Optical System Calibration Using Marking Elements and Light Structures

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Solution Overview

Problem

Existing optical systems face challenges in quickly and simply calibrating distance determination systems, particularly in medical navigation and endoscopic applications, where precise spatial positioning and orientation of optical components are critical.

Innovation Solution

A calibration procedure and device that utilize a detection system with marking elements and a measuring camera to record spatial positions, project a light structure onto a carrier with a calibration pattern, and determine coordinates in both measurement and image coordinate systems, allowing for the calibration of distance determination devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional calibration methods are used, then calibration accuracy can be achieved, but calibration time and complexity increase significantly

Engineering Contradiction:
Improvecalibration accuracyVSAvoidcalibration time
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The patent applies preliminary action by pre-defining multiple calibration positions and arranging marking elements at these positions before the actual calibration process. The optical system is moved to these pre-prepared positions sequentially, eliminating the need for complex real-time calculations and measurements at each position. This preparation in advance significantly reduces calibration time while maintaining accuracy through the pre-established geometric relationships between marking elements.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The calibration process is segmented into discrete, independent steps: moving the optical system to predetermined positions, capturing images at each position, and processing data separately for each position. This segmentation allows parallel processing of multiple positions and simplifies the overall calibration workflow, reducing total calibration time while maintaining measurement precision through systematic data collection at each segment.

Inventive Principle:
Principle #1Segmentation

2Measurement precision

If complex calibration procedures are implemented, then measurement precision improves, but device complexity and ease of operation deteriorate

Engineering Contradiction:
Improvecalibration accuracyVSAvoidcalibration system complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent implements self-service by using the optical system's own imaging capability to capture images of marking elements during calibration. The system uses its internal camera and processing units to automatically detect marking element positions and calculate calibration parameters without requiring external measurement devices or complex auxiliary equipment. This self-calibration approach reduces device complexity while maintaining high measurement precision.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The marking elements serve multiple functions: they act as reference targets for calibration, provide spatial position information, and enable verification of calibration accuracy. The same marking elements are used throughout the calibration process at multiple positions, eliminating the need for different calibration tools or procedures. This multi-functionality simplifies the overall system while ensuring accurate calibration results.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Measurement precision

If multiple calibration positions are used, then calibration accuracy improves, but the number of required measurements and processing steps increases

Engineering Contradiction:
Improvecalibration accuracyVSAvoidmeasurement and processing complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by pre-defining multiple calibration positions and marking element arrangements before calibration begins. These positions are calculated in advance based on the optical system's characteristics, so that when the system is moved to each position, the required measurements are already optimized. This pre-planning reduces the complexity of real-time processing while maintaining high accuracy through multiple positions.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent uses identical marking elements replicated at multiple predetermined positions throughout the calibration process. Each marking element is a copy of the others, with the same geometric features and reflectivity characteristics. This copying approach allows the system to use the same detection and processing algorithms at each position, simplifying the overall processing complexity while improving accuracy through multiple independent measurements.

Inventive Principle:
Principle #26Copying

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

Enables rapid and precise calibration of optical systems, ensuring accurate spatial positioning and orientation of optical components, enhancing the reliability of medical navigation and endoscopic procedures.

Implementation Method 1

These systems can determine distances, particularly the distance between the optical system and an object, based on the principle of triangulation using collimated radiation (especially laser radiation).

Methodology Applied
Scientific EffectTriangulation:

Implementation Method 2

The measuring camera of the detection system is based, in particular, on the principle of a stereo camera, i.e., For example, it has two sensor elements (especially CCD chips) spaced apart from each other, which receive light from an object (especially a marker element of the detection system) at different angles and at different times, so that the spatial position of the object can be reconstructed from the data of the sensor elements.

Methodology Applied
Scientific EffectStereo vision:

Implementation Method 3

These systems can determine distances, particularly the distance between the optical system and an object, based on the principle of triangulation using collimated radiation (especially laser radiation).

Methodology Applied
Scientific EffectLaser: Laser

Data Source

PatentEP2627237B1Method and device for calibrating an optical system, distance determining device, and optical system
Publication Date: 2022.08.24 STRYKER EUROPEAN OPERATIONS LIMITED
  • EP2627237B1 patent drawingFigure 1
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AI summary

The invention relates to a method and device for calibrating a distance determining device for determining a distance or a position vector between an optical system and an object, wherein the method comprises the following steps: a) providing a detecting system, which comprises a plurality of marking elements and a measuring camera for detecting the spatial position of the marking elements; b) arranging the marking elements on the optical system and/or the distance determining device; c) providing a carrier, to which a calibration pattern is connected and/or which forms a calibration pattern; d) projecting a light structure onto the carrier by means of the distance determining device; e) detecting the marking elements, the calibration pattern, and/or carrier marking elements arranged on the carrier by means of the measuring camera; f) determining the spatial position of the marking elements and thus of the optical system using data of the measuring camera; g) determining coordinates of the calibration pattern in a first coordinate system associated with the measuring camera using data of the measuring camera; h) creating an image of the calibration pattern and of the light structure by means of a camera of the optical system; i) determining coordinates of the image of the calibration pattern and of the light structure in a second coordinate system associated with the image plane of the camera; and j) calibrating the distance determining device using the determined coordinates and the determined spatial position of the optical system.