The advances in the field of adaptive optics and in the fabrication of tunable optical components capable to automatically modify their physical features are of great interest in areas like machine vision, imaging systems, ophthalmology, etc. Such components like tunable lenses are used to reduce the overall size of optical setups like in small camera systems and even to imitate some biological functions made by the human eye. In this direction, in the last years we have been working in the development and fabrication of PDMS-made tunable lenses and in the design of special mechanical mounting systems to manipulate them. A PDMS-made tunable lens was previously designed by us, following the scheme reported by Navarro et al. in 1985, in order to mimic the accommodation process made by the crystalline lens of the human eye. The design included a simulation of the application of radial stress onto the lens and it was shown that the effective focal length was indeed changed. In this work we show the fabrication process of this particular tunable lens and an optimized mechanism that is able to automatically change the curvature of both surfaces of the lens by the application of controlled stress. We also show results of a study and analysis of aberrations performed to the Solid Elastic Lens (SEL).
The pupil size of the human eye has a large effect in the image quality due to inherent aberrations. Several studies have been performed to calculate its size relative to the luminance as well as considering other factors, i.e., age, size of the adapting field and mono and binocular vision. Moreover, ideal lighting conditions are known, but software suited to our specific requirements, low cost and low computational consumption, in order to simulate radiation adaptation and image formation in the retina with ideal lighting conditions has not yet been developed. In this work, a database is created consisting of 70 photographs corresponding to the same scene with a fixed target at different times of the day. By using this database, characteristics of the photographs are obtained by measuring the luminance average initial threshold value of each photograph by means of an image histogram. Also, we present the implementation of a digital filter for both, image processing on the threshold values of our database and generating output images with the threshold values reported for the human eye in ideal cases. Some potential applications for this kind of filters may be used in artificial vision systems.
Tunable lenses have attracted much attention due to their potential applications in such areas like machine vision, laser projection, ophthalmology, etc. In this work we present the design of a tunable opto-mechatronic system capable of focusing and to regulate the entrance illumination that mimics the performance made by the iris and the crystalline lens of the human eye. A solid elastic lens made of PDMS has been used in order to mimic the crystalline lens and an automatic diaphragm has been used to mimic the iris of the human eye. Also, a characterization of such system has been performed with standard values of luminosity for the human eye have been taken into account to calibrate and to validate the entrance illumination levels to the overall optical system.
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