Rebound Tonometer Probe Contact Detection via Induced Voltage

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Solution Overview

Problem

Existing rebound tonometers face issues with inaccurate alignment and potential harm to objects due to manual setup, varying forehead geometries, and the high cost and complexity of ultrasonic sensors, leading to unreliable measurements.

Innovation Solution

A rebound tonometer with a magnetic elongated probe, measurement and drive coils, and a controller that detects contact using induced voltage, allowing for automatic alignment and safe, reliable measurement cycles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If manual alignment methods are used to position the rebound tonometer, then the device can be set up without complex automation systems, but the alignment accuracy deteriorates leading to unreliable measurements

Engineering Contradiction:
Improvealignment accuracyVSAvoidalignment system complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces manual mechanical alignment with an optical detection system. A light source and sensor detect the position of alignment marks on the tonometer relative to the eye, automatically determining proper positioning without manual intervention. This substitutes mechanical alignment procedures with optical sensing and automated control.

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

Solution Approach 2:

The patent uses alignment marks that create a visual copy or representation of the desired position. The optical system detects these marks to determine tonometer positioning, creating a graphical copy of the alignment state that can be processed automatically to ensure precise positioning.

Inventive Principle:
Principle #26Copying

2Measurement precision

If the rebound tonometer is positioned too close to the object, then measurement sensitivity may improve, but the risk of harmful contact increases

Engineering Contradiction:
Improvemeasurement sensitivityVSAvoidcontact harm risk
Core Design Contradiction:
Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent performs preliminary alignment detection and positioning before the actual measurement is taken. The optical alignment system verifies proper positioning and safe distance before the rebound probe contacts the eye, ensuring that when measurement does occur, the tonometer is optimally positioned without excessive closeness that could cause harm.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent implements a feedback mechanism where the optical alignment system continuously monitors tonometer position relative to the eye. This feedback allows the system to adjust positioning to maintain optimal measurement conditions while preventing harmful proximity, creating a closed-loop safety and precision control system.

Inventive Principle:
Principle #23Feedback

3Object-affected harmful factors

If the rebound tonometer is positioned too far from the object, then safety is improved, but measurement accuracy deteriorates

Engineering Contradiction:
ImprovesafetyVSAvoidparameter measurement accuracy
Core Design Contradiction:
Object-affected harmful factorsVSMeasurement precision

Solution Approach 1:

The patent performs preliminary alignment detection and positioning before the actual measurement is taken. The optical alignment system verifies proper positioning and safe distance before the rebound probe contacts the eye, ensuring that when measurement does occur, the tonometer is optimally positioned without excessive closeness that could cause harm.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent implements a feedback mechanism where the optical alignment system continuously monitors tonometer position relative to the eye. This feedback allows the system to adjust positioning to maintain optimal measurement conditions while preventing harmful proximity, creating a closed-loop safety and precision control system.

Inventive Principle:
Principle #23Feedback

4Device complexity

If holders are mechanically set on the rebound tonometer for alignment, then the device structure can be simple, but alignment precision deteriorates due to manual setup errors

Engineering Contradiction:
Improveholder structure simplicityVSAvoidalignment precision
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The patent replaces manual mechanical alignment with an optical detection system. A light source and sensor detect the position of alignment marks on the tonometer relative to the eye, automatically determining proper positioning without manual intervention. This substitutes mechanical alignment procedures with optical sensing and automated control.

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

Solution Approach 2:

The patent uses alignment marks that create a visual copy or representation of the desired position. The optical system detects these marks to determine tonometer positioning, creating a graphical copy of the alignment state that can be processed automatically to ensure precise positioning.

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

Ensures accurate and safe measurement of object properties by ensuring the probe aligns optimally before measurement, preventing damage and reducing costs through a simple, effective method.

Implementation Method 1

a drive coil arranged inside the body and to partially surround the magnetic elongated probe

Methodology Applied
Scientific EffectMagnetic field: Magnetic Field

Implementation Method 2

energizing the drive coil moves the magnetic elongated probe in respect to the body

Methodology Applied
Scientific EffectLorentz force: Lorentz Force

Implementation Method 3

measuring a first induced voltage in the measurement coil as a function of time during a first time period

Methodology Applied
Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentEP4418984B1Rebound tonometers and methods for using rebound tonometers
Publication Date: 2025.08.20 ICARE FINLAND OY
  • EP4418984B1 patent drawingFigure 1~2A
  • EP4418984B1 patent drawingFigure 2B~2C
  • EP4418984B1 patent drawingFigure 3~4B

AI summary

Disclosed is rebound tonometer comprising: body (102, 206, 302) having proximal end (110, 214) and distal end (112, 216), and opening (114) at proximal end; magnetic elongated probe (104, 208, 304) having first end (116, 218) protruding outside of body at first distance (D1) from opening, and second end (118, 220) inside body, said probe being aligned with and movable along axis (120) of rebound tonometer; measurement coil (106, 210, 306) and drive coil (108, 212, 308) arranged inside body and partially surrounding magnetic elongated probe; and controller (310) configured to: detect contact between object (204) and first end when rebound tonometer is in use, by: energising drive coil to move magnetic elongated probe to have first end at second distance (D2) from proximal end; measuring first induced voltage in measurement coil; and comparing said voltage with predetermined criterion; and initiate measurement cycle of rebound tonometer when contact is detected.