# Spatial frequency–based correction of the spherical aberration in living brain imaging

## TL;DR

This paper introduces Peak-F, a new method for correcting spherical aberration in brain imaging that improves accuracy by using a broader range of spatial frequencies.

## Contribution

The novel Peak-F method uses spatial frequency analysis to enhance spherical aberration correction in live brain imaging.

## Key findings

- Peak-F outperforms existing methods like Peak-C by addressing arbitrary neighbor selection and noise issues.
- Using fast Fourier transforms as a bandpass filter allows comprehensive coverage of low-frequency image domains.
- The Deep-C microscope system benefits from this improved correction method for clearer, high-resolution imaging.

## Abstract

Optical errors, including spherical aberrations, hinder high-resolution imaging of biological samples due to biochemical components and physical properties. We developed the Deep-C microscope system to achieve aberration-free images, employing a motorized correction collar and contrast-based calculations. However, current contrast-maximization techniques, such as the Brenner gradient method, inadequately assess specific frequency bands. The Peak-C method addresses this issue, but its arbitrary neighbor selection and susceptibility to the noise limit its effectiveness. In this paper, we emphasize the importance of a broad spatial frequency range for accurate spherical aberration correction and propose Peak-F. This spatial frequency–based system utilizes a fast Fourier transform as a bandpass filter. This approach overcomes Peak-C’s limitations and comprehensively covers the low-frequency domain of image spatial frequencies.