Defocus Aberration Theory Confirms Gaussian Model in Most Imaging Devices

TL;DR

This paper confirms that the Gaussian model accurately describes defocus aberration in most imaging devices, enabling efficient depth estimation from 2D images by leveraging optical theory and empirical validation.

Contribution

It provides a theoretical and empirical validation that the Gaussian model effectively represents defocus aberration in typical imaging devices, supporting real-time depth estimation.

Findings

Gaussian model fits defocus aberration with less than 1% MAE

Applicable to a range of focused depths from 1 to 100 meters

Supports real-time depth estimation in imaging applications

Abstract

Over the past three decades, defocus has consistently provided groundbreaking depth information in scene images. However, accurately estimating depth from 2D images continues to be a persistent and fundamental challenge in the field of 3D recovery. Heuristic approaches involve with the ill-posed problem for inferring the spatial variant defocusing blur, as the desired blur cannot be distinguished from the inherent blur. Given a prior knowledge of the defocus model, the problem become well-posed with an analytic solution for the relative blur between two images, taken at the same viewpoint with different camera settings for the focus. The Gaussian model stands out as an optimal choice for real-time applications, due to its mathematical simplicity and computational efficiency. And theoretically, it is the only model can be applied at the same time to both the absolute blur caused by depth in a single image and the relative blur resulting from depth differences between two images. This paper introduces the settings, for conventional imaging devices, to ensure that the defocusing operator adheres to the Gaussian model. Defocus analysis begins within the framework of geometric optics and is conducted by defocus aberration theory in diffraction-limited optics to obtain the accuracy of fitting the actual model to its Gaussian approximation. The results for a typical set of focused depths between $1$ and $100$ meters, with a maximum depth variation of $10\%$ at the focused depth, confirm the Gaussian model's applicability for defocus operators in most imaging devices. The findings demonstrate a maximum Mean Absolute Error $(\!M\!A\!E)$ of less than $1\%$, underscoring the model's accuracy and reliability.