When performing interferometric measurements in ambient conditions, air refractive index fluctuations can be a limiting factor: variations in surrounding pressure, temperature, and humidity can cause measurement inaccuracies in the tens of parts-per-million (ppm) range. Especially for applications where highest precision is key, these deviations have to be measured and accounted for.
With the ECU (Environmental Compensation Unit), attocube offers the first interferometer compensation unit providing fully automated air refractive index correction down to the sub-ppm range: when connected to the IDS interferometer, the ECU automatically detects the absolute sensor/target separation, calculates the actual air refractive index, and compensates any incremental measurement. In addition, the environmental parameters are recorded and stored for future reference.