SINGLE-SHOT FULL-FIELD REFLECTION PHASE MICROSCOPY

• US 20120307035A1
• Filed: 01/25/2012
• Published: 12/06/2012
• Est. Priority Date: 01/25/2011
• Status: Active Grant

• Current Assignee: Hamamatsu Photonics KK, Massachusetts Institute of Technology
• Original Assignee: Hamamatsu Photonics KK
• Inventors: Yaqoob, Zahid, Yamauchi, Toyohiko, Feld, David, Hearn, Alison, Feld, Jonathan, Choi, Wonshik, Feld, Michael
• Granted Patent: US 10,451,402 B2
• Time in Patent Office: Days
• US Class Current: 348/79
• CPC Class Codes: G01B 9/02032 generating a spatial carrier frequency, e.g. by creating lateral or angular offset between reference and object beam shearing interferometers G01B9/02098
• CPC Class Codes: G01B 9/02047 using digital holographic imaging, e.g. lensless phase imaging without hologram in the reference path
• CPC Class Codes: G01B 9/02064 by particular adjustment of coherence gate, i.e. adjusting position of zero path difference in low coherence interferometry
• CPC Class Codes: G01B 9/0207 Error reduction by correction of the measurement signal based on independently determined error sources, e.g. using a reference interferometer
• CPC Class Codes: G01B 9/02084 Processing in the Fourier or frequency domain when not imaged in the frequency domain
• CPC Class Codes: G01B 9/02091 Tomographic interferometers, e.g. based on optical coherence
• CPC Class Codes: G01B 9/04 Measuring microscopes
• CPC Class Codes: G01N 21/45 using interferometric methods; using Schlieren methods
• CPC Class Codes: G02B 27/1086 operating by diffraction only
• CPC Class Codes: G02B 27/50 Optics for phase object visualisation
• CPC Class Codes: G03H 1/0443 Digital holography, i.e. recording holograms with digital recording means holobject computation G03H1/0866
• CPC Class Codes: G03H 2001/005 in microscopy, e.g. digital holographic microscope [DHM]
• CPC Class Codes: G03H 2001/0456 Spatial heterodyne, i.e. filtering a Fourier transform of the off-axis record
• CPC Class Codes: G03H 2001/0467 Gated recording using pulsed or low coherence light source, e.g. light in flight, first arriving light
• CPC Class Codes: G03H 2222/24 Low coherence light normally not allowing valuable record or reconstruction G03H1/06 takes precedence

Abstract

The present invention relates to a full-field reflection phase microscope. In a preferred embodiment, the invention can combine low-coherence interferometry and off-axis digital holographic microscopy (DHM). The reflection-based DHM provides highly sensitive and a single-shot imaging of cellular dynamics while the use of low coherence source provides a depth-selective measurement. A preferred embodiment of the system uses a diffraction grating in the reference arm to generate an interference image of uniform contrast over the entire field-of-view albeit low-coherence light source. With improved path-length sensitivity, the present invention is suitable for full-field measurement of membrane dynamics in live cells with sub-nanometer-scale sensitivity.

Claims

1. A system for phase measurement comprising:

a light source;

a material to be measured that is positioned to receive light from the light source;

an optical system that separates a diffraction order of light from the light source; and

an imaging detector that detects the diffracted order of light from the optical system and light from the material to provide a phase image of the material.

2. The system of claim 1 wherein light from the light source is transmitted through the material.

3. The system of claim 1 wherein light from the light source is reflected off a surface of the material.

4. the system of claim 1 further comprising a translation stage to position a coherence gate relative to the material.

5. The system of claim 1 wherein the low coherence light source comprises a laser.

6. The system of claim 1 wherein the light source comprises a broadband light source.

7. The system of claim 1 further comprising a reference light path is incident on a surface of the imaging detector at an angle relative to light incident on the surface from the material.

8. The system of claim 1 wherein the optical system comprises a spatial filter transmits a single order of light received from a grating.

9. The system of claim 1 wherein the optical system comprises a grating.

10. The system of claim 7 wherein the reference light path separates a diffraction order of the reflected light.

11. The system of claim 1 further comprising a spatial filter.

12. The system of claim 1 further comprising a data processor connected to the imaging detector.

13. The system of claim 12 further comprising a display that displays a quantitative phase image of the material.

14. The system of claim 12 further comprising a memory for storing image data.

15. The system of claim 1 further comprising an actuator providing relative movement between the light source and the material to be imaged.

