Gee-young Sung

Optimal synthesis of double-phase computer generated holograms using a phase-only spatial light modulator with grating filter.

We propose an optical system for synthesizing double-phase complex computer-generated holograms using a phase-only spatial light modulator and a phase grating filter. Two separated areas of the phase-only spatial light modulator are optically superposed by 4-f configuration with an optimally designed grating filter to synthesize arbitrary complex optical field distributions. The tolerances related to misalignment factors are analyzed, and the optimal synthesis method of double-phase computer-generated holograms is described.

Modulation efficiency of double-phase hologram complex light modulation macro-pixels

The modulation efficiency of the double-phase hologram macro-pixel that is designed for complex modulation of light waves is defined and analyzed. The scale-down of the double-phase hologram macro-pixel associated with the construction of complex spatial light modulators is discussed.

61.4: Active Crosstalk Reduction on Multi‐View Displays Using Eye Detection

Multi-view displays have some problems in the quality of images, while they provide glasses-free systems. Especially inter-view crosstalk is the most critical factor to deteriorate the image quality and cause visual fatigue under large depths. We propose a method to provide clear images appropriate to the positions of the observers eyes. In a subpixel group, using the visibility profiles of the subpixels expressing each view, we can determine the subpixel values to express a certain color at a certain direction. This can compensate color distortion caused by slanted lenticular lens and expand the observable area using the repeated regions neighboring the main region.

Holographic display with a FPD-based complex spatial light modulator

We demonstrate a holographic image reconstructed by a FPD-based complex spatial light modulator (SLM) which is composed of a phase-only SLM and a sheet of beam combiner. A complex SLM which modulates both amplitude and phase independently is necessary for a better image quality with reducing conjugate images. The two-phase encoding method is one of the most practical candidates for the complex SLM. The proposed complex SLM is presented in a phase-only LCD panel which can be manufactured in a conventional LCD process and it was used for generating different phases. The PAL (Parallel-Aligned nematic Liquid crystal) mode is used to modulate the phase without the amplitude change. The film-type beam combiner consists of a prism array and a grating made by a conventional fabrication process. The beam combiner plays a vital role to merge two pixels and to adjust effective complex modulation. In this paper, the holographic image by the proposed complex SLM is verified by the experimental and simulation work in a monochromatic reconstruction. This complex SLM can be scaled up and it is a promising candidate SLM for a large-size holographic 3D display.

Enhancement of the effective viewing window for holographic display with amplitude-only SLM

We propose the effective viewing window enhancement method for a holographic display with an amplitude-only SLM by using algorithmic approach. The basic concept is the superposition principle of holography. The multiple computer generated holograms (CGH) can be displayed on the SLM, and multiple 3D images are reconstructed at different positions within a viewing window simultaneously. In the experiments, we have implemented the holographic display using an amplitude-only SLM, a field lens, and laser light sources. We can observe the holographic 3D image in the frustum formed by the field lens through the viewing window located in the Fourier plane of the hologram. To enhance the effective viewing window, we generate multiple CGHs with an observer’s eye positions, and then overlap them to make the final CGH. Multiple 3D images can be reconstructed in different positions within the theoretical viewing window from the CGH displayed on SLM. This makes the enlargement of viewing zone that can observe the holographic images. The multiple holograms can be also made for enlargement of the viewing window along both horizontal and vertical direction (2D enlargement viewing zone). We confirmed that the experimental results and the simulation based on Rayleigh-Sommerfeld theory match well.

Ultra-slim coherent backlight unit for mobile holographic display

We propose slim coherent backlight unit for a mobile holographic display. This backlight unit consists of glass substrate for waveguide and two surface gratings produced by two-beam interference. The area of backlight illumination is 150 by 85 mm, and the thickness is 0.7 mm, which is thin compared to other conventional coherent backlight units. This backlight unit exhibits a total efficiency of 0.1%, preserving the collimation and a uniformity of 80% over the whole area. The proposed slim coherent backlight can be applied to a mobile holographic display.

Inversion-free multiview subpixel rendering for natural 3D presentation

In this paper, an inversion-free subpixel rendering method that uses eye tracking in a multiview display is proposed. The multiview display causes an inversion problem when one eye of the user is focused on the main region and the other eye is focused on the side region. In the proposed method, the subpixel values are rendered adaptively depending on the eye position of the user to solve the inversion problem. Also, to enhance the 3D resolution without the color artifact, the subpixel rendering algorithm using subpixel area weighting is proposed instead of the pixel values. In the experiments, 36-view images were seen using active subpixel rendering with the eye tracking system in a four-view display.