Design and fabrication of square micro-lens array for integral imaging 3D display

Zhang

et al. 2023

J Soc Info Display

Due to the limitation of traditional microlens arrays (MLAs) in integral imaging display, the depth of field (DOF) is restricted in space and the center depth plane is difficult to extend in a large range. Here, we propose a microfabrication method based on bifocal MLAs to improve DOF. The bifocal MLAs for extended DOF were fabricated by using two‐step photolithography and thermal reflow. This method allows diverse microlenses of high to low numerical aperture to achieve high spatial resolution as well as accurate depth estimation. Microlenses of different focal lengths were simultaneously deposited on a substrate by repeated photolithography with multiple photomasks with alignment mark to define micro‐posts of different thicknesses. Hexagonally packaged bifocal MLAs clearly show the DOF extended from 0.004 to 4.908 mm for 57.6 μm in lens diameter, and their corresponding object distance ranges from 0.125 to 0.165 mm. Based on the proposed scheme, this method provides potential applications in integral imaging 3D display or light field display.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Enhanced depth of field of integral imaging display using bifocal microlens array fabricated by two‐step lithography

Zhang

et al. 2023

J Soc Info Display

“…[1][2][3][4][5] Thus, like the basic II technique, the quality of 3D visualization of the target object is determined by the MLAs specification, such as its numerical aperture (NA), focal length and pitch. [6][7][8] Commonly available II system have a fixed image plane position due to the focal length is invariable, which may lead to the dizziness and visual fatigue with long-time use [9][10] . Generally, a depth priority II display system that can provide reconstructed image with large DOF.…”

Section: Introductionmentioning

confidence: 99%

29.5: Enhanced depth of field of integral imaging display using bifocal microlens array fabricated by two‐step lithography

Symp Digest of Tech Papers

Zhang

et al. 2022

Due to the limitation of traditional microlens arrays (MLAs) in integral imaging display, the depth of field (DOF) is restricted in space and the center depth plane are difficult to extended in a large range. Here we propose a microfabrication method based on bifocal MLAs to improve DOF. The bifocal MLAs for extended DOF was fabricated by using two‐step photolithography and thermal reflow. This method allows diverse microlenses of high to low numerical aperture to achieve high spatial resolution as well as accurate depth estimation. Microlenses of different focal lengths were simultaneously deposited on a substrate by repeated photolithography with multiple photomasks with alignment mark to define micro‐posts of different thicknesses. Hexagonally packaged bifocal MLAs clearly show the DOF extended from 0.004 mm to 4.908 mm for 57.6 �m in lens diameter and their corresponding object distance ranges from 0.125 mm to 0. 165 mm. Based on the proposed scheme, this method provides potential applications in integral imaging 3D display or light field display.

“…On the other hand, curved displays are now quickly overtaking flat monitors among discerning users, due to a number of benefits unique to their design, including enhanced sense of immersion, wider field of view and reduced eyes strain 6,[33][34][35] . The realization of curved integral imaging 3D display not only have great application potentials, but also provide referential values to flexible 3D displays when they are under deformation 36,37 .…”

mentioning

confidence: 99%

Large-scale microlens arrays on flexible substrate with improved numerical aperture for curved integral imaging 3D display

Chen

Weng

et al. 2020

Sci Rep

Curved integral imaging 3D display could provide enhanced 3D sense of immersion and wider viewing angle, and is gaining increasing interest among discerning users. In this work, large scale microlens arrays (MLAs) on flexible PMMA substrate were achieved based on screen printing method. Meanwhile, an inverted reflowing configuration as well as optimization of UV resin's viscosity and substrate's surface wettability were implemented to improved the numerical aperture (NA) of microlenses. The results showed that the NA values of MLAs could be increased effectively by adopting inverted reflowing manner with appropriate reflowing time. With decreasing the substrate's wettability, the NA values could be increased from 0.036 to 0.096, when the UV resin contact angles increased from 60.1° to 88.7°. For demonstration, the fabricated MLAs was combined to a curved 2D monitor to realize a 31-inch curved integral imaging 3D display system, exhibiting wider viewing angle than flat integral imaging 3D display system. Display technology will develop in the direction of more natural vision and more user-friendly. In the past two decades, considerable attention has been paid to extend the classical two-dimensional (2D) displays into their three-dimensional (3D) counterparts because of its stronger sense of reality 1-4. Another important research stream is flexible display, which has thin, lightweight and non-breakable characteristics. Displays with flexible form factors enable the fabrication of displays on curvilinear surfaces and allow their shapes to be transformed, providing potential applications to mobile, wearable and vehicle display. Therefore, flexible 3D displays become a major technological and application goal in the field of next-generation displays. Integral imaging is an autostereoscopic and multiscopic 3D display technology that uses double micro-lens arrays (MLAs) to capture and reproduce a light field of the target based on reversibility principle of light rays 5. It is regarded as a promising approach to realize the 3D display system due to its typical characteristics, such as glasses free, full parallax, quasi-continuous view points, eliminating visual fatigue and real 3D display. In particular, it produces real concentrations of light to optically produce 3D images that are observed without decoupling the convergence and the accommodation, avoiding the detrimental effects of the convergence-accommodation conflict. Thus, there has been substantially increasing interest in researching and implementing effective technologies for the capture, processing, and display of 3D images 6-8. It is also inferred that flexible integral imaging 3D displays could be achieved via the combination of flexible 2D display panel and flexible MLAs 9-11. MLAs have been widely used as key components in lots of optical systems 12-14 , such as integral imaging 15,16 , optical communications 17 , digital display 18 , detection 19 and far field imaging 20. In particular, MLAs with good converging performance, great uniformity of focusing...