PI fast steering mirrors provide high-speed, high-precision beam steering using piezo or voice-coil drive technologies. Frictionless flexure guides enable fast response, high resolution and precise multi-axis motion for static and highly dynamic applications.
Available configurations range from single-axis scanners to multi-axis systems combining pitch, roll and piston motion in a single platform.
Applications free-space optical communication (FSOC), laser beam steering, scanning, optical dithering, image stabilization, vibration cancellation, laser welding, semiconductor manufacturing, astronomy, two-photon polymerization and medical technology.
Read Article: Design, Performance, and Tuning of Fast Steering Mirrors based on Piezo Drives and Flexure Guides
Tip/Tilt Mirrors for Precise & Highly Dynamic Beam Steering
Fast steering mirror design involves a trade-off between angular range, resolution and dynamic performance. The optimum solution depends on the beam-steering task – from wider-angle acquisition and coarse pointing to high-speed, high-precision tracking and stabilization.
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Fast Steering Mirrors for Free-Space Optical Communication (FSOC)
Fast steering mirrors provide the rapid, precise beam correction required to acquire, track and maintain free-space optical communication links.
PI has extensive experience in LEO optical communication, with thousands of fast steering mirrors already deployed in LEO applications.
Three platforms cover different combinations of angular range and dynamic performance:
- V-931 Fast Steering Mirror – voice-coil technology providing up to 140 mrad (8°) optical deflection, making it particularly suitable where a large steering range is required.
- S-335 Fast Steering Mirror – piezo-driven platform providing up to 70 mrad optical deflection with resolution down to the nanoradian range, combining relatively large angular travel with high precision.
- S-330 Fast Steering Mirror – high-speed piezo platform for applications requiring particularly fast, precise beam correction.
Beyond standard products, PI can adapt its proven piezo and voice-coil technologies to specific optical communication requirements, optimizing characteristics such as angular range, dynamics, mirror size and resolution.
These technologies support satellite-to-satellite, satellite-to-ground, ground-to-satellite and terrestrial optical communication.
Read the use case: Reliable Optical Communication in LEO Satellite Constellations →
Expert Insights on Fast Steering Mirrors for Free-Space Optical Communication
Expert Insights on Fast Steering Mirrors for Free-Space Optical Communication
Our podcast explores FSOC in LEO, focusing on the challenges of pointing, acquisition, and tracking (PAT) and the technologies that make optical links reliable.
S-330 Fast Tip/Tilt Steering Mirror
Mirrors up to 50mm
- Fixed orthogonal axes with a common pivot point
- To 20mrad optical beam deflection
- Up to 20nrad resolution
- Closed-loop for high linearity
S-310/14 Z-Actuator – Phase Shifter
With Aperture
- 6/14µm piston motion
- Sub-millisecond dynamics
- Sub-nanometer resolution
- Open loop
- 10mm aperture
S-224 Fast Steering Mirror
Compact, 4mrad
- Sub-microradian resolution
- Sub-millisecond response
- 4.4mrad optical beam deflection
- Closed-loop option
- Includes BK7 mirror
S-331 Tip/Tilt Mirror Platform
High Dynamics, for ½” Mirrors
- 10mrad optical deflection
- High dynamics: 0.8msec rise time
- PKM: single pivot point
- Closed-loop for high linearity
- Up to 50nrad resolution
S-330 Fast Tip/Tilt Steering Mirror
Mirrors up to 50mm
- Fixed orthogonal axes with a common pivot point
- To 20mrad optical beam deflection
- Up to 20nrad resolution
- Closed-loop for high linearity
S-340 Fast Tip/Tilt Steering Mirror
Mirrors up to 100mm
- Fixed orthogonal axes with a common pivot point
- 4mrad optical beam deflection
- Sub-microrad resolution
- Closed-loop for high linearity
S-335 Tip/Tilt Mirror Platform
Long Travel, Mirrors up 1”
- 70mrad optical beam deflection
- Up to 100nrad resolution
- Closed-loop for high linearity
- PKM = Equal dynamics for both axes
- ID chip for auto calibrate
V-931 Fast Steering Mirror Platform
Voice-Coil Driven, Mirrors to 1”
- 140mrad (8°) optical deflection
- <1 µrad resolution
- Closed-loop voice coil drives
- PKM = Equal dynamics for both axes
- 20msec step response
N-480 Tip/Tilt Mirror Mount
Piezo Motors, 16° Tilt Angle
- Kinematic mount
- High stability PiezoMike motors
- For 0.5", 1" or 2" optics
- 1µrad resolution
- Vacuum versions to 10-9 hPa
Custom Example - Astronomy
Ultra-Stable, Piezo Mirror Mount
- ±2° tip / tilt range with PiezoWalk motor
- <0.5 arcsec angular resolution
- <1 arcsec position repeatability
- <20 arcsec static position stability
- >110Hz resonant frequency
Custom Example – Low Profile
Dynamic tip/tilt mirror (ΘXΘY)
- ±100µrad tip/tilt range
- Low profile design
Talk to our engineers about your custom steering mirror project.
