Conventional digital holography uses the technique of combining two coherent light fields and the numerical reconstruction of the recorded hologram leads to the object amplitude and phase information. In spite of significant developments on the DH with coherent light, complex field imaging with arbitrary coherent source is also desired for various reasons. Here, we present a possible experimental approach for holography with the incoherent light. In case of incoherent light, the complex spatial coherence function is the measurable quantity and the incoherent object holograms are recorded as the coherence function. Thus, to record complex spatial coherence a square Sagnac radial shearing interferometer is designed with the phase-shifting approach. The five phase-shifting method helps to measure the fringe visibility and the corresponding phase, which jointly represents the complex coherence function. The back propagation of complex coherence function helps to retrieve the object information.

Polarization has a profound impact on image quality, visual perception and completer wave front imaging. For instance, polarization provides a new perspective on seeing an object which is otherwise obscured, low contrast or not measurable by conventional imaging methods. In this paper, we discuss a possible extension of the digital holography (DH) to the polarization domain, and the technique is referred to as digital polarization holography (DPH). Basic principle of DPH is described and some of our recent contributions on quantitative polarization imaging are covered. . We also discuss and highlight potential of combining speckle field illumination with DPH for high-resolution polarization imaging.

Management of medical fear and pain is a complex mission in children. Holographic technology provides an innovative distraction approach. To our knowledge, holograms have not been used in hospitals before.

The aim was to deliver holographic characters as a new digital pain and stress reducing tool in medicine.

Methods

The study was performed at Tartu University Children's Hospital during 2020-2021. 62 children aged 10 months to 11 years (5.31 yrs; SD=2.63) underwent painful procedures: intravenous cannulations, blood tests. The hospital pain was examined via parents’ questionnaires and children's pain scores by FLACC/VAS before and after viewing holograms, assessed by nurses. 33 playful holographic characters with HYPERVSN 3D devices were presented with music. Holograms were shown for 3-10 minutes depending on the procedure.

Results

We found that the use of holographic techniques (HT) was effective: before viewing holograms 7% of children had severe, 64% moderate, 22% mild and 7% no distress. After viewing holograms, positive effect was reported: 50% of children were stress-free, 43% had mild, 7% moderate and no children with severe discomfort. Increased cooperation in Botox and blood pressure procedures. HT was effective in all age groups, including babies; parents reported calming effects of holograms on themselves, confirming the suitability of HT for adults.

Conclusions

Holograms are the new tools to prepare and guide patients during painful procedures. Holograms also improved children's’ emotional state and pain control. We encourage technicians to create and develop new 3D solutions based on HT to improve healthcare services.

Optical imaging has been well-known in nature and in technology for decades. Recently, new methods of optical imaging assisted by techniques of computational imaging have been proposed and demonstrated. In the presentation, we describe several new techniques of three-dimensional optical imaging, from Fresnel Incoherent Correlation Holography (FINCH) to interferenceless Coded Aperture Correlation Holography (COACH). These systems have different imaging performances than conventional techniques. FINCH and COACH are methods for recording digital holograms of a three-dimensional scene. However, COACH can be used for several other incoherent and coherent optical applications. In this talk, we survey the prime landmarks on the topics of FINCH and COACH from two major perspectives: architectures and applications of the various systems. We explore the main configurations of hologram recorders in FINCH and COACH systems. For each design, we describe some of the recent implementations of these recorders in optical imaging. Possible applications for these imaging methods, ranging from a new generation of fluorescent microscopes to methods of noninvasive imaging through a scattering medium, will be discussed

Imaging based problem solving approaches have shown an illustrative way of solving problems for various scientific applications, for several decades. With an increased demand for automation, such approaches have shown exponential growth in recent years. In this context, deep learning-based “learned” solutions are widely opted for many applications thus slowly becoming an inevitable alternative tool. It is known that in contrast to the conventional “physics-based” approach, deep learning models are known to be a “data-driven” approach where the outcomes are based on data analysis and interpretation. Thus, the deep learning approaches have applied for several (optical and computational) imaging based scientific problems such as denoising, phase retrieval, hologram reconstruction and histopathology, to name a few. In this talk, I will briefly discuss the role of deep learning networks for imaging-based problem solving applications and will provide the future direction for those approaches.

