The invention relates to a shutter for an optical imaging system. An amount of opaque fluid is moved in a planar capillary space to open and close the shutter. Depending on the position of the opaque fluid with respect to an optical path passing through the capillary space, the fluid opens or blocks the optical path. In an embodiment, the opaque fluid is moved by a pressure differential caused by a diaphragm which is coupled to a piezoelectric actuator. In another embodiment, the opaque fluid is moved by electrostatic forces.