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As a unique natural satellite of the Earth, the Moon has always attracted much attention, and one subject of interest is the establishment of an Earth observation platform on the Moon. Compared with the existing spaceborne and airborne observation platforms, a Moon-based Earth observation platform would have the unique advantage of the ability to obtain global and large-scale observation data. At present, the study on Moon-based Earth observations is in theory, so it is necessary to use simulation methods to understand the observation performance of a Moon-based Earth observation platform. In this study, a method for Moon-based Earth observation imaging simulation in the thermal infrared band is developed to study the Moon-based thermal infrared imaging process. The method comprises three parts, including the estimation of Moon-based imaging coverage, the acquisition of the radiation intensity at the entrance pupil, and the simulated image output from the Moon-based thermal infrared sensor. Then, the simulated results are validated with the existing spaceborne observation data. Results show that the absolute error of Moon-based thermal infrared simulations is between 1.3–5.7 K, the RMSE is between 1.38 – 3.12 K, and the relative error is between 0.44% – 2.12%, indicating that the thermal infrared imaging model can more realistically simulate the true conditions of ground surface and that a Moon-based Earth observation platform could observe the Earth in the thermal infrared band.

To evaluate the effect of visual axis positioning on the optical performance of the Tecnis MIOL and the Diff-aA MIOL. In this prospective, randomized comparative study, 70 eyes of 35 subjects with senile cataract were implanted with the spherical aberration–correcting diffractive, bifocal Tecnis ZLB00 IOL and 60 eyes of 30 age-matched subjects with the spherical aberration neutral, diffractive, bifocal Diffractiva IOL. Observation procedure was performed 1, 3, and 6 months postoperatively. Main outcome measures included uncorrected and corrected distance and near visual acuity, manifest refraction, ocular aberrations, and visual quality metrics with 2 mm and 4 mm pupil and the position of visual axis. At the 6-month visit, no significant difference was found in monocular and binocular uncorrected (UDVA) and corrected (CDVA) distance and near (UNVA, CNVA) visual acuity between the groups. Spherical and coma-like aberrations were similar measured with a 2-mm pupil, but with a 4-mm pupil, the SA was significantly larger (in negative direction) in the Diffractiva group. The higher-order Strehl ratio and MTF was significantly larger in the Diffractiva group measured at 2 mm entrance pupil; however, this difference disappeared by the 4-mm pupil measurements. Postoperative angle alpha distance had a significant influence on HO Strehl value. The size of angle alpha is a predictive factor of image quality by multifocal IOL patients. Trial registration number and date of registration: NCT04274088, 14.02.2020.

Purpose to evaluate the effects of kappa angle and intraocular orientation on the theoretical performance of asymmetric multifocal intraocular lenses (MIOL). Methods For a total of 21 corneal aberrations, a computational analysis simulated the implantation of a computationally designed MIOL. An image quality parameter (IQ) (visually modulated transfer function metric) was calculated for a 5.0-mm pupil and for three conditions: distance, intermediate, and near vision. The procedure was repeated for each eye after a rotation of the MIOL with respect to the cornea from 0o to 360o in 5o steps. Kappa angles from 0 to 900 microns, in 150 microns steps, combined with two two variants of MIOL centration were tested: in the corneal apex or in the center of the entrance pupil. A p-value ≤ 0.05 was considered significant. Results There were statistically significant differences of the IQ depending of the intraocular orientation of the MIOL. If kappa angle was increased, there was a statistically significant decrease of the IQ. The IQ maintained stable when the optimal intraocular orientation was re-calculated for each kappa angle. In general, the inter-variability of the results between subjects was very high. There were no strong evidences supporting that there exists a preferable centration point. Conclusions Our results suggest that kappa angle theoretically affects significantly the performance of asymmetric MIOL implantation. However, its negative effect can be compensated if a customized intraocular orientation is calculated taking into account the presence of the kappa angle.

An imaging system is designed with a liquid crystal (LC) lens as the focusing element. The aperture of the LC lens plays the role of the aperture stop of the system. An entrance pupil larger than t...

This work discusses a variation of the Double Donut Schmidt Camera (DDSC), originally proposed for the EUSO-FF (EUSO on Free Flyer) project and devoted to the observation of UHECRs from space with a threshold of about 5 * 10(19) eV for a 600 km altitude. Increasing the entrance pupil area by a factor similar to 3, and then lowering the energy threshold to about 8 EeV (assuming for the differential energy spectrum of UHECR's the index -2.7), the proposed system will allow the observation of some 'cosmogenic neutrino' events in the 10(18)-10(19) eV range, where most of their flux is expected. The scalability of the DDSC design and the high Technological Readiness Level (TRL5) reached in the last decade for ultra-light, deployable, active mirrors does not set conceptual limits on the possible diameter of the primary mirror. We then propose to scale up the optics until the UV light detector in the focal plane will fill the whole diameter of the fairing of the considered launcher (4.2 m diameter assumed as in EUSO-FF baseline for Ariane 5/6 class). This will make necessary to deploy the corrector plate in orbit, in order to accommodate it into the fairing. This technology is still to be evaluated, but as the plate has a small refractive power, its tolerances are much broader than those of the primary mirror and it should be technologically feasible. With this upgrade, EUSO-FF, in addition to detecting more UHECR events, could also act as a precursor of a UHE neutrino observatory from space, addressing the problems to be faced for its realization. (C) 2020 COSPAR. Published by Elsevier Ltd. All rights reserved.

