Multifocal display
A multifocal display, also called a multiplane display is a type of 3D display that shows portions of images at multiple discrete focal planes at different distances, largely reducing all vergence-accommodation conflicts (VACs).
Low-plane count multifocal display (like two planes) is the natural evolution from 2D displays to light field 3D technology. It is the simplest step up from 2D and it is backwards compatible, promoting market price discovery and independent product development across multiple firms.
Rendering to a multifocal display can be done by taking the depth buffer in software and rendering each pixel on the focal plane that it is closest to depthwise. However this may result in artifacts; see multifocal rendering.
The goal of a multifocal display is to get all the directions of rays of light at the surface of a user’s eyeball.
A multifocal display can be head-mounted, or instead, part of a device that is separate like on a computer screen or laptop computer.
Head-mounted multifocal displays are generally made using a sequential focal stack, where very quickly multiple images are shown and the focus of the optical system changes at the same time. It happens so quickly it all looks like one image.
The image that is projected and the focus of the image do not have to align perfectly. There can be a little bit of a difference, as long as the difference is not too great.
Examples[edit]
- Lightspace Technologies products
- Hoffman, Banks, et. al research prototype
Low-plane multifocal display[edit]
A low-plane multifocal display uses a low number of focal planes, like 2 or 3. It can be two planes, three planes, or generally under 5. It is an early research stage in solving VAC, because having many planes is expensive.
It is typically a head-mounted display.
The focal planes may display simultaneously, or they may be time multiplexed.
One of these displays spans a diopter range. It is limited in the total diopter range due to the margin considering the just-noticeable difference. It is most useful for viewing a 3D scene with shallow depth, like a small scene that is desk-scale. The planes may be placed close together, or far apart.
They are backwards compatible with 2D display techniques.
A system was built by Hoffman, Banks, et. al, which used three planes.
Components[edit]
- 50/50 beam splitter cube
References[edit]
- Banks et. al. Vergence–accommodation conflicts hinder visual performance and cause visual fatigue. https://jov.arvojournals.org/article.aspx?articleid=2122611
- Accommodation to multiple‐focal‐plane displays: Implications for improving stereoscopic displays and for accommodation control. https://jov.arvojournals.org/article.aspx?articleid=2191682