Frame Scan Research Articles

Measurement of field distributions in ultrasonic cleaning baths: implications for cleaning efficiency

The information available on ultrasound field distributions in cleaning baths is limited. Two techniques capable of providing this information have been investigated. The first employs a thermistor probe coated with ultrasound absorbing material and uses the rate of temperature rise when the ultrasound is switched on as a measure of local energy density. A motorized scanning frame has been used to map field distributions in three dimensions using the technique. The second technique, the Sarvazyan (dye/paper) method, uses Astralux paper placed in a bath containing an aqueous solution of methylene blue dye. More dye is transferred to the paper in areas where the ultrasound field is most intense. Pockets of gas are trapped in pores in the paper which provide additional nuclei for initiation of cavitation events and these produce small areas of intense staining about 1 mm in diameter, which are related to cavitational activity. The techniques reveal non-uniformities both in the field distribution and in the pattern of cavitational activity in ultrasound cleaning baths. Methods for assessing ultrasound field distributions are required in order to ensure that energy densities are sufficient to initiate cleaning action throughout ultrasonic cleaning baths.

In vitro validation of right ventricular volume measurement by three dimensional echocardiography.

Evaluation of ability of three dimensional echocardiography to accurately assess right ventricular volumes in vitro. Silicone casts of normal human right ventricles were examined. Each was filled with three different volumes of water to yield 15 different measurements. The casts were examined in a waterbath with three dimensional echocardiography using a 7.5 MHz ultrasound probe mounted in a scan frame. It was steered by a stepper motor, which moved the probe in steps of 0.25 mm over a distance of 5.9 cm inside the frame, acquiring an image at each step. 236 parallel slices of the cast were thus obtained, forming the three dimensional dataset. The longest axis of the right ventricular volume was defined and the area of perpendicular 1 mm thick slices was outlined manually to calculate the area of each slice. This was multiplied by the slice thickness to obtain the volume of each slice; the respective volumes were added to obtain the volume of the whole cast. The casts had a median volume of 31.1 (23) ml (range 15-100); three dimensional echocardiography gave a median volume of 29.0 (21.7) ml (15.7-91.7). Interobserver variability was 4.5% (0.4%-13.6%) and intraobserver variability 4.3% (0.2%-9.3%). Correlation between real cast volumes and volumes measured by three dimensional echocardiography was 0.99 (y = 1.08 x -0.16) with an SEE of 2.7 ml. Limits for agreement between methods ranged from -3.1 ml to 8.3 ml. In 14 of the 15 measurements, volume by three dimensional echocardiography was smaller than real volume, with the mean difference being 7.4% (2.8%-19.5%). This may be due to the thickening of surfaces of structures when imaged by ultrasonography. Right ventricular volumes can accurately be determined by three dimensional echocardiography.

Calibration Requirements and Procedures for a

Augmented reality entails the use of models and their associated renderings to supplement information in a real scene. In order for this information to be relevant or meaningful, the models must be positioned and displayed in such a way that they blend into the real world in terms of alignments, perspectives, illuminations, etc. For practical reasons the information necessary to obtain this realistic blending cannot be known a priori, and cannot be hard-wired into a system. Instead a number of calibration procedures are necessary so that the location and parameters of each of the system components are known. In this paper we identify the calibration steps necessary to build a computer model of the real world and then, using the monitor-based augmented reality system developed at ECRC (GRASP) as an example, we describe each of the calibration processes. These processes determine the internal parameters of our imaging devices (scan converter, frame grabber, and video camera), as well as the geometric transformations that relate all of the physical objects of the system to a known world coordinate system.

Calibration requirements and procedures for a monitor-based augmented reality system

Augmented reality entails the use of models and their associated renderings to supplement information in a real scene. In order for this information to be relevant or meaningful, the models must be positioned and displayed in such a way that they blend into the real world in terms of alignments, perspectives, illuminations, etc. For practical reasons the information necessary to obtain this realistic blending cannot be known a priori, and cannot be hard wired into a system. Instead a number of calibration procedures are necessary so that the location and parameters of each of the system components are known. We identify the calibration steps necessary to build a computer model of the real world and then, using the monitor based augmented reality system developed at ECRC (GRASP) as an example, we describe each of the calibration processes. These processes determine the internal parameters of our imaging devices (scan converter, frame grabber, and video camera), as well as the geometric transformations that relate all of the physical objects of the system to a known world coordinate system.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A short wavelength R-θ scanning laser microscope and optical disc tester for the characterization of optical recording media

The design and applications of a novel, short wavelength, combined R-/spl theta/ scanning laser microscope (SLM) and optical disc tester that is used for the imaging of recorded bit structures and the characterization of optical recording media is described. The instrument is optimised for magneto-optical recording applications and provides images with sub-micron resolution. Imaging is achieved by focusing the light from an argon-ion laser (514 nm or 488 nm wavelength) to a diffraction limited spot on the surface of a rotating sample to generate the line scan, whilst moving the objective lens slowly in the radial direction to generate the frame scan.

