Optical Coherence Scanning Measurement Limit Boundaries on Vertical Tooling Cavity Sidewalls
Side-viewing prisms and polarized optical coherence gating extend sidewall slope scanning limits beyond eighty-five degrees in deep tooling cavities.
Numerical Aperture Limits
Meaning
Geometrical constraints that define the range of angles over which an optical system can accept or emit light. In the inspection of transparent plastic films, these boundaries determine the maximum tilt or curvature a surface can have before the sensor loses the return signal. A higher numerical aperture allows the measurement of steeper angles and rougher textures but typically reduces the working distance between the lens and the part.
Angle Acceptance
Sensors with restricted light gathering capability struggle to measure parts with complex geometries or high gloss. The numerical aperture limits of a displacement sensor dictate whether it can accurately profile the edge of a moulded lens where the surface curves sharply away from the detector.
Signal Intensity
Power of the reflected light reaching the detector drops when the numerical aperture is small. This becomes a problem when measuring dark or matte resins that absorb or scatter a large portion of the incident beam, requiring longer integration times that slow down the production line.
Metrology Capability
Selection of an optical head must account for the specific geometry of the part being inspected. If the numerical aperture limits are exceeded, the system will report missing data points or erroneous spikes, leading to false rejects in the quality control process.