Test+equipment

Test equipment used for making more recent optics.

Below is version R04 of the Bath Interferometer. Information on this is here:- https://datscope.wikispaces.com/Bath+Interferometer

Radius of curvature is done with a Focault tester and laser ranger. The optic is tested at the vertex to +/- 1.5mm. The ranger is mounted to the tester. 11.3mm is added to the reading due to it's position in the frame. The mirror vertex has a piece of tape on it to prevent confusion with the rear surface. The Foucault tester is par-focal with the interferometer so that they can be interchanged easily.



The Bath interferometer uses OpenFringe to analyse fringe data and create and error map. This image is then project down onto the mirror in the correct orientation. A large flat mirror is used to project the image. This is a standard 'rear surface' mirror mounted ointo flat double thickness MDF that is braced at the back to prevent twisting. This projects the image of the error map onto the surface to within +/- 2mm of error in round and diameter. Good enough for teh tools we use to correct. The image below shows teh PC projector with a PLOP image down onto teh new 1.0M aluminium table we have recently (Summer 2014) installed.

Image below shows the test set up with a 30 inch F3 inplace with the error map on top. Creium oxide in a darkened room shows up the surface very well.

Close up of the mirror that can be tilted and removed to open the garage door.

The test rig has a counterbalance to 'point' the mirror at the interferometer.

Close up of the projected PLOP imag on the new aluminium table.

Exmple image of the project image of a real error map at the start of figuring. This is of a 30 inch F3. High centre and edge with low 70%.



Handling equipment is required for large heavy optics. Loading and un-loading onto tehtabel or into and out of the mirror cell etc.

The hoist uses strops and a lifting plate with 3 x 'C' channel brackets tha hook under the mirror. These are covered in 3 layers of heat shrink. The mirror surface is protected with tissue as a precaution also.