Device and method for iterative phase recovery based on pixel super-resolved on-chip holography
A method for lens-free imaging of a sample or objects within the sample uses multi-height iterative phase retrieval and rotational field transformations to perform wide FOV imaging of pathology samples with clinically comparable image quality to a benchtop lens-based microscope. The solution of the transport-of-intensity (TIE) equation is used as an initial guess in the phase recovery process to speed the image recovery process. The holographically reconstructed image can be digitally focused at any depth within the object FOV (after image capture) without the need for any focus adjustment, and is also digitally corrected for artifacts arising from uncontrolled tilting and height variations between the sample and sensor planes. In an alternative embodiment, a synthetic aperture approach is used with multi-angle iterative phase retrieval to perform wide FOV imaging of pathology samples and increase the effective numerical aperture of the image.
1. A method for lens-free imaging of a sample or objects within the sample using a sensor comprising:
illuminating the sample containing one or more objects with one or more light sources at a plurality of different illumination angles, wherein at each different angle the one or more light sources, sensor, or sample is shifted in lateral in-plane increments;
obtaining a plurality of images of diffraction patterns of the one or more objects with the sensor, wherein the plurality of images comprise multiple shifted images at each different angle;
generating a plurality of high-resolution pixel super-resolved holograms from the plurality of images, wherein each high-resolution pixel super-resolved hologram corresponds to a different illumination angle;
recovering phase information of the high-resolution pixel super-resolved holograms comprising, for each angle:
a) generating an initial guess of a complex field representing the sample;
b) applying a digital forward-propagation of the resulting field to a sensor plane;
c) updating the amplitude of the field at the sensor plane using a square root of the diffraction patterns generated at each angle, wherein the field amplitude is updated by a weighted average of the forward-propagated amplitude of (b) and the amplitude of the generated pixel super-resolved hologram of the corresponding illumination angle;
d) back propagating the updated field to a sample plane;
e) updating a sub-region of a spatial frequency domain corresponding to each illumination angle using the back propagated field;
f) repeating steps (a) through (e) for each angle;
and
outputting a phase-recovered complex field at an object plane based on the recovered lost phase information for one or more angles.
2. The method of claim 1 , wherein the one or more light sources comprises a single wavelength.
3. The method of claim 1 , wherein the one or more light sources comprises multiple different wavelengths.
4. The method of claim 2 , further comprising pseudo-coloring a reconstructed image from the phase-recovered complex field.
5. The method of claim 1 , wherein the weighted average of the forward-propagated amplitude and the amplitude of the generated pixel super-resolved hologram of the corresponding illumination angle sum to 100%.
6. The method of claim 1 , wherein the sample comprises a tissue sample located on a slide.
7. The method of claim 1 , wherein the plurality of illumination angles comprises less than 10 different angles.
8. The method of claim 1 , wherein the lens-free imaging has a numerical aperture exceeding 1.0.
9. A system for carrying out the method of claim 1 , comprising one or more processors configured to execute instructions thereon for recovering an object image based on a high-resolution synthetic aperture hologram created by the differing illumination angles.
10. The method of claim 1 , wherein the sample comprises an unstained pathological tissue sample or a stained pathological tissue sample.
11. The method of claim 1 , wherein the sample comprises multi-cellular features, cells, a blood smear, a biological component or constituent, cellular organelle, microscopic or nanoscopic particles, or bacteria.
12. The method of claim 1 , wherein the one or more light sources comprise a moveable light source.
13. The method of claim 1 , wherein the one or more light sources comprise a least one moveable or stationary light source(s) coupled to one or more waveguide(s), optical fiber(s), or aperture(s) configured to illuminate the sample at different illumination angles.
14. The method of claim 1 , wherein the one or more light sources comprise a plurality of light sources configured to illuminate the sample at different illumination angles.
15. The method of claim 1 , wherein the one or more light sources comprise a plurality of light sources at different illumination wavelengths configured to illuminate the sample at different illumination angles.
16. The method of claim 1 , wherein updating a sub-region of the spatial frequency domain using the back propagated field in (e) comprises a weighted average of the back-propagated amplitude of the field from (d) and the amplitude of the generated pixel super-resolved hologram of the corresponding illumination angle.
17. The method of claim 1 , wherein operation (b) further comprises applying a phase modulation and operation (d) removes the phase modulation.