Near-eye display users universally request larger fields of view for enhanced immersion, presence, and device utility. Unlike frame rate or device weight, field of view cannot be represented precisely as a single number. Quoting field of view as a diagonal, a carry-over from the display industry, could refer to either the monocular or stereo field of view and gives no indication of the field of view boundary shape. This work defines an unambiguous metric evaluation of field of view based on solid angle, accounting for eye relief, interpupillary distance, eye rotation, and device alignment. The approach allows optical system designers to identify weak points in the optics/display/rendering pipeline. To accompany modeling, a measurement scheme was developed to metrically compare field of view over various real-world user conditions. Best practices for visualizing and communicating field of view are also presented. This work reviews the methods used to increase field of view, with discussion of the monocular and binocular artifacts that arise in large field of view systems. The limitations and advantages of optical tiling, canting, and extreme distortion are described, using relevant examples in the commercial VR space. The fundamental tradeoffs between resolution, field of view, and optical quality over field are discussed, including a review of methods to maximize field of view without sacrificing on-axis resolution. Until display and optics technology can fully match the human visual system, the intermediate objective is to find the best experience match in field of view, resolution, and optical quality given existing hardware limitations. Qualitative assessments of the relative value of different regions of the human visual field will be provided.

The design challenge of an optical system is not limited to the optical design itself and its performance in nominal conditions; it extends to the realisation of a system which includes tolerancing and manufacturability as well as meeting system requirements such power consumption, heat dissipation, mass, cost constraints and timescales. In this presentation, optical designs for different applications ranging from satellite optical imager to Augmented Reality Displays are presented to illustrate the different challenges that an optical design needs to address. Augmented Reality will prove to be a very useful tool in our everyday lives; it brings elements of the virtual world into the real world, enhancing what we see, hear, and feel. With this comes a high demand for compact, light, affordable and high-quality displays.

Near-eye display performance is usually summarized with a few simple metrics such as field of view, resolution, brightness, size, and weight, which are derived from the display industry. In practice, near-eye displays often suffer from image artifacts not captured in traditional display metrics. This work defines several immersive near-eye metrics such as pupil swim, image contrast, and stray light. We will discuss these metrics through review of a few families of viewing optics and their trade-offs. Fresnel lenses are used in most current virtual reality near-eye displays. These lenses are thin and low weight with acceptable pupil swim performance, but they can create significant stray light artifacts. We will share our measurements of several lenses and demonstrate ways to improve performance. Refractive systems offer the option for lower stray-light viewing but usually at the cost of a much larger size and weight in order to get to the same pupil swim performance. This can be addressed by using a curved image plane but requires new imagers. Polarization-based reflective folded optics is promising and can provide excellent image resolution and pupil swim performance within an attractive form-factor. This approach, however, generally results in relatively low image contrast and severe ghosting. We will discuss some of the main limitations of that technology.

We present an advanced optical design for a high-resolution ultra-compact VR headset for high-end applications based on multichannel freeform optics and 4 OLED WUXGA microdisplays developed under EU project LOMID. Conventional optical systems in VR headsets require large distance between lenses and displays that directly leads to the rather bulky and heavy commercial headsets we have at present. We managed to dramatically decrease the required display size itself and the display to eye distance, making it only 36 mm (to be compared to 60-75 mm in most conventional headsets). This ultra-compact optics allows reducing the headset weight and it occupies about a fourth of volume of a conventional headset with the same FOV. Additionally, our multichannel freeform optics provides an excellent image quality and a large field of view (FOV) leading to highly immersive experience. Unlike conventional microlens arrays, which are also multichannel devices, our design uses freeform optical surfaces to produce, even operating in oblique incidences, the highest optical resolution and Nyquist frequency of the VR pixels where it is needed. The LOMID microdisplays used in our headsets are large-area high-resolution (WUXGA) microdisplays with compact, high bandwidth circuitry, including special measures for high contrast by excellent blacks and low-power consumption. LOMID microdisplay diagonal is 0.98” with 16:10 aspect ratio. With two WUXGA microdisplays per eye, our headset has a total of 4,800x1,920 pixels, close to 5k. As a result, our multichannel freeform optics provides a VR resolution 24 pixels/deg and a monocular FOV of 92x75 degs (or 100x75 with a binocular superposition of 85%). We are currently building LOMID headset prototype with characteristics stated above, which will be presented at the conference.

Femtosecond direct laser writing of micro-optical freeform elements in 3D can be useful for many applications in the realm of digital optics. Due to its high flexibility and short design cycles, it is an ideal candidate for rapid prototyping of novel AR or VR concepts. We present various examples of refractive, diffractive and hybrid optical components which can be fabricated on a variety of substrates including imaging fiber bundles and CMOS image sensors. With typical system diameters of <500 µm, the approach can lead to a plethora of highly compact systems for imaging and illumination, consisting of multiple refractive and/or diffractive freeform surfaces. Alignment free fabrication is possible and can be further extended to create arrays of different freeform imaging lenses, e.g for foveated imaging applications. Due to their small size, wave-optical effects have to be considered in design and simulation. Algorithms like the wave-propagation method (WPM) are ideal candidates to simulate light propagation through complex step-index structures as presented in this paper. Diffractive effects can be used to compensate material dispersion in the photoploymer. Similarly, different materials can be combined to compensate for chromatic aberration. Well defined absorbing structures can be realised by filling 3D printed cavities with black liquids. We present an overview of our latest results and show advances in design, fabrication and optical performance of 3D printed micro-optical systems.

The seamless integration of optical elements such as holograms, waveguides or Fresnel structures into prescription lenses is a key challenge for see-through near-to-eye displays of AR and MR headsets. For a truly immersive experience, many potential users require refractive optics for the perception of the real world around them as well as for the virtual content. A new process has been developed which allows for direct casting of prescription spectacle lenses with embedded optical elements. UV curing of the monomer resin ensures much shorter production times compared to freeform technology. The successful incorporation of polymer films containing volume holograms into a broad range of prescription spectacle lenses will be presented. Thanks to mild process conditions, full functionality of the hologram is maintained. The lenses with integrated volume holograms are further analysed regarding their optical and mechanical properties, such as transmission and film adhesion. Durability of spectacle lenses is only achieved by adequate finishing which includes hard and antireflective coating. Concerning the latter, coating design modifications can be applied in order to meet specific additional requirements of AR displays and to further improve imaging quality of the optical combiners. Finally, a short outlook will cover ongoing work related to the employment of casting technologies for other display applications.

The author will present a low cost technique to produce Monolithic LIght guide component for Near to Eye and Smart Glasses devices. The Monolithic light guide technique made by injection molding process offers a lot of advantage for large scale deployment of Smart Glasses devices in terms of production scalability, cost and safety. The technology is already proved and equip already a Smart Glasses product ORA-2. The Author will detail optical performance and current development for large Field Of View and compact near to eye optical system.

