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Charged particles in the space environment can degrade the scientific performances of X-ray detectors in astronomical telescopes. An efficient countermeasure is to place a magnetic diverter at the exit pupil of optics to deflect charged particles away from the sensitive detection area. In this work, we have performed a preliminary design of the magnetic diverter on-board the enhanced X-ray Timing and Polarimetry (eXTP) observatory. It relies on a Monte Carlo method via the GEANT4 toolkit to simulate the mirror responses to charged particles, using the single scattering physics for electrons and the elastic Remizovich physics for protons. It also implements a numerical method to calculate magnetic fields generated by an assembly of permanent magnets and its impact on the trajectories of charged particles. The compact calculation scheme provides efficient access to the background level estimation given the certain radiation environment, which enables the verification of the diverter configuration with the scientific requirements.

Main properties of holographic waveguide periscopic multiplexors of the exit pupil of optical systems of augmented reality displays are considered. Limitations in the operation of waveguide holograms, compensation of chromatic aberrations in periscopic schemes, and influence of waveguide defects on the operation of augmented reality displays constructed based on waveguide holograms are analyzed.

Four of the most viable glasses-free three-dimensional display methods were chosen for our research at NTU's Advanced Displays Laboratory. Our multilayer light field display enables a smaller form factor. Faster algorithms combined with horizontal parallax-only speed-up Tensor Display computation time. A spin-off from this is an augmented reality light field near-eye display with focus cues. Our head-tracked displays use a directional backlit liquid crystal display panel to produce multiple sets of exit pupil pairs that employ a head tracker to follow the users’ eyes. This enables a ‘plug and play solution’ where existing content can be used without resolution loss. We have developed three different spatio-temporally multiplexed super multiview display systems based on liquid crystal displays, organic light-emitting diodes and fast projectors. In this article, the background, status of the prototypes and their performance are explained, and the future direction of our research is described.

We review, with proper derivation and proofs, the common undergraduate formulas for building images of objects using a system of lenses with spherical surfaces. This is done using the first-order approximation which assumes that light rays deviate from the symmetry axis by only small angles. Yet, even this most basic approximation results in surprisingly complex theory, which is then applied to explain workings of everyday optical instruments.

In this paper, it is proven that for any optical system with a circular exit pupil and wavefronts affected by any aberrations, the borders of all leaving rays are caustic surfaces and/or marginal rays. Several examples are shown for wavefronts affected by linear combinations of Zernike aberrations.

In standard photography, vignetting is considered mainly as a radiometric effect because it results in a darkening of the edges of the captured image. In this paper, we demonstrate that for light field cameras, vignetting is more than just a radiometric effect. It modifies the properties of the acquired light field and renders most of the calibration procedures from the literature inadequate. We address the problem by describing a model and camera-agnostic method to evaluate vignetting in phase space. This enables the synthesis of vignetted pixel values, which applied to a range of pixels yield images corresponding to the white images that are customarily recorded for calibrating light field cameras. We show that the commonly assumed reference points for microlens-based systems are incorrect approximations to the true optical reference, i.e., the image of the center of the exit pupil. We introduce a novel calibration procedure to determine this optically correct reference point from experimental white images. We describe the changes vignetting imposes on the light field sampling patterns and, therefore, the optical properties of the corresponding virtual cameras using the equivalent camera array model [L. Mignard-Debise, J. Restrepo, and I. Ihrke, “A unifying first-order model for light-field cameras: The equivalent camera array,” IEEE Trans. Comput. Imag. , vol. 3, no. 4, pp. 798–810, Dec. 2017] and apply these insights to a custom-built light field microscope.

