We have demonstrated a new type of near-field microscope that uses an add-on lens, called a solid immersion lens, to a real-time Nipkow disk type of confocal scanning optical microscope. Using this microscope, a factor of two improvement in the edge response over a confocal microscope has been observed along with excellent images of a grating with 100 nm strips and spaces. This microscope operates in reflection and gives real-time images.

In this paper we consider the coupling of energy from electromagnetic waves through an electrically small aperture into a tapered metallic probe. An understanding of propagation through an aperture is essential if subwavelength resolution near-field studies of diffraction patterns are to be performed. Small-hole coupling theory is used to determine the total power transmitted into a perfectly conduction conical waveguide that approximates a tapered probe. It is found that along with the size of the coupling aperture, the most significant factor in determining the transmitted power is the radius of the waveguide at the point of coupling.

Near-field microscopy techniques are ideally suited for the determination of optical electromagnetic field structures with high spatial resolution. In this paper we report some preliminary results of our experiments on the near-field diffraction by a straight-edge and on the fields emanating from a single mode optical fiber. It is suggested that near-field techniques might provide an excellent approach to characterizing the properties of optical fibers.

We have integrated silicon micromachining techniques with piezoelectric thin film deposition to make a near-field acoustic microscope. A piezoelectric zinc oxide (ZnO) transducer is deposited on a substrate of 7740 glass. A sharp tip is formed in a silicon wafer which is anodically bonded to the glass substrate. A sample is attached to substrate of glass with a receiving ZnO transducer. The transducer on the tip excites an ultrasonic beam which passes from the tip to the sample and is detected by the receiving transducer. A feedback signal is generated to keep the transmitted amplitude constant as a sample is raster scanned. The feedback signal is applied to a tube scanner and is also used to modulate the intensity of a display monitor. We find that the instrument has a vertical height sensitivity of about 20 angstroms, and a lateral resolution of better than 800 angstroms.

The application of the STM and AFM techniques to imaging of biomolecules is reviewed. It is shown that in order to image poorly conductive molecules of nanometer dimensions, the STM has to be operated at high gap resistances in the 1012 ohm range. The correlation between forces and currents between tip and surface is investigated in model organic films of alkylsiloxanes on SiO2/Si(100) surfaces. The application of the AFM in the attractive and repulsive modes is also reviewed.

The focus of this paper is on the principal means of realizing a metric appropriate for atomic scale metrology. These are evaluated to determine the systematic uncertainties involved in relating sensed displacements to the international standard of length.

On the STS-32 Space Shuttle mission, a flight experiment provided an understanding of the effects of the environment on the long duration exposure facility (LDEF) from rendezvous with the shuttle until removal from the payload bay at the Orbiter Processing Facility (OPF) at NASA/KSC. The interim operational contamination monitor (IOCM) is an attached shuttle payload that has been used on two earlier flights (STS 51C and STS 28) to quantify the contamination deposited during the course of the missions. The IOCM can characterize by direct measurement the deposition of molecular and particulate contamination during any phase of flight, i.e., prelaunch, ascent, on-orbit operations, descent, and ferry flight of the shuttle. Measurements are made continually during these periods. Two types of particulate collection sensors are employed in order to avoid efficiency of collection uncertainties. In addition to these principal measurements, the IOCM actively measures the optical property changes of thermal control surfaces by calorimetry, the flux of the ambient atomic oxygen environment, the incident solar flux, and the absolute ambient pressure in the payload bay. The IOCM also provides a structure and sample holders for the exposure of passive material samples to the space environment, e.g., thermal cycling, atomic oxygen, and micrometeoroids and/or orbital debris, etc. One of the more salient results from the STS-32 flight suggests that the LDEF emitted a large source of contamination (mainly particulates) after berthing into the shuttle. The source emission rate of LDEF averaged 2.5 X 10-12 gr/cm2-sec for a period of eighty hours following berthing, falling off to a rate of 4.1 X 10-13 gr/cm2-sec just prior to re-entry. Post flight obscuration ratios on IOCM surfaces were measured at 2.4 percent. An atomic force microscope (AFM) was used to perform post-flight characterization of the IOCM sensors. The AFM is a new instrument capable of ultra high (atomic) resolution without coating the surface or exposing it to vacuum. This paper discusses the results observed by the IOCM during the retrieval of the LDEF, the operational capabilities of AFM, and the unique results acquired in assessing the data.

