We demonstrate the first 1050nm MEMS-eVCSEL co-packaged with a wideband amplifier to achieve over 70nm wavelength tuning at over 30mW of output power and SMSR greater than 40dB. Ophthalmic Optical Coherence Tomography Angiography (OCTA) images acquired at 800kHz A-scan rates showcase the telecom grade 14pin butterfly co-package as a path to low cost swept source OCT engines. Device design employs a strain-compensated InGaAs/GaAsP gain region disposed on a wideband fully oxidized GaAs/AlxOy back mirror capable of tuning ranges beyond 100nm. It has been suggested the wideband fully oxidized GaAs/AlxOy back mirror may pose risk to device lifetime reliability. However, over 9000hrs of lifetime testing validates reliability and projects device lifetimes exceed 20,000hrs under continuous use.
Endoscopic optical coherence tomography (OCT) angiography enables volumetric coregistered architectural and microvasculature imaging of the human gastrointestinal tract in vivo. In this talk, we will discuss technical advances and clinical gastroenterology applications with the endoscopic OCT angiography technique.
OCT angiography (OCTA) has recently garnered immense interest in clinical ophthalmology, permitting ocular vasculature to be viewed in exquisite detail, in vivo, and without the injection of exogenous dyes. However, commercial OCTA systems provide little information about actual erythrocyte speeds; instead, OCTA is typically used to visualize the presence and/or absence of vasculature. This is an important limitation because in many ocular diseases, including diabetic retinopathy (DR) and age-related macular degeneration (AMD), alterations in blood flow, but not necessarily only the presence or absence of vasculature, are thought to be important in understanding pathogenesis. To address this limitation, we have developed an algorithm, variable interscan time analysis (VISTA), which is capable of resolving different erythrocyte speeds. VISTA works by acquiring >2 repeated B-scans, and then computing multiple OCTA signals corresponding to different effective interscan times. The OCTA signals corresponding to different effective interscan times contain independent information about erythrocyte speed. In this study we provide a theoretical overview of VISTA, and investigate the utility of VISTA in studying blood flow alterations in ocular disease. OCTA-VISTA images of eyes with choroidal neovascularization, geographic atrophy, and diabetic retinopathy are presented.
Since the first demonstration of swept source optical coherence tomography (SS-OCT) imaging using widely tunable micro-electromechanical systems vertical cavity surface-emitting lasers (MEMS-VCSELs) in 2011, VCSEL-based SSOCT has advanced in both device and system performance. These advances include extension of MEMS-VCSEL center wavelength to both 1060nm and 1300nm, improved tuning range and tuning speed, new SS-OCT imaging modes, and demonstration of the first electrically pumped devices. Optically pumped devices have demonstrated continuous singlemode tuning range of 150nm at 1300nm and 122nm at 1060nm, representing a fractional tuning range of 11.5%, which is nearly a factor of 3 greater than the best reported MEMS-VCSEL tuning ranges prior to 2011. These tuning ranges have also been achieved with wavelength modulation rates of >500kHz, enabling >1 MHz axial scan rates. In addition, recent electrically pumped devices have exhibited 48.5nm continuous tuning range around 1060nm with 890kHz axial scan rate, representing a factor of two increase in tuning over previously reported electrically pumped MEMS-VCSELs in this wavelength range. New imaging modes enabled by optically pumped devices at 1060nm and 1300nm include full eye length imaging, pulsatile Doppler blood flow imaging, high-speed endoscopic imaging, and hand-held wide-field retinal imaging.
