A machine consists of many subsystems working together to perform a certain task. Information from electronic devices is retrieved from machine subsystems as binary code. All of this information is presented in a user-readable format via a display device. Display technology has seen rapid growth in recent decades, from the old CRT (cathode ray tube) monitors to today's LCD (liquid crystal display) and LED (light-emitting diode) monitors. LCDs and LEDs consist of two-dimensional arrays of individual display units (pixels), the number of which relative to the size of the display determines the clarity of the display (resolution). These display units that we encounter every day (LCDs and LEDs) are pixel-based display systems, where these individual pixels form an image by combining individual colors. The colors are formed by different intensities of the primary color combinations RGB (Red, Green and Blue) or CMYK (Cyan, Magenta, Yellow and Black). But these technologies have a bad reputation when it comes to image quality, weight and power consumption when they need to be considered for application in wearable technology.
This is where the emerging concept of Virtual Retinal Display comes into play. It shrinks the gap between the screen and retina to zero, shining light directly onto the retina, just as we see the world around us. It was developed at the University of Washington's Human Interface Technology Laboratory (HIT Lab) by Dr. Thomas A. Furness III. VRD technology can produce images by scanning low-power laser light directly onto the retina, which will create bright, high-contrast, high-resolution images. This is specially designed to offer a more interactive and immersive experience in Virtual Reality and Augmented Reality technologies. It provides a wide field of view with absolutely no background disturbance. In this article we will discuss the aspects and characteristics of VRD and some products recently launched on the market such as the Avegant glyph
1. OVERVIEW
The advent of virtual and augmented reality has required a display device more suitable for visual interaction. A wide field of view, which can be achieved in a pixel-based display by making a curved screen or a curved lens, but this would only increase the cost, which would discourage the commercial launch of this technology. VRD would (to a large extent) reduce the screen size, providing better quality images along with an immersive experience. It would also offer a more personal viewing experience, which would not just be a luxury but a necessity in certain applications, such as surgical practices. So what better way to see images than through the biological way in which the eyes receive direct light from the surrounding environment?
The video source provides the raw image data to the VRD system. The control and drive electronics control the modulators (optical-acoustic) to store the image data and encode it into pulse streams that feed information to the individual photon generators (red, green and blue) to generate a mixed stream to recreate the image in pixel form. The photon (light) sources consist of individual monochromatic lasers, a red laser diode (wavelength 650 nm), blue argon laser (wavelength 488 nm), and green helium-neon laser (wavelength 488 nm). 488nm). Scanning consists of specially designed sets of Mechanical Resonance Scanners (MRS). Delivery optics consist of exit pupil lenses that are aligned with the user's eyes. In some cases, to obtain a transparent image for superimposition in the real world, beam splitters are used to modulate the intensities of the scanned light.
3 WORKING
The combined light is passed through a single-mode optical fiber. This wire carries the light to the VRD's main subsystem, the Mechanical Resonance Scanner (MRS). It consists of a polished mirror on a 2cmx1cmx1cm support. The mirror is oscillated by a magnetic field generated by coils present in the system assembly. It oscillates at a frequency of 15 KHz and an angular range of 12 degrees. The movement of the mirror in the MRS produces a digitized light in the horizontal direction. This scanned light is passed through a mirror galvanometer which is a second set of MRS arranged in a different configuration to allow vertical scanning of the light. The combination of vertical and horizontal light scanning produces a two-dimensional raster that is cast at the focused point on the retina. The digitized image can be sent through a mirror/combiner to superimpose the image on the real world view in case of magnification. reality.
Figure 3 Horizontal (X axis) and vertical (Y axis) scanning of images through MRS
Another important strength is that the digitized light from the VRD is collected directly by the brain in the form of an electrical signal generated by the photoreceptors and tries to make sense of the image. Here, the human brain provides computing power to the VRD and therefore reduces the flickering seen on CRT screens. Each unit of the digitized image is projected onto the retina for a short period of time (about 40 nanoseconds). Furthermore, it produces images bright enough for outdoor viewing along with a wide field of view while consuming power in the Nano watt range.
4 COMPARISON WITH SCREEN DISPLAYS
