"Hi Luis- The only two devices I know that would detect the gap optically would be either a laser micrometer: http://www.me-sensor.com/products/dimension-2D-3D-sensors/optical-micrometer/optoCONTROL_2500/index.html or a laser triangulation…"

"Hi Luis- I have a couple of solutions- where are you located?"

"Question- to what degree are direct digital sensors (physical property measurement to I2C, SPI or other) being adopted in the market place?"

"Reduce turbine gearbox oil changes that are costly and time consuming via real time detection of water intrusion & oil oxidation. The Measurement Specialties fluid property sensor (FPS) directly and simultaneously measures the viscosity,…"

"Or, if you are looking for ISO 10993 compliant adhesives that have a color change mechanism to know when the adhesive is cured, check this out: http://www.dymax.com/products/medical/index.php"