Near-infrared Laser Scanning Research Articles

ACCURACY OF MEASURING THE BOTTOM OF A POND BY AIRBORNE LIDAR BATHYMETRY (ALB)

Abstract. Airborne Lidar Bathymetry (ALB) is a technology for characterizing the depths of shallow-water bodies in relatively transparent waters from an airborne platform using a scanning and pulsed light beam. A bathymetric LiDAR usually uses wo laser pulses: one is a near-infrared (NIR) laser pulse for land topography and the other is a green laser pulse for submarine topography. In recent years, ALB has become more popular in river and coastal surveying in Japan. The accuracy of ALB has been verified by comparison with the results of acoustic sounding or levelling. However, since the comparison with either acoustic sounding or levelling is limited to a partial comparison at a point or on a line such as a cross section, it is not suitable for overall verification for detailed terrain features. In addition, accuracy verification by comparison between the results of ALB's green laser scanning and those of NIR laser scanning has been performed in the past only on land, but not in water. As scattering of the green laser occurs when measuring in water, it is possible to affirm that the verification under actual operating conditions has not been sufficiently investigated. In this study, we conducted NIR laser scanning in a natural pond and an artificial pool when they had no water, and conducted green laser scanning when they were filled with water. Thus, the NIR laser scanning and the green laser scanning could be compared in terms of surface measurement for the same bottom of the water body. It was confirmed that the green laser in water has sufficient accuracy compared to the NIR laser in actual operation conditions.

Human forehead recognition: a novel biometric modality based on near‐infrared laser backscattering feature image using deep transfer learning

Human recognition systems are an essential tool for identity verification. Though various parts of the human body have been widely used as input data for decades, developing new biometric technology is still necessary to enhance the security system complexity. This article presents a novel biometric modality based on forehead feature images acquired from a specially designed near-infrared laser scanning system. The authors selected state-of-the-art deep convolutional neural networks (CNN), including VGGNet, ResNet, and Inception-v3, to demonstrate the human forehead recognition task. Though large-scale training data is generally required for learning a promising CNN model, they showed the feasibility to transfer the feature representation knowledge of the networks that were pre-trained on the data from a different domain and fine-tuned the target network on the limited dataset of forehead feature images. This transfer learning approach establishes the usability of human forehead recognition and allows us to implement this biometric modality for real-world application.

Near-infrared laser scanning confocal microscopy and its application in bioimaging

Near-infrared (NIR) fluorescence imaging is an important imaging technology in deep-tissue biomedical imaging and related researches, due to the low absorption and scattering of NIR excitation and/or emission in biological tissues. Laser scanning confocal microscopy (LSCM) plays a significant role in the family of fluorescence microscopy. Due to the introduction of pinhole, it can provide images with optical sectioning, high signal-to-noise ratio and better spatial resolution. In this study, in order to combine the advantages of these two techniques, we set up a fluorescence microscopic imaging system, which can be named as NIR-LSCM. The system was based on a commercially available confocal microscope, utilizing a NIR laser for excitation and a NIR sensitive detector for signal collection. In addition, NIR fluorescent nanoparticles (NPs) were prepared, and utilized for fluorescence imaging of the ear and brain of living mice based on the NIR-LSCM system. The structure of blood vessels at certain depth could be visualized clearly, because of the high-resolution and large-depth imaging capability of NIR-LSCM.

An entropy-based filtering approach for airborne laser scanning data

Parameter-tuning is a challenging task when generating digital terrain models from airborne laser scanning (light detection and ranging, LiDAR) data. To address this issue, this paper presents a filtering method for near-infrared laser scanning data that exploits the principle of entropy maximization as the optimization objective. The proposed approach generates ground elevation of point cloud by constructing a triangulated irregular network, calculates the entropy of the elevation from different parts, and automatically separates ground and non-ground points by the principle of entropy maximization. Experimental results from different ground surfaces show that the proposed entropy-based filtering method can effectively extract bare-earth points from the point cloud without adjusting thresholds.

Near-Infrared Laser Scanning (NILS) to Differentiate Historical Inks, Deployed on a Stained and Faded Ninth-Century Fragment of Boethius Reused as Binding Material: Proving a Concept

AbstractIn this paper we describe the use of a dual-wavelength near-infrared laser scanner (NILS) to reveal ink differences in a ninth century Boethius fragment. The scanning system worked at 680 and 780 nm excitation wavelength with a maximal resolution of 21 µm. Fresh images were recorded at both wavelengths and compared with others based on conventional methods, such as UV photography and infrared reflectography. Whereas the latter secured no new information for mapping and distinguishing via inks the layered genesis of the manuscript, images of the fragment based on infrared laser fluorescence revealed the different inks used to elaborate the manuscript. The method revealed and distinguished the respective inks used for glosses, other marginal notes, neumes and the main text. Furthermore, corrections and additions invisible under other types of light were discovered by NILS in combination with paleographic methods. The scope and limitations of NILS when used to investigate stained or faded reused parchment (Makulatur) and/or restored manuscripts are discussed in detail.

Novel Multiwavelength Microscopic Scanner for Mouse Imaging

Real-time in vivo imaging of molecular targets at (sub)cellular resolution is essential in better understanding complex biology. Confocal microscopy and multiphoton microscopy have been used in the past to achieve this goal, but their true capabilities have often been limited by bulky optics and difficult experimental set-ups requiring exteriorized organs. We describe here the development and validation of a unique nearinfrared laser scanning microscope system that uses novel optics with a millimeter footprint. Optimized for use in the far red and near-infrared ranges, the system allows an imaging depth that extends up to 500 Mm from a 1.3-mm-diameter stick objective, which is up to 2 cm in length. We show exceptionally high spatial, temporal, and multiwavelength resolutions of the system and show that it can be applied to virtually any internal organ through a keyhole surgical access. We demonstrate that, when combined with novel far red imaging probes, it is possible to image the cellular details of many organs and disease processes. The new optics, coupled with the use of near-infrared probes, should prove immensely valuable for in vivo cancer imaging.

Dynamic Laser Stimulation Case Studies

Dynamic Laser Stimulation (DLS) techniques based on near-infrared laser scanning are used for failure analysis, design debug, and time margin studies or critical path analysis. In failure analysis, it is applied to localize defects when static techniques can not be applied. Moving from static to dynamic laser stimulation requires a more complex electrical setup. This paper presents several DLS case studies along with the used DLS setup. It is shown that design-process related issues as well as physical defects such as resistive contacts are rapidly and precisely localized.

Robert Feulgen Prize Lecture. Laser tweezers and multiphoton microscopes in life sciences.

Near infrared (NIR) laser microscopy enables optical micromanipulation, piconewton force determination, and sensitive fluorescence studies by laser tweezers. Otherwise, fluorescence images with high spatial and temporal resolution of living cells and tissues can be obtained via non-resonant fluorophore excitation with multiphoton NIR laser scanning microscopes. Furthermore, NIR femtosecond laser pulses at TW/cm2 intensities can be used to realize non-invasive contact-free surgery of nanometer-sized structures within living cells and tissues. Applications of these novel versatile NIR laser-based tools for the determination of motility forces, coenzyme and chlorophyll imaging, three-dimensional multigene detection, non-invasive optical sectioning of tissues ("optical biopsy"), functional protein imaging, and nanosurgery of chromosomes are described.