Single-Photon 3D Imaging With Pulsed Pattern Projection
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Solution Overview
Problem
Existing depth imaging systems face challenges in achieving high-speed scanning and sufficient illumination in ambient light conditions, particularly in industrial applications like conveyor systems, due to limitations in sensor framerate and optical power requirements.
Innovation Solution
A method and system that project a light pattern onto the field of view for less than 10 microseconds, using a camera sensor with single-photon detectors to synchronize imaging, separate ambient noise, and calculate depth profiles through triangulation, while minimizing optical power and enhancing depth resolution through spatial dithering and coincidence imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a high-speed imaging system is used to monitor distortions of projected lines in conveyor systems, then depth profiling speed is improved, but the system framerate becomes limited and cannot keep up with fast scanning requirements
Solution Approach 1:
The patent implements periodic pulsed illumination at frequencies up to 100 kHz, synchronizing light projection with sensor exposure windows. This periodic action allows the system to accumulate depth information over multiple illumination cycles without requiring the sensor to capture complete frames at the same high rate, effectively decoupling scanning speed from imaging framerate limitations.
Solution Approach 2:
The patent segments the imaging process into individual line-based exposure events rather than capturing complete frames. Each sensor line captures depth information from a single illuminated line segment, allowing independent processing and accumulation of depth data from multiple segments to reconstruct complete 3D scenes at high speeds.
2Speed
If the laser line power is modulated or pulsed to project multiple lines simultaneously, then sensing speed is improved, but illumination power requirements increase for ambient light conditions
Solution Approach 1:
The system uses periodic pulsed illumination with duty cycles optimized for ambient light rejection. By illuminating only during specific time windows and synchronizing sensor exposure accordingly, the system achieves high sensing speed while minimizing total energy consumption compared to continuous illumination approaches.
Solution Approach 2:
The system performs preliminary temporal gating by defining narrow exposure windows before actual depth measurement. This preliminary timing setup allows the sensor to ignore ambient light during non-illumination periods, reducing the required illumination power for achieving sufficient signal-to-noise ratio in bright environments.
3Device complexity
If the sensor system imposes framerate limitations, then device complexity is reduced, but sensing delay increases and performance is degraded
Solution Approach 1:
The patent implements periodic high-frequency illumination pulsing that operates independently of the sensor's native framerate. This allows the system to collect depth information at much higher rates than traditional frame-based systems, reducing sensing delay without requiring complex high-speed sensor architectures.
Solution Approach 2:
The system transitions from two-dimensional frame-based imaging to one-dimensional line-based depth scanning. By abandoning the requirement to capture complete 2D frames simultaneously and instead accumulating depth information from sequential line scans, the system achieves higher effective sampling rates with simpler sensor hardware.
4Illumination intensity
If ambient light conditions are strong, then illumination power requirements increase, but system reliability decreases without sufficient signal-to-noise ratio
Solution Approach 1:
The system uses periodic pulsed illumination synchronized with sensor exposure windows to create temporal separation between active illumination and ambient light. This timing synchronization allows the sensor to capture only photons from the pulsed laser during narrow exposure windows, effectively rejecting continuous ambient light and maintaining high signal-to-noise ratio without increasing illumination power.
Solution Approach 2:
The patent converts the harmful effect of ambient light into a beneficial filtering mechanism by using its temporal characteristics. By illuminating in short pulses and exposing the sensor only during these pulses, the system exploits the temporal distinction between pulsed laser light and continuous ambient light, turning ambient light from a noise source into a reference for temporal filtering.
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
Enables high-speed, low-power depth imaging with improved accuracy and immunity to ambient light, allowing for efficient depth profiling in various environments and reducing latency and bandwidth requirements.
Implementation Method 1
each comprising a photodetector, said pixels being in a false status when no light is detected by the corresponding photodetector, and in a true status when light is detected
Implementation Method 2
separating the projected pattern from an ambient light noise on the binary matrix of pixels by considering only pixels in the true status having at least one neighbour pixel also in the true status
Data Source
AI summary
Depth imaging system implementing the method of any of the previous claims comprising: a. an imaging device (4) comprising a matrix of pixels (1) each pixel comprising a photodetector (9) capable of detecting single photons impinging thereon and optics able to make an image of the field of view on the matrix of pixel (1), said single photon detector having a binary logic status of true when a photon is detected and a logic status of false when no photon is detected in a timeframe; b. a projector (5) able to project a pattern in a time window of less than 10 μsec, preferably less than 1 μsec; c. a controller synchronising the projector (5) time window and the imaging device timeframe; d. a logic determining, in use, the presence, during the timeframe, of contiguous pixels (11) in the true state, and calculating the depth profile corresponding to said contiguous pixels (11).