This PDF file contains the front matter associated with SPIE Proceedings Volume 12026, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

Bayfol^® HX photopolymer films prove themselves as easy-to-process recording materials for volume holographic optical elements (vHOEs) and are available in customized grade at industrial scale. Their full-color (RGB) recording and replay capabilities are two of their major advantages. Moreover, the adjustable diffraction efficiency, tunable angular and spectral selectivity of vHOEs recorded into Bayfol^® HX as well as their unmatched optical clarity enables superior invisible “off Bragg” optical functionality. As a film product, the replication of vHOEs in Bayfol^® HX can be carried out in a highly cost-efficient and purely photonic roll-to-roll (R2R) process. Utilizing thermoplastic substrates, Bayfol^® HX was demonstrated to be compatible to state-of-the-art plastic processing techniques like thermoforming, film insert molding and casting, which opened using a variety of industry-proven integration technologies for vHOEs. Therefore, Bayfol^® HX makes its way in applications in the field of augmented reality such as Head-up-Displays (HUD) and Headmounted- Displays (HMD), in free-space combiners, in plastic optical waveguides, and in transparent screens. Also, vHOEs made from Bayfol^® HX are utilized in highly sophisticated spectrometers in astronomy as well as in narrow band notch filters for eyeglasses against laser strikes.

Especially in the automotive application field the required reliability performance is very high and demanding. Bayfol® HX film itself and its integration in respective parts were further optimized to show significantly increased resilience against environmental conditions. Those parts pass automotive standard tests like accelerating weathering tests (PV 3930) and thermal cycling test (PV 1200), while keeping the performance level of the vHOEs recorded into Bayfol^® HX film unchanged. This enables a long-term stability of the final product and thus enabling the material to be used in even more applications. This especially holds true for permanent or most frequently outdoor applications such as automotive lighting, HUD or HMD.

We found Holographic materials in a widespread field of applications and particularly in Augmented Reality (AR) area, which has been attracting attention for several years. Scientists have developed various complex holographic optical design for displaying clear and bright images in transparent devices. Holographic materials developed for this technology necessitate stringent optical properties such as photosensitivity, transparency, low cost and robustness. Photopolymer materials offer a reliable solution for these requirements. Our research team has recently presented a unique concept for AR applications that requires evaluating different photopolymers system in order to support our development. Among the photomaterials under test, we have studied in particular a photopolymer formulated in our own laboratory based on du Pont patents that contains N-Phenylmethacrylamide as monomer. This solution is not commercially available and has the advantage of a good transparency and wet chemistry. Another photopolymer under test, based on a different photochemistry mechanism, is the commercial product Bayfol® HX from Covestro available as laminated layers on triacetate cellulose film substrates.

Our AR optical concept requires the use of pixelated holograms with a complex recording process that strongly depends on the inhomogeneous properties response of the photomaterial. In this paper, we describe the both photopolymer materials behavior during this holographic recording step. Then, we discuss about writing strategies implemented to improve the hologram homogeneity. In a second part, we evaluate the robustness of the holograms written in our photomaterial and we mesure their spectral stability under thermal stresses in order to extrapolate their natural aging. A comparison is made with the commercial product, it underlines that the robustness strongly depends on the nature of the polymer chemical formulation.

Holographic reconstruction algorithms based on wave propagation require the object’s Z-plane location. The location is determined manually by selecting an image from a set of reconstructed images over a range of Z-planes. We evaluate five autofocus metrics; the standard deviation of Laplacian and Sobel edge detectors, sum of darkest 2% of pixels, sum of the difference of adjacent reconstructed images (DAMP method), and product of the variance of two orthogonal Gabor filters. The metrics were tested on ten classes of plankton collected from field deployments of a submersible digital holographic imaging system (HOLOCAM). Our results indicate that Gabor filters provide the best focus metric performance, correctly predicting focus distance with +/- 100 um for 78% of the images (n=687). The performance of each metric is significantly dependent on the plankton class, from 46% for the round Coscinodiscus class to 100% for the Thalassionema nitzschoid class using the Gabor focus metric. Focus metric waveform analysis provides a prediction confidence to eliminate images likely to produce erroneous Z predictions. Applying focus metrics to reconstructed image segments substantially containing the object greatly improves the performance of the DAMP method. While Gabor filters are the most computationally intensive focus metric evaluated, the Gabor focus metric curves are relatively smooth and unimodal, enabling iterative search methods to reduce the number of reconstructions required to determine focus.

In this paper, a full-color holographic stereogram (HS) printing system based on effective digital content generation using the inverse-directed propagation (IDP) algorithm is proposed. The digital content is generated effectively within the fast computation based on the IDP algorithm, and an optimized phase-modulation of hogel for red, green, and blue (RGB) channels of computer-generated hologram (CGH). Parallel computing is applied to provide high-resolution hologram data based on the independent hogel property. Finally, the generated hogels are recorded into holographic material sequentially as a volume hologram via fully-automated hogel printing setup using a single spatial-light modulator (SLM) to obtain a full-color HS. Numerical simulation and optical reconstructions demonstrate the simple and effective computation operated in content generation using the proposed IDP-based full-color HS printing system without degrading the image quality of the holograms.

