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Pinero D.P.,Medimar International Hospital | Pinero D.P.,University of Alicante | Alcon N.,Medimar International Hospital | Alcon N.,Instituto Tecnologico Of Optica
Journal of Cataract and Refractive Surgery | Year: 2014

Interest in corneal biomechanics has increased with the development of new refractive surgery techniques aimed at modifying corneal properties and a variety of surgical options for corneal ectasia management. The human cornea behaves as soft biological material. It is a viscoelastic tissue and its response to a force applied to it depends not only on the magnitude of the force, but also on the velocity of the application. There are concerns about the limitations to measuring corneal biomechanical properties in vivo. To date, 2 systems are available for clinical use: the Ocular Response Analyzer, a dynamic bidirectional applanation device, and the Corvis ST, a dynamic Scheimpflug analyzer device. These devices are useful in clinical practice, especially for planning some surgical procedures and earlier detection of ectatic conditions, but further research is needed to connect the clinical measurements obtained with these devices to the standard mechanical properties. Financial Disclosure Neither author has a financial or proprietary interest in any material or method mentioned. © 2014 ASCRS and ESCRS.

Pinero D.P.,Medimar International Hospital | Pinero D.P.,Foundation for the Visual Quality | Pinero D.P.,University of Alicante | Alcon N.,Instituto Tecnologico Of Optica
Clinical and Experimental Optometry | Year: 2015

Biomechanics is often defined as 'mechanics applied to biology'. Due to the variety and complexity of the behaviour of biological structures and materials, biomechanics is better defined as the development, extension and application of mechanics for a better understanding of physiology and physiopathology and consequently for a better diagnosis and treatment of disease and injury. Different methods for the characterisation of corneal biomechanics are reviewed in detail, including those that are currently commercially available (Ocular Response Analyzer and CorVis ST). The clinical applicability of the parameters provided by these devices are discussed, especially in the fields of glaucoma, detection of ectatic disorders and orthokeratology. Likewise, other methods are also reviewed, such as Brillouin microscopy or dynamic optical coherence tomography and others with potential application to clinical practice but not validated for in vivo measurements, such as ultrasonic elastography. Advantages and disadvantages of all these techniques are described. Finally, the concept of biomechanical modelling is revised as well as the requirements for developing biomechanical models, with special emphasis on finite element modelling. © 2014 Optometry Australia.

Portales C.,Instituto Tecnologico Of Optica | Portales C.,University of Valencia | Ribes-Gomez E.,Instituto Tecnologico Of Optica
Computers in Industry | Year: 2015

In this paper we present a hardware system and related computer processes to assess a preliminary quality control of grape harvest batches by automatically detecting, classifying and quantifying grape stems and other objects from images acquired on arrival at the winery, from which a quality grading is given. A non-invasive methodology based on computer vision is implemented, and the developed approach is based on the combination of a spectral and spatial analysis, where the inspection is performed in a small region of the near infrared (from 1000 to 1100 nm range). A non-expensive optical system was designed, which is composed of two high resolution CCD cameras, a long pass filter, some halogen light sources, related electronics and a standard PC. The performance of the optical system and implemented computer vision-based algorithms were tested in a laboratory setup for repeatability and overall accuracy while operating outdoors and over a whole working day, with varying illumination conditions. The system response presented small variations when estimating the occurrences of grape stems or other objects in the scene under analysis. The best results - lowest standard deviations and lowest root mean square errors - were obtained for the system working with added artificial lights and for the analysis being performed in the green channel. The system was also installed at a winery, where operators tested it for its good performance in a real scenario. The system worked as expected and the outcomes show that it is a robust and intuitive inspection system. © 2014 Elsevier B.V. All rights reserved.

Wallhead I.,Hyperion Development Europe | Ocana R.,Instituto Tecnologico Of Optica
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

Laser projection devices should be designed to maximize their luminous efficacy and color gamut. This is for two main reasons. Firstly, being either stand alone devices or embedded in other products, they could be powered by battery, and lifetime is an important factor. Secondly, the increasing use of lasers to project images calls for a consideration of eye safety issues. The brightness of the projected image may be limited by the Class II accessible emission limit. There is reason to believe that current laser beam scanning projection technology is already close to the power ceiling based on eye safety limits. Consequently, it would be desirable to improve luminous efficacy to increase the output luminous flux whilst maintaining or improving color gamut for the same eye-safe optical power limit. Here we present a novel study about the combination of four laser wavelengths in order to maximize both color gamut and efficacy to produce the color white. Firstly, an analytic method to calculate efficacy as function of both four laser wavelengths and four laser powers is derived. Secondly we provide a new way to present the results by providing the diagram efficacy vs color gamut area that summarizes the performance of any wavelength combination for projection purposes. The results indicate that the maximal efficacy for the D65 white is only achievable by using a suitable combination of both laser power ratios and wavelengths. © 2014 Copyright SPIE.

Wallhead I.,Instituto Tecnologico Of Optica | Jimenez T.M.,Instituto Tecnologico Of Optica | Garcia Ortiz J.V.,Benjamin Franklin Bancorp | Toledo I.G.,Benjamin Franklin Bancorp | Toledo C.G.,Benjamin Franklin Bancorp
Optics Express | Year: 2012

A novel of Fresnel-type lens for use as a solar collector has been designed which utilizes double total internal reflection (D-TIR) to optimize collection efficiency for high numerical aperture lenses (in the region of 0.3 to 0.6 NA). Results show that, depending on the numerical aperture and the size of the receiver, a collection efficiency theoretical improvement on the order of 20% can be expected with this new design compared with that of a conventional Fresnel lens. © 2012 Optical Society of America.

