High-resolution Optical System Research Articles

High-resolution three-dimensional scanning optical image system for intrinsic and extrinsic contrast agents in tissue

This article presents the theory and development of a three-dimensional (3D) imaging instrument capable of determining the biochemical properties of tissue by measuring the absorption or fluorescence of different intrinsic and extrinsic agents simultaneously. A bifurcated optical fiber bundle, serving to deliver the excitation light and collect the emission or reflection light, scans over the flat tissue surface retrieving optical signals in each pixel. Two-dimensional (2D) images of a series of subsequent sections are obtained after signal conversion and processing to yield a 3D image. Manipulation of the scanning step and diameter size of the fibers within the bundle, the spatial resolution of the instrument attains a maximum of 40 × 40 × 10 μm3. The wavelength range is extended from ultraviolet to the near infrared (NIR) through specialized optical design, typically employed for the NIR extrinsic contrast agents study. The instrument is most applicable in situations involving the measurement of fluorescence or absorption at any specific wavelength within the spectrum range. Flavoprotein and nicotinamide adeine dinucleotide are the two typical intrinsic agents indicating the oxidization and reduction status of the tissue sample, with their fluorescence detected at wavelengths of 540 and 440 nm, respectively. Oxy and deoxy hemoglobin are two other significant intrinsic agents for evaluating the blood oxygenation saturation by recording their absorptions at two different wavelengths of 577 and 546 nm. These intrinsic agents were measured in this study for comparison of biochemical properties of rat liver in different gas inhalation treatments. Indocyanine green, a NIR extrinsic contrast agent measured at wavelengths of 780 nm/830 nm as excitation/emission can indicate blood pooling by displaying the distribution of blood vessels within a 9 L tumor. The advantage of high sensitivity, spatial resolution, and broad applied potentiality were demonstrated by the instrument during these experiments.

Sub-Doppler spectroscopy with a narrow linewidth pulsed optical parametric oscillator: hyperfine structure in the PF radical

A preliminary version of a very high-resolution pulsed optical parametric oscillator laser system is described. It is seeded by a tunable diode laser around 790 nm to give tunable, narrow-bandwidth (∼160 MHz) light around 645 nm. This is frequency doubled and used to take sub-Doppler spectra of the A 3 Π –X 3 Σ − (3,0) transition of the PF radical in a molecular beam. The resolution achieved (0.015 cm −1=450 MHz in the UV) is sufficient to resolve hyperfine structure clearly. An analysis of this is presented, together with a discussion of the bonding in PF as revealed by the hyperfine constants.

OPTICAL SENSOR DESIGN USING NONLINEAR PROGRAMMING

Nonlinear programming is used to design a non-contact high resolution optical system capable of sensing all six degrees of freedom of an object. This system uses two wide-beam lasers to illuminate two reflective fiducial markers placed on the object's surface. Light rays reflected from these markers are incident on three position sensitive detectors, which measure the x-y coordinates of the ccntroids of the incident light spots. The mathematical model of the system, which maps object coordinates into light spot coordinates, is very complex and highly nonlinear. The purpose of the study is to find designs that optimize three objectives: linearity error, range, and sensitivity, both singly and in combination, and to gain insight into the design tradeoffs among them. The design variables include the angular orientation of the laser beams, the positions of each of the fiducial markers, and the distance between sensor and object planes. Analysis of the model shows how these variables must be changed to improve each objective. Computational results obtained using a generalized reduced gradient (GRG) algorithm show how geometric constraints on system area and component overlap limit the attainment of each objective. Tradeoff studies show the strong tradeoffs among these objectives, and indicate that the most important design variables are the orientations of the light sources. The methodology shows great promise for reducing the development time of sensors with specific requirements, and for improving sensor performance.

