Hexagonal Lens Array Research Articles

Imaging quality characterization and optimization of segmented planar imaging system based on honeycomb dense azimuth sampling lens array.

Segmented planar photoelectric imaging is an advanced computational imaging technology that utilizes photonic integrated circuits (PICs) to achieve the miniaturization of imaging systems. The original radial-spoke lens array has dense radial sampling and coarse azimuthal sampling. The sparsity and inhomogeneity of spatial frequency sampling lead to the loss of spatial frequency information and blurred reconstructed images. In this paper, a honeycomb dense azimuth sampling lens array is proposed, and three baseline pairing methods are designed, which can realize dense azimuth sampling, effectively increase spatial frequency sampling and improve the imaging quality. The signal transmission model of the segmented planar imaging system is established and the imaging process is simulated and analyzed. The simulation results show that the honeycomb lens array improves the azimuth sampling density and spatial frequency coverage, and its imaging quality is significantly improved compared with the hexagonal lens array and the radial-spoke lens array. Furthermore, the optimal choice of the baseline pairing method and the error range of the fill factor and are also given in this paper. The results indicate that the mixed pairing method first ensures low and medium-frequency dense sampling, and then increases high-frequency sampling, which makes the imaging results better than those of the other two baseline pairing methods in terms of image contour, contrast and image detail information. The sampling density of the spatial frequency and the imaging quality can be improved by increasing the fill factor. In the actual manufacturing process, the allowable error range of the fill factor of the lens array is within 5%. The research results will provide theoretical support for the design and development of segmented planar imaging system.

Fast tool servo-based ultra-precision diamond sculpturing for fabricating micro-structured surfaces

To eliminate differences in surface quality and improve the machining flexibility of micro-structured surfaces, this paper proposes a novel ultra-precision diamond sculpturing method based on a triaxial fast tool servo (FTS). In this method, the diamond tool is directly driven by the FTS rather than the ultra-precision lathe to fabricate the micro-structure surfaces. The corresponding toolpath generation algorithm is established to take full advantage of the triaxial FTS. The toolpath is first generated through traditional calculating the shortest tool edge projection on the desired surface and the curve interpolation. The overshoot around the path corner is predicted by simulating the tracking path. Then an extended path is added to the original toolpath to stabilize the overshoot before removing the material. The simulation indicates that the hexagonal lens array can be favorably fabricated by the proposed ultra-precision diamond sculpturing method, and the developed toolpath reduces the form error from 20 to 5nm. The sculpturing experiments of sinusoidal micro-structure array and micro-lens array surfaces suggest that their actual peak-to-valley (PV) form errors are 70nm and 50nm, respectively. The single lens with the surface roughness Sa 3.44nm can be precisely fabricated in 0.1s, demonstrating the high machining efficiency and high machining quality of the proposed ultra-precision diamond sculpturing method.

A microfluidically controlled concave\u2013convex membrane lens using an addressing operation system

Electrical control toolkits for microlens arrays are available to some extent, but for applications in environments with strong electromagnetic fields, radiation, or deep water, non-electrical actuation and control strategies are more appropriate. An integrated digital microfluidic zoom actuating unit with a logic addressing unit for a built-in membrane lens array, e.g., a flexible bionic compound eye, is developed and studied in this article. A concave–convex membrane fluidic microvalve, which is the component element of the logic gate, actuator, and microlens, is proposed to replace the traditional solenoid valve. The functions of pressure regulation and decoding can be obtained by incorporating microvalves into fluidic networks according to equivalent circuit designs. The zoom actuating unit contains a pressure regulator to adjust the focal length of lenses with three levels, and the logic addressing unit contains a decoder to choose a typical lens from a hexagonal lens array. The microfluidic chip control system is connected flexibly to the actuating part, a membrane lens array. It is shown from a simulation and experimental demonstration that the designed and fabricated system, which is composed of a whole microfluidic zoom unit, addressing technology, and a microlens array, works well. Because these components are constructed in the same fabrication process and operate with the same work media and driving source, the system can be made highly compatible and lightweight for applications such as human-machine interfaces and soft robots.

Advanced 360-Degree Integral-Floating Display Using a Hidden Point Removal Operator and a Hexagonal Lens Array

An enhanced 360-degree integral-floating three-dimensional display system using a hexagonal lens array and a hidden point removal operator is proposed. Only the visible points of the chosen three-dimensional point cloud model are detected by the hidden point removal operator for each rotating step of the anamorphic optics system, and elemental image arrays are generated for the detected visible points from the corresponding viewpoint. Each elemental image of the elemental image array is generated by a hexagonal grid, due to being captured through a hexagonal lens array. The hidden point removal operator eliminates the overlap problem of points in front and behind, and the hexagonal lens array captures the elemental image arrays with more accurate approximation, so in the end the quality of the displayed image is improved. In an experiment, an anamorphic-optics-system-based 360-degree integral-floating display with improved image quality is demonstrated.

