Single-Pixel Camera Imaging Through Dynamic Fog
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Solution Overview
Problem
Imaging through fog presents challenges due to temporal variations in fog density, which can be confused with changes in target reflectivity, and the presence of light scattered by the fog, leading to image degradation and noise.
Innovation Solution
A method using a single-pixel camera with a combination of short pulses, a fast detector, and a high-pass filter to suppress the effects of fog density variations, allowing for successful image reconstruction using computational ghost imaging and compressive sensing techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional single-pixel imaging is used, then image reconstruction is achieved, but image quality degrades due to temporal variations in fog density and scattered light
Solution Approach 1:
The patent employs periodic pulsed illumination at a fixed repetition rate to probe the target through fog. By using periodic action rather than continuous illumination, the system can distinguish between signal variations caused by target reflectivity changes and those caused by fog density variations, as the pulsed nature creates a regular temporal pattern that can be filtered and analyzed to separate these effects.
Solution Approach 2:
The patent dynamically adjusts the illumination pulse timing and detector gating to track and compensate for fog density variations. By making the illumination and detection synchronized and adaptive, the system can maintain measurement precision despite the dynamic and changing nature of fog conditions during the imaging process.
2Loss of information
If longer acquisition times are used for image reconstruction, then more complete data is collected, but temporal fog variations cause signal confusion and degradation
Solution Approach 1:
The patent performs preliminary characterization of the fog medium by measuring its temporal transmission variations before and during the imaging process. This preliminary action allows the system to pre-compensate for fog effects and reconstruct images more quickly, as the fog variation model is already established and can be used to correct the imaging data without requiring extended acquisition times.
Solution Approach 2:
The patent implements feedback mechanisms where the detector continuously monitors the transmitted light through fog, and this information is fed back to adjust the reconstruction algorithm in real-time. This feedback loop allows the system to adapt to changing fog conditions during acquisition, maintaining image quality while reducing the total time needed for sufficient data collection.
3Reliability
If standard detectors are used, then system complexity is reduced, but sensitivity is insufficient for low light conditions and long distance imaging
Solution Approach 1:
The patent merges the illumination source and detection system into a synchronized pulsed operation, combining multiple functions into a coordinated system. By merging the timing control of illumination pulses with the gating of the sensitive detector, the system achieves high sensitivity for low-light conditions while managing complexity through integrated control rather than separate independent subsystems.
Solution Approach 2:
The patent changes the temporal parameters of illumination and detection, using short pulsed illumination followed by time-gated detection. This parameter change from continuous to pulsed operation allows standard detectors to achieve enhanced sensitivity by concentrating measurement time into brief windows when the signal is strongest, effectively improving detection capability without requiring inherently more complex detector hardware.
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
The method enables the reconstruction of images through fog with potential for shorter acquisition times, improving image fidelity and reducing noise by effectively mitigating the effects of temporal fog variations.
Implementation Method 1
the presence of light scattered by the fog, leading to image degradation and noise
Implementation Method 2
A pseudo-random pattern is imposed on each of a series of pulsed illumination beams directed at a target
Implementation Method 3
received by a detector that converts the light into electronic signals
Data Source
AI summary
A method for using a single-pixel camera to reconstruct images of objects obscured by fog or other dynamic scattering media. A pseudo-random phase or intensity pattern is imposed on illumination beams directed at a target. The beam with the imposed pattern forms a pseudo random pattern on the target. Information regarding the pattern imposed on each pulse is entered into a data processor/controller. The illumination beams with the pseudo random patterns are reflected off the target, collected by receiving optics and a bucket detector and converted into electronic signals fed into the data processor/controller. The data processor/controller applies a high-pass filter to remove slower signal variations produced by dynamic changes in the scattering medium over time. The filtered bucket values are then used together with their corresponding speckle patterns to generate the images using any appropriate reconstruction algorithm such as CGI or CSI.