The Gabor superlens as an alternative wafer-level camera approach inspired by superposition compound eyes of nocturnal insects

Incoherent diffractive optical elements for extendable field-of-view imaging

We present a diffractive optics design for incoherent imaging with an extendable field-of-view. In our design method, multiple layers of diffractive optical elements (DOEs) are synthesized so that images on the input plane illuminated with spatially incoherent light are reproduced upright on the output plane. In addition, our method removes the need for an approximation of shift invariance, which has been assumed in conventional optical designs for incoherent imaging systems. Once the DOE cascade is calculated, the field-of-view can be extended by using an array of such DOEs without further calculation. We derive the optical condition to calculate the DOEs and numerically demonstrate the proposed method with the condition.

Diffractive lensless imaging with optimized Voronoi-Fresnel phase

Lensless cameras are a class of imaging devices that shrink the physical dimensions to the very close vicinity of the image sensor by replacing conventional compound lenses with integrated flat optics and computational algorithms. Here we report a diffractive lensless camera with spatially-coded Voronoi-Fresnel phase to achieve superior image quality. We propose a design principle of maximizing the acquired information in optics to facilitate the computational reconstruction. By introducing an easy-to-optimize Fourier domain metric, Modulation Transfer Function volume (MTFv), which is related to the Strehl ratio, we devise an optimization framework to guide the optimization of the diffractive optical element. The resulting Voronoi-Fresnel phase features an irregular array of quasi-Centroidal Voronoi cells containing a base first-order Fresnel phase function. We demonstrate and verify the imaging performance for photography applications with a prototype Voronoi-Fresnel lensless camera on a 1.6-megapixel image sensor in various illumination conditions. Results show that the proposed design outperforms existing lensless cameras, and could benefit the development of compact imaging systems that work in extreme physical conditions.

A wide-field and high-resolution lensless compound eye microsystem for real-time target motion perception

Optical measurement systems suffer from a fundamental tradeoff between the field of view (FOV), the resolution and the update rate. A compound eye has the advantages of a wide FOV, high update rate and high sensitivity to motion, providing inspiration for breaking through the constraint and realizing high-performance optical systems. However, most existing studies on artificial compound eyes are limited by complex structure and low resolution, and they focus on imaging instead of precise measurement. Here, a high-performance lensless compound eye microsystem is developed to realize target motion perception through precise and fast orientation measurement. The microsystem splices multiple sub-FOVs formed by long-focal subeyes, images targets distributed in a panoramic range into a single multiplexing image sensor, and codes the subeye aperture array for distinguishing the targets from different sub-FOVs. A wide-field and high resolution are simultaneously realized in a simple and easy-to-manufacture microelectromechanical system (MEMS) aperture array. Moreover, based on the electronic rolling shutter technique of the image sensor, a hyperframe update rate is achieved by the precise measurement of multiple time-shifted spots of one target. The microsystem achieves an orientation measurement accuracy of 0.0023° (3σ) in the x direction and 0.0028° (3σ) in the y direction in a cone FOV of 120° with an update rate ~20 times higher than the frame rate. This study provides a promising approach for achieving optical measurements with comprehensive high performance and may have great significance in various applications, such as vision-controlled directional navigation and high-dynamic target tracking, formation and obstacle avoidance of unmanned aerial vehicles.

A bio-inspired polarization navigation sensor based on artificial compound eyes

Insect compound eyes are optical systems with small volume and a compact structure. The ommatidia in the dorsal rim area of some insects have polarized vision, which can perceive the polarization pattern of the sky and provide them with navigation information. In this paper, inspired by the polarization-sensitive compound eyes of insects, a bio-inspired polarization navigation sensor based on artificial compound eyes is designed. The sensor consists of an artificial compound eye, an integrated polarization detector and an integrated circuit. The optical path of the sensor uses the lens defocus method, which can ensure that the sensor obtains redundant polarization information. The integrated polarization detector is used to obtain the polarization information of the incident light, and the integrated circuit is responsible for the calculation. To extract effective information from images, we propose a multi-threshold segmentation method to filter and classify effective pixels. We use the least squares method to fit the inherent error of the sensor and then compensate it. The indoor calibration accuracy of the sensor is ±0.3°, and the outdoor calibration accuracy is ±0.5°. The sensor can provide accurate direction information for general smart mobile devices. The size of the sensor is 4 × 4 × 2 cm, and the weight is only 15 g. The key components of the sensor can be mass-produced, and it is a miniaturized and low-cost polarization navigation sensor.

