Augmented reality (AR) devices such as head-up displays (HUDs) burst into our lives, especially in the automotive industry. AR HUDs should display 3D images within a wide field of view (FoV) to bring in full immersion. However, HUDs with a wide FoV built on conventional mirror-based architecture occupy significant dashboard space and cause overheating of the display. These factors limit the integration of such wide FoV HUDs into vehicles. Instead, we propose AR HUD with a wide FoV based on a thin waveguide. A key feature of our display is the ability to deliver 3D virtual images while maintaining a small system volume. Our approach to combining both benefits is based on integrating novel units into a pupil-replication waveguide. First, a multi-view picture generation unit (MV-PGU) creates autostereoscopic 3D content within the same FoV. Then, the content is transmitted through the waveguide in a conventional pupil replication manner. Finally, a thin optical module, which we call the multi-view eyebox formation unit (MV-EFU), separates the images for the corresponding views based on the distinctive parameters. Moreover, we investigate the possibility to extend FoV by choosing the optimal parameters of the invented units. We validate our concept by raytracing simulation of a developed full-color display with an FoV of 20° × 7°. Additionally, we assemble a prototype with reduced display specifications to verify the approach experimentally.
Although head-up displays (HUDs) have already been installed in some commercial vehicles, their application to augmented reality (AR) is limited owing to the resulting narrow field of view (FoV) and fixed virtual-image distance. The matching of depth between AR information and real objects across wide FoVs is a key feature of AR HUDs to provide a safe driving experience. Meanwhile, current approaches based on the integration of two-plane virtual images and computer-generated holography suffer from problems such as partial depth control and high computational complexity, respectively, which makes them unsuitable for application in fast-moving vehicles. To bridge this gap, here, we propose a light-field-based 3D display technology with eye-tracking. We begin by matching the HUD optics with the light-field display view formation. First, we design mirrors to deliver high-quality virtual images with an FoV of 10 × 5° for a total eyebox size of 140 × 120 mm and compensate for the curved windshield shape. Next, we define the procedure to translate the driver eye position, obtained via eye-tracking, to the plane of the light-field display views. We further implement a lenticular-lens design and the corresponding sub-pixel-allocation-based rendering, for which we construct a simplified model to substitute for the freeform mirror optics. Finally, we present a prototyped device that affords the desired image quality, 3D image depth up to 100 m, and crosstalk level of <1.5%. Our findings indicate that such 3D HUDs can form the mainstream technology for AR HUDs.
A 10.1-inch 2D/3D switchable display using an integrated single light-guide plate (LGP) with a trapezoidal lightextraction (TLE) film was designed and fabricated. The integrated single LGP was composed of inverted trapezoidal line structures made by attaching a TLE film on its top surface and cylindrical lens structures on its bottom surface. The top surface of the TLE film was also bonded to the bottom surface of an LCD panel to maintain a 3D image quality, which can be seriously deteriorated by the gap variations between the LCD panel and the LGP. The inverted trapezoidal line structures act as slit apertures of parallax barriers for 3D mode. Light beams from LED light sources placed along the left and right edges of the LGP bounce between the top and bottom surfaces of the LGP, and when they collide with the inclined surfaces of the inverted trapezoidal structures, they are emitted toward the LCD panel. Light beams from LED light sources arranged on the top and bottom edges of the LGP are emitted to the lower surface while colliding with the cylindrical lens structures, and are reflected to the front surface by a reflective film for 2D mode. By applying the integrated single LGP with a TLE film, we constructed a 2D/3D switchable display prototype with a 10.1-inch tablet panel of WUXGA resolution (1,200×1,920). Consequently, we showed light-field 3D and 2D display images without interference artifacts between both modes, and also achieved luminance uniformity of over 80%. This display easily generates both 2D and 3D images without increasing the thickness and power consumption of the display device.
Future commercialization of glasses-free holographic real 3D displays requires not only appropriate image quality but also slim design of backlight unit and whole display device to match market needs. While a lot of research aimed to solve computational issues of forming Computer Generated Holograms for 3D Holographic displays, less focus on development of backlight units suitable for 3D holographic display applications with form-factor of conventional 2D display systems. Thereby, we report coherent backlight unit for 3D holographic display with thickness comparable to commercially available 2D displays (cell phones, tablets, laptops, etc.). Coherent backlight unit forms uniform, high-collimated and effective illumination of spatial light modulator. Realization of such backlight unit is possible due to holographic optical elements, based on volume gratings, constructing coherent collimated beam to illuminate display plane. Design, recording and measurement of 5.5 inch coherent backlight unit based on two holographic optical elements are presented in this paper.
To commercialize glasses-free 3D display more widely, the display device should also be able to express 2D images without image quality degradation. Moreover, the thickness of display panel including backlight unit (BLU), and the power consumption should not be increased too much, especially for mobile applications. In this paper, we present a 10.1-inch 2D-3D switchable display using an integrated single light guide plate (LGP) without increasing the thickness and power consumption. The integrated single LGP with a wedge shape is composed of prismatic line patterns on its top surface and straight bump patterns on its bottom surface. The prismatic line patterns, which are composed of micro prisms having the light aperture on one side, act as slit apertures of parallax barriers for 3D mode. The linear bump patterns arranged along the vertical direction scatter the light uniformly together with the reflective film disposed under the LGP for 2D mode. LED light sources are arranged as edge-lit in the left and right sides of the LGP for 2D mode, and on the top edge of the LGP with the wider thickness for 3D mode. Display modes can be simply switched by turning on and off the LED light sources, alternatively. Applying the integrated single LGP, we realized a 2D-3D switchable display prototype with a 10.1-inch tablet panel of WQXGA resolution (2,560 × 1,600), and showed the light-field 3D display with 27-ray mapping and 2D display. Consequently, we acquired brightness uniformity over 70% for 2D and 3D modes.
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