Ganbat Baasantseren

Fresnel and Fourier hologram generation using orthographic projection images

A novel technique for synthesizing a hologram of three-dimensional objects from multiple orthographic projection view images is proposed. The three-dimensional objects are captured under incoherent white illumination and their orthographic projection view images are obtained. The orthographic projection view images are multiplied by the corresponding phase terms and integrated to form a Fourier or Fresnel hologram. Using simple manipulation of the orthographic projection view images, it is also possible to shift the three-dimensional objects by an arbitrary amount along the three axes in the reconstruction space or invert their depths with respect to the given depth plane. The principle is verified experimentally.

View image generation in perspective and orthographic projection geometry based on integral imaging.

A novel technique generating arbitrary view images in perspective and orthographic geometry based on integral imaging is proposed. After capturing three-dimensional object using a lens array, disparity estimation is performed for the pixels at the selected position of each elemental image. According to the estimated disparity, appropriate parts of elemental images are mapped to synthesize new view images in perspective or orthographic geometry. As a result, the proposed method is capable of generating new view images at arbitrary positions with high resolution and wide field of view.

Viewing angle enhanced integral imaging display using two elemental image masks.

A viewing angle enhanced integral imaging display using two elemental image masks is proposed. In our new method, rays emitted from the elemental images are directed by two masks into corresponding lenses. Due to the elemental image guiding of the masks, the number of elemental images for each integrated image point is increased, enhancing the viewing angle. The experimental result shows that the proposed method exhibits two times larger viewing angle than the conventional method with the same lens array.

Hologram Generation of 3D Objects Using Multiple Orthographic View Images

We propose a new synthesis method for the hologram of 3D objects using incoherent multiple orthographic view images. The 3D objects are captured and their multiple orthographic view images are generated from the captured image. Each orthographic view image is numerically overridden by the plane wave propagating in the direction of the corresponding view angle and integrated to form a point in the hologram plane. By repeating this process for all orthographic view images, we can generate the Fourier hologram of the 3D objects.

Resolution enhancement of integral‐imaging three‐dimensional display using directional elemental image projection

— A new approach to resolution enhancement of an integral-imaging (II) three-dimensional display using multi-directional elemental images is proposed. The proposed method uses a special lens made up of nine pieces of a single Fresnel lens which are collected from different parts of the same lens. This composite lens is placed in front of the lens array such that it generates nine sets of directional elemental images to the lens array. These elemental images are overlapped on the lens array and produce nine point light sources per each elemental lens at different positions in the focal plane of the lens array. Nine sets of elemental images are projected by a high-speed digital micromirror device and are tilted by a two-dimensional scanning mirror system, maintaining the time-multiplexing sequence for nine pieces of the composite lens. In this method, the concentration of the point light sources in the focal plane of the lens array is nine-times higher, i.e., the distance between two adjacent point light sources is three times smaller than that for a conventional II display; hence, the resolution of three-dimensional image is enhanced.

Integral-floating Display with 360 Degree Horizontal Viewing Angle

A three-dimensional integral-floating display with 360 degree horizontal viewing angle is proposed. A lens array integrates two-dimensional elemental images projected by a digital micro-mirror device, reconstructing three-dimensional images. The three-dimensional images are then relayed to a mirror via double floating lenses. The mirror rotates in synchronization with the digital micro-mirror device to direct the relayed three-dimensional images to corresponding horizontal directions. By combining integral imaging and the rotating mirror scheme, the proposed method displays full-parallax three-dimensional images with 360 degree horizontal viewing angle.

Three-Dimensional Display System Based on Integral Imaging with Viewing Direction Control

We propose a three-dimensional display system based on integral imaging with viewing direction control. In the proposed method, 4-f illumination optics with a dynamic aperture are used to direct the displayed three-dimensional images to the viewer. It is also possible to control the divergence or convergence of the illumination for an optimized display of real or virtual images. The principle of the proposed method was verified experimentally.

Advanced 360-Degree Integral-Floating Display Using a Hidden Point Removal Operator and a Hexagonal Lens Array

An enhanced 360-degree integral-floating three-dimensional display system using a hexagonal lens array and a hidden point removal operator is proposed. Only the visible points of the chosen three-dimensional point cloud model are detected by the hidden point removal operator for each rotating step of the anamorphic optics system, and elemental image arrays are generated for the detected visible points from the corresponding viewpoint. Each elemental image of the elemental image array is generated by a hexagonal grid, due to being captured through a hexagonal lens array. The hidden point removal operator eliminates the overlap problem of points in front and behind, and the hexagonal lens array captures the elemental image arrays with more accurate approximation, so in the end the quality of the displayed image is improved. In an experiment, an anamorphic-optics-system-based 360-degree integral-floating display with improved image quality is demonstrated.

Integral floating-image display using two lenses with reduced distortion and enhanced depth

— An integral floating display (IFD) with a long depth range without floating lens distortion is proposed. Two lenses were used to reduce barrel distortion of the floating lens and three-dimensional (3-D) image deformation from object-dependent longitudinal and lateral magnifications in the floating-display system, combined with an integral imaging display. The distance between the floating lenses is the sum of their focal lengths. In the proposed configuration, lateral and longitudinal magnifications are constant regardless of the distance of the integrated 3-D images, so the distortions from the distant-dependent magnifications of the floating lens do not occur with the proposed method. In addition, the proposed floating system expands the depth range of the integral imaging display. As a result, the display can show a correct 3-D floating image with a large depth range. Experimental results demonstrate that the proposed method successfully displays a 3-D image without floating lens distortions across a large depth range.

Fourier hologram generation of 3D objects using multiple orthographic view images captured by lens array

We propose a new synthesis method for the hologram of 3D objects using multiple orthographic view images captured by lens array. The 3D objects are captured through a lens array under normal incoherent illumination, and their multiple orthographic view images are generated from the captured image. Each orthographic view image is numerically overridden by the plane wave propagating at the direction of the corresponding projection angle and integrated into a single complex value, which constitutes one pixel in the synthesized hologram. By repeating this process for all orthographic view images, we can generate the Fourier hologram of the 3D objects. Since the proposed method generates the hologram not from the interference with the reference beam, but from the multiple view images, coherent system is not required. The manipulation of the 3D information of the objects is also easily achieved in the proposed method. By manipulating coordinate information of each orthographic view image according corresponding view angle, the depth order of the reconstructed 3D object can be controlled.