Analysis of Systematic Error of Autocollimating Null Indicator and the Ways to Eliminate It

Dynamic goniometers are among the most precise non-contact optical angle measuring systems, which provide complete measuring process automation. The optical interaction with the test object reflecting faces in these systems is implemented by the null-indicator, which is extremely sensitive device and thus multitude of goniometer error sources are related to it. This article focuses on one specific systematic error typical for dynamic goniometers that utilize null-indicators based on autocollimation principle. This error originates from null-indicator internal components poor adjustment together with certain measurement conditions. Based on the experimental data obtained, the accuracy of the said null indicator was analyzed and the main sources of the systematic errors were identified and possible measure to eliminate those errors were proposed.