Michelson interferometer configurations
In the standard configuration of a PICOSCALE sensor head, the reference mirror is coated to one of the side surfaces of the beam splitter cube.
Front reference - look around the corner
As a variant, the beam splitter can be coated to the front surface of the beam splitter cube. This can be advantagous in setups with certain space constraints as the sensor head can "look around the corner".
External reference - differential measurements
Another variant of PICOSCALE sensor heads do not have a reference mirror at all. This is unique for Michelson interferometers and allows to perform differential measurements of two targets with several advantages. Please also see our pre-aligned differential measurement head: Read more...
The standard PICOSCALE C01 Sensor Head has one port of the beam splitter unused for interferometer purposes. Typically, this part of the beam splitter has a coarse grinding so that one can use it as a view port for alignment (see schematic). This view port we call SmarAlign window in the following.
When the pilot laser beam of the PICOSCALE is activated, the visible light can be used to trace the propagation path to the target mirror as well as its reflection back to the sensor head. If the reflected beam hits the sensor head, one can see two spots in the SmarAlign window. By fine adjustment of the tip/tilt angle of the sensor head, these two spots can be overlapped which means the two beams can interfere.
Advantages of Michelson Interferometers
Michelson Interferometers have several advantages in terms of displacements sensing accuracy and flexibility.
Learn more in this article: Advantages of Michelson interferometers compared to other architectures