Zoom Factor Research Articles

A micro-optical system for endoscopy based on mechanical compensation paradigm using miniature piezo-actuation

The goal of the study was to investigate the feasibility of a novel miniaturized optical system for endoscopy. Fostering the mechanical compensation paradigm, the modeled optical system, composed by 14 lenses, separated in 4 different sets, had a total length of 15.55mm, an effective focal length ranging from 1.5 to 4.5mm with a zoom factor of about 2.8×, and an angular field of view up to 56°. Predicted maximum lens travel was less than 3.5mm. The consistency of the image plane height across the magnification range testified the zoom capability. The maximum predicted achromatic astigmatism, transverse spherical aberration, longitudinal spherical aberration and relative distortion were less than or equal to 25μm, 15μm, 35μm and 12%, respectively. Tests on tolerances showed that the manufacturing and opto-mechanics mounting are critical as little deviations from design dramatically decrease the optical performances. However, recent micro-fabrication technology can guarantee tolerances close to nominal design. A closed-loop actuation unit, devoted to move the zoom and the focus lens sets, was implemented adopting miniaturized squiggle piezo-motors and magnetic position encoders based on Hall effect. Performance results, using a prototypical test board, showed a positioning accuracy of less than 5μm along a lens travel path of 4.0mm, which was in agreement with the lens set motion features predicted by the analysis. In conclusion, this study demonstrated the feasibility of the optical design and the viability of the actuation approach while tolerances must be carefully taken into account.

Vectorial boundary-based sub-pixel mapping method for remote-sensing imagery

This article presents a vectorial boundary-based sub-pixel mapping (VBSPM) method to obtain the land-cover distribution with finer spatial resolution in mixed pixels. With inheritance from the geometric SPM (GSPM), VBSPM first geometrically partitions a mixed pixel using polygons, and then utilizes a vectorial boundary extraction model (VBEM), rather than the rasterization method in GSPM, to determine the location and length of each edge in the polygon, while these edges are located at the boundary of and within the interior of the mixed pixel. Furthermore, VBSPM uses a decay function to manage the mixed pixels along the image boundary region due to the missing parts of their neighbours. Finally, a ray-crossing algorithm is employed to determine the land-cover class of each sub-pixel in terms of vectorial boundaries. The experiments with artificial and remotely sensed images have demonstrated that VBSPM can reduce the inconsistency between the boundaries of different land-cover classes, approximately calculating errors with an odd zoom factor, and achieve more accurate sub-pixel mapping results than the hard classification methods and GSPM.

Optical Design and Optimization of a Micro Zoom System with Liquid Lenses

A micro zoom system without moving elements by use of two liquid lenses is designed and optimized in this paper. The zoom equations of the system composed of two liquid lenses are deduced. The structure parameters including radius and thickness of a conical double-liquid electrowetting based lens are analyzed and calculated. Because the liquid thickness varies non-linearly with the radius of the interface, it's very difficult to optimize a real liquid lens using commercial optical design software directly. Through the Application Programming Interface (API) of the optical design software CODE V, a zoom system with two real electrowetting based liquid lenses is modeled and optimized. A two-liquid-lens zoom system without moving elements, with a zoom factor of 1.8 and a compact structure of 10 mm is designed for illustration. This can be useful for the camera design of mobile phones, tablets and so on. And this paper presents a convenient way of designing and optimizing a zoom system including liquid lenses by commercial optical design software.

3D Printing of Rat Salivary Glands: The Submandibular-Sublingual Complex

The morphology and the functionality of the murid glandular complex, composed of the submandibular and sublingual salivary glands (SSC), were the object of several studies conducted mainly using magnetic resonance imaging (MRI). Using a 4.7 T scanner and a manganese-based contrast agent, we improved the signal-to-noise ratio of the SSC relating to the surrounding anatomical structures allowing to obtain high-contrast 3D images of the SSC. In the last few years, the large development in resin melting techniques opened the way for printing 3D objects starting from a 3D stack of images. Here, we demonstrate the feasibility of the 3D printing technique of soft tissues such as the SSC in the rat with the aim to improve the visualization of the organs. This approach is useful to preserve the real in vivo morphology of the SCC in living animals avoiding the anatomical shape changes due to the lack of relationships with the surrounding organs in case of extraction. It is also harmless, repeatable and can be applied to explore volumetric changes occurring during body growth, excretory duct obstruction, tumorigenesis and regeneration processes. 3D printing allows to obtain a solid object with the same shape of the organ of interest, which can be observed, freely rotated and manipulated. To increase the visibility of the details, it is possible to print the organs with a selected zoom factor, useful as in case of tiny organs in small mammalia. An immediate application of this technique is represented by educational classes.