Optical systems for immersive displays incorporate a range of optical components and assemblies that require precision non-contact metrology, including Fizeau interferometry of surface form, new techniques for aspheric microlenses, and interference microscopy for surface structure and texture analysis. Here we consider the problem of evaluating the parallelism and surface form deformation for stacked assemblies of multiple flat glass substrates. Similar structures are common for RGB planar waveguides with slanted sub-wavelength gratings acting as in- and out-couplers. The assembly process for these plates can result in stresses that negatively impact the operation of the planar waveguides and distort the image field. In our experiments, we demonstrate the effectiveness of using coherence scanning interferometry (CSI) over a large aperture area using an LED-based, 100-mm aperture equal-path interferometer having a 4MP camera and software-based dispersion compensation.

Studies on Head Mounted Displays (HMDs) to integrate increased sensory capacities to the wearer are growing fast over the years for applications in Augmented (AR), Virtual (VR) and Mixed Reality (MR). In this work, we focalize our attention on the characterisation of the projected image from the Optical Module (OM) equipped on board of “F4” model (AR mask for industrial users) produced by GlassUp. We have used our own system to test the quality assessment process but it can be applied also to other kinds of OM. The major difference between real eye and the emulated one is that in the first the projected image is elaborated as a continuum by our brain wile in the second the acquiring detector is discretized in pixels. Images acquired by the detector (1936x1216 px) can be analysed with respect to the original images used as input of the display in the OM (640x480 px) as a resize. This allow an innovative approach, the Quality-Threshold-Method (QTM), based on the Structural Similarity (SSIM) theory to extract quantitative information on the quality of projected images. This approach can be used both for hardware validation trial and to evaluate digital corrections for the pincushion and vignetting optical distortions. The quality assessments proposed in this work need a Quality-Threshold-Method (QTM), based on the statistical elements of the SSIM theory, implemented with the brightness of the projection display and the perceived-like resolution with respect to the resolution of the reference images. Functionality test of the entire system for the QTM assessment are presented.

Designer spectacles look great and we want the same for a virtual display. A curved wedge guide will be described that can transfer the virtual image from a projector near the ear round to the pupil of the eye. The eye-box is tiny but the plan is to steer it so as to follow the pupil of the eye and this will be done by shearing the holographic combiner. Ray-tracing predicts a field of view of 115° per eye and a resolution of 2000 pixels per radian at the fovea using pre-distortion in the projector. Guide tolerances are lax, image accommodation is variable and a few milliWatts suffice to steer the pupil.

Studies to integrate increased sensory capacities to the wearer on Head Mounted Displays (HMDs) are growing fast for applications in Augmented (AR), Virtual (VR) and Mixed Reality (MR). This paper focuses on the characterisation of the combiner of the “UNO” AR glasses by GlassUp: a Volume Holographic Optical Element (VHOE), recorded at 532 nm on Bayfol HX, providing high diffraction efficiency over a narrow bandwidth at the desired angles. Furthermore, there is a negligible impact on the HMD frontal lens’s size and on the view of the real world. During the VHOE R&D, we developed a characterisation to serve as development tool, that granted us insight on the patterns inside the polymer, and quality check for the requirements of a pair of UNO glasses. In particular, we designed a setup that provides Total Angular Characterisation through Optical Spectroscopy (TACOS), acquiring the visible spectral response of VHOEs as transmittance, reflectance or dispersion maps at arbitrary angles. Afterwards, it analyses the patterns through a custom fit based on the Kogelnik model. The early stages VHOEs presented undesirable secondary efficiency peaks causing ghosts, impairing both the vision of the real world and the image projected by the OM. TACOS’ custom fit, allowed us to conduct a quantitative analysis on the ghosts. We tied qualitative feedback of the users and quantitative data, identifying the peaks contributing to ghosts. From the spectral maps from TACOS, we can define the parameters for a second VHOE, written together with the first one, aiming to attenuate the ghosts effect and increase the AR immersion. In this work, we present an equilibrium study on all these parameters to find the better condition of projection. Moreover, we studied the impact of both the recording and curing parameters on the appearance of ghosts, e.g. tuning exposure, power ratios.

Real time digital holography provides 3D visual experience close to natural viewing. The high coherence of the required light source is a key to the application of diffractive optics in holographic displays. Switchable diffractive elements are advantageous for several optical functions in immersive holographic displays such as shutters, rapid beam-expansion, polarization filters, and selectable beams. For example, Bragg polarization gratings (B-PG) offer a beneficial set of these properties for application in holographic AR/VR displays. Used with a polarization switch, such gratings can be applied as binary switchable deflection elements as well as switching elements in working as pre-deflection for field lenses. Moreover, they can be applied as deflecting and reflecting polarization filters. The high reachable diffraction angles combined with high DE make this type of gratings attractive for HMD AR/VR applications because of the system inherent short focus lengths and large numerical apertures required by the low space budget in HMDs. The deflection angle can even be doubled by forming a stack of two gratings aligned with opposite orientations. Circular polarization gratings characterized by a high diffraction efficiency (DE > 95%), large diffraction angles (> 30°) and wide angular and wavelength acceptance were made based on photo-crosslinkable liquid crystalline polymers (LCP). In contrast to polarization gratings with larger periods, these gratings exhibit Bragg properties such that one beam is either transmitted or diffracted depending on the direction of circular polarization of the input beam, and the maximal diffraction efficiency is achieved at the proper incident angle only. The fabrication consists of two steps. Initially the holographic exposure of the film at room temperature provides bulk photo-alignment of the LC polymer film caused by the photo-selective cycloaddition of cinnamic ester groups. Finally thermal annealing of the film above Tg enhances the photo-induced optical anisotropy of the film.

DigiLens’s Switchable Bragg Grating (SBG) based waveguides enable switchable, tuneable and digitally reconfigurable color waveguide displays with a field of view and form factor surpassing those of competing technologies. DigiLens waveguides can be laminated to integrate multiple optical functions into a thin transparent device. DigiLens waveguide gratings are printed into a proprietary polymer and liquid crystal mixture which has been optimized to provide any required combination of diffraction efficiency and angular bandwidth in a thin waveguide with high transparency and very low haze. DigiLens waveguides combine two key components: an image generation module, essentially a pico projector, and a holographic waveguide for propagating and expanding the image vertically and horizontally. Color is provided by a stack of monochrome red, green and blue waveguides each with a grating layer capable of addressing the entire field of view, including an input rolled K-vector grating, a fold grating, and an output grating. The output and fold gratings are, typically, passive while the input gratings are switched to eliminated color crosstalk. Rolling the K-vectors of the grating expands the effective angular bandwidth of the waveguide. Fold gratings enable two-dimensional beam expansion in a single waveguide layer, which translates into lower manufacturing cost, reduced haze, and improved image brightness. The design of these complex SBGs is complicated by their birefringent properties, requiring careful attention to polarization when modelling the propagation of light through the waveguide. This takes the design of DigiLens waveguides well beyond the frontiers of established ray-tracing codes. DigiLens has developed proprietary optical tools that run on the ZEMAX platform together with other models for modelling aspects of waveguide SBGs. Our paper summarizes the key features of DigiLens waveguide technology and discusses our optical design methodology for designing and simulating the performance of DigiLens waveguides, giving examples from our motorcycle, and autoHUD products.

