One of siderostat enclosures of the Palomar Testbed Interferometer, with the Palomar Observatory 5 m Hale telescope in the background.

Inside the Palomar Testbed Interferometer (PTI) beam combining building. Light from the two telescopes enters through the two white pipes shown, and is directed down the long tunnel to optical delay lines which move under computer control along precision tracks. Light from the delay lines is then reflected back toward the optical table in the center of the picture, which contains additional optics, and then is directed toward two beam combiner tables on either side of the picture.

Optical design embraces a number of technical capabilities, including design of: traditional refractive and reflective optical systems; non-traditional optical elements (e.g., active/actuated, holographic, diffractive and gradient index elements); optical materials & coatings; fiber and integrated optics elements and systems; and optomechanical mounts and benches.

Advanced optical interferometers, high contrast imaging systems and active/adaptive optical systems invariably employ several of the above capabilities. The Space Interferometry Mission in fact exercises all the above areas of optical design, using; traditional practices in the design of its beam compressor optics; non-traditional elements in its delay lines and picometer metrology gauges; carefully designed and implemented optical coatings to reliably achieve high reflectivity mirrors and low loss/reflection transmissive surfaces; fiberoptic lines to carry light from the laser source to each of the metrology gauge beam launchers; and a variety of low stress, temperature stable mounts and benches to establish and maintain alignment of the numerous optical elements.