Calibration System for Tracking Equipment Using Rotating Sensor Assembly

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Solution Overview

Problem

Calibrating precise tracking systems, such as optical and acoustic tracking systems, is challenging due to manufacturing imperfections, and existing methods struggle to accurately measure and adjust for errors in these systems.

Innovation Solution

A calibration system comprising a stationary support element and a sensor assembly with photodetectors that rotate in circular paths, allowing for precise measurement of errors by generating light patterns and using non-linear solvers to calculate calibration factors, which can be applied to optical or acoustic tracking systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional calibration equipment is used to calibrate tracking systems, then the calibration process can be performed, but the calibration accuracy is limited because the tolerances on calibration equipment are greater than the expected errors in the tracking systems

Engineering Contradiction:

Improvecalibration accuracyVSAvoidequipment tolerance

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

Instead of using a more precise tracking system to calibrate a less precise one, the patent inverts the approach by using a mechanically precise circular motion system to generate known ground truth positions. The circular paths are defined by rigid mechanical constraints rather than by a higher-precision tracking system, allowing calibration of precise tracking systems without requiring even more precise reference equipment.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent performs preliminary action by pre-defining precise circular paths through mechanical constraints before the calibration process begins. The photodetectors are constrained to move in perfect circles by the mechanical structure, establishing known ground truth positions in advance, which eliminates the need for complex real-time reference measurements during calibration.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If photodetectors are arranged to sweep circular paths for calibration, then measurement precision improves, but device complexity increases due to the need for precise rotational constraints and multiple photodetectors

Engineering Contradiction:

Improveerror measurement accuracyVSAvoidsensor assembly structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent employs circular (curved) paths for the photodetectors instead of linear arrangements. The dome-shaped outer surface and circular sweep paths provide geometric constraints that naturally define precise positions through curvature, allowing accurate error measurement while using relatively simple rotational mechanics rather than complex multi-axis positioning systems.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The sensor assembly with multiple photodetectors arranged in specific patterns serves multiple functions: it can detect light from emitters at various positions, define circular calibration paths, and provide redundant measurements. This multi-functional design improves measurement precision without requiring separate dedicated systems for each function, thereby managing device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If multiple photodetectors are used to improve calibration accuracy, then measurement precision increases, but the difficulty of detecting and measuring increases due to the complexity of coordinating multiple detectors

Engineering Contradiction:

Improvetracking error measurementVSAvoidcoordinate multiple detectors

Core Design Contradiction:

Measurement precisionVSDifficulty of detecting and measuring

Solution Approach 1:

The patent uses periodic action by rotating the sensor assembly in circular motion, causing photodetectors to sweep through defined paths at regular intervals. This periodic movement creates predictable, repeating measurement patterns that simplify data processing and coordinate multiple detectors, as the temporal and spatial relationships between detections follow consistent periodic patterns rather than requiring complex real-time coordination.

Inventive Principle:

Principle #19Periodic action

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

This method enables accurate measurement and correction of tracking system errors, improving the precision and performance of tracking systems used in virtual and augmented reality applications.

Implementation Method 1

A calibration system may be summarized as comprising: a stationary support element; and a sensor assembly rotatably coupled to the stationary support element, the sensor assembly includes at least one photodetector constrained to rotate about an axis of rotation of the sensor assembly

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Data Source

PatentUS11137484B1Systems and methods to calibrate tracking systems

Publication Date: 2021.10.05 VALVE CORPORATION

AI summary

A calibration system for calibrating tracking equipment includes a segmented dish formed from a plurality of individual panels, a support frame formed from a plurality of individual structural shafts to support the segmented dish, and a rotatable platform to hold the tracking equipment to be calibrated. The segmented dish includes a plurality of sensor assemblies rotatably coupled to its individual panels and a plurality of motor assemblies to control operation of the sensor assemblies.