Unwanted Image Research Articles

Speckle-illuminated fluorescence confocal microscopy, using a digital micro-mirror device

An implementation of a speckle-illuminated fluorescence confocal microscope using a digital micro-mirror device (DMD) is described. The DMD not only projects a sequence of imaged binary speckle patterns onto the specimen at a very high frame rate but also operates as a spatial light modulator to perform real-time optical data processing. Frame averaging is accomplished by CCD charge accumulation during a single exposure. The recorded time-averaged image is a confocal image plus an unwanted non-confocal image which can be removed by recording a separate image. Experimental results with image acquisition within a fraction of a second are shown. Images of a thin biological sample are also shown to demonstrate practical application of the technique.

Integrated Calibration and Management of Color, Tone, and Image Structure in a Digital Intermediate System

As the number of feature films processed with digital intermediate systems has increased, so has the need for more efficient methods for reducing system variability and preserving creative intent. Unwanted color, tone, and image structure distortions might be introduced during digitization or subsequent image-processing operations. The presence of this variability makes visually seamless intercutting of source material much more difficult. This paper describes a system and method for automatically creating calibration functions that convert color, tone, and image structure into a common exchange space. After this calibration, the system provides features that allow the user to accurately preserve the color, tone, and image structure of existing films or create custom renderings that are faithfully reproduced when the images are displayed on film or digital devices.

Full-field Thermal Deformation Measurements in a Scanning Electron Microscope by 2D Digital Image Correlation

Using recently developed methods for application of a nano-scale random pattern having high contrast during SEM imaging, baseline full-field thermal deformation experiments have been performed successfully in an FEI Quanta SEM using 2D-DIC methods. Employing a specially redesigned commercial heating plate and control system, with modified specimen attachment procedures to minimize unwanted image motions, recently developed distortion correction procedures were shown to be effective in removing both drift and spatial distortion fields under thermal heating. 2D-DIC results from heating experiments up to 125°C on an aluminum specimen indicate that (a) the fully corrected displacement components have nearly random variability and a standard deviation of 0.02 pixels (≈25 nm at 200× and ≈0.5 nm at 10,000×) in each displacement component and (b) the unbiased measured strain fields have a standard deviation ≈150 × 10−6 and a mean value that is in good agreement with independent measurements, confirming that the SEM-DIC based method can be used for both micro-scale and nano-scale thermal strain measurements.

Effective Bandwidth SF-CW SAR increase using frequency agility

The use of a frequency-agile waveform is proposed as a way of providing significantly increased bandwidth for a stepped frequency continuous wave (SF-CW) SAR, than is provided by traditional imaging schemes. The range resolution is set by the bandwidth of the transmitted waveform, and is built up as a set of monotonically increasing stepped frequencies. As these frequencies are sampled sequentially, a constraint with SF-CW waveforms is the time restriction available to build up the bandwidth, imposed by the spatial sampling requirements along the aperture to avoid grating-lobe effects. To address this problem, an approach is outlined which allows the frequency spectrum to be greatly undersampled to provide a greater effective bandwidth. It was found that randomizing the set of frequencies omitted from sweep to sweep allowed significant thinning before the appearance of significant unwanted image artifacts due to the under-sampling. This scheme allows great flexibility in the choice of bandwidths that can be realized for a particular imaging scenario. Their application is considered from the point of view of operation from UAV SAR platforms

The effects of mismatch in Gm-C polyphase filters

Based upon state-space representation, the effects of component mismatch in a complex (or polyphase) Gm-C filter are examined. It was found that the effects of component mismatch in this kind of filter are twofold. The first is that it will distort the filter's frequency response. The second and probably more severe consequence is the crosstalk in which the unwanted image signal is leaked into the passband frequencies, interfering with the wanted signal of the selected channel. A simulation method of a polyphase filter is also presented, and simulation results based on Monte Carlo analysis are given.

