In a MEMS mirror-based dual interference Fourier transform spectrometer (FTS) with a laser interferometer as the position sensing mechanism, making the two interferometers coaxial is very challenging. To solve this problem, a single interference MEMS FTS based on asynchronous calibration is designed. This single interference FTS uses a dichroic mirror to couple a laser beam and a broadband light beam into the same interferometer. Since the two optical beams share the same optical path, they will experience the same change when the position of any optical component along the optical path is adjusted. In data acquisition, the two interference signals are acquired asynchronously by the same InGaAs photodetector. This asynchronous calibration can effectively eliminate the laser coupling issue. According to the experimental results, compared with the dual interference spectrometer, the proposed spectrometer based on asynchronous calibration can improve the spectral repeatability and make the system simpler and lower power consumption.
Angiogenesis is essential for bone homeostasis and repair. Newly formed vessels convey osteogenic progenitors during bone regeneration. However, the lack of continuous and label-free visualization of the bone microvasculature has resulted in little understanding of the neovascular dynamics. Here, we take advantage of optical-resolution photoacoustic microscopy (ORPAM) for label-free, intravital, long-term observation of the bone vascular dynamics. We quantify the angiogenic effect of locally-applied vascular endothelial growth factor (VEGF) in the mouse tibia defect model. VEGF treatment increased the concentration of total hemoglobin, vascular branching, and vascular density, which increased bone formation within the defect. These data demonstrated ORPAM as a useful imaging tool understand bone angiogenesis, and revealed the effectiveness of locally delivered therapeutic agents with sufficient sensitivity, contributing to the studying the bone regeneration in the future.
In this paper, a new design of an electrothermal micromirror integrated with piezoresistive sensors is proposed. The micromirror is composed of four electrothermal bimorph actuators and four piezoresistive position sensors. In order to reduce the influence of temperature on piezoresistance, silicon dioxide can be used to thermally isolate the piezoresistive sensors from the silicon substrate. The optimized micromirror has a square mirror plate of 1800 * 1800 μm2 and a footprint of 4040 * 4040 μm2 , leading to a fill factor of 20%. The simulation results show that the optical fields of view of the micromirror are about 7° in the tilt and tip directions and the maximum piston displacement is close to 600 μm. The simulation results also show that the sensitivity and resolution of the piezoresistive sensors under a 3 V bias voltage are 2.88 mV/° and 0.4 μrad for the tip-tilt motion, respectively, and 0.056 mV/μm and 1.2 nm for the piston motion, respectively.
KEYWORDS: Microelectromechanical systems, Mirrors, Luminescence, Micromirrors, Photodynamic therapy, In vivo imaging, Prototyping, Tumors, Tissues, Surgery
Nowadays, the ability to diagnose brain tumors intraoperatively and to delineate their margins, as accurately as possible, is of primordial importance during surgery. However, the exact tumor boundaries and the infiltrated tumor cells outside its solid volume are difficult to be found by the surgeon due to the similar visual appearances especially at the margins, leading in many cases to poor surgical outcomes and a high risk of recurrences. To solve this issue, our group develop a two-photon multimodal endomicroscope to analyze the endogenous fluorescence of cerebral tissues in order to provide reliable informations intraoperatively on the tissues nature at cellular level. For that, and in order to implement the imaging modality in our endomicroscope, we launched a study based on an original miniaturized scanning system to be coupled with our endomicroscope. In this work, we characterize a scanning system prototype based on an electrothermally-actuated scanning micro-mirror. This type of scanning devices can provide a wide linear scan range at a low driving voltage and a high stable scanning speed along a straight scan line which help to acquire high-quality images.
Fiber scanning for forward-view imaging method has been widely used in biomedical imaging. It also attracts great interest in the fields of virtual and augmented reality. In this study, we propose a fiber scanner actuated by a robust Cu/W electrothermal MEMS stage which can be driven quasi-statically. The Cu/W MEMS stage is successfully fabricated after overcoming Cu oxidization. Compared to previous Al/SiO2 MEMS stages, this new Cu/W MEMS stage, which generates 0.7 mN forces at 1.8 V, offers three times more force. The MEMS stage can travel up to 53 μm at only 1.8 V. A single-mode fiber is assembled on the central platform of the MEMS stage to form a fiber scanner. The travel range can be amplified by four times.
