Abstract

We have designed and built an electrostatically deformable membrane mirror with simple bias and driver electronics to evaluate its suitability for a curvature-sensing adaptive optics system. It has a 100-mm-diameter aluminized nitrocellulose membrane, with 31 actuators arranged concentrically. The unit operates at atmospheric pressure with a high bias voltage applied to the membrane. The high-voltage electronics are contained within the mirror housing for safety reasons. An entrance window reduces the effects of air-coupled vibration. Details of the device and design rationale are presented. With a proper bias, the unit can provide low-order (including tip–tilt) wave-front correction.

© 1998 Optical Society of America

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References

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  1. R. Grosso, M. Yellin, “The membrane mirror as an adaptive optical element,” J. Opt. Soc. Am. 67, 399–406 (1977).
    [CrossRef]
  2. R. Centamore, A. Wirth, “High bias membrane mirror,” in Active and Adaptive Optical Components, M. A. Ealey, ed., Proc. SPIE1543, 128–132 (1991).
    [CrossRef]
  3. H. Takami, M. Iye, “Membrane deformable mirror for SUBARU adaptive optics,” in Adaptive Optics in Astronomy, M. A. Ealey, F. Merkle, eds., Proc. SPIE2201, 762–767 (1994).
    [CrossRef]
  4. B. Carnahan, H. Luther, J. Wilkes, Applied Numerical Methods, (Wiley, New York, 1969), pp. 482–485.

1977 (1)

Carnahan, B.

B. Carnahan, H. Luther, J. Wilkes, Applied Numerical Methods, (Wiley, New York, 1969), pp. 482–485.

Centamore, R.

R. Centamore, A. Wirth, “High bias membrane mirror,” in Active and Adaptive Optical Components, M. A. Ealey, ed., Proc. SPIE1543, 128–132 (1991).
[CrossRef]

Grosso, R.

Iye, M.

H. Takami, M. Iye, “Membrane deformable mirror for SUBARU adaptive optics,” in Adaptive Optics in Astronomy, M. A. Ealey, F. Merkle, eds., Proc. SPIE2201, 762–767 (1994).
[CrossRef]

Luther, H.

B. Carnahan, H. Luther, J. Wilkes, Applied Numerical Methods, (Wiley, New York, 1969), pp. 482–485.

Takami, H.

H. Takami, M. Iye, “Membrane deformable mirror for SUBARU adaptive optics,” in Adaptive Optics in Astronomy, M. A. Ealey, F. Merkle, eds., Proc. SPIE2201, 762–767 (1994).
[CrossRef]

Wilkes, J.

B. Carnahan, H. Luther, J. Wilkes, Applied Numerical Methods, (Wiley, New York, 1969), pp. 482–485.

Wirth, A.

R. Centamore, A. Wirth, “High bias membrane mirror,” in Active and Adaptive Optical Components, M. A. Ealey, ed., Proc. SPIE1543, 128–132 (1991).
[CrossRef]

Yellin, M.

J. Opt. Soc. Am. (1)

Other (3)

R. Centamore, A. Wirth, “High bias membrane mirror,” in Active and Adaptive Optical Components, M. A. Ealey, ed., Proc. SPIE1543, 128–132 (1991).
[CrossRef]

H. Takami, M. Iye, “Membrane deformable mirror for SUBARU adaptive optics,” in Adaptive Optics in Astronomy, M. A. Ealey, F. Merkle, eds., Proc. SPIE2201, 762–767 (1994).
[CrossRef]

B. Carnahan, H. Luther, J. Wilkes, Applied Numerical Methods, (Wiley, New York, 1969), pp. 482–485.

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Figures (12)

Fig. 1
Fig. 1

Photographs of the membrane mirror show the simple structure of the device: (a) front view showing the reflecting surface, visible through the entrance window; (b) back view showing the bias electronics (which generate up to 300 V) contained within the mirror housing to minimize any hazard.

Fig. 2
Fig. 2

Membrane-mirror structure. The 100-mm-diameter membrane is suspended 390 μm above the electrode array by a three-point spacer arrangement. A second set of spacers supports the entrance window. Connecting wires from the internal circuit board to the electrode array are not shown. Overall the mirror is 14 cm in diameter by 6.5 cm deep.

Fig. 3
Fig. 3

Electrode array and reflecting membrane. The electrode array consists of 31 actuators, arranged concentrically on a machined Macor ceramic substrate. The reflecting surface is an aluminized nitrocellulose membrane, 100 mm in diameter by 2.5 μm thick, stretched flat and bonded to an aluminum tension ring.

Fig. 4
Fig. 4

Electrode array schematic. The beam diameter on the mirror is 42 mm. The boundary actuators outside the beam area provide tip–tilt response. The electrodes inside the beam area can be ganged together to form different actuator patterns.

Fig. 5
Fig. 5

Actuator driver amplifier schematic. The circuit features a wide-output-voltage swing, high-output impedance for short-circuit protection, and a variable reference (VREF) input to accommodate a wide variety of digital-to-analog converters.

Fig. 6
Fig. 6

Tilt simulation. Contours are at 0.25 μm. The static parabolic shape of the membrane has been removed, and the actuator pattern has been superimposed for reference. The outer contour is the edge of the membrane. Tilt actuator voltages are applied to the outer electrode ring only. For this simulation, the tilt signal is ΔV = 50 sin θ, where θ is the angle to the center of each boundary actuator.

Fig. 7
Fig. 7

Membrane surface profile. The membrane surface is smoothly tilted within the actuated area.

Fig. 8
Fig. 8

Off-axis actuator response. The membrane-surface response is simulated for an off-axis actuator voltage of 50 V (with the static parabolic shape removed and actuator pattern superimposed). The contour lines are 0.25 μm apart.

Fig. 9
Fig. 9

Membrane-surface interferogram as measured with a Zygo interferometer at bias voltage V 0 = 200 V. The slight asymmetry and reflection are due to the entrance window.

Fig. 10
Fig. 10

Membrane-surface simulation. This numerically simulated contour plot shows the membrane surface, with bias and spacing values corresponding to the mirror used for the interferogram.

Fig. 11
Fig. 11

Optical arrangement used to determine tip–tilt dynamic range and step response time, consisting of an illuminated pinhole (PH), the membrane mirror (MM), an f = 1000 mm lens (L1), flat mirror (M1), and CCD sensor (WFS). The setup fits comfortably on an optical table.

Fig. 12
Fig. 12

CCD streak-mode images illustrating the membrane mirror tip–tilt step response. The applied tilt was ±20 arc sec and response time was approximately 10 ms. Each row of the CCD is read out in 1.25 ms.

Tables (1)

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Table 1 Membrane-Mirror and Electronics Specifications

Equations (6)

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2 z = 0 Tl 0 2   V 2 ,
2 z = 0 Tl 0 2 · V 0 2 + 2 V 0 Δ V ,
z r = 0 4 Tl 0 2 V 2 r 2 - V 0 2 r a 2 1 - 2   ln r a r f - V 2 - V 0 2 r p 2 1 - 2   ln r p r f r < r p 0 4 Tl 0 2 V 0 2 r 2 + 2 V 2 - V 0 2 r p 2 ln r r f - V 0 2 r a 2 1 - 2   ln r a r f r p < r < r a , 0 2 Tl 0 2 V 2 - V 0 2 r p 2 + V 0 2 r a 2 ln r r f r a < r < r f ,
f = Tl 0 2 0 V 0 2 ,
2 z Δ V = 2 0 V 0 Tl 0 2 ,
Δ z p Δ V = 0 V 0 2 Tl 0 2   r p 2 1 - 2   ln r p r f ,

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