Laser Device Protection Windows Offset Focal Shift

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Solution Overview

Problem

High-power laser devices experience focal shift due to temperature increases in the condensing assembly, leading to deteriorated processing quality of workpieces, as existing solutions fail to effectively suppress this shift.

Innovation Solution

Incorporating a cover with protection windows having positive and negative refractive index temperature coefficients, along with specific thermal properties and coatings, to offset refractive index changes and maintain focal stability during temperature increases.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the laser device operates at higher output, then the processing power increases, but the temperature increase of the condensing assembly becomes larger causing focal shift

Engineering Contradiction:

Improvelaser output powerVSAvoidfocal range stability

Core Design Contradiction:

PowerVSManufacturing precision

Solution Approach 1:

The patent changes the physical parameters of the protection windows by selecting materials with opposite refractive index temperature coefficients. The first protection window uses material with a positive coefficient while the second uses material with a negative coefficient, allowing their thermal-optical effects to compensate for each other and maintain focal stability at high power

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system employs a composite structure of multiple protection windows made from different materials with complementary thermal-optical properties. By combining materials with positive and negative refractive index temperature coefficients, the system creates a composite optical path that resists focal shift through mutual compensation of thermal effects

Inventive Principle:

Principle #40Composite materials

2Reliability

If protection windows are added to protect the condensing assembly, then the assembly is protected from smoke and gas, but focal shift occurs due to refractive index change with temperature

Engineering Contradiction:

Improvecondensing assembly protectionVSAvoidfocal range stability

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent addresses the focal shift problem by changing the material parameters of the protection windows. By selecting materials with opposite refractive index temperature coefficients, the system ensures that thermal-optical effects in one window compensate for those in the other, maintaining focal stability while providing necessary protection

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The protection windows serve as intermediary elements that both protect the condensing assembly from harmful environmental factors and manage thermal-optical effects. The dual-material design allows these intermediaries to compensate for each other's thermal refraction, solving both protection and focal stability requirements

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The solution effectively suppresses focal shifts, thereby improving the processing quality of workpieces by maintaining consistent laser focus, even at higher power outputs.

Implementation Method 1

The protection windows include at least one first protection window (22) having a positive refractive index temperature coefficient and at least one second protection window (24) having a negative refractive index temperature coefficient

Methodology Applied

Scientific EffectRefractive index temperature coefficient:

Implementation Method 2

correct and offset a focal shift owing to a refractive index change of the first protection window (22) by a refractive index change of the second protection window (24)

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 3

The optical lens and the mirror absorb energy of the laser light upon laser light irradiation, and raise in temperature

Methodology Applied

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

Data Source

PatentUS11101613B2Laser device and processing device

Publication Date: 2021.08.24 MITSUBISHI HEAVY IND LTD

AI summary

A laser device includes a condensing assembly for condensing laser light output from a laser oscillator and a cover for accommodating the condensing assembly, the cover including protection windows permeable to the laser light on an optical path of the laser light. The protection windows include at least one first protection window having a positive refractive index temperature coefficient and at least one second protection window having a negative refractive index temperature coefficient, the at least one first protection window and the at least one second protection window being arranged along the optical path of the laser light.