Mul -plane near-eye stereoscopic 3D display technology...the 2nd rendering pass responsible for the “depth slicing” is virtually negligible in comparison to conven on-al stereoscopic

A problem known as vergence-accommoda�on conflict (VAC), which limits the comfortable viewing �me and might cause adverse effects – most notably eye fa�gue, vision disorders, blurred vision and problems with concentra�ng on a task, hasn’t been solved. This is highly undesirable for professional usage of stereoscopic display technology, as well as for consumer and entertainment segments which require safe and widely accepted 3D technology (with high user sa�sfac�on rates).

Mul�-plane near-eye stereoscopic 3D display technologyAPPLICATION NOTES MPN - 2019/25

lightspace3d.com

LightSpace Technologies, SIAZiedleju 1, Marupe, LV-2167Latvia, EUPhone: (+371) 6780 0009

LightSpace Technologies, Inc. P.O. Box 242, Twinsburg, OH 44087, USAPhone: +1 (234) 200 0570

Copyright 2019 All Rights Reserved

email: [email protected]

lightspace3d.comlightspace3d.comlightspace3d.com

From S3D television to S3D VR headsets

Stereoscopic display systems are known already from 19th century, nevertheless, the idea of tricking the brain into thinking it is observing a three-dimensional image (scene) hasn’t disappeared up �ll current �mes. The display technology has improved – high-resolu�on high refresh-rate micro displays are readily available, allowing to display dynamically changing true color 3D content. The concept behind stereoscopic 3D imaging with single fixed focus plane placed in front of viewer in current mass-produced stereoscopic display solu�ons hasn’t changed.

In human visual system, which is binocular, accommoda�on and eye convergence angle are naturally linked depth cues. When stereoscopic 3D imagery is displayed on a single focal depth-plane, which is the case for most VR/AR display products, eye convergence has the freedom to change, while accommoda�on is fixed on the only available focus plane (otherwise the image would be out of focus).

Consequently, these depth cues become decoupled, contradic�ng and causing the VAC and a�ributed disadvantages. Typical products that realize such an op�cal architecture are the stereoscopic 3D TV’s and their more recent deriva�ve – single focus plane VR/AR headsets (near-eye displays).

lightspace3d.com





lightspace3d.com

2/8

Op�cal principles of mul� plane Stereoscopic 3D (mpS3D) concept

Mul� plane Stereoscopic 3D (mpS3D) display concept from the scien�fic point of view has been previously inves�gated from different aspects, using theore�cal approach and model-systems in a laboratory environment. Experimenta�ons have been performed with a moving (sweeping) displays, variable focus lenses, electrically controllable op�cal path extenders, focal surface genera�on and others.

Nevertheless, for prac�cal implementa�on in a head-mounted display currently available technology hasn’t yielded a sa�sfactory result capable of gaining wide acceptance. Studies by Rolland, Akeley, MacKenzie and others, have shown that an accommoda�on of human visual system can be driven con�nuously or pseu-do-con�nuously with a quite limited number of focal planes without obvious degrada�on in image quality.

Key enabling technology and opera�on principle

In order to implement mul�plane S3D image near eye display architecture LightSpace Technologies have developed superior op�cal quality fast switching op�cal diffusers that are used to assemble mul� plane volumetric 3D image screens. They do switch between low haze fully transparent to high resolu�on image quality diffuser state.

lightspace3d.com





lightspace3d.com

3/8

Translucent state are characterized with very low haze levels that allow to assemble them in mul�plane stacks. For designing mpS3D near eye displays sized for head -mounted VR/AR applica�ons, the company has developed a scaled-down from large volumetric 3D screens produc�on technology of mul� plane diffuser stacks.

Mul� plane diffuser are fabricated as stacks of miniature LCD panels in various form-factors - from 0.5" to 3.5" (diagonal), with 4 to 6 ac�ve switchable diffusing layers. Individual diffusing layer has switching speed between transparent and diffusing state below <1mS.

Complete near eye mpS3D system requires fast image project and synchronized diffuser layer driver. Most op�mal image source for fast image projector today is fast refresh rate MEMS Spa�al Light Modulator (for example suitable resolu�on Texas Instruments DLP). Typically a light engine is built around RGB LEDs but in a case, when VR or AR headset design has foreseen u�liza�on of a holographic image waveduide, or other holographic op�cal elements, the light source has to be reconfigured to u�lize small RGB laser diodes or comound laser modules.

