Part Two : Finding the Right Display
We learned about the planning stages of installing an interactive installation in Part 1 of the series. Now it’s time to get to the meat. Choosing the right touchscreen is a fraught and complex process. There are a plethora of touch technologies, and if the available hardware doesn’t fit your needs, you can always just build your own; the possibilities are endless.
Don’t despair, and don’t get over excited, either. Just keep one thing in mind when selecting your screen: exactly what the interactive needs to do. Once you know how many simultaneous users will be circling around the display, whether they’ll be using gestures or taps, how quickly they expect the screen to respond—in other words, once you’re sure of all types of interaction required—you’re ready to pick a screen.
The Technology Behind the Touch
Not all touch tracking technologies are created equal. Some are great for dragging but can’t recognize continuous stationary touch. Some are good for multi-touch but not for multi-user. (A great example of the diversity between technologies is on the Elo Touch's technologies page.) Getting a screen that is great for taps but no good for expanding images through multi-touch will hinder an experience that wants traditional pinch and zoom gestures.
Getting good at choosing what’s right for each installation comes from a mixture of experience, documentation, and extensive research. After working with a number of touch technologies (with mixed results, at first), we’ve been able to get a feel for what tech works best for each situation, as well as which to steer clear of. Here’s a checklist of what we’ve learned.
- Acoustic Pulse Recognition:
- The Tech: Pioneered by Elo, this technology tracks vibrations created by touches and computes the vibrations origin on the display. This is similar to Dispersive Signal (below).
- Best for: Small budgets.
- Wrong for: Anything beyond very basic one touch applications. Any touch and hold or dragging executions.
- The Tech: Touches are tracked when one conductive layer is depressed and comes in contact with a second conductive layer. This connection results in a change of current, causing the software to pinpoint the location on the display.
- Best for: Tracking any object pressed down on the display. Small budgets.
- Wrong for: Tracking drags or sustained touches (depending on the brand and drivers).
- Surface Acoustic Wave:
- The Tech: Ultrasonic waves flow over the display. When contact is made, part of the wave is absorbed. The software recognizes the disruption of the wave and passes the information to the controller, which processes and tracks the touch.
- Best for: Tracking drags and sustained touches.
- Wrong for: Uses that are prone to dirtying or scratching the screen, which inhibits the responsiveness.
- The Tech: This is the technology behind iPhones and iPads, as well as other hand held devices. The display consists of an insulator (typically glass), coated with a conductive substance. When another conductor, like a finger, comes in contact with the surface, it causes a distortion in the electrostatic field which registers as a touch event. Go with PCT (Projected Capacitance Touch), since it’s more stable and durable. There are two types of PCT: 1) Mutual Capacitance can handle Multi-touch and tracking multiple fingers, hands, or styli simultaneously. 2) Self Capacitance can only track a single point of touch but has a stronger signal than MC.
- Best for: Quick response time. Any sort of tracking.
- Wrong for: Using non-conductive inputs (gloved hands, pens, any other non-conductive device).
- Dispersive Signal:
- The Tech: Brought to us by the fine folks at 3M. Much like the Accoustic Pulse technology, this tracks vibrations on the surface from touches.
- Best for: Detecting touches created by any object.
- Wrong for: Detecting touch and holds if the object is not moving. It responds to drags, but can’t read a user holding their finger down in the same spot.
None of these fit exactly with the experience you’re designing? Build your own. Custom solutions (DIY or commercial) often utilize rear projection with infrared tracking. This means, essentially, that infrared light shines through glass or acrylic while, below the substrate, a camera is set up to track any touches. As a finger touches the surface, the infrared light reflects back to the camera and its position is calculated by the computer. There are several kinds of DIY and commercial setups. Learn more about the different types of optical technologies at NUI Group and Peau Productions. When we create large touch surfaces at Bluecadet, as a final note, Diffused Surface Illumination is our choice of technology. It detects all different types of objects and it is relatively stable and accurate for optical setups.
It's All About the Multi-Touch, Baby
It’s unfortunate that multi-touch still isn't as ubiquitous as it deserves to be. There aren't as many manufacturers supplying multi-touch displays, and the ones out there can be quite costly. Often, the more affordable and prominent multi-touch displays support only two points of touch. Now, how much fun is that? One of the most exciting parts about multi-touch installations is that more than one person can use it at once—an interaction model that opens up thrilling new doors for designers, developers and users. Since multi-touch options are more limited, here are a few display manufacturers worth a look.
- Best for: Gesture support, with a maximum of two simultaneous touches*. Top-notch displays. *We’ve spoken with their engineers and they are in the process of developing support for more simultaneous points of touch.
- Wrong for: Multiple users requiring more than two points of simultaneous touch.
- Best for: Multiple users, multiple touches—their displays support a maximum of 32 touches. They are currently one of the best manufacturers for multi-touch displays with more than two points of touch.
- Wrong for: Very high-quality display. Their screens aren’t quite as sharp as NextWindow’s.
- Best for: Large touch surfaces that support up to 32 points of touch. Great for experiences that require touch support at very large sizes.
- Wrong for: Small budgets. They are on the pricier side.
- Best for: Good display, supporting at least 20 points of touch. We've witnessed them accurately read 60 simultaneous touches.
- Wrong for: Large displays. These screens run on the small side, offering only 22” or 32” displays.
Hopefully our experience can help you on your search for the perfect touchscreen. If you can't or don't get the display with the right qualifications, you can always tailor the experience to best fit the strengths and weaknesses of your hardware. Of course, it can be incredibly frustrating to try to force a particular piece of functionality that just won't work on your hardware. As long as you make sure to fully plan the experience, and only then select the display that will support your vision, the little tailorings become that much easier. Good luck, and stay tuned for part 3 of the series.
Jason Grandelli @jasongrandelli