Photopolymer films (Bayfol® HX) have been recently introduced into the market place and prove themselves as easy to process for volume holographic optical element (vHOE) recording. The unique properties of vHOEs could significantly simplify the layer structure of immersive displays like in Head-mounted-displays (HMD) and Head-up-displays (HUD). In this paper we investigate and demonstrate spectral multiplexing recording in Bayfol® HX film with a specific focus on the design of the optical recording setup and its system and stability margins. Well controlled RGB recording power conditions enable high repeatability over extended operation periods of the RGB efficiency balance of reflective vHOEs.

The recent new development of Meta Resonant Waveguide-Gratings (RWG) allows adapting the unique optical properties of Resonant Waveguide-Grating away from the specular reflection and direct transmission, in which they were confined in the last 35 years. Exploiting Wood's second type of anomalies, the so-called resonance anomalies in meta-devices based-on horizontal guided-mode resonances (GMR) create excellent transparency out of the resonance condition. Meta RWG can be engineered to exhibit highly selective and tunable optical properties to realize as examples monochromatic diffraction gratings, monochromatic metalenses and meta-couplers, while their nanostructures are made very compact and with flat aspect-ratio. Examples of new optical combiner implementations for augmented and mixed reality will be presented. A roadmap for future developments will be sketched as well as their advantages and limitations, for which they will be compared to surface relief grating, volume holograms and visible-light metasurfaces.

Recently, we proposed a 360-degree viewable holographic display system [1]. Based on this recent work, we are to apply a speckle reduction technique and a spatial filtering method to improve the image quality of 360 degree viewable holographic display system. After capturing the reconstructed holograms of a specially designed pattern, we try to show the functionality of the speckle reduction technique and the spatial filter.

Freeform prism systems are commonly used for head mounted display systems for augmented and virtual reality. They have a wide variety of applications from scientific uses for medical visualization to defense for flight helmet information. The advantage of the freeform prism design over other designs is their ability to have a very large field of view and low f-number while maintaining a small and light weight form factor. This work looks at implementing a freeform gradient-index (GRIN) into the freeform prism design to improve performance, increase field of view (FOV), and/or decrease package size/form factor by the use of 3D printable polymers and glasses. Current designs typically employ a homogeneous material such as polymethyl methacrylate (PMMA). Using a GRIN material gives the designer extra degrees-of-freedom by allowing a variable material refractive index within 8uuthe prism. For example, previous work has shown that a PMMA/Polystyrene plastic GRIN can be used to correct residual lateral color in an eyepiece while maintaining the same weight as homogeneous PMMA. The addition of the GRIN material also allows for light to bend within the material instead of only reflecting off of the surfaces. With the bending and different refractive index of materials, the total internal reflection (TIR) surface requirement of the system can be more easily achieved. This addition of GRIN can improve the packaging constraints of the system and make the system easier to manufacture and increase the FOV which is able to fit in a comparable size. A prism design with freeform GRIN is designed with a FOV of greater than 40°, eye relief of 18.25 mm, eyebox of 8 mm, and performance greater than 10% at 30 lps/mm.

We propose a novel near-eye display, which is capable of: 1. Providing per pixel focus cues within a large depth range, 2. Providing eyebox by using a novel pupil steering HOE, 3. Retaining compact form factor. By simulation, the system can provide FOV of 60 degrees, high resolution (in theory, diffraction limited), high brightness, and 7mm x 7mm of eyebox size, with retaining light and compact form factor. We expect the largest component would be the SLM, except the image combiner, which is essentially a thin film. The proposed system is inspired by some preceding works, especially Maimone’s work on holographic display (2017) and Jang’s work on pupil-tracked light field generation (2017). We overcome drawbacks of both systems by combining the advantages of them. Also, we propose novel PSHOE that can be a breakthrough of current holographic optical element design. We expect the proposed design will suggest a way to elevate the performance of next generation AR display.

Here we present the development and investigation of a holography-based HMD that uses the proprietary Viewing-Window (VW) technology of the company SeeReal Technologies to generate a holographic scene. The VW technology only reconstructs those parts of the wave front that matches the eye pupil. Consequentially a VW is reconstructed. Each object point of the holographic scene is encoded by subholograms in limited areas of the display. The size of the SHs depend on the locations of the object points and the size of the VW. All information outside the SH are not encoded, because they do not reach the VW, and are thus not required. Considering various specification requirements, such as field of view (FOV) and resolution, the development of the HMD system was implemented by means of the optical design software Zemax. A prototypical HMD was set up in the laboratory and several tests were conducted e.g. resolution limit, field of view (FOV), and spatial resolution of the holographic reconstruction to investigate the performance. The HMD system reaches a resolution limit of 2.2 cycles/mm at a distance of 1500 mm between observer and image plane. The magnification of the system was determined to be 7.2x and the FOV is 4.1° in the horizontal and 2.3° in the vertical direction. By tuning the focus of the camera it was demonstrated that the holographic reconstruction is spatially resolved in three dimensions. Taking into account all technical specifications and restrictions, the image quality of the HMD was evaluated with a good result. Using holographic imaging technique has been demonstrated to be suitable to avoid the conflict between accommodation and convergence of the eye and is thus a promising way in future HMD technology.

Deformable beamsplitters have been shown as a means of creating a wide field of view, varifocal, optical see-through, augmented reality display. Current systems suffer from degraded optical quality at far focus and are tethered to large air compressors or pneumatic devices which prevent small, self-contained systems. We present an optimization on the shape of the curved beamsplitter as it deforms to different focal depths and show methods for manufacturing a membrane to achieve those shapes. Our design also demonstrates a step forward in reducing the form factor of the overall system.

Augmented reality systems are becoming very popular nowadays. One of the examples of such system is a monocular see-through smart glass display. Smart glasses look like simple eyeglasses but can way simplify people’s life being. It can quickly find and visualize information, show a map and navigate you in a real time, and do many more different useful things. In such type of a system microdisplay is used as an image generator. We have used amlcd microdisplay with 640x480 resolution, 7.2x5.4 mm display size. The size of the pixel is 11.25x11.25 microns. This provides required angular pixel resolution of maximum 1.5 arcmin and diagonal field of view of minimum 20 degrees. To forward the image from microdisplay to the eye we have used several mirrors. We have considered a monocular see-through smart glass imaging system with the amlcd microdisplay as a source of imposed image. Thus, the main object of the research is to design and analyze an optical architecture for the monocular smart glass display and to provide required characteristics.

One of the main issues of the AR/VR systems is to fit the displayed image to the accommodation and the vergence of the user's eyes. Indeed the quality of a 3D immersion relies on three parameters: -the stereoscopic vision -the impression of depth by the recovering of different objects (the closer objects recover the furthest) or by the angular size of the same object that the user sees. That impression is due to parallax. -and the focus of the eyes. This third point is quite complex to render in AR and VR systems. Indeed, the device needs to acquire the perfect orientation of the user's eyes and their accommodation and then to recalculate the displayed image in real time in function of these data. I found two ways to realize the acquisition of the user's eye's accommodation and orientation: -eye tracking -eye's lens analysis and three ways to render a focused image: -image processing by intelligent blurring -image processing by FFT operations -optical auto-focus embedded on the AR device upstream the image projection. All these solutions will be laid out during the presentation as well as their performances and complexity. Then I'll present my design, the technologies I selected, and why I chose them.

