Abstract: A SEM with an electrostatic objective lens 14, 16 and a detector 6, 8 for through-the-lens detection of secondary electrons (SEs) 24. A suitable collection efficiency of the SEs would require a comparatively high electric field near the surface of the specimen 18, whereas suitable voltage contrast (voltage range of the order of from 1 to 5 V) would require a moderate electric field near the surface of the specimen. In accordance with the invention an adjustable voltage source is provided in order to adjust at will the voltage of the final electrode 16 relative to the specimen, such that the voltage contrast and the collection efficiency can be adjusted to an optimum value in conformity with the measurement requirements.

Abstract: The invention relates to a SEM with an electrostatic objective lens 14, 16 and a detector 6, 8 for through-the-lens detection of electrons 24. In accordance with the invention a voltage contrast (voltage range of the order of magnitude of from 1 to 10 V) is achieved by subdividing this detector surface 9 into separate regions, preferably concentric annular regions 36 and 38, and by electronically combining the signals from these regions.

Abstract: Single beam color CRT of the beam tracking type having a display screen comprising a plurality of parallel phosphor lines, the CRT being equipped with a Distributed Main Lens type electron gun. The distributed main lens has a plurality of oblong grids which each have a single, oblong, beam passing aperture. The longitudinal axes of the grids and of the apertures are transverse to the direction of the phosphor lines. Correction means are provided to compensate for the astigmatism introduced by the main lens.

Abstract: A picture display device comprising a cathode ray tube (1) with an elongated display screen (8) and a deflection system (9) is described. The deflection power is reduced by two means. The deflection system (9) is arranged to scan the lines in the direction of the short axis (22) of the display screen (8), and the cone portion (3) of the cathode ray tube (1) has an elongated cross-section (54) whose aspect ratio is larger than or equal to the aspect ratio of the display screen (8), thereby enabling the deflection system (9), and in particular the line deflection subsystem (12), to be positioned closer to the electron beam envelope (51), which reduces magnetic losses.