Feasibility study of hidden flow imaging based on laser speckle technique using multiperspectives contrast images

This paper demonstrates the insertion of lens array in the front of a CCD camera in a laser speckle imaging (LSI) like-technique to acquire multiple speckle reflectance projections for imaging blood flow in an intact biological tissue. In some of LSI applications, flow imaging is obtained by thinning or removing of the upper tissue layers to access blood vessels. In contrast, with the proposed approach flow imaging can be achieved while the tissue is intact. In the system, each lens from an hexagonal lens array observed the sample from slightly different perspectives and captured with a CCD camera. In the computer, these multiview raw images are converted to speckled contrast maps. Then, a self-deconvolution shift-and-add algorithm is employed for processing yields high contrast flow information. The method is experimentally validated first with a plastic tube filled with scattering liquid running at different controlled flow rates hidden in a biological tissue and then extensively tested for imaging of cerebral blood flow in an intact rodent head experience different conditions. A total of fifteen mice were used in the experiments divided randomly into three groups as follows: Group 1 (n=5) consisted of injured mice experience hypoxic ischemic brain injury monitored for ~40min. Group 2 (n=5) injured mice experience anoxic brain injury monitored up to 20min. Group 3 (n=5) experience functional activation monitored up to ~35min. To increase tissue transparency and the penetration depth of photons through head tissue layers, an optical clearing method was employed. To our knowledge, this work presents for the first time the use of lens array in LSI scheme.

Real-time 3D display system based on computer-generated integral imaging technique using enhanced ISPP for hexagonal lens array

This paper proposes an open computer language (OpenCL) parallel processing method to generate the elemental image arrays (EIAs) for hexagonal lens array from a three-dimensional (3D) object such as a volume data. Hexagonal lens array has a higher fill factor compared to the rectangular lens array case; however, each pixel of an elemental image should be determined to belong to the single hexagonal lens. Therefore, generation for the entire EIA requires very large computations. The proposed method reduces processing time for the EIAs for a given hexagonal lens array. By using the proposed image space parallel processing (ISPP) method, it can enhance the processing speed that generates the 3D display of real-time interactive integral imaging for hexagonal lens array. In our experiment, we implemented the EIAs for hexagonal lens array in real-time and obtained a good processing time for a large of volume data for multiple cases of lens arrays.

육각형 렌즈 어레이로부터 요소영상을 생성하기 위한 병렬 처리 기법

대부분 집적영상 기법에서는 사각형 렌즈 어레이가 사용되고 있으며, 이로 인해 집적된 빛의 분포는 사각격자 형태로 기록된다. 그러나 육각형 렌즈 어레이를 사용하면, 사각형 렌즈 어레이보다 더 높은 밀도의 빛의 분포와 이상적인 원형 렌즈에 가깝게 이미지를 기록 또는 재생 할 수 있다[4]. 육각형 렌즈 어레이 요소영상을 병렬 처리 기법을 사용하여 생성하기 위해서는 요소영상을 구성하는 각 화소에 대하여 그 화소가 속할 육각형 렌즈를 결정해야하고, 이 과정은 화면에 출력되는 모든 화소에 대하여 진행 되며 많은 계산량이 요구된다. 본 논문에서는 3D 볼륨 데이터를 사용하여 육각형 렌즈 어레이에 대한 요소영상을 생성하기 위해 OpenCL를 사용한 병렬 처리 기법을 제안한다. 제안 된 방법을 위한 실험에는 Male [<TEX>$128{\times}256{\times}256$</TEX>화소] 볼륨데이터를 사용하였으며, 실험 결과 <TEX>$20{\times}20$</TEX>개의 육각형 렌즈 어레이에 대해 요소영상을 초당 20~60장 생성할 수 있었다. According that most integral imaging techniques have used rectangular lens array, this integrated distribution of light is recorded in the form of a rectangular grid. However, hexagonal lens array gives a more accurate approximation of ideal circular lens and provides higher pickup/display density than rectangular lens array[4]. Using the parallel processing technique in order to generate the elemental imaging for hexagonal lens array, each pixel that compose the elemental imaging should be determined to belong to the hexagonal lens. This process is output to the screen for every pixel in progress, and many computations are required. In this paper, we have proposed parallel processing method using an OpenCL to generate the elemental imaging for hexagonal lens array in 3D volume date. In the experimental result of proposed method show speed of 20~60 fps for hexagonal lens array of <TEX>$20{\times}20$</TEX> sizes and input data of Male[<TEX>$128{\times}256{\times}256$</TEX>] volume data.

Resolution comparison between integral-imaging-based hologram synthesis methods using rectangular and hexagonal lens arrays

We compare the resolution of the hologram reconstruction synthesis methods based on integral imaging using rectangular and hexagonal lens arrays. By using a hexagonal lens array instead of conventional rectangular lens array, the three-dimensional objects are sampled with hexagonal grids. Due to more efficient sampling of the hexagonal grid, the resolution of the reconstructed object is higher compared with the case of using rectangular lens array. We analyze the resolution enhancement of the hologram reconstruction quantitatively and verify it experimentally.