Non-line-of-sight Imaging with Dynamic Gating and Relay Wall Characterization
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Solution Overview
Problem
Current non-line-of-sight imaging systems are limited to small, controlled environments due to difficulties in detecting faint optical signals from distant objects and require precise positioning of components, which restricts their range and usability in uncontrolled environments with unknown or arbitrarily positioned relay walls.
Innovation Solution
A non-line-of-sight imaging system that uses an optical position finder to dynamically adjust the pulse repetition rate and detector gating, allowing characterization of relay walls and accommodating irregularities, enabling operation in uncontrolled environments with remote and arbitrarily oriented relay walls, and allowing imaging around corners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the system uses high time accuracy light detectors to measure time-of-flight of individual photons, then imaging capability around corners is achieved, but detection range is limited to less than a meter due to difficulty in detecting faint optical signals from distant objects
Solution Approach 1:
The patent employs pulsed laser illumination with dynamic pulse repetition rate adjustment to periodically illuminate the scene and collect returning photons. By synchronizing the detector gating with the pulse repetition rate, the system accumulates photons over multiple cycles, enhancing the detectable signal from distant objects while maintaining precise time-of-flight measurements through phase-locked detection
Solution Approach 2:
The system dynamically adjusts the pulse repetition rate of the laser based on the detected signal strength and distance to the relay wall. This dynamic parameter adjustment optimizes the balance between photon accumulation for extended range and maintaining measurement precision, allowing the system to adapt to varying detection ranges while preserving time-of-flight measurement accuracy
2Measurement precision
If the system requires precise positioning of components on an optical bench, then measurement accuracy is maintained, but adaptability to uncontrolled environments with unknown or arbitrarily positioned relay walls is lost
Solution Approach 1:
The system performs self-characterization of the optical path by using the reflected light from the illuminating laser to automatically determine the position and orientation of the relay wall. The optical position finder uses the same laser light that illuminates the scene to characterize the relay wall geometry, eliminating the need for external positioning equipment or manual calibration in uncontrolled environments
Solution Approach 2:
The illuminating laser serves multiple functions: it illuminates the hidden scene for imaging, provides the reference light for optical position finding, and enables time-of-flight measurements. This multi-functionality allows the system to operate in uncontrolled environments by using the same light source for both scene illumination and relay wall characterization, removing the requirement for separate positioning equipment
3Device complexity
If the system uses fixed pulse repetition rate and detector gating, then system complexity is reduced, but detection range remains limited and signal-to-noise ratio decreases
Solution Approach 1:
The system implements feedback control where the detected signal strength and time-of-flight distribution inform dynamic adjustment of the pulse repetition rate and detector gating parameters. This feedback loop optimizes the detection range and signal-to-noise ratio by adapting the illumination and detection timing to the actual scene conditions, while the automated nature of this feedback minimizes the perceived complexity for the user
4Ease of operation
If the system is designed for controlled laboratory environments with short optical paths, then component positioning is simplified, but usability in field applications with distant relay walls is prevented
Solution Approach 1:
The system automatically characterizes the relay wall position and orientation using reflected laser light, eliminating the need for manual positioning or calibration in field conditions. The optical position finder uses the same illuminating laser to determine relay wall geometry, allowing the system to self-adapt to distant and arbitrarily positioned relay walls without requiring simplified component positioning procedures
Solution Approach 2:
The system dynamically changes operational parameters including pulse repetition rate, detector gating timing, and integration time based on the detected distance to the relay wall and signal strength. These parameter adjustments enable the system to maintain optimal performance across varying ranges from laboratory distances to field deployment distances, bridging the gap between controlled and uncontrolled environments
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 system significantly increases detection range, enables precise characterization of relay walls, and facilitates imaging in dynamic environments, allowing for meaningful use in the field with improved signal-to-noise ratio and acquisition speed.
Implementation Method 1
The photons are originally emitted from a laser near the light detector and bounce off of a 'relay' wall in a non-specular reflection to then illuminate the object to be imaged. Light reflected from the object to be imaged returns to the light detector after again reflecting off of the relay wall.
Implementation Method 2
Current non-line-of-sight systems employ light detectors with extremely high time accuracy to measure the time-of-flight of individual photons as they arrive from the image surface.
Data Source
AI summary
An improved non-line-of-sight camera provides for real-time evaluation of a relay wall with respect to illuminated points and sensing areas for higher accuracy and practical field use. Gated sensing allows improved recovery of faint photon signals and higher resolution. The system allows an operator to a find virtual camera from looking around multiple corners.