Galvanometer Mirror Research Articles

Video-rate resonant scanning multiphoton microscopy: An emerging technique for intravital imaging of the tumor microenvironment

The abnormal tumor microenvironment fuels tumor progression, metastasis, immune suppression, and treatment resistance. Over last several decades, developments in and applications of intravital microscopy have provided unprecedented insights into the dynamics of the tumor microenvironment. In particular, intravital multiphoton microscopy has revealed the abnormal structure and function of tumor-associated blood and lymphatic vessels, the role of aberrant tumor matrix in drug delivery, invasion and metastasis of tumor cells, the dynamics of immune cell trafficking to and within tumors, and gene expression in tumors. However, traditional multiphoton microscopy suffers from inherently slow imaging rates-only a few frames per second, thus unable to capture more rapid events such as blood flow, lymphatic flow, and cell movement within vessels. Here, we report the development and implementation of a video-rate multiphoton microscope (VR-MPLSM) based on resonant galvanometer mirror scanning that is capable of recording at 30 frames per second and acquiring intravital multispectral images. We show that the design of the system can be readily implemented and is adaptable to various experimental models. As examples, we demonstrate the utility of the system to directly measure flow within tumors, capture metastatic cancer cells moving within the brain vasculature and cells in lymphatic vessels, and image acute responses to changes in a vascular network. VR-MPLSM thus has the potential to further advance intravital imaging and provide new insight into the biology of the tumor microenvironment.

SU-E-T-98: Towards Cell Nucleus Microdosimetry: Construction of a Confocal Laser-Scanning Fluorescence Microscope to Readout Fluorescence Nuclear Track Detectors (FNTDs).

To construct a custom confocal laser scanning microscope (CLSM) capable of resolving individual proton tracks in the volume of an Al2 O3 :C,Mg fluorescent nuclear track detector (FNTD). The spatial resolution of the FNTD technique is at the sub-micrometer scale. Therefore the FNTD technique has the potential to perform radiation measurements at the cell nucleus scale. The crystal volume of an FNTD contains defects which become fluorescent F2+ centers after trapping delta electrons from ionizing radiation. These centers have an absorption band centered at 620 nm and an emission band in the near infrared. Events of energy deposition in the crystal are read-out using a CLSM with sub-micrometer spatial resolution. Excitation light from a 635 nm laser is focused in the crystal volume by an objective lens. Fluorescence is collected back through the same path, filtered through a dichroic mirror, and focused through a small pinhole onto an avalanche photodiode. Lateral scanning of the focal point is performed with a scanning mirror galvanometer, and axial scanning is performed using a stepper-motor stage. Control of electronics and image acquisition was performed using a custom built LabVIEW VI and further image processing was done using Java. The system was used to scan FNTDs exposed to a 6 MV x-ray beam and an unexposed FNTD. Fluorescence images above the unexposed background were obtained at scan depths ranging from 5 - 10 micrometer below the crystal surface using a 100 micrometer pinhole size. Further work needs to be done to increase the resolution and the signal to noise ratio of the images so that energy deposition events may be identified more easily. Natural Sciences and Engineering Research Council of Canada.

Coaxial monitoring of keyhole during Yb:YAG laser welding

In laser remote welding using a scanner, high-speed welding can be achieved by using a 6-axial robot and a galvanometric mirror. In this system, because the laser projection point changes depending on the mirror's position, coaxial monitoring is required to track welding phenomena.This paper presents coaxial monitoring of the keyhole generated by an Yb:YAG laser beam during laser lap welding of steel and Al sheets. A coaxial image camera and a coaxial illumination laser are integrated into the proposed monitoring system. The areas of the keyhole and the full penetration hole were calculated by image processing, and their behaviours were investigated under various welding conditions. The keyhole was monitored using various band-pass filters and a coaxial illumination laser. Adequate filters were suggested for steel and Al alloy welding.

