Stereo Camera Exposure Timing for Low-Light Obstacle Ranging
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Solution Overview
Problem
Existing ADAS systems face challenges in detecting obstacles quickly and accurately under low ambient illuminance conditions, as the detection cycle is prolonged, and the signal-to-noise ratio (SNR) is low, leading to reduced ranging accuracy and potential failure in obstacle detection.
Innovation Solution
An image capturing apparatus with multiple image capturing units that can read luminance values multiple times during a frame, utilizing a combination of image plane phase difference and stereo ranging, and adjusting exposure start timings to enhance detection in low illuminance conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If exposure time is shortened to increase frame rate and reduce detection cycle, then detection speed is improved, but signal-to-noise ratio decreases and ranging accuracy deteriorates
Solution Approach 1:
The system performs preliminary actions by capturing multiple luminance values at different time points within a single exposure period. The image capturing units read luminance values multiple times during one frame cycle, allowing the system to accumulate sufficient signal data even with shorter exposure times, thereby maintaining ranging accuracy while achieving higher frame rates
Solution Approach 2:
The system maintains continuous useful action by continuously capturing luminance values throughout the exposure period rather than taking a single measurement. By reading luminance values multiple times during the exposure and utilizing all captured data for ranging calculations, the system ensures continuous signal accumulation that preserves measurement precision while enabling faster frame rates
2Measurement precision
If multiple image capturing units are used for stereo ranging to improve long distance accuracy, then ranging accuracy at long distance is improved, but device complexity and cost increase
Solution Approach 1:
Each image capturing unit is designed to perform multiple functions: it can capture images for stereo ranging with other units to achieve long distance accuracy, and simultaneously perform image plane phase difference ranging independently for short distance objects. This multi-functionality allows a single camera to replace what would otherwise require multiple specialized cameras, reducing overall system complexity
Solution Approach 2:
The system merges two ranging methodologies (stereo ranging and image plane phase difference ranging) into a unified system where the same image capturing units serve both purposes. By combining these approaches and allowing flexible switching between them, the system achieves both long distance and short distance ranging capabilities without requiring separate dedicated camera systems for each function
3Loss of time
If image capturing units read luminance values multiple times during one frame to achieve high frame rate, then detection cycle is shortened, but processing complexity increases
Solution Approach 1:
The system segments the luminance value reading process into multiple discrete time points within a single exposure period. By dividing the capture process into multiple readings and associating each reading with specific time information, the system can process and utilize these segmented data points independently for ranging calculations, reducing the overall detection cycle while managing processing complexity through structured data organization
4Reliability
If exposure start timings of multiple image capturing units are shifted to improve detection in low illuminance, then detection reliability is improved, but synchronization complexity increases
Solution Approach 1:
The system implements dynamic exposure timing where the start timings of exposure for different image capturing units are shifted relative to each other based on illuminance conditions. This dynamic adjustment allows the system to optimize detection reliability in low light by ensuring at least one unit captures adequate signal, while the timing relationships are managed through coordinated control that handles synchronization complexity
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 system effectively reduces the detection cycle of obstacles by optimizing exposure timings, ensuring accurate and timely obstacle detection even in low light conditions, thereby enhancing the safety of ADAS systems.
Implementation Method 1
a single photon avalanche diode (SPAD) sensor camera using a SPAD sensor has been proposed... This SPAD sensor is a sensor using a photon counter
Implementation Method 2
a stereo camera has been proposed. This stereo camera can perform a triangulation by using a parallax of two cameras to measure a distance to the obstacle
Data Source
AI summary
In a case where it is determined that a ranging image in which an object is not to be detected exists and it is determined that a situation where an automobile currently travels is a situation where jumping-in or cutting-in is likely to occur, an exposure start timing of one of cameras constituting a stereo camera is shifted.