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Ferrofluids can be used to make deformable mirrors having highly interesting characteristics (e.g., extremely large strokes and low costs). Until recently, such mirrors were thought to be restricted to corrections of frequencies lower than 10 Hz, thus limiting their usefulness. We present counterintuitive results that demonstrate that the limiting operational frequency can be increased by increasing the viscosity of the ferrofluid. We tested the response of ferrofluids having viscosities as high as 494 cP, finding that they could allow an adaptive optics correction frequency as high as 900 Hz. We also demonstrate that we can counter the amplitude loss due to the high viscosity by overdriving the actuators. The overdriving technique combines high current, short duration pulses with ordinary driving step functions to deform the mirror. The integration of a FDM in a complete closed-loop adaptive optics system running at about 500 Hz thus appears to be a realistic goal in the near future. OCIS codes: 220.1000, 220.1080, 230.3810.

We discuss a new type of deformable mirror made from nanoengineered reflective layers deposited onto liquids. The surfaces are shaped by heating with a laser. The response times of the deformed surfaces are slow (>1 s). Simplicity and low cost appear to be the main advantages of thermally deformable liquid mirrors. OCIS codes: 230.0230, 230.4040, 350.1260.

We describe a new technology for the fabrication of inexpensive high-quality mirrors. We begin by chemically producing a large number of metallic nanoparticles coated with organic ligands. The particles are then spread on a liquid substrate where they self-assemble to give optical quality reflective surfaces. Since liquid surfaces can be modified by a variety of means (e.g., rotation, electromagnetic fields), this opens the possibility of making a new class of versatile and inexpensive optical elements that can have complex shapes and that can be modified within short time scales. Interferometric measurements show optical quality surfaces. We have obtained reflectivity curves that show 80% peak reflectivities. We are confident that we can improve the reflectivity curves because theoretical models predict higher values. We expect nanoengineered liquid mirrors to be useful for scientific and engineering applications. The technology is interesting for large optics, such as large rotating parabolic mirrors, because of its low cost. Furthermore, because the surfaces of ferrofluids can be shaped with magnetic fields, one can generate complex, time-varying surfaces that are difficult to make with conventional techniques. OCIS codes: 000.3110, 240.6700, 260.3910, 350.1260.

We describe a device that applies the advantages of the space invariance of telecentric triangulation with the measurement of large objects (1 m(super 3)). Because the scan motion of the laser beam is decoupled from the physical transport of the sensor head, the fast scanning of large volumes becomes feasible. The device consists of a triangulation laser telemeter head that uses a large liquid primary mirror and an aspheric secondary mirror to realize the telecentric f-(theta) objective. We propose using liquid-mirror technology to make low-cost large objectives that have low f numbers, a diffraction-limited performance, and low scattering in the visible. This new optical system is useful for 3-D measurement. We discuss the optical configuration of the system and the performance of a laboratory prototype. The prototype has a standoff distance of 1.5 m, a telecentric scan as long as i m, a depth of view of I m, and a relative depth resolution of 0.5-1 mm.

We investigate a family of two-mirror correctors to compensate for the aberrations of a parabolic mirror observing at a large angle from the zenith. We constrain our designs to optical elements that can be built with currently available technology. The secondary and the tertiary mirrors are warped by Zernike polynomials, which we know can be generated with active vase mirrors. The performances of these corrector designs are usable for imagery.

We built and tested a 3.7-m-diameter liquid mirror that rotates on a ball bearing. Although the ball bearing is of a poor quality, the mirror is surprisingly good for one that comprises 1-mm-thick mercury layers. We found no evidence of the strong astigmatism that might have been expected from Coriolis forces. We did not detect effects of turbulence might or vibrations for thin mercury layers, illustrating the necessity of using thin layers: Large liquid mirrors would have had unacceptable optical qualities for layers much thicker than 2 mm. [C] 2000 Optical Society of America OCIS codes: 110.6770, 230.4040, 120.0120.