A method of performing sub-surface imaging of a specimen in a charged-particle microscope of a scanning transmission type, comprising the following steps: - Providing a beam of charged particles that is directed from a source along a particle-optical axis (B') through an illuminator so as to irradiate the specimen; - Providing a detector (26;30;32;34) for detecting a flux of charged particles traversing the specimen; - Causing said beam to follow a scan path across a surface of said specimen, and recording an output of said detector as a function of scan position, thereby acquiring a scanned charged-particle image / of the specimen; - Repeating this procedure for different members n of an integer sequence, by choosing a value P n of a variable beam parameter P and acquiring an associated scanned image I n, thereby compiling a measurement set M = {(I n, P n)}; said variable beam parameter being focus position along said particle-optical axis; - Using computer processing apparatus to automatically deconvolve the measurement set M and spatially resolve it into a result set representing depth-resolved imagery of the specimen, characterized in that: - Said scanned image / is an integrated vector field image, obtained by; ▪ Embodying said detector to comprise a plurality of detection segments; ▪ Combining signals from different detection segments so as to produce a vector output from the detector at each scan position, and compiling this data to yield a vector field; ▪ Mathematically processing said vector field by subjecting it to a two-dimensional integration operation. - Providing a beam of charged particles that is directed from a source along a particle-optical axis (B') through an illuminator so as to irradiate the specimen; - Providing a detector (26;30;32;34) for detecting a flux of charged particles traversing the specimen; - Causing said beam to follow a scan path across a surface of said specimen, and recording an output of said detector as a function of scan position, thereby acquiring a scanned charged-particle image / of the specimen; - Repeating this procedure for different members n of an integer sequence, by choosing a value P n of a variable beam parameter P and acquiring an associated scanned image I n, thereby compiling a measurement set M = {(I n, P n)}; said variable beam parameter being focus position along said particle-optical axis; - Using computer processing apparatus to automatically deconvolve the measurement set M and spatially resolve it into a result set representing depth-resolved imagery of the specimen, - Said scanned image / is an integrated vector field image, obtained by; ▪ Embodying said detector to comprise a plurality of detection segments; ▪ Combining signals from different detection segments so as to produce a vector output from the detector at each scan position, and compiling this data to yield a vector field; ▪ Mathematically processing said vector field by subjecting it to a two-dimensional integration operation. ▪ Embodying said detector to comprise a plurality of detection segments; ▪ Combining signals from different detection segments so as to produce a vector output from the detector at each scan position, and compiling this data to yield a vector field; ▪ Mathematically processing said vector field by subjecting it to a two-dimensional integration operation.