S-325 Tip/Tilt Piston Mirror Platform
For 1” Mirrors
- Tripod design: pitch, roll, piston
- 10mrad optical beam deflection
- 30µm piston (Z-motion)
- Closed-loop for high linearity
- PKM = Equal dynamics for All axes
S-316 Tip/Tilt/Piston Platform
With 10mm Aperture
- Tripod design: pitch, roll, piston
- 2.4mrad optical beam deflection
- 12µm piston (Z-motion)
- Closed-loop for high linearity
- PKM = Equal dynamics for all axes
P-612 Piezo-Z Stage
Compact Z Stage, Aperture
- 100µm motion
- Compact: 60x60x27mm
- For cost-sensitive applications
- <1 nanometer resolution
- PICMA® long-life piezo drives
P-541 Piezo-Z & Z-Tip-Tilt Stages
Low-Profile, 80x80mm Aperture
- 100µm linear travel, 1 mrad tip/tilt
- Lowest profile: 16.5mm
- <1 nanometer resolution
- Choice of feedback sensors
- 80x80mm aperture
P-528 Piezo Z & Z/Tip/Tilt Stages
Parallel Metrology
- 50, 100, 200µm Z-motion
- Up to 4 milliradian Z/tip/tilt
- Precision trajectory control
- Sub-nanometer resolution
- Parallel capacitive metrology
PI offers a large range of fast steering mirrors (FSM) from compact systems for laser beam steering up to large units used for astronomy.
Single-Axis Tilt Platforms
The most compact approach is based on a flexure guided platform driven by a single actuator. For differentially driven platforms see “Tip/Tilt System with Differential Piezo Drive (Tetrapod) and improved Thermal Stability” below.
The platform is supported by one flexure and pushed by one linear piezo actuator. The flexure determines the pivot point and doubles as a preload for the Piezo actuator.
Single flexure, single piezo actuator (PZT) tilt mirror platform design. Advantages are the straightforward construction, compact dimensions and low costs. If thermal angular stability over a large temperature range is a critical issue, a differential piezo actuator drive system is recommended (see below).
Multi-Axis Piezo Steering Mirrors
Multi-axis piezo tip/tilt mirror platforms from PI are based on parallel kinematics with a single moving platform for all directions of motion. The common platform approach achieves higher linearity than can be attained by cascading single-axis mirrors in succession (e.g. with most galvo scanners). The single platform design also avoids polarization rotation and is much more compact than a multi-stage approach.
High Dynamics and High Stability
Piezo-actuated tip/tilt mirrors and platforms are suitable both for highly dynamic operation, such as tracking, scanning, image stabilization, elimination of drift and vibration, and for static positioning of optical systems and samples.
Direct Drive and Motion Amplified Steering Mirrors
Piezo steering mirrors can provide very fast response times in the sub-millisecond range and resolutions down to nano radians. Direct-driven units achieve higher dynamics, while designs that take advantage of on internal flexure motion amplifiers provide for larger optical beam deflection up to 100 mrad.
Tip/Tilt/Piston System - Tripod Piezo Drive
The platform is driven by three piezo actuators that are located in 120° angles to one another. By means of coordinate transformation, the motion can be split among the different actuators. In addition to tilting, the platform may also be used linearly in Z direction (piston motion), useful for phase shifting and correcting optical path length differences.