We developed an ultrahigh speed endoscopic swept source optical coherence tomography (OCT) system for clinical
gastroenterology using a vertical-cavity surface-emitting laser (VCSEL) and micromotor based imaging catheter, which
provided an imaging speed of 600 kHz axial scan rate and 8 μm axial resolution in tissue. The micromotor catheter was
3.2 mm in diameter and could be introduced through the 3.7 mm accessory port of an endoscope. Imaging was
performed at 400 frames per second with an 8 μm spot size using a pullback to generate volumetric data over 16 mm
with a pixel spacing of 5 μm in the longitudinal direction. Three-dimensional OCT (3D-OCT) imaging was performed in
patients with a cross section of pathologies undergoing standard upper and lower endoscopy at the Veterans Affairs
Boston Healthcare System (VABHS). Patients with Barrett’s esophagus, dysplasia, and inflammatory bowel disease
were imaged. The use of distally actuated imaging catheters allowed OCT imaging with more flexibility such as
volumetric imaging in the terminal ileum and the assessment of the hiatal hernia using retroflex imaging. The high
rotational stability of the micromotor enabled 3D volumetric imaging with micron scale volumetric accuracy for both en
face and cross-sectional imaging. The ability to perform 3D OCT imaging in the GI tract with microscopic accuracy
should enable a wide range of studies to investigate the ability of OCT to detect pathology as well as assess treatment
response.
In the last 2 years, the field of micro-electro-mechanical systems tunable vertical cavity surface-emitting lasers (MEMS-VCSELs)
has seen dramatic improvements in laser tuning range and tuning speed, along with expansion into unexplored
wavelength bands, enabling new applications. This paper describes the design and performance of high-speed ultra-broad
tuning range 1050nm and 1310nm MEMS-VCSELs for medical imaging and spectroscopy. Key results include
achievement of the first MEMS-VCSELs at 1050nm and 1310nm, with 100nm tuning demonstrated at 1050nm and
150nm tuning at shown at 1310nm. The latter result represents the widest tuning range of any MEMS-VCSEL at any
wavelength. Wide tuning range has been achieved in conjunction with high-speed wavelength scanning at rates beyond 1
MHz. These advances, coupled with recent demonstrations of very long MEMS-VCSEL dynamic coherence length,
have enabled advancements in both swept source optical coherence tomography (SS-OCT) and gas spectroscopy.
VCSEL-based SS-OCT at 1050nm has enabled human eye imaging from the anterior eye through retinal and choroid
layers using a single instrument for the first time. VCSEL-based SS-OCT at 1310nm has enabled real-time 3-D SS-OCT
imaging of large tissue volumes in endoscopic settings. The long coherence length of the VCSEL has also enabled, for
the first time, meter-scale SS-OCT applicable to industrial metrology. With respect to gas spectroscopy, narrow dynamic
line-width has allowed accurate high-speed measurement of multiple water vapor and HF absorption lines in the 1310nm
wavelength range, useful in gas thermometry of dynamic combustion engines.
Recent advances in swept-source / Fourier domain optical coherence tomography (SS-OCT) technology enable in vivo ultrahigh speed imaging, offering a promising technique for four-dimensional (4-D) imaging of the eye. Using an ultrahigh speed tunable vertical cavity surface emitting laser (VCSEL) light source based SS-OCT prototype system, we performed imaging of human eye dynamics in four different imaging modes: 1) Pupillary reaction to light at 200,000 axial scans per second and 9 μm resolution in tissue. 2) Anterior eye focusing dynamics at 100,000 axial scans per second and 9 μm resolution in tissue. 3) Tear film break up at 50,000 axial scans per second and 19 μm resolution in tissue. 4) Retinal blood flow at 800,000 axial scans per second and 12 μm resolution in tissue. The combination of tunable ultrahigh speeds and long coherence length of the VCSEL along with the outstanding roll-off performance of SS-OCT makes this technology an ideal tool for time-resolved volumetric imaging of the eye. Visualization and quantitative analysis of 4-D OCT data can potentially provide insight to functional and structural changes in the eye during disease progression. Ultrahigh speed imaging using SS-OCT promises to enable novel 4-D visualization of realtime dynamic processes of the human eye. Furthermore, this non-invasive imaging technology is a promising tool for research to characterize and understand a variety of visual functions.
