This PDF file contains the front matter associated with SPIE Proceedings Volume 7429, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

Recent research in the area of electro-optical system design identified the benefits of spherical aberration for extending the depth-of-field of electro-optical imaging systems. In such imaging systems, spherical aberration is deliberately introduced by the optical system lowering system modulation transfer function (MTF) and then subsequently corrected using digital processing. Previous research, however, requires complex digital postprocessing algorithms severely limiting its applicability to only expensive systems. In this paper, we examine the ability of low-cost spatially invariant finite impulse response (FIR) digital filters to restore system MTF degraded by spherical aberration. We introduce an analytical model for choosing the minimum, and hence cheapest, FIR filter size capable of providing the critical level sharpening to render artifact-free images. We identify a robust quality criterion based on the post-processed MTF for developing this model. We demonstrate the reliability of the estimated model by showing simulated spherical coded imaging results. We also evaluate the hardware complexity of the FIR filters implemented for various spherical aberrations on a low-end Field-Programmable Gate Array (FPGA) platform.

A phase mask at the aperture stop of a hybrid digital-optical imaging system can improve its tolerance to aberrations. The choice of the introduced phase modulation is crucial in the design of such systems. Several successful phase masks have been described in the literature. These masks are typically derived by searching for optical-transfer-functions that retain restorability under aberrations such as defocus. Instead of optimizing the optical-transfer-function for some desired characteristics, we calculate the expected imaging error of the joint design directly. This was used to compare thirddegree polynomial phase masks, including the cubic phase profile and a commonly used generalization. The analysis shows how the optimal phase profile depth is always limited by noise and more importantly, numerical simulations show that only a finite range of the third-degree polynomial profiles yield optimal performance.

Three different techniques for extending the depth of field of a low-power (4x) microscope objective system are examined experimentally: wavefront coding with a cubic phase mask, amplitude modulation with a large central obscuration, and added spherical aberration. Their relative merits are discussed and demonstrated with sample images.

A novel design of a phase coded depth-sensing camera is presented. A rotational symmetric phase mask is designed to discriminate the point spread functions (PSF) from different scene distances. The depth information can then be computationally obtained from a single captured photograph through a phase coded lens. The PSF must be carefully optimized at off-axis angles in order to create a restored image which is sharp over the required field of view. In this paper, a phase coded depth camera with a focal length 10.82mm, sensor size 2mm and F-number 5 is designed. Simulation data is exchanged between Matlab and Zemax for co-optimization of optical coding and digital decoding process. The simulation result shows that coarse depth information is investigated for object distance from 513 mm to 1000 mm.

We studied the infrared image guidance for ground vehicle based on the fast wavelet image focusing and tracking. Here we uses the image of the uncooled infrared imager mounted on the two axis gimbal system and the developed new auto focusing algorithm on the Daubechies wavelet transform. The developed new focusing algorithm on the Daubechies wavelet transform processes the result of the high pass filter effect to meet the direct detection of the objects. This new focusing gives us the distance information of the outside world smoothly, and the information of the gimbal system gives us the direction of objects in the outside world to match the sense of the spherical coordinate system. We installed this system on the hand made electric ground vehicle platform powered by 24VDC battery. The electric vehicle equips the rotary encoder units and the inertia rate sensor units to make the correct navigation process. The image tracking also uses the developed newt wavelet focusing within several image processing. The size of the hand made electric ground vehicle platform is about 1m long, 0.75m wide, 1m high, and 50kg weight. We tested the infrared image guidance for ground vehicle based on the new wavelet image focusing and tracking using the electric vehicle indoor and outdoor. The test shows the good results by the developed infrared image guidance for ground vehicle based on the new wavelet image focusing and tracking.