Ninety Years of Polarography

Ninety Years of Polarography

Stimulated Raman hyperspectral imaging based on spectral filtering of broadband fiber laser pulses

We demonstrate a technique of hyperspectral imaging in stimulated Raman scattering (SRS) microscopy using a tunable optical filter, whose transmission wavelength can be varied quickly by a galvanometer mirror. Experimentally, broadband Yb fiber laser pulses are synchronized with picosecond Ti:sapphire pulses, and then spectrally filtered out by the filter. After amplification by fiber amplifiers, we obtain narrowband pulses with a spectral width of <3.3 cm(-1) and a wavelength tunability of >225 cm(-1). By using these pulses, we accomplish SRS imaging of polymer beads with spectral information.

A dual-beam dual-camera method for a battery-powered underwater miniature PIV (UWMPIV) system

A battery-powered in situ Underwater Miniature PIV (UWMPIV) has been developed and deployed for field studies. Instead of generating high-energy laser pulses as in a conventional PIV system, the UWMPIV employs a low-power Continuous Wave (CW) laser (class IIIb) and an oscillating mirror (galvanometer) to generate laser sheets. In a previous version of the UWMPIV, the time between exposures of a pair of particle images, \(\Updelta t\), could not be reduced without loss of illumination strength. This limitation makes it unsuitable for high-speed flows. In this paper, we present a technique to solve this problem by adopting two CW lasers with different wavelength and two CCD cameras in a second-generation UWMPIV system. Several issues including optical alignment, non-uniform distribution of \(\Updelta t\) due to the varying speed of the scanning beam and local flow velocities are discussed. The timing issue is solved through a simple calibration procedure that involves the reconstruction of maps of laser beam arrival time. Comparison of the performance between the new method and a conventional PIV system is presented. Measurements were performed in a laboratory open-channel flume. Excellent agreement was found between the new method and the standard PIV measurement in terms of the extracted vertical profiles of mean velocity, RMS fluctuation, Reynolds stress and dissipation rate of turbulent kinetic energy.

Measuring Neuronal Population Activity Using 3D Laser Scanning

Neural tissue is organized in three-dimensional (3D) networks of neuronal and glial cell populations. To understand the functional organization of these networks, it is desirable to achieve 3D activity measurements from large cell populations in intact tissue with high temporal resolution. Repeated acquisition of image stacks with standard laser-scanning microscopes is too slow. This protocol describes fast 3D calcium imaging in the living brain using mechanical laser scanning with standard galvanometric mirrors and a piezoelectric focusing element. The purpose of 3D laser scanning is to create a 3D line scan that samples relatively homogenously from a particular observation volume. The spatial resolution of this approach is low, except along the line. However, the main goal is not to resolve subcellular structures, but rather to hit as many cell bodies as possible within the volume. In this manner, local network activity can be inferred from the somatic calcium signals of a significant fraction of the cell population. With a sinusoidal swinging microscope objective as a constraint, 3D scan trajectories are generated that sample fluorescence signals from the majority of cells within a cuboidal volume. Measurements with 10-Hz temporal resolution can be achieved for population calcium signals from several hundreds of identified neurons and glial cells within cuboids with side lengths of ∼250 µm. An example cellular 3D orientation map of the rat visual cortex is presented. This 3D laser-scanning technique enables direct observation of in vivo neural network dynamics in cell populations of substantial size.