Atomic force microscopy was used to determine in situ the nanometer-scale morphological changes that occur on dielectric optical coatings as a result of laser-induced damage. The optical film studied was a highly reflective dielectric multilayer mirror (HR) consisting of many alternating HfO2 and SiO2 layers of quarter-wave thickness at 1.06 micrometers . The top layer was a (lambda) /2 SiO2 overcoat. Laser beam specifications were: 1.06 micrometers wavelength, 8 ns pulselength, and 110 micrometers to 300 micrometers beam diameter. The laser fluence was determined by beam profiling and total energy measurements. The maximum scan-range of the AFM was 80 micrometers . A survey of the as-deposited surface shows mostly hillocks of approximately 200 nm width and 10 nm height. Comparison of this hillock structure to that of a single layer of SiO2 and a surface layer of HfO2 was made. Irregularities (i.e., defects) on the surface of the HR consisted of micrometer-scale domes, and occasional craters, of micrometer planar dimension and depth extending over many layers. Three types of coating defects were identified which could be related to the classic nodule-type coating defect. Nodule defects were found to be easily ejected from the coating surface by laser illumination, leaving craters from which further damage would propagate. After laser damage with fluences above 30 J/cm2 the hillocks coalesced into structures with heights and widths 5 - 10 times that of the as-deposited film. A pattern of concentric surface distortions (ripples or cracks) appeared at higher fluences, in some cases following the full circumference of the beam.

Measurement of impurity dopant density in silicon with lateral resolution on the 100 nm scale has been demonstrated with the scanning capacitance microscope (SCM). This approach is based on the measurement of local capacitance changes between a 50 nm tip and semiconductor surface as the voltage bias is changed and/or the tip is scanned laterally across the surface. Capacitance versus voltage measurements provide a means to quantitatively determine local dopant density. We describe the scanning capacitance microscope and its application to dopant density measurements in semiconductors. We review the application of SCM to the measurement of dopant density on the nanometer scale.

An x-ray shadow projection microscope using a scannable point source of x-rays is under development at SUNY. The point source is generated by a focused electron beam that can be steered electromagnetically in a plane perpendicular to the optical axis of the microscope. The specimen is mounted on a rotatable mechanical stage for microtomography. An elaborate feedback system is being implemented to measure and correct the motion error of the mechanical stage. The conventional cone-beam image reconstruction algorithm suffers from two constraints. Firstly, the specimen must be contained in a sphere-like reconstruction region. Secondly, the x-ray source must be moved along a circle in the specimen coordinate system. Considering the characteristics of the x-ray microscope system of ARTS-AMIL and the limitations of the conventional cone-beam reconstruction algorithm, a general cone-beam image reconstruction algorithm is presented. The general algorithm can be applied to various scanning geometries, such as polygonal, helical, or random scanning patterns, for different reasons. In order to study the general cone-beam reconstruction algorithm, a computer simulation has been performed. With various scanning parameters, projection data were generated mathematically and then the general cone-beam reconstruction algorithm tested with the simulated data. The experimental results shows that the different kinds of scanning loci of the x-ray source consistently resulted in satisfactory 3-D reconstructed images.

A focusing error sensor has been applied to the detection of photothermal vibrational displacements for the first time and the usefulness of this detection method has been confirmed. The principle of this sensor is based upon the steep reflectivity change near the critical angle in internal reflection. The signal amplitude of the focusing error sensor has been calibrated by interferometry, and the smallest detectable amplitude has proven to be of the order of picometer by the lock-in detection. Photothermal vibrational displacements of metal plates, plastics, and others have been measured against the excitation power and frequency. A subsurface structure of a stainless steel plate has been detected by one-dimensional scanning.

Measurement of small displacements using interferometry and optical microscopy of transparent phase objects are both well established techniques. Somehow missing, however, is the combination of the interferometry's temporal resolution and displacement sensitivity with the resolving power (and hence ability to spatially discriminate) of high numerical aperture optical microscopy. This paper outlines the design of such an instrument as well as the theory of its operation. The details of both are described in Applied Optics, 29, 2383-91 where relevant references can be found.

We have developed a spectrally resolved confocal microscope with high photon efficiency for photoluminescence and fluorescence measurements. A scanning grating is placed inside the detection arm of the microscope so that the diffraction-limited spot on the sample acts like the entrance slit, and the detector pinhole acts like the exit slit of a standard monochromator. The pinhole also performs the same function as the detector pinhole in a standard confocal microscope. This arrangement has better photon efficiency than focusing the light from the detector pinhole of a standard confocal scanning laser microscope onto the entrance slit of a grating monochromator. This configuration also produces higher spectral resolution and is more flexible than one in which bandpass filters are placed in the detection arm. The microscope is described and measurements of the spectral and axial resolutions are presented. Axial resolution measurements were made using a planar sample that is both reflecting and photoluminescent. Spectrally resolved photoluminescence and fluorescence images are presented.

