Light condensing unit with guided movement mechanisms

A light condensing unit is located between a radiation source and a sample being analysed. The unit comprises a mirror 41 located on a holding shaft 6 that is arranged to collect light, such as cathode luminescence (cathodoluminescence), coming from the sample that is being irradiated. The unit comprises moving mechanisms 81, 82 and 83 to move the shaft in X axial, Y axial and Z axial directions respectively using corresponding moving guides 811, 821 and 831; tilt mechanism 9 with a tilt guide arranged to tilt the holding shaft around an axis 9R that is orthogonal to the direction of irradiation and to the centre axis of the shaft; and a rotation mechanism 10 with rotation guide 101 that rotates the holding shaft around its centre axis. These mechanisms allow the focusing mirror to be moved independently in each of the directions, simplifying positional adjustments and improving positional repeatability.