Lens Module Research Articles

An Accurate and Efficient User Authentication Mechanism on Smart Glasses Based on Iris Recognition

In modern society, mobile devices (such as smart phones and wearable devices) have become indispensable to almost everyone, and people store personal data in devices. Therefore, how to implement user authentication mechanism for private data protection on mobile devices is a very important issue. In this paper, an intelligent iris recognition mechanism is designed to solve the problem of user authentication in wearable smart glasses. Our contributions include hardware and software. On the hardware side, we design a set of internal infrared camera modules, including well-designed infrared light source and lens module, which is able to take clear iris images within 2~5 cm. On the software side, we propose an innovative iris segmentation algorithm which is both efficient and accurate to be used on smart glasses device. Another improvement to the traditional iris recognition is that we propose an intelligent Hamming distance (HD) threshold adaptation method which dynamically fine-tunes the HD threshold used for verification according to empirical data collected. Our final system can perform iris recognition with 66 frames per second on a smart glasses platform with 100% accuracy. As far as we know, this system is the world’s first application of iris recognition on smart glasses.

Fabrication of Infrared Filters for Three-Dimensional CMOS Image Sensor Applications

Infrared (IR) filters were developed to implement integrated three-dimensional (3D) image sensors that are capable of obtaining both color image and depth information at the same time. The combination of light filters applicable to the 3D image sensor is composed of a modified IR cut filter mounted on the objective lens module and on-chip filters such as IR pass filters and color filters. The IR cut filters were fabricated by inorganic SiO2/TiO2 multilayered thin-film deposition using RF magnetron sputtering. On-chip IR pass filters were synthetized by dissolving various pigments and dyes in organic solvents and by subsequent patterning with photolithography. The fabrication process of the filters is fairly compatible with the complementary metal oxide semiconductor (CMOS) process. Thus, the IR cut filter and IR pass filter combined with conventional color filters are considered successfully applicable to 3D image sensors.

An electro-active polymer based lens module for dynamically varying focal system

We demonstrate a polymer-based active-lens module allowing a dynamic focus controllable optical system with a wide tunable range. The active-lens module is composed of parallelized two active-lenses with a convex and a concave shaped hemispherical lens structure, respectively. Under operation with dynamic input voltage signals, each active-lens produces translational movement bi-directionally responding to a hybrid driving force that is a combination of an electro-active response of a thin dielectric elastomer membrane and an electro-static attraction force. Since the proposed active lens module widely modulates a gap-distance between lens-elements, an optical system based on the active-lens module provides widely-variable focusing for selective imaging of objects in arbitrary position.

Design methodology for a confocal imaging system using an objective microlens array with an increased working distance.

In this study, a design methodology for a multi-optical probe confocal imaging system was developed. To develop an imaging system that has the required resolving power and imaging area, this study focused on a design methodology to create a scalable and easy-to-implement confocal imaging system. This system overcomes the limitations of the optical complexities of conventional multi-optical probe confocal imaging systems and the short working distance using a micro-objective lens module composed of two microlens arrays and a telecentric relay optical system. The micro-objective lens module was fabricated on a glass substrate using backside alignment photolithography and thermal reflow processes. To test the feasibility of the developed methodology, an optical system with a resolution of 1 μm/pixel using multi-optical probes with an array size of 10 × 10 was designed and constructed. The developed system provides a 1 mm × 1 mm field of view and a sample scanning range of 100 μm. The optical resolution was evaluated by conducting sample tests using a knife-edge detecting method. The measured lateral resolution of the system was 0.98 μm.

