ontheweg
God offers us a paar of amazing eyes, with which we are able to perceive the world more strongly and intuitively. With the development of the technique, the available things for us to watch, view or see are more and more abundant. Specially the improment of television lead to a new visual feast. While human's requirement can never be satisfied, we dream of a new view perspective way of the world, we want to change our world visually in our own way, at any time, in any place, with any angle. For example on the way to university we could play a computer game as first character with read scenario:
With the help of HMD (Head Mounte Display) we are able to realize it easily. Frankly speaking it is a head worn display, that is putting on the display device on the user's head with the display in front of the eye or eyes. It is able to offer the user not only just head motion, but potentionlly whole body mobility. Usually HMD has one or two semi-transparent displays fixed on the view glasses or something like pilot's helmet. And it is considered as one of the bridges between the eyes and a virtual environment. Here is a nice video from CNN about HMD:
From user's perspective side to say the HMD will be divided as monocular (with one eye display), biocular (with the same image applied on both eyes) and binocular (stereosopics images). The first creation of HMD or quasi-HMD was done by Ivan Sutherland by 1960s. It was used for USA Army flight Helmet sighting system. And later was further developed and applied in Education, Medical application, Sport and entainterment areas.
The image above illustrates an example of HMD, which is embedded on a helmet device with two camears. With these cameras the user can see the read environment around, besides with the analysis based on the environment images or video, the helmet device is also able to estemate the position of the head or even whole body. According to the ways how the computer generated images are immersed into the view, the HMD could also be distinguished as Virtual Reality HMD which just offers the virtual computer generated image on the display, without any information of outside real environment; and the other one is the Augmented Reality HMD which combines the real view outside and virtual images (as shown in figure 1), with the help of a see-through displays or cameras fixed on the helmet. But attention, with the camera embedded HMD is not necessary Augmented applied. Because they can be used as a pose estimation function.
One of the largest chanllage is to design a high solution view effect device but with reasonalbe size and light weight requirement. So the microdisplay sources play a significant role for this problem solution. In early HMDs, miniature monochrome CRTs were primarily employed. Then VGA with 640 x 480 color pixels AM-LCDs took place. While today more and more excellent microdisplay techniques garantee the better display solution with expected size as SVGA with 800 x 600 color pixels, XGA with 1280 x 1024 color pixels resolution LCDs. FLCOS, OLEDs and TMOS are also on the way of the implementation for HMDs. Here is a table about the descriptions of different display techniques:
To describe or evalute the HMD more detailedly or more technically we need to focus more on some of the performance parameters which are relevante for the HMDs' view effect, stability and life span, such as: resolution, FOV(Field of View), Binocular overlap, distant focus and so on. There is a paper which is specially about the Head Mounted Display. Inside you could find more professional description and definitions about this technique. When you have interest, CLICK me:)
At the end is another interesting video about DIY of a HMD system for a flight simulator. It appeares the private HMD is already not far from us, right?
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