Sinusoidal Scanning Research Articles

Bridging the gap between conventional and video-speed scanning probe microscopes

A major disadvantage of scanning probe microscopy is the slow speed of image acquisition, typically less than one image per minute. This paper describes three techniques that can be used to increase the speed of a conventional scanning probe microscope by greater than one hundred times. This is achieved by the combination of high-speed vertical positioning, sinusoidal scanning, and high-speed image acquisition. These techniques are simple, low-cost, and can be applied to many conventional microscopes without significant modification. Experimental results demonstrate an increased scan rate from 1 to 200 Hz. This reduces the acquisition time for a 200×200 resolution image from 3 min to 1 s.

Image reconstruction in reduced circular sinusoidal cone-beam CT.

Non-circular scanning geometries such as helix or circular sinusoid have been used or proposed for cone-beam computed tomography (CBCT), because they provide sufficient data for numerically stable and exact image reconstruction within the scanned volume. Analytic algorithms have been developed for image reconstruction from cone-beam data acquired with a full-scan circular sinusoidal trajectory. In this work, we propose an innovative imaging approach in which a reduced-scan circular sinusoidal trajectory is used for acquiring data sufficient for exact 3D image reconstruction. A filtered backprojection (FBP) algorithm based on Pack-Noo's reconstruction formula is applied for image reconstruction in reduced-scan circular sinusoidal scans. We have conducted numerical studies to demonstrate the reduced-scan approach and to validate the FBP reconstruction algorithm in the proposed approach. The proposed scanning method can contribute to increasing the throughput of a scanner, while improving the image quality compared to a conventional circular scan.

Extension of distance measurement range in a sinusoidal wavelength-scanning interferometer using a liquid-crystal wavelength filter with double feedback control

The optical path difference (OPD) and amplitude of a sinusoidal wavelength scanning (SWS) are controlled with a double feedback control system in an interferometer, so that a ruler marking every wavelength and a ruler with scales smaller than a wavelength are generated. These two rulers enable us to measure an OPD longer than a wavelength. A liquid-crystal Fabry-Perot interferometer (LC-FPI) is adopted as a wavelength-scanning device, and double sinusoidal phase modulation is incorporated in the SWS interferometer. Because of a high resolution of the LC-FPI, the upper limit of the measurement range can be extended to 280 microm by the use of the phase lock where the amplitude of the SWS is doubled in the feedback control. The ruler marking every wavelength is generated between 80 microm and 280 microm, and distances are measured with a high accuracy of the order of a nanometer in real time.

Mapping approach for image correction and processing for bidirectional resonant scanners

We have developed a mapping algorithm for correcting sinusoidally scanned images from their distortions. Our algorithm is based on the close relationship between linear and sinusoidal scanning. Straightforward implementation of this algorithm showed that the mapped image has either missing lines or redundant lines. The missing lines were filled by fusing the mapped image with its median-filtered or interpolated version. The implementation of this algorithm shows that it is possible to retrieve up to 98% of the original image (depending on the algorithm used for data fusion) as measured by the recovered energy. Excellent correction was obtained for both simulated scanned images and actual images from a scanning laser radar system.

Scanned beams of high-energy charged particles and problems of their collimation

The coordinate distributions of the accelerated charged particle flux density that are simultaneously formed by sinusoidal scanning and collimation are analyzed. Under certain formation conditions, the edge portions of these distributions are shown to take a two-humped shape. The experimental data obtained are in good agreement with the calculation. Advices are given about practical use of these beams in view of the above effects.

Diffractive element design for resonant scanner angular correction: a beam retardation approach

A new approach for designing diffractive optical corrective elements with zooming capability to convert nonlinear sinusoidal scanning into linear scanning is proposed. Such a device will be useful for linearizing the angular scan of a resonant mirror scanner. The design methodology is to create a graded index of a refraction device as the reference design with its index of refraction parameters based on beam retardation through propagation in an inhomogeneous medium. The diffractive element is designed by utilizing a binarizing algorithm of the accumulated phase from transmission through the refractive element. In contrast to a prior approach, which was introduced based on the beam propagation through inhomogeneous media, the new approach takes beam diameters into consideration. This makes both the refractive element and its associated diffractive element more robust against beam fanning.

Diffractive element design for resonant scanner angular correction

We propose an optical corrective element with zooming capability to convert nonlinear sinusoidal scanning into linear scanning. Such a device will be useful for linearizing the angular scan of a resonant mirror scanner. The design methodology is to create a graded index of refraction device as the reference design, with its index of refraction parameters based on the propagation of an electromagnetic field in inhomogeneous media. The algorithm for converting this refractive element to the corresponding binary diffractive version is also presented. Design and simulation data are shown.

