# Rapid wavefront shaping using an optical gradient acquisition

## TL;DR

This paper introduces a faster method for deep tissue imaging by using gradient descent instead of slow sequential scanning to correct light scattering in tissues.

## Contribution

The novel contribution is a rapid wavefront shaping system using gradient descent and a non-invasive score function for high-resolution imaging.

## Key findings

- Gradient descent optimization enables simultaneous updates of all modulation parameters for faster correction.
- The system's complexity is independent of the number of parameters, unlike previous methods.
- The technique was successfully demonstrated in a coherent confocal microscope for aberration correction.

## Abstract

Wavefront shaping systems enable deep tissue imaging by correcting scattering aberrations, but estimating optimal modulation correction is challenging, since it depends on the unknown tissue structures. Most current methods use slow coordinate descent algorithms, which sequentially scan all modulation parameters and query them independently, thus their complexity scales prohibitively with the number of parameters. We introduce a rapid wavefront shaping system, replacing coordinate descent with gradient descent optimization. To this end, our system acquires a gradient vector, which allows simultaneous update of all modulation parameters. We start with a non-invasive, guide-star-free score function to assess modulation quality and analytically derive its gradient with respect to all modulation parameters. Although the gradient depends on unknown tissue structure, we show it can be inferred from optical measurements. This enables fast, high-resolution wavefront correction with complexity independent of parameter count. We demonstrate the system’s effectiveness in correcting aberrations in a coherent confocal microscope.

The authors present a rapid wavefront shaping system for fast, high-resolution imaging deep inside scattering tissue. It does this by optically acquiring the focusing score’s gradient, a method orders of magnitude faster than previous techniques.