A Meniscus Multifocusing Compound Eye Camera Based on Negative Pressure Forming Technology.

To meet the challenge of preparing a high-resolution compound eye, this paper proposes a multi-focal-length meniscus compound eye based on MEMS negative pressure molding technology. The aperture is increased, a large field of view angle of 101.14° is obtained, and the ommatidia radius of each stage is gradually increased from 250 µm to 440 µm. A meniscus structure is used to improve the imaging quality of the marginal compound eye so that its resolution can reach 36.00 lp/mm. The prepared microlenses have a uniform shape and a smooth surface, and both panoramic image stitching and moving object tracking are achieved. This technology has great potential for application in many fields, including automatic driving, machine vision, and medical endoscopy.

Double-Glued Multi-Focal Bionic Compound Eye Camera.

Compound eye cameras are a vital component of bionics. Compound eye lenses are currently used in light field cameras, monitoring imaging, medical endoscopes, and other fields. However, the resolution of the compound eye lens is still low at the moment, which has an impact on the application scene. Photolithography and negative pressure molding were used to create a double-glued multi-focal bionic compound eye camera in this study. The compound eye camera has 83 microlenses, with ommatidium diameters ranging from 400 µm to 660 µm, and a 92.3 degree field-of-view angle. The double-gluing structure significantly improves the optical performance of the compound eye lens, and the spatial resolution of the ommatidium is 57.00 lp mm-1. Additionally, the measurement of speed is investigated. This double-glue compound eye camera has numerous potential applications in the military, machine vision, and other fields.

Design and Integration of the Single-Lens Curved Multi-Focusing Compound Eye Camera.

Compared with a traditional optical system, the single-lens curved compound eye imaging system has superior optical performance, such as a large field of view (FOV), small size, and high portability. However, defocus and low resolution hinder the further development of single-lens curved compound eye imaging systems. In this study, the design of a nonuniform curved compound eye with multiple focal lengths was used to solve the defocus problem. A two-step gas-assisted process, which was combined with photolithography, soft photolithography, and ultraviolet curing, was proposed for fabricating the ommatidia with a large numerical aperture precisely. Ommatidia with high resolution were fabricated and arranged in five rings. Based on the imaging experimental results, it was demonstrated that the high-resolution and small-volume single-lens curved compound eye imaging system has significant advantages in large-field imaging and rapid recognition.

High-Identical Numerical Aperture, Multifocal Microlens Array through Single-Step Multi-Sized Hole Patterning Photolithography.

Imaging applications based on microlens arrays (MLAs) have a great potential for the depth sensor, wide field-of-view camera and the reconstructed hologram. However, the narrow depth-of-field remains the challenge for accurate, reliable depth estimation. Multifocal microlens array (Mf-MLAs) is perceived as a major breakthrough, but existing fabrication methods are still hindered by the expensive, low-throughput, and dissimilar numerical aperture (NA) of individual lenses due to the multiple steps in the photolithography process. This paper reports the fabrication method of high NA, Mf-MLAs for the extended depth-of-field using single-step photolithography assisted by chemical wet etching. The various lens parameters of Mf-MLAs are manipulated by the multi-sized hole photomask and the wet etch time. Theoretical and experimental results show that the Mf-MLAs have three types of lens with different focal lengths, while maintaining the uniform and high NA irrespective of the lens type. Additionally, we demonstrate the multi-focal plane image acquisition via Mf-MLAs integrated into a microscope.

Fabrication and Characterization of Curved Compound Eyes Based on Multifocal Microlenses.

Curved compound eyes have generated great interest owing to the wide field of view but the application of devices is hindered for the lack of proper detectors. One-lens curved compound eyes with multi-focal microlenses provide a solution for wide field imaging integrated in a commercial photo-detector. However, it is still a challenge for manufacturing this kind of compound eye. In this paper, a rapid and accurate method is proposed by a combination of photolithography, hot embossing, soft photolithography, and gas-assisted deformation techniques. Microlens arrays with different focal lengths were firstly obtained on a polymer, and then the planar structure was converted to the curved surface. A total of 581 compound eyes with diameters ranging from 152.8 µm to 240.9 µm were successfully obtained on one curved surface within a few hours, and the field of view of the compound eyes exceeded 108°. To verify the characteristics of the fabricated compound eyes, morphology deviation was measured by a probe profile and a scanning electron microscope. The optical performance and imaging capability were also tested and analyzed. As a result, the ommatidia made up of microlenses showed not only high accuracy in morphology, but also imaging uniformity on a focal plane. This flexible massive fabrication of compound eyes indicates great potential for miniaturized imaging systems.