Automotive Holographic Head-Up Displays

Driver's access to information about navigation and vehicle data through in-car displays and personal devices distract the driver from safe vehicle management. The discrepancy between road safety and infotainment must be addressed to develop safely operated modern vehicles. Head-up displays (HUDs) aim to introduce a seamless uptake of visual information for the driver while securely operating a vehicle. HUDs projected on the windshield provide the driver with visual navigation and vehicle data within the comfort of the driver's personal eye box through a customizable extended display space. Windshield HUDs do not require the driver to shift the gaze away from the road to attain road information. This article presents a review of technological advances and future perspectives in holographic HUDs by analyzing the optoelectronics devices and the user experience of the driver. The review elucidates holographic displays and full augmented reality in 3D with depth perception when projecting the visual information on the road within the driver's gaze. Design factors, functionality, and the integration of personalized machine learning technologies into holographic HUDs are discussed. Application examples of the display technologies regarding road safety and security are presented. An outlook is provided to reflect on display trends and autonomous driving.

Artificial Compound Eye Systems and Their Application: A Review

The natural compound eye system has many outstanding properties, such as a more compact size, wider-angle view, better capacity to detect moving objects, and higher sensitivity to light intensity, compared to that of a single-aperture vision system. Thanks to the development of micro- and nano-fabrication techniques, many artificial compound eye imaging systems have been studied and fabricated to inherit fascinating optical features of the natural compound eye. This paper provides a review of artificial compound eye imaging systems. This review begins by introducing the principle of the natural compound eye, and then, the analysis of two types of artificial compound eye systems. We equally present the applications of the artificial compound eye imaging systems. Finally, we suggest our outlooks about the artificial compound eye imaging system.

Biomimetic curved compound-eye camera with a high resolution for the detection of distant moving objects

In this Letter, we demonstrate the design and fabrication of a biomimetic curved compound-eye camera (BCCEC) with a high resolution for detecting distant moving objects purpose. In contrast to previously reported compound-eye cameras, our BCCEC has two distinct features. One is that the ommatidia of the compound eye are deployed on a curved surface which makes a large field of view (FOV) possible. The other is that each ommatidium has a relatively large optical entrance and long focal length so that a distant object can be imaged. To overcome the mismatch between the curved focal plane formed by the curved compound eye and the planar focal plane of the CMOS image sensor (CIS), an optical relay subsystem is introduced between the compound eye and the CIS. As a result, a BCCEC with 127 ommatidia in the compound eye is designed and fabricated to achieve a large FOV of up to 98^∘×98^∘. The experimental results show that objects with a size of 100 mm can be clearly resolved at a distance of 25 m. The capture of the motion trajectories of a moving object is also demonstrated, which makes it possible to detect and track the moving targets in a huge FOV for security surveillance purposes.

Biologically inspired artificial eyes and photonics

Natural visual systems have inspired scientists and engineers to mimic their intriguing features for the development of advanced photonic devices that can provide better solutions than conventional ones. Among various kinds of natural eyes, researchers have had intensive interest in mammal eyes and compound eyes due to their advantages in optical properties such as focal length tunability, high-resolution imaging, light intensity modulation, wide field of view, high light sensitivity, and efficient light management. A variety of different approaches in the broad field of science and technology have been tried and succeeded to duplicate the functions of natural eyes and develop bioinspired photonic devices for various applications. In this review, we present a comprehensive overview of bioinspired artificial eyes and photonic devices that mimic functions of natural eyes. After we briefly introduce visual systems in nature, we discuss optical components inspired by the mammal eyes, including tunable lenses actuated with different mechanisms, curved image sensors with low aberration, and light intensity modulators. Next, compound eye inspired photonic devices are presented, such as microlenses and micromirror arrays, imaging sensor arrays on curved surfaces, self-written waveguides with microlens arrays, and antireflective nanostructures (ARS). Subsequently, compound eyes with focal length tunability, photosensitivity enhancers, and polarization imaging sensors are described.

