A reflective microelectromechanical mirror array was used to control the intensity distribution of a coherent beam that
was propagated through a strongly scattering medium. The controller modulated phase spatially in a plane upstream of
the scattering medium and monitored intensity spatially in a plane downstream of the medium. Optimization techniques
were used to maximize the intensity at a single point in the downstream plane. Intensity enhancement by factors of
several hundred were achieved within a few thousand iterations using a MEMS segmented deformable mirror (e.g. a
spatial light modulator) with 1020 independent segments. Experimental results are reported for alternate optimization
approaches and for optimization through dynamically translating scattering media.
In this paper we present an alignment methodology for a non-linear laser scanning fluorescence microscopic imaging
system integrated with a MEMS deformable mirror that is used to compensate microscope aberrations and improve
sample image quality. The procedure uses an accurate open-loop control mechanism of the MEMS DM, a high
resolution CMOS camera and a compact Shack-Hartmann wavefront sensor. The success of the indirect AO control
method used by the microscope to compensate aberrations requires careful alignment of the optical system, specifically
the DM conjugate planes in the scanning laser optical path. Considerations of this procedure are presented here, in
addition to an assessment of the final accuracy of the alignment task is presented, by verifying the pupil conjugation and
wavefront response. This method can also serve as a regular check-up of the system's performance and trouble-shoot for
system misalignment.
A prototype optical system for compact, high-speed zooming is described. The system is enabled by a pair of
MEMS deformable mirrors (DMs), and is capable of high-speed optical zoom without translation of components. We
describe experiments conducted with the zoom system integrated with an optical microscope, demonstrating 2.5× zoom
capability. Zoom is achieved by simultaneously adjusting focal lengths of the two DMs, which are inserted between an
infinity-corrected microscope objective and a tube lens. In addition to zoom, the test system is demonstrated to be
capable of automated fine focus control and adaptive aberration compensation. Image quality is measured using contrast
modulation, and performance of the system is quantified.
Improvements for open-loop control of MEMS deformable mirror for large-amplitude
wavefront control are presented. The improvements presented here relate to measurement
filtering, characterization methods, and controlling the true, non-differential shape of the
mirror. These improvements have led to increased accuracy over a wider variety of
deflection profiles including flattening the mirror and Zernike polynomials.
We present a model for MEMS deformable mirrors (DMs) that couples a 2-dimensional, linear 4th order partial
differential equation for the DM facesheet with linear spring models for the actuators. We estimate the
parameters in this model using the method of output least squares, and we demonstrate the effectiveness of this
approach with data from a 140-actuator MEMS test mirror produced at Boston University. A scheme for robust,
computationally efficient open-loop control, which is based on this model, is also presented.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.