Optical force sensing is transforming human-machine interaction 

A robotic hand that can sense touch. A sleek oven front panel with no visible controls. A smartwatch whose housing itself becomes an input surface. In all of these applications, the surface takes on a new role. It no longer serves merely as a housing but becomes part of the interaction itself. 

“Surfaces are expected to offer more and more functions. Optical force sensing makes exactly that possible. The technology detects even minor surface deformations and converts them into actionable information about touch, pressure, and contact. This turns surfaces into active interfaces and expands possibilities for human-machine interaction — from household appliances to robotics,” says Christian Feierl, Senior Product Manager at ams OSRAM.

Getting more information from every touch
For product surfaces to offer more than conventional buttons or touch surfaces, they must not just detect whether contact has occurred. They also need to extract as much information as possible from each touch and capture it at the point of contact. 

This becomes particularly demanding when touch and pressure are applied across multiple points rather than at a single point. For example, whenever a robotic hand lifts a tool, it must detect how the forces are distributed across several of its fingers and how those forces change during the gripping process. Only by combining multiple contact points can a complete picture of the interaction be created.

This is exactly where the Analog Frontend AS7160 comes in. It controls up to eight optical frontends simultaneously and captures data from multiple sensor points in parallel. This enables robotic hands, for example, to analyze pressure information across multiple contact points to obtain a more accurate picture of the gripping process.

The high sensitivity of the system is a decisive factor here. The AS7160 detects surface movements of just 0.22 micrometers. Deformations far smaller than the diameter of a human hair can thus be detected. This allows the sensors to identify the slightest changes in the force applied — even behind metal or in wet conditions — and detect early on when a tool moves within the robotic hand.

The more information a machine obtains from a touch, the better it can understand its surroundings. Equally important, however, is the question of where this information is captured. The Optical Frontend SFH7065 is designed for exactly this purpose. As a so-called side looker, the sensor unit detects changes laterally along the surface rather than from above, thus expanding the possibilities for integrating sensing technology into complex geometries: in the finger tips, joints, along the finger sides, as well as in the curved areas of a robotic hand. The lateral sensing capability makes it possible to measure both compressive and shear forces. This enables the sensors to detect not only how firmly an object is being gripped, but also whether it is moving within the grip or starting to slip. Combined with top lookers, developers can place sensors precisely where touch and forces actually occur. This brings the sensing technology into the product’s structure. It is no longer merely protected or covered but actively contributes to detection and control.

More than just touch: pressure as an additional source of information
The same principles can be applied to everyday applications, where optical force sensing opens up new possibilities for user interaction.

In household appliances such as ovens, controls can completely disappear behind a closed glass front. Multiple sensor points can form dedicated control zones without the need for individual controls to be visible. Even while wearing an oven mitt, a light touch can open a menu, while deliberate pressure activates a function. 

Similarly, additional functions can also be integrated directly into existing surfaces in compact devices. When it comes to smartwatches, for example, the housing itself serves as the input surface. A long press on the side of the watch could start a workout mode, while a short press could answer a phone call. This enables additional input options without changing the product’s design or form factor.

Optical force sensing does more than just detect touch — it turns it into an additional source of information. What is possible today in robotics, household appliances, and wearables points to a broader development: Products are increasingly developing a digital sense of touch, enabling them to interact with their surroundings in more differentiated ways.
 

More insights here: Replace mechanical buttons with smart surfaces