Virtual retinal display
The term virtual retinal display ( VNA, english virtual retinal display, retinal scan display or retinal image display) is a display technology that draws a raster image directly onto the retina of the eye. The user gets it the impression of a floating canvas in front of him.
Operation
In the past, similar systems were manufactured, which represented an unfocused image on a small screen in front of the eye of the user, usually in the form of a kind of oversized sunglasses (see VR helmet). The user focused his eyes on the background, the screen looked as if he was floating. The disadvantage of these systems was the limited area of the screen, the heavy weight of the small screens that were used for imaging and the fact that the image is sharp only when the user had focused his eyes on a certain depth. Due to the limited brightness of these systems, they were also useful only for indoor use.
Only recently did some real innovations VNA systems usable. In particular, the development of high-brightness light-emitting diodes made the presentation now bright enough to use the device even during the day outdoors can. In addition, Adaptive optics allowed the devices to dynamically adapt to irregularities of the eye ( but this is not necessary in every case). The result is a high-resolution display with excellent color gamut and brightness, far better than the best screens.
Most research in the field of VNA has been carried out in combination with various systems of virtual reality. In this role VNAs have the advantage of being significantly smaller than existing screen based systems. However, they share some of the same disadvantages as the need for optics to bring the image on the retina. VNAs may be used as part of a portable computer system.
Recently there has been some interest in VNA for use in mobile devices such as mobile phones, PDAs, and different players. In this role, the system would be established before the user is directed to a table and upon his eyes, for example. The system would then recognize the eyes using face detection and project the image using motion compensation to the right place. In this task, the VNA offers unique advantages, as it allows to simulate a full-fledged monitor in a small device.