As a structure composed of two-dimensional arrays of microlensing, Microlens Array (MLA) has attracted the attention of academia and industry due to its outstanding optical properties and wide applications. Recently, MLA has gradually stepped into diverse application areas, such as wave front sensing, virtual/augmented reality display, beamforming, small/wide angle imaging, light field camera, optical communication and many other emerging applications.
However, with traditional MLA manufacturing methods, such as hot reflow, inkjet and self assembly, it is difficult to directly fabricate the matrix of aspheric microlensing lenses (AMLA) with the desired arrangement and profile, which determines the optical performance of AMLA. Meanwhile, obstacles, such as debris from top-down writing, difficulties in controlling the terrain and the complexity of the process, hinder these methods from commercializing on a large scale.
In a new paper published in Light: advanced manufacturinga team of scientists led by Professor Chengqun Gui from State Key Advanced Lithography Laboratory, Institute of Technology Science, Wuhan University, Wuhan, and colleagues demonstrated the fabrication and characterization of AMLA via DLWL single-beam exposure, which can meet the high requirements for optical performance.
To control the profile, an optimization method was used in our study to reduce the deviation of the AMLA profile from the desired profile. Parallel and scattered light sources were used to test the different optical performances of AMLA, and the results are in good agreement with our design. Due to the high flexibility of our approach, AMLA with different filling agents and AMLA can also be fabricated off-axis using one-step photolithography. Finally, a flexible thin-film automatic stereoscopic display is prepared using the above technology, which shows a new way to provide flexible 3D display at low cost.
Compared with traditional MLA fabrication methods, this advanced optical lithography technology is of high design flexibility, which can greatly improve the performance of many functional MLA-based devices. These scholars summarize the advantage and application of this advanced lithographic technology:
We display AMLA with dimensions of 30 x 30 mm2 Can be manufactured within 8 hours and 36 minutes, consistent with high-speed writing exceeding 100mm2/ h. In fact, we can manufacture MLA with an area larger than 500 x 500mm2Meanwhile, the synthetic AMLA profile was successfully optimized by 3D optical proximity correction (profile relative deviation of up to 0.28%) and the surface roughness was less than 6 nm on average. “
“It has many application prospects, such as a laser beamformer and wavefront sensor. For example, to achieve a free beam shape, microlenses within the MLA must be aligned irregularly (for example, focused spot arrays are randomly distributed), which It requires a complex grayscale mask for use in other methods. Using direct-write laser lithography technology with a high degree of fabrication freedom, we can directly fabricate off-axis MLA to create irregular spot arrays without the need for a complex grayscale mask,” they added.
“The proposed AMLA fabrication method based on direct laser-write lithography can not only reduce the difficulty of preparing the complex morphology of MLAs, but is also very suitable for industrial production. This may significantly reduce the cost of preparing devices composed of microlens, such as endoscopes, microlensing devices, etc. infrared detection, holographic screens, optical couplers, etc., therefore, it will have a great impact on The medical treatmentrescue, visual communications, military and many other related fields.”
Shiyi Luan et al, High-speed, large-area, high-resolution fabrication of an aspherical micro-lens array based on 12-bit direct laser lithography, Light: advanced manufacturing (2022). DOI: 10.37188 / lam.2022.047
Chinese Academy of Sciences
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