Two-step channel selection-a novel technique for reconfigurable multistandard transceiver front-ends

This paper starts with a review of the prevailing channel-selection techniques utilized so far in the design of wireless transceiver analog front-ends before describing a novel two-step channel-selection technique, which handles the traditionally unwanted image, in radio frequency-to-intermediate frequency (RF-to-IF) or IF-to-RF frequency conversion, as a useful adjacent channel of the desired one, and selects deliberately either of them from IF to baseband (or baseband to IF). Thus, one more channel-selection possibility is created for both low-IF receivers and two-step-up transmitters. The consequential benefits of introducing channel selection at IF consist of two. First, many design specifications (such as phase noise and settling time) of the RF frequency synthesizer and local oscillator can be substantially relaxed. Second, a low-IF/zero-IF reconfigurable receiver and a direct-up/two-step-up reconfigurable transmitter can be synthesized to match better with narrowband-wideband-mixed multistandard systems. The operating principles of such architectures are presented in easy-to-understand complex-signal spectral-flow illustrations, and their practicability is demonstrated in the design of a Bluetooth/IEEE 802.11FH/HomeRF multistandard receiver. SPECTRE simulation results validate the reconfigurable functionalities mainly implemented by a triple-mode channel-select filter and a multifunctional sampling-mixer scheme.

Frequency offset and I/Q imbalance compensation for direct-conversion receivers

Two types of wireless system imperfections, namely, frequency offset and in-phase/quadrature (I/Q) imbalance, are addressed in this paper. The I/Q imbalance in radio frequency (RF) direct-conversion not only introduces an unwanted in-band image interference but also degrades the accuracy of carrier estimation. Toward this end, we propose a pilot-based scheme for both frequency offset and I/Q imbalance compensation at the baseband. A low-cost nonlinear least squares (NLS) frequency estimator robust to the I/Q imbalance is developed. Also derived is an I/Q imbalance compensation structure that consists of two stages: a finite impulse response (FIR) filter that compensates the frequency dependent imbalance; and an asymmetric phase compensator that corrects the frequency independent error. The compensation coefficients are optimized by exploiting the phase rotation embedded in the pilot symbols. Both computer simulations and experiment results verify the effectiveness of the proposed scheme in various I/Q imbalance scenarios.

Dependence of the lateral ion transport on the driving frequency in nematic liquid crystal displays

The presence of ions in a liquid crystal (LC) influences the transmission characteristics of LC displays. These ions follow the electric field perpendicular to the electrodes and move back and forth under the influence of the ac field. Because of their charge, they can distort the electric field, which leads to transmission changes. Recently it was discovered that due to the LC anisotropy, ion motion parallel with the plane of the electrodes (perpendicular to the electric field) is also possible, even without lateral fields. After driving a pixel for a long time, the ions will accumulate at one pixel edge, which leads to unwanted image artifacts. In this paper, we investigate the frequency dependence of the lateral ion transport in twisted nematic liquid crystal displays at high and low ion concentrations, different ion mobilities, and LC rotational viscosities, for a fixed voltage just above the LC threshold.

In vivo fluorescence imaging using two excitation and/or emission wavelengths for image contrast enhancement

Steady-state fluorescence imaging can be used in conjunction with selective exogenous or endogenous fluorescent compounds for the diagnosis of skin lesions, for example cancer. Depending on the excitation and emission properties of the fluorescent compound used, various excitation and/or emission wavelengths can be chosen in order to allow fluorescence imaging. Unwanted background signals such as autofluorescence and scattering can decrease the image quality and, hence, the diagnosis potential of this imaging method. We have used an inexpensive dual excitation and/or emission wavelength approach in order to suppress the unwanted background signal and allow contrast enhanced fluorescence imaging. One excitation and/or emission wavelength is at the corresponding maximum of the fluorescent compound, while the second is at a nearby excitation/emission minimum. The first image contains the emission from the fluorescent compound used combined with the signal from the unwanted background. The second image provides an image of just the unwanted background signal. The difference of both images taken, thus gives a contrast enhanced image of the skin lesion. The method relies on the assumption that the background signal does not change significantly due to the small changes in wavelength for excitation or emission. Image ratio methods have already been applied towards diagnosis of basal cell carcinomas after administration of aminolevulinic acid-induced protoporphyin IX. In this study, we describe in vivo measurements in mice where the second image, usually the background signal only, contains new unwanted image data. This simple method can successfully resolve the desired image, thus demonstrating the versatility of the image processing procedure.