Video-rate Scanning Confocal Microscopy and Microendoscopy

Confocal microscopy has become an invaluable tool in biology and the biomedical sciences, enabling rapid, high-sensitivity, and high-resolution optical sectioning of complex systems. Confocal microscopy is routinely used, for example, to study specific cellular targets, monitor dynamics in living cells, and visualize the three dimensional evolution of entire organisms. Extensions of confocal imaging systems, such as confocal microendoscopes, allow for high-resolution imaging in vivo and are currently being applied to disease imaging and diagnosis in clinical settings. Confocal microscopy provides three-dimensional resolution by creating so-called "optical sections" using straightforward geometrical optics. In a standard wide-field microscope, fluorescence generated from a sample is collected by an objective lens and relayed directly to a detector. While acceptable for imaging thin samples, thick samples become blurred by fluorescence generated above and below the objective focal plane. In contrast, confocal microscopy enables virtual, optical sectioning of samples, rejecting out-of-focus light to build high resolution three-dimensional representations of samples. Confocal microscopes achieve this feat by using a confocal aperture in the detection beam path. The fluorescence collected from a sample by the objective is relayed back through the scanning mirrors and through the primary dichroic mirror, a mirror carefully selected to reflect shorter wavelengths such as the laser excitation beam while passing the longer, Stokes-shifted fluorescence emission. This long-wavelength fluorescence signal is then passed to a pair of lenses on either side of a pinhole that is positioned at a plane exactly conjugate with the focal plane of the objective lens. Photons collected from the focal volume of the object are collimated by the objective lens and are focused by the confocal lenses through the pinhole. Fluorescence generated above or below the focal plane will therefore not be collimated properly, and will not pass through the confocal pinhole, creating an optical section in which only light from the microscope focus is visible. (Fig 1). Thus the pinhole effectively acts as a virtual aperture in the focal plane, confining the detected emission to only one limited spatial location. Modern commercial confocal microscopes offer users fully automated operation, making formerly complex imaging procedures relatively straightforward and accessible. Despite the flexibility and power of these systems, commercial confocal microscopes are not well suited for all confocal imaging tasks, such as many in vivo imaging applications. Without the ability to create customized imaging systems to meet their needs, important experiments can remain out of reach to many scientists. In this article, we provide a step-by-step method for the complete construction of a custom, video-rate confocal imaging system from basic components. The upright microscope will be constructed using a resonant galvanometric mirror to provide the fast scanning axis, while a standard speed resonant galvanometric mirror will scan the slow axis. To create a precise scanned beam in the objective lens focus, these mirrors will be positioned at the so-called telecentric planes using four relay lenses. Confocal detection will be accomplished using a standard, off-the-shelf photomultiplier tube (PMT), and the images will be captured and displayed using a Matrox framegrabber card and the included software.

Video-rate Scanning Confocal Microscopy and Microendoscopy

Confocal microscopy has become an invaluable tool in biology and the biomedical sciences, enabling rapid, high-sensitivity, and high-resolution optical sectioning of complex systems. Confocal microscopy is routinely used, for example, to study specific cellular targets1, monitor dynamics in living cells2-4, and visualize the three dimensional evolution of entire organisms5,6. Extensions of confocal imaging systems, such as confocal microendoscopes, allow for high-resolution imaging in vivo7 and are currently being applied to disease imaging and diagnosis in clinical settings8,9. Confocal microscopy provides three-dimensional resolution by creating so-called "optical sections" using straightforward geometrical optics. In a standard wide-field microscope, fluorescence generated from a sample is collected by an objective lens and relayed directly to a detector. While acceptable for imaging thin samples, thick samples become blurred by fluorescence generated above and below the objective focal plane. In contrast, confocal microscopy enables virtual, optical sectioning of samples, rejecting out-of-focus light to build high resolution three-dimensional representations of samples. Confocal microscopes achieve this feat by using a confocal aperture in the detection beam path. The fluorescence collected from a sample by the objective is relayed back through the scanning mirrors and through the primary dichroic mirror, a mirror carefully selected to reflect shorter wavelengths such as the laser excitation beam while passing the longer, Stokes-shifted fluorescence emission. This long-wavelength fluorescence signal is then passed to a pair of lenses on either side of a pinhole that is positioned at a plane exactly conjugate with the focal plane of the objective lens. Photons collected from the focal volume of the object are collimated by the objective lens and are focused by the confocal lenses through the pinhole. Fluorescence generated above or below the focal plane will therefore not be collimated properly, and will not pass through the confocal pinhole1, creating an optical section in which only light from the microscope focus is visible. (Fig 1). Thus the pinhole effectively acts as a virtual aperture in the focal plane, confining the detected emission to only one limited spatial location. Modern commercial confocal microscopes offer users fully automated operation, making formerly complex imaging procedures relatively straightforward and accessible. Despite the flexibility and power of these systems, commercial confocal microscopes are not well suited for all confocal imaging tasks, such as many in vivo imaging applications. Without the ability to create customized imaging systems to meet their needs, important experiments can remain out of reach to many scientists. In this article, we provide a step-by-step method for the complete construction of a custom, video-rate confocal imaging system from basic components. The upright microscope will be constructed using a resonant galvanometric mirror to provide the fast scanning axis, while a standard speed resonant galvanometric mirror will scan the slow axis. To create a precise scanned beam in the objective lens focus, these mirrors will be positioned at the so-called telecentric planes using four relay lenses. Confocal detection will be accomplished using a standard, off-the-shelf photomultiplier tube (PMT), and the images will be captured and displayed using a Matrox framegrabber card and the included software.

