SPAD Array Phase Control Circuit for Time of Flight Precision
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Solution Overview
Problem
The precision of time of flight estimation in SPAD arrays is degraded due to the timing of the light pulse, which affects the accuracy of applications such as ranging and 3D imaging.
Innovation Solution
A circuit and method that generate a voltage signal for an optical pulse based on a phase control signal, using a phase control circuit to adjust the phase of the optical pulse to optimize its positioning within a detection period, thereby improving phase estimation accuracy and avoiding clipping, while also considering ambient count rates to dynamically adjust the target phase value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the light pulse timing is fixed, then the circuit operation is simple, but the phase estimation accuracy is degraded
Solution Approach 1:
The patent implements dynamic adjustment of the light pulse phase through a phase control circuit that modifies the phase control signal based on detected phase values. This allows the system to adapt the pulse timing dynamically rather than keeping it fixed, thereby improving phase estimation accuracy while managing complexity through automated control
Solution Approach 2:
The patent employs a feedback mechanism where the detected phase of the optical pulse is fed back to the phase control circuit. This feedback loop enables the system to automatically adjust the phase control signal to optimize pulse positioning, resolving the contradiction between fixed operation simplicity and accuracy requirements
2Adaptability or versatility
If the target phase value is adjusted dynamically based on ambient count rate, then the accuracy under varying light conditions is improved, but the control circuit complexity increases
Solution Approach 1:
The patent makes the target phase value dynamic by adjusting it according to the ambient count rate. The phase control circuit responds to changing ambient light conditions by modifying the target phase, enabling the system to adapt to varying operational environments
Solution Approach 2:
The system performs self-adjustment by using its own detection of ambient count rate to automatically modify the target phase value. This self-service mechanism reduces the need for external intervention or complex manual control while maintaining adaptability
3Measurement precision
If the phase control is optimized to avoid clipping, then the measurement precision is improved, but the computational requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-determining an appropriate target phase value that avoids clipping conditions. The phase control circuit uses this pre-calculated target phase to position the optical pulse optimally within the detection period, preventing clipping before it occurs
Solution Approach 2:
The patent changes the phase parameter of the optical pulse to optimize positioning and avoid clipping. By adjusting the phase control signal to achieve a target phase value, the system modifies the pulse timing parameter to prevent measurement errors while managing computational complexity
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 enhances the accuracy of phase estimation and increases the dynamic range of time of flight readings, ensuring high precision and reducing the risk of clipping, especially under varying ambient light conditions.
Implementation Method 1
The light pulse reflected back from an object in the image scene is detected by the SPAD array, and used to determine the time of flight of the light pulse
Data Source
AI summary
A circuit may include a first circuit configured to generate a voltage signal for generating an optical pulse, the voltage signal being generated based on a phase control signal, and an array of single photon avalanche diode (SPAD) cells configured to detect a phase of the optical pulse. The circuit may include a phase control circuit configured to generate the phase control signal based upon a target phase value and the detected phase of the optical pulse.