We present a compact,wide-angle,lightweight,optical see-through head-mounted display system integrating freeform elements here.The use of freeform elements can broaden the FOV,which is the critical problem in existing HMD designs that use rotationally symmetric optics.The optimized system can achieve a field of view(FOV)of 40*20 and angular resolution is less than 0.16 arcmin with DMD display channels.With integrated design,portability and reliability of this display design were achieved,which makes mass production possible.

The design proposed in this abstract, for a monocular see through smart glass, i.e. Design Challenge #1, leverages a varifocal lens to accommodate human eyes with different focusing abilities. The eyepiece is made of two separate segments. The first segment, hereby called EP-1, is very similar to a cube beam splitter with two main distinctions; (1) the surface of which light will be exiting has the prescription of an Alvarez lens, and (2) the surface which is parallel to the exiting surface has a concave shape. An LED based projector is used to emit chromatic light into EP-1. The beam splitter guides the projected image towards the freeform Alvarez surface upon which the rays will be moving toward the eye. Intermediate between the eye and the beam splitter, a complimentary Alvarez lens, is placed and is hereby called EP-2. The EP-2 lens combined with the effect of the first freeform surface will provide the focus variability. EP-2 is connected to the third surface of EP-1, a planar surface perpendicular to the surfaces that light travels through, using a thin rectangular flexure. The flexure will provide small motions horizontally for EP-2 relative to EP-1. The other end of EP-2 is attached to a linear actuator which provides the motion for tuning the focus of the system. The concave surface of the eyepiece is prescribed as such to align far-field rays with that of the projector rays reflected off the prism. The combination of EP-1 and EP-2, called EP, will have a total aperture size of 10 mm. EP is fixed to the glass frame in such way that, it will be kept at the lower portion of the user’s field of view.

Regarding the characteristics of limited structure and weight of smart glasses, a large field of view high resolution imaging optical system is invented based on DMD. With zemax software, the optical system is designed with following features: exit pupil diameter 6mm, distance of exit pupil 25mm, field of view 40°X 30°, back focal length >5mm, resolution ratio at 60lp/mm Modulation Transfer Function (MTF) >0.3. The design turns out to fully meet the requirements of design index, and have smaller volume and lighter quality.

We propose a compact optical design for waveguide-based AR exploiting the recently developed polarizing diffractive optical elements. It also enables the depth control of the display content. The exit-pupil expansion can be realized through polarization management instead of gradient efficiency, allowing uniform ambient transmittance. We believe this work will make good impact to the current waveguide-based AR devices.

In recent years, many design forms have been investigated for augmented reality (AR) systems. One of these design forms consists of a waveguide structure that directs light in such a way as to generate a virtual image superimposed on the real environment. Even among the AR systems using the waveguide approach, there are many design forms. Each of these waveguide designs face unique challenges ranging from color non-uniformity to limited field of view. This paper focuses on the design of a gradient index (GRIN) waveguide component for AR systems. A GRIN waveguide utilizes an axial index variation to guide the light in a more direct path towards the eye. By carefully designing the gradient index profile, it is possible to address multiple challenges that waveguide based AR systems face. For example, one of the current AR design forms utilizes multiple waveguides with each waveguide optimized to transmit a specific color to the eye. These multi-waveguide designs are difficult and expensive to manufacture. However, by utilizing the unique chromatic properties of a GRIN material, it is possible to eliminate the need for multiple waveguides and achieve the same color separation using a single GRIN waveguide. Additionally, the chromatic properties of GRIN materials could be used to alleviate some of the color non-uniformity issues exhibited in other waveguide design forms. Other potential benefits from a GRIN waveguide include improved transmission and field of view. Current designs are limited in these areas due to the total internal reflection requirements necessary to contain the light within the waveguide and the number of reflections the light undergoes on its path to the eye. With a GRIN waveguide, the number of reflections is decreased or even eliminated, which could have a positive impact on the transmission and field of view. In this paper we investigate and report on the impact GRIN would have on improving transmission, increasing the field of view, and eliminating the need for multiple waveguides for AR systems.

In recent years, virtual reality technology has become a hot spot in the field of optical design. The head-mounted display is the key device in the virtual reality technology, which undertakes the simulation of visual information. For the convenience of wearing, the head-mounted display must have a smaller size and lighter weight. Head-mounted display based on freeform surfaces prism is favored by many businesses and users due to their compact size and light weight. At present, the head-mounted display’s field of view is small so that it is difficult to bring a strong immersion to the users for it is limited by the freeform surfaces type. We designed a new freeform surfaces prism head-mounted display for z-axis symmetry. The head-mounted display consists of dual light sources and a prism. The dual light sources a1, a2 are symmetrical about the z axis. The prism consists of the freeform surfaces b1, b2, c1, c2, d1, d2. The surfaces b1, c1, d1 of the prism and the surfaces b2, c2, d2 are symmetrical about the z axis. The single prism of the new head-mounted display is equivalent to two normal prisms whose central axes are tilted ± 25 degrees from the z axis respectively. Thus, the field of view of the new prism head-mounted display has twice field of view that the conventional freeform surfaces prism has. The light beams emitted by the dual light sources a1 and a2 are refracted into the prism through the surfaces b1 and b2, respectively. Then the beams are totally reflected on the surfaces d1 and d2 by the internal reflection surfaces c1 and c2. Finally, the light passes through the surfaces c1 and c2 and enter the human pupil. The maximum field of view of the optical system reaches 100 °, which is further greater than the field of view of the current freeform surfaces prism system, and it provides a more realistic experience for the users. Except for merits of the high image quality, compactness and light weight that the ordinary prism head-mounted display has, the freeform surfaces prism also has the advantages of expanding the field of view of the current head-mounted display and it provides a new idea for the future development of the head-mounted display.

Resonant Waveguide Gratings (RWGs) are dielectric structures where the incident waves interfere with the coupled modes to produce narrowband reflection anomalies. Because of the easiness of fabrication and of their unique properties such as the possibility of working with uncoherent white light, they have been industrialized in many fields as optical security, biochemical sensing, solar cells and signal processing, to name a few. Here, we report a novel implementation of these elements as optical combiner for near-eye displays. In particular the engineering of new patterns of RWGs, that we call Meta Resonant Waveguide Gratings (Meta-RWGs), makes possible to create high wavelength and angular selective diffraction structure with excellent transparency, as typically obtained with volume hologram technology. On the other hand, Meta-RWGs go beyond the fabrication limits of volume holograms, since they are compatible with up-scalable fabrication processes such as roll-to-roll nanoimprint lithography or hot-embossing replication at high speeds on thin supportive films. Meta-RWGs can therefore be used to make optical combiners which can be integrated on standard prescription glasses with curved lenses. Because of the high wavelength and angular selectivity, optical combiners based on Meta-RWGs have high transparency and are, therefore, better see-through devices compared to surface relief gratings or metasurfaces-based combiners. We will show that these structures can be designed for large steering angles, allowing large field of view and are compatible with holographic displays or light-field displays.

