Seung-Cheol Kim

Effective memory reduction of the novel look-up table with one-dimensional sub-principle fringe patterns in computer-generated holograms

We propose a novel approach to massively reduce the memory of the novel look-up table (N-LUT) for computer-generated holograms by employing one-dimensional (1-D) sub-principle fringe patterns (sub-PFPs). Two-dimensional (2-D) PFPs used in the conventional N-LUT method are decomposed into a pair of 1-D sub-PFPs through a trigonometric relation. Then, these 1-D sub-PFPs are pre-calculated and stored in the proposed method, which results in a remarkable reduction of the memory of the N-LUT. Experimental results reveal that the memory capacity of the LUT, N-LUT and proposed methods have been calculated to be 149.01 TB, 2.29 GB and 1.51 MB, respectively for the 3-D object having image points of 500 × 500 × 256, which means the memory of the proposed method could be reduced by 103 × 10(6) fold and 1.55 × 10(3) fold compared to those of the conventional LUT and N-LUT methods, respectively.

Fast generation of video holograms of three-dimensional moving objects using a motion compensation-based novel look-up table.

A novel approach for fast generation of video holograms of three-dimensional (3-D) moving objects using a motion compensation-based novel-look-up-table (MC-N-LUT) method is proposed. Motion compensation has been widely employed in compression of conventional 2-D video data because of its ability to exploit high temporal correlation between successive video frames. Here, this concept of motion-compensation is firstly applied to the N-LUT based on its inherent property of shift-invariance. That is, motion vectors of 3-D moving objects are extracted between the two consecutive video frames, and with them motions of the 3-D objects at each frame are compensated. Then, through this process, 3-D object data to be calculated for its video holograms are massively reduced, which results in a dramatic increase of the computational speed of the proposed method. Experimental results with three kinds of 3-D video scenarios reveal that the average number of calculated object points and the average calculation time for one object point of the proposed method, have found to be reduced down to 86.95%, 86.53% and 34.99%, 32.30%, respectively compared to those of the conventional N-LUT and temporal redundancy-based N-LUT (TR-N-LUT) methods.

Time-sequential autostereoscopic 3-D display with a novel directional backlight system based on volume-holographic optical elements.

A novel directional backlight system based on volume-holographic optical elements (VHOEs) is demonstrated for time-sequential autostereoscopic three-dimensional (3-D) flat-panel displays. Here, VHOEs are employed to control the direction of light for a time-multiplexed display for each of the left and the right view. Those VHOEs are fabricated by recording interference patterns between collimated reference beams and diverging object beams for each of the left and right eyes on the volume holographic recording material. For this, self-developing photopolymer films (Bayfol® HX) were used, since those simplify the manufacturing process of VHOEs substantially. Here, the directional lights are similar to the collimated reference beams that were used to record the VHOEs and create two diffracted beams similar to the object beams used for recording the VHOEs. Then, those diffracted beams read the left and right images alternately shown on the LCD panel and form two converging viewing zones in front of the users eyes. By this he can perceive the 3-D image. Theoretical predictions and experimental results are presented and the performance of the developed prototype is shown.

MPEG-based novel look-up table for rapid generation of video holograms of fast-moving three-dimensional objects.

A new robust MPEG-based novel look-up table (MPEG-NLUT) is proposed for accelerated computation of video holograms of fast-moving three-dimensional (3-D) objects in space. Here, the input 3-D video frames are sequentially grouped into sets of four, in which the first and remaining three frames in each set become the reference (RF) and general frames (GFs). Then, the frame images are divided into blocks, from which motion vectors are estimated between the RF and each of the GFs, and with these estimated motion vectors, object motions in all blocks are compensated. Subsequently, only the difference images between the motion-compensated RF and each of the GFs are applied to the NLUT for CGH calculation based on its unique property of shift-invariance. Experiments with three types of test 3-D video scenarios confirm that the average number of calculated object points and the average calculation time of the proposed method, have found to be reduced down to 27.34%, 55.46%, 45.70% and 19.88%, 44.98%, 30.72%, respectively compared to those of the conventional NLUT, temporal redundancy-based NLUT (TR-NLUT) and motion compensation-based NLUT (MC-NLUT) methods.

Fast one-step calculation of holographic videos of three-dimensional scenes by combined use of baseline and depth-compensating principal fringe patterns

As a new approach for rapid generation of holographic videos, a so-called compressed novel-look-up-table(C-NLUT), which is composed of only two principal fringe patterns (PFPs) of baseline and depth-compensating PFPs (B-PFP, DC-PFP), is proposed. Here, the hologram pattern for a 3-D video frame are generated by calculating the fringe patterns for all depth layers only by using the B-PFP, and then transforming them into those for their depth layers by being multiplied with corresponding DC-PFPs. With this one-step calculation process, the computational speed (CS) of the proposed method can be greatly enhanced. Experimental results show that the CS of the proposed method has been improved by 30.2% on the average compared to that of the conventional method. Furthermore, the average calculation time of a new hybrid MC/C-NLUT method, in which both of motion-compensation (MC) and one-step calculation schemes are employed, has been reduced by 99.7%, 65.4%, 60.2% and 30.2%, respectively compared to each of the conventional ray-tracing, LUT, NLUT, and MC-NLUT methods. In addition, the memory size of the proposed method has been also reduced by 82 × 10(6)-fold and 128-fold compared to those of the conventional LUT and NLUT methods, respectively.

