The compact and stable dual fiber optic refractive collimator is a device that takes laser light from two fiber optic cables, generating two beams of collimated light at increased diameters. This device is designed to be stable over a specific soak temperature range and maintain alignment through adverse vibration. Single or multiple beam configurations are possible with this design and the complexity goes linearly with beam quantity.
What makes this device noteworthy is the simplicity of design plus ease in assembly and alignment. A precision alignment fixture is used instead of cumbersome, built-in, multiple degree of freedom features such as adjustment screws and flexures. This allows the collimator itself to be quite simple, compact and thermally stable.
The dual collimator consists of a common housing, two fiber tip shuttle plugs allowing for adjustment in focus, and two laterally adjustable lens cells for beam alignment. The design has integral adhesive tack bonding features throughout and contains few parts keeping fabrication and alignment costs down.
This paper covers the requirements, design, manufacture, assembly and performance of this optical device. The collimator has utility in precision interferometry. A patent has been filed.
The Space Interferometry Mission (SIM), planned for launch in 2009, will measure the positions of celestial objects to an unprecedented accuracy of 4.0 microarcseconds. In order to achieve this accuracy, which represents an improvement of almost two orders of magnitude over previous astrometric measurements, a ten-meter baseline interferometer will be flown in space. NASA challenges JPL and its industrial partners, Lockheed Martin and TRW, to develop an affordable mission. This challenge will be met using a combination of existing designs and new technology. Performance and affordability must be balanced with a cost-conscious Systems Engineering approach to design and implementation trades. This paper focuses on the Lockheed Martin-led Starlight (STL) and Metrology (MET) subsystems within the main instrument of SIM. Starlight is collected by 35cm diameter telescopes to form fringes on detectors. To achieve the stated accuracy, the position of these white-light fringes must be measured to 10-9 of a wavelength of visible light. The STL Subsystem consists of siderostats, telescopes, fast steering mirrors, roof mirrors, optical delay lines and beam combiners. The MET Subsystem is used to measure very precisely the locations of the siderostats with respect to one another as well as to measure the distance traveled by starlight from the siderostat mirrors and reference corner cubes through the system to a point very close to the detectors inside the beam combiners. The MET subsystem consists of beam launchers, double and triple corner cubes, and a laser distribution system.
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