For some applications, such as phase contrast electron microscopy, defocused images can contain useful information. Multiple images recorded with various values of defocus can be used to examine how the intensity of the electron wave varies in three-dimensional space, and from this information the phase of the wave can be inferred.
For certain applications, such as phase contrast electron microscopy, unfocused images can contain valuable information. Multiple images captured with varying degrees of defocusing can be utilized to investigate how the intensity of the electron wave changes in three-dimensional space, and from this data, the wave's phase can be deduced.