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09 Aug 2002
Originally published in Displays Europe magazine earlier this year, Chris Williams' polemic sparked some fierce debate. In the upcoming issue of the magazine due to be published in September, Tom Holzel, CEO of Printable Field Emitters, a start-up company in the field-emission-display sector, takes a somewhat different point of view.
Look out for this in the next issue of the magazine and subscribe free on-line at Displays Europe subscriptions.
Chris Williams of UK-based display consultancy Logystyx says that headset displays have little attraction for consumers, and could pose health and safety risks.
Headsets fall into two categories: augmented reality (AR) and virtual reality (VR). AR headsets, where "real-world" vision is supplemented with a forward-projected transparent image through which the user sees, can supply valuable information to help perform a task. Back in the days when my amplifiers oscillated and my oscillators wouldn't, I might have appreciated AR glasses showing oscilloscope waveforms. I never got the hang of juggling printed circuit board and scope probes while cricking my neck to see the trace, so I gave up electronic design.
So what does AR look like? Try looking at your TV with both the main picture and teletext activated. Watch the picture and simultaneously read the text. It's easy for a while or if you keep taking breaks, but difficult for continuous use. Maybe professional users will adopt such "wearable computers", but for the mass consumer market - forget it!
But no, the product-marketing dreamers in search of the "killer application" want to bring AR into everyday life. The idea of AR headsets being a viable wearable computer option for mobile phone users fills me with dread. Drivers already crash cars when distracted by mobile phones. What chance do we have if there are video images to look at as well?
As if that weren't bad enough, VR headsets completely replace the real world with an electronic image displayed in front of the viewer. Job-specific VR headsets have existed for years - night-vision goggles and infrared thermal-imaging goggles are just two examples. They extend the human vision system's dynamic range and allow the user to "see" the frequency-translated images where normal vision would be inadequate. But they are usually linked to a helmet-mounted camera and worn while the user carries out the task, so the artificial images are supported by other sensory inputs.
Health and safety
Commercial "edutainment" VR headsets are designed to present fully immersive full-motion video for games and feature films to "involve" the viewer. First, can you really see modern youth (the target market for electronic consumer goods) wanting to look like extras from "Planet of the Ants"? Second, there are many human factors that may well have personal health and safety implications, but these seem to be ignored by commercial product developers.
Take two very simple parameters - weight and image quality. Designers aim to get headset weight down to 100 g. I wear spectacles to improve the resolution and image quality of the world I look at. Ordinary spectacles with glass lenses and metal frames typically weigh only 40 g. Why would I buy - and use - a heavier-than-spectacles microdisplay headset offering resolution and image quality much lower than real life that I will find uncomfortable after a while? (Eye resolution is 130 million pixels, while VR display resolution is about 1 million pixels.)
Apart from weight, there are some fundamental problems that remain, even if the image of helmeted storm troopers does become de rigueur. The showstopper comes where you are a passive viewer using a VR headset. Images on the display totally replace your view of the real world, but move your head and the displayed world moves with you - not what happens in the real world. This is where the problems start.
Ever been seasick? The biggest problem with VR glasses is that they must fool the brain which is used to interpreting sight and movement. The imagery projected by the glasses into the visual system shows apparent movement to the brain. The ears, as well as having primary responsibility for hearing, also sense movement, but in this case they detect none. The brain, worn out with arbitrating between conflicting sensory systems, goes on sick leave in the literal sense.
This problem is not one of display resolution. Cramming multimillion pixel displays into a VR headset won't overcome the brain's expectation of synchronized inputs from eyes and ears. People fall over in (fully immersive) IMAX cinemas and find it funny - they won't when they have to clean the carpet at home.
Most people I know have never tried VR headsets or experienced the physiological impact. Want to try at home? Sit close to your TV and stare at an in-car camera sequence or rollercoaster ride. If you feel any sense of nausea then you probably won't like VR headsets!
So, in a final plea to headset companies, please develop professional headset systems, but leave the consumer market out of the loop. The streets are littered with early failures of companies who tried to address this mythical "killer application". Yours won't be any different.
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