Interpolation-based super-resolution land cover mapping

Super-resolution mapping (SRM) is a technique to produce a land cover map with finer spatial resolution by using fractional proportion images as input. A two-step SRM approach has been widely used. First, a fine-resolution indicator map is estimated for each class from the coarse-resolution fractional image. All indicator maps are then combined to create the final fine-resolution land cover map. In this letter, three popular interpolation methods, Inverse Distance Weighted (IDW), Spline and Kriging, as well as four indicator map combination strategies, including the maximal value strategy and the sequential assignment strategy with and without normalization, were assessed. Based on the application to two simulated images, the performance of all SRM algorithms was assessed. The results show that the two-step SRM approach can obtain smoother land cover maps than hard classification. An increase in zoom factor results in the appearance of numerous small patches and linear artefacts in the SRM results. The accuracies of Spline and Kriging are similar and are both higher than that of IDW. The maximal value strategy can generate a smoother land cover map than the sequential assignment strategy in most cases, and a normalizing indicator value has a mixed effect on the result.

Human search with a limited field of view: effects of scan speed, aperture size, and target conspicuity

We investigate how human visual search performance with field of view (FOV) restrictions depends on scan speed, zoom factor, target location, and conspicuity. First, observers search a FOV that moves at a constant speed along a predefined path over a visual search scene (the field of regard, or FOR), and we measure the effects of scan speed, zoom factor, FOV size, target location, and conspicuity on search performance (detection time and probability). Then observers search either visual or thermal scenes by freely moving a joystick-controlled FOV over the FOR, while freely selecting the zoom factor in some conditions, and we measure the effects of the scan path characteristics and the use of different strategies on search performance. Search performance depends on the effective FOV size (the area where targets are expected to occur), but is largely independent of the display area. Both for visual and thermal imagery, various search performance measures correlate with target conspicuity. The results of both experiments suggest that observers can optimize their performance by adjusting their scanning behavior both to their visual limitations and to the expected target conspicuity. We present the outlines of a simple search model based on these current findings.

Multi-Frame SPRITE: A method for resolution enhancement of multiple-point SPRITE data

The Single Point Ramped Imaging with T1 Enhancement (SPRITE) sequence is well suited for the acquisition of magnetic resonance signals from fast relaxing nuclei and from heterogeneous materials. However, it is time inefficient compared to sequences that are based on frequency encoding because only one single point is acquired per excitation. Multiple-point SPRITE (mSPRITE) mitigates this problem with the acquisition of multiple FID points. mSPRITE images reconstructed from early FID samples suffer from reduced spatial resolution due to the limited extent of its corresponding k-space. In this work we present a new reconstruction algorithm for spatial resolution enhancement that solves this problem without changes to the mSPRITE sequence. The method, called Multi-Frame mSPRITE, substitutes high spatial frequencies from late FID points into k-spaces of limited extent constructed from early FID points. In this way, images of high quality and resolution can be obtained despite a large range of zoom factors used to reconstruct images with the same FOV and resolution.

Mechatronic Design of a Fully Integrated Camera for Mini-Invasive Surgery

This paper describes the design features of an innovative fully integrated camera candidate for mini-invasive abdominal surgery with single port or transluminal access. The apparatus includes a CMOS imaging sensor, a light-emitting diode (LED)-based unit for scene illumination, a photodiode for luminance detection, an optical system designed according to the mechanical compensation paradigm, an actuation unit for enabling autofocus and optical zoom, and a control logics based on microcontroller. The bulk of the apparatus is characterized by a tubular shape with a diameter of 10 mm and a length of 35 mm. The optical system, composed of four lens groups, of which two are mobile, has a total length of 13.46 mm and an effective focal length ranging from 1.61 to 4.44 mm with a zoom factor of 2.75×, with a corresponding angular field of view ranging from 16° to 40°. The mechatronics unit, devoted to move the zoom and the focus lens groups, is implemented adopting miniature piezoelectric motors. The control logics implements a closed-loop mechanism, between the LEDs and photodiode, to attain automatic control light. Bottlenecks of the design and some potential issues of the realization are discussed. A potential clinical scenario is introduced.