New estimation methods that directly use the time accumulated counts in the input function in quantitative dynamic PET studies

In cardiac dynamic PET studies, the input function can be obtained directly from the reconstructed images. Therefore, there is a need to convert the time accumulated count to the time-activity curve (TAC). Conventionally, this is done by dividing the total counts in a localized region on the reconstructed image obtained during each scan frame period by its frame duration. This conversion, however, can significantly bias the estimates of rate constants of a compartmental model describing the dynamics of a PET tracer. Three new methods are formulated in this study. These new methods either use the accumulated counts in the input function directly or convert the accumulated counts to the input function more accurately. Computer simulation results show, for C-11 acetate and F-18 fluoro-2-deoxy-D-glucose (FDG), that the three new methods proposed can improve significantly the parameter estimates over the ones obtained by the conventional method.

High temporal and spatial resolution studies of bone cells using real-time confocal reflection microscopy.

Chick and rat bone-derived cells were mounted in sealed coverslip-covered chambers; individual osteoclasts (but also osteoblasts) were selected and studied at 37 degrees C using three different types of high-speed scanning confocal microscopes: (1) A Noran Tandem Scanning Microscope (TSM) was used with a low light level, cooled CCD camera for image transfer to a Noran TN8502 frame store-based image analysing computer to make time lapse movie sequences using 0.1 s exposure periods, thus losing some of the advantage of the high frame rate of the TSM. Rapid focus adjustment using computer controlled piezo drivers permitted two or more focus planes to be imaged sequentially: thus (with additional light-source shuttering) the reflection confocal image could be alternated with the phase contrast image at a different focus. Individual cells were followed for up to 5 days, suggesting no significant irradiation problem. (2) Exceptional temporal and spatial resolution is available in video rate laser confocal scanning microscopes (VRCSLMs). We used the Noran Odyssey unitary beam VRCSLM with an argon ion laser at 488 nm and acousto-optic deflection (AOD) on the line axis: this instrument is truly and adjustably confocal in the reflection mode. (3) We also used the Lasertec 1LM11 line scan instrument, with an He-Ne laser at 633 nm, and AOD for the frame scan. We discuss the technical problems and merits of the different approaches. The VRCSLMs documented rapid, real-time oscillatory motion: all the methods used show rapid net movement of organelles within bone cells. The interference reflection mode gives particularly strong contrasts in confocal instruments. Phase contrast and other interference methods used in the microscopy of living cells can be used simultaneously in the TSM.

Spectral imaging of clouds using a digital array scanned interferometer

Spectral images of various cloud fields have been made from the ground using a prototype imaging interferometer. The instrument, called DASI (digital array scanned interferometer), is under development as an alternative technique for terrestrial remote sensing. Our paper describes the unusual characteristics of DASI's that make them promising candidates for both ground and aircraft based measurements of clouds. These characteristics include superior signal-to-noise potential, design simplicity and compactness. The prototype DASI had a wavelength sensitivity range of 4550–9090 cm −1 (1.1–2.2 μm), a spectral resolution of 300 cm −1, a spatial field of view of 5 degrees, and 256 transverse spatial elements for each exposure frame with exposure rates up to 1 frame/s. Spectrally resolved images of cirrus and cumulus clouds over the San Francisco Bay area were obtained by multiple frame scanning over the field of view. The DASI measurements are compared with radiative transfer calculations using LOWTRAN-7. Modification of the LOWTRAN code was necessary so that high spectral resolution data for ice optical properties could be used. With these modifications, the agreement between measured and model results is good in some cases. However, quantitative interpretation of these preliminary measurements was not generally possible because of various sources of uncertainty. Finally, a discussion is given on the potential applications and science yields of DASI instruments in the framework of coordinated field missions such as project FIRE. Such applications include the use of ground and airborne based DASI's to retrieve microphysical properties of clouds and to investigate current problems in atmospheric radiation.

