Vehicle Camera Exposure Timing for Flickering Light Detection
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Solution Overview
Problem
Autonomous vehicle cameras struggle to capture images of flickering illuminated objects, such as brake lights and LED signs, due to short exposure times, leading to low likelihood of imaging these objects within a few microseconds, which can result in incorrect identification and control issues.
Innovation Solution
Adjusting the exposure time of cameras to cover the period of both power grid and PWM lights, combined with the use of neutral density or darkening filters to increase the likelihood of capturing images of flickering objects, allowing for more reliable identification of traffic signals and brake lights.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the exposure time is set to a very short duration (microseconds) based on ambient lighting conditions, then the camera can avoid over-exposure and maintain proper brightness levels, but the likelihood of capturing flickering illuminated objects (such as brake lights and LED signs) within the brief exposure window becomes very low
Solution Approach 1:
The patent applies periodic action by synchronizing the camera's exposure timing with the known flicker frequency of illuminated objects (e.g., 60Hz power grid frequency). Instead of using random or purely brightness-based exposure timing, the system schedules exposures to occur during the expected illumination phases of flickering lights, thereby reliably capturing these transient light sources while maintaining proper exposure through controlled timing intervals.
2Reliability
If the exposure time is extended to capture flickering objects, then the likelihood of imaging illuminated objects increases, but the risk of over-exposure and loss of scene detail increases
Solution Approach 1:
The patent applies local quality by using region-specific exposure strategies. Different regions of the image frame receive different exposure treatments: regions containing flickering illuminated objects use extended or synchronized exposure times to ensure capture, while other regions maintain standard exposure parameters to avoid over-exposure. This allows the system to optimize for detection reliability in critical areas without compromising overall image quality.
Solution Approach 2:
The system dynamically adjusts exposure parameters based on real-time detection of flickering light patterns. When flickering objects are detected or anticipated, the exposure time and timing are dynamically modified to synchronize with the flicker cycle. This dynamic adaptation allows the camera to switch between standard and enhanced exposure modes as needed, maintaining proper exposure control while improving detection reliability for illuminated objects.
3Ease of operation
If standard exposure algorithms are used without considering flicker frequency, then the camera operation remains simple and processing is straightforward, but illuminated objects may be missed or incorrectly identified
Solution Approach 1:
The patent applies preliminary action by pre-synchronizing the camera's exposure timing with known flicker frequencies (such as 60Hz power grid frequency) before actual object detection begins. This preliminary synchronization ensures that when the camera captures images, the exposure windows are already aligned with the expected illumination phases of flickering lights. This pre-planned timing coordination improves object identification accuracy without requiring complex real-time adjustments, thus maintaining operational simplicity.
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 improves the likelihood of capturing images of flickering objects, making identification simpler and reducing incorrect identification, thereby enhancing the reliability of image data for autonomous vehicle control.
Implementation Method 1
the use of neutral density or darkening filters to increase the likelihood of capturing images of flickering objects
Data Source
Figure 1
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Figure 3A~3B
AI summary
The technology relates to camera systems for vehicles having an autonomous driving mode. An example system includes a first camera mounted on a vehicle 100 in order to capture images of the vehicle's environment. The first camera 300 has a first exposure time and being without an ND filter. The system also includes a second camera 350 mounted on the vehicle in order to capture images of the vehicle's environment and having an ND filter. The system also includes one or more processors configured to capture images using the first camera and the first exposure time, capture images using the second camera and the second exposure time, use the images captured using the second camera to identify illuminated objects, use the images captured using the first camera to identify the locations of objects, and use the identified illuminated objects and identified locations of objects to control the vehicle in an autonomous driving mode.