Public computing and two ideas for touchless interfaces

12.40, Monday 11 May 2020

Think about ATMs, or keypads on vending machines, or Amazon lockers, or supermarket self-checkout, or touchscreens on kiosks to buy train tickets. Now there’s a virus that spreads by touch, how do we redesign these shared interfaces?

(This post prompted because I know two people who have separately been grappling with public computing recently. There must be something in the air. These are two ideas I came up with in those conversations.)

Idea #1. QR codes, augmented reality, and the unreal real

The obvious approach is to move the control surface to a smartphone app, just like the Zipcar app lets me unlock my rental or sound the horn. But as an answer, it’s pretty thin… how does a person discover the smartphone app is there to be used? How do you ensure, in a natural fashion, that only the person actively “using” the ticket machine or locker is using the app, and everyone else has to wait their turn? A good approach would deal with these interaction design concerns too.

So, imagine your train ticket machine. Because of the printer, it’s a modal device: although it’s public, only one person can use it at a time.

Let’s get rid of the touchscreen and replace it with a big QR code.

Scan this code with your smartphone camera, and the QR code is magically replaced - in the camera view - with an interactive, 3D, augmented reality model of what the physical interface would be: menu options, a numeric keypad, and so on.

There’s something that tickles me about the physicality of the interface only visible through the smartphone camera viewfinder.

How does it work? An exercise for the reader… the iPhone can launch a website directly from a QR code seen in the camera view. So perhaps that website includes a webcam view which can add the augmented reality interface? Or perhaps it triggers an app download which similarly includes the camera view? (Android has the ability to run mini Instant Apps direct from the store; there are rumours about iOS doing the same.)

The point is to make the transition from the QR code to the AR interface as invisible and immediate as possible. No intermediate steps or confirmations or changes in metaphor: it should feel like your phone is a little window that you’re reaching through to work with the computer, like using a scientific glovebox in a chemistry laboratory, and you’re just moving it into position.

The bonus here is that the interface can only be used while the user is standing directly in front of it, so the “one person at a time” nature of the machine is communicated through natural physicality. I don’t think you get that with apps; an app tethered to a place would feel wrong.

Idea #2. Gestures for no-touch touchscreens

The starting point here is a kiosk with a touchscreen.

Obviously we don’t want the touchscreen to be touched by the general public with their filthy, virus-infested fingers. So, instead, use a tablet with a camera in it, but the screen of the tablet is not intended to be touched. The camera instead recognises hand gestures such as

  • point at screen left/right/up/down (to select)
  • brush left/right (to browse or dismiss)
  • fist (hold for 5 seconds to confirm)
  • count with fingers from 1 to 5 (more sophisticated, for input)

The inspiration is this gorgeous Rock Paper Scissors browser game that uses machine learning and the webcam. That is, the web browser activates your webcam, and you make a fist (rock), flat hand (paper), or scissors gesture, and the A.I. which is also running in the web browser recognises it, and then the computer makes its move. All without hitting the server.

Check out the live graph in the background of that site. It provides a view of the classifier internals - how confident the machine is in recognising your gesture.

What this tells me is that all of this can be done with a web browser and a tablet with a camera in it. For robustness, stick the tablet inside the shop window, looking out through the glass. Set the web browser to show the live feed from the webcam, providing discoverability: people will see the moving image, understand it as a mirror, and experiment with gestures.

It would be like a touchscreen with very large buttons, only you wave at it to interact.

Look, the Minority Report gestural interface is cool but dumb because your arms get knackered in like 30 seconds. But just using your hands or fingers? I could live with a future where we do tiny techno dancing at our devices to interact with them.

Whatever the approaches, the important considerations for public computing interfaces would seem to be:

  • Discoverability (how do you know the interface is there? Public computing has a ton of first-time users)
  • Privacy/security (think of using an ATM on a public street)
  • Familiarity (like, weird is fun, but not too weird…)
  • Accessibility
  • Viability

On accessibility, I’m into Microsoft’s Inclusive Design approach - to see it summarised in a single graphic, scroll to the permanent/temporary/situation diagram here: accommodations might be required for visual impairments, but a person with a cataract has temporary blindness; a distracted driver has situational blindness. For me, understanding situational accessibility (like, having my arms full of shopping or a wriggling toddler so I can’t press a touchscreen) really made me start thinking about accessibility in a much broader way.

Viability is about the commercial and physical reality of public computing interfaces: can it withstand being used 100s of times daily, is it reliable in the rain, is it cheap, etc.


Touchscreens with cameras, web browsers with computer vision, broadly deployed smartphones, augmented reality, voice: these technologies weren’t around when the last generation of public computing interfaces was being invented. It might be worth experimenting to see what else can be done?

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