We show the basic mechanism of optical pH sensors using hydrogels and FBGs. We show the experimental results
obtained and the importance of a precise formulation of the hydrogel an appropriated design of our transducer.
V. Micó, M. L. Lozano, J. J. Esteve-Taboada, J. A. Carrión, T. Molina-Jiménez, S. Simón, E. Pérez, J. M. Lloris, M. Cruz-Yusta, M. J. López-Tendero, C. Silvestre, F. López, D. Barrera-Villar, R. García-Olcina, S. Sales
There are a lot of factors that call into question the integrity, safety and reliability of concrete macrostructures such as
bridges, buildings, tunnels and dikes. Examples of such factors are humidity variations, in-excess load supported during
years, vibrations and pH variations, which can damage the concrete structure after extended periods. In order to test the
real state of such structures, we present the design and development of fiber optic based sensors that permit the
measurement of loads and tensions applied to the structure, just as both the humidity and pH of the concrete at the
measurement point. The load of the structure can be measured by means of fiber Bragg grating techniques, which
involves wavelength multiplexing and optical spectrum analysis, and the humidity and pH measurements are achieved
by incorporating different types of hydrogels to the nearness of the fiber Bragg grating. The change in humidity and pH
produces volume changes in these hydrogels that modify the spectral response provided by the fiber Bragg grating. Thus,
it is possible to place multiple sensors along the macrostructure to visualize the on-line status during its life time.
KEYWORDS: Computer aided design, Finite element methods, Solid modeling, 3D acquisition, 3D modeling, 3D metrology, Reverse modeling, Chemical elements, Systems modeling, Manufacturing
Conventional techniques applied to three dimensional (3D) acquisition of information has significant limitations
depending on the features of the piece under test. Thus, complex curvatures, deeper concavities and higher volumes are
some examples of critical factors in which contact digitising systems are not suitable to undertake such kind of task. In
these cases, the usage of optical 3D digitization systems implies a more appropriate way to obtain 3D information about
the sample. In particular, structured illumination by means of white light provides point-to-point object acquisition with
accuracy and resolution that are always below the manufactured tolerances. Moreover, when the object under test is too
large, structured illumination can be mixed with photogrammetrical techniques in order to avoid errors by means of the
delimitation of the overall working volume. This proceeding presents several real cases applied to mould industry in
which 3D shape measurement using white light structured illumination is combined with finite element method (FEM)
and laser cladding techniques to allow the repair of the mould.
One of the most interesting points when evaluating the response of an implanted prosthesis is the knowledge of how
biomaterials behave under a certain deforming stress. Obviously, the greater the stress on a particular moment, the higher
possibility of the failure implant. But in many cases, the most important fact regarding the implant failure is due to a
lesser stress that is continuously applied. Therefore it is helpful to know how biomaterials respond to this lesser stress.
Digital speckle interferometry (DSPI) is suitable for this type of determination because of it is a highly sensitive and
non-invasive optical technique.
The aim of the presented work is determining the elasticity of biomaterials such as osseous structures and implants used
to replace bones and to fix fractures between them. In particular, preliminary results were obtained applied to macerated
human radius and a titanium screw used to treat the fractures of this bone. The analysis shows high correlation ratios in
determining Young's modulus via DSPI technique in comparison with than that obtained by creation of the bone
computer aided design (CAD) model using finite element method (FEM) in ANSYS software. The high degree of
concordance between the results of both methods makes it possible to continue studying osseous samples with a fixed
implant, and also other implants made of different alloys.
Knowledge of how osseous structures and implants behave under deforming stress is an interesting point when evaluating the response of an implanted prosthesis. The failure of an implant is not always due to the great stress a structure may be subjected to at a particular moment, but rather to the effects of deterioration associated with lesser stress but which is continuously applied. Therefore it is helpful to know how bones and implants respond to this lesser stress. Digital speckle interferometry (DSPI) is suitable for this type of determination, as it is a highly sensitive, non-invasive optical technique.
In this study we present the results we obtained when determining the elasticity of a sample of a macerated human radius, a titanium implant and a titanium screw used to treat the fractures of this bone. The correlation ratios we obtained in determining Young's modulus were in the order of r=0.994. Models were made of these structures using the finite elements method (FEM) with the aid of the ANSYS 10.0 program, applying Young's modulus values determined by DSPI.
With a view to monitoring the accuracy of the FEM models of the bone and the implant elements we designed a flexion experiment to obtain the DSPI values in and out of plane. The high degree of concordance between the results of both methods makes it possible to continue studying osseous samples with a fixed implant, and also other implants made of different alloys.
In this paper we present an automatic system for the on-line quality control of printed circuit boards. A line-scan camera permits the acquisition of a 550 mm wide image with a resolution up to 70 microns/pixel. The system detects the following type of errors: cuts and short circuits in tracks, stains, ink excess or faults, pores, omissions, "bites" and track narrowing. The input for the system are just the Gerber data files corresponding to the circuit to be analyzed. All the tolerances and precision factors can be modified directly from the user-friendly interface. For each analyzed board, the type of error detected and its location inside the circuit are indicated in the interface. For each set of analyzed circuits the system provides information for statistical control of the results.
