Proceedings Volume 10376

Novel Optical Systems Design and Optimization XX

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Proceedings Volume 10376

Novel Optical Systems Design and Optimization XX

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Volume Details

Date Published: 7 December 2017
Contents: 9 Sessions, 26 Papers, 18 Presentations
Conference: SPIE Optical Engineering + Applications 2017
Volume Number: 10376

Table of Contents

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Table of Contents

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  • Front Matter: Volume 10376
  • Optical Engineering Plenary Session
  • Exotic and Unconventional Optics and Systems
  • Multi- and Hyperspectral Applications
  • Novel Systems
  • Biomedical Applications and Human Factors
  • Volumetric Displays and 3D Imaging
  • Metrology and Inspection Systems
  • Poster Session
Front Matter: Volume 10376
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Front Matter: Volume 10376
This PDF file contains the front matter associated with SPIE Proceedings Volume 10376, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.
Optical Engineering Plenary Session
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Designing for one to one-million: how production quantities influence design (Conference Presentation)
One of the most significant factors in product design is the production quantity. Along with unit price, it determines what is possible and what is prudent in allocating resources to the engineering, to the tooling, and to the material costs. From the extreme of producing one or two units to the other extreme of producing over a million units, these trade-offs are discussed in the context of optical and photonic systems. These trade-offs are illustrated using examples of products produced for the capital equipment and consumer electronics markets covering the gamut of production quantities with particular attention given to optical components.
Exotic and Unconventional Optics and Systems
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Curved sensors for compact high-resolution wide field designs
Christophe Gaschet, Bertrand Chambion, Stéphane Gétin, et al.
Over the recent years, a huge interest has grown for curved electronics, particularly for opto-electronics systems. Indeed, curved sensors help the correction of off-axis aberrations, such as Petzval Field Curvature and astigmatism. In this paper, we describe benefits of curvature and tunable curvature on an existing fish-eye lens. We proposed a new design architecture, compact and with a high resolution, developed specifically for a curved image sensor. We discuss about aberrations and effect of higher sensor curvature on third order aberrations. Besides, we show results of sensors’ mechanical limits and its electro-optical characterization. Finally, all these experiments and optical results demonstrate the feasibility and high performances of systems with curved sensors.
Focus-induced photoresponse: a fundamentally novel approach to optical distance measurements (Conference Presentation)
Christoph Lungenschmied, Oili Pekkola, Christian Lennartz, et al.
Focus-Induced Photoresponse (FIP) is a patented monocular technology for optical distance measurements [1]. It relies on physical phenomena which are fundamentally different from established technologies such as time-of-flight, stereo vision, structured light or systems based on image processing. In this presentation, the underlying principles of the technology as well as application examples are introduced. FIP exploits the nonlinear transient photoresponse of various organic as well as inorganic semiconductors when exposed to optical radiation. When a light-emitting (or reflecting) object moves in and out of focus, the size of the image that it creates on a sensor surface determines the magnitude of the photoresponse. As the focal point shifts with the distance between the collecting lens and the object, the sensor response yields a unique signature for every distance. The device layout can hence be simple: the main components are modulated light sources, a lens and a non-pixelated sensor. Due to the unstructured sensor, resolution is not restricted by pixel size. FIP does not require large computational power as neither image processing nor stereo vision is required. By proper choice of optics and sensor type, the system can be adapted to any measuring task. We have successfully demonstrated functionality for wavelengths from visible light to IR and for distances up to 100 m. [1] Bruder et al. (US 9,001,029 B2) DETECTOR FOR OPTICALLY DETECTING AT LEAST ONE OBJECT.
Ideal-lens stars
Jakub Bĕlín, Tomáš Tyc, Stephen Oxburgh, et al.