This work is intended to deal with the problems which arise when illuminanting Paleolithic cave paintings. We have carried out the spectral and colorimetric characterization of some paintings located in the Murcielagos (bats) cave (Zuheros, Córdoba, Spain). From this characterization, the chromatic changes produced under different lighting conditions are analysed. The damage function is also computed for the different illuminants used. From the results obtained, it is proposed an illuminant whose spectral distribution diminishes the damage by minimizing the absorption of radiation and optimises the color perception of the paintings in this cave. The procedure followed in this study can be applied to optimise the lighting systems used when illuminating any other art work

The color and luminance distributions of large light sources are difficult to measure because of the size of the source and the physical space required for the measurement. We describe a method for the measurement of large light sources in a limited space that efficiently overcomes the physical limitations of traditional far-field measurement techniques. This method uses a calibrated, high dynamic range imaging colorimeter and a goniometric system to move the light source through an automated measurement sequence in the imaging colorimeter's field-of-view. The measurement is performed from within the near-field of the light source, enabling a compact measurement set-up. This method generates a detailed near-field color and luminance distribution model that can be directly converted to ray sets for optical design and that can be extrapolated to far-field distributions for illumination design. The measurements obtained show excellent correlation to traditional imaging colorimeter and photogoniometer measurement methods. The near-field goniometer approach that we describe is broadly applicable to general lighting systems, can be deployed in a compact laboratory space, and provides full near-field data for optical design and simulation.

In thremmatology, many researches focus on ecological illumination for improving the growing speed of animal or plant. According to the Trichromatic theory, any specific color can be made up of red, green, and blue light. Sunlight has full spectrum so it is the most applicable source. A Natural Light Guiding System includes collecting, transmitting, and lighting parts. In our research, we would like to design a beam splitter in the transmitting part to separate the sunlight into red, green, and blue light for ecological illumination. We use high pass and low pass dichroic coatings in a prism, called dichroic prism, to be the beam splitter to separate the wavelength. For measuring the spectra of the exit beams, we build a space with the Natural Light Guiding System. In the space, the spectra of sunlight outside and inside the space and the exit beams of the beam splitter are measured. Finally, we use prismatic structure to design the beam splitter, and optimize the surface of the element with aspheric surface and Fresnel surface to reduce the beam angle of exit light.

In recent years, the practicality and importance of the illumination with sunlight are getting more seriously concern in public. The reason is that natural light is non-polluting, energy-saving, and healthy in comparison with traditional light sources. Therefore, our research focuses on how to replace the artificial sources by natural light. A Natural Light Guiding System has collecting, transmitting, and lighting parts. For replacing the traditional sources, the lighting part should have similar characteristic, such as intensity distribution and geometric parameters, to artificial sources. In this paper, we design, simulate, and optimize illumination lightpipe with dot pattern to redistribute the collecting sunlight from Natural Light Guiding System. The lightpipe includes input, system, and output parts. In the input part, we design a coupler to improve the coupling efficiency with natural light. For optimizing the efficiency of the coupler, we evaluate the relationship between the distance that is from the fiber to the lightpipe and the coupled power. In the system part, the sunlight is locked by total internal reflection, TIR, so we design dot pattern to scatter the locked sunlight for uniform lighting. In the output part, a uniform illumination is our goal. For designing the percentage of the surface will be covered by dot pattern, we offer a design theory and simulate the efficiency.

The Simultaneous Multiple Surfaces (SMS) was developed as a design method in Nonimaging Optics during the 90s. Later, the method was extended for designing Imaging Optics. We present an overview of the method applied to imaging optics in planar (2D) geometry and compare the results with more classical designs based on achieving aplanatism of different orders. These classical designs are also viewed as particular cases of SMS designs. Systems with up to 4 aspheric surfaces are shown. The SMS design strategy is shown to perform always better than the classical design (in terms of image quality). Moreover, the SMS method is a direct method, i.e., it is not based in multi-parametric optimization techniques. This gives the SMS method an additional interest since it can be used for exploring solutions where the multiparameter techniques can get lost because of the multiple local minima.

In consideration of the broad range of possible Fresnel lens applications, it is desirable to find a fast way of approximating optical performance that is not specific to a particular lens geometry. This is potentially useful for gaining deeper insight into a lens system and affording accelerated development times. Additionally, a Fresnel lens manufactured using a molded polymer process has limitations on how accurately it can replicate a microstructured prismatic pattern. This is especially true at the prismatic peaks of the part where it is more difficult to completely "fill-out" the moldbase. Inclusion of this effect in performance evaluation is important. Using transmission efficiency (or transmittance) as the metric, a Fresnel lens model which includes imperfect peak replication is sought. The system description will be parameterized so that the formulations are not specific to a particular geometry and can be generally applied. The parameter space will be explored with raytracing and the results compiled for convenient reference.