The Vergence Accomodation Conflict (VAC) is a major visual discomfort that happens when one looks too long at a virtually displayed scene. Our brain is used to the real world where the accommodation distance and vergence distance are always the same. However, in virtual reality, the 3D effect is created by varying vergence, and demands to dissociate accommodation and vergence. This may cause headaches or even nausea after a long time exposure. Yet, virtual reality displays could be very helpful in a large set of applications such as surgery, unless the surgeon cannot operate longer than a dozen of minutes a day There are two approaches to solve the VAC: static or dynamic systems. We propose a dynamic VAC free virtual reality display that is light and small enough to be worn with the largest field of view, best angular resolution and quality possible. Our approach is to mimic what an eye does. The idea is to follow user’s sight through the image in order to recreate as close from reality as possible the behavior of our stereoscopic vision. An eye tracker is used to know the part of the scene that is observed. Using a varifocal system, we conjugate the image at the vergence distance and blur out of focus objects to put the user into realistic conditions. Recent technological advances allow the use of varifocal methods that were impossible to do because of response time of several components just a few years ago. The main idea is not new (virtual reality displays were invented in the 1960’s, the VAC was theoretically solved in the 1990’s, the basis of our work was proven efficient in the 2010’s), our proposition groups several technical solutions and focus on how to miniaturize the system in order to make it wearable. Hopefully, soon enough, surgeons will finally be able to operate far away from the hospital thanks to a virtual reality head-set without any nauseous effects…

In this submission, we will demonstrate the design of an augmented reality (AR) system with an ultra-thin light guide as the optical combiner. It will have a glasses-like form factor and mainly consists two parts: the image collimating system and the light guide. The collimating system is a monolithic freeform prism consisting of multiple freeform surfaces. On one hand, it produces front illumination for a reflective liquid-crystal-on-silicon (LCoS) microdisplay. On the other hand, it is used to collimate the image from the microdisplay to infinity, which ensures that the light from the microdisplay is efficiently coupled into the light guide with parallel incidence. The light guide will contain a wedge shape in-coupling part to let the rays TIR and propagate within the substrate. On the out-coupling region, there are an array of microstructure mirrors that is arranged periodically with small flat transparent surfaces in between each tapered micro-mirrors. The collimated image is coupled into the eye pupil by micro-mirrors, whereas outdoor scene can be seen through the flat surfaces within the eyebox, so that the virtual image and the see-through scene can be combined with this half-reflection-half-transmission out-coupling structure. Our innovation was to improve the image quality and uniformity over a wide field of view and eyebox with more compact freeform design, while keeping the image brightness and see-through efficiency. The microdisplay will be an LCoS with LED backlight with the diagonal size of 0.4 inch and resolution of 1280 by 960. The system field of view can be about ±15 degree, with exit pupil diameter at least 4mm, which yields an angular resolution of about 1.4 arc minutes per pixel. The thickness of the light guide can be within 3mm. With only one freeform prism and one waveguide piece, the overall system can be light weighted and super compact, and have a glasses-alike appearance with high quality image performance.

We proposed a 2D/3D switchable display design based on polarization-dependent metasurfaces. Metasurfaces are ultrathin planar optical devices patterned with subwavelength nanostructures. We design the metasurfaces such that they can simultaneously deflect right-hand circularly polarized (RCP) light to an angle and transmit left-hand circularly polarized (LCP) light to the normal direction. Combined with an active polarization rotator, the device can be switched between high resolution 2D display mode and multiview 3D display mode. Proof-of-principle metasurface designs are demonstrated. The far field radiation patterns in the 2D and 3D mode are simulated and analyzed. The effects of spectral bandwidth and beam directionality are also discussed. Compared with liquid crystal lenses, which is the key element in previous 2D/3D switchable displays, metasurfaces 1) deliver more precise phase profile control, thus less aberrations and higher image quality; 2) offer additional degrees of freedom in polarization manipulation; and 3) can be adapted to much smaller sizes.

One of the solutions to the augmented reality (AR) problem is the freeform prism. The freeform prism design is robust during use because it features fewer independently-moving elements. However, this also means fewer surfaces are available to improve optical performance. Thus, for AR design in general (and freeform prisms specifically), designers need every tool available to achieve high field of view, low f/number, small package, and high performing systems. For a freeform prism, one key choice is the mathematical basis describing the freeform surface. Descriptions range from XY polynomials to the broadly-used Zernike polynomials to application-specific characterizations such as the freeform Q-polynomials introduced by Greg Forbes. In this work, we explore and compare designs with different mathematical surfaces descriptions. Just as important is how that basis is used. Because of increased complexity of both freeform surface descriptions and of freeform aberration theory, designers may lean more heavily on the optical design software to improve nominal performance. This can lead to systems which are over-designed and very sensitive to small changes in parameters. Often, it is hard to undo such decisions; even the best tolerancing analysis cannot improve a system which is over-designed, overly sensitive, or poorly understood. Therefore, this work focuses on design for analysis, manufacture, and assembly. In particular, we design a freeform prism with a diagonal FOV of greater than 40°, eye relief of 18.25 mm, eyebox of 8 mm, and performance greater than 10% at 30 lps/mm. We use multiple surfaces representations, and examine how different representations affect the system, including optical performance, analysis of aberrations, and a statistical analysis of tolerancing and sensitivity. Freeform aberration theory, including Nodal Aberration Theory, is used to understand the performance of the system. We also extend freeform aberration analysis to chromatic aberrations. We analyze tolerancing, manufacturability, and sensitivity.

The emergence of new Virtual Reality (VR) and Augmented Reality (AR) technologies has changed the gaming and entertainment industry but also have shown great potential in engineering and medical applications. This has increased the importance to improve the immersive experience in the most natural way possible. Some of the hurdles like Vergence-Accommodation Conflict (VAC) and limited Field of View (FOV) need to be addressed. The aim of our work is to adapt the optics of a head mounted display (HMD) in order to achieve an improved perceptional experience. Furthermore, we want to simulate and present the 3D environment in the most comprehensible way.

During the history of display fields, there have been a desire to implement ideal three-dimensional (3D) displays. The ideal 3D displays may provide full of physiological cues including binocular disparity, motion parallax, and focus cues. Although several technologies have been studied to realize the ideal 3D displays, it is still challenging to satisfy commercial demands in resolution, depth of field, form factor, eye-box, field of view, and frame rate. Here, we propose tomographic near-eye displays that may have extremely large depth of field (8.5 cm – infinity) without loss of frame rate or resolution, and enough eye-box (10 mm) with moderate field of view (30°). According to the optical design of the SMB, tomographic near-eye display may support up to 100 planes within the addressable depth of field. Tomographic near-eye displays consist of a tunable lens, a display panel (e.g. liquid crystal panel), and a SMB. The tunable lens is operated by triangle wave at 60 Hz so that it sweeps the focal range within single frame. Within the single frame, the backlight is spatially modulated about 16-100 times while the display panel shows static 2D images. The SMB independently illuminates pixels of the display panel so that each pixel is floated on the desired depth. In summary, we introduce a novel 3D display technology called tomographic near-eye displays that present superior performance in resolution, depth of field, and focus cue reproduction. This approach has a lot of potential to be applied for various field in 3D displays including head-up displays, tabletop displays, as well as head-mounted displays. It could be efficient solution for vergence-accommodation conflict as providing accurate focus cues.