We recently showed how structures of ideal (thin) lenses can act as (ray-optical) transformation-optics devices. This was done by breaking the structure down into all sets of ideal lenses in the structure that share a common edge, and showing that these sets have very specific imaging properties. In order to start the development of a general understanding of the imaging properties of sets of ideal lenses that share a common edge, we investigate here particularly simple and symmetric examples of combinations of ideal lenses that share a common edge. We call these combinations ideal-lens stars. An ideal-lens star is formed by N identical ideal lenses, each placed such that they share a principal point (which lies on the common edge) and such that the angles between all neighbouring lenses are the same. We find that that passage through every single ideal lens in the ideal-lens star images any point to itself. Furthermore, light-ray trajectories in ideal-lens stars are piecewise linear approximations to conic sections. (In the limit of N approaching infinity, they are conic sections.)
High-speed video analysis of ballistic trials to investigate the crack propagation in glass laminates
Arash Ramezani, Hendrik Rothe
Since computers and software have spread into all fields of industry, extensive efforts are currently made in order to improve the safety by applying certain numerical solutions. For many engineering problems involving shock and impact, there is no single ideal numerical method that can reproduce the various regimes of a problem. This paper presents a set of numerical simulations of ballistic tests, which analyze the effects of soda lime glass laminates, familiarly known as transparent armor. Transparent armor is one of the most critical components in the protection of light armored vehicles. The goal is to find an appropriate solver technique for simulating brittle materials and thereby improve bullet-proof glass to meet current challenges. To have the correct material model available is not enough. In this work, the main solver technologies are compared to create a perfect simulation model for soda lime glass laminates. The calculation should match ballistic trials and be used as the basis for further studies. In view of the complexity of penetration processes, it is not surprising that the bulk of work in this area is experimental in nature. Terminal ballistic test techniques, aside from routine proof tests, vary mainly in the degree of instrumentation provided and hence the amount of data retrieved. Here, the ballistic trials and the methods of analysis are discussed in detail. The numerical simulations are performed with the nonlinear dynamic analysis computer code ANSYS AUTODYN
Imaging with pairs of skew lenses
Jakub Bělín, Stephen Oxburgh, Tomáš Tyc, et al.
Many of the properties of thick lenses can be understood by considering these as a combination of parallel ideal thin lenses that share a common optical axis. A similar analysis can also be applied to many other optical systems. Consequently, combinations of ideal lenses that share a common optical axis, or at least optical-axis direction, are very well understood. Such combinations can be described as a single lens with principal planes that do not coincide. However, in recent proposals for lens-based transformation-optics devices the lenses do not share an optical-axis direction. To understand such lens-based transformation-optics devices, combinations of lenses with skew optical axes must be understood. In complete analogy to the description of combinations of pairs of ideal lenses that share an optical axis, we describe here pairs of ideal lenses with skew optical axes as a single ideal lens with sheared object and image spaces. The transverse planes are no longer perpendicular to the optical axis. We construct the optical axis, the direction of the transverse planes on both sides, and all cardinal points. We believe that this construction has the potential to become a powerful tool for understanding and designing novel optical devices.
Multi- and Hyperspectral Applications
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Temporal focal plane filter arrays (Conference Presentation)
We recently defined a new formalism for engineering spatial information channels for focal plane filter arrays (FPFAs) in a general way for any physical light property measured via irradiance including spectral bands, polarimetric bands, and general coherence. The formalism encompasses color filter arrays, micropolarizer arrays, and microantenna arrays over a pixelated irradiance sensor. The formalism derives the physical channels available from the parameters of the unit cell used to tile the focal plane array: the unit cell geometry, the filter transmission functions, the number of unit cells, and the unit cell filter weights. We also recently showed that switching the polarization measuring properties in time over a fixed micropolarizer array would perform well compared with snapshot systems, even given increased noise due to doubling the temporal framerate. We present preliminary results on the extension of our FPFA framework to include temporal effects. Instead of a 2D unit cell which completely defines the system channels, a 3D unit cell consisting of 3D attenuation functions on a 3D rectangular lattice in (x,y,t) is defined, and specific examples are shown for micropolarizer array systems with a ferroelectric variable retarder; and a color filter array system utilizing tunable etalons for color filter modulation.
