RLD10 differential interferometer

Differential interferometers allow measurement relative to defined reference.

The differential head is designed with a unique optical scheme to achieve a low SDE performance.  Integrated beam steerers allow for pitch and yaw adjustment during set up which improves the alignment process (only suitable for plane mirror applications).

The RLD10-X3-DI detector head has been designed to mount to the external wall of a process chamber via a simple three-pin mount. There is no need to enter the chamber to align the detector head – integral beam steerers allow independent pitch and yaw adjustment of reference and measurement beam – and the design of the mounting system allows the detector head to be removed and repositioned with minimal effect on system alignment.

Features and benefits

  • Exceptional metrology -ppb frequency stability and ultra low cyclic error, allowing output resolutions to 38.6 pm.
  • Differential configurations – measures the relative position of the stage relative to the column, therefore eliminating common mode errors such as motion of the chamber side wall associated with environmental fluctuations.
  • Rapid alignment – simple alignment from outside the vacuum chamber using four integrated beam steerers to overcome chamber and mirror mounting tolerances.


Axis travel 0 m – 1 m
Resolution (resolution configured with RLU) Analogue quadrature = λ/4 (158 nm)
Digital quadrature = 10 nm
RPI20 resolution = 38.6 pm
System non-linearity error* (SDE)

*excludes interface

<±1 nm below 50 mm/sec with >70% signal strength
<±6 nm at 1 m/sec with >50% signal strength
Maximum speed Up to 1 m/s
The differential interferometer detector head is often configured with the Renishaw RLU20.  The high stability of the RLU20 laser source, combined with the performance of the differential interferometer head, is the ideal choice for measurements within vacuum chambers and other strictly controlled environments.


RLD10 differential interferometer