We proposed a 2D/3D switchable display design based on polarization-dependent metasurfaces. Metasurfaces are ultrathin planar optical devices patterned with subwavelength nanostructures. We design the metasurfaces such that they can simultaneously deflect right-hand circularly polarized (RCP) light to an angle and transmit left-hand circularly polarized (LCP) light to the normal direction. Combined with an active polarization rotator, the device can be switched between high resolution 2D display mode and multiview 3D display mode. Proof-of-principle metasurface designs are demonstrated. The far field radiation patterns in the 2D and 3D mode are simulated and analyzed. The effects of spectral bandwidth and beam directionality are also discussed. Compared with liquid crystal lenses, which is the key element in previous 2D/3D switchable displays, metasurfaces 1) deliver more precise phase profile control, thus less aberrations and higher image quality; 2) offer additional degrees of freedom in polarization manipulation; and 3) can be adapted to much smaller sizes.

This study proposes an optical-see-through light-field near-eye display (OST LF-NED) based on integral imaging (InI) using a discrete lenslet array (DLA). A real-time rendered light-field image based on OpenGL is used as the image source. A special microdisplay array built on a transparent substrate is used as the screen. A DLA is used as a spatial light modulator (SLM) to generate dense light field of the 3-D scene inside the eyebox of the system and provide correct focus cues to the user. The key to realize the OST capacity is that the microdisplays and the lenslets are both discretely-arranged so that the light from the real world passes directly through the gaps among the microdisplays on the transparent substrate and then the flat portion on the DLA panel, providing a clear view of the real world as well as the virtual information. Analysis and numerical simulation of the stray light are conducted in detail. The stray light can be totally eliminated in the region of the eyebox, regardless of the limitation of the lenslets' F-number. In practical situations, take the limitation of the F-number into consideration, a trade-off between the size of eyebox and the stray light is made. A ring-shaped aperture on each lenslet is added to further relief the stray light by blocking the screen light that passes by the outer edge of each lenslet. A static film-based prototype and a dynamic OLED-based prototype are implemented in the experiments. The experimental results show that the proposed method is capable of obtaining a corrected perception of depth of the virtual information and an OST view in augmented reality (AR) applications.

Head mounted displays (HMD) showed huge market potential in recent years. In these techniques, vergence-acommodation conflict is a fundamental problem which makes viewers feel discomfort and fatigue. To overcome this limitation, researchers proposed many solutions including multi-focal-plane (MFP) displays and light-field (LF) displays. In the MFP displays, the input image is projected onto four or more depth planes, while the LF displays present a four-dimensional (4D) light field to the viewer’s retina. These techniques are able to correct or nearly correct focus cues, however, they failed to achieve both high image fresh rate and high lateral resolution with a compact architecture. In this paper, we propose a compact HMD with correct focus cues by spatially projecting the input images onto four depth planes. In the proposed system, two stacked transparent liquid crystal displays (LCD) provide two axially separated input images in an additive fashion. We set a liquid crystal panel behind the LCDs to modulate the polarization of the emitting light from the LCDs in pixel level. Based on a known depth map, the liquid crystal panel segment each input image into two regions labelled by two orthogonal polarization states, respectively. After that, a birefringent lens further projects each input image onto two different depth planes based on polarization state of the incident light. In this design, we get four images on different depth planes at 0D, 1D, 2D, and 3D. Comparing to the existing techniques, the proposed HMD corrects focus cues with a compact architecture. Moreover, because there is no temporal multiplexing and lateral resolution sacrifice, the HMD can easily achieve high image refresh rate and high lateral resolution. Herein, we will present the optical design of the HMD and characterize its performance in Zemax.

We propose a retinal-projection-based near-eye display (NED)――also dubbed as retinal projection display (RPD)――for virtual reality (VR). Our design is highlighted by an array of tiled organic light-emitting diodes (OLEDs) and a transmissive spatial light modulator (SLM). Its design rules are to be set forth in depth, followed by the results and discussion regarding the field of view, angular pixel resolution, eye box and relief, brightness, full color operation, modulation transfer function, contrast ratio, distortion, simulated imaging, and industrial design. The working principle of our design is briefly explained as follows. OLEDs in tandem with a SLM constitute an array of miniature projectors that deliver the virtual image directly to the retina. Since the size of an individual OLED is way smaller than that of SLM, each OLED can be regarded as a point light source. The function of SLM is to modulate the intensity of light emitted from the OLEDs. For achieving a high brightness, it is desirable to be highly transparent. As a viable option, a backlight-free, monochrome liquid crystal display can be used for this purpose. In order for the real image of SLM not to be directly perceived by the eye, it is required that SLM be placed out of the range of accommodation. By doing so, eye will trace back along the extended virtual rays to see a magnified virtual image formed at a target distance. For full color operation, a sequential color scheme is adopted, with which each primary color of OLEDs is activated in sequence. As opposed to the conventional NEDs for VR, our RPD exhibits several unique features. First, instead of using an eyepiece or ocular lens, RPD relies on the eye itself in imaging the virtual objects. Second, lighter weight is expected as no bulky lenses are needed for RPD. Third, the distance and size of virtual objects hinge on the status of eye, including its diopter and pupil. Fourth, its ultra-large FOV could be a trump card in pursuing the throne of NEDs.

See through augmented reality head mounted display(STHMD) has been regarded as the next-generation display technology with potential applications in navigation, education, and entertainments. Field of view(FOV) and the light-weight are the two key factors for a STHMD which determine the user’s experience and production cost. Freeform optics can be a good choice due to its advantages in multiple degree of freedom in designs, high-quality imaging performance, compact size and low production cost. However, it is extremely difficult to control the boundary condition of the freeform surfaces, especially for optical engineer without much experiences. In this work, we investigate several common boundary problems incorporated with several scientific merits functions for evaluations and propose an adaptive weight method for controlling the imaging quality by using customized OpticsStudio API (ZOS-API) in ZEMAX. To verify the proposed method, we designed a STHMD with single freeform surface. The FOV is large than 40 degrees, with an exit pupil diameter of 8mm, and the modulation transfer function values across the entire field of the STHMD are above 0.2 at 9-line pairs/mm (lp/mm). This work provide an effective method for optical designers.

