For the LINC-NIRVANA (LN) project, MPIA requested an appropriate motorized mount for initial alignment
of two dichroic beam splitters in the instrument. These dichroic mirrors which reflect the visible light and
transmit the NIR are located close to the pupil plane are therefore very sensitive to tilt and flexure errors
which could be introduced to the wave-front sensor. Considering this the following high level specifications
were requested in a very tight operating envelope: range of adjustment tip and tilt ±2° around the major axis
of the elliptical mirror, resolution of adjustment <0.5 arcsec , position repeatability <1 arcsec, static position
stability within an elevation 0° up to 90° <20 arc seconds and a minimum eigenfrequency <110Hz.
To overcome the stroke limitation of single piezoelectric actuators walking drives are developed for long range travel application. This paper describes design concepts and products optimized for loads starting from 10N to 1kN and speed from 100μm/s to 20mm/s. Besides the micro stepping mode different driving concepts are presented to allow limited range high speed analogue motion with sub-nm resolution as well as ultra low constant velocity motion over the full range. The self locking design holds the mechanisms in position if not energized up to loads which exceed the max. driving force capability. Technology updates for ultrahigh vacuum, cryogenic, radiation or nonmagnetic environments will also be discussed.
This paper describes the development of the detector motion stage for the instrument SPHERE (Spectro-Polarimetric
High-contrast Exoplanet REsearch). The detector movement is necessary because the instrument SPHERE has
exceptional requirements on the flatfield accuracy: In order not to limit planetary detections, the photon response of
every pixel with respect to the detector's mean response must be known to an accuracy of 10<sup>-4</sup>. As only 10<sup>-3</sup> can be
reached by calibration procedures, detector dithering is essential to apply ~100 pixels at a single spatial detection area
and time-average the result to reduce the residual flatfield noise. We will explain the design of the unit including the
detector package and report on extensive cold and warm tests of individual actuators.
The novel, patented NEXLINE<sup>®</sup> drive actuator design combines long travel ranges (hundreds of millimeters) with high
stiffness and high resolution (better than 0.1 nm). Coordinated motion of shear and longitudinal piezo elements is what
allows NEXLINE<sup>®</sup> to break away from the limitations of conventional nanopositioning actuators. Motion is possible in
two different modes: a high resolution, high dynamics analogue mode, and a step mode with theoretically unlimited
travel range. The drive can always be brought to a condition with zero-voltage on the individual piezo elements and with
the full holding force available to provide nanometer stability, no matter where it is along its travel range. The
NEXLINE<sup>®</sup> stage is equipped with capacitive sensors for the closed loop mode. The piezo modules are specially
designed for cryogenic application.
This paper describes a high-force PZT-ceramic based linear actuator for long-travel, high resolution
applications. Different modes of operation offer high bandwidth dither, step and constant velocity slew motion.
The drive is self-locking and does not expend energy to hold a position. This development was originally
undertaken for applications in the semiconductor industry and mature serial production actuators are now
embedded in machinery to actively collimate heavy optic assemblies weighing 10's of kg in multiple axes with
This is a progress report on the development of the tip-tilt secondary mirror for the United Kingdom Infrared Telescope on Mauna Kea, Hawaii. The concept-- with emphasis on the electromechanical and optomechanical design--was published in an earlier paper. The reader is kindly requested to refer to the background information given there. Here, we present the electronics, system control and data handling considerations along with updated design drawings of the mirror and the combined piezoelectric/hexapod mirror mounts.
The European Space Organization (ESO) requested Physik Instrumente (PI) to develop a system to compensate for atmospherically induced image jitter in astronomical telescopes. The product, designated S-380 by PI, is a sophisticated adaptive optic system using closed loop piezoelectric actuators and momentum compensation to significantly improve telescope resolution during long integrations by correcting for image jitter in real time. Optimizing the design of this system involved solving several interdependent problems, including: (1) selection of the motion system, (2) arrangement of the pivot points and actuators, (3) momentum compensation, and (4) selection of the sensor system. This paper presents the trade-offs leading to final design of the S-380 system, some supporting technical analysis and ongoing efforts at PI to provide fast tilting platforms for larger mirrors.