In this work, we investigate numerical models of selected spatial light modulators (SLMs) to provide an accurate simulation of diffractive effects present in optoelectronic hologram reconstruction, i.e. DC term and higher orders. We focus on reported most influential parameters: (a) fill factor, (b) amplitude modulation of dead space (effect of surface structure between adjacent pixels), (c) phase of dead space (phase modulation profile between adjacent pixels), (d) spatial influence of adjacent pixels on phase modulation value, and (e) number of phase quantization levels. The impact of each factor on modeled diffraction efficiency and orders distribution is investigated. We consider phase-only reflective models of LCoS SLMs on the basis of commercially available architectures. Additionally, the pixelated SLM model is tested on the example of two practical cases.
The digital holography and holographic display constitute the best framework of 3D imaging as they aim to recreate the complete optical field emitted by a recorded scene. In this paper, we present two techniques of Fourier holographic imaging of real world objects. The first solution is an end-to-end full color Fourier holographic imaging approach, which involves standard RGB holographic recording an LED-driven viewing window display. It gives possibility of almost undistorted orthoscopic reconstruction of large real objects. Second architecture uses the same digital holographic content and horizontal parallax rainbow holographic display, which has reduced space bandwidth product requirements.
Recent advances in holographic displays include increased interest in multiplexing techniques, which allow for extension of viewing angle, hologram resolution increase, or color imaging. In each of these situations, the image is obtained by a composition of a several light wavefronts and therefore some wavefront misalignment occurs. In this work we present a calibration method, that allows for correction of these misalignments by a suitable numerical manipulation of holographic data. For this purpose, we have developed an automated procedure that is based on a measurement of positions of reconstructed synthetic hologram of a target object with focus at two different reconstruction distances. In view of relatively long reconstruction distances in holographic displays, we focus on angular deviations of light beams, which result in a noticeable mutual lateral shift and inclination of the component images in space. A method proposed in this work is implemented in a color holographic display unit (single Spatial Light Modulator – SLM) utilizing Space- Division Method (SDM). In this technique, also referred as Aperture Field Division (AFD) method, a significant wavefront inclination is introduced by a color filter glass mosaic plate (mask) placed in front of the SLM. It is verified that an accuracy of the calibration method, obtained for reconstruction distance 700mm, is 34.5 μm and 0.02°, for the lateral shift and for the angular compensation, respectively. In the final experiment the presented method is verified through real-world object color image reconstruction.
Proc. SPIE. 9970, Optics and Photonics for Information Processing X
KEYWORDS: Holograms, Holography, 3D image reconstruction, Digital holography, Sensors, Image processing, Image registration, Spatial light modulators, 3D image processing, RGB color model, RGB color model
In this work we present a high pixel count color holographic registration system that is designed to provide 3D
holographic content of real-world large objects. Captured data is dedicated for holographic displays with a wide-viewing
angle. The registration in color is realized by means of sequential recording with the use of three RGB laser light
sources. The applied Fourier configuration of capture system gives large viewing angle and an optimal coverage of the
detector resolution. Moreover, it enables to filter out zero order and twin image. In this work the captured Fourier
holograms are transformed to general Fresnel type that is more suitable for 3D holographic displays. High resolution and
large pixel count of holographic data and its spatial continuity is achieved through synthetic aperture concept with
camera scanning and subpixel correlation based stitching. This grants an access to many tools of numerical hologram
processing e.g. continuous viewing angle adjustment, and control of 3D image position and size. In this paper the
properties of 1D synthetic aperture (60000 x 2500 pixels) are investigated. Each of the RGB 1D SA holograms is
composed of 71 frames, which after stitching result in approx. 150 Megapixel hologram pixel count and 12° angular field
of view. In experimental part high quality numerical reconstructions for each type of the hologram are shown. Moreover,
the captured holograms are used for generation of hybrid hologram that is assembled from a set of RGB holograms of
different color statues of height below 20 cm. In the final experiment this hybrid hologram as well as RGB hologram of a
single object are reconstructed in the color holographic display.
In this paper we present a wide viewing angle multi SLMs color holographic 3D display. An extended viewing angle is provided by the use of circular setup configuration. To ensure best utilization of spatial bandwidth of a single SLM a temporal multiplexing method for a color reconstruction is applied. Averaged in time modulated component wavefronts overlap in space and create a real color 3D image. We present the display implementation resulting in color reconstruction of computer generated objects and multi-view 2D real object stereogram converted into holographic representation. The applicability of this approach to allow holographic display of big 3D scenes and the future possibilities to extend the spatio-temporal bandwidth of color holographic displays are discussed.
Conventional (analog) holographic interferometry (HI) has been used as a powerful technique in optical metrology since sixties of XX century. However, its practical applications have been constrained because of the cumbersome procedures required for holographic material development. Digital holography has brought significant simplifications due to digital capture of holograms and their further numerical reconstruction and manipulation of reconstructed phases and amplitudes. These features are the fundamentals of double exposure digital holographic interferometry which nowadays is used in such applications as industrial inspection, medical imaging, microscopy and metrology. However another very popular HI technique, namely real time holographic interferometry has not been demonstrated in its digital version. In this paper we propose the experimental-numerical method which allows for real-time DHI implementation. In the first stage a set of digital phase shifted holograms of an object in an initial condition is captured and the phase of an object wavefront in the hologram plane is calculated. This phase is used to address a spatial light modulator, which generates the initial object wavefront. This wavefront (after proper SLM calibration) propagates toward an object and interfere with an actual object wavefront giving real-time interference fringes. The procedure works correctly in the case when CCD camera and SLM LCOS pixel sizes are the same. Usually it is not the case. Therefore we had proposed two different methods which allow the overcome of this mismatch pixel problem. The first one compensates for lateral magnification and the second one is based on re-sampling of a captured phase. The methods are compared through numerical simulations and with experimental data. Finally, the implications of setting up the experiment with the object reference phase compensated by the two approaches are analyzed and the changes in an object are monitored in real time by DHI.
Holography can store full wide angle information about a registered object, since during registration process information
about amplitude and phase of an optical wave scattered from an object is captured. Because of this unique feature people
put hope in holography as the method which can be utilized in a 3D imaging display. In the paper we present the design
of a wide viewing angle display system utilizing multiple Spatial Light Modulators (SLMs). The system is capable of
displaying objects from both virtual and real worlds. In our system we are using phase only reflective SLMs based on
liquid crystal on silicon (LCoS). There are designed to work with normal illumination. However in order to simplify an
optomechanical system of the display here the SLMs are used with an inclined plane wave illumination. Therefore in the
paper at first we focus on determination of a tilt depended SLM calibration, so thus SLM even with highly off axis
inclined illumination is capable of an accurate wave reproduction. Then we focus on obtaining high quality
reconstruction of objects from virtual world. We present an algorithm based on Gerchberg-Saxton scheme and
diffraction computing between tilted and parallel planes. All of the paper discussions are accompanied with experimental
results obtained in the multi SLMs display.