As the development of electro-optical weapon system, the technique of multi-sensor is used popular. A visual telescope based on a television viewing-aim system has been designed in this paper, which has the common aperture. The optical system which used visual telescope as optical reference of correcting the optical axis, share the same objective and compound prism, and has been applied to versatile optic-electronic observation with coating beam-splitting film on inclined plane of the block prism. A visual telescope system has been presented, which has been inverted image with a Schmidt roof-prism. As a result, a visual telescope could be used to aim target by the eye at exit pupil, which magnification is 10×, field of view is 5°,exit pupil isφ6mm, exit distance is not less than 20mm, the optical resolution is not more than 5″.There is a very important point, that compound prism has been applied in visual telescope optical system, which cause not only reversed image but also turned 45°optical path to meet the requirement of man-machine. Furthermore, owing to high resolution and maximum probability of distinguish, a CMOS digital camera based on cameral link has been used in the television viewing-aim system, which resolution is 1024× 768, the pixel size is 4 μm. So a television viewing-aim system is made up of telephoto objective to shorten optical length, which has F number 4 and 1°×0.75°field of view in near infrared wavelength. And the system could be used to detect, distinguish and aim target by getting reflect characteristic of the target and converting video image in real time. Finally, according to the analysis of tolerance, the fabrication and assembly tolerance are has been formulated, the result could meet the imaging demands.

As an important evaluation specification of the helmet mounted display, binocular alignment directly affects the imaging quality of the helmet mounted display, such as the imaging distance and the imaging clarity, and then has a vital impact on the combat effectiveness of the pilot and the aircraft. The traditional detection method relies on the human eye to align the collimator for subjective interpretation, the results are often uncertain because different people have different feelings. This paper proposes an automatic measurement method of binocular alignment based on a single digital camera. This method combines the binocular images of the helmet mounted display into the same optical path by placing a turning prism at the binocular exit pupil position of the helmet mounted display, thereby achieving the purpose of synchronously collecting binocular images by using a single digital camera. Digital image processing technology realizes automatic calculation of binocular alignment indicators, which greatly improves the measurement accuracy and the measurement efficiency. This method uses a turning prism to merge the binocular images of the helmet mounted display into one optical path. The camera can collect binocular images without moving during the measurement process, so it can avoid the straightness error caused by the use of a translation stage, and finally an objective, accurate and fast measurement of binocular alignment specification is obtained. At last, this article discusses the measurement principle of the method in detail, explains the optical-mechanical structure of the binocular alignment measurement equipment in detail, and analyzes the measurement accuracy. Finally, several binocular alignment test results are compared. The test results show that this method has obvious advantages in the measurement accuracy and the measurement efficiency. It can meet the needs of fast, accurate and objective measurement of the binocular alignment of the helmet mounted display, and has the value of a wide range of applications.

Illumination non-uniformity caused by the multiple total internal reflection has become an important factor restricting the development of grating- based AR devices. Most of the current solutions can effectively modulate the distribution of diffraction efficiency (DE) of different diffraction orders by adjusting the groove parameters of the diffraction grating, so as to optimize the exit pupil uniformity of the diffraction grating waveguide. In this paper, an out-coupling grating with variable duty cycle is fabricated by a new way to improve the performance of diffraction grating waveguides. The ashing process is chosen to modulate the duty cycle, which can chemically react with the photoresist without damaging the grating substrate. Based on the relationship between the ashing time and the shrinking rate of the duty cycle, the grating coupler can be fabricated to meet the optimized results. The diffraction efficiency of the gratings is tested. The results show that the method we proposed is reliable and effective to produce continuously variable duty cycle gratings. The diffraction efficiency of the grating is gradually improved along the direction of exit pupil expansion, which is beneficial to the display device to achieve more uniform output brightness.

Currently most of the holographic waveguide near-eye display are based on flat waveguide structure. It is always required to add curved goggles for head mounted display (HMD) or helmet display. And consequently, the human eyes have to see through both the flat waveguide and the curved goggles when viewing see-through background. It suffers from bulky form-factor, low transmittance and limited application. Therefore, this paper proposes a near-eye display system based on curved holographic waveguide, which integrates both flat waveguide and curved goggles. This design includes cylindrical holographic waveguide and corresponding micro projection module. To ensure the rays transmitted regularly in the waveguide, we designed special holographic optical elements (HOEs) attached on the surface of cylindrical waveguide to achieve large exit pupil and field of view (FOV). Besides, the aspheric lenses in the micro projection module are employed to correct aberration caused by cylindrical waveguide. This novel design of the proposed HMD with cylindrical waveguide can achieve a binocular FOV of about 42° in diagonal, an eye relief of 15mm and exit pupil of 10mm×10mm. For the central FOV, the modulation transfer function is close to the diffraction limit, and the intensity is uniformly distributed at the exit pupil with high light efficiency. For the edge FOV, the image quality is still good and suitable for the human eye. This novel design integrates the waveguide with curved goggles into one curved waveguide based near-eye display, which can provide a new approach for portable near-eye display applied in the helmet or some other related usages.

