Virtual Sensor Array for Non-Line-of-Sight Imaging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current time-of-flight imaging technologies face challenges in imaging objects that are occluded or hidden from direct line-of-sight, such as around corners or through diffusers, as they struggle to accurately reconstruct images due to limitations in resolution and light scattering.
Innovation Solution
The implementation of a time-of-flight imaging system that utilizes virtual sensors on reflective walls or diffusive media surfaces, where light from the occluded object reflects or passes through, allowing phase and intensity measurements to be used by a computer to reconstruct the object's image through algorithms like beamforming, pseudoinverse, CoSaMP, or basis pursuit denoising, improving resolution by leveraging the properties of diffusely reflective surfaces and modulation frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If time-of-flight sensors are used to image occluded objects around corners or through diffusers, then the ability to detect hidden objects is improved, but the resolution deteriorates to meters between targets
Solution Approach 1:
The patent introduces a diffusely reflective surface (wall or diffuser) as an intermediary element that light must pass through or reflect from to reach the camera. This intermediary surface becomes a virtual sensor array where different points on the surface capture light from different directions, enabling resolution improvement from meters to centimeters while maintaining the ability to detect occluded objects.
2Ease of manufacture
If purely Lambertian walls are used for corner imaging, then the system is simpler to implement, but the resolution remains limited to meter-scale
Solution Approach 1:
The patent changes the optical parameter of the wall surface from purely Lambertian (diffuse) reflection to include a specular lobe component. This parameter change in the reflectance properties of the surface dramatically improves resolution from meter-scale to centimeter-scale, while the surface remains simple and ordinary rather than requiring complex optical components.
3Difficulty of detecting and measuring
If diffusive media are used to image through scattering materials, then the ability to see through diffusers is improved, but light scattering reduces image quality
Solution Approach 1:
The patent uses the diffusive media surface itself as an intermediary virtual sensor array. Points on the surface of the diffuser function as virtual sensors that capture light from different angles, allowing the system to reconstruct images of objects behind the diffuser with improved reliability and quality despite the scattering nature of the media.
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 enhances the resolution of imaging around corners and through diffusers, enabling real-time reconstruction of occluded objects with improved spatial accuracy, even when objects are partially shiny or behind scattering media, by effectively turning reflective surfaces into sensor arrays.
Implementation Method 1
Light from the target object reflects off a diffusely reflective surface (e.g., a wall) and travels to the time-of-flight ('ToF') camera. Points on the diffusely reflective surface function as a virtual sensors in the imaging system.
Implementation Method 2
The diffusive media scatters light. For example, in some cases, the diffusive media comprises (a) a solid diffuser, (b) a translucent liquid (such as an emulsion or other colloid) in a transparent or translucent container, or (c) a fog, vapor or other light-scattering aerosol or gas in a transparent or translucent container.
Implementation Method 3
A computer performs an algorithm that takes as input phase and intensity measurements at each pixel of the time-of-flight camera, and that reconstructs an image of the target object.
Data Source
AI summary
A time-of-flight camera images an object around a corner or through a diffuser. In the case of imaging around a corner, light from a hidden target object reflects off a diffuse surface and travels to the camera. Points on the diffuse surface function as a virtual sensors. In the case of imaging through a diffuser, light from the target object is transmitted through a diffusive media and travels to the camera. Points on a surface of the diffuse media that is visible to the camera function as virtual sensors. In both cases, a computer represents phase and intensity measurements taken by the camera as a system of linear equations and solves a linear inverse problem to (i) recover an image of the target object; or (ii) to compute a 3D position for each point in a set of points on an exterior surface of the target object.