Two-photon microscopy (TPM) has shown its great impact in studying neuronal activity of live animals. Commercial TPM systems require the animals under study to be restrained under the microscope and the 3D images are obtained typically by using bulky galvo scanning mirrors, which limits the flexibility of animal brain imaging to a large extent. To study freely moving animals, miniaturization of the optical scanning system is the key. In this work, a miniature TPM probe has been developed based on an electrothermal MEMS mirror that can be driven under low voltage. The MEMS mirror has an initial tilt angle after fabrication, and its footprint is 3 mm x 4 mm and reflective mirror plate is aluminumcoated with an equivalent diameter of 2.5 mm. This MEMS probe can be directly adapted to a commercial TPM system. In addition to the MEMS mirror for laser beam scanning, inside the MEMS probe head there are a fixed mirror to fold the laser beam and a high NA polymer lens for focusing. This miniature probe can realize an FOV of 3.5°, or a scanning range of 150 μm. This MEMS probe head is compact with a size of 8 mm x 16 mm, which can be further scaled down.
In this paper, we present the construction and preliminary experimental results of a MOEMS fiber-based integrated probe for endoscopic optical imaging of stomach tissue using a Swept-Source Optical Coherence Tomography (SSOCT). The probe consists of a Mirau micro-interferometer, combined with a GRIN lens collimator and a micromirror scanner. We describe the building blocks of the probe, especially the monolithically integrated Mirau mirointerferometer, fabricated by wafer-level vertical stacking and anodic bonding of Si/glass components, and the electrothermal 2-axis MEMS microscanner allowing large swept angles (up to ±22°) at high frequencies (> kHz) for low driving voltages (<20 V). The results of probe characterization, performed in a designed SS-OCT system, have confirmed proper operation of the probe. The B-scan images were obtained for central wavelength of λc = 840 nm, swept range of Dλ = 60 nm and A-scan frequency of fA= 110 kHz. The axial resolution of the probe is equal to 5.2 μm (determined by applied swept source), whereas the lateral resolution, measured by use of USAF test pattern, is 9.8 μm.
This paper reports an electrothermal MEMS mirror-based LiDAR system. The MEMS mirror has a low driving voltage of 9 V and a large mirror aperture of 2 mm in diameter. The working range of this system is 80 to 250 cm with a distance resolution of 7.2 cm. The complete LiDAR prototype can fit into a small volume of 100 mm×100 mm×60 mm with the weight under 100 g. The use of such a MEMS mirror can greatly reduce the weight, size and power of LiDAR modules, making it possible for small UAVs to carry LiDAR for accurate navigation.
Optical coherence tomography (OCT) can obtain light scattering properties with a high resolution, while photoacoustic
imaging (PAI) is ideal for mapping optical absorbers in biological tissues, and ultrasound (US) could penetrate deeply
into tissues and provide elastically structural information. It is attractive and challenging to integrate these three imaging
modalities into a miniature probe, through which, both optical absorption and scattering information of tissues as well as
deep-tissue structure can be obtained. Here, we present a novel side-view probe integrating PAI, OCT and US imaging
based on double-clad fiber which is used as a common optical path for PAI (light delivery) and OCT (light
delivery/detection), and a 40 MHz unfocused ultrasound transducer for PAI (photoacoustic detection) and US
(ultrasound transmission/receiving) with an overall diameter of 1.0 mm. Experiments were conducted to demonstrate the
capabilities of the integrated multimodal imaging probe, which is suitable for endoscopic imaging and intravascular
imaging.
A MEMS-based common-path endoscopic imaging probe for 3D swept-source optical coherence tomography (SSOCT) has been developed. The common path is achieved by setting the reference plane at the rear surface of the GRIN lens inside the probe. MEMS devices have the advantages of low cost, small size and fast speed, which are suitable for miniaturizing endoscopic probes. The aperture size of the two-axis MEMS mirror employed in this endoscopic probe is 1 mm by 1 mm and the footprint of the MEMS chip is 1.55 mm by 1.7 mm. The MEMS mirror achieves large two dimensional optical scan angles up to 34° at 4.0 V. The endoscopic probe using the MEMS mirror as the scan engine is only 4.0 mm in diameter. Additionally, an optimum length of the GRIN lens is established to remove the artifacts in the SSOCT images generated from the multiple interfaces inside the endoscopic imaging probe. The MEMS based commonpath probe demonstrates real time 3D OCT images of human finger with 10.6 μm axial resolution, 17.5 μm lateral resolution and 1.0 mm depth range at a frame rate of 50 frames per second.
