Transferring Technology in Optimised Metal-Mirror Fabrication

Lead Research Organisation: University of Huddersfield
Department Name: Sch of Computing and Engineering

Abstract

The main objective of the proposed research is to transfer to British Industry advanced technologies in making metal mirrors - both existing methods in which the University of Huddersfield has considerable experience, and improvements to be developed during the project.

The idea of making mirrors out of metal goes right back to Sir Isaac Newton's reflecting telescope, which he built in 1668 as a way to overcome the colour fringe problem with the simple glass lenses available at that time. His chosen alloy - speculum - was hard and easy to polish, but tarnished quickly, and the ability to reflect light effectively, was not good by modern standards.

Aluminium alloys have superseded Speculum, due to aluminium's availability at low cost in large sizes, and because of its superior reflection properties and durability. Whilst it expands and contracts much more than glass with changing temperature, it settles down much more quickly because it conducts heat very well. Moreover, you can drop it or shake it and it will not break!

However, aluminium has a distinct disadvantage - it is soft and difficult to polish. For this reason, aluminium mirrors have normally been made in modest sizes by turning using a very high-precision lathe and diamond tools. Unfortunately, diamond-turning inevitably leaves characteristic features on surfaces, which make the mirrors not very good for imaging in 'visible' light. Instead, they are usually used in the more-tolerant infrared (e.g. for night-vision goggles).

In metre sizes, aluminium mirrors have normally been machined traditionally, then nickel-plated, as this is easier to polish. But nickel has inferior reflection properties to aluminium, so back to square-1! Worse, the nickel expands differently from aluminium, and the whole mirror can distort with temperature changes.

With that background, the project concerns two main avenues of investigation. The first tackles removing the features on diamond-turned mirrors, using computer-controlled polishing machines and robot platforms. The diamond turning will be performed using machines on-campus, with specialised diamond tools provided by the partner CFT Ltd. Then, polishing will proceed in Huddersfield's new laboratory at the STFC-Daresbury site, using highly specialised abrasive slurries from the partner company Kemet Ltd. The technology developed will be transferred to a defence company making optics, QioptiQ Ltd.

The second avenue is to develop methods to make bare aluminium mirrors in metre sizes, as needed by partner TMF Ltd. The idea is then to position Kemet as a potential supplier, by transferring technology and so upgrading their lapping and polishing facility.

In both cases, a key aspect missing from previous research is investigating the detailed interactions between process steps. The best surface in terms of the heights of errors, may not be best for polishing, because of how those errors are distributed over the surface. We believe the project will break new ground in considering this type of approach for both avenues above.

Publications

10 25 50
 
Description Collaboration with Institute of Astrophysics of the Canary Islands 
Organisation Institute of Astrophysics of the Canary Islands
Country Spain 
Sector Academic/University 
PI Contribution The contributions from PI's team: Instrument control and part of the software development in developing scanning long-wave optical test system (SLOTS) and software configurable optical test system(SCOTS)
Collaborator Contribution The contributions from IAC: Hardwares including Thermal IR camera, Server, camera optics, linear stage for SLOTS test. Theoretical understanding of SLOTS tests
Impact no output yet
Start Year 2021
 
Description Collaboration with National Central University, Taiwan 
Organisation National Central University Taiwan
Country Taiwan, Province of China 
Sector Academic/University 
PI Contribution Technology consultancy in ultra-precision processing
Collaborator Contribution Staff and machine time in polishing optical surfaces
Impact No output yet
Start Year 2022
 
Description Collaborative partnership with Contour Fine Tooling Ltd 
Organisation Contour Fine Tooling Ltd
Country United Kingdom 
Sector Private 
PI Contribution None up to now
Collaborator Contribution None up to now
Impact None up to now
Start Year 2020
 
Description Collaborative partnership with Optical Tools for Industry Ltd. 
Organisation Optical Tools for Industry
Country United Kingdom 
Sector Private 
PI Contribution 1. Data for sample machining
Collaborator Contribution 1. Staff and machine times for samples
Impact No outcome yet
Start Year 2020
 
Description Collaborative partnership with Qioptiq Ltd. 
Organisation Qioptiq Limited
Country United Kingdom 
Sector Private 
PI Contribution None up to now
Collaborator Contribution None up to now
Impact None up to now
Start Year 2020
 
Description Collaborative partnership with Thin Metal Films Ltd. 
Organisation Thin Metal Fims Ltd
Country United Kingdom 
Sector Private 
PI Contribution We (University of Huddersity Laboratory for Ultra-Precision Surfaces: UoH UPS) has made the following contributions: 1. Consultancy for processing large aperture metal mirrors 2. Conduct pioneering experiments on technology transfer
Collaborator Contribution Thin Metal Film ltd (TMF) has made the following contributions: 1. Large mirror sample for experiments
Impact No outcomes yet
Start Year 2020
 
Description Industrial Partnership with Kemet International Ltd. 
Organisation Kemet International
Country United Kingdom 
Sector Private 
PI Contribution We (University of Huddersfield Laboratory for Ultra-Precision Surfaces at Daresbury: UoH UPS) has set up a collaborative partnership with Kemet International Ltd. The contributions are listed below: 1. UoH UPS has requested polishing slurries for large aperture metal mirrors 2. UoH UPS has tested and provided feedback suggestions and results to Kemet
Collaborator Contribution 1. Kemet has developed new products that are following the specification of UoH UPS 2. Kemet agreed to deliver further products under UoH UPS specification
Impact We are working together to transfer the polishing technologies to all the industrial partners.
Start Year 2016
 
Title Software for testing large optical surfaces using deflectometry 
Description This software is still under development. 
Type Of Technology Physical Model/Kit 
Year Produced 2021 
Impact This software will enable the testing of large optical surfaces within our laboratory 
 
Title Swing Arm Profilometer 
Description This new surface metrology is under construction. 
Type Of Technology Systems, Materials & Instrumental Engineering 
Year Produced 2021 
Impact This equipment will enable us to measure large freeform optical surface