Aneta Michalkiewicz

Digital Holographic Capture and Optoelectronic Reconstruction for 3D Displays

The application of digital holography as a viable solution to 3D capture and display technology is examined. A review of the current state of the field is presented in which some of the major challenges involved in a digital holographic solution are highlighted. These challenges include (i) the removal of the DC and conjugate image terms, which are features of the holographic recording process, (ii) the reduction of speckle noise, a characteristic of a coherent imaging process, (iii) increasing the angular range of perspective of digital holograms (iv) and replaying captured and/or processed digital holograms using spatial light modulators. Each of these challenges are examined theoretically and several solutions are put forward. Experimental results are presented that demonstrate the validity of the theoretical solutions.

Holographic three-dimensional displays with liquid crystal on silicon spatial light modulator

One of the ways to achieve 3D objects visualization is holography. The recent progress of CCD/CMOS cameras provides quick development of digital holographic recording. Optoelectronic reconstruction of digital holograms can be realized by means of variety of spatial light modulators, however each of them suffers several limitations due to big pixel size, low diffraction efficiency and noise. In the paper high efficiency liquid crystal on silicon (LCOS) spatial light modulator is proposed as the novel solution for optoelectronic holographic reconstruction. The system for holograms reconstruction based on LCOS is presented. The results of initial experiments on reconstruction of computer generated and digital holograms of different classes of 2D and 3D objects are shown and discussed. The problems connected with limited resolution of the recording (CCD) and reconstruction (LCOS) devices are considered. The comparison of the results obtained by numerical and optoelectronic reconstruction of digital holograms is presented, together with a discussion of the limitations and further possibilities of these techniques.

Phase manipulation and optoelectronic reconstruction of digital holograms by means of LCOS spatial light modulator

Fresnel and Fourier holograms recorded by CCD/CMOS cameras can be numerically or optoelectronically reconstructed in order to provide visualization of 3D objects or to enable further manipulation of their phases and amplitudes. In the paper we propose to introduce into digital holographic (DH) setup Liquid Crystal on Silicon (LCOS) spatial light modulator as an active 2D optoelectronic element which facilitates performing a variety of operations at the recording and reconstruction stages. This includes introducing phase shifting digital holography, additional phase manipulation for object contouring and displacement measurements as well as for optoelectronic reconstruction of all types of digital holograms. The results of initial experiments performed with LCOS are presented and discussed. Also the future directions of development of active DH and DHI system are outlined.

Digital holographic cameras and data processing for remote monitoring and measurements of mechanical parts

Fast growing technology and requirements for testing of different types of materials and devices require new methods and systems for investigation of their parameters. Among the quantities of high interest are shape, deformation, roughness, local materials constants, displacement, and strain fields of elements under load. In the paper, we present novel solutions for digital holographic cameras, which allow for remote monitoring and measurement of the above mentioned quantities at small mechanical objects or at restricted areas of interest at big structures. The systems have compact design, “black box” measurement approach, and allows for fast and accurate measurements performed directly at the element and often in outdoor environment. The principles of digital and optoelectronic reconstruction and phase manipulation are described together with the exemplary measurement results obtained by means of the cameras presented.

Miniaturized low-cost digital holographic interferometer

Digital holography (DH) and digital holographic interferometry (DHI) are very useful, robust, full-field visualization and measurement techniques applied for small objects, especially in the field of bioengineering and microelements system testing. Nowadays CCD/CMOS detectors and microlasers allow to build miniaturized and compact digital holographic head. Various approaches to develop DH/DHI systems including a variety of optical and mechanical solutions have been made. The main recent requirements for holocamera design include compactness, insensitivity to vibrations environmental changes and with good quality of output data. Other requirement is the ability to build a low-cost and robust system for sensing applications. In our paper, we propose a design of miniaturized holo-camera head with fibre optics light delivery system and remote data read-out. The opto-mechanical architecture allows out-of-plane and shape measurements of diffuse and reflective surfaces. The possible data capture schemes and software for enhanced quality numerical reconstruction of complex objects are discussed and the optimized methodology is determined. Also real-time optoelectronic hologram reconstruction is demonstrated on the base of remote data delivery to liquid crystal on silicon spatial light modulator. The performance of the system is tested on the resolution amplitude test and master sphere, while engineering objects in the experiments are static and dynamic microelements.

