Shack-Hartmann versus reverse Hartmann wavefront sensors: experimental results

Area of Science:

• Optics and Photonics
• Optical Metrology
• Wavefront Sensing

Background:

• The Shack-Hartmann (SH) wavefront sensor (WFS) is a standard for wavefront error (WFE) measurement.
• The reverse Hartmann (RH) sensor offers an alternative configuration by inverting optical element positions.
• A double Fourier transform algorithm can process raw data from both sensor types.

Purpose of the Study:

• To experimentally validate the performance of a simplified reverse Hartmann (RH) WFS.
• To compare the WFE measurement accuracy of RH WFS with a reference SH WFS.
• To evaluate the efficacy of a double Fourier transform algorithm for both RH and SH sensor data.

Main Methods:

• Implementation of a simplified reverse Hartmann (RH) wavefront sensor (WFS).
• Acquisition of experimental data using both RH WFS and a reference Shack-Hartmann (SH) WFS.
• Application of a double Fourier transform algorithm to raw data from both sensor types.

Main Results:

• The reverse Hartmann (RH) sensor demonstrated comparable WFE measurement accuracy to the Shack-Hartmann (SH) sensor.
• The double Fourier transform algorithm proved effective for both RH and SH sensor data.
• Achieved WFE measurement accuracy was within approximately $\lambda/10$λ/10 RMS on the test bench.

Conclusions:

• The reverse Hartmann (RH) sensor is a viable alternative to the Shack-Hartmann (SH) sensor for wavefront error measurement.
• The double Fourier transform algorithm offers a unified approach for enhancing WFE reconstruction in both RH and SH sensors.
• Similar wavefront measurement accuracy is achievable with RH and SH sensors, particularly when employing advanced processing algorithms.