Meaning
Non-contact optical measurement instruments evaluate surface topographies and distance profiles by projecting multi-wavelength light through dispersively focused lenses. Precision electronics production uses the chromatic confocal sensor to measure transparent layer thickness and silicon die tilt down to sub-micron resolution. The sensor splits polychromatic light into spectral wavelengths focused at distinct axial distances, mapping wavelength intensity directly to target distance.
Measurement range remains constrained by the focal dispersion range of the specialized optical head.
Optical Mechanics
Controlled chromatic aberration creates a spatial continuum of focused monochromatic focal points along the measurement axis. Light reflected from the target passes back through a pinpoint aperture onto a spectrometer that identifies the precise peak wavelength returned. Standard sensor designs operate without physical probe contact, eliminating surface damage risks on soft silicon die surfaces or wet adhesive beads.
Surface Interaction
Substrate reflectivity variations alter returned light intensity without distorting the calibrated distance output. Multi-layer assemblies allow simultaneously measuring top glass cover thickness and internal air gap distances in a single optical pass.
Thermal Limit
Thermal expansion within the sensor body shifts internal grating alignment during extended measurement cycles. Temperature variations modify the spectral calibration curve, requiring local ambient thermal stability during high-precision metrology operations.
