Autocollimators are excellent measuring tools for many applications, such as adjustments or characterizations of precision mechanics, optics and instruments. Autocollimators have several characteristic error sources due to misalignment or nonideality of the collimator lens, the light source and the sensor. To fully characterize errors related to simultaneous engagement of both measurement axes of the autocollimator a two directional angle generator is necessary.
In this paper, VTT MIKES interferometric 2-directional small angle generator (I2D-SAG) with updated model for calibration of autocollimators is described. It generates angles around 2 orthogonal axes with high accuracy. The maximum range of the I2D-SAG is ±1000” for both axes. In calibration of a high quality autocollimator a standard uncertainty below 0.01” can be reached.
In addition, preliminary results of a comparison of I2D-SAG and PTB Spatial Angle Autocollimator Calibrator (SAAC) instrument are presented. This is the first comparison between 2D autocollimator calibration systems. In this comparison, a good agreement was reached in characterization of an electronic autocollimator over 900”×900” range.
A new Aperture Centring Device (ACenD) for precisely positioning small apertures with respect to the autocollimator’s optics has been developed. With the new device, differences in the angle response of autocollimators between the calibration at a laboratory and their subsequent application in the slope measuring profilers are significantly minimized. Evaluation of the device with a circular aperture size of d=2.5 mm was carried out in different laboratories. It was verified that the ACenD is capable of achieving a reproducible aperture alignment < 0.1 mm. The device is a substantial aid for the operation of slope measuring profilometers and enables the measurable, documentable, and transferable positioning of apertures that did not exist before.