Light Detector Split Beam Interferometry Shot Noise Reduction
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Solution Overview
Problem
Existing optical systems face challenges in detecting signals due to high noise and low contrast, particularly in thermal and reflective spectral bands, where the signal of interest is obscured by a large light pedestal, leading to shot noise that inhibits detection.
Innovation Solution
The method involves splitting light into two streams, modifying one spectrum relative to the other, and recombining them to create a beat pattern that enhances signal amplitude and frequency differentiation between the signal of interest and background, reducing the impact of shot noise through interferometric techniques using fiber optics and silicon photonic waveguides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional light detection is used in thermal and reflective spectral bands, then the system can detect optical signals, but the signal-to-noise ratio deteriorates due to shot noise from the large light pedestal
Solution Approach 1:
The incoming light is divided into two separate beams: a signal beam that carries the information of interest and a reference beam that preserves the original light characteristics. This segmentation allows independent processing of each beam, enabling the system to eliminate shot noise while preserving the signal
Solution Approach 2:
A photonic lattice intermediary is introduced to correlate the signal beam with the reference beam. This intermediary structure enables the system to identify and eliminate noise components while preserving the actual signal, effectively acting as a mediator between the two beams
2Illumination intensity
If display brightness adjustment is used to enhance contrast in thermal imagery, then display contrast improves, but the underlying noise level remains unchanged
Solution Approach 1:
The system performs noise elimination and signal enhancement at the detection stage before the signal reaches the display. By preprocessing the optical signal to remove shot noise and enhance contrast intrinsically, the system ensures that the displayed image has both high contrast and high signal-to-noise ratio, rather than merely adjusting display brightness
3Adaptability or versatility
If passive thermal imaging is used under poor thermal contrast conditions, then the system can operate without active illumination, but the signal-to-noise ratio deteriorates when thermal contrast is less than 0.1 degree Kelvin
Solution Approach 1:
The system changes the detection parameters by using photonic lattice correlation to detect subtle variations in thermal radiation patterns. This parameter change enables the system to distinguish actual thermal signals from noise even when the thermal contrast is extremely low (less than 0.1 degree Kelvin), maintaining both passive operation and high measurement precision
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 significantly improves the signal-to-noise ratio by increasing signal amplitude and reducing the effect of noise, enabling more effective detection of optical signals even under poor contrast conditions, with a two-order magnitude improvement in some cases.
Implementation Method 1
splitting light into two light streams, modifying one spectrum slightly, and recombining them to create a beat pattern
Implementation Method 2
Two photonic detectors convert the recombined light streams into electrical signals
Data Source
AI summary
Methods for design and production of highly sensitive active and passive light detecting devices and systems. Orders of magnitude improvement in optical signal detection is made possible in high noise or low contrast scenes. The current invention creates a small spectral difference between two parts of a split light stream. When recombined, the altered light streams partially correlate, and that generates fall amplitude signal oscillation at a frequency that depends on the constituent spectrum. The full amplitude signals and spectrum dependent oscillation make signal discrimination much better than intensity-only methods. The effect of read noise, amplifier noise, dark current noise, and thermal noise due to photo detector shunt resistance, become less important when compared to light detection using prior art methods.