Biologically inspired ultrathin arrayed camera for high-contrast and high-resolution imaging

Compound eyes found in insects provide intriguing sources of biological inspiration for miniaturised imaging systems. Here, we report an ultrathin arrayed camera inspired by insect eye structures for high-contrast and super-resolution imaging. The ultrathin camera features micro-optical elements (MOEs), i.e., inverted microlenses, multilayered pinhole arrays, and gap spacers on an image sensor. The MOE was fabricated by using repeated photolithography and thermal reflow. The fully packaged camera shows a total track length of 740 μm and a field-of-view (FOV) of 73°. The experimental results demonstrate that the multilayered pinhole of the MOE allows high-contrast imaging by eliminating the optical crosstalk between microlenses. The integral image reconstructed from array images clearly increases the modulation transfer function (MTF) by ~1.57 times compared to that of a single channel image in the ultrathin camera. This ultrathin arrayed camera provides a novel and practical direction for diverse mobile, surveillance or medical applications.

Review of state-of-the-art artificial compound eye imaging systems

The natural compound eye has received much attention in recent years due to its remarkable properties, such as its large field of view (FOV), compact structure, and high sensitivity to moving objects. Many studies have been devoted to mimicking the imaging system of the natural compound eye. The paper gives a review of state-of-the-art artificial compound eye imaging systems. Firstly, we introduce the imaging principle of three types of natural compound eye. Then, we divide current artificial compound eye imaging systems into four categories according to the difference of structural composition. Readers can easily grasp methods to build an artificial compound eye imaging system from the perspective of structural composition. Moreover, we compare the imaging performance of state-of-the-art artificial compound eye imaging systems, which provides a reference for readers to design system parameters of an artificial compound eye imaging system. Next, we present the applications of the artificial compound eye imaging system including imaging with a large FOV, imaging with high resolution, object distance detection, medical imaging, egomotion estimation, and navigation. Finally, an outlook of the artificial compound eye imaging system is highlighted.

Insect-Mimetic Imaging System Based on a Microlens Array Fabricated by a Patterned-Layer Integrating Soft Lithography Process

In nature, arthropods have evolved to utilize a multiaperture vision system with a micro-optical structure which has advantages, such as compact size and wide-angle view, compared to that of a single-aperture vision system. In this paper, we present a multiaperture imaging system using a microlens array fabricated by a patterned-layer integrating soft lithography (PLISL) process which is based on a molding technique that can transfer three-dimensional structures and a gold screening layer simultaneously. The imaging system consists of a microlens array, a lens-adjusting jig, and a conventional (charge-coupled device) CCD image sensor. The microlens array has a light screening layer patterned among all the microlenses by the PLISL process to prevent light interference. The three-dimensionally printed jig adjusts the microlens array on the conventional CCD sensor for the focused image. The manufactured imaging system has a thin optic system and a large field-of-view of 100 degrees. The developed imaging system takes multiple images at once. To show its possible applications, multiple depth plane images were reconstructed based on the taken subimages with a single shot.

Compact multichannel infrared camera integrated in an operational detector dewar cooler assembly

We present an ultracompact infrared cryogenic camera integrated inside a standard Sofradir's detector dewar cooler assembly (DDCA) whose field of view is equal to 120°. The multichannel optical architecture produces four nonredundant images on a single SCORPIO detector with a pixel pitch of 15 μm. This ultraminiaturized optical system brings a very low additional optical and mechanical mass to be cooled in the DDCA: the cool-down time is comparable to an equivalent DDCA without an imagery function. Limiting the number of channels is necessary to keep the highest number of resolved points in the final image. However, optical tolerances lead to irregular shifts between the channels. This paper discusses the limits of multichannel architectures. With an image-processing algorithm, the four images produced by the camera are combined to process a single full-resolution image with an equivalent sampling pitch equal to 7.5 μm. Experimental measurements on the modulation transfer function and noise equivalent temperature difference show that this camera achieves good optical performance.