8 pags., 8 figs., Multifocal lenses comprising progressive power surfaces are commonly used in contact and intraocular lens designs. Given a visual performance metric, a wavefront engineering approach to design such lenses is based on searching for the optimal wavefront at the exit pupil of the eye.Multifocal wavefronts distribute the energy along the different foci thanks to having a varying mean curvature. Therefore, a fundamental step in the wavefront engineering approach is to generate the wavefront from a prescribed mean curvature function. Conventionally, such a thing is done by superimposing spherical wavefront patches and maybe adding a certain component of spherical aberration to each spherical patch in order to increase the depth-of-field associated with each focus. However, such a procedure does not lead to smooth wavefront solutions and also restricts the type of available multifocal wavefronts. We derive a new, to the best of our knowledge, mathematical method to uniquely construct multifocal wavefronts from mean curvature functions (depending on radial and angular coordinates) under certain numerically justified approximations and restrictions. Additionally, our procedure leads to a particular family of wavefronts (line-umbilical multifocal wavefronts) described by 2 conditions: (1) to be smooth multiplicative separable functions in the radial and angular coordinates; (2) to be umbilical along a specific segment connecting the circle center with its edge.We provide several examples of multifocal wavefronts belonging to this family, including a smooth variant of the so-called light sword element.

In this paper, we give a spatial frequency analysis of polarization imaging system and study the effects of rotational alignment errors of the polarizer from their ideal orientations. With the help of newly proposed Optical Transfer Matrix (OTM) for a diffraction-limited polarization imaging system, we investigate the effects of polarization-sensitive aberrations from the generalized pupil matrix at the exit pupil plane. Here, polarization aberrations stemming from the angular alignment errors of a linear polarizer has been demonstrated. The performance of a polarization imaging system with rotational alignment error has also been evaluated based on a cost function based on OTM.

In the field of endoscope optics we see more and more zoom designs, realized by tuneable lenses, micro actuators or traditional lens movement in rigid endoscopes with a camera sensor. For such devices, a lighting concept that adapts the beam angle to the current field of view of the zoom optics is desirable. In endoscopes, the light is usually transported from a source to the tip by a light guide or fiber bundle.1 Since it is not feasible to place an optical system at the fiber exit to fulfill the task, one would make use of the fact that a fiber roughly conserves the angular distribution of incident light and transfer the task of variable beam generation to the light source. We present an optical system that performs this task by conventional optical means outside the endoscope. A LED is imaged to the fiber entrance by a system of variable focal length. By choosing the source etendue equal to that of the fiber, it is ensured that the proper magnification of the imaging is accompanied by the specified angular extent. The LED light is first collimated, and the exit pupil of the collimator is imaged by a system of moving and fix lenses. In a final step, we show a design to adapt a colored light source to the variable beam optics.

In recent years, with technological advances, head-mounted display systems (HMDs) for virtual reality (VR) and augmented reality (AR) have been adopted for their applications in the military, government, education, training, medical visualization, aerospace, entertainment industries, and tourism. For this reason, a compact and light HMD but without sacrificing their performance is necessary. In this paper, the optical design of a lightweight and compact head-mounted display (HMD) system is proposed. We use an off-axis three-mirror system (OTS) with freeform surfaces for the correction of the aberrations and obtain a wide field of view (FOV), a compact structure with an exit pupil size over 7 mm and eye relief of 25 mm.