Land Cover Super-resolution Mapping using Hopfield Neural Network for Simulated SPOT Image

Using soft classification, it is possible to obtain the land cover proportions from the remotely sensed image. These land cover proportions are then used as input data for a procedure called “super-resolution mapping” to produce the predicted hard land cover layers at higher resolution than the original remotely sensed image. Superresolution mapping can be implemented using a number of algorithms in which the Hopfield Neural Network (HNN) has showed some advantages. The HNN has improved the land cover classification through superresolution mapping greatly with the high resolution data. However, the super-resolution mapping is based on the spatial dependence assumption, therefore it is predicted that the accuracy of resulted land cover classes depends on the relative size of spatial features and the spatial resolution of the remotely sensed image. This research is to evaluate the capability of HNN to implement the super-resolution mapping for SPOT image to create higher resolution land cover classes with different zoom factor.

Combining Pixel Swapping and Contouring Methods to Enhance Super-Resolution Mapping

Combining super-resolution techniques can increase the accuracy with which the shape of objects may be characterised from imagery. This is illustrated with two approaches to combining the contouring and pixel swapping methods of super-resolution mapping for binary classification applications. In both approaches, the output of the pixel swapping method is softened to allow a contour of equal class membership to be fitted to it to represent the inter-class boundary. The accuracy of super-resolution mapping with the individual and combined techniques is explored, including an assessment of the effect of variation in the number of neighbors and zoom factor on pixel swapping based analyses. When combined, the error with which objects of varying shape were represented was typically greatly reduced relative to that observed from the application of the methods individually. For example, the root mean square error in mapping the boundary of an aeroplane represented in relatively fine spatial resolution imagery decreased from 14.41 m with contouring and 4.35 m with pixel swapping to 3.07 m when the approaches were combined.

The Material of the Resonant Vibration Impact Motivates the Influence of and the Simulation Analysis

This paper to the resonant vibration conveying material on the effect of the shock of geologic detailed analysis to research, perfect the resonant vibration against the motive of the dynamic model. Application of the method of harmonic balance system dynamics equation of solution, and draw the conclusion that, under geological body dynamics of the zoom factor amplitude frequency response curve. A test bed to the actual parameters is simulated, on the test, the displacement of the geological time response curve. The results show that: consider material impact and without considering the impact of material, compared the antiresonant frequency decreases, and in the near antiresonance point, the amplitude becomes big bodies.

Super-Resolution Iris Image Restoration Based on Multiple MLPs and CLS Filter

Iris recognition is a biometric technology which shows a very high level of recognition accuracy, but low resolution (LR) iris images cause the degradation of the recognition performance. Therefore, a zoom lens with a long focal length is used in an iris camera. However, a bulky and costly zoom lens whose focal length is longer than 150 mm is required for capturing the iris image at a distance, which can increase the size and cost of the system. In order to overcome this problem, we propose a new super-resolution method which restores a single LR iris image into a high resolution (HR) iris image. Our research is novel in the following three ways compared to previous works. First, in order to prevent the loss of the middle and high frequency components of the iris patterns in the original image, the LR iris image is up-sampled using multiple multi-layeredperceptrons (MLPs). Second, a point spread function (PSF) and a constrained least square (CLS) filter are used to remove sensor blurring in the up-sampled image. Third, the optimal parameters of the CLS filter and PSF in terms of the recognition accuracy are determined according to the zoom factor of the LR image. The experimental results show that the accuracy of iris recognition with the HR images restored by the proposed method is much enhanced compared to the three previous methods.

The “covariation method” for estimating the parameters of the standard Dynamic Energy Budget model II: Properties and preliminary patterns