Effect of Datum Securing Method on Precision of Mechanical Alignment System

In this research, the achievable precision level using mechanical datums for manufacturing has been studied. Specifically, the effect of how a datum is secured in a mechanical alignment system was studied with the aid of a high-resolution multidimensional optical position monitoring system developed for the purpose. The study shows that the way datum is secured can be a major factor affecting the alignment precision of a mechanical alignment system. For a datum prepared by randomly inserting dowel pins into precision bored holes, a common practice in industry, the precision level was found to be worse than 10 μm. The results also show that the precision level can be readily improved by addressing this major cause of inaccuracy. Different methods depending on manufacturing requirements and constraints have been proposed. Some of these simple procedures lead to more than an order of magnitude improvement in alignment precision. [S1087-1357(00)02001-3]

Distorted wave front produced by a high-resolution projection optical system having rotationally symmetric birefringence

The influence of birefringence caused by rotationally symmetric stress distribution in a high-resolution projection optical system is investigated. The general form of the pupil function is derived based on the Jones matrix calculation, expressing the wave front as a combination of the two orthogonal polarization components. Assuming a linearly polarized incident beam, it is found that the main polarization portion of the wave front exiting the projection lens has astigmatic aberration in the Seidel region and shows phase singularity at four pupil points at which the amplitude transmittance becomes zero.

Structural Change Caused by Substitution of Nd for Sm in (Nd, Sm)AlO3: Application of Synchrotron High-Resolution Powder X-ray Diffraction

Structural change caused by substitution of Nd for Sm in perovskite (Nd, Sm)AlO3was analysed by application of high-resolution powder X-ray diffraction using synchrotron radiation. The parallel, well monochromated and bright incident X-rays improved the full width at half-maximum (FWHM) to 0.027° in a wide 2θ range for the standard Si powder. Applying this high-resolution optical system, the lattice parameters of the solid solution (Ndx, Sm_{1-x})AlO3were precisely analysed for the phases fromx = 0.0 to 1.0 with an interval of 0.2. The lattice parameters of a series ofRAlO3vary systematically with the average ionic radii of R^{3+}, accompanying a structural change from orthorhombic to a trigonal system at around R^{3+}=1.11 Å corresponding to average ionic radii of 0.7{\rm Nd}^{3+}+0.3{\rm Sm}^{3+}. In orthorhombic phases, deformation of the crystal lattice from its ideal cubic lattice is minimized at aroundx = 0.0–0.2 in (Ndx, Sm_{1-x})AlO3and increased with increasing average ionic radii of Nd^{3+} and Sm^{3+}. The structure changes from orthorhombic to trigonal at aroundx = 0.7.

Delayed signal propagation via CA2 in rat hippocampal slices revealed by optical recording.

Signal propagation from mossy fibers to CA1 neurons was investigated in rat hippocampal slices by a combination of electrical and optical recordings. The slices were prepared by oblique sectioning of the middle part of the hippocampus to preserve fiber connections. The mossy fibers were stimulated to induce population spikes (PSs) and excitatory postsynaptic potentials in the middle part of the CA1 region. Latencies of maximal PSs in CA1 varied widely among slices; they ranged from 7 to 13.5 ms, with two maxima at 9 and 11.5 ms. The fastest PSs probably are evoked by the Schaffer collaterals that connect the CA3 and CA1 regions in the well-known trisynaptic circuit. However, the slower PSs suggest the existence of additional delayed inputs. To determine the source of the delayed input, slices were stained with a voltage-sensitive dye, RH482, and the optical signals relevant to membrane potential changes were detected by a high-resolution optical imaging system. Optical recording of responses to mossy fiber stimulation indicated two distinct types of signal propagation from CA3 to CA1. In preparations evincing the fast type of propagation, signals spread to CA1 within 7.2 ms after the mossy fiber stimulation. During such propagation, activity flowed directly from CA3 to the stratum radiatum of CA1. Other preparations illustrated slow signal propagation, in which optical signals were generated in CA2 before spreading to CA1. During such slow signal transmission, activity persisted in CA2 and its surrounding area for 3 ms before propagating to the strata radiatum and oriens in CA1. In such cases, CA1 activity was detected within 10.8 ms of mossy fiber stimulation. In some slices, a mixture of the fast and slow propagation patterns was observed, indicating that these two transmission modes can coexist. Our data reveal that CA2 neurons can transmit delayed excitatory signals to CA1 neurons. We therefore conclude that consideration of electrical signal propagation through the hippocampus should include flow through the CA2 region in addition to the traditional dentate gyrus-CA3-CA1 trisynaptic circuit.