In-line electron holography with an atomic focuser source

The resolution that may be achieved in an image formed by reconstruction from an in-line electron hologram, without aberration correction, is governed by the source size. Computer simulations show that ultrahigh resolution, of better than 0.05 nm for 100 keV electrons, may be possible if the electron source is a crossover formed at the exit face of a thin atomic-focuser crystal when electrons from a beam focused in a scanning transmission electron microscope (STEM) instrument are channeled along a line of atoms through the crystal. Simulations also show that, because of the channeling effect, the resolution of the reconstructed image is not degraded by translations or oscillations of the STEM beam by 0.1 nm or more. We suggest a scheme for removing the unwanted background and conjugate image from the reconstructed image by combining the in-line holography with an off-axis mode.

Spatial Normalization of Lesioned HMPAO-SPECT Images

We investigated the effect of nonlinear alignment on SPECT images with lesions. Linear alignment produces reliable results but the introduction of nonlinear methods can improve matching by accounting for global brain shape. We examined the hypothesis that nonlinear alignment can introduce unwanted image distortions when lesions are present. We set out to quantify possible distortions by constructing artificial lesions in order to obtain images with controllable characteristics. We examined the use of basis functions (in SPM96 and SPM99) and other nonlinear models (in AIR3.08) designed to achieve optimum alignment between image and template. We found that the use of models with high degrees of nonlinearity will result in unwanted deformations and that the safest way to align images with lesions is to use 12-point linear affine transformations. Masking was examined as a remedy to distortions caused by nonlinear methodologies and produced significantly improved results.

Precise interpolation for band‐limited digital signals based on sampling theorem incorporated with window functions

AbstractThis paper proposes an interpolation method called the “window function method” in which the sampling theorem and the window functions are combined. The cause of the generation of the interpolation error is the folding distortion due to the multiplication of the time‐limited window to the input signal. The conditions to enable precise interpolation are that the functions are continuous, the windows with large spectral decays in the side lobes are normalized such that the window function values are unity at the interpolation points, and the main lobe width is set to an optimum. When the interpolation precision is compared with those by other interpolation methods, the present one is about the same as that in the “filter method” (the conventional method using the filter to eliminate the unwanted image components) but is somewhat poorer than that in the “least RMS error method” (theoretical limit) if Kaiser–Bessel windows are used. However, the number of input signal data to obtain the same interpolation precision is larger only by 10%. Hence, the operating time to obtain the required interpolation precision is close to optimum. The calculation of the coefficients needed for interpolation is basically a simple substitution and can avoid a design of higher‐order filters (in the filter method) and solution of the ill‐conditioned simulation equations (in the least RMS error method). © 2001 Scripta Technica, Electron Comm Jpn Pt 3, 84(7): 63–77, 2001

Recent advances in fuzzy techniques for image enhancement

With the continued growth of multimedia and communications systems, the instrumentation and measurement fields have seen a steady increase in the focus on image data. Developing tools and techniques to enhance the quality of image data plays a very relevant role. Enhancement of noisy images, however, is not a trivial task. The filtering action should distinguish between unwanted noise (to be removed) and image details (to be preserved or possibly enhanced). Nonlinear filters based on fuzzy systems effectively complete this task, outperforming conventional methods. Fuzzy reasoning is very well suited to model the uncertainty that typically occurs when both noise cancellation and detail preservation represent very critical issues. Since 1992, the number of different approaches to fuzzy filtering has been progressively increasing. The goal of this article is to explain the basic principles of fuzzy filtering, focusing on a selection of the most significant methods.

In-line soft-x-ray holography: the unwanted image

Recent improvements in computer technology remove the limitations in the Bragg-Rogers method of eliminating the unwanted image from in-line holography.

