Headlamp-Camera Synchronization for PWM Dynamic Range Control
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Solution Overview
Problem
Existing camera systems for motor vehicles struggle to detect vehicle surroundings in low-light conditions due to dynamic range issues caused by pulse width modulation-controlled headlamps, leading to underexposed and saturated areas, and interference effects like rolling shutter effects.
Innovation Solution
A camera system with a matrix or array of sensor elements is used to read out individual elements sequentially, synchronized with the actuation of imaging elements in the headlamp to adjust the temporal overlap based on luminous flux, reducing the dynamic range and minimizing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the headlamp uses pulse width modulation to generate bright and dark areas (e.g., low-beam with light/dark cut-off line), then the light distribution is optimized for human observation, but the camera detects a very wide dynamic range leading to underexposed and saturated areas
Solution Approach 1:
The patent divides the image sensor into multiple regions corresponding to different solid angle ranges, with each region having customized synchronization parameters. This segmentation allows different parts of the sensor to capture light from different headlamp imaging elements with optimized temporal overlap, preventing both underexposure and saturation in different spatial zones simultaneously.
Solution Approach 2:
The patent applies different synchronization strategies to different regions of the image sensor based on their specific requirements. Each sensor element or group is synchronized with corresponding headlamp imaging elements using locally optimized temporal overlap parameters, allowing the system to handle varying luminous flux characteristics across different fields of view.
2Productivity
If the camera reads out all sensor elements simultaneously, then the entire scene is captured at once, but interference effects and rolling shutter effects occur with pulse width modulation headlamps
Solution Approach 1:
The patent implements periodic synchronization between headlamp imaging element actuation and camera sensor element readout. By coordinating the temporal cycles of headlamp illumination pulses with camera readout cycles, the system ensures that each sensor element reads out during the corresponding on-phase of its associated imaging element, eliminating rolling shutter effects while maintaining efficient periodic operation.
3Illumination intensity
If the camera increases exposure time to capture dark areas, then underexposed regions are improved, but bright areas become saturated and lose information
Solution Approach 1:
The patent segments the sensor and applies region-specific temporal overlap settings. Dark area regions use longer temporal overlap to maximize light capture, while bright area regions use shorter temporal overlap to prevent saturation. This spatial segmentation of exposure parameters allows simultaneous optimization of both dark and bright region capture without information loss.
4Use of energy by moving object
If the headlamp imaging elements are actuated with high luminous flux, then the illumination efficiency for the camera is improved, but the dynamic range of the detected image increases leading to loss of detail
Solution Approach 1:
The patent applies local quality by assigning different temporal overlap parameters to different sensor regions based on their illumination requirements. Regions receiving high luminous flux use shorter temporal overlap to control dynamic range, while regions with lower flux use longer overlap to maintain illumination efficiency. This localized parameter optimization maintains overall system efficiency while controlling image dynamic range.
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 approach reduces the dynamic range of the camera's image, prevents overexposure and underexposure, and enhances the efficiency of vehicle lighting for the camera, while maintaining consistent illumination across different solid angle ranges.
Implementation Method 1
an image sensor (not shown) featuring a plurality of sensor elements arranged in the shape of a matrix or an array to detect image information from different solid angle ranges
Data Source
AI summary
A device is provided including a headlamp including imaging elements for the targeted generation of pixels of a light distribution, and which is set up so that individual imaging elements are actuated separately via pulse width modulation to specify the luminous flux generated by the imaging element through the ratio of the on-phases and the off-phases of the pulse width modulation. A camera features an image sensor with a plurality of sensor elements read out consecutively to detect image information from different solid angle ranges illuminated by the headlamp. A control unit actuates the headlamp and the camera, and regulates temporal overlap between on-phases of the actuation of an imaging element and reading out of at least one sensor element of the camera which is hit by light generated by the imaging element, depending on the size of luminous flux generated by the imaging element.