Multi-distance phase retrieval represents a computational imaging technique that synergizes a basic imaging setup with computational post-processing. This method involves capturing diffraction intensity at distinct distances, enabling the iterative reconstruction of the target's wavefront by incorporating the intensity patterns into the relevant algorithm. Despite the advantages of lensless imaging through multi-distance phase retrieval, including its uncomplicated setup, expansive field of view, and freedom from aberrations, challenges persist in terms of sluggish convergence and limited resolution. To address these concerns, the presented paper introduces enhancements to both the imaging system and the algorithm. This dual approach contributes to a remarkable 5.88 times acceleration in convergence speed, all achieved without the need for supplementary equipment. Moreover, a substantial enhancement in imaging quality is achieved when compared to the conventional method.
KEYWORDS: 3D image processing, 3D acquisition, Image processing, Microlens array, Cameras, Microlens, Imaging technologies, Imaging systems, 3D modeling, 3D applications
The traditional imaging method can only obtain the two-dimensional information of the object space in lateral resolution through a single exposure, but cannot obtain the longitudinal depth information. The depth information of the object space will be lost because the object cannot be reconstructed in three dimensions. The light field imaging technology enables reconstruction of three-dimensional objects by means of adding microlens arrays into a conventional camera system. The technology has a wide range of applications in medical, military, and entertainment. In this paper, a light field acquisition technology using microlens based on 3ds Max is proposed. A 3D object model was established using 3ds Max. By establishing a virtual microlens array, the crosstalk-free, high resolution and fast acquisition of the light field image by the microlens can be realized. Simulation study of the light field imaging technology can provide a highefficiency computational study. The acquired images are processed to reconstruct images from different perspectives. Finally, the light field imaging experiments based on microlens arrays is carried out to realize the image reconstruction in different perspective images. Reliability of the algorithm is verified.
Bionic compound eye optical element composed of multi-dimensional sub-eye microlenses plays an important role in miniaturizing the volume and weight of an imaging system. In this manuscript, we present a novel structure of the bionic compound eye with multiple focal lengths. By the division of the microlens into two concentric radial zones including the inner zone and the outer zone with independent radius, the sub-eye which is a multi-level micro-scale structure can be formed with multiple focal lengths. The imaging capability of the structure has been simulated. The results show that the optical information in different depths can be acquired by the structure. Meanwhile, the parameters including aperture and radius of the two zones, which have an influence on the imaging quality have been analyzed and discussed. With the increasing of the ratio of inner and outer aperture, the imaging quality of the inner zone is becoming better, and instead the outer zone will become worse. In addition, through controlling the radius of the inner and outer zone independently, the design of sub-eye with different focal lengths can be realized. With the difference between the radius of the inner and outer zone becoming larger, the imaging resolution of the sub-eye will decrease. Therefore, the optimization of the multifocal structure should be carried out according to the actual imaging quality demands. Meanwhile, this study can provide references for the further applications of multifocal microlens in bionic compound eye.
The high-precision fabrication of micro-/nano-structure is a challenge. In this paper, we proposed a new fabrication method of high-precision structure based on an etching resistance layer. The high-precision features were fabricated by photolithography technique, followed by the etching process to transfer the features to the substrate. During this process, the etching uniformity and error lead to the feature distortion. We introduced an etching resistance layer between feature layer and substrate. The etching process will stop when arriving at the resistance layer. Due to the high precision of the plating film, the high-precision structure depth was achieved. In our experiment, we introduced aluminum trioxide as the etching resistance layer. The structures with low depth error of less than 5% were fabricated.
According to the exposure pattern distortion in contact printing caused by the photoresist and sometimes has a rough surface with impurity particles on it, we propose a new flexible hybrid mask for contact printing. The mask consists of three layers: a flexible polymer buffer layer, a polymer structure layer of high Young's modulus, and a metal masking layer. Because the hybrid mask skillfully combines the characteristics of flexible polymer and high Young's modulus polymer, it has two advantages: high flexibility and high resolution. The flexible hybrid mask can attach closely with the photoresist under the condition of vacuum adsorption. So the fabrication of micro-nano structures with high precision and high resolution can be realized. In this paper, a new flexible hybrid mask with critical dimension of 2um was fabricated. The photoresist structure with high precision was manufactured using this mask by photolithography and it verified the feasibility of the mask for lithography.
With the advantages of small structure and high efficiency, the diffractive element is widely used in the construction of a structured light 3D measurement system. But the working wavelength of diffraction element is single, and the light field generated by the diffraction element is only one channel. We make the original single channel into three channels, so as to achieve from the serial algorithm to parallel algorithm to improve the measurement speed. Based on the lattice light field and the design method of multi wavelength diffraction elements, and in the premise of ensuring the number of points, the traditional lattice points of light field are divided into three channels. These channels are regarded as the target fields, and the diffraction element for generating color structure light field is designed.
This paper demonstrates an approach to fabricate nano-pillar based on thiol-ene via soft-lithography. The template is anodic aluminum oxygen (AAO) with ordered nano-holes with the diameter of 90nm.The nano-pillar consists of rigid thiol-ene features on an elastic poly(dimethylsiloxane) (PDMS) support. It is capable of patterning both flat and curved substrate. The thiol-ene is a new green UV-curable polymer material, including a number of advantages such as rapid UV-curing in the natural environment, low-cost, high resolution, and regulative performance characteristic. Here, we fabricated a two-layer structure, which included rigid thiol-ene nano-pillar with sub-100nm resolution and soft PDMS substrate. The experiment results show that this approach can be used to fabricate high-resolution features and the thiol-ene is an excellent imprint material. The fabrication technique in this paper is simple, low-cost, high-resolution and easy to high throughput, which has broad application prospects in the preparation of nanostructures.
Biological inspiration has produced some successful solutions for different imaging systems. Inspired by the compound eye of insects, this paper presents some image process techniques used in the spherical compound eye imaging system. By analyzing the relationship between the system with large field of view (FOV) and each lens, an imaging system based on compound eyes has been designed, where 37 lenses pointing in different directions are arranged on a spherical substrate. By researching the relationship between the lens position and the corresponding image geometrical shape to realize a large FOV detection, the image process technique is proposed. To verify the technique, experiments are carried out based on the designed compound eye imaging system. The results show that an image with FOV over 166° can be acquired while keeping excellent image process quality.
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