While Stimulant’s repertoire of sensing and input devices is broad, we frequently come back to touch as a primary method of interaction with our installation projects. Touch offers direct interaction with content in a way that visitors are familiar with due to the ubiquity of mobile devices, but touch can still be exciting and novel when used with large or otherwise unique form factors, or when combined with other sensors or input methods.
As easy as touch screens are for visitors to use, we’ve learned that not all touch interfaces are created alike. In this article we’ll compare some of the products in our lab and hopefully provide some guidance for choosing the right product for your next touch project.
There are many technical approaches to implementing touch, each with differing benefits and limitations around size, environmental interference, performance, and cost. Here are a few of the most common.
A projected capacitance (or “pro-cap”) display has a grid of conductive material under the top layer of glass. When powered on, the grid creates an electrostatic field which is interrupted when touched. These interruptions are interpreted by firmware on the display and passed to the operating system as touches.
Pro-cap displays tend to have very low latency and high accuracy compared to other display types, and are not affected by environmental conditions like sunlight. The downside is that they are difficult and costly to manufacture at large sizes. As such they tend to be most suitable for single-user kiosk experiences, such as our Reunion Tower, ASCO, and Space Needle projects.
Infrared (IR) touch products tend to come as rectangular bezels which are used in conjunction with a separate display device at installation. The bezels project a grid of infrared light beams between them, and touches are detected when the beams are interrupted by a finger or other object.
IR overlays can be produced at very large, arbitrary sizes, so they are suitable for multi-user “touch wall” experiences such as our Maxim and MOHAI installations. Their accuracy and latency tend to not be as good as pro-cap displays, however. Environmental infrared light (such as sunlight) can also interfere with the displays to such a degree that infrared-filtering films should sometimes be placed on surrounding windows.
Vision-based displays use infrared light combined with cameras and computer vision algorithms to sense touch. IR light is projected onto the display surface via IR LEDs along the edges where fingers, hands and other objects on the surface reflect the light back inside the display. These reflections are detected by a camera inside the unit as “blobs”, which are then processed using “blob detection” algorithms and interpreted as touches. What’s more, sometimes they can return finger orientation based on the shape of the “contact patch” of the finger, allowing the system to know generally where the user is standing or sitting relative to the touch surface.
The vision-based approach enables very large displays that can detect a virtually unlimited number of touches. Aside from touches, other objects can be tracked if they’re marked with a fiducial — a graphic pattern which is interpreted as a numeric value. The technology is simple and accessible enough that you can make your own vision-based touch table.
Vision-based products tend to have higher latency and are physically deeper than other display products in order to house the projection and camera assemblies. The ability to sense many touches and other objects make them suitable for multi-user and tabletop applications, such as our WIND, Bing, and TouchTones projects.
It would be impossible to include every touch product on the market today, but we’ll discuss a few which we’ve actually used at Stimulant and can recommend for production projects.
The 3M pro-cap multitouch displays are extremely durable and responsive, and range in size from 21” to 46” diagonal. The first of the 46” displays to roll off the production line were destined for the Reunion Tower observation deck where they are used by visitors every day. After our positive experience with the displays in Dallas, we used them again on the Space Needle observation deck in Seattle. They support up to 60 simultaneous touches and are spill-resistant and “toddler-proof”. The displays are available directly from 3M, or integrated with a PC in a table or wall form factor from Ideum.
The Perceptive Pixel (“PPI”) product was introduced in 2007 and was considered a high-end product for government and broadcast use. They are often seen on news programs displaying infographics which can be manipulated and annotated to explain complex concepts to viewers. Microsoft acquired the company in 2012 and rolled it into their Office division, positioning it as the perfect thing for every conference room and collaboration space.
PPI displays use projected capacitance, are available in a 55” and 82” form factors, and are intended to be vertically mounted on a wall or stand. In addition to touch, the PPI supports input with the included stylus, which makes it a good replacement for whiteboard purposes. Much attention has been paid to the silky texture of the touch surface, which is extremely pleasing to touch (“low-stiction”), as well as responsive and accurate. It supports an “unlimited” number of touches, so it’s highly suitable for multi-user collaborative applications.
While a PPI could be deployed in a public installation, it’s really intended for an office scenario, and as such includes a large Microsoft logo on its fairly thick bezel. Even so, we love using the one in our conference room.
The PPI line has been upgraded and rebranded as “Surface Hub“, and we’re looking forward to trying it out once it’s released.
PQ Labs is a Chinese manufacturer of popular infrared touch frames of all sizes, which can be ordered with or without integrated glass and support up to 32 simultaneous touches. We used a custom-made frame of about 12’×5’ for the Maxim lobby and it is working well now, though it took some effort to get it assembled and functioning properly, and technical support was limited. The PQ overlays are a good option for vertically-oriented multi-user applications in sizes above 55”.
The Baanto infrared touch frames use a patented sensing technology referred to as “ShadowSense” which provides improved performance over traditional IR sensing techniques. They are also especially resistant to dirt and spills, and are suitable for outdoor use. The frames are available in off-the-shelf sizes up to 85”, or in custom sizes up to 267”. The included software allows an integrator to tune the sensitivity of the device to detect objects within a specific size range, and to treat smaller objects like a stylus differently from larger ones like fingertips. The company has a produced a collection of short videos highlighting their distinguishing features.
We’ve not yet had the chance to use a Baanto product in an installation, but the 46” unit in our lab has proved to be very durable and responsive, so we look forward to deploying with it in the future. It is worth noting that Christie, a leader in high-quality display products, uses Baanto technology for the “interactivity kit” that adds touch sensing to their displays.
Multitaction products are vision-based solutions from Finland, which they describe as “cells”. These cells come only in 42” and 55” sizes but can be combined to create touch-sensing walls or tables of various sizes and orientations due to their very thin bezels. Cells are available with or without an integrated PC. The company encourages developers to use their proprietary “Cornerstone” SDK for application development, but the system can be configured to output TUIO for development in other frameworks.
We deployed a Multitaction touch wall in a corporate lobby using six 55” cells in a portrait orientation and found the responsiveness and display quality to be better than the old Pixelsense products (such as the Samsung SUR-40) or something custom-built, but not as good as a pro-cap display. We also learned that the units can get very hot, which should be accounted for in the design of any type of enclosure. In general we found the company’s customer support to be very good.
There are plenty of other products we’d like to review and compare here, but we didn’t want to wait until we had everything in the lab to share our experiences. In the short term we’re looking forward to getting our hands on newer products from PQ Labs, checking out PQ’s competitor Zaagtech, and trying the touch foils from Displax that can make any surface touch-sensitive. We’ll add products here as we get them into the lab; follow our blog for updates.