A drive system for a projection screen in a swept surface volumetric three dimensional display, the drive system operable to cause the projection screen to reciprocate through an excursion distance at a screen reciprocating frequency relative to a projection system, the drive system including: an actuator arrangement for generating an input reciprocating force substantially at the screen reciprocating frequency through an input excursion distance; and a support structure for the projection screen, the support structure including a resonant mounting arrangement for the projection screen, the resonant mounting arrangement operably connected to the actuator arrangement and configured to allow the projection screen to reciprocate through the excursion distance, wherein the resonant mounting arrangement is configured to have a resonant frequency substantially equivalent to the screen reciprocating frequency on actuation of the actuator arrangement, the resonant mounting arrangement consisting of four planar spiral spring arrangements, and wherein the support structure for the projection screen includes a first support component having a square profile for supporting the projection screen, the first support component including four legs or struts downwardly extending from each corner of the projection screen; and a second support component comprising four planar platforms each to mount a planar spiral spring arrangement of the resonant mounting arrangement, each of the four planar spiral spring arrangements having a central region to which one leg of the first support component is attached to, wherein at rest each spiral spring arrangement 1170 is substantially coplanar with the planar platform and at the resonant frequency the central region flexes upwards and downwards, and wherein the second support component is attached to the first support component by coupling each of the four planar platforms to a respective downwardly extending leg of the first support component and wherein the resonant mounting arrangement is operably connected to the actuator arrangement having four linear actuators by directly connecting each of the four planar platforms to a respective linear actuator. an actuator arrangement for generating an input reciprocating force substantially at the screen reciprocating frequency through an input excursion distance; and a support structure for the projection screen, the support structure including a resonant mounting arrangement for the projection screen, the resonant mounting arrangement operably connected to the actuator arrangement and configured to allow the projection screen to reciprocate through the excursion distance, wherein the resonant mounting arrangement is configured to have a resonant frequency substantially equivalent to the screen reciprocating frequency on actuation of the actuator arrangement, the resonant mounting arrangement consisting of four planar spiral spring arrangements, and wherein the support structure for the projection screen includes a first support component having a square profile for supporting the projection screen, the first support component including four legs or struts downwardly extending from each corner of the projection screen; and a second support component comprising four planar platforms each to mount a planar spiral spring arrangement of the resonant mounting arrangement, each of the four planar spiral spring arrangements having a central region to which one leg of the first support component is attached to, wherein at rest each spiral spring arrangement 1170 is substantially coplanar with the planar platform and at the resonant frequency the central region flexes upwards and downwards, and wherein the second support component is attached to the first support component by coupling each of the four planar platforms to a respective downwardly extending leg of the first support component and wherein the resonant mounting arrangement is operably connected to the actuator arrangement having four linear actuators by directly connecting each of the four planar platforms to a respective linear actuator.