High Precision Metrology Using SSI

SSI provides high precision measurement for MRF target maps and for final element verifications.  Calibration of the transmission element ensures accurate pixel scale and error mapping.  Reference wave error is calculated and removed for each measurement.

  • The cylinder has ~27 µm of departure and can be measured on the SSI using a transmission flat.
  • The full aperture of the transmission flat can be masked to capture a subaperture that is within the Nyquist limit of the system.
  • Stitching smaller subapertures together allowed us to measure the cylinder as the deviation from a flat.


Subapertures configurations
Subaperture configuration

Fringes from an off-axis subaperture


The measurement technique allowed for a reliable measurement to evaluate

the specifications for cylinder form and figure.