KEYWORDS: Optical coherence tomography, Vertical cavity surface emitting lasers, Endoscopy, Imaging systems, Data acquisition, In vivo imaging, 3D acquisition, Colon, Image resolution, 3D image processing
We developed a micro-motor based miniature catheter with an outer diameter of 3mm for ultrahigh speed endoscopic optical coherence tomography (OCT) using vertical cavity surface-emitting laser (VCSEL) at a 1MHz axial scan rate. The micro-motor can rotate a micro-prism at 1,200-72,000rpm (corresponding to 20- 1,200fps) with less than 5V driving voltage to provide fast and stable scanning, which is not sensitive to the bending of the catheter. The side-viewing probe can be pulled back for a long distance to acquire three-dimensional (3D) dataset covering a large area on the specimen. VCSEL provides high a-line rate to support dense sampling under high frame rate operation. With the use of a C++ based high speed data acquisition (DAQ) system, in vivo three-dimensional OCT imaging in rabbit GI tract with 1.6mm depth range, 11μm axial resolution, 8μm lateral resolution, and frame rate of 400fps is demonstrated.
This paper demonstrates new wavelength swept light source technology, MEMS tunable VCSELs, for OCT imaging.
The VCSEL achieves a combination of ultrahigh sweep speeds, wide spectral tuning range, flexibility in sweep
trajectory, and extremely long coherence length, which cannot be simultaneously achieved with other technologies. A
second generation prototype VCSEL is optically pumped at 980nm and a low mass electrostatically tunable mirror
enables high speed wavelength tuning centered at ~1310nm with ~110nm of tunable bandwidth. Record coherence
length >100mm enables extremely long imaging range. By changing the drive waveform, a single 1310nm VCSEL was
driven to sweep at speeds from 100kHz to 1.2MHz axial scan rate with unidirectional and bidirectional high duty cycle
sweeps. We demonstrate long range and high resolution 1310nm OCT imaging of the human anterior eye at 100kHz
axial scan rate and imaging of biological samples at speeds of 60kHz - 1MHz. A first generation 1050nm device is
shown to sweep over 100nm. The results of this study suggest that MEMS based VCSEL swept light source technology
has unique performance characteristics and will be a critical technology for future ultrahigh speed and long depth range
OCT imaging.
MEMS tunable vertical cavity surface emitting laser (MEMS-VCSEL) development, over the past two decades, has
primarily focused on communications and spectroscopic applications. Because of the narrow line-width, single-mode
operation, monolithic fabrication, and high-speed capability of these devices, MEMS-VCSELs also present an attractive
optical source for emerging swept source optical coherence tomography (SSOCT) systems. In this paper, we describe the
design and performance of broadly tunable MEMS-VCSELs targeted for SSOCT, emphasizing 1310nm operation for
cancer and vascular imaging. We describe the VCSEL structure and fabrication, employing a fully oxidized
GaAs/AlxOy mirrors in conjunction with dielectric mirrors and InP-based multi-quantum well active regions. We also
describe the optimization of MEMs speed and frequency response for SSOCT. Key results include 1310 nm VCSELs
with >120nm dynamic tuning range and imaging rates near 1MHz, representing the widest VCSEL tuning range and
some of the fastest swept source imaging rates thus far obtained. We also describe how low-noise semiconductor optical
amplification boosts average optical power to the required levels, while maintaining superior OCT imaging quality and
state of the art system sensitivity. Finally, we present measured multi-centimeter dynamic coherence length, and discuss
the implications of VCSELs for OCT.
The effectiveness of speckle reduction using traditional frame averaging technique was limited in ultrahigh speed optical
coherence tomography (OCT). As the motion between repeated frames was very small, the speckle pattern of the frames
might be identical. This problem could be solved by averaging frames acquired at slightly different locations. The
optimized scan range depended on the spot size of the laser beam, the smoothness of the boundary, and the homogeneity
of the tissue. In this study we presented a method to average frames obtained within a narrow range along the slow-axis.