A microelectromechanical system (MEMS) mirror based endoscopic swept-source optical coherence tomography (SS-OCT) system that can perform three-dimensional (3-D) imaging at high speed is reported. The key component enabling 3-D endoscopic imaging is a two-axis MEMS scanning mirror which has a 0.8×0.8 mm 2 mirror plate and a 1.6×1.4 mm 2 device footprint. The diameter of the endoscopic probe is only 3.5 mm. The imaging rate of the SS-OCT system is 50 frames/s . OCT images of both human suspicious oral leukoplakia tissue and normal buccal mucosa were taken in vivo and compared. The OCT imaging result agrees well with the histopathological analysis.
Optical coherence tomography (OCT) provides non-invasive cross-sectional imaging capability and
high resolution, but it has very limited applications inside human body because of the stringent size
requirements for accessing the internal organs. Micro-Electro-Mechanical Systems (MEMS) is an
emerging technology that can make devices with small size and fast speed. This paper reports the
design optimization of a MEMS mirror-based miniature OCT probe. The probe consists of three main
parts: a GRIN lens module (1.3 mm in diameter), a MEMS mirror (1.7 mm x 1.55 mm), and a stainless
steel mount. A special assembly holder is designed for easy placement of parts and accurate optical
alignment and real-time monitoring of optical alignment and electrical characteristics is also used to the
assembly process. Code V is used for the optical design and analysis. Simulation shows that the
changes of the spot size and focal length are within the acceptable range when the distance between the
optical fiber and the GRIN lens varies less than 0.1 mm. The fiber may tilt as much as 2.5 degrees
without any considerable change of the spot size and working distance. The maximum tolerance to the
lateral shift between the fiber and GRIN lens is about 0.1 mm.
We present the design and experimental results of a new MEMS-based endoscopic optical coherence tomography (OCT) probe. The uniqueness of this miniature OCT imaging probe is a two-axis MEMS mirror with through-silicon vias (TSVs) for interconnecting. The TSV interconnection enables ultracompact probe design, successfully reducing the probe size to only 2.6 mm in diameter. The MEMS mirror is actuated by an electrothermal actuator that is capable of scanning ±16° at only 3.6 V DC. Two-dimensional and three-dimensional OCT images of microspheres embedded in PDMS and acute rat brain tissue have been obtained with this miniature probe in a time-domain OCT system.
KEYWORDS: Optical coherence tomography, Microelectromechanical systems, Mirrors, Actuators, Doppler tomography, In vivo imaging, 3D image processing, Endoscopy, Ear, Cancer
Most cancers occur inside human body, so endoscopic high-resolution imaging modalities are required for early cancer
detection and surgical removal. This paper reports in vivo endoscopic 3D imaging based on optical coherence
tomography (OCT). Endoscopic imaging is enabled by integrating rapid-scanning MEMS mirror into a miniature
imaging probe. The MEMS mirror has an aperture size of 1 mm by 1 mm and a chip size of 2 mm by 2 mm. The optical
scan angle exceeds ±25 V at 6 Vdc, and thus large, constant-velocity, linear scan can be realized. The outer diameter of
the probe is only 5 mm. The axial resolution is about 10 μm and the imaging speed is 2.5 frames per second. Doppler
OCT imaging has also been demonstrated.
The paper reports 3D in vivo endoscopic imaging enabled by integrating rapid-scanning MEMS mirrors into an optical
coherence tomography (OCT) imaging probe. OCT provides high-resolution cross-sectional information suitable for in
vivo noninvasive early cancer diagnosis. However, conventional OCT systems are bulky and slow, and thus are difficult to
apply to internal organs where most cancers are originated. Microelectromechanical systems (MEMS) technology offers
the advantages of small size and fast speed and can be used to miniaturize optical imaging probes. The MEMS mirrors
have large aperture size (1 mm × 1 mm), large scan range (> ±25°) and low drive voltage (< 10 V). A 5.8mm-diameter
FEB-protected MEMS-OCT has been built and 3D OCT images of live mice have been successfully acquired with a
resolution of ~10μm and a frame rate of 2.5 frames per second.