World-smallest fiber-GRIN lens system for optofluidic applications

We have developed a new type of an optical fiber probe which integrates the standard single mode fiber with a gradient index (GRIN) microlens. The system is perfectly suited for optofluidic sensor applications since the diameter of the lens module is exactly the same as the diameter of the optical fiber. Moreover, the performance of the GRIN lens is not degraded by low contrast of the refractive index between of the lens and the fluidic environment. The GRIN lens is made with novel technology of nanostructured optics. Full Text: PDF References M. Woerdemann, C. Alpmann, M. Esseling, C. Denz, Advanced optical trapping by complex beam shaping, Laser Photonics Rev. 7, 839 (2013). CrossRef E. Weber, F. Keplinger, and M. J. Vellekoop, On-Chip Light Modulation Applying Optofluidic Principles, IEEE Sensors Journal 13 4773 (2013). CrossRef F. Hudelist, J. M. Nowosielski, R. Buczynski, A. J. Waddie, M. R. Taghizadeh, Nanostructured elliptical gradient-index microlenses, Optics Letters 35, 130 (2010) CrossRef J. M. Nowosielski, R. Buczynski, F. Hudelist, A. J. Waddie, M. R. Taghizadeh, Nanostructured GRIN microlenses for Gaussian beam focusing, Opt. Comm. 283 1938 (2010). CrossRef A.Sihvola, Electromagnetic Mixing Formulas and Applications (London: The Institution of Electrical Engineers 1999). J. Nowosielski, R. Buczynski, A. J. Waddie, A. Filipkowski, D. Pysz, A. McCarthy, R. Stepien, M. R. Taghizadeh, Large diameter nanostructured gradient index lens, Opt. Ex. 20 11767 (2012). CrossRef R. Stepien, J. Cimek, D. Pysz, I. Kujawa, M. Klimczak, R. Buczynski, Soft glasses for photonic crystal fibers and microstructured optical components, Opt. Eng. 53, 071815 (2014). CrossRef A. Filipkowski, B. Piechal, D. Pysz, R. Stepien, A. Waddie, M. R. Taghizadeh, R. Buczynski, Nanostructured gradient index microaxicons made by a modified stack and draw method, Opt. Lett. 40, 5200-5203 (2015). CrossRef

A wide-angle camera module for disposable endoscopy

A wide-angle miniaturized camera module for disposable endoscope is demonstrated in this paper. A lens module with 150° angle of view (AOV) is designed and manufactured. All plastic injection-molded lenses and a commercial CMOS image sensor are employed to reduce the manufacturing cost. The image sensor and LED illumination unit are assembled with a lens module. The camera module does not include a camera processor to further reduce its size and cost. The size of the camera module is 5.5 × 5.5 × 22.3 mm3. The diagonal field of view (FOV) of the camera module is measured to be 110°. A prototype of a disposable endoscope is implemented to perform a pre-clinical animal testing. The esophagus of an adult beagle dog is observed. These results demonstrate the feasibility of a cost-effective and high-performance camera module for disposable endoscopy.

A New Method for Appearance Quality Detection of Lens Module Based on Machine Vision

The lens module is widely used in many types of equipment, such as mobile phone, image recognition product, iPad, computer camera module, security product, car rear view module, industrial endoscope and medical endoscope product. In the process of appearance quality inspection of lens module, it is a problem that the inspection accuracy depends mainly on manual workers. To save the time and amount of this quality detection labor, it’s necessary for us to design the lens module’s appearance quality automatic inspection system. This paper proposes a subpixel-accurate edge detection algorithm based on wavelet transform with the cubic spline interpolation for the lens module’s appearance quality inspection system. Firstly, calculate the wavelet modulus maximum, and detect a pixel-accurate edge. Then apply the cubic spline interpolation to obtain subpixel-accurate edge at the side of the pixel-accurate edge. Finally, an industrial measurement method using this subpixel-accurate edge detection algorithm is studied, and some experiments are conducted to demonstrate the effectiveness of the lens module’s appearance quality inspection system. Comparing with the traditional methods, the lens module’s appearance quality inspection system has a good anti-noise performance and stable inspection accuracy.

A System and Vision Localization Method for the Opening of Railway Oil Tank Wagon Based on Shape Matching

The opening localization for railway oil tank wagon using machine vision technology is an effective way to load petroleum automatically. In this paper, we introduce a localization system for the opening of railway oil tank wagon, which consists of industrial camera, lens, LED lighter, industrial PC, and IO module. In addition, we also propose a shape matching localization method, which can overcome the adverse effects produced by illumination changes, various types of railway oil tank wagon, and various poses of camera. The shape template is extracted from a standard opening image using edge detection and shape fitting methods, which can help avoid the randomness of template selection. An optimized similarity measure is exploited to avoid the edge extraction, so that the threshold setting of edge extraction can be avoided. In addition, we also exploit scalable template to find various types opening and exploit image pyramid during shape matching procedure to gain a speedup. The indoor and outdoor experiments show that the localization system and the proposed method fully meet the requirements of practical industrial applications.

Design of an 8x Four-group Inner-focus Zoom System Using a Focus Tunable Lens

This study presents an 8x four-group inner-focus zoom lens with one-moving group for a compact camera by use of a focus tunable lens (FTL). In the initial design stage, we obtained the powers of lens groups by paraxial design based on thin lens theory, and then set up the zoom system composed of four lens modules. Instead of numerically analytic analysis for the zoom locus, we suggest simple analysis for that using lens modules optimized. After replacing four groups with equivalent thick lens modules, the power of the fourth group, which includes a focus tunable lens, is designed to be changed to fix the image plane at all positions. From this design process, we can realize an 8x four-group zoom system having one moving group by employing a focus tunable lens. The final designed zoom lens has focal lengths of 4 mm to 32 mm and apertures of F/3.5 to F/4.5 at wide and tele positions, respectively.

