We present a new adaptive optics visual simulator (AOVS), allowing to both measure and manipulate the optical aberrations of the eye of any patient, including those with large refractive errors. The instrument incorporates a Hartmann-Shack wavefront sensor (HS), a liquid crystal on silicon spatial light modulator (LCOS-SLM), and a variable lens. A motorized diaphragm with a variable diameter ranging from 0.5 to 8.2 mm was incorporated at the exit pupil plane of the instrument, permitting visual testing for any pupil size. Presenting of visual stimuli was done using a high definition digital light processing projector (DLP), which provided provided bright, realistic visual conditions, enabling photopic vision. The AO visual simulator has been successfully proved in real subjects, including those exhibiting moderate and high levels of myopia. The AOVS was successfully tested in different subjects, including those exhibiting moderate and high levels of myopia. Aberrations were measured with the HS after pre-compensation of defocus with the variable lens, and LCOS-SLM corrected for the rest of aberrations. This visual simulator could be used in most patients, irrespectively of their refraction or the amount of aberrations.
Cataracts is a common ocular pathology that increases the amount of intraocular scattering. It degrades the quality of vision by both blur and contrast reduction of the retinal images. In this work, we propose a non-invasive method, based on wavefront shaping (WS), to minimize cataract effects. For the experimental demonstration of the method, a liquid crystal on silicon (LCoS) spatial light modulator was used for both reproduction and reduction of the realistic cataracts effects. The LCoS area was separated in two halves conjugated with the eye’s pupil by a telescope with unitary magnification. Thus, while the phase maps that induced programmable amounts of intraocular scattering (related to cataract severity) were displayed in a one half of the LCoS, sequentially testing wavefronts were displayed in the second one. Results of the imaging improvements were visually evaluated by subjects with no known ocular pathology seeing through the instrument. The diffracted intensity of exit pupil is analyzed for the feedback of the implemented algorithms in search for the optimum wavefront. Numerical and experimental results of the imaging improvements are presented and discussed.
The PAU (Physics of the Accelerating Universe) project goal is the study of dark energy with a new photometric technique aiming at obtaining photo-z resolution for Luminous Red Galaxies (LRGs) roughly one order of magnitude better than current photometric surveys. To accomplish this, a new large field of view camera (PAUCam) has been built and commissioned at the William Herschel Telescope (WHT). With the current WHT corrector, the camera covers ~1 degree diameter Field of View (FoV). The focal plane consists of 18 2kx4k Hamamatsu fully depleted CCDs, with high quantum efficiency up to 1 μm. To maximize the detector coverage within the FoV, filters are placed in front of the CCD's inside the camera cryostat (made of carbon fiber material) using a challenging movable tray system. The camera uses a set of 40 narrow band filters ranging from ~4400 to ~8600 angstroms complemented with six standard broad-band filters, ugrizY. Here, we describe the camera and its first commissioning results. The PAU project aims to cover roughly 100 square degrees and to obtain accurate photometric redshifts for galaxies down to iAB ~ 22:5 detecting also galaxies down to iAB ~ 24 with less precision in redshift. With this data set we will obtain competitive constraints in cosmological parameters using both weak lensing and galaxy clustering as main observational probes.
The Physics of the Accelerating Universe (PAU) is a project whose main goal is the study of dark energy. For this purpose, a new large field of view camera (the PAU Camera, PAUCam) is being built. PAUCam is designed to carry out a wide area imaging survey with narrow and broad band filters spanning the optical wavelength range. The PAU Camera is now at an advance stage of construction. PAUCam will be mounted at the prime focus of the William Herschel Telescope. With the current WHT corrector, it will cover a 1 degree diameter field of view. PAUCam mounts eighteen 2k×4k Hamamatsu fully depleted CCDs, with high quantum efficiency up to 1 μm. Filter trays are placed in front of the CCDs with a technologically challenging system of moving filter trays inside the cryostat. The PAU Camera will use a new set of 42 narrow band filters ranging from ~4400 to ~8600 angstroms complemented with six standard broad-band filters, ugrizY. With PAUCam at the WHT we will carry out a cosmological imaging survey in both narrow and broad band filters that will perform as a low resolution spectroscopic survey. With the current survey strategy, we will obtain accurate photometric redshifts for galaxies down to iAB~22.5 detecting also galaxies down to iAB~24 with less precision in redshift. With this data set we will obtain competitive constraints in cosmological parameters using both weak lensing and galaxy clustering as main observational probes.
