For high accuracy measurements, the NSI-OP-5929 Optical Measurement System (NSI Patent No.5,408,318) can be added to a vertical or horizontal scanner to improve the probe position
accuracy. This optional measurement system dynamically tracks probe X and Y positions in real time. The system also permits automated generation of probe X, Y and Z calibration error tables. The system uses laser interferometers for the X and Y position feedback, and a patented NSI optical subsystem for measuring the probe’s straightness. The NSI Antenna Measurement Software with built-in monitoring and calibration routines controls the optical system. The system includes NSI’s active position correction software, which uses the measured errors to actively move to a corrected position on the fly while acquiring near-field data (NSI Patent No. 5,419,631). The system consists of a spinning Z-laser, Z-sensor, Optics Box, laser interferometers, and software. NSI's standard optical products and subsystems are listed below.