Large field-of-view synthetic aperture holography using rotation stages

In general, digital holography means a technology to measure an object wave by using a focal plane array (FPA) sensor. Since the limitation of the dimension of the FPA sensor, the field of view obtained by the FPA sensor is usually very narrow. Many methods have been proposed to increase the field of view of measurement. One simple solution is the synthesis of the holograms with small apertures, where each of them is measured by the FPA sensor respectively. If we imagine specific applications such as 360-degree table-top digital holographic display, the large field of view of the object is required to present the three-dimensional contents to the observer who may change his position dynamically. In this paper, we use two-axis rotation stage for acquisition of the object wave with large field of view. In our system, the optics including a laser and a CCD sensor are fixed and the object is mounted on the rotation stage. During the rotation of the object, the holograms are taken sequentially and the object wave over the hemispherical surface in k-space is obtained. The increase of solid angle of the measured hologram means the increase of acquired angular spectrum of interested objects. The resolution of the measurement is closely related with the numerical aperture and the data with fine resolution is expectable. But since it is not easy to match the relative phases of the each hologram, unfortunately the enhancement of the resolution in the reconstructed object wave is negligible.