In 3D displays based on parallax barriers, active parallax barriers that can change the barrier pattern according to the viewing position have been proposed to expand the viewing area. However, the production cost increases because the active barrier requires a special LC panel. Therefore, to lower the cost, we propose a glasses-free stereoscopic display using an active parallax barrier of an LC panel with the same specifications as the image LC panel. The ideal image pattern cannot be formed because the minimum control unit of the LC panel is equal to one subpixel. However, by using an image cycle pitch method (ICPM) that periodically increases the horizontal pitch of one pair of binocular images by one subpixel, we can realize the ideal relationship between the average pitch of the binocular image and the barrier pitch. In our previous research, we could make the average pitch match to the ideal pitch on the discrete optimum viewing distances (OVDs), but we could not follow the viewing position between the discrete OVDs. In this paper, we propose the ICPM that can keep the stereoscopic vision even at any viewing position. In order to verify the effectiveness of the proposed method, we made the prototype displays and evaluated them. As a result, we showed the crosstalk ratio could be suppressed low over a very wide range by using the proposed method. Also, we confirmed we could obtain the stereoscopic vision at the viewing distance from 300 mm to 729 mm by a subjective evaluation.
We have previously proposed eye tracking system to expand viewing area in all directions for glasses-free 3D display. In this system, since the parallax barrier was fixed, the viewing zone was expanded by image processing corresponding to the viewing position. Thus, there was a limit to expanding the viewing zone only by image processing. On the other hand, we can expand the viewing zone by applying an active barrier that changes to the optimum barrier pattern corresponding to the viewing position by eye tracking. However, to change the active barrier pattern, complex calculation and a specially designed active barrier LC panel are required. To overcome this problem, we propose a novel control method to expand the viewing zone of stereoscopic 3D displays with active parallax barrier in depth direction. The proposed method is the combination of the simple generation method of a barrier pattern and the synthesis method of Left/Right synthetic image corresponding to the viewing position. In this method, let the optimum barrier pitch be Bp at the viewing distance d, we set the barrier pitch to x*Bp and synthesize the Left/Right image so that crosstalk is low at the same time at the viewing distance d/x. To verify the effectiveness of the proposed method, we measured the crosstalk of the prototype 3D display. The crosstalk ratios at the optimum viewing distance 1092 mm (d), 774 mm (d*3/4) and 546 mm (d*1/2) were 4.28%, 3.82% and 5.02%, respectively. Therefore, low crosstalk 3D images could be observed.
In the stereoscopic 3D display using the parallax barrier, the active barrier method can expand the viewing area if the barrier pattern optimizes corresponding to the position of the observer by eye tracking. However, requiring not only the LC display panel but also the specially shaped LC panel for the active barrier, this system should be very expensive. We propose using the active barrier which is a monochromatic panel of the same pixel shape as the image display panel. In the proposed method, it is easy to manufacture panels for the active barrier, and the 3D display provide the wide viewing area and high quality 3D images for observers. When the active barrier is a monochromatic panel having the same pixel shape as the image display panel, basically the barrier pitch cannot realize the ideal value. Thus, the observer cannot observe the stereoscopic image in the full screen. In order to realize stereoscopic observation, we apply the cycle pitch composing the stereoscopic image. The cycle pitch composing the stereoscopic image is the method to bring the pitch constituting the L/R image closer to the ideal value by periodically increasing the number of dots constituting the L/R image. To confirm the effectiveness of the proposed method, the crosstalk of the prototypes using film barriers were measured. Crosstalk was less than or equal to 10% at the viewing distance of 421 mm to 1238 mm. That crosstalk can be reduced regardless of observation distance was confirmed.
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