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.
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.
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 Sommerfeld's 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.
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