Rolling Shutter Detection in CMOS Camera Calibration
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Solution Overview
Problem
The rolling shutter effect in images captured by CMOS cameras of motor vehicles causes perspective distortion due to non-parallel sensor planes and varying exposure times, leading to distorted depictions of the environmental region, which complicates camera calibration and image quality.
Innovation Solution
A method to detect the rolling shutter effect by determining motion vectors between feature positions in consecutive images, calculating a correction factor based on the vertical span of these vectors, and applying it to compensate for the effect, thereby enabling high-quality, distortion-free images and accurate camera calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a rolling shutter method is used to capture images with CMOS sensors in moving vehicles, then the camera can capture environmental regions efficiently, but perspective distortion occurs causing rolling shutter effect
Solution Approach 1:
The patent replaces the mechanical/optical constraint of simultaneous exposure (which would be required to eliminate rolling shutter effect) with a computational approach. By using motion vectors and vertical span calculations from consecutive frames, the system computationally detects and compensates for the distortion, allowing the rolling shutter method to continue being used for efficient image capture.
Solution Approach 2:
The patent changes the parameter being measured from raw pixel positions to motion vectors derived from feature tracking between frames. By calculating the vertical span of motion vectors and comparing it against threshold values, the system dynamically adjusts for the rolling shutter effect, transforming the distortion problem into a detectable and correctable parameter variation.
2Adaptability or versatility
If the sensor plane is not parallel to the ground plane or aligned with the longitudinal axis, then camera installation flexibility is improved, but perspective distortion increases
Solution Approach 1:
The patent implements a feedback mechanism where motion vectors from consecutive frames are analyzed to detect vertical span variations. This feedback information is used to identify and compensate for perspective distortion caused by non-standard camera installations, allowing the system to maintain image quality regardless of camera orientation or position.
Solution Approach 2:
The patent performs preliminary detection of the rolling shutter effect by calculating motion vectors and vertical spans before final image processing. This preliminary analysis allows the system to pre-compensate for distortion artifacts, ensuring that subsequent image processing operations work with corrected data rather than attempting to fix distortion afterward.
3Measurement precision
If feature positions are tracked between consecutive frames to detect rolling shutter effect, then detection accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent segments the image into distinct features or interest points that can be tracked independently between frames. By focusing computational resources on detecting and tracking these discrete features rather than analyzing all pixels, the system achieves accurate motion vector calculation with reduced computational complexity. The vertical span is then derived from these segmented feature trajectories.
Data Source
AI summary
The invention relates to a method for detecting a rolling shutter effect in images of an environmental region (9) of a motor vehicle (1) captured by an image sensor of at least one camera (4) of the motor vehicle (1) comprising a plurality of sensor lines (15), including the following steps: a) determining a first position (P1) on a sensor plane (13) of the image sensor corresponding to a feature (14) when capturing a first image and identifying a second position (P2) on the sensor plane (13) corresponding to the feature (14) when capturing a second image, b) determining a motion vector (v) characterizing a displacement of the feature (14) on the sensor plane (13) between the first position (P1) and the second position (P2), c) determining a vertical span (Δy) of the motion vector (v) characterizing a number of sensor lines (15) at least partially covered by the motion vector (v), d) detecting the rolling shutter effect based on the vertical span (Δy). I addition, the invention relates to a computing device (3), a driver assistance system (2) as well as a motor vehicle (1).