In this case the heat driven by the finger is detected, which is greater when there is a ridge than when there is a valley. A silicon component has been developed with a matrix of pixels called "FingerChip", that is, "finger integrated circuit", each of which is covered with a layer of pyroelectric material in which a change in temperature translates into a change in the load distribution of its surface. The image is in the gray scale that has the right quality even with the finger worn, with dirt, with grease or with humidity. The sensor has a robust protective layer and can provide a dynamic output.