Tip-tilt mirror

The main characteristics which determine the performance of a wavefront corrector are the number of actuators, actuator stroke and the temporal response. The number of actuators will determine the maximum Strehl ratio which can be obtained with the AO system. The price of a deformable mirror is directly related to the number of actuators. The actuator stroke should be enough to compensate wavefront errors when the seeing is moderately poor. This can be derived from the Noll formula with ao = 1.03. For example, on a 10m telescope with ro = 0.05m at 0.5 m, the rms wavefront error is 6.7 /xm. The deformable mirror stroke should be a factor of at least three times this. It should also include some margin for correction of errors introduced by the telescope itself. The required stroke is too large for most types of deformable mirror, and it is common practice to off-load the tip-tilt component of the wave-front error to a separate tip-tilt mirror. The Noll coefficient a2 = 0.134 and... 

Mt. Wilson Observatory. The UnISIS excimer laser system is deployed on the 2.5 m telescope at Mt. Wilson Observatory (Thompson and Castle, 1992). A schematic of the system layout is shown in Fig. 11. The30W, 351 nm excimer laser is located in the coude room. The laser has a 20 ns pulse length, with a repetition rate of 167 or 333 Hz. The laser light is projected from the 2.5 m mirror and focused at 18 km. A fast gating scheme isolates the focused waist. A NGS is needed to guide a tip-tilt mirror. Even with relatively poor seeing, UnISIS has been able to correct a star to the diffraction limit. 

To overcome the effects associated with laser uplink, a quadrupole tip-tilt sensor on the AO bench is interfaced with the tip-tilt mirror on laser table... 

The effect of overall slope on the wavefront can be removed by re-centering the speckle image, and in most adaptive optics systems this is performed by a planar tip/tilt mirror (Roddier and Roddier, 1993). 

A two-axis tip-tilt mirror was designed and fabricated in the PolyMUMPS process as a student design project [12]. Here the mirror was not lifted out of plane as in the lambda router switch, so the maximum tilt angle was determined by the radius of the mirror, 100 pm, set by the dimensions of the optical fiber core that the switch was designed for, and the maximum sacrificial gap of 2.75 pm obtained... 

Figure 4.13 Two-axis tip-tilt mirror designed and fabricated as a student project in the PolyMUMPs process. (Image courtesy of Kuan-Fu Chen and Tung-Chien Chen, EE215 MEMS Design final project report, Spring 2007.)...

Kipp-spiegei m. tilting mirror oscillating mirror. -verrichtung, /. tipping device, tipper. 

The basic layout of a laser guided AO system is shown in Fig. 1. Implementation of LGS referencing requires the addition of a laser and launch telescope, plus one or more additional wavefront sensors (WFS), including a tip-tilt sensor. Multiple LGSs require additional lasers and launch systems, or a multiplexing scheme. Multi-conjugate AO (MCAO) requires additional deformable mirrors, operating in series, plus multiple WFSs. 

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