![Piezo actuator arrangement of a tripod Z/tip/tilt mechanism. Tilt angles and piston motion (Z) are calculated with these formulas: θY = 2A-[(B+C)/2a]; θX = (B-C)/b; Z = (A+B+C)/3. A, B, C = linear displacement of the relevant piezo actuators.](/fileadmin/_processed_/f/0/csm_TripodSteeringMirror_dfcd7daf56.png "Piezo actuator arrangement of a tripod Z/tip/tilt mechanism")
Piezo actuator arrangement of a tripod Z/tip/tilt mechanism. Tilt angles and piston motion (Z) are calculated with these formulas:
θY = 2A-[(B+C)/2a]; θX = (B-C)/b; Z = (A+B+C)/3
A, B, C = linear displacement of the relevant piezo actuators
Tip/Tilt System with Differential Piezo Drive (Tetrapod) and improved Thermal Stability
The platform is driven by a total of four piezo actuators - two pairs with the θX and θY tilt axes arranged orthogonally removing the need for coordinate transformation. Each pair is controlled differentially, i.e. one actuator extends while the other one retracts by the same amount. The advantage of this approach is the improved thermal stability over a wider temperature range compared to a simpler, two actuator design. Just as the tripod, the differential version guarantees an optimum angular stability over a large temperature range. For position controlled versions, the differential evaluation of two sensors per axis provides an improved linearity and resolution.
Design principle of a differential piezo-actuator (PZT) steering mirror. This construction features two piezo linear actuators (operated in push/pull mode) per axis, supporting the platform. The case can be machined from one solid metal block with FEA (Finite Element Analysis) designed wire EDM (Electric Discharge Machining) cut flexures. The flexures provide for zero friction/stiction and excellent guiding accuracy. The differential design exhibits excellent angular stability over a wide temperature range - temperature changes only affect the vertical position of the platform (piston motion) and have no influence on the angular position. After the operating voltage is removed the platform returns to the center position.
Dynamics of Piezo Tip/Tilt Mirror Mechanisms
The dynamics and maximum operating frequency of a piezo tip/tilt system strongly depends on its mechanical stiffness and resonant frequency. The properties of amplifier, controller and closed-loop position sensor / circuit are also important. To estimate the effective resonant frequency of the system – a combination of platform and mirror – the moment of inertia of the mirror substrate needs to be calculated:
m = mirror weight [g]
IM = moment of inertia of a mirror [g × mm²]
L = mirror length orthogonally to tilt axis [mm]
H = mirror thickness [mm]
R = mirror radius [mm]
T = distance of pivot point to platform surface [mm]
The resonant frequency of the system is calculated with resonant frequency of the platform (see technical data) and moment of inertia of the mirror substrate using the following formula:
f' = resonant frequency of platform with mirror [Hz]
f0 = resonant frequency of platform without mirror [Hz]
I0 = moment of inertia of platform (see technical data) [g × mm²]
IM = moment of inertia of mirror [g × mm²]
Hexapods and Fast Steering Mirrors / Active Optics in Astronomical Telescopes
Resolution in large earthbound telescopes is limited by atmospheric turbulence and vibrations. During the last 35 years, PI has designed a number of large-aperture high bandwidth tip/tilt systems for image stabilization. Piezoelectrically driven active secondary mirrors can improve the effective resolution up to 1000% by correcting for these image shifts in real time, especially during long integrations with weak light sources.
Momentum Compensation
Due to the inertia of the large mirrors and the high accelerations required to correct for image fluctuations, significant forces can be induced in the telescope structure, causing unwanted vibrations. PI has developed momentum compensation systems integrated into the tip/tilt platforms which cancel undesirable vibrations and thus offer significantly better stabilization than uncompensated systems.
More Information on PI Precsion Motion Control Products in Astronomy
- PI wins Contract for Ultra-High Precision Positioning Actuators to Align Mirror Segments in the ELT Telescope
- Motorized Stages and S-330 Piezo Tip/Tilt in SOXS ESO Spectrograph Controlled by EtherCat Fieldbus
- P-845 Piezo Actuators / Control modeling of the fast-steering secondary mirror for GMT
- Ultra-Stable Mirror Mounts for LINC-NIRVANA High Resolution Imager
