Phase Imaging Apparatus Using Spatial Light Modulator and Dark-Field System
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Solution Overview
Problem
Conventional phase imaging techniques face limitations in dynamic range due to shot noise, particularly when dealing with weak-phase objects, where the intensity of scattered light is overwhelmed by non-scattered light, restricting the acquisition of phase information.
Innovation Solution
The integration of a spatial light modulator and a dark-field optical system to cancel large phase components, allowing for high-sensitivity measurement of small phase shifts with strong illumination, and combining these to generate phase images with a wide dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional digital holography is used to measure phase distribution, then phase information can be acquired, but the dynamic range is limited due to shot noise overwhelming the scattered light component
Solution Approach 1:
The patent segments the phase measurement process into two distinct stages: a first measurement for weak-phase objects using dark-field digital holography to capture small phase shifts with high sensitivity, and a second measurement for strong-phase objects using a spatial light modulator to cancel large phase components. This segmentation allows each measurement to be optimized for its specific phase range, thereby extending the overall dynamic range while maintaining high phase detection sensitivity in both regimes.
2Measurement precision
If strong illumination is used to improve S/N ratio, then phase detection sensitivity increases, but large phase components cause saturation and limit dynamic range
Solution Approach 1:
The patent applies preliminary anti-action by using a spatial light modulator to pre-cancel large phase components before the measurement process. By introducing a modulation pattern that is the negative of the large phase component, the system prevents saturation from occurring in the first place, allowing strong illumination to be used without causing harmful saturation effects. This enables high phase detection sensitivity to be achieved while avoiding the saturation problem.
3Measurement precision
If dark-field imaging is used to weaken non-scattered light, then scattered light component is enhanced, but the method is not established for providing quantitative phase imaging
Solution Approach 1:
The patent merges dark-field imaging with digital holography to create a unified quantitative phase imaging system. By combining the dark-field optical system that enhances scattered light detection with the holographic interference measurement capability, the system achieves both the enhanced scattered light detection of dark-field imaging and the quantitative phase measurement capability of digital holography, thereby establishing a complete solution for quantitative phase imaging across a wide dynamic range.
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 extends the dynamic range and enhances phase detection sensitivity, enabling the detection of small phase changes and reducing noise, thereby improving the imaging capabilities for both weak and strong phase objects.
Implementation Method 1
a spatial light modulator provided on a plane conjugate to a sample plane and capable of spatially modulating illumination light to be irradiated to a sample or object light that has passed through or that has been reflected by the sample based on a modulation pattern
Implementation Method 2
the dark-field optical system removes the non-scattered light component included in first object light affected by the spatial light modulator so as to generate second object light
Implementation Method 3
The intensity distribution of the interference fringe generated by the object light SOBJ and the reference light SREF which is a plane wave is recorded as a hologram by means of an image sensor 4
Data Source
AI summary
A spatial modulator is provided on a plane conjugate to a sample plane on which a sample is to be placed. The spatial modulator spatially modulates illumination light irradiated to the sample 2 or object light that has passed through or that has been reflected by the sample. A dark-field optical system removes the non-scattered light component of the first object light affected by the spatial light modulator so as to generate second object light. An image sensor records a hologram based on the second object light. A calculation processing apparatus combines complex amplitude information based on the modulation pattern supplied to the spatial light modulator and complex amplitude information based on the hologram with respect to the second object light so as to acquire a phase distribution originating from the sample.