Holographic microinformation hiding.

We propose a holographic microinformation hiding scheme in which the embedding information to be embedded is small and imperceptible to the human eyes. This scheme converts the embedding information into a complex amplitude via scaled diffraction. The complex amplitude of the reduced embedding information is added to the complex amplitude of the host image, followed by conversion to a hologram. The reduced embedded information is inconspicuous from the hologram during the reconstruction process; however, the reduction leads to the degradation of the embedded image quality. Therefore, to improve the quality of the embedded image quality, we employ iterative optimization and the time averaging effect of multiple holograms.

Color computer-generated hologram generation using the random phase-free method and color space conversion.

We propose two calculation methods of generating color computer-generated holograms (CGHs) with the random phase-free method and color space conversion in order to improve the image quality and accelerate the calculation. The random phase-free method improves the image quality in monochrome CGH, but it is not performed in color CGH. We first aimed to improve the image quality of color CGH using the random phase-free method and then to accelerate the color CGH generation with a combination of the random phase-free method and color space conversion method, which accelerates the color CGH calculation due to down-sampling of the color components converted by color space conversion. To overcome the problem of image quality degradation that occurs due to the down-sampling of random phases, the combination of the random phase-free method and color space conversion method improves the quality of reconstructed images and accelerates the color CGH calculation. We demonstrated the effectiveness of the proposed method in simulation, and in this paper discuss its application to lensless zoomable holographic projection.

Random phase-free kinoform for large objects.

We propose a random phase-free kinoform for large objects. When not using the random phase in kinoform calculation, the reconstructed images from the kinoform are heavy degraded, like edge-only preserved images. In addition, the kinoform cannot record an entire object that exceeds the kinoform size because the object light does not widely spread. In order to avoid this degradation and to widely spread the object light, the random phase is applied to the kinoform calculation; however, the reconstructed image is contaminated by speckle noise. In this paper, we overcome this problem by using our random phase-free method and error diffusion method.

Acceleration of computer-generated holograms using tilted wavefront recording plane method.

Computer Generated Holograms (CGH) are generated on computers; however, a great deal of computational power is required because the quality of the image is proportional to the number of point light sources of a 3D object. The Wavefront Recording Plane (WRP) method is an algorithm that enables reduction of the amount of calculations required. However, the WRP method also has a defect; it is not effective in the case of a 3D object with a deep structure. In this study, we propose two improved WRP methods: "Least Square Tilted WRP method" and "RANSAC Multi-Tilted WRP method."