Digital holographic measurement and phase reconstruction of 3D object based on wavefront data

Digital holography is an attractive method for instantaneous measurement of three-dimensional (3D) objects and numerical reconstruction of the 3D objects after the recording. The reconstruction can be implemented optically for visualization. In this paper, we review a 3D measurement system based on phase-shifting digital holography and an optical 3D reconstruction based on wavefront modulation. In the 3D reconstruction, phase distribution is used for 3D reconstruction because there is no available spatial light modulator that can modulate both amplitude and phase. The viewing zone is limited by the pixel size of phase-mode spatial light modulator. For enlargement of viewing zone, we have proposed a timesharing method to distribute the reconstructed 3D object in wide area by using a Galvanometer mirror. Numerical and experimental results are presented.

Coherent microscopy by laser optical feedback imaging (LOFI) technique

The application of the non-conventional imaging technique LOFI (laser optical feedback imaging) to coherent microscopy is presented. This simple and efficient technique using frequency-shifted optical feedback needs the sample to be scanned in order to obtain an image. The effects on magnitude and phase signals such as vignetting and field curvature occasioned by the scanning with galvanometric mirrors are discussed. A simple monitoring method based on phase images is proposed to find the optimal position of the scanner. Finally, some experimental results illustrating this technique are presented.

Determination of Surface Heat Flow in Mazesta (USSR)

A great number of temperature measurements in deep bore-holes are made on the territory of the Soviet Union. The results of these measurements are partly systematized in the work Problems of Geothermie t1). However they can be hardly used for the calculations of heat flow because of the absence of the corresponding determinations of the thermal conductivity of rock cores taken directly from these boreholes. In the present paper the temperature gradient and the thermal conductivity of samples of rocks for the same place are determined and by means of these data the value of the thermal flow is estimated. For temperature measurements the electric resistance thermometer was used that is designed by Dergunov I. D. and improved for the conditions of work in deep bore-holes (up to 4-5 km) at rather high pressures and temperatures. The electrical resistance was measured by means of the compensation methods by a special potentiometer and a high sensitive mirror galvanometer. Four bringing wires are used for doing away with the erratic currents and the influence of the wires. As a result of it the accuracy of the temperature measurements is about 0.01°C. Fig. 1 represents the exterior of the apparatus and the thermometer. The thermometer is a hollow cylinder on the surface of which a copper wire is winded bifllarily, whose resistance is measured. When the cylinder is buried into a bore-hole it is washed by a solution from outside and inside. Together with the application of ftorplast isolation this decreases the thermal inertia of the thermometer down to 1.5 sec. For the sake of strength annular justs are made on the cylinder. The thermometer stands the pressure up to 600 atm and the temperature up to 200°C.

Heuristically optimal path scanning for high-speed multiphoton circuit imaging

Population dynamics of patterned neuronal firing are fundamental to information processing in the brain. Multiphoton microscopy in combination with calcium indicator dyes allows circuit dynamics to be imaged with single-neuron resolution. However, the temporal resolution of fluorescent measures is constrained by the imaging frequency imposed by standard raster scanning techniques. As a result, traditional raster scans limit the ability to detect the relative timing of action potentials in the imaged neuronal population. To maximize the speed of fluorescence measures from large populations of neurons using a standard multiphoton laser scanning microscope (MPLSM) setup, we have developed heuristically optimal path scanning (HOPS). HOPS optimizes the laser travel path length, and thus the temporal resolution of neuronal fluorescent measures, using standard galvanometer scan mirrors. Minimizing the scan path alone is insufficient for prolonged high-speed imaging of neuronal populations. Path stability and the signal-to-noise ratio become increasingly important factors as scan rates increase. HOPS addresses this by characterizing the scan mirror galvanometers to achieve prolonged path stability. In addition, the neuronal dwell time is optimized to sharpen the detection of action potentials while maximizing scan rate. The combination of shortest path calculation and minimization of mirror positioning time allows us to optically monitor a population of neurons in a field of view at high rates with single-spike resolution, ∼ 125 Hz for 50 neurons and ∼ 8.5 Hz for 1,000 neurons. Our approach introduces an accessible method for rapid imaging of large neuronal populations using traditional MPLSMs, facilitating new insights into neuronal circuit dynamics.