The advancement in data transfer and storage technology has prompted new challenges for its
secure transmission. Everyday a huge amount of data (images, passwords, bank details etc.)
is transmitted through open channels, making it vulnerable to intruders. To ensure the safe
transmission, several optical and digital encryption techniques have been explored. Mostly,
the security keys used in the existing image encryption methods are computer generated noise
like distributions having uniformly distributed histogram. Statistically, an attacker may
retrieve these keys if he/she will have partial/full knowledge of the cryptosystem or its
constituents. In this paper, we propose a new asymmetric cryptosystem for phase image
encryption which uses the physically unclonable functions (PUFs) as security keys. The
PUFs are the speckle patterns recorded optically by scattering of vortex beams through
ground glass diffuser (GGD) having unique properties. For encryption, the original amplitude
image is first converted to a phase image and modulated with a PUF to get the complex
image. This complex image is then illuminated with a plane wave and the complex wavefront
at a distance d is recorded. The real part of the complex wavefront is further processed to get
the encrypted image and the imaginary part is kept as the first private key. Polar
decomposition approach is utilized for generating two more private security keys and to
enable the multi-user capability in the cryptosystem. Numerical simulation results consisting
of encryption/decryption, key sensitivity and robustness analysis will be shown in support of
the proposed method.

Fourier transform holography overcomes the phase recovery challenge by recording complex field information of the object in an interference pattern recorded at the far field, i.e., Fourier plane. Moreover, this geometry helps to reconstruct the complex field of the object from a single Fourier transform which is an attractive feature for numerical reconstruction of the digitally recorded hologram. In this paper, we present a nearly common path experimental design for recording of a digital Fourier holographic hologram using a beam displacer, and recover the complex valued objects using the Fourier analysis. The performance of the system is experimentally examined for different objects.

The usability of non-amplified laser systems in additive manufacturing via femtosecond-laser direct writing is presented. Photo-structuring of hybrid organic-inorganic SZ2080TM pre-polymer without using any photo-initiator is realized using ~100 fs oscillator operating at 517 nm wavelength and 76 MHz repetition rate. The proof of concept is experimentally demonstrated and benchmarking 3D woodpile nanostructures, micro-scaffolds, free-form micro-object “Benchy” and bulk micro-cubes are successfully produced. Also, the outlook for using fundamental 1030 nm wavelength excitation of oscillators for optimal fabrication conditions is discussed. The validated method opposes the necessity to use higher pulse energies and lower repetition rates of amplified lasers for structuring non-photosensitized polymers. The experimental work is of high importance for the principal understanding of laser-enabled nanoscale 3D additive manufacturing and widens technology’s field of applications where the avoidance of photo-initiator is preferable or is even a necessity, such as micro-optics, nano-photonics, and biomedicine.

The near-eye display (NED) devices are required to provide visual instructions in the fields of education, navigation, military operations, construction, healthcare, etc. The issues with conventional NEDs are the vergence-accommodation conflict (VAC) and form factor. The Maxwellian display alleviates the VAC in NEDs by providing always-focused images to the viewer regardless of the depth of focus of the human eye. The main limitation of the Maxwellian display has a limited exit pupil size. Due to misalignment of the device or eyeball rotation, the user may miss the eye box, and the image will become lost. To mitigate this limitation, exit pupil expansion can be obtained either statically or dynamically. This paper reviews the various techniques employed to expand the exit pupil. The review includes the principle, advantages, and drawbacks of various techniques for expanding the exit pupil of the Maxwellian display. The structure of the paper starts with an introduction and the principle of the Maxwellian display, followed by a discussion of the main limitations that arise with various techniques, along with potential solutions.

Holography is a prominent 3D display approach as it offers a realistic 3D display without the need for special glasses. Due to advancements in computation power and optoelectronic technology, holographic displays have emerged as widely appreciated technology among other 3D display technologies and have drawn a lot of research interest in recent years. The core of dynamic holographic displays is spatial light modulator (SLM) technology. However, owing to the limited resolution and large pixel size of SLMs, holographic displays suffer from certain bottlenecks such as limited field of view (FOV) and narrow viewing angle. To develop a holographic display at the commercial level, it is crucial to solve these problems. A variety of probable solutions to these challenges may be found in the literature. In this review, we discuss the essence of these approaches. We study the important milestones of the various methodologies from three primary perspectives: devices, optical systems, and algorithms employed for FOV extension, and provide useful insights for future research.