Introduction

This next entry in my series on companies I met with at CES or Photonics West’s (PW) AR/VR/MR show in 2023 will discuss a company working on a headset for a specific application, namely firefighting and related first responders. In discussing Longan Vision, I will mention ThermalGlass (by 360world using Vuzix Blaze optics), Campfire 3D, iGlass, and Mira, which have some similar design features. In addition to some issues common with all AR devices, Longan Vision has unique issues related to firefighting and other first responder applications.

This was my first meeting with Longan Vision, and it was not for very long. I want to be clear that I have no experience working with firefighters or their needs and opinions on AR equipment. In this short article, I want to point out how they tried to address the user’s needs in an AR headset.

Longan Vision

Below is a picture of Longan Vision’s booth, my notations, and some inset pictures from Longan’s website.

Hands-free operation is a big point and central to the use case for many AR designs. Longan uses AR to enhance vision by letting firefighters see through the smoke and darkness and providing additional life-saving information such as temperature and direction.

The AR optics are one of the simplest and least expensive possible; they use dual merged large curved free-space combiners, often called “bug-eye” combiners based on their appearance. They use a single cell phone-size display device to generate the image (some bug-eyes use two smaller displays). The combiner has a partial mirror coating to reflect the display’s image to the eye. The curvature of the semi-reflective combiner magnifies and moves the focus of the display, while light from the real world will be dimmed by roughly the amount of the display’s light reflected.

The bug-eye combiner has well-known good, bad, and other points (also discussed in a previous article).

• The combiner is inexpensive to produce with reasonably good image quality. This means it can also be replaced inexpensively if it becomes damaged.
• It gives very large eye relief, so there are no issues with wearing glasses. Thus it can be worn interchangeably by almost everyone (one size fits all).
• It is optically efficient compared to Birdbath, Waveguides, and most other AR optics.
• While large, the combiner can be made out of very rugged plastics and is not likely to break and will not shatter. It can even serve as eye and face protection.
• Where the eyes will verge is molded into the optics and will differ from person to person based on their IPD.
• As the name “bug-eye” suggests, they are big and unattractive.
• Because the combiner magnifies a very large (by near-eye standards) display with very large pixels, the angular resolution (pixels per degree) is very low, while the FOV is large.
• Because the combiner is “off-axis” relative to the display, the magnification and focus are variable. This effect can be reduced but not eliminated by making the combiner aspherical. Birdbath optics (described here and shown above-right) have a beamsplitter, which greatly reduces efficiency but makes optics “on-axis” to eliminate these issues.
• Brightness is limited by the display’s brightness multiplied by the fraction of light reflected by the combiner. Typically, flat panels will have between 500 and 1,000 nits. That fraction typically ranges between 50% and 20% depending on the tradeoff of display efficiency versus transparency of the real world. These factors and others typically limit their use of indoor applications.

Longan also had some unique requirements incorporated into their design:

• The combiner had to be made out of high-temperature plastics
• They had to use high-temperature batteries, which added some weight and bulk. Due to their flammability, they could not use the common, more energy-dense lithium batteries.
• The combiner supports flipping up to get out of the user’s vision. This is a feature supported by some other bug-eye designs.
• The combiner also acts as an eye and partial face shield. Their website demonstration video shows firefighters having an additional flip-up outer protective shield. It is not clear if these will interfere with each other when flipping up and down.
• The combiner must accommodate the firefighting breathing apparatus.
• An IR camera feeds the display to see what would otherwise be invisible.

Companies with related technologies

I want to mention a few companies that have related technologies.

At CES 2023, I met with ThermalGlass (by 360world), which combined infrared heat images with Vuzix blade technology to produce thermal vision AR glasses. I discussed ThermalGlass in my CES recap with SadlyItsBradley.

Mira has often been discussed on this blog as an example of a low-cost AR headset. Mira’s simple technology is most famously used in Universal Studios Japan, and Hollywood Mario Kart rides. Mira’s website shows a more industrially oriented product with a hard hat and an open frame/band version. Both, like Longan, support a flip-up combiner. The open headband version does not appear to have enough support, with just a headband and forehead pad. Usually, an over-the-head band is also desirable for comfort and a secure fit with this type of support.

In my video with SadlyItsBradley after AWE 2022, I discussed other large combiner companies, including Campfire, Mira, and iGlass.

The images below show some pictures I took at AWE 2018 of the iView prototype with a large off-axis combiner with a front view (upper left), a view directly of the displays (lower left), and a view through the combiner without any digital correction (below right). The football field in the picture below right illustrates how the image is distorted and how the focus varies from the top to the bottom of the display (the camera was focused at about the middle of the image). Typically the distortion can be corrected in software with some loss in resolution due to the resampling. The focusing issue, however, cannot be corrected digitally and relies on the eye to adjust focus depending on where the eye is centered.

Conclusions

Longan has thought through many features from the firefighter’s user perspective. In terms of optics, it is not the highest-tech solution, but it may not need to be for the intended application. The alternative approach might be to use a waveguide much closer to the eye but with enough eye relief to support glasses. But then the waveguide would have to be extremely ruggedized with its own set of issues in a firefighter’s extreme environment.

Unlike many AR headsets that have me scratching my head. With Longan Vision, I can see the type of customer that might want this product.