Non-iterative aberration retrieval based on the spot shape around focus

•A non-iterative, robust, aberration retrieval method capable of determining the most common aberrations present in an optical system from just three measurements of the intensity distribution taken near focus.•For individual aberrations, the aberration indicators derived vary almost linearly with magnitude of aberration up to 0.13λ rms. For context, a value of 0.13λ rms corresponds to a Strehl ratio of ∼0.44 which would translate to a decrease of the PSF peak intensity by about 56%.•In the presence of multiple primary aberrations, the method is found to be reliable for a total rms wavefront deviation below 0.10λ (Strehl ratio of 0.68).•The presented technique is well suited for retrieving the most common aberrations present in imaging systems and therefore could from a useful component of an adaptive optics setup for wavefront correction in optical microscopy and in particularly for super-resolution microscopes. Being iteration free would make any correction routine fast which is advantageous for biomedical imaging where limiting photon damage is important. A non-iterative, robust, aberration retrieval method to determine primary aberrations by utilizing the intensity distribution at and around focus is presented. The primary Zernike aberrations (coma, spherical aberration and astigmatism) are retrieved by fitting a set of orthogonal circle functions within the central region of the intensity distribution recorded at 3 different axial planes, typically taken at best focus and either side of focus. Aberration indicators are derived from these fits for each primary aberration and it is shown that these indicators can be used for aberration retrieval. The selected indicators vary almost linearly with the magnitude of aberration up to 0.13λ rms, corresponding to a Strehl ratio of 0.44. In the presence of multiple primary aberrations, the method is found to be reliable for a total rms wavefront deviation below 0.10λ (Strehl ratio of 0.68). This approach is linear and non-iterative and will therefore be beneficial for applications where speed and limiting photon exposure is important such as wavefront correction in biomedical imaging.