25 September 2008 Design for test and manufacture of complex multi-component optical instruments
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Abstract
The KBand Multi-Object Spectrograph (KMOS) is an astronomical spectrograph designed for integration with the VLT (Very Large Telescope) and capable of surveying 24 independent fields. The IFU (Integral Field Unit) subsystem is a complex instrument with no less than 1080 optical surfaces. We focus here on the design of the manufacturing and test process for this subsystem. Design of this system is based on experience gained on similar complex optical systems, such as the NIRSPEC (Near Infra Red Spectrometer) IFU that will be integrated into the James Webb Space Telescope. Surfaces are produced in aluminium using a freeform diamond machine. Many surfaces are multi-faceted and of complex form. The requirement for 15 nm RMS form accuracy poses a significant challenge for the machining process. In particular, the large number of highly complex surfaces represents the most serious design challenge. Design of the part fixturing is critical to the consistent achievement of the required surface accuracy. Furthermore, efficient test procedures must be developed to characterise all surfaces. In recognition of this, particular emphasis is placed on the metrology of these components. Moreover, the volume of complex metrology involved offers a unique opportunity to fully characterise and optimise the manufacturing process.
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Stephen Rolt, C. Marc Dubbeldam, David J. Robertson, David A. Ryder, "Design for test and manufacture of complex multi-component optical instruments", Proc. SPIE 7102, Optical Fabrication, Testing, and Metrology III, 71020A (25 September 2008); doi: 10.1117/12.797680; https://doi.org/10.1117/12.797680
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