## 1 Introduction  
Three-dimensional (3D) displays are mostly categorized into light-field displays [1; 2; 3] and holographic displays [4; 5; 6]. Although holographic displays are more ideal for human 3D perception than light-field displays in terms of visual fatigue, the latter can be commercialized more easily than the former to fulfill the device technology requirements. Current light-field displays suffer from a low lateral resolution and limited viewing zone. This study proposed a technique to increase the lateral resolution of a light-field display with a near-virtual-image mode, which we previously proposed [7]. In this study, we address the problem of lateral resolution, and \"resolution\" corresponds to \"lateral resolution\". The near-virtual-image-mode light-field display was proposed to provide a wide viewing zone and bright 3D images simultaneously for flat-panel-type light-field displays. Generally, flat-panel-type light-field displays have thin form factors, as they comprise flat-panel displays and lens or aperture arrays. Although the lens-array-type light-field displays present brighter 3D images than the aperture-array-type light-field displays, lens aberrations limit their viewing zone. Although the aperture-array types offer a wider viewing zone, the light loss of the aperture array limits the brightness of 3D images. The light-field display using the near-virtual-image mode employs both lens and aperture arrays to provide a larger viewing zone compared to the lens-array types and to produce brighter 3D images than the aperture-array types. However, the resolutions of its 3D images are still equal to those of the previous types. Several techniques have been proposed for increasing the resolutions of flat-panel-type light-field displays. An electronic shutter array has been integrated with a lens-array-type light-field display employing a high-speed flat-panel display to increase the resolution based on the time-multiplexing technique [8; 9]. For aperture-array-type light-field displays,techniques for replacing their static aperture arrays with dynamic ones have been proposed to increase the resolution [10; 11]. The utilization of multiple light-field displays to increase the resolution has also been proposed based on the space-multiplexing technique [12; 13]. The addition of an eye-tracking mechanism to move the viewing zones to eye positions has been proposed to increase the resolution of light-field displays [14; 15]. However, these techniques lack frame rates and feature complex systems owing to the space-multiplexing or additional devices. In a recent study, dynamic image shifting [16] and time-polarization multiplexing [17] were employed to improve the resolution of 3D images. In the lens-array-type light-field displays, there are two methods depending on the gaps between the lens array and display panel: the depth priority and resolution priority [18; 19]. In the depth-priority technique, the gap is adjusted to be equal to the focal length of the lens to suppress the divergence of light rays. The resolution-priority technique involves increasing the spatial resolution of the light-field display using real or virtual images of the elemental images. The resolution-priority technique can increase the resolution without requiring additional devices; it exploits thin flat-panel-type systems. In a recent study, the resolution-priority technique was applied to head-mounted displays, which produced virtual images several meters behind the display [20; 21] and aerial displays to present real images in front of the display [22]. The technique proposed in this study can increase the resolution of the generated 3D images by facilitating the observation of multiple pixels through each aperture of the aperture array in the near-virtual-image-mode light-field display. Previously, an electronic slit array in which the slit passes multiple pixels has been used to construct two-view autostereoscopic displays based on the time-multiplexing technique [10; 23; 24].