Aberrations of temporally modulated optical wavefronts in dispersive optical systems
Classical time-invariant lens aberrations, and methods for correcting them, are well known in the art. However, the design, analysis, and construction of optical components and systems for temporally modulated optical wavefronts–and in particular, wavefronts in optical time-of-flight or phase measurement instruments, such as laser trackers, heterodyne laser interferometers, and spherical retroreflectors, require additional considerations to correct for what will be called Optical Amplitude Modulation (OAM) aberrations. Ray tracing analysis is time-invariant and thus insensitive to temporal modulation of the rays. Secondary considerations must be given to the wavefront of the modulated envelope which is focused on a detector, i.e., while the rays converge to a focus, the phase of the modulated envelope will in general depend on the path of the rays. Elements from communications theory, including amplitude modulation (AM) and analysis in the Fourier transform frequency domain are unified with classical optics, where the optical wavelength of a laser is treated as a carrier signal and the AM produces two slightly offset sidebands. The sidebands produce the OAM aberration due to dispersion and different paths through the optical elements. Suggestions are made for methods for correcting OAM aberrations, such as lens designs that are achromatic at the two sidebands, the use of specific materials matched to the carrier wavelength, the use of corrector plates, and computer modeling tools. A review of relevant patent literature is included.
A novel surface plasmon coupled tunable wavelength filter for hyperspectral imaging
John F. Turner II, Ajaykumar H. Zalavadia
The development of ultra-compact handheld hyperspectral imagers has been impeded by the scarcity of small widefield tunable wavelength filters. The widefield modality is preferred for handheld imaging applications in which image registration can be performed to counter scene shift caused by irregular user motions that would thwart scanning approaches. Conventional widefield tunable filters like the liquid crystal tunable filter and acousto-optic tunable filter achieve narrow passbands across a wide spectral range by utilizing large interaction lengths, thereby increasing the thickness of the device along the optical path. In addition, these technologies rely on rather bulky external control circuitry and, in the case of acousto-optic filters, high power requirements. In the work presented here, we introduce a novel widefield tunable filter for visible and near infrared imaging based on surface plasmon coupling that can be miniaturized without sacrificing performance. The surface plasmon coupled tunable filter (SPCTF) provides diffraction limited spatial resolution with a <10nm nominal passband and a spurious free spectral range of more than 300nm. Acting on the π-polarized component, the device is limited to transmitting 50 percent of unpolarized incident light. This is higher than the throughput of comparable Lyot-based liquid crystal tunable filters that employ a series of linear polarizers. The design of the SPTF is presented along with a comparison of its performance to calculated estimates of transmittance, spectral resolution, and spectral range.
Novel Systems
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Thermally tunable III-V photonic crystals for coherent nonlinear optical circuits
Ranojoy Bose, Marina Radulaski, Tho Tran, et al.
We present a hybrid photonic architecture using gallium arsenide photonic crystals coupled to silicon nitride waveguides. Chrome microheaters are integrated in the system for tuning the cavities. The combination of low-energy switching elements, combined with low loss photonic waveguides provides an ideal architecture for applications in dedicated optical computing and machine learning applications.
Short range, >100Kbits/s, visible light communication protocol design for high-gamma smartphones
High gamma smartphones based on Android operating system support the development of third-party applications. This kind of devices include subsystems such as sensors and actuators which can be used for diverse purposes. One example is the implementation of short range visible light communication (VLC) channels where the built-in light-emitting diode (LED) is the transmitter, and the complementary metal-oxide semiconductor (CMOS) camera works as the receiver. A major challenge for this communication channel is the modulation bandwidth of the light source which is limited to a few MHz, and the availability of a line-of-sight. The camera shutter is limited to a few frames per second (30 or 60 fps) for a few bits per second transmission, but the Rolling Shutter effect could allow the enhancement of the bit rate. In this work, we propose a VLC protocol design for the use of the built-in camera and the flash LED in order to implement a short range VLC channel, for high gamma mobile-to-mobile devices based on Android. The design is based on On-Off Keying (OOK) modulation for initially transmitting a few bits. Based on the rolling shutter effect in the CMOS image sensor, bright and dark fringes can be observed within each received frame, and the data can then be retrieved. Furthermore, two thresholding schemes for high fluctuation and large extinction ratio (ER) variations in each frame, are explored. Full protocol design and short range (5 cm), >100 kbits/s, VLC demonstration and image processing results will be included in the presentation.