With the emergence of Augmented Reality (AR) and Virtual Reality (VR) headset during the past decade, firms and academic laboratory worked on the design of optical combiners to increase the performances and form factor of the optical combiners. Most of the smart glasses on the market have the asset of having a small form factor that will ease the integration of the combiner in a head worn device. Most of them (Google glass, Vusix) use prism-like architecture, where the collimation and deflection of the light is performed by one single optical piece. This approch reduce the size and tolerence issues of the device. Other companies (Optinvent, Microsoft, Lumus) came with waveguide architecture, in which the light is collimated by a lens or group of lens, injected in a slab waveguide and extracted in front of the eye of the user. This way, the image is brought right in front of the eye, where prism like architecture display an image in the peripherical sight of the user. These optical combiners however suffer from low tolerences and fabrication complexity as several pieces are combined. The injection and extraction of image rays in the waveguide can be performed either by holograms or slanted mirrors. Each technology has its downturns but for now no satisfying results were obtained with holographic option, bringing chromatic dispersion resulting in degradation of MTF. This work is a proposition of waveguide-type optical design for AR smart glasses. This investigation deals with pupil folding mechanism to try to optimize the optical device form factor. In the meantime, leads on the design of a monolithic waveguide optical combiners are developped. To push the performances of the waveguide-like architecture and take it one step further, the problem is considered in the 3 dimensions to try to take the the pupil folding mechanism one step further.

This design concept is using multi-core imaging fiber bundles with small diameters (<500 µm) to transfer information from an image source (e.g. laser pico projector) to the eye of the user. One of the main benefits of this approach is that the resulting glasses are almost indistinguishable from conventional eyewear. Not only are the fiber bundles very thin and positioned close to the eye but their difference in refractive index compared to the surrounding medium is very small which makes them basically invisible. At the same time, they can carry a significant space bandwidth product and are easier to fabricate in comparison to similar solutions using waveguides or Fresnel-type extractors. Using raytracing and wave-optical considerations, we show that such an approach can lead to highly inconspicuous AR glasses with a >20° diagonal field of view and a high angular pixel resolution.

The contradiction between large field of view, big exit pupil and large eye relief in immersive VR head-mounted displays limits the probability that such bulky device would be accepted by the most consumers. A wide field of view coaxial catadioptirc system is propsed to serve as the magnified optics in this paper, which consists of a wire grid polarizer, a quarter wavelength plate and a plano-convex lens, making the optics thinner and fabrication easier. Note that on the surface of wire grid polarizer towards the image source is a partically reflecting surface and the spherical surface of the plano-convex lens is semi-reflecting. The plano-convex lens takes the role of imaging, while the wire grid polarizer and the quarter wavelength plate work together to adjust the polarization orientation so as to suppress direct transmission. To shrink RMS spot diameter and improve the off-axis aberrations, one or more surfaces could be replaced by aspherics. The resulting monocular optical system yields the field of view as large as 110°, with virtual image exhibited 5 meters away from the observer. Exit pupil diameter and eye relief of the designed system are 10 mm and 15 mm, respectively. The MTF is higher than 0.2 at 8 lp/mm. Considerable distortion will appear inevitably when field of view approaches 100°, which could be tackled via electronic correction. With evaluation in the CodeV, weight of the whole optics is about 38 grams and the distance from the element near the observer to the image source is as thin as 25 mm, showing the suggested design is superior to the ones in the form of singlet, doublet, aspherics or Fresnel lens, in terms of the weight and volume. With this monocular optical system, an HMD binocular optical system is achieved in the form of partially overlapping field of view.

We present an advanced optical design for a high-resolution ultra-compact Virtual Reality headset based on the traditional pancake configuration following optical foveation in the sense: Firstly, the magnification is variable along the FoV i.e. the VR pixel density is maximum at the center and gradually becomes smaller towards the edge. Secondly, the optics image quality is also adapted, and the combination of both is designed to fit with the human visual acuity with normal eye movements, so the user does not perceive the lower peripheral resolution. VR pixel resolution (i.e. pixels per degree) of traditional pancake optics is limited to the geometrical distance of the different elements present. However, we have broken that compromise by applying Limbak’s ThinEyes® super-resolution technology to the design of four aspherical surfaces in a pancake-type configuration, so that the VR pixel resolution is dramatically increased at the center while maintaining high FoV and excellent imaging quality. We make use of a curved reflective polarizer, which could be done by vacuum molding a polymeric one made out of birefringent multilayer technology (as DBEF of 3M). As an example, we present an optical system that uses a standard 3.28“square display, with a pixel pitch of 27.3 microns (2,160x2,160). The total track length (eye pupil to display distance) of the system is 36mm with 15 mm eye relief, so the lens thickness is only 21 mm. Thanks to the optical foveation, this design achieves a focal length of 49.5 mm at the center of the FoV, resulting in an outstanding VR resolution of 30.5 pixels per degree at the center with a circular FoV of 100 deg for a 10mm eyebox. As a comparison, for the same FoV, a conventional pancake lens design (with a linear rho-theta distortion function) would achieve a VR resolution of 21.6 ppd, which is 1.41x lower.

Two possible systems of optical architecture to mitigate the Vergence-Accomodation conflict and low-vision are proposed in this work. The first system using a single magnifier lens allows a magnification of the image projected on the display. This option is possible because the function of a converging lens is magnifying a near object. Using a converging lens, the image in the retina is bigger in angular extension than if the object is visualizing with the naked eye. Also, the use of the converging lens allows that the eye is relaxed, this is, the accommodation of the eye is like the object were at infinite, so, the eye is in a comfortable position. A second system being studied is a Galilean telescope. The Galilean telescope is not a simple lens; it is a composite lens or a system of lenses, in which the field of view is determined by the diameter of the objective lens and the position of the eye with respect to the ocular.

The quality of coupling optical design in waveguide based augmented reality display is vital to the final imaging performance. In this work, we provide a waveguide optics design tool package (AR kit in ZOS) to model waveguide based augmented reality optical system. In the demo design presented, the input/exit coupler window is 5.4X2mm in size, the field of view is 24X15°and 57° in diagonal. The optical transfer efficient is 37% and the total dimensional size is 45*20*2mm. For user-friendly interface for designers, our AR kit in ZOS allows self-defined or file data input for the in/exit coupling beam profile. The dispersion element allows angle-dependent coating or etched grating, to avoid cross-talk and maintain intensity uniform between different wavelengths, the transmission or diffraction efficiency of each layer is computed within our tools. Users can define system size (width, length, thickness), the number of layers and size of exit coupler window in flexible. Furthermore, our tools can also optimize the whole waveguide system in terms of low stray light by recording all ray data and adjust the configuration data by using inherent Zemax Optimization operands for the better beam quality at the detector.

A smart glass augmented reality (AR) display system is designed with a streamlined form factor featuring an off-axis mirror design. The main component of the combiner optics is in the shape of a regular pair of eye glasses or sun glasses, with no diffractive gratings, waveguides (lightguides), prisms or Fresnel surfaces involved. Perfect see-through performance is achieved with a low-cost combiner that consist of only highly manufacturable reflective surfaces. The optical performance of the projected display can be enhanced by using a freeform gradient index element. The 20-degree full field of view of the AR display is centered at about 35 degrees with respect to the center of the ocular vision. Such a design allows the user to have a clear unobscured central field of view. At the same time, the projected image is accessible by moving the eyeball off the central vision. The system is designed with a circular eye box with more than 10 mm in diameter.

