Variable orientation illumination-pattern rotator

A structured illumination microscopy instrument comprising:

• a splitter arranged to receive and split a coherent beam of light from a light source into three or more beams of light;
• a rotation selector;
• one or more mirror clusters;
• and
• an objective,
• wherein the rotation selector is arranged such that the three or more beams of light, which are linearly polarized, strike the rotation selector and undergo a first reflection that directs the three or more beams of light towards the one or more mirror clusters,
• wherein the one or more mirror clusters are arranged to receive the first reflected three or more beams of light, rotate a linear polarization of the first reflected three or more beams of light by at least one of a plurality of different predefined angles about an axis directed in a propagation direction of the first reflected three or more beams of light, and reflect the three or more rotated beams of light away from the one or more mirror clusters,
• wherein the objective is arranged to receive the three or more rotated beams of light and focus the three or more rotated beams of light to form an interference pattern in a focal plane, and
• wherein the rotation selector is operable to select an angle by which to rotate a linear polarization of light.