Virtual sources, guided wave paths, and far-field radiation from an internally excited ribbed cylinder

An experimental analysis of structural dynamics and acoustic radiation associated with a large scale (7.5 m long, 1.5 m diam) immersed hull structure is presented. Pressure data were collected with an automated scanning frame and an array of hydrophones at 0.3-m intervals over a measurement surface conformal to and 0.3 m distant from the body. Visualizations of the pressure field in the measurement plane were analyzed to verify data quality and to characterize dominant phenomena (hull resonances, low-order mode shapes, virtual source locations, and scattering discontinuities). The data were then backprojected to the hull using near-field acoustical holography algorithms to obtain (normalized) pressure, velocity, and intensity distributions on the hull. Finally, algorithms based on the Helmholtz integral were employed to determine far-field radiation patterns. [Work sponsored by NAVSEA.]

A 400KV multi-functional electron and ion radiation accelerator

In this paper we describe a 400kV multi-functional electron and positive ion irradiation accelerator based upon a 400kV Cockcroft-Walton, which was successfully used to accelerate electrons and positive ions with electron beam current of more than 5 mA. It has a scanning window of 1200mm in width, a scanning frame of 4500×1400mm. The transmitting speed of the scanning frame is between 0.1–5m backward and forward, continuously adjustable. The conversion time from accelerating positive ions to electrons is less than twenty minutes, and vice versa. It is proved that this accelerator can meet more requirements in the fields of nuclear physics and electron irradiation applications.

Criteria for use of electron beam charging technique for very large scale integration process inspection

A mathematical description of the method of testing by electron beam charging is used to clearly specify its measurement capabilities. The scanning electron microscopy parameters of beam current, frame scan time, and magnification, are used to derive the requirements necessary to distinguish between shorted and isolated structures.

Towards compositional imaging using auger electron signals

Auger electron spectroscopy (AES) is a well established, quantitative surface analytical technique with reasonable accuracy of the order of 1% of an atomic monolayer. When it is combined with a small electron beam diameter, high resolution concentration maps of the surface distribution of elements can be obtained. This has been demonstrated to be a useful and powerful method in surface analysis. However, because of the rather low efficiency of Auger electron production (∼ 10-5 - 10-4 per incident electron) long frame scan times (of the order of hours) have to be employed in the case of multi-element composite samples. The raw images often reflect not only surface elemental distribution but also electron beam fluctuations. In addition, subsurface atomic number variations as well as local surface topography are known to alter the contrast of these images. In order to quantify Auger maps to give concentration distribution of the surface elements, sample and instrumental effects have to be separated.

The Electron Microscope and the Computer: Present Trends and Future Prospects

In the present generation of electron microscopes the roles of computers or microprocessors can be divided into control, acquisition and analysis of both spectral and image data. Not much, however, has been done to realise the full power of computer based systems and integrate all these functions with the electron optics. The control of practically all microscope columns is performed by an 8-bit or 16-bit processor usually running a program that repeatedly scans for user inputs and changes lens currents or alignment settings if necessary. External control for special experiments can either be implemented by scanning an additional user input from a serial port or by allowing external analog signals to replace those generated by the microscope control scheme. As the program loop typically takes 0.1 sec to complete it is preferable to implement some functions such as external beam scanning by providing analog ramps (even if generated by another computer).Computer acquistion of data was introduced to electron microscopy with analytical techniques, such as EDX, in which the computer was the basis of a multi channel analyser. In the case of energy loss and Auger spectroscopy, computer scanning of the spectrometer and acquisition of single electron pulse-counted data quickly displaced chart recorders as a means of collecting data. A computer based system not only could perform acquisition more efficiently, it could also provide a convenient means for processing the results and doing quantitative analysis. Furthermore digitally stored data could easily be transferred to other systems on disks or by direct link (such as ethernet) and analysed elsewhere. However for image acquisition there has been very little use of computers in acquiring data. Although microscopists are happy to consider a spectrum as an array of numbers they still prefer to deal with images as pictures rather than digital data sets. The problems are not entirely psychological since a major barrier to the widespread use of image processing in microscopy is the lack of a suitable detection system. TV cameras compare unfavourably with photographic plates in terms of both dynamic range and "resolution" as defined loosely in terms of pixel size or lines/mm. This argument does not apply to scanning microscopes but, even in scanning systems, frame buffers and powerful computer systems have only been integrated as part of the microscope electronics in the last few years. Microscopists still prefer to measure quantities from exposed photographs rather than work with digitized data in a workstation environment using high level image processing software. Until recently cost may have been a consideration but now computing platforms of sufficient capability are less than 1/5 of the cost of an average SEM.

