Optimum Focal Point Research Articles

Edge Detection Based Autofocus Algorithm to Detect Accurate Camera Working Distance

In the last 10 years, industrial image processing has been used in many areas such as automotive, medicine and aviation. Especially for sensitive measurement applications, camera control systems are preferred due to their speed and quality advantages. In this study, a method is proposed to determine the optimum camera position at the image acquisition phase for industrial cameras. In the proposed approach, images are captured while the camera and telecentric lens, which are connected to the servo motor, are moving up and down. The edge informations of the captured images are extracted in the x and y directions and the amplitude value is calculated. Then, meaningful and meaningless edge information at each motor position is found with a median-based approach. Finally, the sharpness of the images are arranged by statistical analysis and the optimum focal point for the camera is found. Sobel, Robert and Prewitt Filters were applied to determine the best method for extracting edge information. Measurements were performed on the workpieces using camera positions where the focus was optimum for each method. According to the results, it has been observed that the camera position, which produces the closest result to the real values, is obtained from the focus determined by the Sobel Filter. The proposed method is leaded to researchers to provide automatic focus for camera control systems.

3D-Printed Inhomogeneous Dielectric Lens Antenna Diagnostics: A Tool for Assessing Lenses Misprinted Due to Fabrication Tolerances

It is difficult to manufacture 3D-printed voxelized inhomogeneous lens antennas exactly to specifications due to fabrication tolerances. Here, we define fabrication tolerances as the sum total of voxelization errors plus printing errors. In this article, we show that the aperture phase is a sensitive function of these fabrication tolerances. A conservative estimate of ±0.127-mm error in the amount of material specified to be printed leads to a 1.63° phase error per cell. This error accumulates, as a voxelized lens is generally made of many cells. We present a novel method for diagnosing misprinted lenses and reverse engineering the true permittivity inhomogeneity profile of a lens fabricated within specified tolerances. The technique is based on an inverse-scattering tool that uses geometrical optics (GO) and particle-swarm optimization (PSO). Once the actual permittivity profile is found with our method, a new optimal focal point can be calculated by using the same GO-PSO optimization tool to determine where to best feed the misprinted lens. Both numerical and measured examples are given to validate the process. The measured results show that at the new optimal focal point, the measured directivity has been restored to that of the original design specifications.

Wide-Scan MSC-AFTSA Array-Fed Grooved Spherical Lens Antenna for Millimeter-Wave MIMO Applications

A new three-element multi- sin -shape corrugated antipodal Fermi tapered slot antenna (MSC-AFTSA) array integrated with a grooved spherical (GS) lens operating at 57–64 GHz is introduced. Multicorrugated patterns are implemented to obtain better matching performance when the antenna feeds the GS lens with broadband coverage. An implemented design for grooving the lens profile presents a new principle to obtain an optimum focal point feed using the tapered slot antennas. This technique gives more freedom to enhance the $E$ - and $H$ -plane characteristics with a gain of 20 dB, radiation efficiency of 83% at 60 GHz, and wide angle multibeam coverage. It is a relatively small spherical-lens antenna with three feeds of MSC-AFTSA array, $44.2 \times 51.6 \times 25.4$ mm3 in size. There is a good agreement between calculated and measured results. The proposed antenna prototype with its wide-scan performance is suitable for broadband multiple-input–multiple-output communication systems operating at millimeter-wave bands.

Beam-transport optimization for cold-neutron spectrometer

We report the design of the beam-transport system (especially the vertical geometry) for a cold-neutron disk-chopper spectrometer AMATERAS at J-PARC. Based on the elliptical shape, which is one of the most effective geometries for a ballistic mirror, the design was optimized to obtain, at the sample position, a neutron beam with high flux without serious degrading in divergence and spacial homogeneity within the boundary conditions required from actual spectrometer construction. The optimum focal point was examined. An ideal elliptical shape was modified to reduce its height without serious loss of transmission. The final result was adapted to the construction requirements of AMATERAS. Although the ideas studied in this paper are considered for the AMATERAS case, they can be useful also to other spectrometers in similar situations.