A swept-source OCT with 100,000 Hz axial scan rate was used to scan the retina in vivo. A series of narrow raster scans
(0-50 micron along the slow axis) were evaluated. Each scan contained 20 image frames evenly distributed in the scan
range. The imaging frame rate was 417 HZ. Only frames with high correlation after rigid registration were used in
averaging. The result showed that the contrast-to-noise ratio (CNR) increased with the scan range. But the best edge
reservation was obtained with 15 micron scan range. Thus, for ultrahigh speed OCT systems, averaging frames from a
narrow band along the slow-axis could achieve better speckle reduction than traditional frame averaging techniques.
We developed a piezoelectric transducer (PZT) based miniature catheter with an outer diameter of 3 mm for
ultrahigh speed endoscopic optical coherence tomography (OCT) using Fourier domain modelocked (FDML)
laser at a 480 kHz axial scan rate. The miniaturized PZT bender actuates a fiber to provide high scanning
speed. The side-viewing probe can be pulled back for a long distance to acquire three-dimensional (3D)
dataset covering a large area on the specimen. Operating with a high speed data acquisition (DAQ) system,
OCT imaging with 6.5 mm imaging range, 10 μm axial resolution, 20 μm lateral resolution, and frame rate of
480 frames per second (fps) is demonstrated.
Doppler OCT is a functional extension of OCT that provides information on flow in biological tissues. We present a
novel approach for total retinal blood flow assessment using ultrahigh speed Doppler OCT. A swept source / Fourier
domain OCT system at 1050 nm was used for 3D imaging of the human retina. The high axial scan rate of 200 kHz
allowed measuring the high flow velocities in the central retinal vessels. By analyzing en-face images extracted from 3D
Doppler data sets, absolute flow for single vessels as well as total retinal blood flow can be measured using a simple and
robust protocol.
We performed OCT imaging of the rat retina at 70,000 axial scans per second with ~3 μm axial resolution. Three-dimensional OCT (3D-OCT) data sets of the rat retina were acquired. The high speed and high density data sets enable improved en face visualization by reducing eye motion artifacts and improve Doppler OCT measurements. Minimal motion artifacts were visible and the OCT fundus images offer more precise registration of individual OCT images to retinal fundus features. Projection OCT fundus images show
features such as the nerve fiber layer, retinal capillary networks and choroidal vasculature. Doppler OCT images and quantitative measurements show pulsatility in retinal blood vessels. Doppler OCT provides noninvasive in vivo quantitative measurements of retinal blood flow properties and may benefit studies of diseases such as glaucoma and diabetic retinopathy. Ultrahigh speed imaging using ultrahigh resolution spectral / Fourier domain OCT promises to enable novel protocols for measuring small animal retinal
structure and retinal blood flow. This non-invasive imaging technology is a promising tool for monitoring disease progression in rat and mouse models to assess ocular disease pathogenesis and response to treatment.
The performance and imaging characteristics of ultrahigh speed ophthalmic optical coherence tomography (OCT) are investigated. In vivo imaging results are obtained at 850nm and 1050nm using different configurations of spectral and swept source / Fourier domain OCT. A spectral / Fourier domain instrument using a high speed
CMOS linescan camera with SLD light source centered at 850nm achieves speeds of ~91,000 axial scans per second with ~3μm axial resolution in tissue. A spectral / Fourier domain instrument using an InGaAs linescan camera with SLD light source centered at 1050nm achieves ~47,000 axial scans per second with ~7μm resolution in tissue. A swept source instrument using a novel wavelength swept laser light source centered at 1050nm achieves 100,000
axial scans per second. Retinal diseases seen in the clinical setting are imaged using the 91kHz 850nm CMOS camera and 47kHz 1050nm InGaAs camera based instruments to investigate the combined effects of varying speed, axial resolution, center wavelength, and instrument sensitivity on image quality. The novel 1050nm swept
source / Fourier domain instrument using a recently developed commercially available short cavity laser source images at 100,000 axial scans per second and is demonstrated in the normal retina. The dense 3D volumetric data sets obtained with ultrahigh speed OCT promise to improve reproducibility of quantitative measurements,
enabling early diagnosis as well as more sensitive assessment of disease progression and response to therapy.
