Camera Calibration via Mobile Carrier Markers

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Solution Overview

Problem

Current methods for calibrating traffic surveillance cameras, especially in large field-of-view environments like road tunnels or motorways, are time-consuming and require manual placement and measurement of markings, necessitating frequent recalibration due to misalignment from tunnel washing or collisions.

Innovation Solution

A method using a mobile carrier, such as a vehicle, with pre-measured markings that moves across the camera's field of view, allowing for camera projection parameter determination without manual marking placement, utilizing the direct linear transformation (DLT) method and the Gauss-Newton method to solve the DLT equation, enabling quick and accurate calibration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If manual markings are placed and measured in the viewing space, then camera projection parameters can be determined accurately, but the calibration process becomes time-consuming and requires road blocking

Engineering Contradiction:

Improvecamera projection parameters determinationVSAvoidcalibration process time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The markings are pre-measured and attached to a mobile carrier (vehicle) before entering the camera's field of view. This preliminary preparation eliminates the need for time-consuming manual placement and measurement during the actual calibration process, allowing the vehicle to simply drive through the field of view for rapid parameter determination.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If manual markings are placed and measured, then accurate calibration is achieved, but frequent recalibration is necessary due to misalignment from tunnel washing or collisions

Engineering Contradiction:

Improvecamera calibration accuracyVSAvoidrecalibration frequency

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

Instead of placing permanent markings on the road that are vulnerable to damage and displacement, the invention uses a mobile carrier that carries markings as a temporary, replaceable copy. When misalignment occurs, the entire carrier with its pre-measured markings can be quickly replaced or repositioned, avoiding the need for time-consuming recalibration of fixed road markings.

Inventive Principle:

Principle #26Copying

3Reliability

If at least six markings are distributed throughout the field of vision, then sufficient data for calibration is obtained, but the complexity of manual placement and measurement increases

Engineering Contradiction:

Improvecalibration data sufficiencyVSAvoidmarking placement and measurement process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention combines multiple markings onto a single mobile carrier (vehicle), integrating them into one unified calibration object. This merging reduces the complexity of placing and measuring six separate markings distributed throughout the field of view, as the entire set is now attached to one moving object that passes through the field of view, simplifying the calibration process while maintaining data sufficiency.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentEP2249580B1Method for calibrating the image of a camera

Publication Date: 2019.09.04 KAPSCH TRAFFICCOM AG

Figure 1~2b

AI summary

The method involves determining the camera projection parameter of a camera projection of the viewing area. A movable carrier (4) is provided with four markers viewed from the camera (1), which span a volume and forms world points (w-1,w-2,w-3,w-4,w-5,w-6,w-7,w-8) in the viewing area. An image of the viewing area is recorded, where the carrier is moved in viewing area.