Head-mounted displays (HMD) are, as the name implies, visual devices that are mounted to the head of the user. Through the proximity of the video output to the eyes, the slightly shifted pictures of one eye to the other and the head-tracking, the HMD convey the impression that you are standing in the virtually created world, instead of just looking at it through a monitor. The area of application for such devices is as vast as the price range and starting from the virtual reality headsets for games, to augmented reality HMDs and to whole helmets, which e.g. are used by pilots for educational purposes.
Despite the fact that virtual reality and head-mounted displays where simply seen as little gimmicks by the public for a long time, they were already in use in areas like the military or medicine. But since the day when tech-giants as Microsoft, Google and many others more started to introduce their head-mounted displays to the market, the interest und investments increased drastically.
Military & more
In most cases the military is the first initiator for investments in new technologies and the first one to use them for training purposes. For example: the pilots in the military use helmet HMD combined with flight simulators to get to know the aircraft and its flight characteristics better without the risk and expenses of the traditional way. Another possibility is to use the augmented reality glasses to provide important soldiers with visual information, which are silent and can only be seen by the person wearing the glasses.
Science & medicine
With the help of the robotic and HMD medicine and all other areas of science could experience a huge change. Doctors would be able to make operations without being in the same room, or even country, as the patients. The same goes for almost every other scientific projects and undertakings. But the most important point should be the researches and conduct studies related to vision, balance, cognition and neuroscience, which are heavily simplified by head-mounted displays.
With the introduction of the Oculus Rift the virtual reality market started to boom. Who does not want to experience his favourite game as if he was part of it. Imagine that you turn around, a blood-soaked sword in your hand and a huge army is facing you and waiting for your orders. Sounds exciting, am I right? This and other reasons drive the gaming industries and all the other involved parties to create a way to enter the virtual realities. Not only the gaming industry, but even the educational and scientific institutions will benefit from the development of virtual reality headsets.
The price range of a head-mounted display can start from 35$ and can go up to 1000$ and sometimes even more. But the price is not the only thing that can vary that much. The dimensions, the technical specifications and the features of a HMD can differ, depending on the purpose, which the device is made for. Obviously they do, since they are used for different tasks and under different circumstances. Some of them are used stationary; others are carried around by the user. Virtual reality headsets shut down the whole world around you, to lead you to whole new (virtual) worlds, while augmented reality headsets still let you see your environment and add new visual information to them.
Technically the displays and headsets can provide different specifications according to the tasks they have to fulfil. Almost any part can vary, starting from the uptime of the displays, to the size and weight and even to the display properties. Some have head-tracking equipped, others have not. While some produce a 150inch virtual HD display others have more simple displays. In the end the price reflect the features and capabilities of such a device.
As mentioned above, the gaming headsets are used to provide audio-visual output, that gives you the impression of being part of the game. Usually they come with respective controllers and connecting cables. Moreover there are different HMDs, which are adapted to different devices, like gaming consoles, PCs or even smartphones. Some of headsets support all of the mentioned devices and the majority can also be used for 3D movies or any movies.
Head-mounted TV displays
The head-mounted TV displays can be used for everything that the gaming headsets are used for. The major difference is the fact, that they are just TV screens attached to the user. They do not provide special controllers for your games or the head-tracking. Surely some of them are mixed up and it is not always possible to categorize a headset to one of these two categories.
Augmented reality HMD
In contrast to the previous two head-mounted display types, the augmented reality devices pursue a whole different purpose. They are not simply a screen mounted to the head, but rather a pair of glasses mixed with a monitor. As the name implies, they augment the reality, meaning they add information to the current reality. The way of implementation of this process varies. You have either additional information on the corner of your glasses that follows you around or you attach information to a specific object in the real world and every time when you look at it, the information are going to be displayed, thus augmenting your reality.
Head-mounted displays in the near future
The next step for the head-mounted displays is going to be the exploration of the human brain and neuroscience. Imagine if you want to run a mile in the virtual world that you are in right now. To accomplish that you have to walk a mile in the real world too, which is pretty impractical if you want to play a game in your living room. If the neuroscientists manage to understand the complexity of the human brain and how to use the signals of the brain to control the virtual reality headset, a new era would be ushered. But in the end the device you choose will depend on yourself and the reason you are buying it for.