Electron spinT 2 of a nitroxyl radical at 250 MHz measured by rapid-scan EPR

Rapid-scan electron paramagnetic resonance (EPR) was used to measure the room temperature spin-spin relaxation timeT2 for the per-deuterated nitroxyl radical, 4-oxo-2,2,6,6-tetramethylpiperidin-1-oxyl-d16 in water at 250 MHz. Signals were recorded on a locally constructed system using either sinusoidal or triangular magnetic field scans. Values ofT2 were obtained by simulation of the rapid-scan response and were systematically shorter for the high-field line (m1=−1) than for them1=0 or +1 lines. Form1=+1, the value ofT2 increased from 0.41±0.03 μs at 0.5 mM to 0.53±0.03 μs at 0.1 or 0.2 mM. Form1=−1,T2 increased from 0.35±0.03 μs at 0.5 mM to 0.42±0.03 μs at 0.1 or 0.2 mM. These values put lower bounds on the values ofT1 for this nitroxyl at 250 MHz.

Impact of resonator on direct-detected rapid-scan EPR at 9.8 GHz

Rapid-scan electron paramagnetic resonance spectra at 9.8 GHz were obtained on a Bruker E580 spectrometer. Spectra of lithium phthalocyanine (LiPc) needles (T1=8 μs,T2=3.4 μs) and of a 0.2 mM aqueous solution of Nycomed triarylmethyl (trityl-CD3) radical (T1=11.5 μs,T2=8 μs) were recorded at scan rates between 3.4·103 and 7.5·105 G/s at the center of sinusoidal scans. Signals for LiPc were obtained with a split-ring resonator, a rectangular resonator and a dielectric resonator. At faster scan rates the small bandwidth of the high-Q dielectric resonator filters, out high-frequency components of the rapid-scan signals. Field inhomogeneities induced by the rapidly changing magnetic field increase with scan rate and are greater with the dielectric and split-ring resonantors than with the rectangular resonator. Data for trityl-CD3 were recorded with the rectangular resonator. The extended trityl sample, about 3 mm long, shows larger effects of magnetic field inhomogeneities than the small LiPc crystals.

Scanning strategy for mapping the Cosmic Microwave Background anisotropies with Planck

We present simulations of different scanning strategies for the Planck satellite. We review the properties of slow- and fast-precession strategies in terms of uniformity of the integration time on the sky, the presence of low-redundancy areas, the presence of deep fields, the presence of sharp gradients in the integration time, and the redundancy of the scanning directions. We also compare the results obtained when co-adding all detectors of a given frequency channel. The slow-precession strategies allow a good uniformity of the coverage, while providing two deep fields. On the other hand, they do not allow a wide spread of the scan-crossing directions, which is a feature of the fast-precession strategies. However, the latter suffer from many sharp gradients and low-coverage areas on the sky. On the basis of these results, the strategy for Planck can be selected to be a slow (e.g. 4 month-period) sinusoidal or cycloidal scanning.

31.1: Invited Paper: Sinusoidal Deflection on a CRT/CPT: Finally a Reality

AbstractThis paper describes the design approach, obstacles encountered and solutions found while building a 526 Line Progressive (640 × 480 active pixels) 36″ display monitor. The prototype has been demonstrated using various conventional and flat CPTs. Genesis Microchip has developed this sinusoidal deflection DTV/HDTV CPT/CRT chassis and a digital deflection controller chip using bi‐directional sinusoidal horizontal scanning. The critical video processing and 8 GHz multi‐clock generator needed for a finished chip has been designed, reduced to silicon and used in production chips for over two years in other products for FPD & TV.

Continuous scanning laser Doppler vibrometer for mode shape analysis

The vibration mode shape measurement technique utilizing a continuous scanning laser Doppler vibrometer (SLDV) is addressed. Continuous scanning capability is added to the conventional discrete laser Doppler vibrometer by reflecting the laser beam on the surface of the object using two oscillating mirrors. Bow scanning resulting from the proposed scanning mechanism is compensated by controlling the two mirrors. If a continuous sinusoidal scanning method is used, it can be shown that the velocity output signal from the SLDV is modulated to give the spatial velocity distribution in terms of coefficients that are obtained from the Fourier transformation of the time-dependent velocity signal. Using the Chebyshev series form, the analysis of vibration mode shape techniques for 2-D scanning is presented and discussed. The performance of the proposed SLDV is presented using the experimental results of the vibration mode shape of a plate.

A Continuous Scanning Laser Doppler Vibrometer for Mode Shape Analysis

The vibration mode shape measurement technique utilizing a continuous scanning laser Doppler vibrometer(SLDV) is addressed in this paper. The continuous scanning capability is added to the conventional laser Doppler vibrometer by reflecting the laser beams on the surface of the object using two oscillating mirrors. The bow scanning resulted from the proposed scanning mechanism is compensated by controlling the two mirrors. If a continuous sinusoidal scanning method is used, it can be shown that the velocity output signal from the SLDV is modulated to give the spatial velocity distribution in terms of coefficients which are obtained from the Fourier transformation of the time dependent velocity signal. Using the Chebyshev series form, the analysis of the vibration mode shape techniques for two dimensional scanning is presented and discussed. The performance of the proposed SLDV is presented using the experimental results of the vibration mode shape of a plate.

