Laser Line Scan Imaging Research Articles

Laser line scan underwater imaging by complementary metal–oxide–semiconductor camera

This work employs the complementary metal–oxide–semiconductor (CMOS) camera to acquire images in a scanning manner for laser line scan (LLS) underwater imaging to alleviate backscatter impact of seawater. Two operating features of the CMOS camera, namely the region of interest (ROI) and rolling shutter, can be utilized to perform image scan without the difficulty of translating the receiver above the target as the traditional LLS imaging systems have. By the dynamically reconfigurable ROI of an industrial CMOS camera, we evenly divided the image into five subareas along the pixel rows and then scanned them by changing the ROI region automatically under the synchronous illumination by the fun beams of the lasers. Another scanning method was explored by the rolling shutter operation of the CMOS camera. The fun beam lasers were turned on/off to illuminate the narrow zones on the target in a good correspondence to the exposure lines during the rolling procedure of the camera’s electronic shutter. The frame synchronization between the image scan and the laser beam sweep may be achieved by either the strobe lighting output pulse or the external triggering pulse of the industrial camera. Comparison between the scanning and nonscanning images shows that contrast of the underwater image can be improved by our LLS imaging techniques, with higher stability and feasibility than the mechanically controlled scanning method.

Performance considerations for continuous-wave and pulsed laser line scan (LLS) imaging systems

Extended range underwater optical imaging techniques can be classified into one of two broad categories; those which use synchronously scanned narrow source and receiver paths to restrict both back-scattered and forward-scattered light reaching the receiver (continuouswave laser line scan); and those which use pulsed sources and time-gating to remove back-scatter noise (pulsed laser line scan and pulse-gated laser line scan). Laser line scan systems are observed to perform at up to 5 to 6 optical attenuation lengths, but greater standoff distances are desirable for seabed imaging using the growing fleet of autonomous underwater vehicles (AUVs). Currently, a moderate physical separation between laser and receiver is necessary to reject near-field multiple back-scatter, which imposes restrictions on AUV miniaturization. Recent experiments and theoretical modeling reveal that significant imaging improvements are possible over the existing continuous-wave laser line scan systems (LLS), by using a pulsed-gated version of the LLS (PG-LLS). However, the use of such a technique has a greater advantage in reducing the overall form factor over conventional LLS imaging system, as well as providing greater depth-of-field. In this paper, we present experimental results comparing both LLS and PG-LLS systems for several source-receiver separations and standoff distances. These results compare favorably with images obtained from validated LLS image simulation tools, and indicate the potential for reducing the source-receiver separation and therefore the system size.

Distinct activity phases during the recent geologic history of a Gulf of Mexico mud volcano

Laser line scan imaging and chirp sub-bottom profiling were used to detail the morphology of a submarine mud volcano and brine-filled crater at 652 m water depth in the northern Gulf of Mexico. The mud volcano has a relief of 6 m and a basal diameter of about 80 m. The feature comprises a central, brine-filled crater (253 m 2) surrounded by a continuous bed of methanotrophic mussels ( Bathymodiolus childressi) covering 434 m 2 and a patchy bed covering an additional 214 m 2 of the periphery. The brine pool was mostly <2 m deep, but there were two holes of >28 m and 12 m deep, respectively at the northern end of the pool which emitted continual streams of small clear bubbles. Sub-bottom profiles indicated three distinct strata beneath the present surface of the mud volcano. Integration of 17 profiles shows that the mud volcano has been built in at least three successive stages: the lowest stage deposited 35,400 m 3, while the middle and upper stages deposited 7700 and 20,400 m 3, respectively. Piston cores were taken at the northern edge of the mussel bed and a site ∼100 m southwest of the pool. Mussel and lucinid shells were recovered from the closer core, lucinid shells from the distant core. A mussel shell from 3.4 m sub-bottom had a Δ 14C age of 16.2 ka. Mixture of modern carbon with “carbon dead” reservoir material would produce actual ages ∼2 ka less than the radiocarbon ages.