Many practical singlet lenses (with one aspheric and one planar surface) can be designed analytically without resorting to iterative optimization. "Good" lenses that precisely focus or collimate monochromatic light are covered first. Then a less important but more interesting "bad" case is discussed. An unusual application required a singlet lens whose axial caustic is an order-of-magnitude greater than its paraxial focal length. A lens with a radial spline surface was designed using the CodeV and ASAP macro languages. The near-field on-axis diffraction irradiance produced by the lens was verified using the ASAP software's beamlet decomposition/summation capability. Specification of the surface for manufacture seemed straightforward but became problematic due to limitations at the time in the software used by the computer-controlled grinding and polishing machines. Eventually the lens was manufactured successfully but only after fitting the spline to a standard radial polynomial (including odd terms).

This paper proposes a new method for optimization optics with a diffractive optical element (DOE) via a Hybrid Taguchi Genetic Algorithm. A Diffractive Optical Element, based the theory of wave phase difference, takes advantage of the negative Abbe number which might significantly eliminate the axial chromatic aberrations of optics. Following the advanced technology applied to the micro lens and etching process, precisely-made micro DOEs can now be manufactured in large numbers. However, traditional least damping square has its limitations for the optimization of axial and chromatic aberrations with DOE. In this research, we adopted the genetic algorithm (GA) and incorporated the steady Taguchi method into GA. Combining the two methods produced a new hybrid Taguchi-genetic algorithm (HTGA). Suitable glass combinations and DOE positions were selected to minimize both axial and lateral chromatic aberration in the optical system. This new method carries out the task of eliminating both axial and lateral chromatic aberration, unlike DOE optimization by LDS, which works for axial aberration only and with less efficiency. Experiments show that the surface position of the DOE could be determined first; in addition, regardless of whether chromatic aberration was axial or longitudinal, issues concerning the optical lens's chromatic aberration could be significantly reduced, compared to results from the traditional least damping square (LDS) method.

More optical engineers are choosing to use Risley prism devices to accomplish alignment and steering of optical systems. A Risley prism device consists of a pair of rotating wedged optic elements that redirect rays of light by refraction. By rotating each wedge independently, the originating ray can be steered to a new angle or translated within a cone respective of the wedge angle and separation of the prism pair. The automated miniature Risley mechanism (MRM) was designed and tested for space flight where the physical envelope was significantly constrained, only very low power was available, and a unique power-off hold function was required. The MRM incorporates a prism pair with a 19 mm clear aperture and 0.75° wedge angle; it performs at 6 rpm (maximum speed) with a beam deflection accuracy of 25 μrad, and a power-off holding accuracy of 8 μrad within a 64 mm (optic axis) by 58 mm (height & width) envelope. This paper describes the driving requirements for the MRM and how the MRM assembly was successfully tested to verify its space flight performance requirements. Some design features included in the MRM assembly are: the radial titanium isothermal optical flexure mounts, a direct-drive zero-cog motor, a 37 Hz bandwidth closed-loop control system; a unique inductive position sensing system; and a fail-safe flexure-type brake assembly.

A system of collection optics was designed and built to perform imaging spectroscopy on shock waves created in the Electric Arc Shock Tube (EAST) at NASA Ames Research Center. This reflective system has four channels and collects radiation wavelengths that span from the vacuum ultraviolet to the near-infrared (120-1700nm). A telecentric object space minimizes blur along the direction of propagation of the shock wave. Additional fold mirrors preserve image orientation and cause the system to be symmetric with respect to the spectrometer entrance slits. The aperture is angularly segmented to allow more than one channel on each side of the shock tube. Optical/mechanical design trade studies, photographs of the as-built system and sample data are presented.

The objective of this work is the suppression of speckles in an image illuminated by a remote laser. This is accomplished by a novel method in which the illuminating laser beam propagates through a multimode fiber dithered at an arbitrary section, then passes through a microlens array prior to illuminating the image generator. Thereby the speckle contrast is reduced to its minimum value for dithering frequencies of at least 25 Hz, attaining a magnitude speckle contrast of less than 12%, and illumination homogeneity across the illumination filed of less than 20%.

