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We demonstrate the potential of Vertical-Aligned Spatial Light Modulators in adaptive-optics visual simulators. The induction and correction of low and high order aberrations was evaluated by testing visual acuity and contrast sensitivity in healthy subjects.

We present a system for imaging objects through non-homogeneous scattering media that works in an adaptive way by combining diffuse optical imaging (DOI) and single-pixel imaging (SPI) techniques. The experimental results are shown.

In this work we propose a non-invasive alternative to cataracts surgery by means of manipulating the wavefront of the incident light. We show a two-fold improvement in the Strehl ratio of the ocular Point Spread Function.

Cataract is one of the common causes of visual impairment due to opacification of the crystalline lens. Increased intraocular scattering affects the vision of cataract patients by reducing the quality of the retinal image. In this study, an amplitude modulation-based scatter compensation (AM-SC) method is developed to minimize the impact of straylight on the retinal image. The performance of the AM-SC method was quantified by numerical simulations of point spread function and retinal images in the presence of different amounts of straylight. The approach was also experimentally realized in a single-pass system with a digital micro-mirror device used as a spatial amplitude modulator. We showed that the AM-SC method allows to enhance contrast sensitivity in the human eyes in vivo with induced scattering.

In this work we present the Adaptive Optics Visual Simulator (VAO) and show the potential of Adaptive Optics in visual diagnostic and simulation, for a complete and fully personalized vision characterization.

In this work we propose a non-invasive alternative to cataracts surgery by means of manipulating the wavefront of the incident light. We show an improvement of 80 in the Strehl ratio of the ocular Point Spread Function.

Cataracts are a common ocular pathology involving an increase in the amount of intraocular light scattering. This causes vision impairment by blurring and reducing the contrast in retinal images. The current treatment for this pathology is cataract surgery, which is an invasive procedure with possible side effects, such as corneal edema, infection or retinal detachment among others. In this work, we propose a non-invasive approach to improve vision through the cataractous lenses by manipulating the wavefront of the incident light. By using a fluorescent signal as feedback (similar to the inherent fluorescence of the lipofuscin pigment at the retina) we show the capability of improving the point spread function (PSF) of the eye in a single pass through the artificial eye’s optics, while the feedback signal is measured in a double-pass configuration, making the whole system completely non-invasive, opening new possibilities for real-time vision correction through cataracts with wearable devices.

Ghost imaging is an unconventional optical imaging technique that reconstructs the shape of an object combining the measurement of two signals: one that interacted with the object, but without any spatial information, the other containing spatial information, but that never interacted with the object. Ghost imaging is a very flexible technique, that has been generalized to the single-photon regime, to the time domain, to infrared and terahertz frequencies, and many more conditions. Here we demonstrate that ghost imaging can be performed without ever knowing the patterns illuminating the object, but using patterns correlated with them, doesn't matter how weakly. As an experimental proof we exploit the recently discovered correlation between the reflected and transmitted light from a scattering layer, and reconstruct the image of an object hidden behind a scattering layer using only the reflected light, which never interacts with the object. This method opens new perspectives for non-invasive imaging behind or within turbid media., 5 pages, 4 figures

Spatial Light Modulators (SLMs) are widely used in several fields of optics such as adaptive optics. SLMs based on Liquid Crystal (LC) devices allow a dynamic and easy representation of two-dimensional phase maps. A drawback of these devices is their elevated cost, preventing a massive use of the technology. We present a more affordable approach based on the serial arrangement of vertical aligned LC devices, with characteristics of phase modulation similar to a widely used parallel aligned LC device. We discuss the peculiarities of the approach, the performance and some potential areas of applications.

Light scattering limits the penetration depth of non-invasive Raman spectroscopy in biological media. While safe levels of irradiation may be adequate to analyze superficial tissue, scattering of the pump beam reduces the Raman signal to undetectable levels deeper within the tissue. Here we demonstrate how wavefront shaping techniques can significantly increase the Raman signal at depth, while keeping the total irradiance constant, thus increasing the amount of Raman signal available for detection.

When light passes through a disordered medium, its wavefront is scrambled, resulting in a seemingly random speckle pattern. In the multiple scattering regime, it is commonly assumed that this randomization removes any memory about the original wavefront, effectively destroying all its information content. But as linear elastic scattering is a purely deterministic process, information is not destroyed, but just hidden and redistributed within these patterns. We present an experimental observation of the correlations between reflected and transmitted speckle patterns, which indicate that information can survive even very strong scattering. We show that there are two distinct contributions to the correlation function - a narrow positive peak and a broad negative dip, which depend in a different way on the system parameters. We study the dependence of this correlation on the thickness of the scattering medium and the mean free path of the light in the sample, probing different regimes from ballistic to diffusive scattering. We propose an experimental procedure, based on the ghost imaging technique, that allows to use this correlation for imaging of the objects hidden behind the scattering media.

We propose a novel technique for imaging through opaque multiply scattering media, based on mesoscopic correlations between the reflected and transmitted speckle patterns.

When light propagates in a turbid medium, multiple scattering prevents it from reaching depths much greater than the mean free path. This limited propagation presents a problem for many fields where optical energy delivery through scattering media is critical, such as energy conversion in dye-sensitized solar cells, light-based medical techniques, or white LEDs. In this work we show that wavefront shaping techniques can significantly increase the delivery of optical energy through strongly scattering media.

Cataracts increase the amount of scattered light in the crystalline lens producing low-contrast retinal images and causing vision impairment. The Optical Memory Effect is a wave correlation of coherent fields, which can enable imaging through scattering media. In this work, we characterize the scattering properties of excised human crystalline lenses by measuring their optical memory effect and other objective scattering parameters, finding the relationship between them. This work has the potential to help fundus imaging techniques through cataracts as well as the non-invasive correction of vision through cataracts.