Meniscal tear is one of the most common knee injuries leading to pain and discomfort. Partial and total meniscectomies
have been widely used to treat the avascular meniscal injuries in which tears do not heal spontaneously. However, the
meniscectomies would cause an alteration of the tibiofemoral contact mechanics resulting in progressive osteoarthritis
(OA). To mitigate the progression of OA, maximal preservation of meniscal tissue is recommended. The clinical
challenge is deciding which meniscal tears are amenable to repair and which part of damaged tissues should be removed.
Current diagnosis techniques such as arthroscopy and magnetic resonance imaging can provide macrostructural
information of menisci, but the microstructural changes that occur prior to the observable meniscal tears cannot be
identified by these techniques. Serving as a nondestructive optical biopsy, optical coherence tomography (OCT), a newly
developed imaging modality, can provide high resolution, cross-sectional images of tissues and has been shown its
capabilty in arthroscopic evaulation of articular cartilage. Our research was to demonstrate the potential of using OCT
for nondestructive characterization of the histopathology of different types of meniscal tears from clinical cases in dogs,
providing a fundamental understanding of the failure mechanism of meniscal tears. First, cross-sectional images of torn
canine menisci obtained from the OCT and scanning electronic microscopy (SEM) were be compared. By studying the
organization of collegan fibrils in torn menisci from the SEM images, the feasibility of using OCT to characterize the
organization of collegan fibrils was elucidated. Moreover, the crack size of meniscal tears was quantatitively measured
from the OCT images. Changes in the crack size of the tear may be useful for understanding the failure mechanism of
meniscal tears.
We report the design, fabrication, and measurements of a dual-reflective, single-crystal silicon-based micromirror that can perform circumferential scanning for endoscopic optical coherence tomography (EOCT). Full 360-deg optical scan angle (OSA) can be achieved by using a dual-reflective mirror with ±45-deg (or 90-deg) mechanical scan angle (MSA), where each reflective mirror surface contributes a 180-deg optical scanning. A novel surface- and bulk-combined micromachining process based on silicon on insulator (SOI) wafers is developed for fabricating the dual-reflective micromirror. The mirror flatness is maintained by the single-crystal-silicon device layer of SOI wafers, and aluminum is coated on both sides for reflection. A fabricated device demonstrated about half circumferential scanning range at resonance of 425 Hz. Other measured data include the radii of curvature, −129 mm (front surface) and 132 mm (back surface), and the reflectance, 86.3% (front surface) and 84.2% (back surface). This micromirror has the potential to realize full-circumferential-scanning EOCT imaging.
A reduced order thermal model of a one-dimensional (1D) electrothermally actuated micromirror device is reported.
Thermal bimorphs with integrated Pt resistors are used for generating the angular rotation. Neglecting the temperature
variation perpendicular to the length of the bimorphs, a 2D finite element thermal model with 4647 nodes is built. The
accuracy of the model is verified by comparing the simulation results with thermal imaging data. Using a Krylov
subspace based algorithm, a reduced order model is extracted from the finite element model. Results obtained from a
reduced model with order ≥ 5 agree well with finite element results. Hence, a reduced order thermal model that saves
computation time and resources without compromising the computation accuracy has been demonstrated.
This paper reports the design, fabrication and measurements of a dual-reflective, single-crystal silicon based micromirror
that can perform full circumferential scanning (FCS) for endoscopic optical coherence tomography (EOCT). In the
proposed FCS-EOCT probe, two optical fibers are used to deliver light beams to either surface of the micromirror, which
can rotate ±45° (or 90°) and thus a 180° optical scanning is obtained from each mirror surface, resulting in full
circumferential scans. A novel surface- and bulk-combined micromachining process based on SOI wafers is developed
for fabricating the dual reflective micromirror. The single-crystal-silicon device layer of SOI wafers is used for mirror
flatness, and Al is coated on both sides for high reflectivity. With one light beam delivered to each mirror surface, full
360° scans have been observed. Other measured data include the resonant frequency: 328Hz, radius of curvatures: - 124 mm (front surface) and 127 mm (back surface), and the reflectances: 81.3% (front surface) and 79.0% (back surface).
