Multilayer Bandpass Filters for Fog Penetration via Water Absorption Bands
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Solution Overview
Problem
Photonic detectors have a limited dynamic range, making it difficult to detect variations in light levels in obscured environments like fog, as they are blinded by scattered light in the spectral regions outside the absorption bands of water, which are typically avoided in optical imaging systems.
Innovation Solution
The use of multilayer bandpass filters that preferentially pass wavelengths corresponding to the absorption bands of water, reducing scattered light and shifting the dynamic range of detectors to include variations in light levels, thereby enhancing contrast between objects and background in foggy conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical systems avoid water absorption bands to reduce scattered light, then detector sensitivity is improved, but visibility in foggy environments deteriorates because scattered light from spectral regions outside absorption bands blinds the detectors
Solution Approach 1:
The patent converts the harmful scattered light from fog into a beneficial effect by selecting spectral regions within water absorption bands. In these regions, water vapor absorbs scattered light from fog droplets, reducing the blinding effect on detectors. The absorption bands that were traditionally avoided become the optimal choice for fog penetration, as they selectively attenuate scattered light while allowing transmitted light from objects to pass through.
2Productivity
If photonic detectors are used to capture light in obscured environments, then image capture is enabled, but the limited dynamic range of detectors prevents detection of light level variations due to scattered light overwhelming the signal
Solution Approach 1:
The patent changes the spectral parameter of light detection by operating within water absorption bands rather than in traditional visible or near-infrared regions. This parameter change exploits the wavelength-dependent absorption characteristics of water vapor to selectively filter scattered light while preserving the transmitted light signal from objects, thereby extending the effective dynamic range of detectors in foggy conditions.
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 visibility in foggy environments by reducing scattered light and increasing the contrast ratio of images, allowing detectors to capture more nuanced light levels, thereby enhancing the quality of images in obscured scenes.
Implementation Method 1
The embodiments disclosed herein take advantage of the fact that the H2O absorption band (e.g. fog) admittedly blocks some light, but also absorbs other portions of scattered light
Implementation Method 2
The use of multilayer bandpass filters that preferentially pass wavelengths corresponding to the absorption bands of water
Data Source
AI summary
A method and device for viewing objects situated in fog is disclosed. An optical system directs light from a scene onto a detector array through one or more optical waveband limiting filters. The detector array transfers a succession of captured scene images to an electronic device for processing. These processed images are transferred to a display device. A method and device for demonstrating the inventive optical system is presented.