A device includes a first portion, an information element, a second portion, and an encoder element. The first portion includes a planar substrate and at least one optical element coupled to the substrate. The optical element has an axis and the axis is substantially normal to the substrate. The information element sensor is coupled to the substrate. The information element sensor is configured to provide an information signal. The second portion includes a membrane configured to couple to the planar substrate. The membrane has a contact surface configured to couple with tissue. The encoder element is coupled to the membrane. The information signal corresponds to proximity of the encoder element.