Sinusoidal wavelength-scanning interferometer with a superluminescent diode for step-profile measurement

In sinusoidal phase-modulating interferometry an optical path length (OPD) larger than a wavelength is measured by detection of sinusoidal phase-modulation amplitude Z(b) of the interference signal that is produced by sinusoidal scanning of the wavelength of a light source. A light source with a large scanning width of wavelength is created by use of a superluminescent laser diode for the error in the measured value obtained by Z(b) to be smaller than half of the central wavelength. In this situation the measured value can be combined with a fractional value of the OPD obtained from the conventional phase of the interference signal. A sinusoidal wavelength-scanning interferometer with the light source measures an OPD over a few tens of micrometers with a high accuracy of a few nanometers.

MODAL TESTING USING A SCANNING LASER DOPPLER VIBROMETER

A number of vibration mode-shape measurement techniques are described in which the measurement point of a laser Doppler vibrometer (LDV) is continuously scanned over the surface of a sinusoidally excited structure. The LDV vibration output is an amplitude-modulated sine wave and mode shapes, defined along the scan line, may therefore be established by demodulation. Alternatively, in the frequency domain, the LDV output is a line spectrum, with sidebands centred on the excitation frequency and spaced at the scan frequency. The sideband amplitudes give series coefficients for the mode shape defined along the scan line—Fourier coefficients for a circular scan or, via a simple transform, polynomial coefficients for a sinusoidal straight line or area scan. Useful measurements can also be made, directed at a single point on a structure: a small-diameter circular scan will give the angular vibration of the structure at the centre of the circle; a conical scan, produced with a short-focus lens, will measure the translational vibration at the point of focus, in magnitude and direction.

Real-time image linearization in a rotating prism-pair scanning system by using laser-diode encoding techniques

Rotating prism-pair scanning is a conventional method used to achieve large angles with a straight-line configuration. A disadvantage of prism scanners for line scanning is that the sinusoidal scan produces a non-linear image. We use a laser-diode encoding technique to carry out real-time image linearization in a rotating prism-pair scanning system. In this study, we report on the results obtained in a thermal image system.

Measurement of Translational and Angular Vibration Using a Scanning Laser Doppler Vibrometer

An experimental procedure for obtaining angular and translational vibration in one measurement, using a continuously scanning laser Doppler vibrometer, is described. Sinusoidal scanning, in a straight line, enables one angular vibration component to be measured, but by circular scanning, two principal angular vibrations and their directions can be derived directly from the frequency response sidebands. Examples of measurements on a rigid cube are given. Processes of narrow-band random excitation and modal analysis are illustrated with reference to measurements on a freely suspended beam. Sideband frequency response references are obtained by using multiplied excitation force and mirror-drive signals.

Measurement of Translational and Angular Vibration Using a Scanning Laser Doppler Vibrometer

An experimental procedure for obtaining angular and translational vibration in one measurement, using a continuously scanning laser Doppler vibrometer, is described. Sinusoidal scanning, in a straight line, enables one angular vibration component to be measured, but by circular scanning, two principal angular vibrations and their directions can be derived directly from the frequency response sidebands. Examples of measurements on a rigid cube are given. Processes of narrow-band random excitation and modal analysis are illustrated with reference to measurements on a freely suspended beam. Sideband frequency response references are obtained by using multiplied excitation force and mirror-drive signals.

A rapidly scanning two-velocity component laser Doppler velocimeter

A two-velocity-component directionally sensitive fringe-type rapidly scanning laser Doppler velocimeter (RSLDV) is described, which scans the measurement volume in a direction perpendicular to the optical axis of the transmitting optics and normal to the test flow floor and measures the velocity components perpendicular to the optical axis. Scan rates of up to 300 Hz are possible over 75 mm using a sinusoidal scanning of the position versus time. The RSLDV was designed to permit space-time velocity correlations along a vertical line scan. To illustrate the use of this instrument, some results are presented from measurements performed in the highly turbulent complex three-dimensional flow in front of a wing-body junction.

Photoacoustic Densitometry of Ovalbumin on Nitrocellulose Sheet by Imaging by Fast Laser Beam Scanning

Photoacoustic densitometry by using a fast laser beam with sinusoidal scanning was conducted. The signal distortion was improved by using a sinusoidal scanning system combined with a Bessel high-pass filter. However, small distortions were found to remain in the densitograms, compared with those produced by conventional light scanning. Ovalbumin was two-dimensionally electrophoresed, followed by blotting on a nitrocellulose sheet. The signal intensity of ovalbumin on a nitrocellulose sheet was about 5-times greater than that on polyacrylamide gel. The reproducibility (RSD) of measurements for ovalbumin on four different nitrocellulose sheets was in the 8-15% range. However, the value was less than 5% for measurements of ovalbumin on the same plate. The detection limit of ovalbumin was about 150ng. Ovalbumin, 1.67μg of which was spiked in calf serum, was almost recovered by the method.