Evidence from animal and human studies suggests that ocular growth is influenced by visual experience. Reduced retinal image quality and imposed optical defocus result in predictable changes in axial eye growth. Higher order aberrations are optical imperfections of the eye that alter retinal image quality despite optimal correction of spherical defocus and astigmatism. Since higher order aberrations reduce retinal image quality and produce variations in optical vergence across the entrance pupil of the eye, they may provide optical signals that contribute to the regulation and modulation of eye growth and refractive error development. The magnitude and type of higher order aberrations vary with age, refractive error, and during near work and accommodation. Furthermore, distinctive changes in higher order aberrations occur with various myopia control treatments, including atropine, near addition spectacle lenses, orthokeratology and soft multifocal and dual-focus contact lenses. Several plausible mechanisms have been proposed by which higher order aberrations may influence axial eye growth, the development of refractive error, and the treatment effect of myopia control interventions. Future studies of higher order aberrations, particularly during childhood, accommodation, and treatment with myopia control interventions are required to further our understanding of their potential role in refractive error development and eye growth.

Using the Richards–Wolf formula, we investigate the tight focusing of a cylindrical vector beam of second order using a high-numerical aperture lens confined by a ring aperture. It is shown that the area of energy backflow can be enlarged by the ring aperture, and that focusing light using a lens with a numerical aperture of 0.95 and a ring aperture, which limits the angle of the entrance pupil to 0.9 of the maximum value, allows us to increase the depth of the area of negative values of the Poynting vector projection onto the optical axis by a factor of four, with a slightly varying width of the region (this varies from 0.357 to 0.352 of the wavelength of the focused light). The ratio of the absolute values of the Poynting vector for reverse and direct flows is increased by a factor of 2.5.

The Debye–Wolfdiffraction integral is a powerful tool for computing the focused field of an illumination by a high numerical aperture (NA) objective lens. With the help of the fast Fourier Transform (FT) algorithm, this integral can be evaluated at a high processing speed. In general, the FT pair is the illumination field at the entrance pupil and the focused field in a transverse plane in the focal region, i.e., the xy-plane. To analyze the field distribution of special beams in a titled plane, conventional calculations require a stack of slices of fields in the xy-planes plane by plane. Here, we propose a modified FT-based diffraction integral algorithm that exhibits a direct FT connection between the illumination field and the field in an arbitrary plane in the focal volume. As a result, significant time saving is achieved with the proposed algorithm. The algorithm is verified by numerous simulations and should be helpful to quickly design holograms to shape complex focus used in holographic optical tweezers.

Virtual image distance (VID) is a key parameter in augmented reality (AR) or virtual reality (VR) systems and has a great influence on product performance and user experience. Therefore, it is very necessary to measure the VID accurately and efficiently. In this paper, we develop a VID measurement system which needs no mechanical scanning in the measurement process. The VID can be measured in a short period of time based on one single image generated by the AR/VR system. An image-telecentric lens is designed which is used to capture the virtual image. A diaphragm with two pinholes is placed at the entrance pupil plane of the imaging lens. When the imaging lens is not focused on the virtual image, the captured image contains two copies of the virtual image with a certain interval which is proportional to the VID in units of diopters. By calculating the interval, we can obtain the VID. A simulation is performed in LightTools to verify the effectiveness of the measurement system, and the result indicates that the measurement error is 5 mm when the virtual image is at 3 m.

A freeform pushbroom hyperspectral imager design was investigated as a combination of a freeform reflective triplet imager and a freeform reflective triplet spectrometer used in double-pass. The design operates at about F/2 with a 15-degree cross-track field-of-view and a 30 mm entrance pupil diameter. The design process led to achieving a small volume of less than 2 liters that fits comfortably within a 3U CubeSat geometry, exemplifying the compactness of this hyperspectral imager. We report the freeform sag departures and maximum slopes of the freeform surfaces, as well as the manufacturing tolerances together with an evaluation of the system stray light, all of which highlight the feasibility of a design in this class to be manufactured. This design uniquely positions itself on the landscape of compact hyperspectral imagers.

The achievable design space for three-mirror unobscured imagers utilizing freeform surfaces was mapped out. The smallest volume diffraction-limited design was targeted for each combination of field-of-view, F-number, and entrance pupil diameter.

The lens design problem for the 2021 IODC is to design a 100 mm focal length lens where if the lens is flipped end-to-end but the radii are not reversed in sign, the lens has to perform the same as in its original form. The lens is used monochromatically. The goal of the problem is to maximize the product of the entrance pupil diameter and the semi-field of view while holding the RMS wavefront error to ≤ 0.070 wave within the field of view. There were 43 entries from 13 different countries. Three different commercial lens design programs were used, along with four in-house programs. The winning entry from Damien Gawron has an entrance pupil diameter of 198.4083 mm and a semi-field of view of 90° for a merit function product of 17,857 out of a maximum possible 18,000.

Phase measuring deflectometry (PMD) is a competitive method for specular surface measurement that offers the advantages of a high dynamic range, non-contact process, and full field measurement, furthermore, it can also achieve high accuracy. Camera calibration is a crucial step for PMD. As a result, a method based on the calibration of the entrance pupil center is introduced in this paper. Then, our proposed approach is compared with the most popular photogrammetric method based on Zhang’s technique (PM) and Huang’s modal phase measuring deflectometry (MPMD). The calibration procedures of these three methods are described, and the measurement errors introduced by the perturbations of degrees of freedom in the PMD system are analyzed using a ray tracing technique. In the experiment, a planar window glass and an optical planar element are separately measured, and the measurement results of the use of the three methods are compared. The experimental results for the optical planar element (removing the first 6 terms of the Zernike polynomial) show that our method’s measurement accuracy reached 13.71 nm RMS and 80.50 nm PV, which is comparable to accuracy values for the interferometer.