Off-Axis Holographic Multiplexing for Six Complex Wavefronts
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Solution Overview
Problem
Existing holographic techniques face challenges in optically multiplexing a large number of interferometric channels in a single camera exposure without experiencing cross-talk between beams and efficiently utilizing the detector's spatial bandwidth, with the previous maximum being four channels.
Innovation Solution
An off-axis interferometric system capable of spatially multiplexing at least six complex wavefronts using different fringe orientations, encoding each into a single multiplexed hologram without loss of magnification or resolution, utilizing a configuration with phase delay plates and beam splitters to prevent interference between beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If on-axis holography is used to record the complex wavefront, then the sample and reference beam intensities are mixed with the complex wavefront, but acquiring three or four phase-shifted holograms sequentially isolates the sample's complex wavefront; however, fast dynamic processes cannot be recorded
Solution Approach 1:
The patent segments the spatial frequency spectrum into distinct regions using off-axis interferometry. By introducing an angle between sample and reference beams, the cross-correlation terms containing the complex wavefront are spatially separated from the auto-correlation term in the frequency domain. This allows single-exposure acquisition of the complex wavefront without requiring multiple sequential phase-shifted holograms, thereby capturing fast dynamic processes while maintaining measurement precision.
Solution Approach 2:
The patent transitions from temporal multiplexing (acquiring multiple holograms sequentially in time) to spatial multiplexing (encoding multiple interferometric channels simultaneously in space). By utilizing the spatial frequency domain and introducing angular separation between beams, the system encodes multiple complex wavefronts in different spatial frequency regions within a single camera exposure, enabling both precise measurement and high-speed dynamic recording.
2Speed
If off-axis holography is used to capture the complex wavefront in a single camera exposure, then fast dynamic processes are recorded, but the spatial frequency separation occurs across a single axis limiting information compression
Solution Approach 1:
The patent extends the spatial frequency separation from a single axis to two dimensions by introducing multiple beam pairs with different angular orientations. Instead of separating frequencies along one axis only, the system creates a two-dimensional spatial frequency spectrum where multiple interferometric channels are distributed across different angular directions. This allows compression of more information along axes other than the primary separation axis, increasing the amount of complex wavefront data that can be encoded in a single exposure without loss of information.
Solution Approach 2:
The patent creates a multi-functional interferometric system where a single optical setup simultaneously performs multiple functions: it captures multiple complex wavefronts from different sample regions or at different wavelengths, encodes them in distinct spatial frequency regions, and enables post-processing separation. This universal approach allows the system to adapt to various imaging needs (extended field of view, multi-color imaging, multi-depth imaging) while maintaining high-speed single-exposure acquisition capability.
3Quantity of substance
If multiple interferometric channels are multiplexed in a single hologram, then more information is acquired with the same number of camera pixels, but cross-talk between beams occurs
Solution Approach 1:
The patent applies local quality by assigning each interferometric channel a distinct spatial frequency region characterized by specific angular orientations and frequency offsets. Each beam pair is engineered to occupy a unique locale in the spatial frequency spectrum, with its cross-correlation term separated from other channels. This localized allocation prevents cross-talk between channels while maximizing the use of available camera pixels, allowing reliable multiplexing of multiple interferometric channels in a single hologram.
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
Enables the acquisition of 50% more complex wavefront data in a single camera exposure, suitable for dynamic samples, with improved spatial bandwidth efficiency and simultaneous acquisition of six holographic channels, optimizing information acquisition.
Implementation Method 1
the first and second phase delay plates are configured and operable to induce (1) a phase delay between each of the at least six beams to encode each of the at least six beams with a different fringe orientation and preventing the at least six beams from interfering with each other
Implementation Method 2
a first beam splitter configured and operable for receiving at least six beams, defining a common optical path, and dividing the common optical path into a sample arm and a reference arm
Implementation Method 3
an off-axis interferometric system capable of spatially multiplexing at least six complex wavefronts using different fringe orientations, encoding each into a single multiplexed hologram
Data Source
Figure 1a
Figure 1b
Figure 2a~2c
AI summary
The present invention discloses a technique having an off-axis interferometric geometry that is capable of spatially multiplexing at least six complex wavefronts, while using the same number of camera pixels typically needed for a single off-axis hologram encoding a single complex wavefront. Each of the at least six parallel complex wavefronts is encoded into an off-axis hologram with a different fringe orientation, and all complex wavefronts can be fully reconstructed. This technique is especially useful for highly dynamic samples, as it allows the acquisition of at least six complex wavefronts simultaneously, optimizing the amount of information that can be acquired in a single camera exposure. The novel off-axis multiplexing holographic system of the present invention provides an off-axis holography modality that is more camera spatial bandwidth efficient than on-axis holography. Moreover, the off-axis interferometric system allows simple simultaneous acquisition of at least six holographic channels, making it attractive for imaging dynamics.