Experimental realisability of lens cloaks
Stephen Oxburgh, Jakub Bělín, Euan N. Cowie, et al.
We recently showed how to construct omni-directional ray-optical transformation-optics devices out of ideal thin lenses. These devices can be seen as theoretical generalisations of the paraxial, four-lens, “Rochester cloak”. Here we investigate the practical realisability of such devices. We use ray-tracing simulations to compare combinations of skew lenses of different types, including ideal lenses and phase holograms of lenses.
Design and implementation of a large depth-of-field and large aperture optical system
Xiaohu Guo, Lingqin Kong, Yijian Wu, et al.
In this paper, it presents a new imaging technology that could realize to extent the depth of field and contribute to receive the large iris aperture optical system. The new technology combines lenses assistance and the aberration modulation. Based on the method, we establish a new optical system. Simulation results indicate that the modulation transfer function (MTF) curves of this optical system have consistency feature during different object distances. According to the feature, we can restore ambiguous images to unambiguous ones. Compared with another normal optical system, the experimental results indicate that the new optical system has the large depth of field and large iris aperture features.
Dip-and-bake low-cost high-performance lenses for smartphone-based microscopy
Bhuvaneshwari Karunakaran, Joseph Tharion, Debjani Paul, et al.
Aspherical optical lenses are known for high performance and aberration free imaging. They are increasingly in demand for developing simple and compact high quality optical systems. The conventional methods of production of aspherical lenses are complex and time-consuming. There is a need for a simple, inexpensive and robust method of fabrication of such lenses. Here, we present a novel, low cost and simple approach to fabricate aspherical lenses reproducibly. The two-step process involves 1) controlled wetting of a curved surface with a transparent, cross-linkable polymer by dipping, and 2) pulling the wetted curved surface from the polymer solution. The curvature of the lens is dependent on the area of wetting, speed of pulling and the curvature of the curved surface. The lenses are produced with less than 5% error, and hence, the approach is reproducible in comparison to the previously reported techniques. A smartphone microscope developed using one of the fabricated lenses is found to have a resolution of ~1.7 μm. In addition, we show an application of these lenses as a means to check for the authenticity of Indian currency notes by a common man. The micro-patterns on the currency note are imaged using the smartphone microscope in ambient light. Also, the lenses have potential applications in developing compact and portable high quality optical systems, such as, endoscopes and microscopes.
Biomedical Applications and Human Factors
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Thin head-mounted display utilizing reflective optics design
Chia-ping Lin, Guo-Dung J. Su
For wearable device, the most importance point for image system is miniaturization. In this paper, we present a headmount display that reduces the distance between the eyeball to the lens and its thickness. In traditional, the thickness of head-mount display is not thin enough because of it is designed that the light source is transmit a series of lenses. It make a large volume of head-mounted display. The system consists of three curve mirrors and a free-form lens. Mirrors and lens can form a reflective design. The image source is placed be next to the eyeball. We expect the image to go through the mirrors to the eyeball so that make the volume of head-mount display can be thinner. The goal of system is 60 mm thick and 140 mm wide. The field of view is designed to be 140 degree. By using the 3D printer, we can make a model of glass to achieve our design.
Gait motion analysis using optical and inertial sensor fusion to design human kinetic energy harvesting systems
Oliver Kröning, Hendrik Rothe
Biomechanical energy harvesting converting kinetic energy from human motion into electrical energy appeared as a promising technology for powering mobile devices. The optimization of these energy harvesting systems requires knowledge about human gait as an energy source to maximize the power output. Therefore, motions during walking and running have to be evaluated to determine the amount of available and convertible energy in several body parts. In case of vibration energy harvesting systems, their efficiency is also dependent on the adjustment of the systems' frequency and dimensions and frequency characteristics to the driving force. Thus, this paper presents a solution fusing optical sensors and inertial measurement units (IMU) to analyze human locomotion. High-speed cameras are used to track the positions and angles of the synchronized inertial body sensors in an earth frame while the IMUs acquire gyroscope, accelerometer and magnetometer data. This data is used to calculate linear acceleration and actual orientation represented in quaternions applying an algorithm by Madgwick. The orientation gives major information about the effect of the driving force on moving masses of the system as energy harvesting devices are often designed as single-axis generators. Furthermore, frequency responses of acceleration data from different body positions while gait cycles are analyzed. Finally, prospects and issues converting acceleration into velocity and position data and vice versa are discussed.