Intramolecular energy transfer from isotope selective overtone spectroscopy by vibrationally assisted dissociation and photofragment ionization

AbstractOvertone spectroscopy by vibrationally assisted dissociation and photofragment ionization (OSVADPI) has been coupled with the detection of fragments in a mass spectrometer allowing isotope selective overtone spectroscopy (ISOS) on naturally occurring isotopomer mixtures. The room temperature CH‐chromophore spectra of CF2HCl (polyad component Nj = 41 near 11430 cm−1) and of chloroform (Nj = 21 near 5942 cm−1 and Nj = 31 near 8726 cm−1) have been investigated in this way and discussed in relation to intramolecular energy transfer. The features of the central Q‐branch regions are assigned with resolution of the Cl‐isotopomers, and Q‐branch maxima and Cl‐isotopomer shifts are determined. The effect of the strong Fermi resonance, mixing CH‐stretching and bending modes, on the position of vibrational hot band transitions is demonstrated. We describe in detail the extension of our technique into the near and mid infrared range with a high resolution optical parametric oscillator system which has a wide range of potential applications as a general infrared spectroscopy with isotope and mass selection (IRSIMS).

Unique properties of cardiac action potentials recorded with voltage-sensitive dyes.

Optical mapping with voltage-sensitive dyes has made it possible to record cardiac action potentials with high spatial resolution that is unattainable by conventional techniques. Optically recorded signals possess distinct properties that differ importantly from electrograms recorded with extracellular electrodes or action potentials recorded with microelectrode techniques. Despite the growing application of optical mapping to cardiac electrophysiology, relatively little quantitative information is available regarding the characteristics of optical action potentials recorded from cardiac tissue. A high-resolution optical mapping system and microelectrode techniques were used to determine the characteristics of guinea pig ventricular action potentials recorded with the voltage-sensitive dye di-4-ANEPPS. The effects of optical magnification, tissue-light interaction, sampling rate, voltage resolution, spatial resolution, and cardiac motion on action potential signal characteristics were determined. The optical action potential signal represents the relative change in transmembrane potential arising from a volume of cells, where the area of a recording site is determined by optical magnification and detector area, and the depth of recording is determined by system optics and the visible light transmission characteristics of cardiac muscle. Using photographic lenses, the depth of tissue contributing to the signal is < 250 microns. The action potential plateau and final repolarization can be accurately reconstructed from data digitized at modest sampling rates (450 to 750 Hz), since the frequency content of optical action potentials is band-limited to approximately 150 Hz. However, faster sampling rates are needed to depict the subtle details of the action potential upstroke. In addition to temporal resolution, it is essential to achieve sufficient dynamic range and voltage resolution to accurately represent the time course of membrane potential change. Voltage resolution is inversely related to the square of spatial resolution, hence, there exists an inherent trade-off between increased spatial resolution and diminished voltage resolution. Cardiac motion, which can otherwise limit spatial resolution as well as signal fidelity, can be effectively reduced using mechanical stabilization of the heart without distorting action potential characteristics. Optical mapping with voltage-sensitive dyes provides high-fidelity multisite action potential recording with flexible spatial resolution. When recording cardiac action potentials with voltage-sensitive dyes, the interdependence of temporal, spatial, and voltage resolutions must be carefully considered.

High-Resolution Optical Measurements of Surface Roughness for Beta-Layered Deuterium-Tritium Solid Inside a Re-Entrant Copper Cylinder

A high-resolution optical imaging system and custom-designed image analysis software are used to make surface roughness measurements for deuterium-tritium (D-T) solid layers, equilibrated inside a ...

