Due to the specific imaging structure of neutron imaging system, the geometric unsharpness is unavoidable in neutron photographic images after imaging.

This study aims to design a geometric unsharpness correction method for neutron photographic image based on improved Richardson–Lucy (RL) algorithm.

First, according to the geometric unsharpness of the neutron photographic image, the mathematical model of the point spread function (PSF) was established. Then, the Laplace operator and median filter were used to remove the PSF related gamma spots noise (GSN) in the image, and the neutron photographic image was restored by RL algorithm. Finally, the restoration quality of neutron photographic images of the line-pair sample was evaluated using average gradient (AG) and spatial frequency (SF).

The results of the line-pair sample demonstrate that compared with four existing correction algorithms of geometric unsharpness, the proposed method improves AG and SF by 60.23% and 29.90%, respectively.

The proposed method of this study can effectively correct the geometric unsharpness caused by the amplification of gamma spots noise in the process of neutron photographic image restoration, providing an important technical support for performing high-resolution neutron radiography.