| This thesis is mainly concerned with the development of a profile measuring instrument, to work in the 1 meter plus diameter area of large optical production, with a resolution in the tens of nanometers region. Development of such an instrument also addresses an important area of optical testing which is concerned with the testing of complex and difficult optical surfaces, which cannot be tested with traditional optical test methods. The thesis starts with a historical review of profile measuring instrumentation, and continues to discuss the optical production and test facilities available at the Optical Science Laboratory, (OSL). A study of the optical specifications of 8 meter class telescope secondary mirrors has used to develop a specification of resolution and dynamic range leading to development of the instrumentation. The main part of the thesis discusses the development of a number of different instrument components. The three major components are discussed in this thesis. A new type of laser reference system, which uses a laser beam in free air, in combination with a custom designed actuator flexure and software control system, defines an absolute reference plane for measurement. A new type of interferometric measurement system, is used as a surface height measurement, as well as an axis position measurement system, to define measurement coordinates. The last area of instrument development, adressed by the thesis is the development of a low contact force surface probe system, based on a torsion wire. The thesis concludes with a series of system testing culminating in a test on a toroidal surface, which is classically difficult to test. The performance of the system is then reviewed against the specifications initially determined earlier in the thesis. In conclusion this thesis provides some ideas for future development and improvement of the instrument. |
