Monolithic SPAD Receiver Architecture for Digital Frame Averaging
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Solution Overview
Problem
Conventional LIDAR systems require analog circuitry for signal processing, which can be complex and inefficient, whereas the proposed solution is a monolithic, single-chip receiver that operates entirely in the digital domain, eliminating the need for analog frontend components and enabling all-digital signal processing for range and intensity calculations.
Innovation Solution
A monolithic LIDAR receiver system that incorporates SPAD arrays to generate digital or digital-like signals, which are processed using a data pipeline, memory, and digital logic gates to determine range, intensity, and other parameters, eliminating the need for analog circuitry and allowing for synchronous operation based on a system clock signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate imaging and non-imaging SPAD architectures are used, then functional versatility is improved, but device complexity and manufacturing overhead increase
Solution Approach 1:
The patent combines imaging and non-imaging SPAD functionalities into a single monolithic pixel array where each pixel contains both an imaging SPAD with timing circuitry and a non-imaging SPAD without timing circuitry. This merging eliminates the need for separate architectures while maintaining both functional capabilities, thereby reducing device complexity and manufacturing overhead while preserving functional versatility.
Solution Approach 2:
The monolithic pixel array is designed to perform multiple functions: imaging SPADs enable time-correlated single photon counting for depth measurement, while non-imaging SPADs provide additional sensitivity for detecting low-light signals. This multi-functional design allows a single device to handle both imaging and non-imaging tasks, improving adaptability without requiring separate specialized components.
2Measurement precision
If timing circuitry is included in all SPAD pixels, then measurement precision is improved, but manufacturing precision requirements and device complexity increase
Solution Approach 1:
The patent applies timing circuitry selectively only to imaging SPAD pixels where depth measurement precision is required, while non-imaging SPAD pixels omit this circuitry. This local differentiation ensures that measurement precision is maintained in imaging regions without unnecessarily increasing device complexity across the entire array, thereby optimizing the balance between precision and complexity.
3Reliability
If frame averaging is implemented, then signal-to-noise ratio is improved, but processing time and loss of time increase
Solution Approach 1:
The patent performs averaging of depth values from multiple frames before generating the final depth image, which improves signal-to-noise ratio by reducing random noise through statistical averaging. This preliminary processing step enhances image quality and reliability, though it does require additional processing time compared to single-frame output.
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 simplifies the LIDAR system architecture, enhances processing efficiency, and enables more robust and accurate digital signal processing for distance measurement and intensity analysis, suitable for applications in autonomous vehicles and other environments.
Implementation Method 1
Each SPAD may be configured to provide a respective photosignal when triggered in response to detecting light from an external environment
Implementation Method 2
The distance between the LIDAR system and a given object may be determined based on a time of flight of the corresponding light pulses
Data Source
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AI summary
The present disclosure relates to systems and methods that include a monolithic, single- chip receiver. An example system includes a plurality of macropixels, each made up of an array of single photon avalanche diodes (SPADs). The system also includes a plurality of pipelined adders communicatively coupled to a respective portion of the plurality of macropixels. The system additionally includes a controller configured to carry out operations. The operations include during a listening period, receiving, at each pipelined adder of the plurality of pipelined adders, respective photosignals from the respective portion of the plurality of macropixels. The operations also include causing each pipelined adder of the plurality of pipelined adders to provide an output that includes a series of frames that provide an average number of SPADs of the respective portion of the plurality of macropixels that were triggered during a given listening period.