The production of digital holographic images comes from several artistic areas such as photography, film and video, after being mixed, electronically manipulated and digitally synthesized, offering visual effects and additional important resources for the artistic creation of images, which are different from analogue holography¹.

In digital holograms, which more easily reproduce colours and movement², ³, one of the main aesthetic features is the time orchestrated by the viewer, that is, the movement that the viewer develops in front of the holographic plate when looking for the holographic image, since the viewing area is larger than the holographic plate and attracted in some way by the perceptual and expressive possibilities that the interactive concept of the chromaticism of the holographic image gives rise to.

The artistic use of colour in holography is a plastic and symbolic important resource. My intention is to discuss my artistic work and concepts, and to present some resources on the creation of image information, in the context of digital holograms.

The topics developed are focused on visual aspects such as light and colour, third and fourth dimensions, the space-time relationship, and representation issues; in order to explore concepts such as memory and identity, materiality and immateriality; gender issues; thought and action.

Phenanthrenequinone doped poly(methyl methacrylate) (PQ:PMMA) is a well-known write-once read-many (WORM) holographic substrate polymer. Its WORM capacity makes it ideal for applications where stability and longevity are essential, such as in free-space communications and metrology. More specifically, wavelength division multiplexing (WDM) holograms that simultaneously operate at many arbitrary wavelength bands are useful for free space systems where each band may be optimized to deal with different properties of the medium. Holograms written in this substrate typically fall into the Bragg regime, allowing the grating to operate at nearly any optical wavelength, albeit at different angles. Yet, setups designed to write many overlapped gratings, each operating at a distinct wavelength, are often complex and require re-tuning for each target wavelength. WDM is achieved when multiple gratings are stacked: each designed to diffract efficiently at a distinct wavelength with a unique input angle, but a shared output angle. However, when designing holograms to multiplex radically distinct wavelengths (e.g., 780 nm and 1550 nm), one must consider the electrical susceptibility of PQ:PMMA in order to accurately predict the refractive index modulation that will result from a given exposure. In this work, we implement a two-level model of the electrical susceptibility into the WDM design process in order to better predict the refractive index modulation at any given wavelength. This allows the diffraction profiles to be optimized according to the application without requiring retuning of the setup.

An innovative design method to perform both amplitude modulation (AM) and phase modulation (PM) within a single SLM is introduced. Light propagation is controlled in two different directions to perform both AM and PM via liquid crystals alignment layer based on technologies by using photo masks, e-beam technologies, or nano-imprint lithography (NIL), which are discussed and proved to be the implementation to create embossed nanostructures to tune incident light and control the polarization and propagation direction of the light entering the liquid crystals of a single SLM device. This method alleviates the issues in using two separated SLMs trying to achieve the same. Further, the designs are amenable to smaller footprint, lower cost packaging, easier pixel to pixel alignment, and reduced pixel pitches to enhance performance. It will be readily and applicable in holographic display and other LCoS-SLM based for AR-VR glasses application once fabricated in the future.

We developed compact phase-only spatial light modulator (SLM) having 1920 × 1080 pixels with pixel pitch of 4.25 μm on the basis of liquid crystal on silicon (LCOS) technologies. Our SLM can downsize optical systems on various applications because of the compactness of the panel and wide diffraction angle realized by the small pixel pitch. In addition, we realized high photostability by using inorganic alignment layers and light shielding layers for transistors. SLMs for visible light and infrared light are developed assuming display applications and industrial applications, respectively. In this paper, we will introduce our LCOS technologies used in the prototype of phase-only SLM and application researches such as illuminator and laser soldering.

A traditional limitation of holographic displays has been their image quality. Recent advances in computer-generated holography using a camera-in-the-loop (CITL) approach have demonstrated that these issues can be overcome to improve image-fidelity by treating the system as a negative feedback control loop.

Such an approach demands high bit-depth camera sensors to realise high system bandwidth. Here, we explore boosting the dynamic-range of a given imaging sensor by using a spatially varying exposure (SVE) approach. The exposure levels of adjacent pixels are spatially-multiplexed using an appropriate optical mask and the full image reconstructed from the sampled SVE image, resulting in a boosted dynamic-range with only a small sacrifice in resolution.

This technique is well-tailored to CITL requirements as it promises to boost the dynamic range of the imaging sensor in a single image acquisition. We present our findings on the viability of this approach within the context of CGH displays.

