A tactile sensor turns contact with an object into a measurement. For a robot gripper, this can provide information about the contact surface that an external camera alone does not capture.
An optical example
GelSight is one example of tactile sensing. A soft sensing surface conforms to an object when pressed against it. An optical system observes that deformation so software can characterize the contacting surface. The manufacturer describes applications in surface measurement and robotics. This describes one sensor family; it does not mean every tactile sensor uses a camera. GelSight technology.
Research on the Taxim simulator describes a GelSight sensor as a soft elastomer coupled to an optical arrangement. Its simulation separates surface geometry, optical response, and motion of surface markers to model contact images. That distinction matters: an image of deformation is an input to a measurement method, not automatically a calibrated force reading. Taxim research paper.
Questions to ask before using one
For an illustrative gripper project, start with the decision the measurement must support. Detecting first contact, estimating surface shape, and detecting an object slipping are different tasks. Define the desired output before choosing hardware.
A practical evaluation could use the same test object at several orientations and contact loads. Record the raw output, the calibration procedure, and the repeatability of the derived measurement. Keep unsuccessful contacts in the results instead of selecting only clear images.
If the controller must react to slipping, also measure the time between physical contact changes and the controller receiving usable data. A detailed image that arrives too late may not serve that particular control task. These are proposed evaluation steps, not performance claims about a specific product.
What the sensor does not prove
A contact measurement does not by itself demonstrate safe handling or reliable manipulation. The gripper, controller, calibration, and test conditions all matter. Report the measured quantity and its conditions explicitly: “surface image captured” and “object held successfully” are different observations.