HMD Head Mounted Display Technology & How It Works

The following article is an in-depth look head mounted displays. It discusses what they are, how they work, and their benefits to users. It also includes details on some HMD models which have already been released to the market as well as some details regarding their potential future applications.

What Are Head Mounted Displays?

Head mounted displays, abbreviated as HMDs, provide users with a visual output via a device worn on the head. HMDs typically take the form of goggles, glasses or visors, and are sometimes mounted on a helmet for ease of use. Applications for head mounted displays range from gaming, to military and medical fields.

How Do Head Mounted Displays Work?

Most head mounted displays have a small screen positioned in front of each of the end user’s eyes. Some, however, only have a tiny monitor for one eye, called a monocular HMD. The majority of HMDs are binocular, with displays for both eyes. The advantage of having binocular HMDs is the user is able to perceive depth when both eyes are able to view their own small screen. Three dimensional perception is achieved with binocular HMDs either with dual video displays, or with multiplexing.

The monitors in HMDs can employ various different display technologies. The earliest HMDs utilized Cathode Ray Tubes (CRTs). They were heavy to wear and bulky to use. More recent models have Liquid Crystal Displays (LCDs), Liquid Crystal on Silicon (LCoS) or Organic Light Emitting Diods (OLEDs). LCDs, LCoS and OLEDs are more compact and allow for a lighter-weight head mounted display. Their energy use is more efficient and therefore less expensive than those which use CRTs.

Many HMDs, particularly those marketed for gamers, are designed to only display computer generated images (CGI). HMDs used for applications in law enforcement, military, and medicine, for example, have the ability to display a real-world view superimposed with CGI. This is sometimes referred to as mixed reality, or augmented reality. HMDs which only show CGI are considered to be displaying virtual reality.

Many HMDs include speakers or headphones, to enhance the users’ sense of immersion by offering both auditory as well as visual experiences. Latency issues with wireless communications demand that the majority of HMDs be hard-wired to ensure top performance.

What Can You Do With A HMD?

Head mounted displays help to give the user a sense of immersion in the environment they are interacting with, whether that’s completely virtual or real with the added visual enhancements. HMDs also allow the advantage of a hands-free method of sharing information.

The most obvious application for HMD use is for simulation and training. By producing virtual environments end-users can feel immersed in, costs and risks associated with training are significantly reduced. With applications such as flying, driving, parachuting, machine maintenance, surgery, etc., experts can easily and inexpensively sharpen their skills or learn new ones with minimal risks to others and themselves.

Gaming and entertainment are also a popular uses for HMDs. However, there is significant overlap between military training and first-person shooter games, for example. HMD users may be entertained and trained at the same time.

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Released HMD Models

Sony’s recently announced HMZ-T1 model contains two 0.7 inch OLED display monitors to produce a 720p 3D picture. The headphones built into this HMD have 5.1 channel surround sound capabilities.

iGlasses offers several different high-end models for computing simulation and gaming. They utilize LCDs, and various models include those for PC and MAC displays. iGlasses includes personal 3D HMDs both at a high-end and consumer price point, each of which also use LCDs in their monitors.

At a much more economical price-point, iTheater’s Head Mounted Display glasses contain two LCDs with a QVGA screen resolution of 320 x 240. The glasses can be plugged into an iPod, and display an image that is the equivalent of watching a 50 inch screen at a distance of 8.5 feet away. The iTheater HR model, by contrast, offers a VGA display of 640 x 480, which is similar to watching a 70 inch screen at that same distance.

Eye-Top Centra’s monocular HMD is essentially a pair of sunglasses with a monitor attached to only on the right eye. The design is sleek and stylish, and the video can be connected via a simple female RCA jack. But it does not aim to totally immerse the viewer in the video. The left eye is free to view the real-world environment.

The Z800 3D visor by eMargin, in contrast, comes with advanced head-tracking to put the user into the 360 degree virtual gaming environment. The displays can be 2D or 3D, and they show a view equivalent to that of a 105 inch big screen.

The Future Of Head Mounted Displays

As with all technologies, the future promises HMDs will become smaller, and less expensive. The marketplace will demand higher resolution, more efficient use of power, faster performance. Though it remains to be seen how much the mainstream will adopt the technology. Governments and corporations will continue to fund research for specific applications of HMDs to benefit their training objectives. However, for the average consumer, the advantages of HMDs may not outweigh the cost.

Although HMDs have been around since the 1990s, they have not been very successful commercially. Corporate and military applications have driven the technology, which may not allow such an easy-fit into the marketplace. For serious gamers, and those training in high-risk fields such as law enforcement, the military, medicine and surgery, head mounted displays are key tools to enhance skills, increase response time and lower costs.