# virtual retinal display

> display technology that draws a raster display directly onto the retina of the eye

**Wikidata**: [Q467178](https://www.wikidata.org/wiki/Q467178)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Virtual_retinal_display)  
**Source**: https://4ort.xyz/entity/virtual-retinal-display

## Summary
Virtual retinal display (VRD) is an output device that projects a raster image directly onto the retina of the human eye. This technology bypasses the need for a physical screen by using low-power lasers to draw light patterns onto the light-sensitive cells at the back of the eye.

## Key Facts
-   **Classification:** VRD is a subclass of `output device`, a type of computer hardware that transmits information from the computer to the user.
-   **Core Function:** It functions by drawing a raster display directly onto the retina of the eye.
-   **Aliases:** Known as VRD, retinal projector (RP), retinal scan display (RSD), Retinal Display Virtual, Netzhautprojektor, VNA, Lichtfelddisplay.
-   **Wikidata Description:** Described as "display technology that draws a raster display directly onto the retina of the eye".
-   **Wikipedia:** Has an entry titled "Virtual retinal display" and is available in 10 languages (ca, de, en, es, et, ko, ru, tr, uk, vi).
-   **Schematic:** A diagram is available at: https://commons.wikimedia.org/wiki/Special:FilePath/Virtual_Retinal_Display_Diagram.svg.
-   **Identifiers:** Freebase ID: `/m/06ymj4` (citing Q15241312, 2013-10-28); Quora Topic: Virtual-Retinal-Display (citing Q51711); Microsoft Academic ID (discontinued): 22461511.
-   **Sitelink Count:** 10 (Wikipedia sitelinks).

## FAQs
### Q: How does a virtual retinal display work?
A: A VRD uses lasers or other light sources to scan light beams directly onto the photoreceptor cells of the retina, creating a raster image. The eye perceives this scanned light pattern as a complete image, eliminating the need for a physical screen surface.

### Q: What are the main advantages of VRD technology?
A: Potential advantages include high resolution and brightness, low power consumption (especially for laser-based systems), the ability to create see-through displays (retinal imaging), and compact form factors as it doesn't require a physical screen.

### Q: How is VRD different from a regular computer monitor or VR headset?
A: Unlike traditional monitors or most VR headsets that rely on light emitted from or reflected off a physical screen surface, a VRD projects the image directly onto the retina using scanned light beams. This bypasses the screen, potentially offering different optical characteristics and applications.

### Q: What is the primary application area for VRDs?
A: While conceptual for consumer displays, VRD technology has found significant application in specialized fields like medical displays, aviation (see-through helmet-mounted displays), military targeting, and augmented reality systems where combining real-world and digital views seamlessly is crucial.

## Why It Matters
Virtual retinal display technology represents a fundamental shift in how visual information is presented to the user. By projecting images directly onto the retina, it bypasses the limitations and bulk associated with physical screens and traditional optics in head-mounted displays. This enables potentially lighter, more compact, and higher-resolution displays, particularly crucial for applications like advanced augmented reality, medical imaging overlays, and aviation heads-up displays where combining real-world views with digital data efficiently is paramount. VRD promises to solve problems of screen fatigue, bulk in headsets, and potentially offer higher perceived brightness and resolution in specific use cases, opening new frontiers in human-computer interaction and wearable technology.

## Notable For
-   **Direct Retinal Projection:** The defining characteristic is drawing a raster display *directly onto the retina* using scanned light sources, eliminating the need for a physical screen.
-   **High Brightness Potential:** Capable of producing very high brightness levels suitable for use in bright environments like cockpits, exceeding typical consumer display limits.
-   **See-Through Capability:** Can be designed to allow the user to see the real world *through* the projected image, enabling true augmented reality overlays without blocking vision.
-   **Compact Optics:** By avoiding large screen elements and complex optics required for traditional head-mounted displays, VRDs can potentially lead to significantly lighter and more wearable devices.

## Body
### Technology Description
-   Virtual retinal display (VRD) is a display technology classified as an `output device`.
-   Its core principle is the projection of a raster image directly onto the photoreceptor cells (rods and cones) of the retina.
-   This is achieved by scanning low-power laser light beams across the eye, drawing the image point by point onto the retina.
-   The brain integrates the rapidly scanned points of light into a complete, stable image.
-   It is fundamentally different from emissive or reflective displays that rely on a physical screen surface.

### Key Characteristics
-   **Aliases:** Also known as retinal projector (RP), retinal scan display (RSD), Retinal Display Virtual, Netzhautprojektor, VNA, Lichtfelddisplay.
-   **Projection Method:** Utilizes scanned light beams, typically lasers, to form the image on the retina.
-   **Raster Display:** Generates images by scanning a series of horizontal lines (raster) sequentially.
-   **Retinal Targeting:** Precisely focuses light onto the light-sensitive retina.

### Applications
-   Primarily researched and developed for specialized applications rather than general consumer displays.
-   Significant potential in medical imaging displays for surgeons.
-   Used in aviation for see-through helmet-mounted displays (HMDs).
-   Relevant for military targeting systems and heads-up displays (HUDs).
-   Offers potential for advanced augmented reality (AR) systems requiring see-through capability and high brightness.

### Advantages
-   **High Brightness:** Capable of producing very high luminance levels suitable for bright ambient light.
-   **High Resolution Potential:** Can theoretically achieve very high pixel densities directly on the retina.
-   **Low Power (Laser):** Laser-based systems can operate with relatively low power consumption.
-   **See-Through:** Enables overlaying digital information onto the real world view seamlessly.
-   **Compact Form:** Eliminates the need for bulky screens and complex projection optics in HMDs, potentially leading to lighter devices.

### Limitations
-   **Eye Safety:** Requires careful design to ensure the scanned light energy levels are safe for the retina.
-   **Requires Eye Movement:** Often requires the user to move their eye to scan the entire image field (though wide-field systems exist).
-   **Complexity:** Involves precise scanning mechanisms and optics.
-   **Cost:** Historically associated with high development and production costs for commercial systems.
-   **Vergence-Accommodation Conflict:** Similar to other HMDs, can cause visual discomfort due to the mismatch between where the eyes focus and where the perceived image is.

### Historical Context
-   The concept involves projecting scanned images directly onto the retina.
-   Named after the `retina`, the part of the eye it targets.
-   Emerged as a research area, particularly in the 1990s and 2000s, for next-generation displays.
-   Has been explored as an alternative to conventional display technologies in demanding environments.
-   Identified by specific identifiers like Freebase ID `/m/06ymj4` and the discontinued Microsoft Academic ID `22461511`.

## References

1. Freebase Data Dumps. 2013
2. Quora