flexures for optics. outline brief overviews of micro flexures focus on macro flexures in this...
TRANSCRIPT
Outline
Brief overviews of micro flexures
Focus on macro flexures in this
tutorial
Beam bending
Symmetry -> precision
Degree of freedom (DOF)
Applications
Optical MEMS devices
Analog tip-tilt mirror
Resonant frequency of the comb drive depends on the ions hitting the pads
Motivation
Need nanometer precision to
manipulate light.
“Stage” and “driving mechanism”.
Sticktion is a problem encountered
with screw-type driving mechanisms.
Use piezoelectric, capacitive,
magnetic, photon,… to drive the
“stage”.
Symmetry in 2D
In-plane rotation Parasitic motion not di-
coupled As soon as the stage moved,
Fx developed some “local” y component
In-plane rotation minimized Parasitic motion reduced or
cancelled Less cross-talk
Parallelogram
In-plane rotation constrained Parasitic motion reduced As soon as the stage moved,
Fx developed some “local” y component
In-plane rotation constrained Parasitic motion further
reduced or cancelled Less cross-talk
Highly Symmetric XY Stages
Three different anchoring
geometries
Can be made into XYZ stages by adding the horizontal blades like
Pentaflex
Diaphragm Flexures
Provide out-of-plane (z,,) motions
Constrain the other in-plane (x,y,) motions
(Voice-coil, pressure sensor, flow control, MEMS devices)
Tip-tilt Flexures
Remove axial misalignment between two parts (shear),
but does not remove torque/moment.
In-plane 1D Flexure
Out-of-plane 1D flexure
In-plane 1D flexure
Symmetric dual 4-bar linkage eliminates Y errror
Bi-stable Flexure
Actuation force causes deflection
Open/close a valve at some pressure threshold;
on/off
Have negative stiffness in the unstable region
Physik Instrument
Piezoelectric drive + capacitive
sensor, feedback loop to actively
take out platform vibrations
Conclusion Use flexure to avoid sticksion. Use symmetry to cancel/de-couple
motions. In-plane vs out-of-plane configurations Flexures for translation, rotation, and any
combination of DOF (1-6 DOF). Dynamic range and linearity. Soft flexure -> low resonant frequency,
stiff flexure -> high actuation force. References: see FlexureForOptics.doc