Interferometric 2D small angle generator for autocollimator calibration

Abstract

Small angle generators are simple devices for providing small angles traceable to the definition of the SI-unit radian. The most accurate ones use a laser interferometer for measurement of angular displacement. Small angle generators used for autocollimator calibration usually create angles around a single axis. A two-directional angle generator would be preferable, as it could more efficiently reveal artefacts related to angular displacement across both axes, such as orthogonality of the autocollimator's measuring axes. Characterizing errors depending on one axis only would also be easier, as the setup needs to be aligned only once for studying both axes of the autocollimator. We describe a novel interferometric two-directional small angle generator which we have built and tested for autocollimator calibration. The range is ±1000″ for both axes. The estimated standard uncertainty for full range is 0.0036″ for the horizontal and 0.0053″ for the vertical direction.

Research on Focal Length Measurement Scheme of Self-Collimating Optical Instrument Based on Double Grating

“…At a grating pitch of 70 µm, when the focal length difference of two collimators is 1% , 3% , and 5% , the variation amount ∆W of moiré fringe width in the range of 0 • -10 • with different angles θ can be calculated using (7), as shown in Figure 3. When there is a slight difference in the focal length of two collimators, the width of moiré fringe changes significantly.…”

“…Currently, the collimator is developing towards the directions of lightweight and miniaturization. With regard to self-collimating optical instruments designed for various specialized fields, the focal length is one of the most important parameters of the collimator, and its accuracy plays a significant role in the use of precise optical systems [7,8]. However, the measurement accuracy of long focal length optical systems is easily affected by external factors, and the processing error of the lens in the manufacturing process also has significant influences on the measurement accuracy [1,9,10].…”

Sensor for the Characterization of 2D Angular Actuators with Picoradian Resolution and Nanoradian Accuracy on the Microradian Range

“…Traceability of autocollimators to the SI unit is obtained through a calibration against primary standards. Few National Metrology Institutes are able to calibrate autocollimators at the level of some tenths of microradian by means of top calibration facilities such as [7][8][9][10][11][12].…”

A Novel 2D Micro-Displacement Measurement Method Based on the Elliptical Paraboloid

“…Conventionally, the three main optical methods for angle measurement with high resolution and accuracy are: interferometers, internal-reflection and autocollimators [4][5][6][7][8]. An interferometer utilizes phase information to measure angular and linear displacement with high signal-to-noise ratio and high resolution [9]. The internal-reflection effect can make a wide range of devices very stable and compact with high resolution [10].…”