So multiple contact points at once is no problem as long as they are far enough apart to differentiate them. “Does it support multiple contacts at once?” Make the “thumb” longer (increase surface area) and you have overall less pixel per area therefore less sensitivity. “How long of a “thumb” can this still work with?”

Posted in digital cameras hacks, Machine Learning, Multitouch Hacks Tagged machine learning, optical, photometric stereo, structured light, touch sensing Post navigation And whilst we’re talking about using cameras as sensors, here’s a neat way to use optical fibers to read multiple light-gates with a single camera and OpenCV.

We’ve not covered all that many optical sensing projects, but here’s one using a linear CIS sensor to turn any TV into a touch screen. The system is so sensitive that it can reportedly detect its own posture by observing the deformation of the skin due its own weight alone! By directly estimating normal and shear force components the direction of the contact could be resolved to 5 degrees. The camera image is fed straight into a pre-trained machine learning system (details on this part of the system are unfortunately a bit scarce) which directly outputs an estimate of the contact shape and force distribution, with spatial accuracy reported good to less than 1 mm and force resolution down to 30 millinewtons. The novelty here is the way they combine both photometric stereo processing with other structured light techniques, using only a single camera. From there, machine learning can be used to estimate the shear and normal force components of the contact with the skin, over the entire surface, by observing how the internal envelope distorts the structured illumination. The first step is to place a soft and compliant outer skin over a rigid metallic skeleton, which is then illuminated internally using structured light techniques. Intended for dexterous manipulation systems, the system is constructed from easily sourced components, so should scale up to a larger assemblies without breaking the bank. A team from the Max Planck Institute for Intelligent Systems in Germany have developed a novel thumb-shaped touch sensor capable of resolving the force of a contact, as well as its direction, over the whole surface of the structure.

Touch sensor output bouncing