## 2 Methods
### Optical Components for the NHD System  
We discuss optical components for the near-eye holographic display system, for which a schematic architecture is illustrated in Figure 2a. Collimated light from the green laser with 532 nm wavelength (CNI optoelectronics, MGL-S-532) is generated by using a first positive lens located just after the fiber-coupled laser source as a coherent illumination. To upload holographic 3D content, a flat LCoS-SLM panel that modulates an 8-bit grey-scaled amplitude is modified as a direct-viewing SLM type. First, the polarization direction of the illuminating light is parallel to that of a transparent, film-typed PBS (polarizing beam splitter), which is positioned at the input surface of the LCoS. Second, near the surface of the SLM, a second convex lens called a field lens is placed against the SLM to converge the output light toward the eye box of the observer. The active area of the LCoS-SLM is 12.1 mm (V) \(\times\) 6.80 mm (H). It supports a pixel arrangement of a nearly rectangular-shaped matrix geometry. This pixel geometry generates an extension of the zeroth diffraction order in the Fourier plane, i.e., a virtual observation window (WW), which corresponds to the area of the eye box of the observer [10; 16; 17]. The size of VW along the \(i\)-axis (\(i=x,y\)) is approximately given by \(W_{i}=\lambda(f/p_{i})\), where \(p_{i}\) is the pixel pitch of the SLM along the \(i\)-axis, \(f\) the focal length of the field lens, which is also related to the viewing distance of the observer from the SLM, and \(\lambda\) the wavelength of illumination light. The size of the wavelength-dependent VW is designed to become larger than the pupil size of the human eye [18; 19; 20]. Thus, \(f=500\) mm is chosen for \(\lambda=532\) nm to obtain \(W_{x}=42.2\) mm (along the horizontal direction) and \(W_{y}=42.2\) mm (along the vertical direction). The optical wave field emerging from a 3D object or scene can be directly observed within the region of VW with the help of both the transparent PBS film and the field lens, thus leading to holographic augmented reality (AR), enabling the viewer to experience genuine depth cues and an accommodation effect. Further, optical observation and an experimental evaluation of the optically reconstructed holographic 3D (H3D) images are performed near the area of VW at the eye position (see Figure 2a) and demonstrated by a camera-captured, holographic 3D (H3D) scene reconstructed from CGHs. As shown in Figure 2, the proposed near-eye holographic 3D display (NEHD) system consists of two split main components so that binocular observation can be achieved; after a collimated beam is split into two parts, its left-side part is designed to focus an incident beam towards the left-eye and the other part towards the right-eye.  
Passing through each SLM, the light wave fields then are guided into two independent focal points corresponding to the two eyes' observational positions. The separation between these two positions is equal to 65 mm in the eye plane of the observer, where the distance corresponds to the average binocular distance of a human [21; 22] and is indicated as a binocular distance (BD) in Figure 2a.