System and method for Hilbert phase imaging

• US 20060291712A1
• Filed: 03/24/2006
• Published: 12/28/2006
• Est. Priority Date: 03/25/2005
• Status: Active Grant

• Current Assignee: Hamamatsu Photonics KK, Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Ikeda, Takahiro, Popescu, Gabriel, Dasari, Ramachandra, Feld, Michael
• Granted Patent: US 8,772,693 B2
• Time in Patent Office: Days
• US Class Current: 382/134
• CPC Class Codes: G01N 15/10 Investigating individual particles
• CPC Class Codes: G01N 15/1433 using image recognition
• CPC Class Codes: G01N 15/1475 using image analysis for extracting features of the particle
• CPC Class Codes: G01N 2015/0073 Red blood cells
• CPC Class Codes: G01N 2015/008 White cells
• CPC Class Codes: G01N 2015/012 Red blood cells
• CPC Class Codes: G01N 2015/016 White blood cells
• CPC Class Codes: G01N 2015/145 by pattern of light, e.g. fringe pattern
• CPC Class Codes: G01N 2015/1454 using phase shift or interference, e.g. for improving contrast
• CPC Class Codes: G01N 2015/1497 Particle shape
• CPC Class Codes: G01N 21/453 Holographic interferometry for dimensional measurements G01B9/021 - G01B9/029
• CPC Class Codes: G01N 33/49 Blood chemical methods for determining blood cell populations G01N33/5094; chemical analysis of blood groups or blood types G01N33/80
• CPC Class Codes: G06V 20/693 Acquisition
• CPC Class Codes: H01L 27/14601 Structural or functional details thereof

Abstract

Hilbert phase microscopy (HPM) as an optical technique for measuring high transverse resolution quantitative phase images associated with optically transparent objects. Due to its single-shot nature, HPM is suitable for investigating rapid phenomena that take place in transparent structures such as biological cells. A preferred embodiment is used for measuring biological systems including measurements on red blood cells, while its ability to quantify dynamic processes on the millisecond scale, for example, can be illustrated with measurements on evaporating micron-size water droplets.

Claims

1. A method of imaging an object comprising:

providing a light source, a first optical path including an object to be imaged, a second optical path and an imaging device;

positioning the imaging device relative to the first optical path and the second optical path;

orienting the first optical path relative to the second optical path to form a fringe structure;

obtaining an image of the fringe structure; and

processing the image with a Hilbert transform to obtain image data.

2. The method of claim 1 further comprising orienting the fringe structure at an angle of 45°

with respect to orthogonal axes of the imaging device.

3. The method of claim 1 further comprising imaging a biological material.

4. The method of claim 1 further comprising imaging tissue.

5. The method of claim 1 further comprising providing a laser light source and a charge coupled device in a Fourier plane of the first optical path and the second optical path that detects an image.

6. The method of claim 1 further comprising obtaining a quantitative spatial phase image of the object.

7. The method of claim 6 further comprising obtaining the spatial phase image of the object by:

Fourier-transforming and high-pass filtering the measured spectral data to obtain a real sinusoidal signal component of a complex analytic signal;

obtaining the complex analytic signal associated with the sinusoidal signal by computing a 2D Fourier transform and suppressing the negative frequencies by employing an Hilbert transformation;

taking an inverse Fourier transform to obtain a complex 2D signal that provides phase information about the object; and

obtaining the quantitative spatial phase image by subtracting the linear phase.

8. The method of claim 1 further comprising removing a tissue or blood ample from a mammalian body for measurement.

9. The method of claim 1 further comprising determining a size of a sample from an image of the sample.

10. The method of claim 1 further comprising determining a volume of an object in a sample.

11. The method of claim 1 further comprising imaging a blood cell.

12. The method of claim 1 further comprising measuring a characteristic of a red or white blood cell.

13. The method of claim 1 further comprising measuring a noise component in an image and removing the noise component from the image.

14. The method of claim 1 further comprising obtaining an image with light reflected by an object.

15. The method of claim 14 further comprising attaching a reflective material to an object being measured.

16. The method of claim 15 further comprising attaching polystyrene particles to the object.

17. The method of claim 1 further comprising measuring hemolysis of a red blood cell.

18. The method of claim 1 further comprising using an optical modulator to modulate light from the light source.

19. The method of claim 1 further comprising measuring a crystalline material.

20. The method of claim 1 further comprising measuring an optical fiber.

21. A Hilbert phase imaging device comprising:

a light source, a first optical path, a second optical path and an imaging device positioned to receive light directed along the first optical path and the second optical path;

a modulating element that positions light from the light source to form a detectable fringe structure at the imaging device; and

a processor that receives image data from the imaging device and performs a Hilbert phase transformation of the image.

22. The device of claim 21 further comprising a fiber optic device that couples light from the light source to the first optical path and the second optical path.

23. The device of claim 21 wherein a beam splitter combines a modulated reference image and a sample image.

24. The device of claim 21 wherein the modulating device comprises a movable mirror.

25. The device of claim 21 wherein the modulating element comprises tilting the first light path relative to the second light path.

26. The device of claim 21 wherein a sample is mounted relative to an inverted microscope.

27. The device of claim 26 wherein the inverted microscope includes a sample holder, an objective lens, a beam splitter and a lens that couples light onto the imaging device positioned in a common Fourier plane.

28. The device of claim 22 further comprising a fiber optic splitter, a fiber coupler, a first collimator, a second collimator and a second objective lens.

29. The device of claim 21 wherein the processor includes a program that performs a Fourier transform on image data, applies a filter to the transformed image data and performs an inverse Fourier transform on the filtered image data.

30. The device of claim 21 further comprising a blood or tissue sample holder.

31. The device of claim 21 wherein light is reflected by a sample.

32. The device of claim 21 wherein light is transmitted through the sample.

33. The device of claim 21 wherein a reflective material is positioned on the sample.

34. The device of claim 21 wherein the imaging device comprises a CCD or CMOS imaging device leaving at least 480×

640 pixels and operating at least 10 frames per second.

35. An imaging device comprising:

a light source, a first optical path, a second optical path and an imaging device positioned relative to the first optical path and the second optical path;

the first optical path comprises an objective lens;

a sample positioned relative to the first optical path to provide an interference pattern;

a processor that provides Fourier transform and filter operations on image data to provide phase image data of the sample.

36. The device of claim 35 further comprising a rotating mirror.

37. The device of claim 35 wherein the imaging device collects at least 10 frames per second.

38. The device of claim 35 wherein the processor performs a Hilbert transform on the image data.

39. The device of claim 35 comprising an interferometer.

40. The device of claim 35 comprising a microscope.