Composite Scale Displacement Measuring Apparatus

Solution Overview

Problem

Existing displacement measuring apparatuses face challenges in achieving high precision and resolution, particularly with magnetic types at lower pitches and optical types where precision is compromised by speed and response during measurement.

Innovation Solution

A displacement measuring apparatus combining a magnetic pattern and a diffraction grating aligned along the measuring axis, using a magnetic detection unit for high-speed and responsive measurements and an optical detection unit for precise and high-resolution measurements, with the magnetic pattern pitch being larger than the diffraction grating pitch.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If magnetic detection is used for high-speed measurement, then measurement speed is improved, but measurement precision deteriorates

Engineering Contradiction:

Improvemeasurement speedVSAvoidmeasurement precision

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The patent combines magnetic detection and optical detection systems into a single displacement measuring apparatus. The magnetic detection unit (using MR elements) provides high-speed measurement capability, while the optical detection unit (using photodetectors and diffraction grating) provides high-precision measurement capability. Both detection systems share common components including the scale, detector head, and signal processing circuitry, allowing the system to achieve both high speed and high precision simultaneously.

Inventive Principle:

Principle #5Merging (Combining)

2Measurement precision

If optical detection is used for high-precision measurement, then measurement precision is improved, but measurement speed deteriorates

Engineering Contradiction:

Improvemeasurement precisionVSAvoidmeasurement speed

Core Design Contradiction:

Measurement precisionVSSpeed

Solution Approach 1:

The patent combines magnetic detection and optical detection systems into a single displacement measuring apparatus. The magnetic detection unit (using MR elements) provides high-speed measurement capability, while the optical detection unit (using photodetectors and diffraction grating) provides high-precision measurement capability. Both detection systems share common components including the scale, detector head, and signal processing circuitry, allowing the system to achieve both high speed and high precision simultaneously.

Inventive Principle:

Principle #5Merging (Combining)

3Measurement precision

If magnetic pattern pitch is decreased for higher resolution, then measurement resolution is improved, but device complexity increases

Engineering Contradiction:

Improvemeasurement resolutionVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the conventional magnetic detection method with a dual-system approach where optical detection handles high-resolution measurements. The optical detection unit uses a diffraction grating with smaller pitch (10 μm) compared to the magnetic pattern pitch (50 μm), enabling higher resolution measurements without requiring excessively fine magnetic patterning. This substitution allows the system to achieve high resolution while maintaining manageable device complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 measurements with higher speed, response, precision, and resolution by leveraging the strengths of both magnetic and optical detection methods, allowing for detailed and accurate displacement measurements.

Implementation Method 1

a magnetic detection unit detecting a magnetic field generated by the magnetic pattern to generate first reproduced signals

Methodology Applied

Scientific EffectMagnetic field detection: Magnetic Field

Implementation Method 2

an optical detection unit detecting the light diffracted by the diffraction grating to generate second reproduced signals

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS7808650B2Displacement measuring apparatus

Publication Date: 2010.10.05 DMG MORI CO LTD

AI summary

Disclosed is a displacement measuring apparatus that includes a composite scale having a magnetic pattern and a diffraction grating each aligned in a direction of measuring axis, and a detector head moving in a direction of measuring axis relative to the composite scale. The detector head has a magnetic detection unit detecting a magnetic field exerted by the magnetic pattern to generate first reproduced signals, a light source irradiating the diffraction grating with light, and an optical detection unit detecting the light diffracted by the diffraction grating to generate second reproduced signals. In composite scale, the magnetic pattern and the diffraction grating are arranged such that a pitch of the first reproduced signals is larger than that of the second reproduced signals.