## 2 Methods
### Encoding Methods for the Amplitude-Modulating Device
When we prepare the intermediate function \(H_{int}(x,\,y)\), we finally obtain \(H_{MAO}(x,\,y)\) just after subtracting \(H_{int}(x,\,y)\) by its minimum [see Equation (5)]. Using the above-explained approaches, we establish the framework that consist of four different kinds of amplitude holograms, each of which is converted from the original, complex-valued hologram calculated by the FFT algorithm and is prepared for experimental comparison. Figure 5 shows the results of each encoding using the same original CGH function generated from a set of RGB and depth map images as shown in Figure 3c,d, with the MAO encoding processed under the condition of \(\varepsilon=1/50\). For the observer to experience an enhanced three-dimensional effect, two different viewpoints about a given 3D scene are required. Hence, for the dual-view holographic display, we made a set of CGH frames by selectively sorting two images per CGH frame among 1024 prepared images to provide 360\({}^{\circ}\) full views of the scene. We now explain that the viewing-point difference per CGH frame has a gap of 8 numbers from a series  
Figure 5: Four kinds of encoded holograms with FHD resolution. Encoding methods to be used are CAO encoding (a), MAO encoding (b), [PERSON]’s encoding (c), and [PERSON]’s encoding (d). of 1024 views with a time-sequential difference. For example, the first view image for the left eye and the ninth view image for the right eye can be chosen as the first CGH content for a single frame. The reason is as follows: when the radius of the circular sector, i.e., the distance between the eyes' plane and the object's plane, is 1.4 m, the arc, i.e., the average distance (BD) between the eyes, is 65 mm [21; 22], and thus their central angle should be 2.66\({}^{\circ}\). Because the central angle increment per image is 0.352\({}^{\circ}\), the view-number difference between the view of left eye and the view of right eye is equal to 8. A brief recapitulation of preparing CGH content fit with the NEHD system is as follows: (i) We obtained two complex hologram matrices through the FFT algorithm from the first set that consists of one RGB-depth image for the left eye and the other for the right eye (see Figure 6). (ii) Then we computed the four types of CGH content by using CAO, MAO, [PERSON]'s, and [PERSON]'s encoding methods. For each encoding, a pair of calculated CGHs are combined in a side-by-side arrangement and stored as an image file with a resolution of 3840 \(\times\) 1080. Figure 6 shows an exemplary process in the case of MAO encoding to prepare the first CGH frame for our dual-view holographic display. Here, we chose two sets of RGB-depth images with different viewpoints; one is for the first viewpoint and the other is for the ninth viewpoint. (iii) We repeated the above process about the 360\({}^{\circ}\) full range to create the final holographic content fit for the binocular geometry. (iv) Finally, we converted the time-sequential 360\({}^{\circ}\) views' CGH set into an uncompressed video file, which can show a holographic 3D movie with a speed of 30 frames per second (fps) [see the Supplementary video (a)-(d)]. Figure 6: Process to prepare CGH content of a frame fit for the dual-view holographic display made up of two AM SLMs.