SPAD Array Dynamic Mode Switching for Distance Measurement
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Solution Overview
Problem
Conventional distance measurement apparatuses using SPAD arrays do not dynamically adjust the number of SPADs per pixel or sampling frequency during operation, leading to suboptimal performance in environments with external disturbance light and varying distances.
Innovation Solution
A distance measurement apparatus with a control section that adjusts the number of SPADs per pixel and sampling frequency in real-time based on external disturbance light and calculated distance, allowing for adaptive distance measurement conditions during the formation of a captured image frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of SPADs per pixel is increased to reduce noise effects, then distance measurement accuracy is improved, but spatial resolution deteriorates
Solution Approach 1:
The patent implements dynamic switching between multiple measurement modes, each with different numbers of SPADs per pixel. The system can transition between high-resolution mode (fewer SPADs per pixel) and high-accuracy mode (more SPADs per pixel) based on real-time measurement requirements, resolving the static trade-off between resolution and accuracy
Solution Approach 2:
The system changes the operational parameter of SPADs per pixel dynamically. By adjusting this parameter based on measurement conditions (such as distance, ambient light levels), the system optimizes the balance between resolution and accuracy for each specific measurement scenario
2Measurement precision
If the sampling frequency is increased to improve distance measurement accuracy, then measurement precision is improved, but measurement time increases
Solution Approach 1:
The system dynamically adjusts sampling frequency based on measurement conditions. For close-range measurements where high accuracy is critical, higher sampling frequencies are used. For far-range or less critical measurements, lower sampling frequencies reduce measurement time while maintaining adequate accuracy
Solution Approach 2:
The sampling frequency parameter is changed adaptively according to measurement distance and required accuracy. This allows the system to optimize the trade-off between measurement precision and measurement time for different operational scenarios
3Reliability
If the number of SPADs per pixel is increased to reduce effects of external disturbance light, then measurement reliability is improved, but device complexity increases
Solution Approach 1:
Rather than permanently increasing SPADs per pixel which would increase device complexity, the system dynamically configures the number of active SPADs per pixel during operation. This allows high reliability to be achieved temporarily when needed without permanently increasing the physical complexity of the pixel structure
Solution Approach 2:
The pixel structure is designed to be multi-functional, capable of operating in different modes (different numbers of SPADs per pixel) to serve different measurement requirements. This universal design avoids the need for separate hardware configurations for different reliability requirements
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 adaptive approach enhances distance measurement accuracy by optimizing the number of SPADs and sampling frequency, reducing noise from external light and ensuring accurate distance calculations across varying distances.
Implementation Method 1
A distance measurement apparatus (also occasionally referred to as a distance measurement sensor) that measures a distance to an object (target) on the basis of ToF (Time of Flight) is known.
Implementation Method 2
detects photons by receiving reflected light from the object with light-receiving elements referred to as SPADs (Single Photo Avalanche Diodes)
Implementation Method 3
converts carriers that arise therefrom into an electric signal by using avalanche multiplication
Data Source
AI summary
A distance measurement apparatus includes a light-emitting section adapted to emit light to a target area, a light-receiving section including a plurality of light-receiving elements that receives observation light in the target area to output an electric signal, a distance measurement process section adapted to perform, according to predetermined distance measurement conditions and in a captured image frame formed by the plurality of light-receiving elements, a distance measurement process for calculating a distance to an object on the basis of an electric signal commensurate with reflected light from the object to which the light emitted from the light-emitting section has been applied, the reflected light being included in the observation light received by some light-receiving element groups of the plurality of light-receiving elements included in a pixel, and a control section adapted to control the predetermined distance measurement conditions. The control section changes the predetermined distance measurement conditions while the current captured image frame is formed. This makes it possible to change the number of SPADs included in the pixel or the number of sampling frequency while the captured image frame is formed.