ORION: Clearing near-Earth space debris using a 20-kW, 530-nm, Earth-based, repetitively pulsed laser

When a large piece of space debris forced a change of flight plan for arecent U.S. Space Shuttle mission, the concept that we are trashing space as well as Earth finally attained broad public awareness. Almost a million pieces of debris have been generated by 35 years of spaceflight, and now threaten long-term space missions. The most economical solution to this problem is to cause space debris items to reenter and burn up in the atmosphere. For safe handling of large objects, it is desired to do this on a precomputed trajectory. Due to the number, speed, and spacial distribution of the objects, a highly agile source of mechanical impulse, as well as a quantum leap in detection capability are required. For reasons we will discuss, we believe that the best means of accomplishing these goals is the system we propose here, which uses a ground-based laser system and active beam phase error correcting beam director to provide the impulse, together with a new, computer-intensive, very high-resolution optical detection system to locate objects as small as 1 cm at 500-km range. Illumination of the objects by the repetitively pulsed laser produces a laser-ablation jet that gives the impulse to de-orbit the object. A laser of just 20-kW average power and state-of-the-art detection capabilities could clear near-Earth space below 100-km altitude of all space debris larger than 1 cm but less massive than 100 kg in about 4 years, and all debris in the threatening 1–20-cm size range in about 2 years of continuous operation. The ORION laser would be sited near the Equator at a high altitude location (e.g., the Uhuru site on Kilimanjaro), minimizing turbulence correction, conversion by stimulated Raman scattering, and absorption of the 530-nm wavelength laser beam. ORION is a special case of Laser Impulse Space Propulsion (LISP), studied extensively by Los Alamos and others over the past 4 years.

3次元自由曲面形状の光非接触測定装置 (第3報)

This study describes the development of an optical noncontact measuring instrument for the 3 -D shape of an object with a free-form surface. The optical sensing system of the instrument proposed in the previous papers detects the depolarized component of backscattered light from the object surface excluding specularly reflected light. Diffusive object surfaces and metal surfaces with both specular and diffusive components can be measured by using the system. However the detectable range in height is narrow for one point measurement and the system is roughly positioned by manual operation at steep slope and edge portion of the object surface to be measured. In this paper, a low resolution optical system for expansion of detecting range has been developed as well as the high resolution optical system already reported. Therefore a new optical sensing system can possess both rough and fine positioning functions and automatically change them each other. The Lew sensing system is wider in detectable range and shorter in measurement time than the previous sensing system. Using the new sensing system the standard deviation of measurement errors can be evaluated 1.4μm in the case of the diffusive object surface having white color and less than ±83° in inclination angle.

High-resolution spectra of cross-phase modulation in optical fibers

Cross-phase-modulation (XPM) effects were investigated as a novel nondegenerate method to control the spectrum of an optical pulse. The oscillating substructures in the XPM spectra were measured with a high-resolution optical spectral analysis system. The dispersion of the third-order nonlinearity was obtained by measurement and analysis of the XPM and self-phase-modulation spectra of the probe and pump pulses at different wavelengths.

Optical spectrum measurement system with very high resolution

Since the discovery of semiconductor-optical fiber, the development of optical communication has been significant. In particular, a baseband modulation frequency in high-speed communication has been increased up to the order of 10 GHz at the research level and of 1 GHz at the practical level. A factor which is the obstacle for further improvement is the bandpass width limitation for a transmitted signal caused by the spread of an oscillation spectrum of LD and also the wavelength dispersion of an optical fiber. For long-distance and high-speed transmission, it is important to determine accurately the spread of the LD spectrum for designing an optical transmission system. The objective of the present study is to clarify the condition required for a high-resolution optical spectrum analysis system, which is essential for understanding the spectrum-spread and chirping of the LD laser at a time of high-speed modulation. A comparison of various measurement systems is made. A method of combining the diffraction grating system and the Fabry-Perot etalon system is proposed, and the optimization of the system is discussed in detail. The present paper describes for the first time the optimization of the tandem configuration of a diffraction grating and Fabry-Perot etalon systems. Based on those discussions, a prototype system has been constructed with which a maximum wavelength sweeping width of 200 MHz/div and resolution of 100 MHz were demonstrated.

