Phase-shifting diffraction phase interferometry
View Patent ↗Snapshot phase-shifting diffraction modules and associated systems and methods are described that enable high spatial and temporal resolution phase imaging with high immunity to environmental factors such as vibrations and temperature changes. One example optical diffraction phase module includes a polarization grating to produce two circularly polarized light beams with opposite polarizations, a first lens to receive the two circularly polarized beams, and a spatial filter positioned at a focal plane of the first lens. The spatial filter includes two openings, one to spatially filter one of the two circularly polarized light beams, and another opening to allow another circularly polarized light beam to pass. The module also includes a second lens to focus the received light onto an image plane and to enable a phase measurement based a plurality of interferograms. The phase module can be incorporated into a microscope system that operates a reflection or a transmission mode.
1. An optical diffraction phase module, comprising:
a polarization grating positioned to receive a linearly polarized light beam and to produce two circularly polarized light beams with opposite polarizations;
a first lens positioned to receive the two circularly polarized light beams;
a spatial filter positioned at a focal plane of the first lens to receive focused light corresponding to the two circularly polarized light beams, the spatial filter comprising a first opening configured to spatially filter a first one of the two circularly polarized lightbeams, and a second opening configured to allow a second one of the two circularly polarized light beams to pass therethrough substantially unchanged; and
a second lens positioned to receive the two oppositely circularly polarized light beams after passing through the spatial filter and to focus the received light onto an image plane to enable a phase measurement based on a plurality of interferograms formed by a polarization sensitive device at the image plane based on the two oppositely circularly polarized light beams.
2. The optical diffraction phase module of claim 1 , wherein the first opening of the spatial filter is a pinhole opening.
3. The optical diffraction phase module of claim 1 , wherein the first one of the two circularly polarized light beams is a right circularly polarized light beam and the second one the two circularly polarized light beams is a left circularly polarized light beam.
4. The optical diffraction phase module of claim 1 , comprising the polarization sensitive device that is a polarization sensitive camera positioned at the image plane that includes:
a polarizer array having a plurality of polarizer elements, and
a detector array configured to produce electrical signals based on detected intensities of the plurality of interferograms.
5. The optical diffraction phase module of claim 1 , comprising a first and a second set of folding mirrors positioned between the first lens and the spatial filter to receive the first and the second one of the two circularly polarized light beams, respectively, and to laterally displace focal spots associated with the two circularly polarized light beams at the focal plane of the first lens.
6. The optical diffraction phase module of claim 5 , wherein each set of the folding mirrors includes two mirrors, and wherein a separation between the two mirrors in one or both of the first or the second set of folding mirrors is selected to produce a particular lateral displacement of the focal spots.
7. The optical diffraction phase module of claim 1 , wherein the polarization grating is a first polarization grating, and wherein the optical diffraction phase module includes a second polarization grating next to the first polarization grating to produce, in conjunction with the first polarization grating, the two circularly polarized light beams with opposite polarizations.
8. The optical diffraction phase module of claim 7 , wherein one or both of the first or the second polarization gratings is configured to be rotated to enable a lateral displacement of focal spots associated with the two circularly polarized light beams at the focal plane of the first lens.
9. The optical diffraction phase module of claim 1 , wherein the optical diffraction module is a part of a microscope system, and wherein an image plane of the microscope system coincides with the polarization grating's position.
10. The optical diffraction phase module of claim 9 , wherein the microscope system is configured to operate in a transmission mode and comprises:
a condenser lens positioned to receive incident light from a light source,
a polarizer to receive the incident light from the condenser lens and to produce a polarized incident light for illumination of an object,
an objective lens positioned to receive and direct at least a portion of the polarized incident light after transmission through the object in the direction of a tube lens, and
the tube lens positioned to direct the polarized light received thereon to the image plane of the microscope system, thus providing the linearly polarized light beam that is incident on the polarization grating.
