Adaptive optics in a multiphoton microscope

The following movie shows the correction of a DM-induced aberration in a second-harmonic microscope using model-based wavefront sensorless adaptive optics.

The images refer to a 2D section approximately 33 µm deep inside collagen fibre extracted from rat tail. At sample time \( k = 0 \), the DM introduces a phase aberration with \( N \) aberration modes. Between sample time \( k = 1 \) and sample time \( k = 8 \) inclusive, \( N + 1 \) trial aberrations are applied and the corresponding values of an image quality metric \( \tilde{y} \) are measured. Starting from sample time \( k = 9 \), the aberration correction is applied.

To correct the aberration, the least-squares estimate of the (unknown) aberration is computed using the measurements of the image quality metric \( \tilde{y} \). This involves solving a non-convex optimisation problem. Further details are found in the following paper (pdf).

T. van Werkhoven designed and implemented the second-harmonic microscope. Dr. Hoa Truong prepared the specimen. The experiment was performed in the Molecular Biophysics department in Utrecht, in collaboration with the Leiden Observatory.