High-resolution spectra of self-phase modulation in optical fibers

We present theoretical calculations and experimental measurements of self-phase-modulation spectra generated with picosecond laser pulses at 532 and 1064 nm propagating in optical fibers. The spectral structures of self-phase-modulation spectra are observed with a high-resolution optical spectral analysis system. The experimental observations are in good agreement with the theoretical predictions.

Visualisation des champs ultrasonores par interférométrie hétérodyne

A high resolution optical system has been designed and developed for imaging pulsed ultrasonic fields transmitted in water by piezoelectric transducers. The particle displacement was measured by a compact heterodyne interferometer whose probe beam is reflected by a thin membrane immersed in front of the transducer. Experiments carried out on focused or planar transducers demonstrate the capability of the system to map acoustic fields both in time and spatial domains. The spatial resolution and the dynamic range reached 20 μm and 45 dB and the bandwidth can be enlarged up to 40 MHz. Results are presented in various cross sectional views (B-scans, C-scans and 3D profiles)

Small-probe-volume laser Doppler anemometry measurements of turbulent flow near the wall of a rib-roughened channel

A special-purpose high-resolution laser Doppler optical system has been used to investigate the wall region of a turbulent water flow within a rectangular channel. The exceptionally small control volume (30 μm × 17 μm × 15 μm) has enabled unique LDA measurements to be achieved on two walls of the channel: one a plane smooth wall and the opposite one a rib-roughened wall. The plane wall measurements agree well with existing classical sublayer/bufferzone concepts. However, for the first time the near-wall experimental measurements between two successive ribs show that reattachment to the channel floor between the ribs may never be achieved for this particular geometry. Previous measurements on this geometry by using relatively large control volumes are therefore misleading. In view of this observation it is not surprising that the existing numerical models have difficulty in accurately predicting points of reattachment and separation for these types of geometries.

Functional Organization of Primate Visual Cortex Revealed by High Resolution Optical Imaging

A high spatial resolution optical imaging system was developed to visualize cerebral cortical activity in vivo. This method is based on activity-dependent intrinsic signals and does not use voltage-sensitive dyes. Images of the living monkey striate (VI) and extrastriate (V2) visual cortex, taken during visual stimulation, were analyzed to yield maps of the distribution of cells with various functional properties. The cytochrome oxidase--rich blobs of V1 and the stripes of V2 were imaged in the living brain. In V2, no ocular dominance organization was seen, while regions of poor orientation tuning colocalized to every other cytochrome oxidase stripe. The orientation tuning of other regions of V2 appeared organized as modules that are larger and more uniform than those in V1.

High-resolution low-voltage electron optical system for very large specimens

This article introduces an unconventional electron optical probe forming system which is particularly suitable for low beam voltages and very large specimens, such as semiconductor wafers which also require a large angle tilting. The system can produce an electron probe of less than 20 Å for a nontilting specimen at 1-kV beam voltage with a working distance of 2.5 mm. The particular design allows a large volume of free space below the specimen which may be used to accommodate a complicated transporting mechanism.

Individual sarcomere length determination from isolated cardiac cells using high-resolution optical microscopy and digital image processing

Discrete sarcomere lengths have been determined from dynamically contracting isolated cardiac cells with a high-speed, high-resolution direct optical imaging system. Calcium-tolerant cardiac cells from the rat are isolated by perfusion with collagenase and hyaluronidase. Individual sarcomere lengths can be determined by directly imaging the cell's striation pattern onto a solid-state charge-coupled device (CCD) detector interfaced with a digital computer. The precision of detection in a real light microscopic optical system is discussed in relation to the type of image detector, optical contract enhancement techniques, and digital image processing. The optical performance of the direct striation pattern image apparatus has been determined empirically with test grids under standard bright-field and Nomarski-differential interference contrast (DIC) conditions for application to real muscle imaging. Discrete striation positions of isolated cells have been detected and followed with high precision during phasic contraction-relaxation cycles down to average sarcomere lengths as short as 1.43 +/- 0.053 microns. The maximum rates of contraction and relaxation are rapid and synchronous in time course along the length of the cell. These results indicate that direct optical imaging can provide an accurate means to monitor discrete striations and sarcomere lengths along the length of Ca2+-tolerant heart cells.