The development of miniaturized nonlinear optical microscopy or endoscopy is essential to complement the current imaging modalities for diagnosis and monitoring of cancers. We report on a nonlinear optical endoscope based on a double-clad photonic crystal fiber and a two-dimensional (2-D) microelectromechanical system mirror, enabling the three-dimensional (3-D) nonlinear optical imaging through in vitro gastrointestinal tract tissue and human breast cancer tissue with a penetration depth of approximately 100 µm and axial resolution of 10 µm. The 3-D high-resolution and high-sensitive imaging ability of the nonlinear optical endoscope facilitates the visualization of 3-D morphologic and cell nuclei arrangement within tissue, and therefore will be important for histopathologic interpretation without the need of tissue excision.
We report the recent technical improvements in our microelectromechanical systems (MEMS)-based spectral-domain endoscopic OCT (SDEOCT) and applications for in vivo bladder imaging diagnosis. With the technical advances in MEMS mirror fabrication and endoscopic light coupling methods, the new SDEOCT system is able to visualize morphological details of the urinary bladder with high image fidelity close to bench-top OCT (e.g., 10 µm/12 µm axial/lateral resolutions, >108 dB dynamic range) at a fourfold to eightfold improved frame rate. An in vivo animal study based on a porcine acute inflammation model following protamine sulfate instillation is performed to further evaluate the utility of SDEOCT system to delineate bladder morphology and inflammatory lesions as well as to detect subsurface blood flow. In addition, a preliminary clinical study is performed to identify the morphological features pertinent to bladder cancer diagnosis, including loss of boundary or image contrast between urothelium and the underlying layers, heterogeneous patterns in the cancerous urothelium, and margin between normal and bladder cancers. The results of a human study (91% sensitivity, 80% specificity) suggest that SDEOCT enables a high-resolution cross-sectional image of human bladder structures to detect transitional cell carcinomas (TCC); however, due to reduced imaging depth of SDEOCT in cancerous lesions, staging of bladder cancers may be limited to T1 to T2a (prior to muscle invasion).
A 5mm biophotonic catheter was conceived for optical coherence tomography (OCT) with collimation optics, an axicon
lens, and custom design imaging optics, yielding a 360 degree scan aimed at imaging within concave structures such as
lung lobes. In OCT a large depth of focus is necessary to image a thick sample with a constant high transverse
resolution. There are two approaches to achieving constant lateral resolution in OCT: Dynamic focusing or Bessel beam
forming. This paper focuses on imaging with Bessel beams. A Bessel beam can be generated in the sample arm of the
OCT interferometer when axicon optics is employed instead of a conventional focusing lens. We present a design for a
5mm catheter that combines an axicon lens with imaging optics and the coupling of a MEMS mirror attached to a
micromotor that allow 360 degree scanning with a resolution of about 5 microns across a depth of focus of about
1.2mm.
A translationally-scanning mirror is always desired for the axial scanning in optical coherence tomography (OCT),
but conventional scanners are bulky and have relatively slow scanning speed. This paper reports a micromirror that
has the potential to achieve both the scanning speed and range required by OCT. The large piston motion of the
micromirror is obtained using a large-vertical-displacement (LVD) microactuator. The device is fabricated using a
deep-reactive-ion-etch (DRIE) CMOS-MEMS process. A pair of electrothermal bimorph actuators is employed to
achieve tilt-free mirror plate and large piston motion. A linear voltage divider with a voltage ratio of 1:2.3 between
the two electrothermal actuators has been used to obtain static displacements up to 200 &mgr;m. The frequency response
of this device was obtained using a laser Doppler vibrometer, and resonant peaks were observed at 1.18 and 2.62
kHz. AC signals at 50 Hz with a voltage ratio of 1:1.2 were supplied to the actuators, and the maximum dynamic
piston motion was measured to be 26 &mgr;m. The decreasing amplitude over increasing frequency was caused by the
heat-sink effect of the mirror plate. A phase delay between the two actuators was also observed.
A biophotonics catheter was conceived with collimation optics, an axicon lens, and custom design imaging optics
yielding a 360 degree scan aimed at imaging within concave structures such as arteries and lung lobes. The large depth
of focus is necessary to image a long-depth-range sample with constant transverse resolution in optical coherence
tomography (OCT). There are two approaches to achieving constant invariant resolution in OCT: Dynamic focusing or
Bessel beam formation. This paper focuses on imaging with Bessel beams. The Bessel beams may be created with
axicon optics which can be used instead of a conventional focusing lens in the sample arm of the OCT interferometer.
