A STEM system is disclosed wherein an imaging system is used to image the electron scatter pattern plane of the HAADF detector onto a two-dimensional array detector. A data acquisition system stores and processes the data from the two-dimensional array detector. For each illumination pixel of the STEM, one frame of data is generated and stored Each frame includes data of all scattered angles and can be analyzed in real time or in off-line at any time after the scan. A method is disclosed for detecting electrons emitted from a sample by detecting electrons scattered from the sample and generating plurality of corresponding signals, each signal indicative of scattering angle of a scattered electron; generating a plurality of signal groups, each signal group being a collection of signals of a user selected scattering angle.