Deformable Mirrors correct wavefronts for Astronomy and Laser Communications

Adaptive Optics systems utilize signals, such as from Laser Guide Stars [hyperlink to 1.3], to measure atmospheric optical disturbance for ground-based telescopes. Deformable Mirrors (DMs) are used to compensate for this disturbance for both astronomy and laser satellite communications to correct the vision of the systems in real time. Within the context of space-based astronomical programs, AO systems are also key to achieving high-contrast imaging capabilities (e.g. exoplanet science) and compensate imperfections of the optics due to manufacturing flaws, misalignments, gravitational release and stress during launching and deploying phases.

To overcome drawbacks of existing DM technologies, TNO has developed systems with the following design features:

• Electromagnetic actuators, high linearity, high force and high efficiency for power and volume
• Highly reliable due to lack of wear/aging, redundant actuator windings and serviceable parts
• Modular and scalable for various actuator counts, configurations and pitches in the range of 3-30 mm
• Adaptable for space environment, including cryogenic

For space applications a different set of requirements must also be met, such as operation in vacuum, radiation and launch. Within the framework of the ESA technology readiness program (TRP), TNO has been working with the University of Durham, RUAG and Airbus Toulouse to further develop its actuator technology that will also be used in an AO system aboard future space missions. TNO’s DM concept is based on variable reluctance actuators, which have several important advantages, including: high reliability, highly linear actuator response, high scalability to large aperture sizes and low power consumption.

The following specifications correspond to the prototype for the ESO TRP program and can be scaled up to larger values depending on the specific application:

• Mirror diameter: Ø160mm (TNO currently considering scalability to 3m)
• Number of actuators: 57 (extendable to several >1000)
• Actuator pitch: 18mm (scalable down to 4mm)
• Free Actuator stroke6: 40 μm (optical surface, total piston, wavefront is 2x this value)
• Inter-actuator stroke: 10 μm (optical surface, wavefront is 2x this value)
• Linearity: >99%
• Maximum Power dissipation <30mW per actuator

NEXT STEPS

We are planning to develop our deformable mirror technology to the 1, 2 and 3-meter scale. We are in continuous discussions with potential partners and users to further refine the concept and develop hardware specific to telescope and instrument needs. Initial design studies have already been performed in the range of 1 and 2 meter diameters.

Please contact us to discuss further developments.