High-speed driving of liquid crystal lens with weakly conductive thin films and voltage booster

Liquid crystal (LC) lenses with weakly conductive thin films are known to have driving voltages of several volts, which are much smaller than those of devices without them; however, their response characteristics have not been investigated in much detail. Here, we show that low-voltage LC lenses, with the help of an overdrive pulse, can show response times of several 10 ms, which are comparable with voice coil motors currently used for focus-tuning of mobile cameras. We provide data on the lens power as well as real images captured using a lens module and a camera; we also present a compact circuit design that can boost a 3.5 V(rms) square pulse from a mobile battery to 15 V(rms). The results of this study should accelerate the use of LC lenses in mobile applications.

A smartphone-based fluorescence microscope utilizing an external phone camera lens module

We constructed a smartphone-based fluorescence microscope by adding a phone camera lens module to the outside of a smartphone camera. The external lens module forms a relay system in conjunction with the built-in phone camera. The system benefits from the small pixel size of the smartphone and other advantages associated with the phone camera lens module such as its low cost, small volume, and low weight. To realize the fluorescence microscope function, the filters and illumination source were integrated into a simple mechanical structure with a focusing adjustment scheme. Based on an image analysis, the resolution of the microscope was approximately 2.5 µm and the field of view was as large as 1.2 mm×1.2 mm. The fabricated microscope was used successfully to visualize the fluorescent paint and the low concentration quantum dots on a slide glass. The microscope obtained fluorescence images of cells stained with carboxyfluorescein succinimidyl ester (CFSE). This demonstration of a smartphone-based fluorescence microscope supports the feasibility of applications such as point-of-care diagnostic equipment based on fluorescence methods.

Methodology of quantifying curvature of Fresnel lenses and its effect on CPV module performance.

Fresnel lenses used as primary optics in concentrating photovoltaic modules may show warping produced by lens manufacturing or module assembly (e.g., stress during molding or weight load) or due to stress during operation (e.g., mismatch of thermal expansion between different materials). To quantify this problem, a simple method called "checkerboard method" is presented. The proposed method identifies shape errors on the front surface of primary lenses by analyzing the Fresnel reflections. This paper also deals with the quantification of the effects these curvatures have on their optical performance and on the electrical performance of concentrating modules incorporating them. This method can be used to perform quality control of Fresnel lenses in scenarios of high volume production.

Electrostatic Focusing Lens Module With Large Focusing Capability in Carbon Nanotube Emitter-Based X-Ray Sources

We fabricated and analyzed an electrostatic focusing lens (FL) module comprising a micro-FL with many holes near the gate and a macro-FL of single aperture toward the anode for carbon nanotube (CNT) emitter-based X-ray sources. The micro-FL suppresses the divergence of the electron beams whereas the macro-FL governs the shape of the beam bundle. The FL module can be controlled over a wide range of gate and anode voltages while maintaining the focal spot. We achieved a small focal spot of 300 $\mu \text{m}$ from CNT emitter dot arrays of 10 mm $\times 1.6$ mm with line pairs of 3 lp/mm maintained for different anode voltages.

S1210103 タブレット端末を用いた観光望遠鏡システム

A new sightseeing telescope which can be controlled by the tablets is created. The lens module includes two stepping motors to control focus and zoom. We attach a CMOS sensor to the lens module, and we use it as a UVC camera. We also create a case for the camera to control the horizontal/vertical directions of the camera. The commands from the tablets are sent to each motor via arduino, and the images from the camera can be seen on the tablet. The communications between the system and the tablet are realized by Wifi.

An ultra-wide-angle wireless camera using ultra wide band communication

A wide-angle wireless camera package using ultra wide band (UWB) communication is demonstrated in this paper. The camera is composed of a camera unit, camera processor module, UWB communication module, and power supply unit. A 162-degree lens module is developed to implement the ultra-wide-angle camera unit. All units are closely packed in a package tube with the size of ∼2 × 2 × 7 cm³ excluding an antenna. Measurements show that the camera package can transmit a high resolution video with the resolution of 2048 × 1536 (QXGA) at the frame rate of 15 fps in a MJPEG (Motion JPEG) compression mode. The camera has the maximum data transfer rate of ∼42 Mbps. The proposed camera can support ∼3X higher resolution and ∼5X higher data transfer rate than a commercial high-performance wireless camera. To the best of author's knowledge, this is the most compact wireless camera using UWB communication.

Aberration design of zoom lens systems using thick lens modules.

