Author(s):

Zhou, Quanyu; Chen, Zhenyue; Liu, Yu-Hang; El Amki, Mohamad; Glück, Chaim; Droux, Jeanne; Reiss, Michael; Weber, Bruno; Wegener, Susanne & Razansky, Daniel

Abstract:

“Wide-field fluorescence imaging is an indispensable tool for studying large-scale biodynamics. Limited space-bandwidth product and strong light diffusion make conventional implementations incapable of high-resolution mapping of fluorescence biodistribution in three dimensions. We introduce a volumetric wide-field fluorescence microscopy based on optical astigmatism combined with fluorescence source localization, covering 5.6×5.6×0.6 mm^3 imaging volume. Two alternative configurations are proposed exploiting multifocal illumination or sparse localization of point emitters, which are herein seamlessly integrated in one system. We demonstrate real-time volumetric mapping of the murine cortical microcirculation at capillary resolution without employing cranial windows, thus simultaneously delivering quantitative perfusion information across both brain hemispheres. Morphological and functional changes of cerebral vascular networks are further investigated after an acute ischemic stroke, enabling cortex-wide observation of concurrent collateral recruitment events occurring on a sub-second scale. The reported technique thus offers a wealth of unmatched possibilities for non- or minimally invasive imaging of biodynamics across scales.”

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Author(s):

Aranchuk, Vyacheslav; Kasu, Ramachandran; Li, Junrui; Aranchuk, Ina & Hickey, Craig

Abstract:

“Multi-beam laser Doppler vibrometers (MB-LDVs) have an advantage over scanning single-beam laser Doppler vibrometers (LDVs) due to the reduction in measurement time and their ability to measure non-stationary and transient events. However, the number of simultaneously interrogated points in current MB-LDVs is limited due to the complexity of the electronic hardware, which increases with the number of measurement channels. Recent developments of high-speed line-scan CMOS cameras suggest that their use in MB-LDVs can reduce the hardware complexity and increase the number of measurement channels. We developed a MB-LDV based on a digital line-scan CMOS camera that simultaneously measures vibrations on a linear array of 99 points. The experimental setup and performance of the developed MB-LDV are discussed in this paper.”

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Author(s):

Touil, Mohamed; Idlahcen, Said; Becheker, Rezki; Lebrun, Denis; Rozé , Claude; Hideur, Ammar & Godin, Thomas

Abstract:

“Driven by many applications in a wide span of scientific fields, a myriad of advanced ultrafast imaging techniques have emerged in the last decade, featuring record-high imaging speeds above a trillion-frame-per-second with long sequence depths. Although bringing remarkable insights into various ultrafast phenomena, their application out of a laboratory environment is however limited in most cases, either by the cost, complexity of the operation or by heavy data processing. We then report a versatile single-shot imaging technique combining sequentially timed all-optical mapping photography (STAMP) with acousto-optics programmable dispersive filtering (AOPDF) and digital in-line holography (DIH). On the one hand, a high degree of simplicity is reached through the AOPDF, which enables full control over the acquisition parameters via an electrically driven phase and amplitude spectro-temporal tailoring of the imaging pulses. Here, contrary to most single-shot techniques, the frame rate, exposure time, and frame intensities can be independently adjusted in a wide range of pulse durations and chirp values without resorting to complex shaping stages, making the system remarkably agile and user-friendly. On the other hand, the use of DIH, which does not require any reference beam, allows to achieve an even higher technical simplicity by allowing its lensless operation but also for reconstructing the object on a wide depth of field, contrary to classical techniques that only provide images in a single plane. The imaging speed of the system as well as its flexibility are demonstrated by visualizing ultrashort events on both the picosecond and nanosecond timescales. The virtues and limitations as well as the potential improvements of this on-demand ultrafast imaging method are critically discussed.”

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Author(s):

Kim, Sehyeon; Chen, Zhaowei & Alisafaee, Hossein

Abstract:

“We report on developing a non-scanning laser-based imaging lidar system based on a diffractive optical element with potential applications in advanced driver assistance systems, autonomous vehicles, drone navigation, and mobile devices. Our proposed lidar utilizes image processing, homography, and deep learning. Our emphasis in the design approach is on the compactness and cost of the final system for it to be deployable both as standalone and complementary to existing lidar sensors, enabling fusion sensing in the applications. This work describes the basic elements of the proposed lidar system and presents two potential ranging mechanisms, along with their experimental results demonstrating the real-time performance of our first prototype.”

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Author(s):

Fukuda, Tomoaki; Ji, Yonghoon & Umeda, Kazunori

Abstract:

“This paper presents very compact range image sensors for short distance measurement, which is suitable for robot hands, etc. Robot manipulation such as grasping is one of the applications that require a range image sensor to obtain threedimensional (3D) information of the target object. For such applications, it is necessary to avoid the occlusion by a robot manipulator or a robot hand while measurement, and it is effective to attach a sensor to the robot hand for the avoidance. For this aim, a range sensor that is small enough and can measure at the short distance is required. Two sensors are constructed in this paper: one uses a multi-slit laser projector and the other uses a multi-spot laser projector. A small laser projector and a small camera is combined and range images are obtained in real time using the principle of active stereo. Appropriate methods to obtain range image are proposed for both sensors, and especially for the one with a multislit laser projector, a method to use both disparity and the intensity of laser light image is presented. The effectiveness of the proposed sensors is verified through short-range object measurement experiments.”