Abstract 577: Origin and Therapeutic Efficacy of Human Cardiac Progenitor Cells

To establish whether progenitor cells are present in the human heart (hCPCs) and have phenotypic properties distinct from human hematopoietic stem cells (hHSCs), samples of human myocardium were enzymatically dissociated and c-kit-positive-cells were sorted and plated immediately to obtain clones derived from single founder cells. By FACS analysis, freshly isolated hCPCs comprised 1.1±1.0% of the population and were negative for HSC markers, CD34 and CD133, and KDR. They were also negative for epitopes of monocytes, CD14 and CD16, mast cells, CD45, and lymphocytes, CD3 and CD20. The phenotype of hCPCs was completely different from that of human bone marrow cells which were positive for these surface antigens. Only small fractions of hCPCs expressed GATA4 and Nkx2.5. Of 1,530 seeded hCPCs, 11 clones were generated accounting for 0.7% cloning efficiency. Subsequently, these cells were injected in immunodeficient mice and rats at the time of coronary occlusion and 5 days after infarction. This was done to assess whether hCPCs differentiated into myocytes and coronary vessels immediately after ischemic injury and in the presence of a well-developed infarct. In both cases, hCPCs regenerated the infarcted myocardium. Connexin 43 and N-cadherin were detected between recipient rodent myocytes and newly formed human myocytes. The problem was then whether the structural integration of these two myocyte populations had a physiological counterpart. Studies were performed using an ex vivo preparation together with two-photon microscopy and laser line-scan imaging. EGFP-positive-hCPCs were injected in infarcted mice and the heart was studied 2-weeks later. The heart was perfused with an oxygenated Tyrode solution containing the calcium indicator Rhod-2 and stimulated at 1 Hz. Calcium transients was recorded in EGFP positive human myocytes and EGFP negative mouse myocytes. The synchronicity in calcium tracings between these two distinct cell pools was apparent, pointing to the functional integration of newly formed EGFP-positive human myocytes with the surrounding EGFP-negative mouse myocytes. Thus, the human heart contains hCPCs which are not of bone marrow origin and possess the ability to acquire the cardiomyocyte and coronary vascular cell lineages.

Using Laser Line Scan Imaging Technology to Assess Deepwater Seafloor Habitats in the Monterey Bay National Marine Sanctuary

We conducted a 9-day field test of laser line scan (LLS) imaging technology to characterize and explore seafloor habitats in and around the Big Creek Marine Ecological Reserve (BCER) within the Monterey Bay National Marine Sanctuary off the central California coast. Our goal was to evaluate the utility of LLS technology for assessing the distribution and abundance offish, megafaunal invertebrates, and seafloor habitats, and to compare LLS images with those acquired from side-scan sonar and a remotely operated vehicle (ROV). We surveyed an area approximately 2.6 km long and 0.4 km wide, extending inside and directly outside BCER. Using LLS technology, we imaged isolated rock outcrops with patches of large sea anemones and dense groups of fishes, drift kelp, sea pens, salp chains, and individual, sedentary benthic fishes (including California halibut, Pacific electric ray, ratfish, and juvenile lingcod). As can be achieved with side-scan sonar, the LLS system also did an excellent job of imaging structural details of low-relief features such as sand waves and ripples. The LLS system offered the advantage of imaging some of the biogenic components of habitat and of describing their spatial relationships with detail that currently is not possible using acoustic techniques such as side-scan and multibeam sonar. However, the ROV far exceeded the capability of a LLS system to discern organisms at the highest possible taxonomic level, which ultimately will affect measures of diversity. The ability to visualize the seafloor in a broad context from a mosaic of LLS images could help us understand physical and anthropogenic (e.g., bottom trawling) processes that influence dynamic benthic habitats. Further development and use of LLS technology have the potential to improve our understanding, quantification, and protection of fish habitats.