16. The system of claim 1 further comprising a translation stage.

17. The system of claim 16 wherein the translation stage orients the material at an oblique angle relative to an incident light axis.

18. The system of claim 1 wherein light is reflected by the material.

19. The system of claim 7 wherein the reference light path includes a reflector.

20. The system of claim 1 wherein the material is positioned on a reflective surface.

21. The system of claim 1 wherein a beamsplitter separates light onto a reference path and an imaging path that includes the material to be imaged.

22. The system of claim 1 further comprising a coherence gate positioned relative to the material.

23. The system of claim 22 wherein the coherence gate is positioned to provide a transmission image of the material.

24. The system of claim 22 wherein the coherence gate is positioned to provide a reflection image of the material.

25. A method for phase microscopy comprising:

delivering light from a low coherence light source onto a material to be measured that is positioned along a first light path optically coupled to the light source;

delivering light onto a reference that is optically coupled to the light source;

separating a diffraction order of light from the reference; and

detecting light with an imaging detector, the detected light including light from the material directed along a first axis and the separated diffraction order of light directed along a second axis that is oriented at an angle relative to the first axis to form an interference pattern.

26. The system of claim 25 further comprising transmitting light from the light source through the material.

27. The method of claim 25 further comprising reflecting light from the light source off a surface of the material.

28. The method of claim 25 further comprising using a translation stage to position a coherence gate relative to the material.

29. The method of claim 25 wherein the low coherence light source comprises a laser.

30. The method of claim 25 wherein the light source comprises a broadband light source.

31. The method of claim 25 wherein the reference light path is incident on a surface of the imaging detector at an angle relative to light incident on the surface from the sample.

32. The method of claim 25 further comprising using a spatial filter to transmit a single order of light received from the grating.

33. The method of claim 25 further comprising processing image data with a data processor that receives image data from the imaging detector.

34. The method of claim 25 further comprising displaying image data on a display.

35. The method of claim 25 further comprising storing image data in a memory.

36. The method of claim 25 further comprising Hilbert transforming image data to provide a phase image.

37. The method of claim 25 further comprising orienting the material at an angle relative to an incident light axis.

38. The method of claim 25 further comprising imaging a biological sample.

39. The method of claim 25 further comprising imaging a moving cellular structure.

40. A system for reflection phase microscopy comprising:

a low coherence light source;

a sample to be measured that is positioned along a first light path optically coupled to the light source;

a reference reflector optically coupled to the light source;

an optical system to provide a diffraction order of light; and

an imaging detector that detects light from the sample and the reference light path.

41. The system of claim 40 wherein light from the light source is transmitted through the sample.

42. The system of claim 40 wherein light from the light source is reflected off a surface of the sample.

43. the system of claim 40 further comprising a translation stage to position a coherence gate relative to the sample.

44. The system of claim 40 wherein the low coherence light source comprises a laser.

45. The system of claim 40 wherein the light source comprises a broadband light source.

46. The system of claim 40 wherein the reference light path is incident on a surface of the imaging detector at an angle relative to light incident on the surface from the sample.

47. The system of claim 40 wherein the optical system comprises a grating and a spatial filter.

48. The system of claim 47 wherein the spatial filter transmits a single diffraction order of light received from the grating.

49. The system of claim 40 wherein the system performs off axis interferometry.

50. The system of claim 40 wherein the optical system uses the first diffraction order of light to interfere with light reflected by the sample.

51. The system of claim 40 wherein the sample is positioned over a reflector that can tilt at an angle relative to incident light.

52. The system of claim 40 wherein light from the light source is transmitted through the sample, reflects from a sample support surface and through the sample for imaging.

53. The system of claim 40 further comprising a coherence gate positioned out of the sample to obtain a no-fringe image.

54. The system of claim 40 wherein the optical system selects a first diffraction order component from a Fourier image and that shifts the component in a Fourier plane.

55. The system of claim 54 wherein the system obtains an inverse Fourier transform of an image.

56. The system of claim 40 further comprising a data processor that phase unwraps the image.

57. The system of claim 40 wherein the image comprises a full field quantitative phase image.

58. The system of claim 40 further comprising a first mirror mounted on a translation stage and a second mirror coupled to an actuator such that noise can be removed from an image.

59. The system of claim 58 wherein common-mode phase noise is subtracted from the image.

60. The system of claim 40 wherein the system determine a power spectral density of the sample.