The image stream to mul�plane S3D near eye display can be fed via DisplayPort 1.2-1.4 or DisplayPort over USB-C complex display device. The whole imaging system operates as follows - a mul�plane screen driver sets the Plane 1 in the diffusing state, a�er a small delay the image projecter outputs the first image depth plane comprised of sequen�ally displayed RGB subframes.

lightspace3d.com





lightspace3d.com

4/8

Characteris�cs and comparison of mpS3D near eye head mount displays

Mul�-Plane Switchable Diffuser key enabling technology allows to build real �me superior stereoscopic 3D near eye display which does not create vergence accommoda�on conflict (VAC) and has several advantages over single fixed or variable focus plane S3D near eye displays. Summary table below:

Comparison of technologies Most available VR/AR headsets LightSpace mul�plane stereo 3D HMD display

Employed 3D visualiza�on technology Single plane display stereo 3D

Mul�plane stereo 3D image screen and fast projector

Short name of visualiza�on technology S3D mpS3D

S3D Image op�cal focus range Fixed at single focus plane at a typical distance of ~4m

Mul�ple focus planes over a range 0.3m to 20m (∞)

Binocular vision convergence Yes Yes Monocular accomoda�on No Yes 3D Depth percep�on characteris�cs

Vergence Accomoda�on Conflict Creates conflict - eye fa�gue, sickness Does not create conflict

Observable by single eye 3D depth No Yes Image quality characteris�cs X-; Y- plane resolu�on Up to 2MPix per eye Up to 2MPix per eye Overall image resolu�on over X-; Y; Z- Up to 2MPix per eye Up to 12MPix per eye

Pixel density of image, ppi Up to 600, defined by display Up to 1000, scaleable to achieve op�mum density/FOV rela�onship

Comfortable viewing maximum period 30 min, limited by eye fa�gue *) Not limited by eye fa�gue *) - according to Samsung: "...people can’t stay inside Gear VR comfortably for more than 30 minutes .... the lenses cause too much fatigue to the eyes..."

A�er the last color subframe has been shown, the screen driver swithces Plane 1 to transparent mode and repeats the same pa�ern for the Plane 2. A�er comple�on of the last image plane the sequencing procedure con�nues from the beginning.

With high speed DLP modulators it is possible to achieve 60 to 90Hz refresh rate for image complexity of 4 to 6 image planes. Op�mally, mul� plane S3D system requires two separate image projectors.

lightspace3d.com





lightspace3d.com

5/8

mpS3D based VR headset consist of very few components: • mul� plane image stream spa�al demux (diffuser stack); • eyepiece that op�cally expands mul� plane image screen, requires precise placement to expand virtual image planes at required distances, they need to be adjusted to par�cular user eye requirements; • image projector which is placed above mul� plane screen and folding mirror system to forward projected image into Image Stream Spa�al Demux (diffuser mul� plane device).

Op�cal architecture of mpS3D near eye head mount display for use in VR headset

Birds bath architecture of mpS3D near eye head mount display for use in AR headset

lightspace3d.com





lightspace3d.com

6/8

Birds bath op�cal architecture mpS3D based AR headset consist of very few components: • mul� plane image stream spa�al demux (diffuser stack); • image projector which is placed above mul� plane demux; • birds bath op�cal combiner that op�cally expands mul� plane image stack, requires precise placement to expand virtual image planes at required distances, they need to be adjusted to par�cular user eye requirements; • op�onal addi�onal lens to adjust op�cal distances to user eye requirements; - not shown on the drawing.

Holographic waveguide based architecture of mpS3D near eye head mount display for use in AR headset

Holographic waveguide based mpS3D AR headset consist of more complex assembly but allows for flat image combiner:

• mul� plane image stream spa�al demux (diffuser stack); • op�cal element that op�cally expands mul� plane image stack, requires precise placement to expand virtual image planes at required distances, they need to be adjusted to par�cular user eye requirements; • image projector which is placed above mul� plane screen; • laser RGB led light source; • bholographic surface or volume gra�ng waveguide image combiner for RGB; • op�onal protec�ve glass to block out from reaching RGB gra�ngs of bright outer light.

lightspace3d.com





lightspace3d.com

7/8

Rendering so�ware and performance aspects for mpS3D near eye head mount display

The image rendering for the mul�-plane stereoscopic architecture is a two-pass process, in contrast to conven�onal stereoscopic displays. The first pass is iden�cal to conven�onal methods, while the second pass is used to a�ribute the data rendered in the first pass to their respec�ve image depth plane – in other words the 2nd rendering pass is the “depth slicing”.

