ADAS Camera Lens Distortion Calibration via Fixed Radial Center
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Solution Overview
Problem
Existing camera-based Advanced Driver Assistance Systems (ADAS) face challenges in accurately modeling lens distortion, which can lead to inaccurate measurements and suboptimal performance due to varying centers of radial distortion, and require complex calibration processes, especially when focusing at infinity without a collimator lens.
Innovation Solution
A method for camera production where the center of radial distortion is set to a fixed location, allowing for stable calibration of lens distortion parameters, using a focus and calibration target positioned at a finite distance and adjusting the lens in five degrees of freedom to achieve optimal focus, eliminating the need for intermediary optics and reducing manufacturing tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the center of radial distortion is allowed to vary, then the lens can achieve optimal optical performance, but the calibration process becomes complex and measurements become inaccurate
Solution Approach 1:
The patent applies preliminary action by pre-setting the center of radial distortion to a fixed location (typically the image center) during lens design and manufacturing. This preliminary configuration eliminates the need for complex post-production calibration to determine the distortion center, as it is already known and fixed. The calibration process only needs to determine the radial distortion coefficients (K1, K2, etc.), significantly simplifying the overall calibration procedure while maintaining measurement accuracy.
2Ease of manufacture
If the center of radial distortion is fixed to a common point, then calibration becomes simpler and more stable, but may reduce adaptability to different lens designs
Solution Approach 1:
The patent applies parameter changes by allowing the fixed center location to be configurable based on lens specifications. While the center is fixed for a given lens to simplify calibration, the system can adapt to different lens designs by adjusting the radial distortion coefficients (K1, K2, etc.) and the fixed center position parameters. This enables the same calibration framework to work across different lens designs while maintaining the simplification benefits of a fixed center approach.
3Device complexity
If focus is adjusted during manufacture, then the need for mechanical or electronic focus systems is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies mechanics substitution by replacing mechanical or electronic focus adjustment systems with a digital/post-processing focus solution. Instead of using motors, actuators, or mechanical focus mechanisms during operation, the system captures images with fixed focus during manufacturing and then applies digital refocusing algorithms during post-processing. This eliminates complex mechanical focus systems while achieving the desired focus flexibility, though it does require precise focus adjustment during the manufacturing phase.
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 enables straightforward and stable online calibration of lens distortion in multi-camera systems, improving accuracy and reducing manufacturing costs by setting the center of radial distortion to a common point, allowing for accurate image distortion correction without complex calibration processes.
Implementation Method 1
the modeling of radial distortion of lenses used in ADAS
Implementation Method 2
determining the radial distortion parameters of a camera after production
Implementation Method 3
lenses can be accurately modeled using the pinhole camera model
Data Source
Figure 1
AI summary
A camera and production technique for an ADAS. The camera lens and image sensor are positioned along multiple axes using a target located at a first distance from the lens to establish a first relative position between the lens and the image sensor. The first relative position between the lens and the image sensor is modified by a predetermined amount for an object located a second distance from the lens. The second distance is larger than the first distance.