Not all drift feeders are trout: a short review of fitness-based habitat selection models for fishes

Currently, there are few mechanistic fitness-based habitat selection models for stream fishes and most models used by management agencies focus on physical habitat alone. In this review, I describe the historical development and the status of mechanistic, fitness-based, habitat selection models for both water column (i.e., drift-feeding) and benthic stream fishes focusing on North America. Although the majority of drift feeders are not salmonids, most mechanistic habitat selection models have been developed and tested only in this group of fishes, likely due to their substantial economic importance. I review the fitness-based microhabitat selection model of Grossman et al. (Ecol Fresh Fish 11:2–10, 2002), which has been tested in both a salmonid and multiple cyprinid species. The model predicts optimal focal point velocities for drift feeders based on prey capture success–velocity relationships and does not include physiological costs, which are logistically difficult to quantify. In addition, I discuss mechanistic, fitness-based models used to predict microhabitat (i.e., patch) selection in benthic fishes. For both basic scientific and management/conservation perspectives, it is important to quantify habitat choice in fishes using mechanistic, fitness-based criteria.

Optimum Focal Point of a Paraboloidal Reflector Antenna With an Omnidirectional Radiative Source

A paraboloidal reflector antenna is useful for enhancing the directivity of a feed antenna with a low directivity. In this letter, we investigate a paraboloidal reflector antenna that has an ultrawideband (UWB) omnidirectional radiative source as the focal feed. To obtain the optimized focal length f for a given diameter D of the paraboloidal reflector antenna, we employ a simple relation between f and D, which can reduce the spreading loss of the source field while maintaining the aperture field uniformity. Simulation results show that the f values obtained from the above relation can maximize the far voltage-a well-known figure of merit for UWB applications.

SETTING AN OPTIMAL IMAGE PARAMETER IN AN ULTRASOUND SYSTEM

Embodiments of setting an optimal image parameter for obtaining an optimal ultrasound image are disclosed. In one embodiment, by way of non-limiting example, a processing unit is configured perform an image process upon an ultrasound image to thereby detect a center of a blood vessel from the ultrasound image. The processing unit is configured to set the center of the blood vessel as an optimal focal point position. The processing unit is configured to calculate a plurality of steering angles, a plurality of transmit (Tx) frequencies and a plurality of sound speeds. The processing unit is further configured to form a plurality of ultrasound images corresponding to each of the steering angles, the Tx frequencies and the sound speeds based on the ultrasound data, detect a signal to noise ratio (SNR), a number of edge points of the blood vessel and a contrast difference between pixels for each of the second ultrasound images to thereby detect an optimal steering angle, an optimal Tx frequency and an optimal sound speed.

Imaging Technique Explored As Depression Treatment

Imaging Technique Explored As Depression Treatment

Focused beam reflectance technique for in situ particle sizing in wastewater treatment settling tanks

AbstractDue to the complexities involved with measuring activated sludge floc size distributions, this parameter has largely been ignored by wastewater researchers and practitioners. One of the major reasons has been that instruments able to measure particle size distributions were complex, expensive and only provided off‐line measurements. The Focused Beam Reflectance Method (FBRM) is one of the rare techniques able to measure the particle size distribution in situ. This paper introduces the technique for monitoring wastewater treatment systems and compares its performance with other sizing techniques. The issue of the optimal focal point is discussed, and similar conclusions as found in the literature for other particulate systems are drawn. The study also demonstrates the capabilities of the FBRM in evaluating the performance of settling tanks. Interestingly, the floc size distributions did not vary with position inside the settling tank flocculator. This was an unexpected finding, and seriously questioned the need for a flocculator in the settling tank. It is conjectured that the invariable size distributions were caused by the unique combination of high solids concentration, low shear and zeolite dosing. Copyright © 2004 Society of Chemical Industry

Choice of the Focal Point Position Using Lasentec FBRM

AbstractThe Focused Beam Reflectance Measurement (FBRM) technique provides on‐line and in situ information about the chord length distribution (CLD) of a population of particles in dispersion. The effect of changing the focal point position on the measured CLD is experimentally analyzed by carrying out single particle FBRM determinations in both pure water and a dispersion of fines. The results allow some general conclusions to be drawn about optimal focal point positions.