In contrast to, mul�-view 3D display technology in which the processing load greatly scales with the number of views to be produced, the mul�-plane architecture only addi�onally requires depth data (depth map) of the scene, which in the case of computer-generated content is readily available. Thus, the processing load in the 2nd rendering pass responsible for the “depth slicing” is virtually negligible in comparison to conven�on-al stereoscopic rendering and makes up a �ny part of the whole rendering process.

A simplified evalua�on using OpenGL in graphs demonstrates the processing performance differences between stereoscopic rendering and mul�-plane stereoscopic rendering for 6 depth planes. As can be seen, the performance differences are miniscule even for very simple 3D scene. Moreover, when addi�onal processing in form of depth an�aliasing is enabled, the rendering performance remains comparable to basic stereoscopic rendering.

30

50

70

90

110

130

150

170

5000 10000 15000 20000 25000 30000 35000

Com

puta

tiona

l Per

form

ance

[Fra

mes

per

Sec

ond]

Complexity of 3D scene [triangle count]

Stereo

mpS3D (6 planes, no depth AA)

mpS3D (6 planes, with depth AA)

155

157

159

161

163

165

0 10 20 30 40 50 60

Com

puta

tiona

l Per

form

ance

[Fra

mes

per

Sec

ond]

Number of depth planes

StereompS3D (no depth AA)mpS3D (with depth AA)

lightspace3d.com





lightspace3d.com

8/8

Follow us: @Lightspace3DLightSpace Technologies LightSpace3D

CONVENTIONAL FRONT VIEWDISPLAY

BENCH TOP DISPLAY “AUGMENTED REALITY SAND BOX”

HEAD MOUNT DISPLAY - CUSTOM AR OR VR SYSTEM

Product summary

X-series models will present fully new model worksta�ons with two versions – 24 and 27-inch screen with 8 to 16 image planes and higher single plane resolu�on - 4MPx. The new model is conveniently deployable into mul� view control worksta�on. Real-Time Volumetric 3D display brings digital content to life and enables people to visualize in a method with no barriers to the 3D experience. The content is viewable in the same way as a real 3D objects, from all angles.

“Augmented Reality Sand Box” or S-series bench top (table-top) volumetric 3D image display worksta-�ons aimed at professionals in fields requiring visualiza�on of scien�fic and medical 3D data sets; security related, tac�cal and traffic informa�on in civil and military environments in rela�on to geographic and terrain datasets, architectural, urban and environmen-tal 3D designs. S-series bench top displays will visualize very high resolu-�on data-rich 3D images with interac-�vity and fusion of real-�me data.

Mul�-plane volumetric 3D image near eye display technology is capable of delivering volumetric 3D images with wide field of view in circular coordi-nates and matched focus depth in whole observable depth space, which eliminates the visual fa�gue of the human eyes that are typically caused by fixed focus depth of stereoscopic 3D displays. Mul�-plane volumetric head mount displays ensure that virtual 3D objects are displayed rendered at the proper focal distances. The viewer perceives 3D scenery and objects naturally as if they were objects in a real environment.

Consumer products – entertainment and gaming Mul�-plane Stereo 3D image VR/AR head mount displays. LightSpace Technologies licenses key enabling (fast switching imaging grade liquid crystal diffuser) technology and relevant IP to Tier1 OEM’s. Agreement may include as NRE project – reference design devel-opment and industrializa�on project for par�cular licensing customer.

Automo�ve products – Mul�ple image plane placed at predefined distances in front of driver – 3D image VR/AR head up displays. LightSpace Technologies supports and licenses key enabling (fast switching imaging grade liquid crystal diffuser) technology and relevant IP to Tier1 automo�ve suppliers and car manufacturers. Agreement may include as NRE project – reference design development and industrializa�on project for par�cular licensing customer.

Professional products

Documents

Mul -plane near-eye stereoscopic 3D display technology...the 2nd rendering pass responsible for the “depth slicing” is virtually negligible in comparison to conven on-al stereoscopic