Two-photon excitation in scanning laser fluorescence microscopy provides axial resolution and rejection of out of focus background similar to that provided by confocal microscopy. Two- photon excitation is allowed by the extremely high peak intensity (> 1010 W/cm2) at the waist of a highly focused beam of subpicosecond pulses from a modelocked laser. Chromophore excitation and photobleaching are restricted to the focal plane by quadratic dependence of the excitation rate on incident intensity. Sectional imaging is therefore possible without the need of a confocal aperture allowing the use of UV excited chromophores, including quantitative fluorescent indicators of divalent cations, which are problematic for confocal microscopy because of chromatic aberration of objective lenses. Furthermore, sectional imaging becomes possible using widefield viewing detectors such as CCD arrays or video camera. The confinement of two-photon excitation to the focal volume allows point localized photochemistry. Two-photon excited release of caged biological probes makes possible the observation of the living cell's response to chemical stimuli with the spatial resolution of optical microscopy. Two-photon excited laser scanning photolithography allows the generation of complicated 3-D forms with a single patterned exposure and one development step. Two-photon activation of fluorescent dyes allows 3-D optical data storage at extremely high density. Two-photon excited release of caged fluorescent probes allows micromobility measurements in 3-D bulk media. By photolytic release of fluorescent dye and subsequent observation of its redistribution it is possible to quantitatively study diffusional transport properties in polymers and living biological specimens.

A packing algorithm has been developed to optimize the spinning disc design. This algorithm can generate spinning disc designs suitable for use in single-sided confocal microscopes. When an even number of spirals is chosen, the symmetrical arrangement of pinholes makes this algorithm suitable in designing spinning discs for tandem scanning confocal microscopes. The algorithm provides the possibility of maximizing pinhole packing density for improved image intensity, and maintains balanced field brightness and an equal degree of discrimination on pinhole crosstalk disregarding the location of the viewing field.

A new confocal scanning beam transmission and reflection microscope is described. The new microscope uses the same detector for both transmitted-light and reflected-light images. The transmitted beam is re-injected into the optical path of the microscope parallel to the reflected beam and the same scanning mirrors are used to descan the two beams. A set of identical objective lenses collect reflected and transmitted light from both the top and bottom of the specimen, recording images with perfect registration. Several images of biological and semiconductor specimens are presented that illustrate the advantages of confocal transmission microscopy. The first scanning-beam confocal transmitted-light differential phase contrast image is also presented.

Laser confocal imaging gives the capability of obtaining 3-D images of biological and other microscopic structures using optical slicing. This eliminates one of the problems of classical scene understanding where a 3-D to 2-D mapping and subsequent loss of information has taken place. In this paper we discuss the implementation of a multidimensional image analysis system used to extract and analyze biological structures in confocal images. The image processing and structure analysis techniques are implemented as a set of knowledge sources or tools that operate on the input image to successively refine and segment the image. These knowledge sources in the system consist of a combination of simple edge/surface detectors and multilevel thresholding to generate the initial segmentation. This segmentation is further refined by a set of more complex knowledge sources such as 3-D morphological operators, a hierarchical refinement scheme, specialized feature detectors, active contour models, and by the use of external knowledge. The analysis tools operate on the segmented image to obtain morphometrical parameters such as surface area, volume, position, and orientation of structures of interest and to generate overall statistical properties of these parameters. A visualization subsystem lets the user manipulate and selectively display the results of segmentation.

We have constructed and evaluated a scanning confocal microscope for the precise measurement of optical fiber cladding diameter. The system measures the fiber endface directly and differs from conventional microscopes in that there is no systematic error due to partial coherence. The results obtained with the scanning confocal microscope are checked by comparison with those obtained from a contact micrometer and by measuring a chrome-on- glass standard reference material provided by NIST, Gaithersburg, Maryland. Fiber diameters can be measured with a random uncertainty of 40 nm and a systematic error estimated to be 40 nm.

A differential phase and amplitude scanning optical microscope for simultaneous and independent detecting variations in surface relief and sample reflectivity is described. Results of surface studies of thin metal layers deposited on Si-wafers are presented. The3depth resolution of 2 A and reflectivity variation sensitivity of 5•lO with the spatial resolution of 2.5 mm are achieved.

The output signal of microtranslators such as PZT is not always proportional to the input signal. It usually is expensive and requires special techniques for linearization. A method is described that is simple, inexpensive, and accurate for measuring the length variations of PZT. A commercialized load cell is directly attached to a PZT (the output voltage of the load cell versus the expansion of PZT has very good linearity) and is then applied to the scanning mechanism for a laser scanning microscope (LSM). A sampling circuit for the increasing voltage used to produce sampling pulses is also studied.

This paper describes a 2-D atomic force microprobe (AFM) system designed specifically for accurate submicron critical dimension (CD) metrology. The system includes 2-D AFM sensing, 3-D position interferometry with 1.25 nm sensitivity, and a special tip design. Unlike conventional AFM scanning systems, the system operates like a nanorobot moving from point to point under computer control and sensing surfaces without making contact. The system design, operating characteristics, and application to metrology are