Thermally Invariant Calibration Artifact for Accurate Optical Pose Checks

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Solution Overview

Problem

Existing calibration artifacts for optical position measuring systems are susceptible to thermal and mechanical influences, leading to inaccurate geometric deviation measurements in machines due to changes in the relative positions of light sources, which are not universally applicable and require specific machine tool geometries.

Innovation Solution

A calibration artifact comprising a base body with selectively activatable light sources and a thermally invariant light source carrier, designed to maintain consistent light source positions despite temperature and mechanical changes, using a thermally stable material like Invar, and a recessed arrangement to allow independent expansion and contraction, ensuring accurate pose determination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a conventional calibration artifact with light sources is used, then the relative positions of light sources can be determined, but thermal and mechanical influences cause undefined changes in the relative positions, preventing accurate determination of calibration data

Engineering Contradiction:

Improveaccuracy of pose determinationVSAvoidthermal and mechanical influences

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent changes the physical parameter of the carrier material from conventional materials to thermally invariant material (Invar), which has a coefficient of thermal expansion of approximately zero. This parameter change ensures that the relative positions of light sources remain constant despite temperature variations, eliminating thermal influences on measurement accuracy.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a composite structure combining a base body with a light source carrier made of thermally invariant material (Invar). This composite material approach allows the carrier to maintain dimensional stability under thermal and mechanical loads, preventing undefined changes in light source relative positions while allowing the base body to expand or contract independently.

Inventive Principle:

Principle #40Composite materials

2Measurement precision

If a calibration artifact requiring specific machine tool geometry is used, then accurate calibration can be performed, but it cannot be used universally across different machine types

Engineering Contradiction:

Improvecalibration accuracyVSAvoiduniversal applicability

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent designs a calibration artifact with a standardized structure consisting of a base body and a light source carrier with at least two light sources arranged at defined relative positions. This universal design allows the same artifact to be used across different machine tools and measurement systems without requiring machine-specific customization, enabling universal applicability while maintaining calibration accuracy.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If the light source carrier is made of thermally invariant material, then temperature-related displacement is minimized, but the device complexity increases due to the specialized material and recessed arrangement

Engineering Contradiction:

Improvetemperature stabilityVSAvoidstructural complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies thermally invariant material (Invar) specifically to the light source carrier portion that requires dimensional stability, while the base body can be made of conventional materials. This localized application of specialized material properties maintains temperature stability where needed without unnecessarily increasing the complexity of the entire device structure.

Inventive Principle:

Principle #3Local quality

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

Ensures accurate geometric deviation checking in machines by minimizing temperature-related displacement and mechanical distortions, allowing large-volume measurement without costly modifications, and maintaining precise calibration across various machine types.

Implementation Method 1

the light source carrier being made of a thermally invariant material

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentEP4524512B1Calibration artifact

Publication Date: 2025.12.31 DR JOHANNES HEIDENHAIN GMBH

Figure 1a~1b
Figure 2~3b
Figure 4

AI summary

The present invention relates to a calibration artifact for checking the geometric deviations of a machine using an optical position measuring system. It comprises a base body on which a first group with at least one selectively activatable light source is arranged, and a light source carrier arranged on the base body on which a second group with several selectively activatable light sources is arranged. The light source carrier consists of a thermally invariant material (Fig. 2).