Design, manufacture, and evaluation of prototype telescope windows for use in low-vision aids
Pixellated Optics, a class of optical devices which preserve phase front continuity only over small sub areas of the device, allow for a range of uses that would not otherwise be possible. One potential use is as Low Vision Aids (LVAs), where they are hoped to combine the function and performance of existing devices with the size and comfort of conventional eyewear. For these devices a Generalised Confocal Lenslet Array (GCLA) is designed to magnify object space, creating the effect of traditional refracting telescope within a thin, planar device. By creating a device that is appreciably thinner than existing LVA telescopes it is hoped that the comfort for the wearer will be increased. We have developed a series of prototype GLCA-based devices to examine their real-world performance, focussing on the resolution, magnification and clarity of image attainable through the devices. It is hoped that these will form the basis for a future LVA devices. This development has required novel manufacturing techniques and a phased development approach centred on maximising performance. Presented here will be an overview of the development so far, alongside the performance of the latest devices.
Design of a three-view cooperative scanning handheld OCT probe for intraoperative microvascular imaging (Conference Presentation)
To meet the needs of real-time imaging in intraoperative microsurgical vessel anastomosis and to break through the bottleneck of limited penetration depth caused by absorption and scattering from blood, we present a novel design of three-view cooperative scanning handheld OCT probe. It is based on a low coherence source with 1.3μm central wavelength for extra-vascular imaging. Traditional OCT probe always scan from one direction and suffers from the problem of incomplete cross-sectional view of the vessel under investigation. We've designed an MEMS mirror based OCT handheld probe, which can be used to generate cross-sectional images from 3 view directions to increase the field of view in the depth direction. In addition, to adapt to vessels of different sizes, we've also designed a micro-stage to be used together with the handheld probe to solve the hand-trembling problem. The rectangle scanning range is about 3 * 3mm in three-view, which can meet the imaging demands of most vessels. We believe that application of the probe will greatly improve the quality of micro-vascular anastomosis success rate.
Method for synthesis of high-accuracy dynamic non-linear control systems
Vladimir L. Kodkin
Optical Engineering + Application conference in 2016 had only few reports dedicated to high-accuracy position control systems for optical complexes. However, at SPIE Optics + Photonics Exhibition 2016 dozens of companies offered such projects. In that respect, this report may be of interest for academic community. The main method for assessment of performance of automatic control systems is assessment of stability of a system as it allows the evaluation of dynamics and accuracy as well as the method for additional adjustment and technological capacity of the whole complex comprising the system. As a rule, complex systems do not reduce to linear systems or other known variants, so their analysis is normally based on modeling or simplified calculation. In the suggested paper the known criterion of stability for non-linear systems by Popov involves not frequency locus of linear part, but logarithmic frequency characteristics of the system, including non-linear frequency characteristics. It allows the development of conditions of stability and methods of adjustment for such complex systems as servo drives with nonrigid mechanics and alternating-current systems which cannot be analyzed with the help of known methods. In the systems where the stated methods are used accuracy and speed performance are increased fivefold at an average. All theoretical calculations are confirmed by experiments and modeling.
Volumetric Displays and 3D Imaging
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Glasses-free 2D/3D switchable display using an integrated single light-guide plate (LGP) with a trapezoidal light-extraction (TLE) film
Jin-Ho Lee, Yoonsun Choi, Igor Yanusik, et al.
