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Lens Potting

IP.com Disclosure Number: IPCOM000199664D
Publication Date: 2010-Sep-14
Document File: 4 page(s) / 302K

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Lens Alignment and Potting Description

Paul Griffiths

,

Julian Perry

26 January 2006

What it does

The arrangement allows for a lens to be aligned and fixed accurately relative to its mechanical housing. The design allows the lens to be held in position even when the housing is moved at high accelerations.

How it works

The lens assembly, for example a microscope objective lens, is connected to a lens nut by using a conventional lens mounting thread. The lens nut has machined into its outside diameter a coarse thread. The mechanical housing for the assembly has machined within it a coarse thread of identical pitch and form but larger nominal diameter.

The lens and nut is screwed into the mechanical housing on the coarse threads. The large difference in the nominal diameters allows sufficient play for the lens assembly to be positionally free. The lens may now be aligned to the intended optical axis by either mechanical or optical means, this being achieved by handling the lens assembly body directly.

Once the lens has been aligned into position, the gap between the coarse threads is filled with a suitable resin material, for example a two part epoxy material. The potting material may be inserted through feed holes by injection, with the material injected at a low level to ensure complete filling of the void between the threads. The lens nut also has features machined into the coarse thread to prevent rotation after the potting material has cured. The resin feed holes will prevent rotation of the potted material relative to the internal thread. After the filling, the resin is left to cure and harden.

After curing the material holds the lens nut rigidly in position as set earlier. However, the lens itself may still be removed on its own thread, either for replacement or for cleaning. This allows lenses to be changed or replaced, whilst offering positional repeatability as good as the repeatability of the lens thread. However, the overall system alignment has been achieved with a high degree of accuracy without the need for accurately machined mounting components. Furthermore, because the resin material need only be of small volume between the two coarse threads, for example only a few tenths of a millimetre thick, th...