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.
Proc. SPIE. 9685, 8th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems; and Smart Structures and Materials
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.
In this paper, a quite effective method is proposed for designing the diffractive optical element (DOE) to generate a pattern with large diffraction angle. Through analyze the difference between the non-paraxial Rayleigh Sommerfeld integral and the paraxial Fraunhofer diffraction integral, we modify the desired output intensity distribution with coordinate transformation and intensity adjustment. Then the paraxial Fraunhofer diffraction integral can be used to design the DOE, which adopts the fast-Fourier-transform (FFT) algorithm to accelerate the computation. To verify our method, the simulation and the experiments are taken. And the result shows that our method can effectively rectify the pillow distortion and can achieve the exact diffraction angle.
This paper presents an approach used to fabricate resonant subwavelength grating based on thiol-ene material. First of all, polydimethylsiloxane soft imprint stamp with opposite structure of the subwavelength grating master mold is made by casting. Then, the desired subwavelength grating with UV-curable thiol-ene material grating structure is fabricated using the polydimethylsioxane soft stamp by UV-curable soft-lithography. Here, we fabricate a subwavelength grating with period of 300nm using the approach, which could reflect blue light with wavelength ranging from 448nm to 482nm at a specific angle and presents the excellent resonant characteristic. The experimental results are consistent with the simulation results, demonstrating that the approach proposed in this paper could effectively fabricate the thiol-ene material resonant subwavelength grating structure. The thiol-ene material 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. The fabrication technique in this paper is simple, low-cost, and easy to high throughput, which has broad application prospects in the preparation of micro and nano structures.
Integral imaging system with soft substrate is proposed and fabricated by lithographic method. The integral imaging
system consists of microlens array and micro-image array. Based on the optical design theory, the geometrical
parameters of the microlens array and micro-image array is calculated and simulated by the software Tracepro.
Furthermore, some experiments are carried out. The microlens array and micro-image array is fabricated on
Polyethylene Terephthalate substrate by lithographic method. After the alignment between the microlens array and the
micro-image array, three dimensional image can be formed over the microlens array. The imaging system is easy to
curve and can be used on some static displays, such as three dimensional display, three dimensional picture and so on.
High performance infrared polarizer with broad band is required for various infrared applications. The conventional infrared polarizer, based on the birefringence effect of natural crystal, is cost-consuming in fabrication and can hardly be integrated into micro-optical systems due to its large bulk. In this paper, an infrared polarizer is proposed in the spectrum from 3 to 19 μm based on sub-wavelength metal wire grid. The dependence of the performance on some key parameters, including metal materials, geometrical parameters, has been deeply investigated by using the Finite-Difference Time-Domain (FDTD) method. The results show that Au wire-grids have a higher transmittance for the Transverse Magnetic（TM） mode light than that of other metal materials, and both the grid period and the grid thickness have important impact on the performance. Based on these observations, a polarizer has been designed by choosing the optimal value of related parameters. Numerical simulation suggests that the designed infrared wire grid polarizer have advantages of broad band, high TM polarization transmission efficiencies and high extinction ratios. The transmission efficiencies of TM polarization are larger than 59.3%, and the extinction ratios range from 28.6 to 44.6 dB in that range of the spectrum.
Polymer optical elements have widely been investigated because of their low cost and simple fabrication. Currently, UV-curable epoxy resins have been become general polymer materials for optical elements. However, they are still limited by their intrinsic properties, such as a relatively low rate of polymerization and high formulation viscosity. This paper proposed and demonstrated a rapid UV-curable process for polymer optical elements fabrication based on a UV-curable and low-viscosity thiol-ene composition. Several optical elements, including one-dimensional gratings with a 10-um period, Dammann Gratings and microlens arrays (100μm lens diameter), were fabricated by the UV-curable thiol-ene composition and their optical properties were examined in detail.
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.
With the rapid development of science and technology, optical imaging system has been widely used, and the
performance requirements are getting higher and higher such as lighter weight, smaller size, larger field of view and
more sensitive to the moving targets. With the advantages of large field of view, high agility and multi-channels,
compound eye is more and more concerned by academia and industry. In this work, an artificial spherical compound eye
imaging system is proposed, which is formed by several mini cameras to get a large field of view. By analyzing the
relationship of the view field between every single camera and the whole system, the geometric arrangement of cameras
is studied and the compound eye structure is designed. By using the precision machining technology, the system can be
manufactured. To verify the performance of this system, experiments were carried out, where the compound eye was
formed by seven mini cameras which were placed centripetally along a spherical surface so that each camera points in a
different direction. Pictures taken by these cameras were mosaiced into a complete image with large field of view. The
results of the experiments prove the validity of the design method and the fabrication technology. By increasing the
number of the cameras, larger view field even panoramic imaging can be realized by using this artificial compound eye.
Novel antireflective surfaces with silica particles arranged regularly and tightly are proposed and fabricated by self
assemble silica nanoparticle through electrostatic attraction between charged colloidal particles and charged
polyelectrolyte multilayer. Due to regularly arrangement of the particles, the nanoparticle coatings, as homogeneous
porous layers with uniform distribution, show high-quality and uniform antireflective capability in each region on the
substrate. It has been sufficiently demonstrated in our experiments. Furthermore, the relations among the antireflective
capability, average size of nanoparticles, and incident angle of the irradiated light are calculated by finite-difference
time-domain method. It is demonstrated that the nanostructure coatings with particles of 100 nm size possess the
excellently suitable performance for reflection/transmission with respect to visible-light region. From the results, the
fabricated anti-reflective nanostructures have great potential to improve the efficiency of optoelectronic devices such as a
photo-detector and solar cells.
An axicon structured lens is designed and its properties of long focal depth is demonstrated. The phase function of the axicon structured lens is constructed according to the properties of nondiffractive Bessel beam with uniform-intensity. Based on the relationship of the side length of the square hole and the phase retardation, the required phase distribution of the axicon structured lens with a long focal depth in a metallic film can be determined. To verify the feasibility of the method, an axicon structured lens with focal length 1000 mm, a focal depth larger than 20 mm was designed and the intensity distribution of far field was calculated. The results show that the focal depth is 25 mm which is nearly 7 times extended with nearly diffraction-limited image quality.
A compound-eye imaging system has been proposed in which the microlenses arranged in a convex solid substrate are
designed for satisfying the requirement of both a large field of view and a flat receiving plane. Based on the geometrical
optics, the formulas are established for determining the parameters of the microlens in the different positions so that the
focal spots of the microlens array can properly be settled on a flat plane. With the method, ray tracing is carried out for
simulating the focusing process of the compound-eye imaging system. The results show that the focal spots distributed
on a plane are achieved and the field of view of the system can be up to 60°.
A projection photolithography method is presented in the paper, which can be used for fabricating continuous surface
structure with the aperture of a few micrometers. In the method, a microlens array is used to form minified images of a
designed object. When the parameters of the microlens and the object are properly determined, images with minification
from hundreds to thousands times can be obtained. Photoresist is used to record the images and patterns with micro or
sub-micro critical size could be manufactured. Both geometric and diffraction theory are used for optimizing the
parameters and the design process is given. Resist reflow method is used in our experiment for achieving microlens array
with the characteristics of a large NA and a small period. The micro-taper array with period 20 μm and aperture of 5 μm
was manufactured with the method and the home made microlens array photolithographic system.