KEYWORDS: Digital holography, Holograms, 3D image reconstruction, Charge-coupled devices, Spherical lenses, Beam splitters, Digital recording, Monte Carlo methods, Numerical analysis, Computer simulations
Digital holography gives new capabilities to the measurements of size, position, shape or velocity of different objects. In general in-line arrangement is used with a CCD device recording the interference pattern and the reconstruction is performed by numerical methods in computer. Some new ideas were used to improve the process of exposure and calculation techniques. The phase-shift technique is widely used in digital holography. Now it is proposed to use the two-reference-beams arrangement, which can replace the phase-shift methods at different cases. Three holograms -- the interference pattern of the object and the two reference waves and the three intensity distribution (of the beams, separately) are recorded and the phase evaluation can be done numerically. The advantage of FFT-algorithm is also applied reducing the computer running time in reconstruction of the image. We have developed another computational method for the reconstruction using Monte-Carlo simulation.
The record of the interference pattern of the object wave and the reference wave is done by the application of high resolution photoplates in holography. After developing the photoplate the reconstruction of the object wave can be realized illuminating the hologram by the reference beam. In digital holography the photographic process is eliminated for the interference patterns are recorded by a CCD camera and the reconstruction can be done virtually using a computer. In general in-line reference beam is used coding the phases for the low resolution of the available CCD devices. The phase-shift technique (or application of two reference beams) can be applied to recover the phase and the amplitude of the image wve at the plane of the CCD matrix. The FFT algorithm is widely used for the reconstruction. Now it is proposed to apply the Monte-Carlo method simulating the diffracted wave to get the intensity distribution at the image plane. The application of Monte-Carlo simulation has a drawback, that is it can be slower than FFT, but its advantages can be significant, namely the intensity pattern of the diffracted wave can be determined along an inclined plane, just a part of the object can be examined if it is required and additionally there are no difficulties in extending it to phase holograms and 3-D objects.
KEYWORDS: Digital holography, Charge-coupled devices, 3D image reconstruction, Monte Carlo methods, Holograms, Physics, CCD cameras, 3D image processing, Image acquisition, Phase shifts
The three-dimensional image formation can be managed by digital holography, where the holograms can be recorded by a CCD camera. As a law resolution of a CCD device, just a small angle between the object beam and the reference beam is allowed. This is the reason why the in-line phase- shifting digital holography is used to avoid the mentioned problem (the zero order beam can be neglected, too). In this paper it is proposed to use an arrangement of two reference beams recording the interference patterns of the object beam and the two reference beams by a CCD matrix. The phase distribution of the object wave can be recovered by a simple algorithm avoiding the uncertainty of the phase. The complex amplitude is used to reconstruct the image of the object by a computer applying the Fresnel transformation.
We propose single photon counting and photon correlation measurements to characterize ultrashort x-ray pulses, in particular to measure their coherence, spectral, and temporal characteristics. Photon coincidence measuremens allow us to measure higher order correlation between photons, from which temporal profiles of the pulses can be recovered.
We solve the problems from the area of nondestructive testing (ND) of the material quality in our laboratory. It is very well known that an optical method (OM) called the holographic interferometry method (HIM) makes possible this check. This contribution deals with some results of research in detection of the carbon composite defects which were obtained by means of this OM. The searching of check processes is the main orientation of our research work. These processes make possible to evaluate the influence of the defects on the modification of the mechanical properties of the tested materials. Such results make possible to determine dangerous nature of these defects with respect to particular way of use of the inspected materials. At the same time the attention is given to the study of methods for searching of defects. In these cases appearances of some types of defects which are of frequent occurence are evaluated.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.