Ultrahigh speed Spectral/Fourier domain ophthalmic OCT imaging at 70,000-312,500 axial scans per second is
demonstrated using a high speed CMOS camera at 800 nm. Comparative imaging results of the fovea illustrate the
performance tradeoffs between different imaging speeds and spectrometer configurations. Dense 3D volumetric
acquisitions show minimal motion artifacts when acquired at 250,000 axial scans per second. The porous structure of the
lamina cribrosa is shown in en face images extracted from a dense volumetric acquisition of the optical nerve head
acquired at 106, 382 axial scans per second. Rapid repeated volume imaging (4D-OCT) shows blood flow in retinal
capillaries. Boundaries of the capillary network are enhanced by motion contrast. 3D volumetric data acquired at 49,000
axial scans per second using an InGaAs camera at 1050 nm is compared to volumetric data acquired at 101, 010 axial
scans per second using a CMOS camera at 800nm. Averaging of adjacent cross sectional scans in the volume is shown to
increase contrast in the images and reduce speckle. The enhanced penetration of the 1050 nm compared to the 800 nm
OCT imaging system is shown. Dense 2D/3D data sets and 4D-OCT repeated volume imaging promise alternative
methods for diagnosis and monitoring of disease.
Ultrahigh speed spectral / Fourier domain optical coherence tomography (OCT) imaging using a CMOS line scan camera with acquisition rates of 70,000 - 312,500 axial scans per second is investigated. Several design configurations are presented to illustrate trade-offs between acquisition speed, sensitivity, resolution and sensitivity roll-off performance. We demonstrate: extended imaging range and improved sensitivity roll-off at 70,000 axial scans per second , high speed and ultrahigh resolution imaging at 106,382 axial scans per second, and ultrahigh speed imaging at 250,000-312,500 axial scans per second. Each configuration is characterized through optical testing and the trade-offs demonstrated with in vivo imaging of the fovea and optic disk in the human retina. OCT fundus images constructed from 3D-OCT data acquired at 250,000 axial scans per second have no noticeable discontinuity of retinal features and show that there are minimal motion artifacts. The fine structures of the lamina cribrosa can be seen. Long cross sectional scans are acquired at 70,000 axial scans per second for imaging large areas of the retina, including the fovea and optic disk. Rapid repeated imaging of a small volume (4D-OCT) enables time resolved visualization of the capillary network surrounding the INL and may show individual red blood cells. The results of this study suggest that high speed CMOS cameras can achieve a significant improvement in performance for ophthalmic imaging. This promises to have a powerful impact in clinical applications by improving early diagnosis, reproducibility of measurements and enabling more sensitive assessment of disease progression or response to therapy.
Due to the tradeoff between field of view and resolution, the ability of traditional optical telescopes to obtain
high-resolution wide field images is limited. This work presents a design for a scanning optical telescope that
can produce high resolution images over a wide field of view. This is accomplished by scanning one of the
telescope's optical elements. Inherent in such a design is the introduction of optical aberrations as off-axis
scanning occurs. The deformable mirror technology is implemented to adaptively correct these aberrations such
that on-axis resolution is achieved at off-axis scan angles. The optical design layout is optimized in software
to minimize on-axis wavefront aberrations. This paper presents results involving two deformable mirrors based
on different technologies: the AgilOptics mirror based on electrostatic actuators and the Imagine Optic mirror
based on electromagnetic actuators. Both mirrors are similar in size (about 15mm aperture), but the Imagine
Optic mirror has significantly larger actuator displacement, though at a higher cost. The static telescope design
has a field of view of 0.49-degrees which is increased to 20-degrees with the AgilOptics mirror and 40-degrees
with the Imagine Optic mirror.
We present a beam shaping method using deformable mirrors without using a target beam shape.
The key to the method is the use of an image-based metric on the quality of beam with respect to
the desired attributes of the super-Gaussian output beam. This technique iteratively adjusts the
deformable mirror shape to minimize the metric measured using a charge-coupled device camera.
