Encoder Tilt Compensation via Asymmetric Element Array Layout

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional encoders experience accuracy deterioration when the scale is disposed in a tilted manner with respect to the receiving unit, leading to shifts in phase differences and reduced output voltage due to interference fringes generated at a tilt angle, affecting the calculation of relative movement.

Innovation Solution

The encoder design includes a light-receiving unit with element arrays disposed in a specific configuration where the sum of distances from a reference position to positive and negative phase signal element arrays is the same for all phases, canceling out phase shifts caused by tilting, and ensuring uniform light distribution across the receiving surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the scale is disposed in a tilted manner with respect to the receiving unit, then the encoder can accommodate misalignment, but the accuracy deteriorates due to phase shifts and amplitude reduction

Engineering Contradiction:

Improvetolerance to tilt angleVSAvoidaccuracy of relative movement detection

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent applies asymmetry by configuring element arrays with different distances from the reference position for positive and negative phase signals. Specifically, the distance from the reference position to the positive phase signal element array differs from the distance to the negative phase signal element array, creating an asymmetric layout that compensates for tilt-induced phase shifts and maintains measurement accuracy

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent changes the spatial parameters of the element arrays by adjusting their distances from the reference position. By optimizing these distance parameters, the system compensates for the effects of tilt angles, maintaining accurate phase difference measurements even when the scale is not perfectly aligned with the receiving unit

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If element arrays are disposed asymmetrically to compensate for tilt, then accuracy is maintained, but the device complexity increases

Engineering Contradiction:

Improveaccuracy of differential signalsVSAvoidcomplexity of element array configuration

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent segments the receiving unit into multiple element arrays, each responsible for detecting specific phase signals. By dividing the detection function across multiple segmented arrays with specific distance relationships, the system achieves tilt compensation through a modular configuration that manages complexity through functional segmentation

Inventive Principle:

Principle #1Segmentation

3Measurement precision

If the distance between positive and negative phase element arrays differs, then phase shifts are canceled, but the light distribution uniformity becomes challenging

Engineering Contradiction:

Improvephase difference stabilityVSAvoiduniformity of light distribution

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The patent optimizes the spatial parameters of element arrays by carefully selecting their distances from the reference position. This parameter optimization ensures that the asymmetric configuration cancels tilt-induced phase shifts while maintaining acceptable light distribution characteristics across the receiving surface

Inventive Principle:

Principle #35Parameter changes

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 configuration maintains the accuracy and phase difference of differential signals, even when the scale is tilted, by canceling out phase shifts and reducing amplitude reduction, resulting in stable interference fringes similar to those at zero tilt angles.

Implementation Method 1

The light radiated from the light source becomes a plurality of diffraction rays via the graduations

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

The plurality of diffraction rays generate interference fringes having the same period as that of the graduations

Methodology Applied

Scientific EffectInterference: Interference

Implementation Method 3

The light-receiving unit converts the light received at the light-receiving surface into detection signals

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Data Source

PatentUS11774270B2Encoder

Publication Date: 2023.10.03 MITUTOYO CORP

AI summary

An encoder includes scale and detection head. The detection head includes light source (transmitting unit) and light-receiving unit (receiving unit). The light-receiving unit includes light-receiving surface (receiving surface) and converts light received at the light-receiving surface 50 into differential detection signals with two phases and outputs the same. The light-receiving surface includes element array group including four element arrays provided in a parallel manner along an orthogonal direction, with each element array including a plurality of light-receiving elements (receiving elements). The plurality of element arrays in the element array group are disposed at positions where the sum of: (i) a distance in the orthogonal direction from a reference position to a positive phase signal element array; and (ii) a distance in the orthogonal direction from the reference position to the negative phase signal element array, is the same for all the phases of the at least two phases.