Xenos peckii vision inspires an ultrathin digital camera

Increased demand for compact devices leads to rapid development of miniaturized digital cameras. However, conventional camera modules contain multiple lenses along the optical axis to compensate for optical aberrations that introduce technical challenges in reducing the total thickness of the camera module. Here, we report an ultrathin digital camera inspired by the vision principle of Xenos peckii, an endoparasite of paper wasps. The male Xenos peckii has an unusual visual system that exhibits distinct benefits for high resolution and high sensitivity, unlike the compound eyes found in most insects and some crustaceans. The biologically inspired camera features a sandwiched configuration of concave microprisms, microlenses, and pinhole arrays on a flat image sensor. The camera shows a field-of-view (FOV) of 68 degrees with a diameter of 3.4 mm and a total track length of 1.4 mm. The biologically inspired camera offers a new opportunity for developing ultrathin cameras in medical, industrial, and military fields.

Design and simulation of a superposition compound eye system based on hybrid diffractive-refractive lenses

Compound eyes offer a promising field of miniaturized imaging systems. In one application of a compound eye, superposition of compound eye systems forms a composite image by superposing the images produced by different channels. The geometric configuration of superposition compound eye systems is achieved by three micro-lens arrays with different pitches and focal lengths. High resolution is indispensable for the practicability of superposition compound eye systems. In this paper, hybrid diffractive-refractive lenses are introduced into the design of a compound eye system for this purpose. With the help of ZEMAX, two superposition compound eye systems with and without hybrid diffractive-refractive lenses were separately designed. Then, we demonstrate the effectiveness of using a hybrid diffractive-refractive lens to improve the image quality.

Compound eye and retina-like combination sensor with a large field of view based on a space-variant curved micro lens array

A compound eye and retina-like combination sensor based on a space-variant curved micro lens array (CMLA) is proposed to simultaneously offer the large FOV characteristic of a compound eye and retina-like feature of a single aperture eye. The mathematical models of the sensor are developed and the structure parameters of the space-variant CMLA are deduced. Modeling verification is carried out and the results show that the whole field of view (FOV) of the sensor is 105° and the optical information loss rate is 0.06 when the sector is 32. Imaging simulations illustrate that the sensor possesses the retina-like property, i.e., logarithmic-polar transformation. Meanwhile, the simulation results indicate that the overlapping angles between the two micro lenses on the adjacent rings can be reduced by decreasing the rings and the blind radius, and increasing the sectors. This work is beneficial for large FOV and time-efficient applications.

Compact near-eye display system using a superlens-based microlens array magnifier

A new type of very compact optical element for a near-eye display (NED) that uses a pair of microlens arrays (MLAs) is presented. The MLA pair works in conjunction to form a magnifier (collimator). The purpose of this is to aid in the accommodation of the eye on a head-up display that is positioned within several centimeters from the eye; the MLA pair collimates the light rays departing from the display thereby generating a virtual image of the display at optical infinity. By using the MLA pair, we are able to make a collimator that retains a thin profile of about 2 mm in thickness with a system focal length of about 7 mm.

Compact multi-aperture imaging with high angular resolution

Previous reports have demonstrated that it is possible to emulate the imaging function of a single conventional lens with an N×N array of identical lenslets to provide an N-fold reduction in imaging-system track length. This approach limits the application to low-resolution imaging. We highlight how using an array of dissimilar lenslets, with an array width that can be much wider than the detector array, high-resolution super-resolved imaging is possible. We illustrate this approach with a ray-traced design and optimization of a long-wave infrared system employing a 3×3 array of freeform lenslets to provide a fourfold reduction in track length compared to a baseline system. Simulations of image recovery show that recovered image quality is comparable to that of the baseline system.