Nowadays, the main directions of development of augmented reality (AR) glasses are: increasing of field of view (FOV) and eye-motion box; reducing weight of AR glasses; solving accommodation-convergence conflict; opportunity of individual ophthalmological vision correction. All these requirements should be combined with high image quality and decreasing dimensions of AR Glasses. We report the optical system of AR glasses, based on Schmidt Camera scheme and using Super Multi View (SMV) technique for focusing in different depths. Calculated and modeled scheme has huge benefits: eye motion box about 10 mm and field of view 60°. Also, reported scheme is compact, lightweight, doesn't cause accommodation-convegrence conflict, has low aberrations and variable focus.

The presented device is a patented HMD with a custom stereo camera mounted on the front side. With a field of view of 110° for both augmented and virtual realities, we perform live software undistortions using different methods for the HMD and cameras lenses for real-time rendering and the lowest “photon-to-pixel” time. The reality and the virtual space are well aligned. The device is also fully autonomous and can track its translation and rotation in world space thanks to Simultaneous Location and Mapping with the cameras, with an option to perform dense 3D reconstruction.

Multi-order diffractive optical elements (DOEs) spatially modulate the optical path length by multiples of the light wavelength. This additional degree of freedom significantly extends their possibilities. Earlier we have demonstrated tunable diffractive lenses (so called Moiré lenses) which consist of a stack of two successive DOEs. In combination they form a lens with an optical power which can be adjusted by a relative rotation between its two components. Using multi-order diffractive optics, these originally dispersive lenses can be designed to become achromatic, apochromatic or even "multi-chromatic". In the field of digital diffractive optics some newer (phase-only) liquid crystal spatial light modulators allow for optical path lengths shifts of multiples of the optical wavelength, thus providing the possibility of displaying digital multi-order DOEs. We demonstrate that this allows one to project color holograms with (at least theoretically) unlimited diffraction efficiency, to display color images without needing any color filters, and to simultaneously display independent images at different viewing angles.

Factored light-field (LF) technology helps resolving the vergence-accommodation conflict inherent to the most of conventional stereoscopic displays. The remaining challenges include decreasing computation cost of light-field factorization and improvement of image quality. We implement and compare three different methods of LF factorization and two ways of initializing them. We consider the possibility to use these methods in a head-mounted display where a mobile device, such as a smartphone might act as a display. We prototyped a dual-layer light-field stereoscope similar to that reported in [Huang et al. SIGGRAPH 2015], but with a resolution twice as high. We measure the speed of LF factorization and display and the quality of the resulting image. We found that the best method for LF factorization in terms of speed and quality is the Weighted Rank-one Residual Iterations (WRRI). Our tests revealed that the best way of initialization in WRRI is that by the square root of the LF central view values – namely, two iterations are enough to achieve acceptable image quality. We have used real images taken with a Lytro Illum plenoptic camera. Reproduction of a small real-world video in real time is demonstrated. We derive formulas for mapping LF values to the target and weight matrices in the case when the display and modulator have different resolutions and pixel sizes. In this case, annoying aliasing effects inevitably arise. Therefore, we suggest anti-aliasing algorithms that improve the quality of the resulting images. Currently, we are working on extending our prototype with the possibility to have a mobile phone as a display.

Conventional holographic displays require ultra-high resolution spatial light modulators (SLMs) with a pixel pitch smaller than one micron. The viewing-zone scanning holographic display using MEMS SLMs does not require such a small pixel pitch and an ultra-high resolution because the viewing zone is expanded by a scanning mechanism not by light diffraction using small pixel pitches. Recently, the two-channel viewing-zone scanning system [Opt. Express, vol. 24, 18772 (2016)] was developed, which has a screen size of 7.4 in. and a viewing zone angle of 43.0°. In this study, the image sharpness of three-dimensional (3D) images generated by the viewing-zone scanning system is discussed. We assume that 3D images consist of an aggregate of object points. The object points are produced by spherical waves emitted from the display screen and the beam waist of the spherical waves gives the image sharpness. When the pixel pitch on the display screen is denoted by 𝑝, the beam waist is given by 0.61 𝑝. It means that the pixel pitch solely determines the image sharpness of 3D images. For the viewing-zone scanning system, the pixel pitch is increased to reduce the viewing zone and the reduced viewing zone is scanned to enlarge the viewing zone. The width of the reduced viewing zone is 𝑣 = 𝜆𝑙 / 𝑝, where 𝑙 represents the distance between the display screen and the reduced viewing zone and 𝜆 represents the wavelength of light. The width of the reduced viewing zone should be larger than the pupil diameter of eyes to practically realize the wavefront reconstruction. Consequently, the image sharpness is given by 𝑤 = 0.61 𝜆𝑙 / 𝑣. The scanning parameter 𝑙 / 𝑣 determines the sharpness of 3D images. The experimental evaluation of the sharpness of the 3D images generated by the viewing-zone systems will be shown.

We discuss theoretical principles of image formation using a non-conventional near-eye display approach. A display positioned at a short distance from the eye can’t be seen with good resolution as the eye is not able to accommodate. To allow eye accommodation, a display based on multiple-interference effect has been proposed. This effect allows image formation without lens and is described here as the intraocular self-focusing effect. We propose a theoretical and experimental analysis to evaluate the potential of this technology. We have demonstrated self-focusing capability on the retina without any optical system from an emissive surface located at a distance closer from the eye than near point of clear view. The diffraction pattern resulting from the self-focusing effect is composed of a signal peak surrounded with noise. From an infinite number of emissive apertures, a planar wave front could be reconstructed from an infinite number of spherical wave fronts, as described by the Huygens Fresnel principle. We use a so-called double-Gaussian approximation to approximate signal peak with the first Gaussian curve, and surrounding halo with the second one. We have studied the ratio between the energy in the peak and in the noise halo as a function of the aperture distribution. The non-conventional projection image consists of elementary focalized spots. To produce one elementary focalized spot we use a single light beam passing through our aperture distribution. Image formation is demonstrated by a complex light wavefront passing through this distribution. A compromise on the number of emissive apertures is necessary to form a sharp image. Our experiment allows us to evaluate the resolution-acutance and sharpness compromise in our display concept. We also analyzed the capability of image formation depending on source coherence (spatial and temporal coherence). Promising first experimental results using alphanumeric character image formation will be presented.

We present a modified tunable Alvarez lens which uses a 4f-setup to image two diffractive sub-lenses onto each other, in contrast to the classic Alvarez lens utilizing a translational motion of the two sub-lenses with respect to each other. Insertion of a galvo-mirror makes the approach suitable for very fast actuation: Focus tuning is achieved by rotating a galvo-mirror which affects the overlap of the light from the two sub-lenses which together form an effective lens of refractive power that depends on the rotation angle. We have demonstrated the approach experimentally, implementing it with an LCOS-SLM. We consider our “stationary” Alvarez setup especially suitable for applications where fast refocusing rates are important, as for example in 3D life cell monitoring or tracking.

We review the various display engine technologies and subsequent optical architectures used today in AR and see-through MR headsets to enable the best possible three-dimensional immersion experience for the user. Special consideration will be given to the degree of adequacy of the display architecture to the human perceptive system in order to increase visual comfort for prolonged usage. Wearable comfort issues are also addressed as key issues for broad acceptance, and range from size, weight, center of gravity to thermals, fabrics and more.