Contrast of Electron-Acoustic Microscopic Image–For Si Tr-Chip under Bias Application–

The study investigated the relation between an electron-acoustic microscopy (EAM) image and images of several SEM modes. A pnp Darlington Si Tr-chip was used as a specimen. The site of ultrasonic signal generation by irradiated electron-beam was compared between the two kinds of images alternately photographed in “one frame scan” with the beam in a fixed condition. The results showed that (1) the contrast of electron acoustic image (EAI) changes with the bias voltage applied to the Tr-chip, (2) EAI resembles the EBIC image but is not exactly the same, and (3) an ultrasonic signal is not always generated at areas of different thermal properties.

Statistical Image Processing With A Hybrid Flying Window Scanning System

The local statistics of an image are needed, for example, to transform the input into stationary data for which many standard enhancement/coding algorithms are optimized, as well as to implement locally adaptive processing techniques. We discuss a system that uses a flying window scanner to extract the second-order parameters (local mean, variance, and correlation length) in real time and show how these parameters can be used to transform an input into block stationary data. The same scanning system is also applied to the measurement of a variety of histograms in a single frame scan.

Initial stage of an underwater explosion of cylindrical charges with foliated cases

This paper is devoted to an investigation of the nature of shock passage through the interlayers consisting of materials with different dynamic stiffness, to determine of the initial shock amplitude and the law of its attenuation in the near zone (at ranges less than 10 discharge radii). The explosion and shock generation were recorded by a schlieren shadowgraph and high-speed photorecorder SFR-1 in 2 modes: frame by frame scan and continuous sweep. The investigations performed permitted establishment of the possibility, in principle, of controlling the shock parameters during an underwater explosion in the zone near the charge.

Scanning auger electron microscopy with high spatial or high energy resolution

An all-electrostatic, computer controlled, high spatial and high energy resolution, scanning Auger electron microscope incorporating a RHEED camera is described. The electron column has a 50 nm spatial resolution at 55 mm working distance. The energy analyser allows high energy resolution of up to 630 or constant energy windows of down to 1 eV over the energy range of 20 eV to 1000 eV. A system software allowing flexibility of the computer control is described. 128 × 128 pixel Auger images of Al and SiO 2, with frame scan times of the order of 8 min, are presented.

A Noncontact Velocimeter Using Sensing Arrays

A method for measuring the velocity of a surface moving relative to two area-sensing arrays is described. The arrays are separated by a known distance and are driven by a common clock so that their outputs can be correlated element for element. The velocity of the surface in the direction of the center line between the arrays is measured by determining the transit time required for a portion of the surface imaged onto the leading array to move to the trailing array. This is accomplished by exposing the leading array for one frame scan, and after some adjustable time delay, exposing the trailing array and correlating its output with the leading-array output. The time delay which gives the best correlation is the transit time. Experimental results from a laboratory model are presented.

Measurement of head movement during auditory localization

Head movement can have a significant effect on the ability to locate the direction of a sound source. A system has been designed to track the head movement in response to sound originating at different azimuth locations with respect to the head. A videotape record is made of a light approximating a point source carried on a lightweight “beanie” mounted on the listener’s head. Movement of the light is monitored by the video camera and recorded on tape, along with the sound stimulus and information concerning loudspeaker location and time. The horizontal and vertical coordinates of the light-spot image are determined in relation to the video synch pulses defining the field borders. Synch signals are available from a video monitor either in real-time or from tape replay to define each TV frame and horizontal scan line. The circuitry interfaces to a computer programmed to take the information, apply a calibration, and process the data into records of time-varying head position and velocity. Examples of both digital and graphic printouts of head movement are given. The system is capable of expansion to three-axis operation.

A digital scanning Auger electron microscope incorporating a concentric hemispherical analyser

A scanning electron microscope with a field-emitting electron gun, digitally controlled scanning and a concentric hemispherical energy analyser is described and compared with different types of energy dispersive scanning electron microscopes. The advantages of hemispherical analysers accessed by electrostatic lenses are flexible electron optical control of working distances and resolving power. A 4 element lens is described which results in an analyser with a 2 eV window over an energy range of 20 eV to 800 eV. Auger images of calcium and sulphur on titanium are given. Spatial resolutions of 50 nm and frame scan times of a few minutes are possible.