A systematic approach for the aberration design of a zoom lens system using a thick lens module is presented. Each component is treated as a thick lens module at the beginning of the design. A thick lens module refers to a thick lens component with a real lens structure, like lens materials, lens curvatures, lens thicknesses, and lens interval distances. All nine third-order aberrations of a thick lens component are considered during the design. The relationship of component aberrations in different zoom positions can be approximated from the aberration shift. After minimizing the aberrations of the zoom lens system, the nine third-order aberrations of every lens component can be determined. Then the thick lens structure of every lens component can be determined after optimization according to their first-order properties and third-order aberration targets. After a third optimization for minimum practical third-order aberrations of a zoom lens system, the aberration design using the thick lens module is complete, which provides a practical zoom lens system with thick lens structures. A double-sided telecentric zoom lens system is designed using the thick lens module in this paper, which shows that this method is practical for zoom lens design.

Laser-direct writing of single mode and multi-mode polymer step index waveguide structures for optical backplanes and interconnection assemblies

A laser direct writing (LDW) method is implemented as a cost efficient polymer waveguide (WG) fabrication method for prototyping large substrates for optical backplanes and optical interconnection assemblies. The LDW setup utilizes a 3-axis air-bearing motion platform to reduce WG fabrication error to within ±0.15μm. A UV laser diode coupled single mode fiber with a focusing lens module is capable of LDW WGs at both multimode (50μm) and single mode (6μm) dimensions. Correlation between LDW parameters and fabricated WG dimensions using Dow Corning® OE-4140 UV-Cured Optical Elastomer (ncore=1.5142, nclad=1.5064) is discussed theoretically and confirmed experimentally for both applications. A theoretical model is developed and utilized for producing LDW multi-mode (0.04dB/cm, λ=850nm) and single mode (0.55dB/cm, λ=1310nm) WGs. Measured propagation losses of LDW WGs are comparable to losses of photolithographic multi-mode (0.04dB/cm @ 850nm) and single mode (0.59dB/cm @ 1310nm) WG builds. LDW multi-mode and single mode WG radial bend and crossing losses are evaluated for advanced optical communication channel routing capabilities and do not exhibit significant deviations from photolithographic-manufactured WG device loss.

Aberration correction of double-sided telecentric zoom lenses using lens modules.

A systematic approach for the aberration design of a four-component double-sided telecentric zoom lens system is presented. The Gaussian structure of the zoom system is specified previously which means the powers and movements of components are known. Each component is treated as a lens module during the design stage with specified first-order properties and third-order aberration targets. The third-order aberration targets of the first component are determined by minimizing the whole aberrations of the zoom lens system using a genetic algorithm (GA). And the aberration targets of components behind are determined by reoptimization with already fixed structures of previous components. Mean pupil spherical aberration of every component in every zoom position is adopted in the objective function to control high-order aberrations. The thin lens structure of each component can be determined from their first-order properties and aberration targets. After lens thickening and reoptimization, the zoom lens system can finally be determined.

FPscope: a field-portable high-resolution microscope using a cellphone lens.

The large consumer market has made cellphone lens modules available at low-cost and in high-quality. In a conventional cellphone camera, the lens module is used to demagnify the scene onto the image plane of the camera, where image sensor is located. In this work, we report a 3D-printed high-resolution Fourier ptychographic microscope, termed FPscope, which uses a cellphone lens in a reverse manner. In our platform, we replace the image sensor with sample specimens, and use the cellphone lens to project the magnified image to the detector. To supersede the diffraction limit of the lens module, we use an LED array to illuminate the sample from different incident angles and synthesize the acquired images using the Fourier ptychographic algorithm. As a demonstration, we use the reported platform to acquire high-resolution images of resolution target and biological specimens, with a maximum synthetic numerical aperture (NA) of 0.5. We also show that, the depth-of-focus of the reported platform is about 0.1 mm, orders of magnitude longer than that of a conventional microscope objective with a similar NA. The reported platform may enable healthcare accesses in low-resource settings. It can also be used to demonstrate the concept of computational optics for educational purposes.

Kinoform diffractive lenses for efficient nano-focusing of hard X-rays.

A nano-focusing module based on two linear Fresnel zone plates is presented. The zone plates are designed to generate a kinoform phase profile in tilted geometry, thus overcoming the efficiency limitations of binary diffractive structures. Adjustment of the tilt angle enables tuning of the setup for optimal efficiency over a wide range of photon energies, ranging from 5 to 20 keV. Diffraction efficiency of more than 50% was measured for the full module at 8 keV photon energy. A diffraction limited spot size of 100 nm was verified by ptychographic reconstruction for a lens module with a large entrance aperture of 440 μm × 400 μm.