Lensless Holographic Imaging with Refractive-Index Phase Retrieval
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Solution Overview
Problem
Holographic reconstruction algorithms introduce reconstruction noise due to the lack of phase information in lensless imaging, and existing methods to estimate phase, such as phase retrieval or moving the image sensor, complicate the device or impose density constraints on the sample.
Innovation Solution
A method for holographic reconstruction that modifies the optical path between the sample and the image sensor without moving the sensor, using materials with different refractive indices to iteratively refine the phase and intensity information, reducing reconstruction noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If holographic reconstruction algorithms are used to process the captured image, then the image can be reconstructed, but reconstruction noise (twin image) is introduced due to lack of phase information
Solution Approach 1:
The patent introduces an intermediary iterative algorithm that acts as a mediator between the captured intensity image and the desired complex image. This algorithm iteratively estimates phase information by alternating between the image domain and frequency domain, effectively recovering lost phase data without requiring additional physical measurements or moving parts.
Solution Approach 2:
The patent replaces mechanical approaches (such as moving the image sensor to capture multiple holograms at different positions) with a computational approach. The iterative algorithm performs phase retrieval computationally, substituting physical movement with mathematical iteration to recover phase information.
2Measurement precision
If phase retrieval algorithms using masks are applied to estimate phase, then phase information can be obtained, but the method is limited by sample density constraints requiring areas free of diffracting objects
Solution Approach 1:
The patent extracts phase information directly from the holographic interference pattern captured in the frequency domain, without requiring separation into reference and object regions. By working with the full complex hologram and applying iterative phase retrieval in the frequency domain, the method eliminates the need to extract or identify specific regions free of diffracting objects.
Solution Approach 2:
The patent creates a universal phase retrieval method that works for samples of any density. The iterative algorithm can handle both sparse and dense samples uniformly, making the technique universally applicable without requiring sample-specific adjustments or region identification.
3Measurement precision
If successive hologram acquisitions with image sensor movement are used, then phase information can be retrieved, but the device complexity increases due to precise movement requirements
Solution Approach 1:
The patent replaces the mechanical system of moving the image sensor with a computational iterative algorithm. Instead of physically displacing the sensor to capture multiple holograms, the method uses frequency domain processing and iterative phase retrieval to recover phase information from a single static capture, eliminating mechanical complexity.
Solution Approach 2:
The patent creates a computational copy of the phase retrieval process that occurs in the frequency domain. Rather than physically moving the sensor to obtain different views, the algorithm computationally generates the necessary information through iterative transformation between spatial and frequency domains.
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
Improves the spatial resolution of reconstructed images by effectively estimating the phase of the light wave, resulting in clearer sample representations even with closely spaced diffracting elements.
Implementation Method 1
diffraction waves resulting from the diffraction, by diffracting objects, of the sample of the light wave emitted by the light source
Implementation Method 2
The image sensor then captures an image of the light wave transmitted by the sample. This image is formed by interference patterns between the light wave emitted by the light source and transmitted by the sample, and diffraction waves resulting from the diffraction
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
Method for obtaining an image of a sample (10), comprising: - a) illumination of the sample using a light source (11); - b) acquisition, using an image sensor (16), of a first image (I1,P0) of the sample (10), formed in the detection plane (P0), the first image being representative of an exposure light wave (14) propagating from the sample, towards the image sensor, along a first optical path (L1); the method comprising, following b) - c) modification of an optical refractive index, between the image sensor and the sample; - d) following c), acquisition, of a second image (I2,P0) of the sample, representative of the exposure light wave (14) along a second optical path (L2); - e) Implementation of an iterative algorithm combining the first and second images to obtain an image of the sample. Figure 2A