Optique théorique et appliquée

The Homer test bench
The elements of Homer

The deformable mirrors

Table summarizing the characteristics of the mirrors

Type	Magnetic
Manufacturer	Floralis - Alpao
Number of actuators for DM1	88 (10x10) 52 in the pupil+a ring of guard actuators
Number of actuators for DM2	88 (10x10)
Layout of the mesh	square
Supply	+/- 0.25A
Inter-actuator distance	2.5 mm
Effective diameter of DM1	17.5 mm
Effective diameter of DM2	22.5 mm
Maximum mechanical displacement for DM1	+/- 8 microns
Maximum mechanical displacement for DM2	> +/- 5 microns
Mechanical coupling between 2 actuators for DM1	45%
Mechanical coupling between 2 actuators for DM2	65%

The HOMER deformable mirrors are magnetic membrane mirrors built by the ALPAO company. They have very attractive technical characteristics (high stroke, correct linearity, etc.) but still have a limited temporal dynamics and are sensitive to the acoustic and vibratory environment. They are very good components, particularly for laboratory testing for reasonable frequencies

Figure 1: Technology of the magnetic membrane mirror: a continuous membrane is deformed by the magnets, placed in front of the solenoids. Laplace forces are created when a current circulates in the solenoids and deforms the membrane (Courtesy to Alpao)

Figure 2: DM1 on its support. The power cable of the DM is connected at the back of the mirror

Figure 3: DM2 on its translation rail. The assembly in front is a return mirror. The power cables of the mirror are connected at the back of the DM.

Figure 4 shows the influence functions of DM2. Deformations are generated on the activation of each actuator. In this figure, we see the influence functions for each motor on the whole surface of DM2, positioned at the location of the motor. For this mirror, the coupling between the actuators is very important so the influence functions are very large: activating a motor has therefore an impact on the whole surface.

Figure 4: Influence function of DM2 when 50% of the maximum command is applied to the actuator.

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Optique théorique et appliquée

The Homer test bench The elements of Homer

The deformable mirrors

The Homer test bench
The elements of Homer