| Popis: |
An autocollimator calibration facility has been developed based upon both a precision rotary table and a sine-bar. The traceability of the system is through sub-division of the circle and hence to the SI unit of angle, and does not require traceability to the definition of the metre. The rotary encoder that measures the angle of the rotary table is calibrated through circle closure techniques to a combined standard uncertainty of 0.013 arcsec at 5° intervals. The rotation of the sine-bar is measured by two interferometers, and together with the rotary encoder, enables calibration of the scale factor of an autocollimator to a combined standard uncertainty of 1.8 × 10 -5. © 2013 BIPM & IOP Publishing Ltd. |
