A positioning assembly (100, 200) including a base part (110, 210) and a holder part (120, 220) for holding a device (130, 630), the assembly further including a motor for driving a displacement mechanism mounted to the base part, the assembly (100, 200) being configured to adjust a position of the holder part (120, 220) relative to the base part (110, 210) between a retracted position and an extended position, along a linear displacement axis extending in longitudinal direction (z), wherein - the base part (110, 210) comprises a first guide rail extending in the longitudinal direction; - the holder part (120, 220) comprises a second guide rail extending in the longitudinal direction; - the base part (110, 210) and the holder part (120, 220) are arranged parallel to each other and are connected via a slide link (140, 240) which is configured to slide on each of the first and second guide rails, and - the slide link (140, 240) is coupled to the displacement mechanism, which is configured to displace the slide link (140, 240) relative to the base part in longitudinal direction (z), characterized in that: the holder part (120, 220) is moveably coupled to the base part (110, 210) via a coupling arrangement configured such that linear displacement of the slide link (140, 240) relative to the base part (110, 210) in one direction causes linear displacement of the holder part relative to the slide link (140, 240) in the same linear direction, the coupling arrangement comprising: ▪ a first linear drive surface (115, 215) provided on the base part (110, 210) in longitudinal direction (z), facing in a transverse direction (y); ▪ a second linear drive surface (125, 225) provided on the holder part (120, 220) in longitudinal direction (z), facing the first linear drive surface; and ▪ at least one drive wheel (145, 245) provided on the slide link (140, 240) having a rotation axis in a direction (x) perpendicular to the transverse direction (y) and the longitudinal direction (z), arranged such that a circumferential drive surface simultaneously engages the first linear drive surface (115, 215) on the base part (110, 210) and the second linear drive surface (125, 225) on the holder part (120, 220). - the base part (110, 210) comprises a first guide rail extending in the longitudinal direction; - the holder part (120, 220) comprises a second guide rail extending in the longitudinal direction; - the base part (110, 210) and the holder part (120, 220) are arranged parallel to each other and are connected via a slide link (140, 240) which is configured to slide on each of the first and second guide rails, and - the slide link (140, 240) is coupled to the displacement mechanism, which is configured to displace the slide link (140, 240) relative to the base part in longitudinal direction (z), the holder part (120, 220) is moveably coupled to the base part (110, 210) via a coupling arrangement configured such that linear displacement of the slide link (140, 240) relative to the base part (110, 210) in one direction causes linear displacement of the holder part relative to the slide link (140, 240) in the same linear direction, the coupling arrangement comprising: ▪ a first linear drive surface (115, 215) provided on the base part (110, 210) in longitudinal direction (z), facing in a transverse direction (y); ▪ a second linear drive surface (125, 225) provided on the holder part (120, 220) in longitudinal direction (z), facing the first linear drive surface; and ▪ at least one drive wheel (145, 245) provided on the slide link (140, 240) having a rotation axis in a direction (x) perpendicular to the transverse direction (y) and the longitudinal direction (z), arranged such that a circumferential drive surface simultaneously engages the first linear drive surface (115, 215) on the base part (110, 210) and the second linear drive surface (125, 225) on the holder part (120, 220). ▪ a first linear drive surface (115, 215) provided on the base part (110, 210) in longitudinal direction (z), facing in a transverse direction (y); ▪ a second linear drive surface (125, 225) provided on the holder part (120, 220) in longitudinal direction (z), facing the first linear drive surface; and ▪ at least one drive wheel (145, 245) provided on the slide link (140, 240) having a rotation axis in a direction (x) perpendicular to the transverse direction (y) and the longitudinal direction (z), arranged such that a circumferential drive surface simultaneously engages the first linear drive surface (115, 215) on the base part (110, 210) and the second linear drive surface (125, 225) on the holder part (120, 220).