The Physics of the Accelerating Universe (PAU) is a new project whose main goal is to study dark energy surveying the
galaxy distribution. For that purpose we need to determine the galaxy redshifts. The most accurate way to determine the
redshift of a galaxy and measure its spectral energy distribution (SED) is achieved with spectrographs. The PAU
collaboration is building an instrument (PAUCam) devoted to perform a large area survey for cosmological studies using
an alternative approach. SEDs are sampled and redshifts determined using narrow band filter photometry. For efficiency
and manufacturability considerations, the filters need to be placed close to the CCD detector surfaces on segmented filter
trays. The most innovative element of PAUCam is a set of 16 different exchangeable trays to support the filters arranged
in a jukebox-like changing mechanism inside the cryostat. The device is designed to operate within the range of
temperatures from 150K to 300K at the absolute pressure of 10-8mbar, being class-100 compliant.
The Physics of the Accelerating Universe (PAU) collaboration aims at conducting a competitive cosmology experiment.
For that purpose it is building the PAU Camera (PAUCam) to carry out a wide area survey to study dark energy.
PAUCam has been designed to be mounted at the prime focus of the William Herschel Telescope with its current optical
corrector that delivers a maximum field of view of ~0.8 square degrees. In order to cover the entire field of view
available, the PAUCam focal plane will be populated with a mosaic of eighteen CCD detectors. PAUCam will be
equipped with a set of narrow band filters and a set of broad band filters to sample the spectral energy distribution of
astronomical objects with photometric techniques equivalent to low resolution spectroscopy. In particular it will be able
to determine the redshift of galaxies with good precision and therefore conduct cosmological surveys. PAUCam will also
be offered to the broad astronomical community.
A novel adaptive optics system is presented for the study of vision. The apparatus is capable for binocular operation. The
binocular adaptive optics visual simulator permits measuring and manipulating ocular aberrations of the two eyes
simultaneously. Aberrations can be corrected, or modified, while the subject performs visual testing under binocular
vision. One of the most remarkable features of the apparatus consists on the use of a single correcting device, and a
single wavefront sensor (Hartmann-Shack). Both the operation and the total cost of the instrument largely benefit from
this attribute. The correcting device is a liquid-crystal-on-silicon (LCOS) spatial light modulator. The basic performance
of the visual simulator consists in the simultaneous projection of the two eyes' pupils onto both the corrector and sensor.
Examples of the potential of the apparatus for the study of the impact of the aberrations under binocular vision are
presented. Measurements of contrast sensitivity with modified combinations of spherical aberration through focus are
shown. Special attention was paid on the simulation of monovision, where one eye is corrected for far vision while the
other is focused at near distance. The results suggest complex binocular interactions. The apparatus can be dedicated to
the better understanding of the vision mechanism, which might have an important impact in developing new protocols
and treatments for presbyopia. The technique and the instrument might contribute to search optimized ophthalmic
Three-dimensional ultrahigh resolution optical coherence tomography (UHR OCT) and adaptive optics (AO) are combined using a liquid crystal programmable phase modulator (PPM) as a correcting device for the first time. AO is required for correcting ocular aberrations in moderate and large pupils in order to achieve high resolution retinal images. The capabilities of the PPM are studied using polychromatic light. Volumetric UHR OCT images of the living retina with AO, obtained with up 25000 A scans/s and high resolution (~5x5x3 μm; transverse (x) x transverse (y) x axial) are recorded, enabling visualization of interesting intraretinal morphological structures. Cellular retinal features, which might correspond to groups of terminal bars of photoreceptors at the level of the external limiting membrane, are resolved. Benefits and limitations of the presented technique are finally discussed.