A VISION SYSTEM FOR MANUFACTURING APPLICATIONS UNDER MODERATELY UNCONSTRAINED CONDITIONS

An industrial vision system capable of extracting the position, orientation, and identification of non-overlapping parts in 2-D scenes subject to moderately unconstrained conditions is presented, Typical scenes exhibit non-homogeneous object surfaces, transparency, shadows and specular reflections. System requirements include recognition of partial and unconnected objects, independent of object scale and rotation, to counterbalance incomplete and imperfect image segmentations that result from these conditions. Part of the approach consists of removal of unwanted image data. Shadows that would otherwise prevent detection of high-discriminant features arc identified and removed. Redundancy is included in feature space to compensate for imprecise feature measurements. Results for a typical industrial application are presented.

Line Detection in Noisy and Structured Backgrounds Using Græco-Latin Squares

In this paper new methods for detection of line targets in digital images using multiple-way Analysis of Variance (ANOVA) methods based on the Græco-Latin square (GLS) are developed and demonstrated. After presentation of the underlying statistical theory upon which the GLS is based, the philosophy of using ANOVA methods in pattern recognition problems is illustrated by one-way and two-way models. The GLS detectors are then described in detail and their performance demonstrated. The detectors are not only capable of detecting lines of different direction, but their complexity also can be used to estimate and remove some types of unwanted image structure. Also proposed is an adaptive ANOVA method for line detection, which uses information contained in the GLS statistics to eliminate unnecessary estimation of some of the structure parameters and again improve the power of the detector. The problem of false alarms in regions of the image containing sharp gray-level discontinuities also is addressed, and adjustments are made to the algorithms for their suppression.

Automated lanes detection and comparison of bacterial electrophoretic protein fingerprints using fast Fourier transformation

A method of computer-automated analysis of bacterial fingerprints produced by electrophoresis of proteins in a one-dimensional slab gel system is described. Proteins were visualized by silver staining, Western blotting, or autoradiography. Gels were recorded with a CCD camera, and after initial manual removal of the unwanted image margins, track margins were identified and extracted and a normalized trace was produced automatically using Fourier routines to smooth plots required for this process. Normalized traces were then compared by Fourier correlation after application of a high-pass step filter.

XVI.—Two Hologram Methods in Diffraction Microscopy

SynopsisThe Bragg two-hologram method for eliminating the unwanted image in Diffraction Microscopy is here thoroughly examined. It is shown to be of general validity for objects containing both amplitude and phase-contrast terms.Other two-hologram methods are briefly discussed. In principle any two sufficiently distinct holograms may be used, but the Bragg 2:1 focal ratio is the simplest. The pair of holograms at ±f is also of interest, since it allows moderate degrees of phase-contrast and amplitude-contrast terms in the original object to be separated. A “three-wavelength” technique for obtaining the Bragg records is briefly outlined.

Elimination of the unwanted image in diffraction microscopy.

DURING a discussion at Cambridge, the idea was put forward that it might be possible to eliminate the effects of the unwanted image in diffraction microscopy by taking a subsidiary hologram and subtracting it from the reconstruction. In Gabor's method1,2 a single hologram is used, and he has shown how two images are formed, when coherent light traverses this hologram, so that the image in sharp focus has as a background a confused pattern due to the other image. In a recent note in Nature3, an elementary explanation of the origin of these two images is given; the confusion they cause is the necessary price paid for the loss of information as to the phase of the disturbance in the plane in which the main hologram is taken. But in a coherent beam, if the amplitude and phase are known over a surface 1, they can be calculated over a subsequent surface 2 by Huyghens's principle. In general, the two patterns differ from one another, yet they both contain essentially the same information. This opens up the possibility that the confusion due to loss of information about phase in one plane, the main hologram plane, may be cleared up by measuring the amplitude in another plane which we call that of the auxiliary hologram. In other words, two suitably separated amplitude patterns will do service for a single pattern giving both amplitude and phase. While one hologram gives two images, two holograms can be made to give one image.

The Removal of an Unwanted Image Layer from one side of Double-coated X-ray Film Negatives

The Removal of an Unwanted Image Layer from one side of Double-coated X-ray Film Negatives