Photon Counting Time-of-Flight System Variable Shift Subframes
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Solution Overview
Problem
Current photon counting Time-of-Flight (ToF) systems face challenges in accurately measuring distance due to the pile-up effect caused by detector dead time, which leads to distortion and loss of signal information.
Innovation Solution
The proposed solution involves a Time-of-Flight system with circuitry that generates illumination pulses and records reflected pulses in recording time slots with variable time shifts, optimizing the illumination pattern by decomposing it into shifted subframes to mitigate the pile-up effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photon counting ToF systems use traditional recording methods with fixed time slots, then the system structure remains simple, but the pile-up effect causes signal distortion and reduces measurement accuracy
Solution Approach 1:
The patent divides the recording period into multiple subframes, each with recording time slots that have variable time shifts relative to illumination pulses. This segmentation allows the system to capture photon arrivals more accurately by distributing them across different time slots, thereby reducing the pile-up effect and improving distance measurement accuracy without requiring fundamental changes to the detector structure.
2Measurement precision
If the pulse width of laser pulses is reduced to achieve higher resolution, then reflection discrimination improves, but the signal intensity decreases and requires more sensitive detection
Solution Approach 1:
The patent employs periodic illumination pulses with optimized timing characteristics and uses multiple subframes with different time shifts to accumulate photon counting data. This periodic action with varying time shifts allows the system to maintain high depth resolution from narrow pulses while recovering signal intensity through temporal distribution and statistical accumulation across multiple periods.
3Ease of operation
If recording time slots are aligned with illumination pulses, then the system operation is simple, but the pile-up effect distorts the recorded signal at high intensity
Solution Approach 1:
The patent introduces dynamic time shifting of recording time slots relative to illumination pulses across different subframes. Instead of a fixed alignment, the time shifts vary dynamically, allowing the system to adapt to different signal intensities and reduce pile-up effects while maintaining operational simplicity through automated timing control.
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 improves the accuracy of distance measurements by reducing the impact of pile-up, allowing for more precise reconstruction of the target pulse shape and maintaining signal-to-noise ratio even at high intensity signals.
Implementation Method 1
A Time-of-Flight (ToF) camera is a range imaging camera system that determines the distance of objects by measuring the time of flight of a light signal between the camera and the object
Implementation Method 2
A pixel array in the ToF camera collects the light reflected from the scene and measures phase-shift which provides information on the travelling time of the light
Data Source
AI summary
A Time-of-Flight system of the photon counting type comprising circuitry configured to generate illumination pulses and to record the reflected illumination pulses in recording time slots within a recoding period with variable time shifts (t0, t1, t2, t3) between the illumination pulses and the recording time slots.