Non-Contact Finger Joint Angle Detection for Fine Motion Measurement

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Solution Overview

Problem

Conventional methods for measuring finger movements, such as playing a musical instrument or performing a surgical operation, hinder fine sensitivity due to sensors being directly mounted on finger joints, preventing accurate measurement.

Innovation Solution

An information processing device that detects finger joint angles in a non-contact manner using photoreflectors and 9-axis posture sensors, estimating finger posture without mounting sensors directly on joints, and an exoskeletal robot that reproduces these movements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If sensors are mounted directly on finger joints to measure movement, then measurement capability is achieved, but fine sensitivity of fingertips is hindered

Engineering Contradiction:
Improvefinger movement measurementVSAvoidfine sensitivity hindrance
Core Design Contradiction:
Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an intermediary optical system consisting of light sources and photodetectors positioned at a distance from the finger. This intermediary system measures finger joint angles by detecting changes in light reflection patterns, thereby achieving measurement capability without direct sensor contact that would hinder fine sensitivity

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the mechanical sensor mounting approach with an optical measurement system. Instead of physically attaching sensors to finger joints, the system uses light reflection and photodetector arrays to non-contactly measure joint angles, eliminating the mechanical interference while maintaining measurement precision

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Object-affected harmful factors

If non-contact optical sensors are used to detect finger joints, then fine sensitivity is preserved, but device complexity increases

Engineering Contradiction:
Improvefine sensitivity preservationVSAvoidoptical sensor system
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The optical sensor system is segmented into multiple independent photodetector elements arranged in arrays. Each photodetector measures local light reflection characteristics, and the collective data from segmented detectors is processed to determine joint angles, reducing individual detector complexity while maintaining overall system capability

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The optical sensor system is designed to measure multiple finger joints simultaneously using the same basic principle of light reflection detection. The system can track various joint angles (MP, PIP, DIP joints) and multiple fingers using a unified optical measurement approach, reducing overall system complexity through functional universality

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

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 accurate measurement and reproduction of fine finger movements without hindering sensitivity, allowing for effective transmission of skills to others.

Implementation Method 1

Light is introduced into the tissue at one point, passes through the tissue, and exits the tissue at a second point where a sensor receives the light as it exits the tissue

Methodology Applied
Scientific EffectLight transmission through living tissue: Light

Implementation Method 2

detects angles of at least some of joints of a finger in a non-contact manner

Methodology Applied
Scientific EffectLight reflection: Reflection

Data Source

PatentEP4119308B1Information processing device, information processing method, and information processing program
Publication Date: 2025.07.23 SONY GROUP CORP
  • EP4119308B1 patent drawingFigure 1
  • EP4119308B1 patent drawingFigure 2
  • EP4119308B1 patent drawingFigure 3

AI summary

An information processing device (100) includes a detection unit (110) and an estimation unit (152). The detection unit (110) detects the angles of at least some of the joints of a finger, in a non-contact manner. The estimation unit (152) estimates the posture of the finger on the basis of the angles of the joints detected by the detection unit (110).