Spatial Phase Scanning Digital Holography for Wide-Area Microscopy
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Solution Overview
Problem
Existing techniques for wide-area quantitative phase microscopy often sacrifice either speed or resolution, with methods like parallel phase shifting being fast but sacrificing pixel resolution, and space-time digital holography lacking holographic character in the scan direction.
Innovation Solution
The implementation of spatial phase scanning digital holography, where a motorized micrometer scans an object specimen across a tilted reference phase field, allowing for continuous large-area scanning and phase shift acquisition in one sweep, reducing optomechanical complexity and enabling true two-dimensional wide-field holograms without the need for phase shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If parallel phase shifting method is used, then acquisition speed is improved, but pixel resolution deteriorates
Solution Approach 1:
The patent introduces a spatial scanning dimension to the phase-shifting process. Instead of using temporal phase shifting at fixed pixels, the object is physically scanned across the field of view while acquiring holograms at different spatial positions. This spatial dimension replaces the temporal dimension, allowing continuous acquisition without sacrificing pixel resolution.
Solution Approach 2:
The large area scan is divided into multiple smaller field-of-view regions that are acquired sequentially through object scanning. Each region is processed independently with full pixel resolution, and the segments are later stitched together to form the complete wide-area hologram, maintaining high resolution throughout.
2Speed
If space-time digital holography is used, then scanning speed is improved, but holographic character in scan direction is lost
Solution Approach 1:
Instead of scanning the detector or reference beam as in conventional space-time holography, the patent inverts the approach by scanning the object specimen itself across the field of view. This maintains the holographic interference pattern formation while enabling continuous scanning without losing holographic character.
Solution Approach 2:
The patent implements continuous scanning of the object through the interferometer without stopping at discrete positions. The object moves continuously while holograms are acquired at regular intervals, eliminating the stop-and-go motion of traditional phase-shifting methods and maintaining continuous holographic recording.
3Loss of information
If multiple exposures per field-of-view are used, then phase information is improved, but system stability deteriorates due to stop-and-go motion
Solution Approach 1:
The patent replaces discrete multiple exposures with continuous scanning and continuous acquisition. The object moves continuously through the field of view while the camera continuously records holographic information, eliminating the repeated stopping and starting that causes mechanical instability and phase drift.
Solution Approach 2:
The system pre-configures the reference beam with a tilted wavefront before scanning begins. This preliminary setup creates a spatially varying phase reference that is captured throughout the entire scan, eliminating the need for repeated phase-shifting operations at each position and reducing the number of stop-and-go cycles.
4Area of stationary object
If large area scanning is implemented, then coverage area is improved, but data set size increases
Solution Approach 1:
The large-area scan is segmented into multiple smaller field-of-view regions acquired at different object positions. Each region contains fewer pixels than a single large-area image would require, and the segments are processed and stored separately before being stitched together, managing data volume through division.
Solution Approach 2:
Instead of acquiring one extremely large-resolution image of the entire area, the system acquires multiple smaller holographic copies at different positions. These copies contain redundant information that can be processed independently and then combined, reducing the total data burden compared to a single massive image.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables high-resolution, continuous scanning of large areas with reduced complexity, suitable for applications like fast scans of blood smears, cell cultures, and microelectronic surface profiles, while processing blocks of phase-shifted interferograms without requiring fast Fourier transforms.
Implementation Method 1
spatial phase scanning digital holography...acquire a series of camera frames...scan the object specimen across a tilted reference phase field
Data Source
AI summary
Disclosed are various embodiments for wide-area quantitative phase microscopy using spatial phase scanning digital holography. A motorized micrometer is scanned across a field-of-view, and a camera captures a frame of the field-of-view. The frame of the field-of-view is phase shifted by a predetermined number of pixels. The phase-shifted frame is included in a plurality of phase-shifted frames, and a complex optical field is generated based at least in part on the plurality of phase-shifted frames. A segment of the complex optical field is extracted and appended to a plurality of segments of the complex optical field. A holographic image is generated based at least in part on the plurality of segments of the complex optical field.