Working Distance
Non-contact measurement of moving webs requires a physical gap between the sensor optics and the substrate surface. The optical standoff defines this clearance distance, allowing high-speed inspection without risking physical contact. It ensures that the focal plane coincides with the surface of the paper or film.
This parameter determines both the field of view and the spatial resolution of the imaging system.
Sensor Protection
Industrial papermaking and converting environments are characterized by high speeds, dust, and occasional web breaks. Maintaining a substantial optical standoff protects the delicate lens surfaces from contamination by paper dust, aerosolized coatings, or moisture. If the sensor sits too close to the web, a sudden tear in the paper can cause the flying sheet to strike and destroy the optical assembly.
A larger gap allows for the installation of protective air knives that blow a continuous stream of clean air across the lens to prevent debris accumulation. This setup ensures continuous operation without frequent stops for manual cleaning.
Process Integration
Integrating sensors into existing press lines requires a compact form factor. However, increasing the standoff distance usually requires larger lenses to maintain the same light-gathering efficiency. The final hardware choice represents a balance between physical clearance and optical performance.
