Acceleration of color computer-generated hologram from RGB-D images using color space conversion

We report acceleration of color computer-generated holograms (CGHs) from three dimensional (3D) scenes that are expressed as RGB and depth (D) images. These images are captured by a depth camera and depth buffer of 3D graphics library. RGB and depth images preserve color and depth information of 3D scene, respectively. Then we can regard them as two-dimensional (2D) section images along the depth direction. In general, convolution-based diffraction such as the angular spectrum method is used in calculating CGHs from the 2D section images. However, it takes enormous amount of time because of multiple diffraction calculations. In this paper, we first describe “band-limited double-step Fresnel diffraction (BL-DSF)” which can accelerate the diffraction calculation than convolution-based diffraction. Next, we describe acceleration of color CGH using color space conversion. Color CGHs are generally calculated on RGB color space; however, we need to perform the same calculations for each color component repeatedly, so that computational cost of color CGH calculation is three times as that of monochrome CGH calculation. Instead, we use YCbCr color space because the 2D section images on YCbCr color space can be down-sampled without deterioration of the image quality.