Since the algorithm does not use a target beam for the optimization, it produces the resulting
super-Gaussian beam geometry consistent with the constraints imposed by the limited stroke and
the finite number of actuators of the deformable mirror.
Traditional solutions for long term imaging of living small biological specimens and microorganisms lack efficiency
due to computationally expensive algorithms, and field of view limitations in optical microscopes. This paper
describes a new algorithm that allows for real time tracking of multiple 1mm nematodes called Caenorhabditis
elegans with a novel optical microscope design called the Adaptive Scanning Optical Microscope (ASOM), developed
at the Center for Automation Technologies and Systems (CATS). Based on the real time experimentation,
an improved algorithm to track multiple worms in the presence of entanglements is generated. The stages of
this development start with an enhanced digital motion controller for the ASOM high speed scanning mirror
to suppress undesired vibrations that limit the system capacity to track multiple organisms. The second phase
is the integration of the ASOM apparatus, the high speed motion control, and a base tracking algorithm, all
which allows for rapid image acquisition to track multiple C. elegans in real time. The base algorithm was
developed at CATS and has been proven to track a single C. elegans in real time. Results demonstrating the
efficacy of the complete system are presented. Lastly, an enhanced tracking algorithm is described that shows
improved accuracy and robustness in tracking worms even when they become entangled. Taking into account
the unique ASOM design, individual segments of the worm are tracked throughout an image sequence, and a
mosaic pattern covering the entire worm is subsequently created. The algorithm takes advantage of geometric
and dynamic knowledge of the C. elegans such as size, and movement patterns. The enhanced algorithm is tested
on previously recorded footage. Simulated tracking experiments also illustrate the effectiveness of the enhanced
algorithm and are presented.
For a wide range of applications in biology, medicine, and
manufacturing, the small field of view associated with high-resolution
microscope systems poses a significant challenge in practice. To address
this limitation, a novel optical microscope uses a micromachined
MEMS deformable mirror working with a specially designed scan lens to
achieve a two-order-of-magnitude increase in the field of view area.
Called the adaptive scanning optical microscope ASOM, the deformable
mirror in the ASOM is an integral component of the optical system
and the static glass optical elements are specifically designed to match
the shape correcting capabilities of the deformable mirror itself. After
describing the design and operating principle of the ASOM, experimental
results from a low-cost prototype are presented. It is shown how an
image-based optimization method can be used to first calibrate the electrical
voltages to the MEMS deformable mirror. And once calibrated, we
show how the deformable mirror can be used in an open loop control
approach for very fast operation during run time. The methods for calibration
of a MEMS deformable mirror and basic control structures demonstrated
form the basis for a range of emerging adaptive-opticsenabled
technologies and instrumentation.
Over the last several years, MEMS deformable mirror technology has evolved from a specialized wavefront control
device used by only a few select research organizations to a low cost and high performance product that can now
be considered for inclusion in certain commercial machines and instrumentation. In a typical MEMS deformable
mirror, a membrane is suspended over a pattern of electrostatic actuators, with the possibility of additional
microstructures to affect the membrane movement. Because the electrostatic actuators in the MEMS deformable
mirrors can only pull on the membrane surface and because the shape of the membrane itself is determined
by the associated membrane mechanics, there are limitations and tradeoffs in the achievable shape corrections.
Our research seeks to clarify and define: (1) the actual wavefront correcting capabilities of the different MEMS
deformable mirror designs and (2) how to effectively design optical systems to best utilize this new technology.
After describing a finite element model of a three layer MEMS deformable mirror technology, a method for
integrating high fidelity models of deformable mirrors with commercial optical design and simulation software is
described. We then suggest a design methodology for both evaluating the performance of the deformable mirror
and optimizing the optical system itself to best utilize the MEMS deformable mirror such that the static optical
elements are tailored to the specific shape correcting capabilities of the deformable mirror. Simulated results are
presented of a defocus case study with more than 7 waves of correction, with the final results analyzed.