Angles subtended at the second nodal point of the eye (NP2) are approximately the same as input visual angles over a very large angular range, despite the nodal point being a paraxial lens property. Raytracing using an average pseudophakic eye showed that the angular nodal point criterion was only valid up to about 10°, and that the linear relationship was due instead to the cornea and lens initially creating chief ray angles at the exit pupil that are about 0.83 times input values for this particular eye, and then by the retina curving around to meet the rays in a manner that compensates for increasing angle. This linear relationship is then also maintained when retinal intersections are calculated relative to other axial points, with angles rescaled approximately using the equation R/(R + delta), where delta is the axial distance from the center of a spherical retina of radius R. Angles at NP2 approximately match the input angles, but the terminology is misleading because this is not a paraxial property of the eye. Chief rays are used with finite raytracing to determine the actual behavior.

A piston error detection method is proposed based on the broadband intensity distribution on the image plane using a back-propagation (BP) artificial neural network. By setting a mask with a sparse circular clear multi-subaperture configuration in the exit pupil plane of a segmented telescope to fragment the pupil, the relation between the piston error of segments and amplitude of the modulation transfer function (MTF) sidelobes is strictly derived according to the Fourier optics principle. Then the BP artificial neural network is utilized to establish the mapping relation between them, where the amplitudes of the MTF sidelobes directly calculated from theoretical relationship and the introduced piston errors are used as inputs and outputs respectively to train the network. With the well trained-network, the piston errors are measured to a good precision using one in-focused broadband image without defocus division as input, and the capture range achieving the coherence length of the broadband light is available. Adequate simulations demonstrate the effectiveness and accuracy of the proposed method, the results show that the trained network has high measurement accuracy, wide detection range, quite good noise immunity and generalization ability. This method provides a feasible and easily implemented way to measure piston error and can simultaneously detect the multiple piston errors of the entire aperture of the segmented telescope.

There are several high-performance adaptive optics systems that deliver diffraction-limited imaging on ground-based telescopes, which renewed the interest of single-mode fiber (SMF) spectroscopy for exoplanet characterization. However, the fundamental mode of a telescope is not well matched to those of conventional SMFs. With the recent progress in asphere manufacturing techniques it may be possible to reshape the fundamental mode of a SMF into any arbitrary distribution. An optimization problem is setup to investigate what the optimal mode field distribution is and what the fundamental throughput limit is for SMF spectroscopy. Both single-object spectrographs and integral-field spectrographs are investigated. The optimal mode for single-object spectrographs is found to be the aperture function of the exit pupil, while for integral-field spectrographs the optimal mode depends on the spatial sampling of the focal plane. For dense sampling, a uniform mode is optimal, while for sparse sampling, the mode of a conventional SMF is near optimal. With the optimal fiber mode, high throughput (>80%) can be achieved when the focal plane is (super) Nyquist sampled. For the Nyquist sampled cases, the optimal mode has almost 20% more throughput than a conventional SMF., 12 pages, 6 figures. Paper written for special double issue of Astrophotonics in JOSA-B and Applied Optics

AR users expect to put on AR Glasses and instantly get an augmented experience. To enable this ease-of-use, AR glasses designers create a large eyebox, using exit pupil expansion or replication. These brute force approaches are inherently inefficient in power consumption and challenged in achieving high image quality. EyeWay's much more efficient approach is to move a small exit pupil aligned with the visual axis of an eye. This requires a low latency accurate eye tracker, low persistency light engine, and also an efficient exit pupil actuator. This approach allows power efficient AR Glasses with large eyebox, high brightness, high contrast, wide color gamut, dynamic focus, large perceived field of view, and retinal resolution image.

High throughput optical system is defined to possess the features of both large field of view (FOV) and high resolution. However, it is full of challenge to design such a telescope with the two conflicting specifications at the same time. In this paper, we propose a method to design a high throughput telescope based on the classical off-axis Three-Mirror Anastigmat (TMA) configuration by introducing a scanning mechanism. We derive the optimum initial design for the TMA system with no primary aberrations through characteristic ray tracing. During the design process, a real exit pupil is necessitated to accommodate the scanning mirror. By gradually increasing the system's FOV during the optimization procedure, we finally obtained a high throughput telescope design with an F-number of 6, a FOV of 60$^{\circ}$*1.5$^{\circ}$, and a long focal length of 876mm. In addition, the tolerance analysis is also conducted to demonstrate the instrumentation feasibility. We believe that this kind of large rectangle FOV telescope with high resolution has broad future applications in the optical remote sensing field., Comment: 12 pages, 9 figures, 7 tables

