Cause of background intensity variations in laser phase plate images

Ascertain the cause of the spatial background intensity variations observed in laser phase plate phase‑contrast TEM images of single‑particle samples and quantify their impact, distinguishing phase‑contrast enhancement of ice thickness or composition inhomogeneities from other potential imaging artifacts.

Background

Representative laser phase plate images show brighter and darker background regions around particles, which are not expected in defocus‑only images.

Understanding whether these modulations arise from enhanced sensitivity to vitreous ice inhomogeneity or other effects (e.g., beam alignment, cavity fringes) is important for particle picking, CTF estimation, and downstream reconstruction fidelity.