Photoelectric Encoder Antireflection Member Stray Light Reduction

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Solution Overview

Problem

Conventional photoelectric encoders suffer from reduced detection accuracy and reliability due to stray light generated by misalignment, which affects the precision of relative movement detection.

Innovation Solution

Incorporating an antireflection member to prevent stray light from entering the light receiving unit, either as a coating on the scale, lead frame, or within the light receiving unit, to ensure that only parallel light is transmitted and detected.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the light emission unit is downsized by using a hemispheroid-shaped lens member, then the device size is reduced, but stray light is generated due to corner portion scattering and misalignment sensitivity

Engineering Contradiction:

Improvelight emission unit sizeVSAvoidstray light

Core Design Contradiction:

Volume of moving objectVSObject-generated harmful factors

Solution Approach 1:

The patent extracts and removes the harmful corner portion from the optical system by designing the light emission unit to exclude sharp corners, thereby eliminating the scattering source while maintaining the compact hemispheroid shape

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent converts the potentially harmful corner portion into a beneficial rounded structure that, when properly designed, redirects stray light away from the light receiving unit while maintaining compact dimensions

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Volume of moving object

If the light emission unit is downsized, then the device size is reduced, but the unit becomes more susceptible to angle variation caused by misalignment

Engineering Contradiction:

Improvelight emission unit sizeVSAvoidalignment stability

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent incorporates light shielding structures in advance within the light emission unit to compensate for and cushion against the effects of misalignment, preventing stray light generation even when angular variations occur

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The patent introduces light shielding structures as intermediary elements between the light source and light receiving unit, which mediate the optical path to prevent misalignment effects from degrading performance

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If parallel light is emitted inclined with respect to the light receiving surface due to misalignment, then the device can be simpler, but detection accuracy deteriorates due to stray light

Engineering Contradiction:

Improvelight emission unit structureVSAvoidrelative movement detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent introduces light shielding structures as intermediary elements that correct the optical path without requiring complex realignment mechanisms, thereby maintaining simple device structure while improving measurement precision

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces complex mechanical alignment adjustment systems with integrated light shielding structures that passively correct optical path deviations, simplifying the overall device while maintaining high detection accuracy

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

This solution enhances the accuracy and reliability of the photoelectric encoder by minimizing stray light interference, allowing for precise measurement of relative movement.

Implementation Method 1

stray light generated by being reflected on the scale

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

antireflection member configured to prevent stray light generated by being reflected on the scale, from entering the light receiving unit

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 3

light source device configured to emit light (parallel light)

Methodology Applied

Scientific EffectLight: Light

Implementation Method 4

light receiving unit configured to receive light (parallel light) being emitted from the light source device and transmitted through the scale

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Data Source

PatentUS10648839B2Photoelectric encoder

Publication Date: 2020.05.12 MITUTOYO CORP

AI summary

Provided is a photoelectric encoder that can achieve higher accuracy while maintaining reliability by reducing stray light. An encoder 1 is a photoelectric encoder including a light source device 2 that emits parallel light, a scale 3 having calibrations C provided along a measurement direction, and a light receiving unit 4 that receives light being emitted from the light source device 2, and transmitted through the scale 3. The encoder 1 includes an antireflection member 30 that prevents stray light generated by being reflected on the scale 3, from entering the light receiving unit 4. Because the encoder 1 includes the antireflection member 30, the encoder 1 can achieve higher accuracy while maintaining reliability by reducing stray light entering the light receiving unit 4.