We propose a waveguide-based near-eye display featuring a dual-channel exit pupil expander, which is composed of an in-coupler, relay gratings, and an out-coupler. Unlike the conventional waveguide-based near-eye displays, whose field of views are usually non-split or partially split, our dual-channel exit pupil expander is able to evenly split the field of view into two halves. The greatest benefit of doing so is that the upper limit of field of view could be significantly increased. The design rules for all components, including the microdisplay, collimating lens, waveguide and gratings, have been studied. The refractive index and dimension of waveguide are identified as two factors that limit the field of view. In what follows, its key specifications are recapitulated. Field of view is 70° (diagonal), eye relief is 15 mm, exit pupil is 20 × 9 mm2, modulation transfer function is above 0.591 at 30 cycle/degree, contrast ratio is 13, and distortion is 1.38%.

Reproduction of the peripheral spherical equivalent refraction (SER) in the eye model is critical for investigations in myopia control. Based on the derivation of a linear relationship between SER and the vergence of the wavefront at exit pupil center, a computing method is proposed to locate the retinal points to reproduce the two-dimensional (2D) distribution of SER. The method is validated by reproducing SER maps measured on both emmetropic and myopic eyes in a realistic eye model based on measurement data. By fitting the retinal points to a general ellipsoid, the limited capability of the general ellipsoid model in reproducing the 2D map of SER is calculated and compared with original data. The high accuracy in SER reproduction and low time-cost of the proposed retinal-locating method can help significantly improve the precision and accuracy of customized wide-angle eye modelling.

There are multiple challenges to realize waveguide-based Surface Relief Gratings (SRG) for combiners in Augmented Reality (AR) applications: fabricability, efficiency and diffraction uniformity are among the most important ones. Interdigital develops SRG using Edge Waves (EW) to design highly efficient gratings with a high angular robustness. An EW is generated by a diffraction phenomenon appearing at the interface between two dielectric media and its direction of propagation is controlled by the index ratio between the two media and the direction of the incident plane wave. Combining different edges together, we optimize the elementary geometry, i.e., the building block of an SRG, to diffract into the direction defined by the grating equation, optimizing the power transfer of the incident light into the direction of interest. Our approach enables symmetrical structures with low aspect-ratio, optimized for coupling very efficiently into the first or second order modes, the latter leads to over-wavelength pitch sizes. Moreover, our SRG is designed to angularly tile the exit pupil of the light engine without losses, making our structures adapted to any sort of light engines. Based on our unique design concept, we present in-couplers using two waveguides with a field of view of 130 degrees and RGB operation, and a one waveguide system with 90 degrees of field of view and RGB operation, both with a wafer having also an index of refraction of about 1.7. We believe this will pave the way to new DOE combiners for future AR glasses.

Diffractive gratings, one of the most promising near-eye display designs, has been challenging to satisfy the essential features without making sacrifices in output efficiency or the direction of incidence due to the low diffraction efficiency of higher modes at normal incidence. Here, we propose dielectric metagratings that support light deflect to a larger angle with high efficiency within the field of view of 54 degrees. In this paper, through the proposed model of the eye-imaging system, we present optimal designs of metagratings for diffractive total internal reflection combiner or diffractive exit pupil expanders.

Aiming at the current testing requirements of optoelectronic products, a long-wave infrared dynamic dual-target simulation system is designed.The optical design of the system adopted a transmissive structure, the dual targets were located on the conjugate focal plane of the optical path, and the dynamic dual targets were realized by a beam combiner.The two-dimensional transportation of the goal was achieved by electric devices.Compared with the static target simulation system, the dual targets could move independently to realize different acceleration and speed curve simulations. In the field of view, the motion curve can be programmed to achieve, and the target position information could be output in real time.The final realization of parallelism was better than 20″, the field of view was 4°, the exit pupil diameter was Φ160mm, the exit pupil distance was 1100mm, the focal length was 800mm, the dynamic target movement speed was 0.02°/s～3°/s, and the acceleration was 0.02°/ s 2～3° /s2 .After a number of product trials, the simulation system meets the current demand for optoelectronic products testing.