A new holographic lens aims to fix several AR display issues

Image: Creal

Swiss startup Creal is developing an AR lens that should offer big advantages over existing optical AR systems. A new video illustrates its function.

The lens is one of the essential components of transparent AR headsets. Called “combiners” in technical jargon, they combine natural and digital light for believable augmented reality.

Ideally, AR lenses should meet a range of requirements:

• They must be transparent in both directions,
• not produce artifacts (e.g. rainbow effect),
• enable high-quality, bright and energy-efficient 3D graphics,
• support vision correction,
• fit in a slim AR headset,
• and be inexpensive to produce.

The most commonly used combiners are waveguides, which are used in Hololens 1 and 2 and Magic Leap 1 and 2, among others.

Creal develops a holographic AR lens

The Swiss start-up Creal (pronounced “see-real”) relies on another type of combiner, the HOE (“Holographic Optical Elements“).

“A HOE is essentially a thin film – comparable to a human hair – that lets almost all visible light pass without effects while reflecting one or more selected colors in the desired way. HOE forAR glasses are therefore completely transparent to almost all the light from the real world but reflect almost all the light projected by a screen (which should only use the few selected colors that interact with the HOE, of course).The physical concept of HOEs is quite simple, they are extremely energy efficient and inexpensive and can be directly integrated into a conventional prescription lens.

Creal writes in a September white paper.

Development of the HOE began in January 2021 in the company’s holography lab. From summer, the first working lens prototype emerged, providing high-quality 3D images and supporting Creal’s brightfield technology, which can simulate different depth planes for AR elements.

Creal AR lens: first HMD prototype coming in 2023

HOE combiners are not an innovation. Sony, Intel and North have already developed and used them for AR devices. A subgenre of the holographic lens could also play an important role for VR headsets in the future (see Meta’s Mirror Lake prototype).

What makes Creal’s new HOE combiner special is that it supports the company’s proprietary light field technology and solves the biggest drawback of previous HOEs: the tiny eye box, or the area where holograms are projected into the eye.

In the white paper, Creal compares the pros and cons of various optical AR systems. Creal’s brightfield HOE is shown in the center, with the waveguides to the right. | Image: Creal

Although the holographic AR lens is new, Creal has been working on its own light field technology for many years and has already demonstrated several VR and AR prototypes.

Creal’s light field representation mimics the behavior of natural light. The focal planes are therefore already included in the image information and do not have to be simulated separately (see this explainer). This allows the eye to focus naturally, which resolves the conflict between vergence and accommodation.

The September 2022 video above demonstrates how the technology works using the latest AR prototype as an example. Note the focal change between foreground and background depending on what the camera is focusing on: once the hologram and the hands, once the background.

Creal’s new HOE lens is not yet seen in action here: according to Creal, it will be integrated into a new hhelmet prototype with light field display early 2023.

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