Measurement and Analysis of Vibrations on Surface of Phantom Induced by Piezoelectric Extracorporeal Shock Wave Lithotripter

We investigated the sound radiated from an object, induced by a piezoelectric extracorporeal shock wave lithotripter (ESWL). However, it was found that more direct measurement is necessary to analyze the sounds in piezoelectric ESWL. Therefore, we investigate the vibrations of a phantom, which are directly measured using laser Doppler velocimetry. The results show that the peak frequency in the power spectrum shifts as the number of shots increases from high frequency to low frequency. The previous results are confirmed by detecting the characteristic peaks obtained from the vibrations of bronze models. The bronze models are used to simulate the phantom during the breaking process. It is found that it is more difficult to make the models vibrate exactly at the focal point than above or below the focal region. These results will be applied to the monitoring of the breaking process and the choice of the optimum focal point on the calculus.

Particle Size Determination by Laser Reflection: Methodology and problems

AbstractThe particle size distribution of crystalline solids has progressively become a key parameter in manufacturing processes, as important as chemical purity. Among the particle size determination and counting systems available on the market, very few offer the possibility of continuous in situ monitoring of the particle size evolution during crystallization. For this reason, much interest has been aroused by the appearance of the Par Tec 100, patented by Laser Sensor Technology [1, 2]. A study has been carried out in a stirred vessel to verify the precision and reproducibility of particle size measurement and elucidate the influence of experimental parameters on data accessible with this instrument. Optimum reproducibility has logically been achieved by fixing the highest possible cycle time and taking the mean of several cycles. Determinations with the Par Tec 100 are influenced variously, according to whether they relate to the total number of particles counted or to the mean size. Thus, the number of counts measured by a particle size probe largely depends on the operating conditions and more particularly on the hydrodynamic conditions, solvent, temperature and focal point position. Its dependence relative to the concentration of the solid in suspension is normal and linear for a solid and for a given monodisperse sample. To establish the relationship between the number of counts and the population density would therefore necessitate delicate calibration on a case‐by‐case basis. The mean size determined does not depend on suspension homogeneity, provided that the stirring speed is sufficient for a statistically significant total count. On the other hand, for a given sample, a displacement of the focal point can lead to considerable variations in the size determined. The optimal focal point position for small sizes is in fact highly sensitive. Lastly, the optimal position of the focal point is considerably dependent on the true size of the particles, which means that this counter is unsuitable for the precise analysis of a dispersed sample since each particle size class would require a different setting of the focal point. In addition, the sizes determined, irrespective of the products studied, appear to be underestimated for large particles and over estimated for small particles.

Microhabitat Models of Large Drift-Feeding Brown Trout in Three New Zealand Rivers

We examined summer habitat use by 189 drift-feeding brown trout Salmo trutta, 45–65 cm long (fork length), by measuring substrate, depth, mean velocity, focal point velocity use, and adjacent velocity into which fish were feeding in three New Zealand rivers. We compared habitat used with habitat available (simulated by hydraulic modeling), and we derived habitat use, habitat preference, and logistic regression models of habitat selection. Focal points usually were associated with large substrate components including bedrock projections, boulders, and large cobbles. Depths between 0.67 and 0.86 m were most commonly used by brown trout but the preferred depth was 1.0 m. Mean velocities between 0.38 and 0.48 m/s were the most commonly used, but preferred mean velocities were 0.05 m/s higher. Optimal focal point velocities, 0.19–0.28 m/s, were lower than mean velocities. Vertical and lateral velocity shears were calculated as measures of the velocity differentials over which fish were feeding. The velocity shears most commonly used by brown trout were between 0.50 and 0.65 m/s per meter for vertical shear and 0.02 and 0.06 m/s per meter for lateral shear. Those most preferred by brown trout were between 0.50 and 1.20 m/s per meter for vertical shear and between 0.06 and 0.26 m/s per meter for lateral shear. Depth, mean velocity, and substrate were selected independently of each other. Significant differences between rivers were found for the use of substrate, depth, focal point velocity, mean velocity, and lateral velocity shear. Depth and mean velocity were consistently significant variables in logistic regression models of habitat selection, accounting for 33–85% of the explained deviances. Large substrate components accounted for 47% of the explained deviance in one river. Lateral and vertical velocity shear together accounted for 15–27% of the explained deviances. Logistic regression and joint habitat preference models were better predictors of suitable habitat in the rivers for which they were developed than were joint habitat use models. However, joint habitat use models may be more general, because, unlike logistic regression and joint habitat preference models, the predictive success of transferred joint habitat use models was similar to that of models tested on the river for which they were developed. Combined-river habitat use, habitat preference, and logistic regression models are presented for general habitat management applications when habitat criteria are not available for specific rivers.