11. The optical diffraction phase module of claim 9 , wherein the microscope system is configured to operate in a reflection mode and comprises:
a condenser lens positioned to receive incident light from a light source,
a polarizer to receive the incident light from the condenser lens and to produce a polarized light,
an objective lens positioned to receive the polarized light for illumination of an object, the objective lens also configured to receive at least a portion of reflected polarized light from the object and to direct the received reflected polarized light in a direction of a tube lens; and
the tube lens positioned to direct the polarized light received thereon to the image plane of the microscope system, thus providing the linearly polarized light beam that is incident on the polarization grating.
12. The optical diffraction phase module of claim 11 , wherein the microscope system further comprises a beam splitter positioned to receive and reflect the polarized light toward the objective lens, the beam splitter further configured to receive, and transmit therethrough, the reflected polarized light collected by the objective lens for reception by the tube lens.
13. The optical diffraction phase module of claim 9 , wherein the microscope system is configured to operate in both a transmission mode and a reflection mode, the microscope system comprising:
a first condenser lens positioned to receive a first incident light from a first light source,
a first polarizer to receive the first incident light from the first condenser lens and to produce a first polarized light for illumination of an object,
an objective lens positioned to receive at least a portion of the first polarized light after transmission through the object,
a second condenser lens positioned to receive a second incident light from a second light source,
a second polarizer to receive the second incident light from the second condenser lens and to produce a second polarized light,
a beam splitter configured to receive the second polarized light produced by the second polarizer, and to provide the second polarized light to the objective lens,
the objective lens further configured to receive at least a portion of the second polarized light after reflection from the object, and
a tube lens positioned to receive the transmitted first polarized light after transmission through the object, collection by the objective, and transmission through the beam splitter, the tube lens further configured to receive the reflected second polarized light after reflection from the object, collection by the objective lens and transmission through the beam splitter.
14. The optical diffraction phase module of claim 13 , wherein the first and second light sources have the same wavelength and transmission characteristics, the first and the second polarized lights have the same linear polarizations, and the microscope system is configured to selectively operate in one of the transmission mode or the reflection mode.
15. The optical diffraction phase module of claim 9 , wherein the microscope system comprises one or more laser light sources, or one or more light emitting diode (LED) light sources.
16. An optical diffraction phase module, comprising:
a grating positioned to receive an unpolarized light beam and to produce a plurality of light beams associated with two or more diffraction orders of the grating;
a first lens positioned to receive the plurality of light beams;
a spatial filter positioned at a focal plane of the first lens to receive focused light corresponding to the plurality of light beams, the spatial filter comprising a first opening configured to spatially filter a first one of the plurality of light beams, and a second opening configured to allow a second one of the plurality of light beams to pass therethrough substantially unchanged;
a first and a second linear polarizers positioned after the spatial filter, the first linear polarizer configured to produce a first linearly polarized light based on the first one of the plurality of light beams after passing through the first opening, the second linear polarizer configured to produce a second linearly polarized light based on the second one of the plurality of lightbeams after passing through the second opening the first and the second linearly polarized lights having orthogonal polarizations with respect to each other;
a quarter wave plate (QWP) positioned to receive the first and the second linearly polarized lights and to produce two oppositely circularly polarized light beams; and
a second lens positioned to receive the two oppositely circularly polarized light beams and to focus the received light onto an image plane to enable a phase measurement using a plurality of interferograms formed by a polarization sensitive camera at the image plane based on the two oppositely circularly polarized light beams.
17. The optical diffraction phase module of claim 16 , wherein a transmission axis of the first and the second polarizers is oriented at 0° and 90°, respectively, and an axis of the QWP is oriented at an angle of 45°.
18. The optical diffraction phase module of claim 16 , wherein the first one of the plurality of light beams corresponds to either a positive first or a negative first diffraction order, and the second one of the plurality of light beams corresponds to a zero diffraction order.
19. The optical diffraction phase module of claim 16 , wherein the optical diffraction phase module is part of a microscope system, wherein an image plane of the microscope system coincides with the grating's position.
20. The optical diffraction phase module of claim 16 , wherein the optical diffraction phase module is configured as a 4f system.