Multi-Camera Extrinsic Calibration with Light-Emitting Reference Points

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Solution Overview

Problem

Existing electronic devices with multiple cameras face issues in maintaining accurate extrinsic calibration parameters due to positional changes or insufficient feature points in the user environment, leading to inaccurate data alignment and reduced user experience.

Innovation Solution

An extrinsic calibration parameter generating device and method that utilizes at least two image capturing devices to generate five- and six-degree-of-freedom information by analyzing light-emitting points in image frames, allowing for efficient calibration without additional assistance devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If extrinsic parameter calibration is performed by photographing feature points in the user environment, then calibration can be conducted during actual use, but the calibration accuracy deteriorates when there are insufficient feature points (e.g., too many white walls or blocked feature points)

Engineering Contradiction:
Improvecalibration operationVSAvoidextrinsic parameter calibration accuracy
Core Design Contradiction:
Ease of operationVSMeasurement precision

Solution Approach 1:

The patent introduces an external device with light-emitting points as an intermediary calibration tool. Instead of relying on feature points in the user environment, the system uses a dedicated calibration device that emits light points with known spatial relationships. This intermediary device ensures accurate feature detection and pairing regardless of the surrounding environment, resolving the contradiction between ease of calibration operation and calibration accuracy.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the calibration approach from using passive environmental feature points to using active light-emitting points with known parameters. By switching to light-emitting points with predetermined spatial relationships, the system ensures that feature points are always detectable and pairable, maintaining high calibration accuracy while allowing flexible operation during actual use.

Inventive Principle:
Principle #35Parameter changes

2Adaptability or versatility

If multiple cameras are used for pose tracking, then tracking functionality is enhanced, but the system complexity increases due to the need for extrinsic parameter calibration between cameras

Engineering Contradiction:
Improvepose tracking capabilityVSAvoidcalibration system complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The external calibration device serves as a mediator that simplifies the calibration process between multiple cameras. By providing a unified reference frame with known light-emitting point positions, it enables straightforward feature pairing and extrinsic parameter calculation, reducing the computational and operational complexity despite having multiple cameras for enhanced pose tracking.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent uses the external calibration device to create a known reference model that can be copied and recognized by multiple cameras. The light-emitting points form a standardized pattern that each camera can detect independently, and the system uses this copied reference information to calculate relative positions and orientations, simplifying the multi-camera calibration process.

Inventive Principle:
Principle #26Copying

Data Source

PatentEP4625324A1Extrinsic calibration parameter generating device, method, and non-transitory computer readable storage medium thereof
Publication Date: 2025.10.01 HTC CORP
  • EP4625324A1 patent drawingFigure 1
  • EP4625324A1 patent drawingFigure 2A~2B
  • EP4625324A1 patent drawingFigure 3A~3B

AI summary

An extrinsic calibration parameter generating device, method, and non-transitory computer readable storage medium thereof are provided. The device calculates a base image capturing device pose based on the light-emitting points of a plurality of image frames. The device generates a first extrinsic calibration parameter corresponding to at least two image capturing devices based on the image frames, and the first extrinsic calibration parameter is a five-degree-of-freedom information. The device generates a second extrinsic calibration parameter corresponding to the at least two image capturing devices based on the base image capturing device pose and the first extrinsic calibration parameter, and the second extrinsic calibration parameter is six-degree-of-freedom information.