a viewing direction towards one of the walls fig3 shows a viewing device 300 with one or two reflectors 301 e g one reflector for each eye arranged to redirect the viewing direction of a patient from a vertical direction 302 to a horizontal direction 303 thus the viewing device enables the patient to see the projected image when the reflector unit is in the second mode the viewing device may be in the form of a pair of glasses to be worn by the patient or a mirroring device which is fixed to the table 102 or the scanner 101 so that it is located in front of the eyes of the patient the signal generator 204 in fig2 may be a switch operable by the patient or clinical personnel for example when the patient is lying down on the table 102 the patient can change the mode of the mirror unit into the second mode so that the image from the image projector 105 is displayed on a surface which is visible to the patient for example in some scanners or in some scanner operations the ceiling may be visible to the patient and therefore the mirror unit may be operated to redirect the image to be displayed on the ceiling however often the scanner is constituted by a long narrow tunnel which surrounds the patient so that the only free viewing direction is along the tunnel parallel with the floor in this situation the image must be projected onto a wall surface adjacent one of.