Illumination systems and devices for Fourier Ptychographic imaging

Apparatus for forming an image of a substantially translucent specimen, the apparatus comprising:

• an imaging system for illuminating and imaging the specimen based on light filtered by an optical element, the imaging system including:
• a detector configured to acquire a plurality of relatively lower resolution intensity images of the specimen based on light filtered by the optical element, wherein the content of the of the relatively lower-resolution intensity images of the specimen corresponds to partially overlapping regions in a two-dimensional (2D) spatial frequency Fourier reconstruction space that are arranged with a substantially regular pattern in a polar coordinate system in which the location of each spatial frequency in the pattern is defined by a radial coordinate that depends on a modulus of the spatial frequency, and an angular coordinate that depends on an angle of the spatial frequency;
• a variable illuminator operable to control the spatial frequency associated with the relatively lower-resolution intensity images according to angles of illumination between individual light sources of the variable illuminator and the specimen such that the modulus of a spatial frequency associated with one of the partially overlapping regions is substantially zero;
• and
• a processor for computationally reconstructing a relatively higher-resolution image of the specimen by iteratively updating overlapping regions of the relatively high-resolution image in a Fourier reconstruction space with the lower-resolution intensity images,
• wherein positions of illumination that correspond to the light sources are arranged in a plane perpendicular to the optical axis and are spaced evenly on concentric circles such that the number of angular locations selected around each circle increases monotonically with the radius of the circle.

A non-transitory tangible computer readable storage medium having a program recorded thereon, the program being executable by a computer apparatus to form an image of a substantially translucent specimen, the program comprising:

• code for controlling an illuminator to variably illuminate the specimen from a plurality of angles of illumination such that:
• (a) when each angle at a given point on the specimen is mapped to a point on a plane perpendicular to an optical axis, the points on the plane have an increasing density towards an axial position on the plane, and one of the points on the plane is substantially coincident with the axial position on the plane;
• or
• (b) the illumination angles are arranged with a substantially regular pattern in a polar coordinate system defined by a radial coordinate that depends on the magnitude of the distance from an optical axis and an angular coordinate corresponding to the orientation of the angle relative to the optical axis, wherein one of the illumination angles is at or near zero;
• code for controlling a detector to acquire a plurality of variably illuminated, relatively lower-resolution intensity images of the specimen based on light emitted from the illuminator according to variable illumination and filtered by an optical element;
• and
• code for computationally reconstructing a relatively higher-resolution image of the specimen by iteratively updating overlapping regions of the relatively higher-resolution image in Fourier space with the variably-illuminated, lower-resolution intensity images,
• wherein the illuminator is controlled such that the points on the plane are spaced evenly on concentric circles and such that a number of angular locations selected around each circle increases monotonically with the radius of the circle.