A 10.1-inch 2D/3D switchable display using an integrated single light-guide plate (LGP) with a trapezoidal lightextraction (TLE) film was designed and fabricated. The integrated single LGP was composed of inverted trapezoidal line structures made by attaching a TLE film on its top surface and cylindrical lens structures on its bottom surface. The top surface of the TLE film was also bonded to the bottom surface of an LCD panel to maintain a 3D image quality, which can be seriously deteriorated by the gap variations between the LCD panel and the LGP. The inverted trapezoidal line structures act as slit apertures of parallax barriers for 3D mode. Light beams from LED light sources placed along the left and right edges of the LGP bounce between the top and bottom surfaces of the LGP, and when they collide with the inclined surfaces of the inverted trapezoidal structures, they are emitted toward the LCD panel. Light beams from LED light sources arranged on the top and bottom edges of the LGP are emitted to the lower surface while colliding with the cylindrical lens structures, and are reflected to the front surface by a reflective film for 2D mode. By applying the integrated single LGP with a TLE film, we constructed a 2D/3D switchable display prototype with a 10.1-inch tablet panel of WUXGA resolution (1,200×1,920). Consequently, we showed light-field 3D and 2D display images without interference artifacts between both modes, and also achieved luminance uniformity of over 80%. This display easily generates both 2D and 3D images without increasing the thickness and power consumption of the display device.
Combining three wavelength illumination and parallel phase shift interferometry for high-speed high-resolution and real-time motion tracking and 3D imaging (Conference Presentation)
Phase based imaging and sensing have been for decades effective optical methodologies for high resolution surface profiling. Several techniques for acquiring the phase information encoding the surface topography have been developed; the most prominent is phase shift interferometry (PSI) in which several phase shifted interference images are usually acquired in a sequence and are algebraically combined to extract the phase information. However, phase imaging is limited both by the 2π phase modulo limiting the ability to map structures with heights only up to half the source's wavelength i.e. several hundreds of nm, and also by error induced by the movements of the sample between the acquisitions of phase shifted interference images. Several approached for dealing with these limitations have been developed that provided only a limited solution, e.g. using a beat wavelength interferogram by a two wavelength illumination but that is more sensitive to phase noise and thus less accurate and parallel PSI in which all phase shifted images are acquired simultaneously but that does not resolve the height limitation. We have developed a combined and improved technique for parallel PSI and three wavelength illumination enabling overcoming both limitations without elevating phase noise sensitivity and have set up two prototypes: the first allowing video rate 3D imaging of moving samples such as biological live samples or high throughput scanning of metrology samples with nm scale resolution, and the second allowing single point very high speed axial motion tracking and vibrometry with sub-nm scale resolution and max step height of 30µm.
Metrology and Inspection Systems
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Development of quadruplet-camera system for pipe thread measurement
Shudo Takenaka, Toshifumi Kodama, Kingo Sawada, et al.
In optical measurement of pipe threads at the manufacturing plant level, achieving uncertainty of within 1 μm was a problem because the object position and shape are not all the same. The authors propose a measurement method by designing an optical specification to suppress the diffraction effect and adopting optical shading/aberration correction and subpixel edge-detection processing. In this method (Quadruplet-Camera system), 4 CCD line cameras are positioned opposite to 4 parallel light sources in order to measure four points of the pipe circumference, and thread images are acquired by moving the Quadruplet-Camera system in the pipe axial direction. In the usual optical approach, the numerical aperture (NA) of the lens is increased to improve optical resolution. However, as NA increases, diffracted rays which form a diffraction pattern are observed in the edge area of a cylindrical object, and this causes measurement uncertainty. Increasing NA also results in a narrower depth of field (DOF), which causes instability in the measurement results at a manufacturing plant. The authors designed a compatible optical specification, and concluded that stability of measurement, which means eliminating the diffraction effect and securing a wide DOF, should take precedence over high optical resolution for application to a manufacturing plant, and adopted optical shading/aberration correction and subpixel edge-detection processing in order to compensate for lower optical resolution. In this manuscript, first, we explain the proposed method and confirmation experiments in the laboratory. We also explain a new optical measurement system based on the concept described above in a manufacturing plant to confirm the effectiveness of the method. We concluded that the measurement system has sufficient performance, i.e., uncertainty within 1 μm, for use as a practical system.
Robust shearography system for inspection of defects in composite material using diffractive optics
Fabio A. A. da Silva, Daniel Willemann, Analucia V. Fantin, et al.
