Displacement Sensor Using Inclined Linear Light Source

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Solution Overview

Problem

Confocal displacement gauges with chromatic aberration lenses are costly to design and manufacture, and their size cannot be easily reduced due to the independent nature of the light source, objective lens, and spectroscope, leading to high production costs and limited miniaturization potential.

Innovation Solution

A displacement sensor design utilizing a linear light source, beam splitter, line sensor, and imaging lens with an inclination of a predetermined angle, along with an inclination sensor and detection circuit to correct displacement measurements, allowing for a simpler and more cost-effective optical system without the need for expensive chromatic aberration lenses or spectrometers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If chromatic aberration objective lens and spectroscope are used to achieve high measurement precision, then measurement accuracy is improved, but device complexity and manufacturing cost increase

Engineering Contradiction:
Improvedisplacement measurement accuracyVSAvoidoptical system complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the spectroscope from the optical system, replacing the chromatic aberration-based wavelength discrimination method with a direct imaging method that uses a simple imaging lens to form images at different positions corresponding to different wavelengths, thereby simplifying the device while maintaining measurement precision

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent creates multiple virtual images of the light source at different positions along the optical axis through the imaging lens, where each image position corresponds to a specific wavelength range, allowing wavelength discrimination without requiring a spectroscope

Inventive Principle:
Principle #26Copying

2Measurement precision

If chromatic aberration objective lens is designed with large chromatic aberration to improve measurement precision, then measurement accuracy is improved, but design cost and manufacturing cost increase

Engineering Contradiction:
Improvedisplacement measurement accuracyVSAvoidlens design and manufacturing
Core Design Contradiction:
Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent replaces the expensive chromatic aberration objective lens with a standard imaging lens that has simpler design requirements and lower manufacturing cost, sacrificing the need for specially designed chromatic aberration lenses while maintaining measurement functionality through a different optical approach

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent changes the optical approach from relying on chromatic aberration parameters to using image position parameters, where displacement is measured by detecting the position of the formed image rather than by analyzing chromatic aberration characteristics

Inventive Principle:
Principle #35Parameter changes

3Measurement precision

If light source, objective lens, and spectroscope are designed as independent components to achieve high measurement precision, then measurement accuracy is improved, but device size increases

Engineering Contradiction:
Improvedisplacement measurement accuracyVSAvoidsensor size
Core Design Contradiction:
Measurement precisionVSVolume of moving object

Solution Approach 1:

The patent merges the functions of the light source, imaging lens, and image detector into a more compact integrated system, where the imaging lens directly forms images on the detector without requiring separate spectroscope components, enabling miniaturization while maintaining measurement precision

Inventive Principle:
Principle #5Merging (Combining)

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 design achieves high accuracy and cost-effectiveness while reducing the size of the displacement sensor, equivalent to chromatic aberration type sensors, using a simpler optical system that maintains resolution and accuracy.

Implementation Method 1

the imaging lens forms an image of the linear light source at a position conjugate with the linear light source

Methodology Applied
Scientific EffectOptical focusing: Lens

Implementation Method 2

the beam splitter is disposed between the linear light source and the imaging lens

Methodology Applied
Scientific EffectLight reflection: Reflection

Implementation Method 3

the line sensor is disposed at a position conjugate with the image formed by the imaging lens through the imaging lens and the beam splitter

Methodology Applied
Scientific EffectPhotoelectric detection: Photoelectric Effect

Data Source

PatentEP3460386B1Displacement sensor
Publication Date: 2021.07.14 YOKOGAWA ELECTRIC CORP
  • EP3460386B1 patent drawingFigure 1
  • EP3460386B1 patent drawingFigure 2
  • EP3460386B1 patent drawingFigure 3

AI summary

A displacement sensor includes a linear light source which emits a linear beam, a beam splitter, a line sensor, and an imaging lens. The linear light source is disposed with an inclination of a predetermined angle with respect to a perpendicular line of an optical axis of the imaging lens. The imaging lens forms an image of the linear light source at a position conjugate with the linear light source with an inclination of a predetermined angle with respect to the perpendicular line of the optical axis of the imaging lens. The beam splitter is disposed between the linear light source and the imaging lens. The line sensor is disposed at a position conjugate with the image formed by the imaging lens through the imaging lens and the beam splitter so that the optical axis of the imaging lens has the inclination of the predetermined angle with respect to the perpendicular line of the optical axis reflected by the beam splitter.