SPAD Array Control Circuit for Photon Detection Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High detected event rates in SPAD arrays can lead to deteriorated measurement accuracy in applications such as ranging and 3D imaging due to factors like ambient light and target reflectance.
Innovation Solution
A circuit and method that selectively enables a subset of SPAD cells based on a measured count rate, using a control circuit to determine the number of cells to enable and employing SPAD cells with reduced sensitivity through partial shielding to manage high event rates and prevent pile-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all SPAD cells are enabled to detect photons, then the detection sensitivity is improved, but the measurement accuracy deteriorates due to event pile-up at high count rates
Solution Approach 1:
The patent implements dynamic control of SPAD cell activation by adjusting the enable signal waveform parameters (duty cycle, amplitude, timing) based on measured count rate. The control circuit modifies the activation signal characteristics in real-time to optimize the balance between detection sensitivity and measurement accuracy, preventing event pile-up while maintaining adequate photon detection capability
Solution Approach 2:
The patent changes operational parameters of the SPAD cells by modifying the enable signal properties (duration, amplitude, timing) and operating voltage levels. The control circuit adjusts these parameters dynamically based on count rate measurements to maintain optimal detection performance while avoiding saturation and event pile-up conditions that degrade measurement accuracy
2Productivity
If the SPAD array operates at high count rates, then the productivity is improved, but the measurement accuracy deteriorates due to event pile-up
Solution Approach 1:
The patent implements a feedback control mechanism where the control circuit continuously monitors the count rate from the SPAD array and uses this information to adjust the enable signal parameters. When high count rates are detected that would cause event pile-up, the control circuit modifies the activation signal to reduce the number of simultaneously active cells or adjust their timing, thereby maintaining measurement accuracy while preserving acceptable detection productivity
Solution Approach 2:
The system dynamically adapts its operation by continuously adjusting the enable signal characteristics based on real-time count rate measurements. This dynamic control allows the system to operate at high productivity levels when conditions permit while automatically reducing activation levels when event pile-up would compromise measurement accuracy, optimizing the trade-off between the two parameters
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
Improves measurement accuracy by preventing event pile-up and maintaining sensitivity within manageable limits, ensuring accurate photon arrival statistics and distance calculations.
Implementation Method 1
The detection by the SPAD array of the returning light pulse is based on event detection in the cells of the SPAD array. In particular, each cell will provide an output pulse when a photon is detected
Implementation Method 2
employing SPAD cells with reduced sensitivity through partial shielding to manage high event rates and prevent pile-up
Data Source
AI summary
A circuit may include an array of single photon avalanche diode (SPAD) cells, each SPAD cell configured to be selectively enabled by an activation signal. The circuit may include a control circuit configured to selectively enable a subset of the array of SPAD cells based on a measured count rate of the array of SPAD cells.