The increasing industry demand for specialized materials promotes a breakthrough in material engineering. In this context, composite materials have gained recognition and have been increasingly employed in the most diverse segments of the industry. When applied to equipment with structural requirements, it is fundamentally important to periodically inspect these materials to ensure their integrity and safety. Often inspections are performed in the field, under unstable conditions generated by operational and environmental factors. Shearography is a valuable method of nondestructive testing (NDT) for industrial applications. This optical technique is less sensitive to environmental disturbances when compared to other interferometric techniques. This paper presents a new shearography configuration based on Diffractive Optical Elements (DOE). In the proposed configuration, a diffraction grating is positioned between the camera sensor and the imaging lens. Therefore, a more compact and robust system is obtained. Another advantage of the proposed system is related to phase shifting, which is generated by the lateral movement of the diffraction grating. Thus, phase shifting is relative to the diffraction grating period and not the laser wavelength as in traditional interferometers. This feature makes the system insensitive to variations in laser wavelengths. Since the period of the diffraction grating used is about 60 times greater than the laser wavelength applied, the shearography system using diffraction grating becomes much more robust for external influences compared to other configurations based on the Michelson interferometer. This paper also presents the evaluation of the proposed shearography system as well as prospective steps.
540nm pulsed laser design for particle image velocimetry applications
Different types of mechanical and digital devices for measuring the velocity of fluids such as rotameters, annubar tubes, orifice plates, are suitable options. A limitation of such devices is that the direct interaction with the flux causes unwanted perturbations affecting their results. In this work, the design of a 540nm pulsed fiber laser system for measuring the velocity of water as a fluid via the Particle Image Velocimetry (PIV) technique is proposed. In particle image velocimetry, the fluid motion is made visible by adding small tracer particles and from the position of these particles, at two instances of time, it is possible to determine the flow velocity. The proposed, made in-house, noncommercial PIV system consists of: a second harmonic generation Q-switched Yb-doped fiber laser emitting 540nm pulses, a CCD camera, a pair of cylindrical diverging lenses, reference beads, and the fluid under test. The Yb3+-doped fiber laser itself is capable of producing 540nm, 5 – 15ns, 400mJ pulses at 500Hz – 15kHz repetition rates, suitable for PIV flow field studies. Full fiber laser design, in-house PIV system integration and flow field measurement results will be included in the presentation.
A confocal microscope with programmable aperture arrays by polymer–dispersed liquid crystal
A programmable array microscope (PAM) is one kind of confocal microscopes which uses the spatial light modulator (SLM) to serve both the source and detection aperture as the scanning apertures. Usually, PAM uses the digital micromirror device (DMD) or liquid crystal based optical components (like LCOS) as the spatial light modulator. The latter one has no mechanical movement part in the system, but it needs polarizers , and it will reduce the light utilization rate. We present a programmable array microscope (PAM) which uses the polymer-dispersed liquid crystal (PDLC) chip as the spatial light modulator. PDLC is a polarization-free material, so we can improve the light utilization rate twice as other liquid crystal based PAMs. Furthermore, in our system, the incident light is perpendicular to the PDLC chip unlike other systems. Therefore, our system will make the whole system more compact. Also, it can increase the dynamic range compare to other liquid crystal based PAMs.
Poster Session
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Imaging application based on an electrically tunable polarization-independent liquid crystal microlens array
Polarization-independent microlens array based on liquid crystal (PI-LCMLA) has been an interesting and important topic in optoelectronic application. In this study, a polarization-independent microlens array using double layered nematic liquid crystals (LC) with orthogonal alignment is proposed and demonstrated. Two orthogonal LC layers are separated by a double-sided indium-tin oxide silica. Further optical experiments and investigations reveals that the PILCMLA can work in polarization and polarization-insensitive mode by operating the driving voltages. The normalized focusing intensity is no polarization dependence on the incident light. Several raw images at different working modes are obtained through by utilizing this novel configuration with low applied voltages. With advantages in high optical efficiency, simple manufacture, electrically tunable focal length, low power consumption, polarization independence and multi operation modes, this device can not only be used for imaging application but also has many potential applications in optical systems.
