Accelerometers are key sensors in many fields and applications such as precision metrology, gravimetry measurements, gravitational wave observatories, and navigation where position and attitude need to be determined accurately. A combination of six accelerometers provides all the necessary information to estimate position and orientation of a rigid body and thus serves as an inertial navigation system for autonomous navigation. Fusedsilica based mechanical resonators paired with laser interferometric read-outs enable compact high-accuracy accelerometers. In this talk, we will present a wide-band accelerometer based on a double resonator with two test masses of different sizes in a single frame. One of the resonators has a resonance frequency of about 50 Hz, while the other is optimized for lower frequencies and has a nominal frequency of about 10 Hz. The combination of the two resonators allows for excellent long-term precision while maintaining good measurement bandwidth. We will show the experimental characterization in air and in vacuum of the double-resonator using a heterodyne laser interferometer and a fiber interferometer and its expected performance as an inertial sensor.
In addition to achieving a desired freeform profile, ensuring a superb micro-roughness finish is a key factor for successful freeform optics manufacturing. We present a pseudorandom orbiting stroke-based postprocessing technique that maintains freeform optic forms, while improving small-scale surface quality. The full-aperture tool can avoid subaperture effects, and the small stroke pseudorandom tool path guarantees the match of freeform profiles while preventing the directionality of the final surface profiles. Three independent experimental studies are designed, conducted, and presented for a wide range of optics, including magnetorheological finishing-polished BK7 glass, single-point diamond turned (SPDT) poly(methyl methacrylate), and SPDT Al6061 optics. The comparison of direct measured maps on the initial and final smoothed optics verifies the form maintenance capability of the freeform optics postprocessing technology. Surface roughness measurement highlights improvements in local surface roughness and periodic toolmark errors left by the previous polishing method.
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