Structured illumination for imaging of stationary and non-stationary, fluorescent and non-fluorescent, objects
An object to be imaged is illuminated with a structured (e.g., sinusoidal) illumination at a plurality of phase shifts to allow lateral superresolution and axial sectioning in images. When an object is to be imaged in vitro or in another situation in which the phase shifts cannot be accurately determined a priori, the images are taken, and the phase shifts are estimated a posteriori from peaks in the Fourier transforms. The technique is extended to the imaging of fluorescent and non-fluorescent objects as well as stationary and non-stationary objects.
1. A method for imaging an object, the method comprising:
(a) applying a structured periodic illumination to the object a plurality of times with a plurality of phase shifts of the structured illumination caused by relative movement between the structured illumination and the object;
(b) taking a plurality of images of the object corresponding to the plurality of phase shifts;
(c) estimating the plurality of phase shifts by determining a phase of a peak of a Fourier transform of each of the images taken in step (b) by a processor; and
(d) reconstructing a 2-D image or 3-D image of the object using the plurality of images taken in step (b) and the plurality of phase shifts estimated in step (c).
2. The method of claim 1 , wherein the object is stationary during step (b).
3. The method of claim 2 , wherein the object is fluorescent.
4. The method of claim 3 , wherein step (a) is performed with coherent illumination.
5. The method of claim 3 , wherein step (a) is performed with non-coherent illumination.
6. The method of claim 2 , wherein the object is non-fluorescent.
7. The method of claim 6 , wherein step (a) is performed with coherent illumination.
8. The method of claim 6 , wherein step (a) is performed with non-coherent illumination.
9. The method of claim 1 , wherein the object is non-stationary during step (b).
10. The method of claim 9 , wherein the object is fluorescent.
11. The method of claim 10 , wherein step (a) is performed with coherent illumination.
12. The method of claim 10 , wherein step (a) is performed with non-coherent illumination.
13. The method of claim 9 , wherein the object is non-fluorescent.
14. The method of claim 13 , wherein step (a) is performed with coherent illumination.
15. The method of claim 13 , wherein step (a) is performed with non-coherent illumination.
16. The method of claim 9 , wherein the phase shifts estimated in step (c) are caused at least partially by movement of the object.
17. The method of claim 1 , wherein the object is fluorescent.
18. The method of claim 1 , wherein step (a) is performed with coherent illumination.
19. The method of claim 18 , wherein step (a) comprising changing an angle of illumination of the object to reduce speckle.
20. The method of claim 1 , wherein step (a) is performed with non-coherent illumination.
21. The method of claim 1 , wherein the object is non-fluorescent.
22. The method of claim 1 , wherein step (a) is performed with coherent illumination.
23. The method of claim 1 , wherein step (a) is performed with non-coherent illumination.
24. The method of claim 1 , wherein step (d) comprises forming a lateral superresolution image of the object.
25. The method of claim 1 , wherein step (d) comprises forming an axially sectioned image of the object.
26. The method of claim 25 , wherein step (d) further comprises forming a lateral superresolution image of the object.
27. The method of claim 1 , wherein step (a) comprises applying the structured periodic illumination at a plurality of angular orientations.
28. The method of claim 1 , wherein the phase shifts estimated in step (c) are caused at least partially by moving an optical element.
29. The method of claim 1 , wherein the phase shifts estimated in step (c) are caused at least partially by moving the object.
30. The method of claim 1 , wherein the phase shifts estimated in step (c) are used in phase shift calibrations.
31. A system for imaging an object, the system comprising:
optics for applying a structured periodic illumination to the object a plurality of times with a plurality of phase shifts of the structured illumination caused by relative movement between the structured illumination and the object;
an imaging device for taking a plurality of images of the object corresponding to the plurality of phase shifts; and
a processor, in communication with the imaging device, for estimating the plurality of phase shifts by determining a phase of a peak of a Fourier transform of each of the images and reconstructing a 2-D image or 3-D image of the object using the plurality of images and the plurality of phase shifts.
32. The system of claim 31 , wherein the optics comprise a source of coherent illumination.
33. The system of claim 32 , wherein the optics comprise an optical element for forming interference fringes on the object.
34. The system of claim 33 , wherein the optics comprise a grating.
35. The system of claim 31 , wherein the optics comprise a source of non-coherent illumination.
36. The system of claim 31 , wherein the processor forms a lateral superresolution image of the object.
37. The system of claim 31 , wherein the processor forms an axially sectioned image of the object.
38. The system of claim 37 , wherein the processor also forms a lateral superresolution image of the object.
39. The system of claim 31 , wherein the optics apply the structured periodic illumination at a plurality of angular orientations.
40. The system of claim 31 , wherein the optics comprise an optical element that is controllable to apply the plurality of phase shifts.
41. The system of claim 40 , wherein the optics further comprise a device for moving the optical element to apply the plurality of phase shifts.
42. The system of claim 41 , wherein the optical element comprises a grating.
43. The system of claim 31 , further comprising a device for moving the object to apply the plurality of phase shifts.
44. The system of claim 31 , wherein the estimated phase shifts are used in phase shift calibrations.
45. The method of claim 1 , wherein, in step (c), the Fourier transform is a spatial-frequency Fourier transform.
46. The system of claim 31 , wherein the processor is configured such that the Fourier transform is a spatial-frequency Fourier transform.