Seidel aberrations of the Gabor superlens

Equations are presented for the third-order Seidel aberrations of the Gabor superlens (GSL) as a function of microtelescope channel position within the aperture array. To reveal the origin and form of increasing aberration with channel height, Seidel coefficients are derived as a function of the accumulating pitch difference between the lens arrays and the aberrations present in the centered channel. Two- and three-element Gabor lenses are investigated and their aberrations are expressed as a function of first-order design parameters. The derived theory is then compared to a real ray trace simulation to demonstrate the accuracy of third-order aberration theory to predict GSL image quality.

Development of a low cost high precision three-layer 3D artificial compound eye

Artificial compound eyes are typically designed on planar substrates due to the limits of current imaging devices and available manufacturing processes. In this study, a high precision, low cost, three-layer 3D artificial compound eye consisting of a 3D microlens array, a freeform lens array, and a field lens array was constructed to mimic an apposition compound eye on a curved substrate. The freeform microlens array was manufactured on a curved substrate to alter incident light beams and steer their respective images onto a flat image plane. The optical design was performed using ZEMAX. The optical simulation shows that the artificial compound eye can form multiple images with aberrations below 11 μm; adequate for many imaging applications. Both the freeform lens array and the field lens array were manufactured using microinjection molding process to reduce cost. Aluminum mold inserts were diamond machined by the slow tool servo method. The performance of the compound eye was tested using a home-built optical setup. The images captured demonstrate that the proposed structures can successfully steer images from a curved surface onto a planar photoreceptor. Experimental results show that the compound eye in this research has a field of view of 87°. In addition, images formed by multiple channels were found to be evenly distributed on the flat photoreceptor. Additionally, overlapping views of the adjacent channels allow higher resolution images to be re-constructed from multiple 3D images taken simultaneously.

Computational superposition compound eye imaging for extended depth-of-field and field-of-view

This paper describes a superposition compound eye imaging system for extending the depth-of-field (DOF) and the field-of-view (FOV) using a spherical array of erect imaging optics and deconvolution processing. This imaging system had a three-dimensionally space-invariant point spread function generated by the superposition optics. A sharp image with a deep DOF and a wide FOV could be reconstructed by deconvolution processing with a single filter from a single captured image. The properties of the proposed system were confirmed by ray-trace simulations.

Compact infrared cryogenic wafer-level camera: design and experimental validation

We present a compact infrared cryogenic multichannel camera with a wide field of view equal to 120°. By merging the optics with the detector, the concept is compatible with both cryogenic constraints and wafer-level fabrication. The design strategy of such a camera is described, as well as its fabrication and integration process. Its characterization has been carried out in terms of the modulation transfer function and the noise equivalent temperature difference (NETD). The optical system is limited by the diffraction. By cooling the optics, we achieve a very low NETD equal to 15 mK compared with traditional infrared cameras. A postprocessing algorithm that aims at reconstructing a well-sampled image from the set of undersampled raw subimages produced by the camera is proposed and validated on experimental images.

Applications of advanced hybrid organic-inorganic nanomaterials: from laboratory to market

Today cross-cutting approaches, where molecular engineering and clever processing are synergistically coupled, allow the chemist to tailor complex hybrid systems of various shapes with perfect mastery at different size scales, composition, functionality, and morphology. Hybrid materials with organic-inorganic or bio-inorganic character represent not only a new field of basic research but also, via their remarkable new properties and multifunctional nature, hybrids offer prospects for many new applications in extremely diverse fields. The description and discussion of the major applications of hybrid inorganic-organic (or biologic) materials are the major topic of this critical review. Indeed, today the very large set of accessible hybrid materials span a wide spectrum of properties which yield the emergence of innovative industrial applications in various domains such as optics, micro-electronics, transportation, health, energy, housing, and the environment among others (526 references).