Imaging of small biological specimens and microorganisms that are living and moving is often hampered by a
traditional microscope's small field of view at high resolution. This paper discusses a new optical microscope
design, called the Adaptive Scanning Optical Microscope (ASOM), which uses a deformable mirror combined
with a custom scanner lens to effectively enlarge the field of view. Using a high speed scanning mirror in a
post-objective configuration, the ASOM captures a complete image (not a single point) at each scan position
and assembles image mosaics on the fly. Consequently, this microscope offers advantages when compared to
moving stage based approaches or confocal microscopes. Whereas previous work on imaging motile organisms
has primarily focused on tracking only one temporally challenging specimen at a time within a single field of view,
this microscope is well suited for tracking multiple moving organisms or monitoring larger organisms at both the
full animal and single cell levels simultaneously. In studies requiring manipulation, probing, or sensing, the ability
of the microscope to automatically monitor several regions of the specimen without agitating the workspace is
particularly advantageous. Using a low cost prototype of the ASOM, we illustrate the basic capabilities of the
instrument by imaging multiple living and freely moving Caenorhabditis elegans nematode worms. In addition to
transmitted, reflected, and epifluorescent illumination modes, we have also integrated an LED light source that
can be rapidly turned on and off in synchronization with the scanning to minimize unnecessary light exposure
to the specimens.
For a wide range of applications in biology, medicine, and manufacturing, the small field of view associated with
high resolution microscope systems poses a significant challenge in practice. This paper describes an optical
microscope design, called the Adaptive Scanning Optical Microscope (ASOM), which uses a MEMS deformable
mirror working with a specially designed scanning lens to achieve a greatly expanded field of view. Most adaptive
optics systems (e.g. telescopes and ophthalmology instruments) are designed to achieve near ideal performance
under nominal operating conditions and primarily use the adaptive optics element to compensate for a time
varying disturbance to the wavefront that is external to the optical system. In contrast to this approach,
the deformable mirror in the ASOM is an integral component of the optical system and the static (glass)
optical elements have been specifically designed to match the shape correcting capabilities of the deformable
mirror. Using a high speed steering mirror coordinated with the deformable mirror actuation voltages, the
ASOM operates by scanning over the workspace and should achieve diffraction limited imaging over a region
approximately two orders of magnitude larger in area than a traditional microscope design. With the rapid
scanning capabilities allowed by the high speed steering mirror and by acquiring a complete image during each
exposure, the ASOM offers advantages in dynamically reconfigurable and adaptable imaging with no agitation
to the workspace. After describing the design and operating principle of the ASOM, we present results from a
low cost ASOM prototype.
Dynamic optical systems that include active and adaptive optical elements allow the pursuit of scientific investigations,
military applications, and medical diagnostics that are well beyond the theoretical capabilities of a
purely static optical design. However, the design of such systems is particularly challenging because of the large
number of design variables, multiple operating configurations, and the need to coordinate different simulation
tools (e.g. optical ray tracing, finite element analysis, dynamic simulations, etc.) during the design and optimization
process. This paper presents a design methodology to facilitate the design and optimization of our
novel Adaptive Scanning Optical Microscope (ASOM), which includes a fast steering mirror (FSM), a custom
designed scanner lens, and a MEMS deformable mirror (DM) to effectively enlarge the field of view in optical
microscopy. An "all at once" formulation of the optimization problem using a traditional construction of the
merit function proved inadequate. Instead, our approach first partitions the design problem into manageable
sub-problems and uses the Collaborative Optimization (CO) framework to coordinate the system wide optimization
of the sub-problems while maintaining a physically consistent solution between the simulation codes. Next,
we demonstrate the efficacy of the approach by presenting two ASOM designs that were generated using this
methodology. The first design is based on high fidelity simulations and the second lower cost version has been
constructed and tested in our laboratory using a 32 actuator deformable mirror. We conclude by summarizing
our experiences and discussing how the approach could be generalized to other optical system design challenges.
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