Abstract: The scanning system of a scanning microscope for the imaging of phase structures is adapted to form a scanning pattern which is free from discontinuities. The detector is divided into a number of sub-regions with the direction of the dividing lines of the detector being adapted to the scanning pattern. The scanning pattern is notably meander-shaped and the detector is divided into four quadrants. The deflection system is digitally controlled and the microscope may be an electron microscope.

Abstract: In a scanning electron microscope, a periodic structure in the object plane is used for the detection of the focus condition of a spot-focussed electron beam scanning an object in order to correct defocusing and astigmatism in the scanning electron beam spot. To achieve this the detector comprises a plurality of individual elements which can be pair-wise read and an electronic circuit for forming a control signal for controlling the excitation of a spot-forming lens and a stigmator, respectively, from signals representing movement of the electron interference pattern at the detector, relative to the object scan, due to an out of focus condition. The signals are derived from corresponding pairs of detector elements which are situated at a fixed distance from each other in order to correct the focus and compensate for the astigmatism in the electron beam respectively. In the case of astimatism, signals from at least two pairs of detector elements spaced in directions at right-angles to one another, are used.

Abstract: In order to reduce object contamination during the examination or machining of the object in an electron beam apparatus, an anti-contamination diaphragm is provided in place of the customary diaphragm. The anti-contamination diaphragm has a central aperture which corresponds to a customary diaphragm aperture, and a concentric annular aperture for transmitting a non-paraxial hollow beam which irradiates a ring around the paraxial focus on the object. The conical hollow anti-contamination beam forms a barrier against contaminating residual gas molecules, notably hydrocarbon molecules.