Structured illumination in inverted light sheet microscopy

A system comprising:

• a first optical element configured to spatially separate two optical beams;
• and
• a second optical element configured to spatially combine two optical beams, the second optical element comprising:
• a focusing element;
• and
• a linearly movable reflector configured to direct a first and a second of the two optical beams to a first point and a second point of the focusing element, wherein the first point and the second point of the focusing element are disposed axially symmetric relative to one another about a symmetry axis of the focusing element.

A sample interface for inverted fluorescence microscopy, comprising:

• a wavefront matching optic having a center of curvature beyond a plane forming a flat side of the wavefront matching optic;
• a transparent window disposed adjacent to the flat side of the wavefront matching optic;
• an illumination objective configured to form an illumination field on a sample by directing two optical beams through the wavefront matching optic, the two optical beams forming an incident plane at an incident angle relative to the transparent window;
• and
• a microscope objective configured to collect a fluorescent signal excited in the sample by the illumination field along a direction perpendicular to the incident plane, wherein:
• the incident angle is one of approximately 60° or approximately 300,
• an optical axis of the illumination objective intersects an optical axis of the microscope objective at the center of curvature of the wavefront matching optic, and
• the illumination field comprises a structured illumination field having a spatial frequency on the incident plane.

A method for forming an image of a sample, comprising:

• providing a spatially modulated imaging field;
• adjusting a frequency of the spatially modulated imaging field;
• directing, with a sample interface, the spatially modulated imaging field to a sample;
• receiving a plurality of fluorescence emission signals from the sample;
• and
• combining the plurality of fluorescence emission signals to reduce a sample scattering signal and to obtain an image of the sample.