Tracking interferometer

from Wikipedia, the free encyclopedia

A tracking interferometer is a measuring device that can record 3D coordinates of object points. They consist of an interferometer whose laser beam can automatically follow a reflector. Laser trackers are used to digitize objects, measure large components in quality assurance , calibrate machine tools and in geodesy .

history

The basic patent for a self-tracking interferometer has been held by Kam C. Lau and Robert J. Hocken since 1986. This patent was licensed to Leica Geosystems from 1989 . In 1991, Leica sold the first such measuring system to the American aircraft manufacturer Boeing . Since then, the market for laser trackers has risen continuously despite the high price level. Today they have a firm place in industrial quality management .

principle

A laser tracker consists of a laser interferometer that can be rotated around the spherical reference surface . The alignment of the interferometer is measured with rotary encoders at two angles. By measuring the distance and two angles, points are measured in spherical coordinates, which can be converted into Cartesian coordinates with a coordinate transformation . The interferometer of the laser tracker works with several thousand laser pulses per second.

Applications

Laser trackers are used to digitize objects in industry and geodesy and work with several thousand laser pulses per second.

accuracy

The measurement uncertainty of tracking interferometers is influenced by the uncertainty of the interferometric length measurement, the stability of the optical center of rotation and the reflector used. The uncertainty of the interferometric length measurement is mainly influenced by the environmental influences and the length that the laser beam shines through the air. In order to determine changes in the ambient conditions, air pressure, humidity and temperature are measured during operation. With these measured values ​​and a model of the process, the systematic errors of the length measurement can be largely compensated for.

Individual evidence

  1. ↑ Kam C. Lau, Robert J. Hocken: Three and five axis laser tracking systems . US4714339 A, December 22, 1987 ( google.de [accessed February 24, 2017]).
  2. ↑ Philipp Jatzkowski: Resource-efficient calibration of 5-axis machine tools with tracking interferometers (=  Diss. RWTH Aachen ). Apprimus, ISBN 978-3-86359-011-6 , pp. 49-65 .

See also