In this paper we present the design of a 2mm catheter for optical coherence endoscopy with resolution of about 5
micron across a depth of focus of about 1.6mm. Importantly, we investigated the fabrication of a 800μm diameter
axicon lens and the associated lateral resolution obtained over a long depth range in our OCT system, compared to the
same OCT system using a conventional lens.
This paper summarizes the development of new 2D MEMS mirrors and the pertinent modification to improve OCT endoscopic catheter packaging suitable for in vivo imaging diagnosis of bladder cancers. Comparative study of the newly developed endocopic OCT versus the bench-top OCT is presented. Results of in vivo OCT cystoscopy based on a porcine acute inflammation model are presented to compare time-domain OCT and spectral-domain OCT for in vivo imaging. In addition, results of spectral-domain Doppler OCT are presented to image blood flow in the lamina propria of the bladder. The results of our in vivo animal study using the presented OCT endoscope are discussed for potential problems in the future clinical applications.
Fully-adiabatic (thermodynamically reversible) logic is one of the few promising approaches to low-power logic design. To maximize the system power-performance of an adiabatic circuit requires an ultra low-loss on-chip clock source, which can generate an output signal with a quasi-trapezoidal (flat-topped) voltage waveform. In this paper, we propose to use high-Q MEMS resonators to generate the custom waveform. The big challenge in the MEMS resonator design is that a non-sinusoidal (quasi-trapezoidal) waveform needs to be generated even though the resonator oscillates sinusoidally. Our solution is to customize the shape of the sensing comb fingers of the resonator, with the result that the sensing capacitance varies quasi-trapezoidally. The effective quality factor and the area-efficiency of the microstructure have been optimized so as to minimize the whole system’s power dissipation and cost at a given frequency. A resonator design with a 100 kHz resonant frequency based on a standard TSMC 0.35μm CMOS process has been fabricated. The resonator has an area of 300 μm by 160 μm with a thickness of 30 μm. Three-dimensional field simulation shows that the resonator generates a quasi-trapezoidal waveform when it operates at its resonance. An on-chip buffer is also designed for monitoring the waveform generated by the MEMS resonator. The post-CMOS fabrication process is compatible with standard CMOS processes. Thus the custom clock generator can be integrated with logic circuits on the same CMOS chip. The size of the MEMS resonator can be further reduced by design optimization and advances in micro/nano-fabrication technology.
We have developed an analytical model that describes the steady-state thermal behavior of a 1-D electrothermal bimorph MEMS micromirror. The steady-state 1-D heat transport equation is used to solve for the temperature distribution of the device upon actuation. Three models are developed using different thermal conditions on the device. The models consider heat dissipation from conduction and convection and the temperature dependence of the actuator electrical resistor. The temperature distribution equation of each model is analyzed to find critical thermal parameters such as the position of maximum temperature, maximum temperature, average temperature, and equivalent thermal resistance. The simplest model, called the Case 1 model, is used to develop an electrothermal lumped element model that uses a single thermal power source. In the Case 1 model, it is shown that a parameter called the “balancing factor” predicts where the maximum temperature is located, the distribution of power flow, and the division of thermal resistances. The analytical models are compared to FEM simulations and agree within 20% for all of the actuation ranges and thermal conditions tested.
Optical coherence tomography (OCT) is an emerging imaging technique that can provide high-resolution cross-sectional images of biological tissues. OCT has been used to detect various cancers including those in gastrointestinal tracts, bladder, and respiratory pathways. For in vivo imaging in visceral organs, small size and fast speed are essential, which can be achieved by using MEMS (Microelectromechanical systems) technology. In this paper, design and experimental results of a miniature endoscopic OCT imaging probe based on unique single-crystal silicon (SCS) MEMS micromirrors are reported. Several generations of one-dimensional (1D) micromirrors with a size of 1 mm by 1 mm have been fabricated. The resonant frequencies and radii of curvature of the micromirrors are about 0.5 kHz and 0.25 m, respectively. The packaged MEMS-OCT probe is 5 mm in diameter. About 15-μm axial resolutions, 20-μm transverse resolutions and 5-frames/s image rates are obtained.
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.