09-06-2017, 09:33 PM
VIRTUAL RETINAL DISPLAY
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INTRODUCTION
The virtual retinal display (VRD) is a display technology which scans modulated laser light on the retina of viewer's eye to create an image. The viewer has perception of standing just in front of high resolution screen or projector but in reality image is on the retina of his eye and not on the screen. The VRD is a device that scans an image, one pixel at a time just like ordinary CRT. The VRD takes video signals from a graphics card or video camera as a input, than these signals are used to modulate light according to the intensity of pixel from light source which can be laser diode, gas lasers or Light emitting diodes. The light is than multiplexed to an optical fiber which transports this light to the scanning assembly, the scanner scans the input light on viewer's retina using horizontal and vertical scanning subsystem in a periodic manner. The output is an image with excellent quality in means of high resolution with no flickering.
WHY VRD S
The CRTs has been the primary active display device for the presentation of entertainment and information. There is much work to supplant the CRT with the lighter and smaller flat panel display which consist of liquid crystal (LCDs), plasma and other technologies. All of these have the common principal that an image that is generated electronically is viewed with the optical system of the eye. The image you see is subject not only to the quality of the optical system of the eye, but also to the quality of the display and the environment in which the display is located.
What if you could bypass defects in the eye's optical system, such as damaged cornea and lens and reduced retinal sensitivity? What if you could remove the problems of the display environment, such as ambient brightness, angle-of-view and display brightness? What if you could naturally augment the image you see naturally with other information?
2.1 Retina
A multi-layered sheet of nerve cells at the back of each eye which converts light signals to electrical signals by performing a chemical reaction. The electric signals are transmitted to brain through the optic nerves.
2.2 Photoreceptor
Photoreceptors are the nerve cells in the retina which emit electrical signals when activated by light of particular wavelength. There are two types of photoreceptors cells. Rods, which are responsible for low light perception and Cones which are used to perceive colour and bright light.
2.3 Macula
The macula is located roughly in the centre of the retina. It is a small and highly sensitive part of the retina responsible for detailed central vision. The fovea is the very centre of the macula. The macula allows us to appreciate detail and perform tasks that require central vision such reading.