New production and testing technologies make high demands on positioning mechanisms. High positioning accuracy , repeatability and reliability is demanded. Corresponding measuring systems must be used. Internal laser interferometers with their highest resolution and accuracy offer more than other measuring systems.

The typical applications are:
- testing of semiconductor wafers
- optical and X ray step and repeat cameras
- pattern generators
- laser writing machines
-drilling machines
- production of large displays

Closed Loop Application
Precise positioning systems usually work in closed loop. Positioning errors measured by the laser measuring system are transferred to a control computer which secures corresponding position correction. Slower systems use personal computers or industrial computers with the usual processors. High speed applications require special control computers. LIMTEK has long experience with laser measuring techniques and positioning control loops designs and adapts the positioning loop according to customers requirements.

Plane Mirror Interferometer
Plane mirror interferometers are used for X-Y table measurements. Plane mirror reflectors are mounted on the moving table. Measurement in two axes (X, Y) or in three axes (X, Y1, Y2) is possible. In three axes measurement eventual table rotation can be computed from values Y1 and Y2. At plane mirror interferometer optical plane mirror convertor LS 20.3 (lamda/4 wave plate) is used.