The problem of three-dimensional (3-D) object recognition is addressed. Range images permit the description of 3-D surfaces with a significant reduction of the complexity of the processing. The encoding of range images as phase gives a simple and straightforward method for parallel processing of these images. In this contribution we propose the use of range images encoded as phase to deal with the detection of three dimensional objects. The use of Fourier transform profilometry can serve for real time optical implementation of correlators based on this encoding, using a joint transform correlator or a VanderLugt one. The extension to scale and in-plane rotation invariant detection is discussed and implemented in a simple optoelectronic system. Furthermore, a method for full 3-D rotation invariant detection is presented. A simplified approach allowing only rotation around an axis perpendicular point of view permits the implementation with a conventional correlator.
We present a method to localize a target in the three-dimensional space. The use of a white light optical correlator that gives us a different response depending on the scale of the input image permits to know the depth position of the particular target, since each different depth position of the target produces an image of different size when captured with a CCD camera. The setup is based on wavelength multiplexing since each different depth position, or analogously, each different scale in the captured image is detected with a different wavelength in the correlation plane.
Fourier transform profilometry, a well-known technique to obtain images of three-dimensional (3-D) objects, is used to achieve a real-time optical recognition of 3-D objects. A distorted grating pattern, that carries all the 3-D information of the object, is obtained from the projection of a regular fringe pattern onto the 3-D object surface. The analysis of such patterns is the basis of the optical method for recognizing 3-D objects in real time. The performance of the technique is demonstrated in two different types of correlators: the joint transform correlator and the classical convergent correlator. The proposed method is extended to the rotation-invariant and scale-invariant 3-D optical recognition. As is shown, the whole experimental setup can be constructed with simple equipment. Some experimental results, which demonstrate the ability of the method, are presented.
The main advantage of optical image processing with respect to its electronic counterpart is the high degree of parallelism. This characteristic can be boosted by feeding an optical system with several channels simultaneously. Several ways to perform this multiplexing can be devised. In this talk we focus on the spatial multiplexing, were several channels share the spatial bandwidth of the system input and wavelength multiplexing, were the channels are input in different wavelengths simultaneously. Principle and applications are discussed, along with several possible architectures for image processing systems.
A real time system for three-dimensional (3-D) object recognition based on Fourier transform profilometry technique is presented. We demonstrate the performance of the proposed method in two different types of correlators: the joint transform correlator and the classical convergent correlator. The projection of a regular fringe pattern onto the 3-D object surface permits to obtain a distorted grating pattern that carries all the 3-D information of the object. The analysis of such patterns is the basis of the method for recognizing 3-D objects in real time. With this method is also possible to obtain rotation-invariant and scale-invariant 3-D object recognition. The experimental results demonstrate the theory and show the utility of the proposed method.
Several methods for channel multiplexing are described and analyzed. The systems permit the use of a single optical setup for the processing of multichannel images or several channels of the same image. The definition of channels depends on the problem to be addressed, examples being RGB images, several orders of circular or radial harmonic extracted from a monochromatic image or resolution channels. The methods can rely on a time sequential multiplexing, spatial multiplexing in the input plane and wavelength multiplexing
We present an optical method to obtain scale-invariant 3D object recognition. It is based on using the Fourier transform profilometry technique and a classical convergent correlator. To obtain the scale invariance property different approaches, such as Mellin radial harmonic decomposition, logarithmic radial harmonic decomposition, and specifically modified matched filters, are considered. Simulated results demonstrate the good performance of the method. Scale-invariance is achieved in an interval of scale 1:1.67.
In this paper we present a real-time system for three- dimensional (3D) object recognition. It is based on the use of the Fourier transform profilometry technique and a joint transform correlator. The projection of a regular fringe pattern onto the 3D object surface permits us to obtain a distorted grating pattern that carries all the 3D information of the object. The analysis of such patterns is the basis of the method for recognizing 3D objects in real time. Later, by encoding with a fringe pattern a single component of the circular harmonic expansion derived from the object to be detected, a rotation-invariant 3D object recognition is also demonstrated. The whole experimental setup is robust and can be constructed with simple equipment. The experimental results demonstrate the theory and show the utility of the proposed method.
We present a novel method for achieving in real-time a 2D object wavelet decomposition with white light illumination. The underlying idea of the suggested method is wavelength multiplexing: the different wavelet components of an input object are transmitted simultaneously in different wavelengths and summed incoherently at the output plane. Experimental results show the utility of the new proposed method.
We demonstrate a method of obtaining scale invariance detection using a white light optical correlator. We are able to detect different scaled versions of the target in the same scene up to a magnification factor equal to 2. Each scale factor is codified in a different wavelength so each scaled version of the target is detected with a correlation peak of different wavelength. Experimental results demonstrate the proposed technique and show the utility of the method here introduced.
We propose and experimentally verify an automatic method for 3D shape detection. We project a grating onto the object to be checked in order to obtain a distorted grating pattern. This distorted pattern carries information about the complete 3D shape, so that their comparison with a reference one provides a method for detecting 3D objects in real time.
Morphological and rank-order filtering can be performed by combining linear operations and thresholding. In this review we present several approaches for the optoelectronic implementation of these operations. The systems based on this architectures are able to deal with realistic size images at high frame rates. Additionally, the same concepts are applied to nonlinear correlators based on thresholding and linear correlation. The main features, owing to the nonlinearity of the process, are the higher discrimination and the selectivity to target intensity, with independence of the global image intensity.
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