Ocular microtremor (OMT) is a physiological high frequency (up to 150Hz) low amplitude (150-2500nm) involuntary tremor of the human eye. It is one of the three fixational ocular motions described by Adler and Fliegelman in 1934 as well as microsaccades and drift. Clinical OMT investigations to date have used eye-contacting piezoelectric probes or piezoelectric strain gauges. Before contact can be made, the eye must first be anaesthetised. In some cases, this induces eyelid spasms (blepharospasm) making it impossible to measure OMT. Using the contact probe method, the eye motion is mechanically damped. In addition to this, it is not possible to obtain exact information about the displacement. Results from clinical studies to date have given electrical signal amplitudes from the probe. Recent studies suggest a number of clinical applications for OMT, these include monitoring the depth of anaesthesia of a patient in surgery, prediction of outcome in coma, diagnosis of brainstem death. In addition to this, abnormal OMT frequency content is present in patients with neurological disorders such as Multiple sclerosis and Parkinson's disease. However for ongoing clinical investigations the contact probe method falls short of a non-contact accurate measurement solution. In this paper, we design a compact non contact phase modulating optical fiber speckle interferometer to measure eye motions. We present our calibration results using a calibrated piezoelectric vibration simulator. Digital signal processing is then performed to extract the low amplitude high frequency displacement information.

The purpose of this study is to find the shape requirement of image sensors when catching the image to obtain a much clear image than the flat image sensor. The results are applied to an o-ring driven liquid filled lens. It was found that the image distortion of the liquid filled lens is inevitable. Therefore, it is necessary to design an curved image sensor which can compensate the image distortion to solve this problem. The shape of the image sensor can be predicted by computer simulation. The required shape of the image sensor can be obtained by deforming the PDMS (Polydimethylsiloxane) membrane. The deformation of PDMS membrane of lens and the image sensor film can be obtain by using ANSYS® software at variable internal pressure in the liquid filled lens. The experimental module is composed of a barrel, transparent liquid (De-ionized water), PDMS lens membrane, rigid ring of lens curvature control, adjustable accessories of lens curvature orientation, the image sensors which are constructed on PDMS film, rigid ring of sensor film curvature control, and adaptable accessories of sensor film variable curvature adjustment. The ring of sensor film and accessories are utilized for variable sensor film's curvature control. On the basis of lens curvature's modulation, the image sensor film tuning process makes the image sensors on the optimal plane.

Wavefront measurements are a key point in the development of imaging techniques. Nowadays, a common tool for these measurements is the Shack-Hartmann sensor, where the results are often given in terms of the Zernike polynomials. The interpretation of the results, as one moves the Shack-Hartmann sensor in the axial zone, is sometimes difficult as it involves the task of visualizing the geometrical propagation of the wavefront. We present a numerical tool based on ray tracing that visualizes wavefronts and caustics as the beam propagates and enables the calculation of the Zernike polynomials at any intermediate stage.

Recently, joint analysis and optimization of both the optical sub-system and the algorithmic capabilities of digital processing have created new digital-optical imaging systems with system-level benefits. We explore a special class of digital-optical imaging systems called spherical coding that combine lens systems having controlled amounts of spherical aberration with digital sharpening filters to achieve fast, low-cost, extended depth-of-field (EDoF) imaging systems. We provide analysis of the optimal amount of spherical aberration required as a function of desired depth-of-field extension. We also characterize the MSE-optimal filters required to restore contrast. Finally, we describe a simple method to designing spherical coded systems and demonstrate several advantages such as improved manufacturing yield using an actual lens design.

Based on an analytical analysis of the optical transfer function in an optical system with wavefront coding, specifically with a cubic phase mask in the aperture stop, we explain that such systems have image artefacts in the restored images and that these are manifested as replication artefacts. To remove image artefacts we propose to store a set of defocused point spread functions such that a single defocused image can be restored to a set of images, wherein one of them is without image artefacts. The image without image artefacts is determined with a new metric which we define in the wavelet domain.

Using the Photonics Leaders program model, recruitment and retention, photonics content, parental engagement, internship, and PHOTON PBL challenges, the session's goal is to inform educators of strategies that can be used to motivate and develop cognitive skills in the discipline of Physics. The program caters to ethnically diverse students who traditionally lack experiences in the discipline. This paper discusses the initial findings of the National Science Foundation (NSF) Innovative Technology Experiences for Students and Teachers (ITEST) program through which high school students and teachers were given the opportunity to participate in shared lessons, and coordinate projects through cooperative learning at The Science House at North Carolina State University.