An optical chip aggregometer based on laser transmission to detect alterations in the aggregation of glycosylated RBC
Martín A. Toderi, Natalia Lerda, Patricia Buszniez, et al.
The study of erythrocyte (RBC) aggregation is of great interest because of its implications on human health, alterations in erythrocyte aggregation can lead to microcirculatory problems. An optical-chip based system was developed using laser transmission techniques in order to evaluate and characterize RBC aggregation. Studies are carried out with in vitro altered RBC by non-enzymatic glycosylation. Several samples were analyzed, and by computational data processing, characteristic parameters were found, describing RBC aggregation kinetics in order to improve the early detection in clinical environments of these anomalies, generally present in vascular diseases such as hypertension and diabetes.
Common-path holographic objective for conventional photographic camera
In this paper, we introduce a digital holographic camera objective based on conventional customer-oriented components for off-axis external white light illumination. The interferometric module based on a modified common-path point diffraction interferometer provides a direct view of the system and admits self-reference and self-interference operation modes. The proposed system is designed for self-emitting and reflective samples. Its modular assemblage provides easy scalability and up-grade possibilities. The operability of the suggested camera system has been proven for both coherent and low-coherent broadband sources, and reconstructed amplitude and phase information of test samples under white light illumination is presented.
Computer tool for achromatic and aplanatic cemented doublet design and analysis
Tatiana Ivanova, Galina Romanova, Tatiana Zhukova, et al.
Algorithm and computer tool for cemented doublet synthesis by Slusarev’s methodology are presented. Slusarev’s methodology is based on lookup tables that allow calculating doublet radii by given value of third-order coma, spherical aberration and chromatic aberration using specific algorithm. The most time-consuming part of cemented doublet synthesis by Slusarev’s methodology is selection needed parameters from lookup tables. This part is automated and presented in this paper. The input parameters for tool are desired values of third-order coma, spherical aberration and chromatic aberration of cemented doublet. The tool looks up several appropriate pairs of optical glasses corresponding to specified value of chromatic aberration and then calculates radii of surfaces for each pair of glasses corresponding to specified third-order coma and spherical aberration. The resulted third-order aberrations and real aberrations (transverse, longitudinal, axial color and coma) are calculated for obtained system. Several doublets can be analyzed in result table and the chosen one can be imported into Zemax. The calculated cemented doublet parameters can be analyzed and optimized in optical system design software. The tool allows making the first step of optical system design fast and simple. It allows to design not only the system which is free of the third-order spherical aberration, coma and axial color, but obtain necessary value of aberration for compensation of aberrations in another part of optical system. Possibility to automatically choose optical glasses and compare the real aberration of the preliminary designed system is especially important features of the developed software.
CMOS image sensor for extracting depth information using offset pixel aperture technique
The 3-dimensional (3D) imaging is an important area which can be applied to face detection, gesture recognition, and 3D reconstruction. Many techniques have been reported for 3D imaging using various methods such as time of fight (TOF), stereo vision, and structured light. These methods have limitations such as use of light source, multi-camera, or complex camera system. In this paper, we propose the offset pixel aperture (OPA) technique which is implemented on a single chip so that the depth can be obtained without increasing hardware cost and adding extra light sources. 3 types of pixels including red (R), blue (B), and white (W) pixels were used for OPA technique. The aperture is located on the W pixel, which does not have a color filter. Depth performance can be increased with a higher sensitivity because we use white (W) pixels for OPA with red (R) and blue (B) pixels for imaging. The RB pixels produce a defocused image with blur, while W pixels produce a focused image. The focused image is used as a reference image to extract the depth information for 3D imaging. This image can be compared with the defocused image from RB pixels. Therefore, depth information can be extracted by comparing defocused image with focused image using the depth from defocus (DFD) method. Previously, we proposed the pixel aperture (PA) technique based on the depth from defocus (DFD). The OPA technique is expected to enable a higher depth resolution and range compared to the PA technique. The pixels with a right OPA and a left OPA are used to generate stereo image with a single chip. The pixel structure was designed and simulated. Optical performances of various offset pixel aperture structures were evaluated using optical simulation with finite-difference time-domain (FDTD) method.