Three-directional motion compensation-based novel-look-up-table for video hologram generation of three-dimensional objects freely maneuvering in space.

A new three-directional motion compensation-based novel-look-up-table (3DMC-NLUT) based on its shift-invariance and thin-lens properties, is proposed for video hologram generation of three-dimensional (3-D) objects moving with large depth variations in space. The input 3-D video frames are grouped into a set of eight in sequence, where the first and remaining seven frames in each set become the reference frame (RF) and general frames (GFs), respectively. Hence, each 3-D video frame is segmented into a set of depth-sliced object images (DOIs). Then x, y, and z-directional motion vectors are estimated from blocks and DOIs between the RF and each of the GFs, respectively. With these motion vectors, object motions in space are compensated. Then, only the difference images between the 3-directionally motion-compensated RF and each of the GFs are applied to the NLUT for hologram calculation. Experimental results reveal that the average number of calculated object points and the average calculation time of the proposed method have been reduced compared to those of the conventional NLUT, TR-NLUT and MPEG-NLUT by 38.14%, 69.48%, and 67.41% and 35.30%, 66.39%, and 64.46%, respectively.

Object tracking mask-based NLUT on GPUs for real-time generation of holographic videos of three-dimensional scenes

A new object tracking mask-based novel-look-up-table (OTM-NLUT) method is proposed and implemented on graphics-processing-units (GPUs) for real-time generation of holographic videos of three-dimensional (3-D) scenes. Since the proposed method is designed to be matched with software and memory structures of the GPU, the number of compute-unified-device-architecture (CUDA) kernel function calls and the computer-generated hologram (CGH) buffer size of the proposed method have been significantly reduced. It therefore results in a great increase of the computational speed of the proposed method and enables real-time generation of CGH patterns of 3-D scenes. Experimental results show that the proposed method can generate 31.1 frames of Fresnel CGH patterns with 1,920 × 1,080 pixels per second, on average, for three test 3-D video scenarios with 12,666 object points on three GPU boards of NVIDIA GTX TITAN, and confirm the feasibility of the proposed method in the practical application of electro-holographic 3-D displays.

Graphics processing unit-based implementation of a one-dimensional novel-look-up-table for real-time computation of Fresnel hologram patterns of three-dimensional objects

Abstract. A one-dimensional novel-look-up-table (1-D N-LUT) has been implemented on the graphics processing unit of GTX 690 for the real-time computation of Fresnel hologram patterns of three-dimensional (3-D) objects. For that, three types of optimization techniques have been employed, which include the packing technique of input 3-D object data and the managing techniques of on-chip shared memory and registers. Experimental results show that the average hologram calculation time for one object point of the proposed system has been found to be 0.046 ms, which confirms that the proposed system can generate almost 3 frames of Fresnel holograms with 1920×1080  pixels per second for a 3-D object with 8000 object points.

Three-directional motion-compensation mask-based novel look-up table on graphics processing units for video-rate generation of digital holographic videos of three-dimensional scenes

A three-directional motion-compensation mask-based novel look-up table method is proposed and implemented on graphics processing units (GPUs) for video-rate generation of digital holographic videos of three-dimensional (3D) scenes. Since the proposed method is designed to be well matched with the software and memory structures of GPUs, the number of compute-unified-device-architecture kernel function calls can be significantly reduced. This results in a great increase of the computational speed of the proposed method, allowing video-rate generation of the computer-generated hologram (CGH) patterns of 3D scenes. Experimental results reveal that the proposed method can generate 39.8 frames of Fresnel CGH patterns with 1920×1080 pixels per second for the test 3D video scenario with 12,088 object points on dual GPU boards of NVIDIA GTX TITANs, and they confirm the feasibility of the proposed method in the practical application fields of electroholographic 3D displays.

Slim-structured electro-floating display system based on the polarization-controlled optical path.

A new slim-type electro-floating display system based on the polarization-controlled optical path is proposed. In the proposed system, the optical path between the input plane and Fresnel lens can be made recursive by repetitive transmission and reflection of the input beam by employing a new polarization-based optical path controller (P-OPC), which is composed of two quaterwave plates, a half mirror and a reflective polarizer. Based on this P-OPC, the absolute optical path between the input plane and Fresnel lens, virtually representing the physical depth of the display system, can be reduced down to one third of its original path, which results in the same rate of decrease in the volume size of the display system. The operational principle of the proposed system is analyzed with the Jones matrix. In addition, to confirm the feasibility of the proposed system, experiments with test prototypes are carried out, and the results are comparatively discussed with those of the conventional system.