The covariation method for estimating the parameters of the standard Dynamic Energy Budget (DEB) model provides a single-step method of accessing all the core DEB parameters from commonly available empirical data. In this study, we assess the robustness of this parameter estimation procedure and analyse the role of pseudo-data using elasticity coefficients. In particular, we compare the performance of Maximum Likelihood (ML) vs. Weighted Least Squares (WLS) approaches and find that the two approaches tend to converge in performance as the number of uni-variate data sets increases, but that WLS is more robust when data sets comprise single points (zero-variate data). The efficiency of the approach is shown to be high, and the prior parameter estimates (pseudo-data) have very little influence if the real data contain information about the parameter values. For instance, the effects of the pseudo-value for the allocation fraction κ is reduced when there is information for both growth and reproduction, that for the energy conductance is reduced when information on age at birth and puberty is given, and the effects of the pseudo-value for the maturity maintenance rate coefficient are insignificant. The estimation of some parameters (e.g., the zoom factor and the shape coefficient) requires little information, while that of others (e.g., maturity maintenance rate, puberty threshold and reproduction efficiency) require data at several food levels. The generality of the standard DEB model, in combination with the estimation of all of its parameters, allows comparison of species on the basis of parameter values. We discuss a number of preliminary patterns emerging from the present collection of parameter estimates across a wide variety of taxa. We make the observation that the estimated value of the fraction κ of mobilised reserve that is allocated to soma is far away from the value that maximises reproduction. We recognise this as the reason why two very different parameter sets must exist that fit most data set reasonably well, and give arguments why, in most cases, the set with the large value of κ should be preferred. The continued development of a parameter database through the estimation procedures described here will provide a strong basis for understanding evolutionary patterns in metabolic organisation across the diversity of life.

Optical requirements on magnification systems for intracranial video microsurgery

The basic idea of video-microsurgery is the improvement of ergonomic conditions in microsurgical procedures by replacing the bulky operating microscope with a compact videosystem. To specify optical requirements on a videosystem for microsurgical intracranial procedures in neurosurgery. During 27 microsurgical intracranial procedures (12 cerebellopontine angle and 15 supratentorial) zoom factor, focus distance and illumination parameters of the operating microscope were continuously recorded. Ergonomic aspects were documented as well. The zoom factor ranged from 1.7 to 13.5 in CPA procedures and from 1.4 to 13.4 in supratentorial procedures. The focus distance ranged from 180 mm to 367 mm in CPA procedures and from 188 mm-472 mm in supratentorial procedures. From an optical point of view current operating microscopes meet the requirements of intracranial microneurosurgery. However, ergonomically further developments are highly desirable. Video microsurgery is a promising field and could hold a solution to this problem.

Spatial-Random-Access-Enabled Video Coding for Interactive Virtual Pan/Tilt/Zoom Functionality

High-spatial-resolution videos offer the possibility of viewing an arbitrary region-of-interest (RoI) interactively. Zoom functionality enables watching high-resolution content even on displays of lower spatial resolution. If arbitrary regions corresponding to arbitrary zoom factors can be served to the user, the transmission and/or decoding of the entire high-spatial-resolution video can be avoided. Moreover, if the video content can be encoded such that arbitrary RoIs corresponding to different zoom factors can be simply extracted from the compressed bitstream, we can avoid dedicated video encoding for each user. We propose such a video coding scheme that is vital in allowing the system to scale to large numbers of remote users as well as to encode and store the content for subsequent repeated playback. Apart from generating a multi-resolution representation, our coding scheme uses P slices from H.264/AVC. We study the tradeoff in the choice of slice size. A larger slice size enables higher coding efficiency for representing the entire scene but increases the number of pixels that have to be transmitted. The optimal slice size achieves the best tradeoff and minimizes the expected transmission bitrate. Experimental results confirm the optimality of our predicted slice size for various test cases. Furthermore, we propose an improvement based on background extraction and long-term memory motion-compensated prediction. Experiments indicate up to 85% bitrate reduction while retaining efficient random access capability.

The impact of image and class structure upon sub-pixel mapping accuracy using the pixel-swapping algorithm

A series of tests assess the impact of image and class structure within input imagery upon the accuracy of outputs from the pixel-swapping algorithm (PSA) to better assess the viability of this sub-pixel mapping algorithm to spatially locate class proportions and improve soft classification accuracies. Simulated maps with known spatial autocorrelation, class proportion and mixed pixel percentages are sub-pixel mapped at varying zoom factors using the PSA and accuracies measured. Block majority filtering (BMF) of input images is an experimental accuracy control. Results quantify PSA accuracies compared to the BMF based on the interrelationship between spatial autocorrelation, class proportions, zoom factor and mixed pixel quantities. Findings, while validating the known positive correlation between spatial autocorrelation and PSA accuracy, demonstrate class proportion difference and mixed pixel quantities to be positively and negatively related to PSA accuracy, respectively. Class proportion affects PSA accuracy to a greater degree on maps exhibiting low spatial autocorrelation levels versus maps with high spatial autocorrelation levels. Traditional accuracy measures, such as overall accuracy, are shown to overestimate the true performance of the PSA. The difference in overall accuracy of the PSA between all map pixels and within mixed map pixels alone can be over 20%. Overall, in general, the PSA accurately sub-pixel mapped input images with an approximate minimum level of spatial autocorrelation at a Moran's I of 0.63, a maximum of 30% of mixed pixels relative to entire image pixels, a difference in class proportions greater than 40% and at zoom factors below 10.