Candel J.J.,Polytechnic University of Valencia | Amigo V.,Polytechnic University of Valencia | Ramos J.A.,Instituto Tecnologico Of Optica | Busquets D.,Polytechnic University of Valencia
Welding International | Year: 2013

The aim of the present work is to establish the relationship between laser cladding (LC) process parameters (power, process speed, and powder feed rate) and AISI D2 tool steel metallurgical transformations, with the objective of optimizing the processing conditions during real reparation. It has been deposited H13 tool steel powder on some steel substrates with different initial metallurgical status (annealed or tempered) using a coaxial LC system. The microstructure of the laser clad layer and substrate heat-affected zone (HAZ) was characterized by optical microscopy, scanning electron microscopy, and electron backscattered diffraction. Results show that the process parameters (power, process speed, feed rate, etc.) determine the dimensions of the clad layer and are related to the microstructure formation. Although it is simple to obtain geometrically acceptable clads (with the right shape and dimensions) in many cases some harmful effects occur, such as carbide dilution and non-equilibrium phase formation, which modify the mechanical properties of the coating. Specifically, the presence of retained austenite in the substrate-coating interface is directly related to the cooling rate and implies a hardness diminution that must be avoided. It has been verified that initial metallurgical state of the substrate has a big influence in the final result of the deposition. Tempered substrates imply higher laser absorption and heat accumulation than the ones in annealed condition. This produces a bigger HAZ. For this reason, it is necessary to optimize the process conditions for each repair in order to improve the working behaviour of the component. © 2013 Copyright Taylor and Francis Group, LLC.

Wallhead I.,Instituto Tecnologico Of Optica | Ocana R.,Instituto Tecnologico Of Optica | Quinza P.,Instituto Tecnologico Of Optica
Applied Optics | Year: 2012

When designing a laser scanning picoprojector, one has to deal with important aspects that do not strictly involve design of hardware and software. We have identified two issues that play a decisive role in the final specifications of a laser scanning picoprojector: the characteristics of the optical displaying system and color management. Regarding the optical system, we have studied the diameter requirements of the laser beam emitted from a picoprojector from the point of view of image quality. Resolution is assessed by calculating the image modulation produced by a projected laser spot over a range of projection distances and image sizes. We also show that a suitable election of the RGB wavelengths increases the lumensperwatt ratio and thereby improves efficiency of a laser-based picoprojector. © 2012 Optical Society of America.

Wallhead I.,Instituto Tecnologico Of Optica | Ocana R.,Instituto Tecnologico Of Optica | Quinza P.,Instituto Tecnologico Of Optica
Applied Optics | Year: 2012

Laser scanning picoprojectors present a new challenge in the field of laser safety with methods of calculating accessible emission limits still in their infancy. We present a laser safety analysis and a calculation of an example picoprojector. We show that, due to its scanning operation, a picoprojector should be considered an extended laser source, and we also show that a picoprojector with two separate one-axis microelectromechanical systems mirrors offers a higher safe power limit than a projector with a single scanning mirror. Finally, a safety analysis is done under conditions of mirror failure.We show that, if the projector fails to scan in just one of the axes, the ocular hazard rises sharply, highlighting the need for a fail-safe system to be built into laser scanning picoprojectors. © 2012 Optical Society of America.

Wallhead I.,Instituto Tecnologico Of Optica | Ocana R.,Instituto Tecnologico Of Optica
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

The optical design of a laser scanning picoprojector can be separated into discrete tasks. Typically, red green and blue solid state lasers are employed and their highly divergent emission is firstly collimated. The beams then need to be shaped from elliptical to round and combined into a single beam. The final step of the process is to direct the combined beam towards a MEMS scan head comprising a single, bi-axis or two, single axis scamiing micro-mirrors. All this has to be done in a small space to embed the picoprojector opto-electro-mechanics into other devices such as smart phones. So along with conventional optical engineering tasks such as lens design, Gaussian beam propagation, tolerancing, laser safety and design for manufacture, there is an additional task of determining the best optical architectum to achieve the goal. Here we present a design study of a laser scamiing picoprojector where the various optical architecture possibilities are presented. A novel solution is presented which has been built as a prototype projector and which offers excellent future miniaturization possibilities. © 2012 SPIE.

Ocana R.,Instituto Tecnologico Of Optica | Molina T.,Instituto Tecnologico Of Optica
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

The laser-diode self-mixing technique is a well-known, powerful, very simple and low cost interferometric technique. The typical structure of a laser-diode self-mixing device is made up of a laser-diode, a focusing lens and a processing unit. One can find in literature numerous examples of target displacement, fluid flow, velocity, distance and vibration measurements. Regarding vibration measurements, the self-mixing effect has been mainly applied to measure amplitude and frequency in isolated points but it is dificult to find real applications in which this technique is applied to measure the vibrating behavior of a complete surface. This is due to the different feedback signals that may appear when a laser beam is scattered by a real rough surface. When scanning a surface, the different speckle patterns that contain the feedback signal at different points introduce big changes in the intensity of the scattered signal captured by the photodiode that drives the laser into a strong coupling self-mixing regime with loss of the sinusoidal behavior of the fringes. In many cases, saturation of the photodiode is also found. When this occurs, it is not possible to measure any vibration parameter. By programming simple algorithms, this problem can be overcome. Here we present vibration measurements of titanium tweeter membranes up to 6.8 Khz that show the vibrating behavior in the micrometer range. We demonstrate that the limit in the frequency range is set by the sample frequency of the data acquisition device. Results are compared with different optical techniques for mapping vibrating surfaces such as laser triangulation and electronic speckle pattern interferometry. © 2014 SPIE.

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