Following a severe drop in enrollment, one high school's photonics program was in jeopardy of being eliminated. Instead, the program was rejuvenated and expanded and now meets the needs of more students than ever. In this paper, we describe how various resources were combined to improve methods of instruction (specifically, through problembased learning, or PBL), enhance classroom/real-world integration, and solidify the role this program plays within the school's larger science and technology curriculum (recently revised to meet new state guidelines). Instructor participation in the New England Board of Higher Education (NEBHE) PHOTON projects, funded by the National Science Foundation, was key.

This paper describes different methods used in the classroom and lab to teach photonics technology students to think. When students transcend from the classroom to the work environment, they must be able to think and problem solve without a teacher, instructor, or professor holding their hand during problem solving. There are many ways that can be used in the classroom to teach students to think. The methods discussed in this paper range from using thought provoking questions during lecture, to "full blown" project based learning methods, such as "Problem Based Learning".

A common complaint about entering college students is that they are not prepared for the college experience. In response to the problem, many colleges and universities offer "first year experience" (FYE) courses that provide a transition to the college experience, promote academic success and enhance learning. In this paper we describe a first semester optics course for community college students that is taught as an inquiry-based studio-type course. Introduction to Light and Lasers incorporates many ideas of a first year experience course and addresses the issue of students underprepared in mathematics, communication, critical thinking and hands-on laboratory skills.

To obtain a number of advantages in fabrication, testing and alignment, many designs in which spherical mirrors replace classical Cassegrain-form aspheric mirrors are present in the literature. However, spherical mirrors suffer from substantial spherical aberration and thereby require some form of corrector group. But in this case, the question encountered is that of making the basic optical configuration more complex. In this paper, a new design based on Cooke corrector group is presented for eliminating spherical aberration, which is believed to provide higher performance with less complexity than previous approaches. Besides, the cost and fabrication period will be extremely decreased. The telescope system using corrector group here can achieve good optical performance with f^# of 10, full field of 0.5°, obscuration of 1/3 and MTF (Modulation Transfer Function) of 0.48 corresponding to 50@lp/mm.

When a fingerprint image is acquired via contactless means, the depth of field must be measured. Due to the natural curvature of a finger, not all of the fingerprint will be in focus. Defocus introduced by such curvature may cause contrast reduction, loss of certain spatial frequencies, blurriness, and contrast reduction and reversal. We need to ensure that the imaging system has enough depth of field to compensate for the longitudinal displacement created by the finger curvature. This paper presents theoretical and experimental techniques to simulate and measure the depth of field of an imaging system. Experimentally, image contrast as a function of object position along the optical axis is measured for several spatial frequencies of interest, and the defocused modulation transfer function (MTF) is determined. The acceptable contrast range is defined by the system application and used to determine the corresponding depth of field. A diffraction image irradiance theoretical model is developed, and the Zemax optical design program is used to simulate depth of field. The experimental and simulated depth-of-field results are presented and applied to a contactless fingerprint sensor.

Colonoscopy is the current gold standard for colon cancer screening and diagnosis. However, the near-blind navigation process employed during colonoscopy results in endoscopist disorientation and scope looping, leading to missed detection of tumors, incorrect localization, and pain for the patient. A fiber optic bend sensor, which would fit into the working channel of a colonoscope, is developed to aid navigation through the colon during colonoscopy. The bend sensor is comprised of a bundle of seven fibers doped with quantum dots (QDs). Each fiber within the bundle contains a unique region made up of three zones with differently-colored QDs, spaced 120° apart circumferentially on the fiber. During bending at the QD region, light lost from the fiber's core is coupled into one of the QD zones, inducing fluorescence of the corresponding color whose intensity is proportional to the degree of bending. A complementary metal oxide semiconductor camera is used to obtain an image of the fluorescing end faces of the fiber bundle. The location of the fiber within the bundle, the color of fluorescence, and the fluorescence intensity are used to determine the bundle's bending location, direction, and degree of curvature, respectively. Preliminary results obtained using a single fiber with three QD zones and a seven-fiber bundle containing one active fiber with two QDs (180° apart) demonstrate the feasibility of the concept. Further developments on fiber orientation during bundling and the design of a graphical user interface to communicate bending information are also discussed.

