Sanjeev Solanki

Digital holographic three-dimensional display of 50-Mpixel holograms using a two-axis scanning mirror device

The current limitation in pixel count of a single spatial light modulator SLM is one of the technological hurdles that must be over- come to produce a holographic 3-D display with a large image size. A conventional approach is to tile subholograms that are predivided from a reconfigurable computer-generated hologram CGH with a high pixel count. We develop a new approach to achieve a 50 Mpixel display by tiling reconstructed subholograms computed from a predivided 3-D ob- ject. The tiling is done using a two-axis scanning mirror device with a new tiling sequence. A shutterless system design is also implemented to enable effective tiling of subholograms. A high-speed digital micromirror device DMD at 6 kHz with 19201080 pixels is utilized to reconstruct the subholograms. Our current system shows the potential to tile up to 120 subholograms, which corresponds to about 240 Mpixels. The ap- proach we demonstrate gives a scalable solution to achieve a gigapixel- level display in the future.

Development of full-color full-parallax digital 3D holographic display system and its prospects

We have developed a full-color full-parallax digital 3D holographic display system by using 24 physically tiled SLMs, an optical scan tiling approach and two sets of RGB lasers, which could display 378-Mpixel holograms at 60 Hz, with a displayed image size of 10 inch in diagonal. In this paper, we will review and compare three different holographic display systems developed by our group from various aspects, including SLMs, lasers, optics designs, hologram computation, data transmission, and system synchronization. We will also discuss the bottlenecks and prospects of further development of the system for practical applications.

Full High-Definition Digital 3D Holographic Display and Its Enabling Technologies

Holographic display is a true three-dimensional (3D) display technology presenting all depth cues without using any special glasses. In this paper, we first introduce a monochrome digital 3D holographic display system developed at Data Storage Institute (DSI), which is capable of displaying both static and dynamic 3D objects reconstructed from computer-generated holograms (CGHs). The system can also display 50-Mpixel holograms at 25 Hz refresh rate via a novel hologram tiling approach, which enables the increase of displayed image size. A futuristic vision for full high-definition (HD) digital 3D holographic display is then proposed and analyzed. The dynamic reconstruction of full-HD 3D objects from CGHs has been preliminarily demonstrated. Finally, we introduce the development trends of its enabling technologies such as highperformance computing, new algorithms, data storage and transmission, spatial light modulator (SLM) and RGB (red, green and blue) laser sources.

Dynamic display of 3D objects in real and virtual spaces with computer-generated holography

In this paper a new holographic 3D display system based on computer-generated hologram (CGH) is developed for the reconstruction of 3D objects. A new algorithm is also developed to reduce the hologram computation time and memory usage. The dynamic 3D objects are successfully reconstructed at video rates in both real and virtual spaces.

Regular effective hologram regions for computer generated holography

An effective hologram region (EHR) based approach is presented to speed up the computation of computer generated holograms (CGHs). The object space is predivided into subspaces, and an EHR for each subspace is predefined according to the maximum spatial frequency of interference fringes, light diffraction efficiency, and CGH binarization effect. To compute the hologram of an object, the object points are first categorized according to which subspace they are located in, and then their holograms are calculated using the corresponding EHRs. As each EHR usually takes up only a portion of the hologram plate, the CGH computational load is thus reduced. This new approach is highly suitable for large hologram display systems. In addition, when compared to the reconstructed image using the conventional approach, our experimental results show that more noise can be blocked off and the reconstructed image appears sharper without noticeable brightness reduction.

Background correction of detected digital data page for holographic storage

A real-time background correction technique is reported for digital data page holographic storage. Two inverted binary data pages are recorded at the same location in recording media with two inverted random phase coded reference beams using a rotating half-wave plate. Adding the two detected inverted data pages from same media location creates background image with noise at that media location. The background image is used to successfully perform the background correction to reduce the noise of detected digital data pages.

Adaptive Computation of Computer-Generated Holograms

Regular Effective Hologram Regions (EHRs) for object subspaces are pre-calculated. Object points are categorized online and the corresponding EHRs are used for hologram computation. The use of EHRs increases computational speed and benefits reconstruction quality.

Adaptive computation of computer-generated holograms

This paper proposes an adaptive approach for reducing the computational load of computer-generated holograms (CGHs). Instead of using the whole hologram plate resolution or carrying out point-wise judgment, this approach pre-divides the object space into subspaces and calculates an effective hologram plate region for each subspace according to interference fringe spatial frequency and grating diffraction energy distribution. As both the very low and very high spatial frequency portions are filtered out, the quality of the reconstructed image is even better in terms of sharpness. This space subdivision based approach also makes parallel CGH computing more straightforward. A simple load-balancing strategy is given.

Laminated holographic recording medium based on photorefractive crystals

A laminated holographic recording medium based on photorefractive lithium niobate crystal is reported for the first time. The medium consists of a piece of photorefractive crystal, a data tracking layer, an intermediate dichroic mirror layer and an anti-reflection layer. Such a holographic medium is able to perform hologram recording and retrieving with compatibility with collinear and coaxial holographic recording schemes.

Random Phase 3D-Shift Multiplexing with Spherical Signal-Reference Waves in Reflection Geometry

A 3D-shift multiplexing is reported with converging signal and diverging random phase coded reference beam into the Cu:Ce:Tb:CLN crystal. Shift-selectivity at first null along x,y and z-axis is measured to be 1.5, 5 and 5mm for random phase-coded reference beam. Low capacity data page with only 1-4 kbits were successfully recorded/retrieved and the achievable raw areal density of >350 Gbit/in2 will be reported.