxial connectors for the antennas. The antennas use special shielded wires to reduce static and electronic interference. The main connector holds power and USB since the battery is at the back of the headband and the USB port is located on the side.
So far, I haven’t found much to complain about with the design of the DJI Goggles, but there is one thing that I think they need to change and it’s somewhat important. Looking at this hinge, you can see the wires are protected with a braided cable and the hinge mechanism is made of metal which is great, but there’s one problem I’ve had with it. The hinge is held onto the headband with two long screws on each end. These screws are too small to be holding the goggles in my opinion. I did break one of the screws in half and had to replace it with a random screw that I had laying around.
Since the DJI Goggles that I’m using are prototypes, I’m not going to complain about it too much. There’s a chance that the production versions will have higher quality screws. If DJI doesn’t make any changes to the design, just be careful with the hinges!
The first thing I had to do before taking the DJI Goggles apart was to remove the rubber face mask. There are ten plastic tabs and two rubber tabs that hold the mask on the goggles. The mask has a plastic plate on the back of it, so if you ever need to take it off for cleaning, you should pull on the plastic part to avoid damaging the rubber material.
Getting to the inside of the goggles is relatively easy. There are only six screws that need to come out from the back. After the screws are out, the back will come right off. The first thing I noticed after taking the back off was how almost everything is black, probably to stop as much light as possible from bouncing around.
In the top center section, you will see the proximity sensor. This proximity sensor saves battery life by turning the screens off when it detects that you aren’t wearing the goggles. Also located at the top of the goggles are the circuit boards that hold the processors, radios, gyros and a few other things.
I also discovered some things that I didn’t expect to find, like a mini belt drive for moving the eyepieces closer and farther apart from each other. This is for the IPD (inter-pupillary distance) adjustment. After taking the back off, I quickly realized that I wasn’t going to be fully taking these goggles apart. The design was too complicated for me to continue without potentially damaging something.
Since I couldn’t do anything else, I decided to take the eye pieces off to get a better look at what’s on the other side of them. I knew that there were two screens inside and that one of them was mounted horizontally at the top of the goggles, but I had no idea how the image was being projected from the upper part of the goggles to my eyes.
What I found on the other side was fascinating. Each eyepiece covers a unique frame of polarized glass. They also have a felt-like material on them and slide back and forth across the polarized glass to adjust the inter-pupillary distance.
In the picture above, you can see the real screen located at the top of the goggles, and the projection of that screen below it. Notice how the top screen is upside-down so that it shows up correctly when projected.
This next image shows how the top screen is visible through the right eyepiece, but almost entirely black when looking through the left eyepiece.
Taking a look through the right eyepiece, you can also see what looks like a mirror in the bottom section. Before taking the goggles apart, I thought that this was a mirror for projecting the top image onto the front of the goggles, but later I realized that I was wrong. Can you guess what this is?
Here’s one last picture of the goggles from a strait-on perspective. Remember, what you see through the left eye is just a screen mounted vertically, and what you see through the right eye is the projection of the top screen mounted horizontally. The reason why the two screens are in different places is that they are physically too large to be mounted in the same location.
I couldn’t take the DJI Goggles apart without breaking something, so instead, I tried creating a few different lighting models in a light simulator to see if I could duplicate what I was seeing through the lenses. I tried a few different techniques, but nothing was creating the results of what I saw in real life, so I stopped trying to figure it out for a few days.
About a week later, I finally realized what crazy magic DJI was pulling off. The design was more simple than I initially thought but quite ingenious at the same time. Instead of having a mirror on the bottom, the mirror is located directly in the center of the goggles. This isn’t just a standard mirror; It’s translucent. Let’s look at an example to get a better idea of what I mean.
In the Image above, I’ve created a simple 3D illustration which shows how the DJI Goggles work. The blue plane represents the screen for the left eye and the red plane represents the screen for the right eye. The translucent plane that looks like a sheet of glass represents the translucent mirror. As you can see, the mirror is at a 45-degree angle to project the image from the top screen into your eyes. The left screen sits behind the mirror, and the right screen sits above the mirror. Both of the screens overlap each other, but they are offset so that the center of each screen lines up with your eyes. By using polarization, the left eye can see through the mirror but doesn’t see the other screen. The same technique is used so that the right eye doesn’t see the left screen but instead sees the projection.
After I finally understood how the DJI Goggles work, I was able to look at them without taking them apart and see the mirror with my own eyes. You can see the diagonal line where the mirror starts on the side-wall of the goggles, but it’s not something you would ever notice if you didn’t know what to look for. It’s amazing how one of your eyes it technically looking at the roof of the goggles while the other is looking forward, and yet it looks completely normal.
From what I’ve researched, this kind of projection is entirely unique to the DJI Goggles and doesn’t exist anywhere else in the head-mounted-display industry. The only other product I know of that’s similar is Sony’s SLT cameras, where a translucent mirror is used for giving the camera faster continuous auto-focus.
In any case, designs like this are just another example of how much more advanced DJI’s products are compared to the competition. Although, I have to wonder if these advanced mirrors are one of the things that are holding back production of the DJI Goggles right now.
What do you think of the DJI Goggles design? Want to see more articles like this? Leave a comment down below.
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