For early detection of abnormalities growing within the healthy tissues a laser based multi-slice reflectance measurement technique is developed. The laser light is guided at the center of the probe. Around this the photo-detectors are arranged symmetrically at various distances from the beam entry point. The optical radiations after scattering within the tissue emerge at various locations which are detected by the detectors. After conversion from current to voltage these signals are digitized and fed to computer. After pre-processing of the backscattered signals from 36 photo-detectors arriving from various locations the reflectance images are reconstructed. As the detectors are placed at various distances from the beam entry point in the form of rings, their respective images are obtained. These multi-slices images provide variation in composition at various depths ranging from 2 - 7.5mm. Thus by placing the probe just once the required data for images reconstruction is obtained. This is in contrast to earlier developments as this does not involve the movement of the probe for image reconstruction. Based on the sequence of images from various depths a three - D image of the tissue structure could also be obtained.

A new approach for structural synthesis of optically compensated zoom lenses is reported. An implementation of evolutionary programming facilitates the procedure by carrying out a global search over the available degrees of freedom, namely, powers of the components and the inter-component separations. Practical success of the method depends on suitable formulation of the fitness function. Normalization of the variables is carried out to get an insight on the optimum structures. Illustrative numerical results are presented.

Illumination is critical to achieve high-contrast, contactless fingerprint images. In this paper, we report results of fingerprint imaging experiments performed under different illumination conditions. We studied how polarization states, illumination wavelength, detection wavelength, and illumination direction influence the contrast of fingerprint images. Our research findings provide a selection rule for optimum illumination and a basis for us to construct an illuminator that generates uniform illumination and high-contrast contactless fingerprint images.

Heterodyne Velocimetry (or Photonic Doppler Velocimetry) has turned out to be a major tool to study the phenomena occurring in detonics and shock wave experiments. With accessible velocities ranging form a few m/s to 30,000 m/s, a very high sensitivity, a dynamics of more than 20 dB and a multi-velocity capability, one can understand why this technique opens new fields of study. This article is aimed at presenting an outlook of the setups and configurations which have been tested. We will connect this outlook to a quick overview of different kinds of experiments that could be achieved. In a first part we will remind how the system works. We will then detail the many setups that have already been put to the test, with different possible hardware configurations responding to different uses and different probes aimed at sensing specific phenomena. We also present our Matlab© based software developed to process the signals. Finally we will go through the different applications on which PDV was implemented, both in a detonics context (free surface, particles and Nitro Methane - or NM - characterization) and in lab experiments (measurement of laser driven shocks on metallic targets).

of grating. First, we studied the reversibility of optical path of grating illuminated by monochromatic light, and then illuminated by polychromatic light. We found that the optical path of diffraction of grating has partial reversibility. Using the partial reversibility of optical path of diffraction of grating, we analyzed the spectral combination characteristic of grating and the bi-grating diffraction imaging effect.

A contactless fingerprint sensor provides deformation-free, high-quality fingerprint images and offers users a cleaner and more comfortable measurement environment. Here we propose and design an innovative prototype optical, contactless, compact, fingerprint sensor that quickly produces high-quality, high-contrast interoperable fingerprint images. A proofof- concept contactless, aliveness-testing (CAT) fingerprint sensor, which is connected to a PC via a firewire cable, was constructed and is currently operating in our laboratory. The CAT sensor affords a more user-friendly interface compared to existing contactless fingerprint sensors and also provides robust aliveness testing and spoof detection. In this paper, we present the imaging system design concepts, finger aliveness detection techniques, and the user-friendly interface approach. Various fingerprint matching results using the CAT sensor device are also presented and discussed.

Optical-fiber vortex-shedding flowmeter is prospective in its application in the measurement field not only for the merits up from vortex-shedding flowmeter but also those in optical fiber sensor such as flexibility, strong endurance, anti electromagnetic interference capacity and adaptation in the flammable explosive environment. A new optical-fiber vortex-shedding flowmeter based on white-light interference principle is introduced in this paper. Because of only responding on dynamic disturbance, the all-fiber white-light interferometric flowmeter not only holds the high-sensitivity of interferometric sensors, but also overcomes the instability of the traditional interferometric sensors, which tend to being affected from the external environmental condition such as temperature fluctuation. At last, some experimental curves are presented in this paper.