Deformable mirror

Deformable mirrors are used in combination with wavefront sensors and real-time control systems in adaptive optics.

[1] The shape of a DM can be controlled with a speed that is appropriate for compensation of dynamic aberrations present in the optical system.

It is very common to compare an arbitrary DM to an ideal device that can perfectly reproduce wavefront modes in the form of Zernike polynomials.

For predefined statistics of aberrations a deformable mirror with M actuators can be equivalent to an ideal Zernike corrector with N (usually N < M) degrees of freedom.

Influence function is the characteristic shape corresponding to the mirror response to the action of a single actuator.

All "modal" mirrors have large cross-coupling, which in fact is good as it secures the high quality of correction of smooth low-order optical aberrations that usually have the highest statistical weight.

Can vary from microseconds (MEMS and magnetics mirrors) to tens of seconds for thermally controlled DM's.

Hysteresis and creep are nonlinear actuation effects that decrease the precision of the response of the deformable mirror.

Each segment can move a small distance back and forth to approximate the average value of the wavefront over the patch area.

The development of robust methods to increase the contrast is key for the direct imaging and characterization of exoplanets.

Continuous faceplate concept mirrors with discrete actuators are formed by the front surface of a thin deformable membrane.

Depending on the design choices made, they can achieve unrivaled stroke - up to a hundred microns of deformation - or very high speed -

They enable a higher actuator count at a more cost-effective price allowing for accurate wave-front correction.

This new concept offers a potential alternative for low-cost, high stroke and large number of actuators deformable mirrors.