A method for digital holographic microtomography comprises (a) providing at least one wavefront controlling device for driving a sample to be rotated and/or an incident beam scanning the sample, (b) utilizing a digital holographic access unit for recording the transmitted or reflected wavefronts of the sample, (c) utilizing a digital holography reconstructing method for reconstructing the transmitted or reflected wavefronts of the sample, and (d) utilizing a tomographic reconstruction approach for reconstructing three dimensional image information of the sample.

A method for digital holographic microtomography comprises (a) providing at least one wavefront controlling device for driving a sample to be rotated and/or an incident beam scanning the sample, (b) utilizing a digital holographic access unit for recording the transmitted or reflected wavefronts of the sample, (c) utilizing a digital holography reconstructing method for reconstructing the transmitted or reflected wavefronts of the sample, and (d) utilizing a tomographic reconstruction approach for reconstructing three dimensional image information of the sample.

A high effective refractive index structure may include one or more high effective refractive index materials disposed on a substrate. The high effective refractive index structure configured to respond to a light received at the high effective refractive index structure by at least generating one or more sub-diffraction limit illumination patterns for illuminating a specimen while one or more frames are captured of the illuminated specimen. The one or more sub-diffraction limit illumination patterns may include one or more speckle patterns. The one or more high effective refractive index materials may exhibit an effective refractive index equal to or greater than 3. Examples of high effective refractive index materials include hyperbolic metamaterial (HMM) multilayers, nanowire based hyperbolic metamaterials, and organic hyperbolic materials (OHM).

Various methods, systems and apparatus are provided for imaging and sensing using interferometry. In one example, a system includes an interferometer; a light source that can provide light to the interferometer at multiple wavelengths (.sub.i); and optical path delay (OPD) modifying optics that can enhance contrast in an interferometer output associated with a sample. The light can be directed to the sample by optics of the interferometer. The interferometer output can be captured by a detector (e.g., a camera) at each of the multiple wavelengths (.sub.i). In another example, an apparatus includes an add-on unit containing OPD that can enhance contrast in an interferometer output associated with a sample illuminated by light at a defined wavelength (.sub.i). A detector can be attached to the add-on unit to record the interferometer output at the defined wavelength (.sub.i).

Various methods, systems and apparatus are provided for imaging and sensing using interferometry. In one example, a system includes an interferometer; a light source that can provide light to the interferometer at multiple wavelengths (.sub.i); and optical path delay (OPD) modifying optics that can enhance contrast in an interferometer output associated with a sample. The light can be directed to the sample by optics of the interferometer. The interferometer output can be captured by a detector (e.g., a camera) at each of the multiple wavelengths (.sub.i). In another example, an apparatus includes an add-on unit containing OPD that can enhance contrast in an interferometer output associated with a sample illuminated by light at a defined wavelength (.sub.i). A detector can be attached to the add-on unit to record the interferometer output at the defined wavelength (.sub.i).

Briefly, embodiments of methods and/or systems for tomographic imaging are disclosed. In an example embodiment, optical measurements may be obtained for at least a portion of an illuminated object at a plurality of focal positions between the illuminated object and an imaging lens and at a plurality of angular orientations. Rotated representations of the optical measurements may be projected onto a coordinate plane in which in-focus and out-of-focus rotated representations of the optical measurements may form a cross-sectional image of the illuminated portion of the object.

Briefly, embodiments of methods and/or systems for tomographic imaging are disclosed. In an example embodiment, optical measurements may be obtained for at least a portion of an illuminated object at a plurality of focal positions between the illuminated object and an imaging lens and at a plurality of angular orientations. Rotated representations of the optical measurements may be projected onto a coordinate plane in which in-focus and out-of-focus rotated representations of the optical measurements may form a cross-sectional image of the illuminated portion of the object.

In a dark-field metrology method using a small target, a characteristic of an image of the target, obtained using a single diffraction order, is determined by fitting a combination fit function to the measured image. The combination fit function includes terms selected to represent aspects of the physical sensor and the target. Some coefficients of the combination fit function are determined based on parameters of the measurement process and/or target. In an embodiment the combination fit function includes jinc functions representing the point spread function of a pupil stop in the imaging system.

In a dark-field metrology method using a small target, a characteristic of an image of the target, obtained using a single diffraction order, is determined by fitting a combination fit function to the measured image. The combination fit function includes terms selected to represent aspects of the physical sensor and the target. Some coefficients of the combination fit function are determined based on parameters of the measurement process and/or target. In an embodiment the combination fit function includes jinc functions representing the point spread function of a pupil stop in the imaging system.

A method for characterizing structures etched in a substrate, such as a wafer is disclosed. A bottom of the structure is embedded in the substrate, the substrate having a top side in which the structures are etched and a bottom side opposite to the top side. The method includes the following steps: illuminating the bottom of at least one structure with an illumination beam issued from a light source emitting light with a wavelength adapted to be transmitted through the substrate, acquiring, with an imaging device positioned on the bottom side of said substrate, at least one image of a bottom of the at least one structure through the substrate, and measuring at least one data, called lateral data, relating to a lateral dimension of the bottom of the at least one HAR structure from the at least one acquired image. A system implementing such a method is also disclosed.