Holographic optical elements (HOEs) are versatile alternatives and complements to conventional refractive and reflective optics. With few exceptions, the manufacturing of HOEs based on holographic recording requires monochromatic light with a long coherence length and narrow linewidth, typically provided by lasers operating at a single longitudinal mode. The wavelength of the recording light is a key process parameter as it directly affects the spectral behavior and selectivity of the HOE at replay. Widely tunable continuous-wave optical-parametric-oscillator (OPO) devices are becoming increasingly popular in the field of applied holography, offering unparalleled wavelength coverage in the visible and near infrared spectral range in a single device with coherence and stability properties that match holography’s stringent requirements. The OPO’s wide tuning range translates into equally wide ranges of HOE replay wavelengths with little to no adjustment of the holographic recording geometry. This allows for drastic simplification of recording tools, as well straightforward adjustment of exposure recipes to compensate for any postprocessing shifts.

In this paper, we present newly developed cw OPO systems operating at Watt-level output powers and their use in holographic recordings of uniformly slanted volume holographic gratings (VHGs). The tunability of the OPO system’s output wavelength is a crucial feature enabling the use of highly efficient scanned-beam exposure approaches. We demonstrate this by using a single recording geometry to produce an array of slanted VHGs whose notch spectral band centres were defined by adjusting only the recording wavelength supplied by the OPO systems. Importantly, most of those recording wavelengths did not correspond to commonly available laser wavelengths – they were only achievable thanks to the free tunability of the OPO sources. Captured in state-of-the art photopolymer material, the holographic filters themselves exhibit anomalous reflection-like behavior with high diffraction efficiency (DE) giving optical densities up to OD4, and linear angle-tuning around normal incidence. Collectively this array of filters covers the full visible spectrum. The capability presented here is straightforwardly extended to more complex VHGs like HOEs with optical power, wavelength-multiplexed waveguide-couplers and free-space holographic image combiners.

Speckle noise is often observed when a rough surface is illuminated with coherent light such as a laser beam. Both laser displays and electro-holography systems often use a laser beam as a light source, so it is difficult to avoid the appearance of speckle noise. Speckle noise severely degrades the quality of the displayed image, so reducing speckle noise is an extremely important challenge. Light sources with lower temporal or spatial coherence include supercontinuum light sources and random laser light sources. Although they effectively reduce speckle noise, they are expensive and impractical. Research on reducing the speckle noise that appears at the output end of multimode optical fiber (MMF) through which a coherent laser beam is guided has shown that the noise can be time-averaged by applying mechanical vibration to the MMF. We have devised a speckle noise reduction method for electro-holography, which is an ideal 3D display technology. Speckle noise is reduced by using a voice coil actuator (speaker) to vibrate the MMF through which coherent light is guided. The driving frequency and amplitude of the actuator are electrically controlled. The light from the laser is carried by the MMF and used as the illumination light for the electro-holography. The MMF is coiled around the actuator. Experimental results showed that the speckle contrast tended to decrease as the vibration amplitude increased. This shows that the speckle contrast can be electrically controlled, which demonstrates the usefulness of this method.

Imaging through biological tissues requires fast retrieval of beam scanning. Regarding this purpose, the angular memory effect (AME) is a classical optical effect studied and widely applied. However, the imaging range of AME is confined, which relies on the thickness or scattering mean free path of scattering media. To break the finite imaging boundary, we numerically exploit the phase relation in transmission matrix (TM) of weak scattering media, from which a higher-order phase relation named optical phase association (OPA) extends beyond AME. Furthermore, we found that the OPA could enable uniform light focusing across output channels through weak scattering media in simulation. We believe the optical phase association would improve the imaging approaches such as confocal imaging and speckle autocorrelation.

The waveguide-type full-color 3D-AR display system based on the integral imaging technique using the holographic mirror array is proposed. In the experiment, the AR feature has been successfully verified that the real-world scene and reconstructed virtual full-color 3D image were observed simultaneously.

In this paper, A full-color Denisyuk-type hologram using photopolymer has been recorded by the sequential exposure method. The photopolymer's optical characteristics show that inhibition periods of the photopolymer at three lasers are different in the same beam intensity. To increase the average diffraction efficiency of a full-color holographic optical element (HOE), the three lasers should be sequentially exposed to the photopolymer. The experimental results show that the average efficiency of a full-color reflection HOE is 59.6% and the standard deviation is 2.1. Also, the full-color hologram recorded in a one-layer photopolymer can reconstruct a high-quality image.

We are able to produce holographic installations experimentally as an art practice but as well as an architectural element but it is necessary to have architectural plans and practices to incorporate some of these possibilities in the projects. One of the solutions can be to use digital emergent systems in the generation of architectural form, for example solar daylight determines the distribution and articulation of the components. It gives the possibility to predict and optimize solar orientation, before construction. Each component will interact and responds by having the best performance, contributing to the general form configuration. The placement of holograms specially produced to be placed outside these kind of buildings and incorporated in order to diffract the daylight, through the window to the interior, can reduce the costs of lighting and environmental pollution. Its technical properties can make a valuable contribution to solving energy consumption in public buildings in the City of Aveiro, Portugal, making them more sustainable.