An Energetic Model of Microhabitat Use for Rainbow Trout and Rosyside Dace

We constructed an energetic model to determine the optimal focal point current velocity (i.e. microhabitat) for rainbow trout (Oncorhynchus mykiss) and rosyside dace (Clinostomus funduloides) in Coweeta Creek, a fifth—order stream in North Carolina, USA. Energetic costs were evaluated by quantifying the metabolic expenditure associated with swimming at a given velocity. We estimated bebefits by measuring potential energetic gains of feeding at a given velocity. This included estimates of the ability of the fish to capture prey at different current velocities as well as etimates of the frequency and the energy content of drifting prey at various velocities. We derived separate models for small (53—70 mm SL [standard length]) and medium (71—125 mm SL) trout, and medium (47—52 mm SL) and large (53—70 mm SL) dace for all seasons, deriving net energy gain as a function of current velocity. We predicted fishes would occupy velocities at which net energy gain was maximized. Predicted velocities were compared with those utilized by fishes inhabiting Coweeta Creek. Optimal velocities predicted by energetic models ranged from 7.7 to 22.1 cm/s, and closely matched actual velocity use (average deviation = 2.6 cm/s). Prey capture success appeared to be the most important component in the models. Consequently, we constructed models based solely upon aspects of capture success; the average deviation from veolocity use with these models was only 1.8 cm/s. Thus, the ability of dace and trout to capture prey at varying velocities appears to be the dominant factor affecting microhabitat selection in these species.

The analysis of deployable umbrella parabolic reflectors

The radiation characteristics of an umbrella-type reflector are studied in detail. When the supporting ribs of the quasiparabolic reflector are parabolic in shape and the surface between any two adjacent ribs is the surface of a parabolic cylinder, the deviation of the surface from the true parabolic shape has the effect of spreading the focal point of the parabolic reflector into a focal region, the limits of which can be calculated from the knowledge of the reflector parameters. The best feed position can be accurately determined by requiring that the phase error over the surface be minimized. For the cosine to the power <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</tex> illumination, numerical results showing the gain degradation, the shift in optimum focal point, and the change in secondary patterns, due to the deviation of the reflector surface from the true parabolic surface, are presented.

Comparative Study of Three Types of Cylindrical Reflectors for Narrow Beam Sonar Transducers

This paper presents a comparison between circular, parabolic, and elliptic cylinder sections used in large aperture reflector systems designed to achieve acoustic beamwidths of a fraction of a degree. An analytic analysis of each type reflector shows the shift in optimum focal point and the phase relations at the focal element as a function of range from a test point on the axis in the near field of the transducer system. Depth of focus due to the phase discrepancies in the focal region is also derived for the three types of reflectors. Experimental results show that near field focusing is possible and the predicted shift in optimum focal point is verified for the parabolic and elliptic reflectors. Aperture shading using both reflector masking and focal element beam control is described in which minor lobe levels are suppressed 18 db below the main beam. Experimental results illustrating several degrees of lobe suppression are shown.