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Author(s):

Ruser, H.; Kaltenbach, A.; Mechold, L.; Obée, F. & Piela, F.

Abstract:

“The concept, design guidelines and reconstruction results for a universal gesture-based optical remote control with simple quasi-intuitive operation are presented. The buttonless hand-held flashlight-type device emits ‘structured’ infrared light with a pseudo-random spatial pattern projected by a diffractive optical element (DOE). A cost-effective array of photodetectors on or near the device to be remotely controlled records the spatio-temporal intensity changes while a gesture is carried out. From the consecutive time lags between highly correlated signal segments received at each pair of photodetectors, the velocity vector is composed from which Cartesian coordinates of the trajectory of motion of the pattern are calculated and the gesture is reconstructed. Extensive simulations varying major design parameters of the DOE pattern and the receiver array were carried out. Based on simulated and typical practical gestures obtained from user tests, design parameters for a highly satisfactory reconstruction performance could be identified.”

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Author(s):

Askari, M.; Tuck, C. J.; Hu, Q.; Hague, R. J. M. & Wildman, R. D.

Abstract:

“Multi-Photon Polymerization (MPP) is a technique used to fabricate complex micro-scale 3D structures using ultra-short laser pulses. Typically, MPP is used to manufacture micron-scale components in photopolymer materials. However, the development of micron scale processes that can produce components from multiple materials within a single manufacturing step would be advantageous. This would allow the inclusion of particles that are manipulated and embedded within structures with sub-micron feature sizes.

To achieve this, an MPP system was combined with an optical trapping (OT) setup in order to independently manipulate microparticles in the x, y and z planes. Particles were transported into the fabrication site using the OT and encapsulated using the MPP laser. Here it is shown that combining the OT capabilities with an additive manufacturing technique enables the production of complex multi-material artifacts.”

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Author(s):

Min, Gihyeon; Lee, Byung-Tak; Kim, Nac Woo & Lee, Munseob

Abstract:

“We propose a novel schlieren imaging method by projecting a random dot pattern, which is generated in a light source module that includes a diffractive optical element. All apparatuses are located in the source side, which leads to one-body sensor applications. This pattern is distorted by the deflections of schlieren objects such that the displacement vectors of random dots in the pixels can be obtained using the particle image velocity algorithm. The air turbulences induced by a burning candle, boiling pot, heater, and gas torch were successfully imaged, and it was shown that imaging up to a size of 0.7 m  ×  0.57 m is possible. An algorithm to correct the non-uniform sensitivity according to the position of a schlieren object was analytically derived. This algorithm was applied to schlieren images of lenses. Comparing the corrected versions to the original schlieren images, we showed a corrected uniform sensitivity of 14.15 times on average.”

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Author(s):

Vandenhouten, Ralf; Hermerschmidt, Andreas & Fiebelkorn, Richard

Abstract:

“Structured light has become a widespread technique for the development of camera-based 3D sensors. The structured illumination provides texture to homogeneous objects and thus allows for the reliable determination of the disparity of each object point in a stereo-camera setting. Even a monocular 3D sensor is possible if the light projector has a fixed relative position to the camera and if the structured light is coded, i.e. the position within the whole light pattern can be reconstructed uniquely from a small local window of the pattern, the uniqueness window. Coded patterns with such a uniqueness property are called Perfect SubMaps (PSM). In our paper we focus on the design and evaluation of the subset of symmetric isolated binary toroidal PSMs (SIBTPSM) for structured light patterns, because of their beneficial properties with respect to the signal-to-noise ratio and the use with laser light sources and DOEs. We define several figures of merit that are relevant for the practical use of PSMs in a 3D sensor: the PSM size, the size of the uniqueness window, the Hamming distance, the density, and the homogeneity. We have created SIBTPSMs using our own dedicated algorithms and have designed and fabricated DOEs that produce these patterns with large fan angles of 61° × 47° when used with near-infrared diode lasers (λ = 830nm). We analyze the influence of these characteristics on the 3D measurement process by theory, simulations, and experiments. The patterns of publicly available DOEs based on SIBTPSMs are used for comparison and reference. Our results show that the PSM width, the uniqueness window size, the minimum and average Hamming distances, and the uniformity have strong impact on either speed or quality of the 3D reconstruction, whereas the point density and the PSM height are of minor importance.”

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Author(s):

Martins, L. Lages; Ribeiro, A. Silva & e Sousa, J. Alves

Abstract:

“This paper describes the use of diffractive optical elements (DOEs) for metrological traceable geometrical testing of high focal length cameras applied in the observation of large- scale structures. DOEs and related mathematical models are briefly explained. Laboratorial activities and results are described for the case of a high focal length camera used for longdistance displacement measurement of a long-span (2278 m) suspension bridge.”

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