The effects of zoomable user interfaces and user age in searching for a target with a mouse on a two-dimensional information space

A zoomable user interface (ZUI) is a useful function to help users deal with large information spaces displayed within a screen. Although used in many applications, ZUIs have not been sufficiently studied in terms of usability. Usability problems may be more crucial for older people than younger ones. The objective of this study is to examine the effects of a combination of two zoom factors (three zoom focus methods: original-center, re-center, and aiming-point; and two zoom scales: +100% and +400%) for two age groups (younger and older adults) on mouse-based information searching tasks in a map-type two-dimensional information space. Twenty four volunteers (twelve users per age group) participated in the experiments by answering a pair of questions about fifty movie information topics. Task completion time, number of operations, and number of errors were selected as performance measures, and a subjective assessment of satisfaction was collected. Older adults used the tested ZUIs less efficiently and precisely than younger adults. The effects of zoom focus methods vary with zoom scale levels regardless of the age groups. The participants also preferred using the aiming-point focus regardless of zoom scale and using the re-center focus with the +400% scale. We discuss potential implications of the age-related performance differences and the effects of ZUI functions, and suggest some ZUI design guidelines in conclusion. We expect that the findings can be used as basic resources in designing various web services and applications for older computer users. Relevance to industry Given that a zoomable user interface is widely used in basic geographic information systems, web services, and various applications, using a selective-focus method such as the aiming-point focus can improve computer users’ usability; in particular, the zooming functions will greatly help older people to explore large information spaces quickly and easily.

Wheel-throwing in digital space using number-theoretic approach

This paper introduces a novel technique to create digital potteries using certain number-theoretic techniques of digital geometry. Given a digital generatrix, the proposed wheel-throwing procedure works with a few primitive integer computations only, wherein lies its strength and novelty. The digital surface created out of the digital wheel-throwing is digitally connected and irreducible when the digital generatrix is an irreducible digital curve segment, which ensures its successful rendition with a realistic finish, whatsoever may be the zoom factor. The proposed technique is also bestowed with the desired quality of producing a monotone or a non-monotone digital surface of revolution depending on whether or not the digital generatrix is monotone with respect to the axis of revolution. Thick-walled potteries, therefore, can be created successfully and efficiently to have the final product ultimately resembling a real-life pottery. Experimental results with some typical generatrices demonstrate its efficiency, elegance and versatility.

A cylindrical zoom lens unit for adjustable optical sectioning in light sheet microscopy

Light sheet microscopy became a powerful tool in life sciences. Often, however, the sheet geometry is fixed, whereas it would be advantageous to adjust the sheet geometry to specimens of different dimensions. Therefore we developed an afocal cylindrical zoom lens system comprising only 5 lenses and a total system length of less than 160 mm. Two movable optical elements were directly coupled, so that the zoom factor could be adjusted from 1x to 6.3x by a single motor. Using two different illumination objectives we achieved a light sheet thickness ranging from 2.4 µm to 36 µm corresponding to lateral fields of 54 µm to 12.3 mm, respectively. Polytene chromosomes of salivary gland cell nuclei of C.tentans larvae were imaged in vivo to demonstrate the advantages in image contrast by imaging with different light sheet dimensions.

A method for accurate localisation of EBSD pattern centres

The moving screen technique for pattern centre localisation is revisited. A cross-correlation based iterative procedure is developed to find both the zoom factor and the zoom centre (which is also the pattern centre) between two EBSD diffraction patterns acquired at two camera positions. The procedure involves two steps: first, a rough estimate of the pattern centre position and zoom factor (the ratio of the two detector distances) is obtained by cross-correlating the entire images. Then, based on this first estimate, cross-correlation of smaller regions of interest (ROIs) gives the displacement field which is interpreted as a zoom factor misfit coupled with a zoom centre position misfit. These misfits are iteratively decreased until the displacement field is reduced to the noise level. The procedure is first applied to simulated patterns and it is shown that the iterative procedure converges very rapidly to the exact solution with an accuracy better than 1/100th of pixel. The potential of this technique for experimental patterns is discussed and recommendations for new EBSD detectors are proposed.