SPAD Array Distance Measurement Merging Sensitive Units
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Solution Overview
Problem
Existing distance measurement devices face challenges in maintaining a high signal-to-noise ratio, especially under high luminous flux conditions, and suffer from excessive size, energy consumption, and reduced fill factor due to complex architectures and photon detection inefficiencies.
Innovation Solution
A measuring device with a sensitive area comprising a number of sensitive units, where each unit generates an electrical signal upon photon impact, and a processing unit that determines distance based on the time of impact, with a secondary processing unit selecting active units to enhance signal-to-noise ratio and adapt to changing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a one-to-one association between sensitive units and processing elements is implemented, then the signal-to-noise ratio is optimized, but the device size and complexity increase excessively
Solution Approach 1:
The patent merges multiple sensitive units under a single processing element by implementing a many-to-one association model. Multiple sensitive units share common readout circuits and processing elements, reducing the overall number of components while maintaining the ability to detect photon impacts across the entire sensitive area. This consolidation reduces device size and complexity while preserving measurement precision through coordinated processing of signals from multiple units.
2Measurement precision
If a one-to-one association between sensitive units and processing elements is implemented, then the signal-to-noise ratio is optimized, but the fill factor decreases considerably
Solution Approach 1:
The patent merges multiple sensitive units under a single processing element, allowing the sensitive area to occupy a larger portion of the receiving means surface. By reducing the number of processing elements required, more area can be dedicated to photon detection, thereby increasing the fill factor. The processing element can sequentially or simultaneously process signals from multiple sensitive units without requiring dedicated hardware for each unit.
3Measurement precision
If a one-to-one association between sensitive units and processing elements is implemented, then the signal-to-noise ratio is optimized, but energy consumption increases excessively
Solution Approach 1:
The patent merges multiple sensitive units under a single processing element, reducing the total number of active components that consume energy. By sharing readout circuits and processing resources across multiple sensitive units, the system achieves the same measurement precision with lower overall energy consumption. The processing element can efficiently handle signals from multiple units through multiplexing or sequential processing, eliminating the need for dedicated power supply circuits for each unit.
4Area of stationary object
If photons impact processing elements in a large number, then the sensitive area coverage is reduced, but the photons cannot be detected causing information loss
Solution Approach 1:
The patent merges multiple sensitive units under a single processing element, ensuring that photons impacting any of the sensitive units can be detected and processed. The processing element is designed to handle signals from multiple sensitive units simultaneously or sequentially, preventing information loss. The sensitive area coverage is maximized while maintaining high photon detection efficiency through the shared processing capability.
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 device maintains a high signal-to-noise ratio, achieves precise distance measurement, and reduces energy consumption while maintaining a high fill factor, even under varying external conditions and high luminous flux.
Implementation Method 1
Devices for measuring distances are known, which are based on the emission of light radiation directed towards a reference object and on the detection of said light radiation reflected by the reference object itself
Implementation Method 2
Each one of said sensitive units or pixels comprises, in fact, at least one SPAD... capable of detecting the impact of at least one photon independently for each one of said sensitive units
Implementation Method 3
The measuring devices belonging to the known art furthermore comprise a processing unit capable of determining the time interval that elapses between the emission of said light radiation by the emission means and the moment when said light radiation is detected by the receiving means. The value of said time interval, which is known as Time of Flight (ToF) in technical jargon... is directly proportional to the distance between the measuring device and the reference object
Data Source
AI summary
Measuring device (1) suited to measure the distance (d) of a reference object (O), configured so that it performs a plurality of measuring operations (Ai) in succession and comprising emission means (2) suited to emit a light radiation (R), receiving means (3) comprising a sensitive area (31) which is sensitive to the light radiation (R) and which is provided with a number M of sensitive units (4), each one of the sensitive units (4) being configured to generate an electrical signal (S), a first processing unit (5) comprising Ne processing elements (6), each one of said Ne processing elements (6) being configured to receive the electrical signal (S) for determining the time of impact (t) of a photon (F) on the sensitive units (4) and for calculating the value of said distance (d). The measuring device (1) comprises a second processing unit (7) configured to receive the electrical signals (S), processing the electrical signals (S) in such a way as to select a number Nu of sensitive units (4) impacted by the photons (F), associating each one of the Nu sensitive units (4) to one of the Ne processing elements (6), in such a way that, at the moment of the successive measuring operation (Ai+1), the distance (d) is determined by each one of the Nu sensitive units (4) selected.