Non-Diamond Turnable Mirror Finish Layer

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Solution Overview

Problem

High precision mirrors made from materials like beryllium and silicon carbide face challenges in achieving a smooth surface finish due to their granular composition and thermal expansion mismatches, leading to optical scatter and bi-metallic bending issues, which limit their performance in visible wavelength applications.

Innovation Solution

A mirrored apparatus with a substrate made from non-diamond point turnable inorganic materials, featuring a finish layer deposited using thin-film vapor deposition techniques and polished to achieve a high degree of smoothness, along with a thin reflective layer, which avoids bi-metallic effects and improves surface finish to around 5-15 Angstroms RMS.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If diamond point turning is used to machine inorganic materials like beryllium and silicon carbide, then manufacturing precision can be improved, but the granular composition and thermal expansion mismatches cause bi-metallic bending and surface finish degradation

Engineering Contradiction:

Improvesurface finishVSAvoidbi-metallic bending

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

A thin-film finish layer is deposited as an intermediary between the substrate and the reflective layer. This finish layer is specifically selected to have compatible thermal expansion properties with both layers, acting as a mediator that prevents thermal stress-induced bending while enabling high-precision surface finishing through controlled polishing processes.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The mirror structure uses a composite approach by combining the inorganic substrate material with a thin-film finish layer and reflective layer. Each layer is carefully selected for its specific properties, creating a composite structure that leverages the high stiffness of the substrate while using the thin-film layers to manage thermal expansion and provide the necessary optical surface quality.

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If traditional optical manufacturing methods are used to finish the optical surface, then mirror finish can be achieved, but the process is time-consuming and requires custom equipment

Engineering Contradiction:

Improveoptical surface finishVSAvoidmanufacturing time

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent replaces traditional mechanical polishing methods with thin-film vapor deposition techniques to create the finish layer. This substitution eliminates the need for time-consuming mechanical polishing equipment and processes, while achieving the required optical surface finish through controlled deposition and subsequent light polishing operations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The finish layer is deposited in advance as a thin-film layer before the final reflective layer is applied. This preliminary action prepares the substrate with a controlled surface profile and finish quality that facilitates the subsequent reflective layer deposition, reducing the need for post-processing adjustments and accelerating the overall manufacturing timeline.

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If electroless nickel plating is applied to achieve a smooth surface, then surface finish improves, but thermal expansion mismatch causes bi-metallic bending

Engineering Contradiction:

Improvesurface smoothnessVSAvoidthermal expansion mismatch

Core Design Contradiction:

Manufacturing precisionVSStability of the object's composition

Solution Approach 1:

The patent changes the material parameter selection by replacing electroless nickel plating with a thin-film finish layer material that has thermal expansion properties matched to the substrate. This parameter change in material selection eliminates the thermal expansion mismatch that causes bi-metallic bending, while still achieving the required surface smoothness through controlled thin-film deposition and polishing.

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

The solution provides mirrors with improved optical imaging performance by reducing scatter and surface figure errors, making them easier and cheaper to manufacture while maintaining accuracy, and avoiding the need for custom equipment.

Implementation Method 1

The finish layer has a polished surface opposite the substrate

Methodology Applied

Scientific EffectPolishing: Abrasion

Implementation Method 2

depositing a finish layer on the surface of the substrate... depositing a reflective layer on surface of the finish layer

Methodology Applied

Scientific EffectVapor deposition: Physical Vapour Deposition

Data Source

PatentUS12066591B2Visible quality mirror finishing

Publication Date: 2024.08.20 RAYTHEON CO

AI summary

According to one or more embodiments of the present invention, a mirrored apparatus includes a substrate with a non-metal inorganic material that is non-diamond turnable. The mirrored apparatus further includes a finish layer arranged on the surface of the substrate. The finish layer has a polished surface opposite the substrate. The mirrored apparatus also includes a reflective layer arranged on the polished surface of the finish layer.