# Full-field Fourier ptychography (FFP): spatially varying pupil modeling and its application for rapid field-dependent aberration metrology

## TL;DR

This paper introduces a full-field Fourier ptychography method that efficiently models and measures spatially varying aberrations across an entire field of view, enabling rapid and robust aberration metrology without moving parts.

## Contribution

The paper presents a novel FFP scheme that recovers full-field aberration coefficients with significantly fewer parameters and faster computation, improving upon previous Fourier ptychography methods.

## Key findings

- Aberration coefficients can be recovered in approximately 35 seconds using a CPU.
- The method reduces optimization degrees of freedom by over two orders of magnitude.
- No moving parts or calibration targets are required for aberration measurement.

## Abstract

Digital aberration measurement and removal play a prominent role in computational imaging platforms aimed at achieving simple and compact optical arrangements. A recent important class of such platforms is Fourier ptychography, which is geared towards efficiently creating gigapixel images with high resolution and large field of view (FOV). In current FP implementations, pupil aberration is often recovered at each small segment of the entire FOV. This reconstruction strategy fails to consider the field-dependent nature of the optical pupil. Given the power series expansion of the wavefront aberration, the spatially varying pupil can be fully characterized by tens of coefficients over the entire FOV. With this observation, we report a Full-field Fourier Ptychography (FFP) scheme for rapid and robust aberration metrology. The meaning of 'full-field' in FFP is referred to the recovering of the 'full-field' coefficients that govern the field-dependent pupil over the entire FOV. The optimization degrees of freedom are at least two orders of magnitude lower than the previous implementations. We show that the image acquisition process of FFP can be completed in ~1s and the spatially varying aberration of the entire FOV can be recovered in ~35s using a CPU. The reported approach may facilitate the further development of Fourier ptychography. Since no moving part or calibration target is needed in this approach, it may find important applications in aberration metrology. The derivation of the full-field coefficients and its extension for Zernike modes also provide a general tool for analyzing spatially varying aberrations in computational imaging systems.

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Source: https://tomesphere.com/paper/1905.00162