Optical Sensor Impedance Converter for LIDAR Parasitic Capacitance
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Solution Overview
Problem
High parasitic capacitance in photodiode matrices limits the implementation of high-count photodiode arrays in LIDAR devices, leading to deteriorated performance and inability to meet stringent requirements for long detection ranges, high accuracy, and high frame rates.
Innovation Solution
Integration of a quadruple well linear Avalanche PhotoDiode (APD) semiconductor with an integrated impedance converter attached to each APD, allowing selective activation and deactivation of columns to mitigate parasitic capacitance and reduce noise, thereby enhancing the performance of LIDAR systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photodiode matrices are used in LIDAR devices, then detection capability is improved, but parasitic capacitance increases leading to deteriorated performance
Solution Approach 1:
The photodiode matrix is divided into multiple independently controllable columns, each column connected to a separate impedance converter. This segmentation allows selective activation of only the necessary columns for each measurement, reducing the total parasitic capacitance connected to the transimpedance amplifier while maintaining detection capability across the full array.
Solution Approach 2:
The patent implements dynamic control of column activation through impedance converters that can selectively connect or disconnect columns from the common node. This dynamic switching capability allows the system to adaptively manage parasitic capacitance by activating only the required number of columns for each measurement, rather than having all columns permanently connected.
2Measurement precision
If high-count photodiode arrays are implemented, then measurement precision is improved, but device complexity increases
Solution Approach 1:
Multiple photodiode columns share a common transimpedance amplifier through individual impedance converters. This merging approach allows high-count photodiode arrays to achieve improved measurement precision while managing device complexity by consolidating the amplification function into a single shared TIA rather than requiring separate TIAs for each photodiode.
Solution Approach 2:
Impedance converters serve as intermediary components between individual photodiode columns and the shared transimpedance amplifier. These intermediaries manage the complex connections by providing controlled impedance matching and selective switching, simplifying the overall circuit architecture while enabling high-count array implementation.
3Area of stationary object
If all photodiodes are continuously connected, then detection coverage is improved, but noise performance deteriorates
Solution Approach 1:
The detection area is segmented into multiple columns that can be independently activated. This segmentation allows the system to provide full detection coverage across all columns while reducing noise by activating only the specific columns needed for each measurement, rather than continuously connecting all photodiodes.
Solution Approach 2:
Columns are activated periodically and selectively based on measurement requirements rather than continuous activation. This periodic action pattern reduces noise by limiting the time each photodiode is connected to the amplifier, while still achieving comprehensive detection coverage through sequential activation of different column groups.
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
The solution significantly reduces parasitic capacitance, improving the noise performance and enabling the use of high-count photodiode matrices in LIDAR devices, meeting the demanding requirements for long detection ranges and high frame rates.
Implementation Method 1
a first photodiode configured to convert light energy into a first electrical signal
Implementation Method 2
quadruple well linear Avalanche PhotoDiode (APD) semiconductor
Data Source
AI summary
Systems and circuits directed to a time-of-flight measurement system are provided. More specifically, an illustrative optical sensor is disclosed to include a plurality of avalanche photodiodes, at least one of the plurality of avalanche photodiodes being in communication with amplifier common node through an impedance converter that is responsive to a control signal and selectively connects or disconnects the at least one avalanche photodiode from the common node based on the control signal. In an example, the impedance converter is also configured to preserve current generated from the at least one avalanche photodiode.