Digital Holography Phase Compensation for 3D and Vibration Imaging
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Solution Overview
Problem
Ladar systems face limitations in space and power consumption, and require multi-functionality for efficient target sensing, particularly in remote sensing applications where phase stability is crucial, yet current digital holography systems can only sense targets in a single range-Doppler bin and are prone to phase errors.
Innovation Solution
Incorporating wide-bandwidth detectors and data acquisition systems to sense and correct for phase errors by interfering TX monitor and local oscillator waveforms, enabling phase-based imaging and compensation for phase instabilities in digital holography systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If digital holography systems use a single reference beam for coherent detection, then the system achieves compact size and low power consumption, but the system is limited to sensing targets in a single range-Doppler bin and suffers from phase errors
Solution Approach 1:
The system segments the reference beam function by employing multiple local oscillators (LOs) with different frequency offsets, where each LO handles a specific range-Doppler bin. This segmentation allows the system to maintain the simplicity of coherent detection while extending functionality to multiple bins simultaneously, resolving the contradiction between device complexity and adaptability.
Solution Approach 2:
The patent implements multi-functionality by designing a system where multiple local oscillators can operate concurrently to sense targets across different range-Doppler bins. Each LO is tuned to a specific frequency offset, enabling the system to perform multiple sensing functions (different velocity measurements) with a single integrated apparatus, thus achieving versatility without proportionally increasing complexity.
2Speed
If digital holography systems operate at moderate to long standoff distances, then the system achieves remote sensing capability, but phase instability and phase errors increase
Solution Approach 1:
The system employs feedback mechanisms where the phase information from multiple local oscillators is processed to compensate for phase errors. By comparing the interference patterns from different LOs and using the known frequency offsets, the system can identify and correct phase instabilities that occur during long-range operation, thereby maintaining reliability at extended standoff distances.
Solution Approach 2:
Multiple local oscillators act as intermediaries that facilitate remote sensing while mitigating phase instability. Each LO provides a reference signal with a specific frequency offset that serves as an intermediary reference, allowing the system to measure phase differences more accurately over long distances by comparing against multiple stable references rather than a single vulnerable reference.
3Measurement precision
If digital holography systems use coherent detection with reference beam, then the system achieves high sensitivity and phase measurement capability, but the system occupies more space and consumes more power
Solution Approach 1:
The system applies partial action by using multiple local oscillators only when multi-bin sensing is required. Each LO operates at a reduced power level compared to a single high-power LO, and the system activates only the necessary LOs based on the sensing requirements. This approach maintains high measurement precision through coherent detection while managing power consumption by avoiding the need for a single excessively powerful reference beam.
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 compact, low-cost solutions for precise 3D and vibration imaging by correcting phase errors, enhancing multi-functionality and efficiency in ladar systems.
Implementation Method 1
the return signal from the target is combined with a local oscillator (LO) beam to produce a mixed beam
Implementation Method 2
coherent detection systems include a receiver that incorporates a reference beam of light, often called a local oscillator (LO) or master oscillator (MO), that is interfered with the received light to produce a signal downshifted to the radio frequency (RF) band where it's amplitude and phase can be measured
Data Source
AI summary
Systems and methods are provided for a digital holography system. The subject system uses wide-bandwidth data, monitor beams, and signal beams to form a digital interference, yielding a reference phase and angle that can be used to compensate DH phase errors. DH systems disclosed herein can provide an ability to sense and correct for phase errors and/or instabilities to perform DH vibrometry. Such a system provides a compact and low-cost solution to improve sensing in, for example, systems that rely on phase stability for precision 3D and/or vibration imaging.