Simulation, registration, and reconstruction of digital holograms of arbitrary objects by means of liquid crystal on silicon spatial light modulator

Each hologram: optical, digital and computer generated represents the phase and amplitude of an object. Therefore the process of object reconstruction may rely on one of two alternative procedures: optoelectronic direct reconstruction of hologram, which is represented by diffractive structure intensity, and recombining of object phase and amplitude as calculated from wavefront propagation process (here the method is based on singular wave component that is derived from a rigorous Sommerfelds solution) or numerical reconstruction of digital hologram. In the paper we present the comparison of these two ways of optoelectronic reconstruction. The pros and cons for application of these procedures from image quality point of view are given. The experimental systems based on a Twyman-Green interferometer with two phase and amplitude LCOS or on a single digital hologram or computer generated hologram reconstruction setup are presented. The conclusions of these experiments will be utilized for optimizing of the process of production of security holograms with use of LCOS modulators.

The C3PO project: a laser communication system concept for small satellites

The satellite market is shifting towards smaller (micro and nanosatellites), lowered mass and increased performance platforms. Nanosatellites and picosatellites have been used for a number of new, innovative and unique payloads and missions. This trend requires new concepts for a reduced size, a better performance/weight ratio and a reduction of onboard power consumption. In this context, disruptive technologies, such as laser-optical communication systems, are opening new possibilities. This paper presents the C3PO1 system, “advanced Concept for laser uplink/ downlink CommuniCation with sPace Objects”, and the first results of the development of its key technologies. This project targets the design of a communications system that uses a ground-based laser to illuminate a satellite, and a Modulating Retro-Reflector (MRR) to return a beam of light modulated by data to the ground. This enables a downlink, without a laser source on the satellite. This architecture suits well to small satellite applications so as high data rates are potentially provided with very low board mass. C3PO project aims to achieve data rates of 1Gbit/s between LEO satellites and Earth with a communication payload mass of less than 1kilogram. In this paper, results of the initial experiments and demonstration of the key technologies will be shown.

Development of a miniature digital holographic interferometry system

The scope of this work is to develop a miniature digital holographic interferometry (DHI) system enabling remote measurements of shape and deformation of small 3D objects. Due to the use of digital holography the system does not require holographic plates but uses a simple digital camera for recording of holograms. Object intensity and phase is reconstructed numerically by Fresnel approach and can be applied for monitoring of object changes. In the paper the variety of systems described in literature are presented and analyzed. The configuration of novel digital holographic interferometer is described and the phase analysis method and scaling algorithms are presented. The initial experimental results obtained by means of DHI demonstrator are presented for the case of a small active micro membrane testing. The error analysis and further suggestions toward design of the final version of DHI system are given.

Digital holocameras for laboratory and outdoor measurements of engineering objects

Industrial inspection requires very fast and reliable measurements. One of the techniques, recently widely used for monitoring of engineering objects, is digital holographic interferometry (DHI). In the paper we present novel digital holographic cameras (DHC). Their configuration allows to provide high accuracy information about shape, out-of-plane and in-plane displacement distributions, through capture of digital hologram by CCD, numerical reconstruction of phases and their proper manipulation. Digital holographic systems presented have compact design, fibre optics light delivery system and automatic data acquisition and processing. The cameras capture data in real-time and have low sensitivity to environmental changes. In the paper several examples of engineering application of these cameras are presented.

Digital Holographic Interferometers Cameras for Remote Monitoring and Measurements of Mechanical Parts

Fast growing technology and requirements for testing of different types of materials and devices require new methods and systems for investigation of their parameters. Main interesting quantities are: shape, roughness, local materials constants and displacements of elements under load. One of many techniques for analysis of different types of elements is holography and holographic interferometry and in particular their digital versions. They allow remote monitoring and measurement of different parameters in the same setup. At the moment we observe fast development of holographic systems for microelements and microregion studies. Those systems with compact design and “black box” measurement approach should allow fast and accurate measurement performed directly at the element and often in outdoor environment.