Full parallax synthetic hologram based on SRTM elevation terrain data

Three-dimensional terrain data have a wide range of applications in urban planning, environmental monitoring, disaster prediction, game entertainment and many other fields. With the development of science and technology and the progress of cognitive psychology, displaying technology has also been improved to fulfill the demand of humans, and promotes the rapid development of three-dimensional display technology. Nowadays, the visualization technology of three-dimensional terrain is a research hotspot in related fields. Through the terrain data model building, simulation and three-dimensional displaying, a variety of techniques have been used to achieve the display of three-dimensional terrain. The three-dimensional display is a technique for displaying three-dimensional images with the medium of two-dimensional plane, which can visually present the different angles and depth information of object and bring the realism close to the objective world. The effect is very similar to people's visual and cognitive habits, which makes it accepted as an ideal real three-dimensional display technology. How to realize the visualization of 3D terrain data without any special glasses or relying on electronic display devices is the research topic of this paper. In this paper, a method of combining Fourier holography with full parallax holographic stereogram is presented to realize the display of three-dimensional terrain by making full parallax hologram. Firstly, the SRTM terrain (elevation) data is processed, the three-dimensional digital model of terrain is established and then is sampled according to the principle of holographic stereogram, and thus a two-dimensional image array containing parallax information is obtained. Then, according to the holographic diffraction formula, the image transformation of two-dimensional image array is carried out to meets the requirement of Fourier holographic transform. Finally, the holographic recording optics setup is designed and the following procedures are take: laser beam is divided into object beam and reference beam, Fourier transform are involved in the procession of object beam, interference between the reference light beam and the Fourier transform image is recorded in the focus point of the objective lens, a microscopic objective with large NA is used to achieve enough view angle, images need to be recorded are displayed one at a time by a LCOS light modulator, under the position of the precision platform every unit of the hologram is recorded automatically, precisely and effectively. After post - processing, the three-dimensional topographic hologram with large view field and full parallax are accomplished. The method presented in this paper realizes the efficient automatic production of three-dimensional topographic hologram based on SRTM terrain data. Under the white light illumination, using the large-view-field and full-parallax three-dimensional hologram display, the elevation data of the terrain are displayed intuitively, accurately, clearly and delicately, which is of great significance for the research of high quality and large field holographic three-dimensional display, and has practical application value in Landform Surveying, commodity exhibition, anti-counterfeiting, advertising and so on.