Patterned two-photon photoactivation illuminates spatial reorganization in live cells.

Photoactivatable fluorescent proteins offer the possibility to optically tag and track the location of molecules in their bright state with high spatial and temporal resolution. Several reports of patterned photoactivation have emerged since the development of a photoactivatable variant of the green fluorescent protein (PaGFP) and the demonstration of two-photon activation of PaGFP. To date, however, there have been few methods developed to quantify the spatial reorganization of the photoactivated population. Here we report on the use of singular value decomposition (SVD) to track the time-dependent distribution of fluorophores after photoactivation. The method was used to describe live-cell actin cytoskeleton behavior in primary murine T-cells, in which a dynamic cytoskeleton is responsible for the reorganization of membrane proteins in response to antigen peptide recognition. The method was also used to observe immortalized simian kidney (Cos-7) cells, in which the cytoskeleton is more stable. Both cell types were transfected with PaGFP fused to the F-actin binding domain of utrophin (UtrCH). Photoactivation patterns were written in the samples with a pair of galvanometric scanning mirrors in circular patterns that were analyzed by transforming the images into a time series of radial distribution profiles. The time-evolution of the profiles was well-described by the first two SVD component states. For T-cells, we find that actin filaments are highly mobile. Inward transport from the photoactivation region was observed and occurred on a 1−2 s time scale, which is consistent with retrograde cycling. For Cos-7 cells, we find that the actin is relatively stationary and does not undergo significant centripetal flow as expected for a resting fibroblast. The combination of patterned photoactivation and SVD analysis offers a unique way to measure spatial redistribution dynamics within live cells.

The Light-Emitting Diode as a Light Detector

Alight-emitting diode (LED) and operational amplifier can be used as an affordable method to provide a digital output indicating detection of an intense light source such as a laser beam or high-output LED.1 When coupled with a microcontroller, the combination can be used as a multiple photogate and timer for under $50. A similar circuit is used as a data logging system for a mirror galvanometer, providing a record of changes in the Earth's magnetic field as small as a few nanotesla (nT).

圧電素子を用いたセルフセンシングアクチュエーションによるガルバノミラーの制振制御

This paper presents a method for suppressing the vibration of galvanometric mirrors used in laser positioning systems. In such systems, it is important to carry out fast and high-precision positioning of the mirror and maintain the flatness of the mirror after positioning, so that the required control specifications are achieved. However, resonant vibrations of the mirror, which are excited by the moment force during positioning, lead to residual vibrations after positioning, thereby, deteriorating the flatness of the mirror and laser manufacturing accuracy. Therefore, we attempt to suppress such vibrations by mounting a piezoelectric element on the mirror, so that the functions of the actuator and sensor of the piezoelectric element are made use of when designing the vibration suppression controller. The applicability of the proposed method to industrial galvano scanners has been verified by performing experiments using a positioning device.

3365 Proposal of High Speed Raster Scanning in Stereolithography

In this study, we have proposed a stereolithography which has an even higher laser beam scanning speed than the conventional galvanometer mirror by using a polygon mirror capable of raster scanning only as the beam deflection device. Moreover, the recoating process to form a smooth unhardened liquid resin surface was done at the same time as raster scanning. The experimental results suggest that the use of high speed laser beam raster scanning in the stereolithography is possibile to shorten the fabrication time and formed high accuracy model.

Intrinsic Coupling between Gamma Oscillations, Neuronal Discharges, and Slow Cortical Oscillations during Human Slow-Wave Sleep

In the first electrocorticograms, Richard [Caton (1877)][1] connected a mirror galvanometer to exposed rabbit brains and observed slow sleep-related fluctuations. Several decades later, [Loomis et al. (1937)][2] applied the then-fledgling technique of scalp EEG to classify sleep stages in humans,

Volumetric Display System Using a Digital Micromirror Device Based on Inclined-Plane Scanning

Experimental results of a volumetric display system based on three-dimensional (3D) scanning using an inclined image are reported. An optical real image of an inclined two-dimensional (2D) display device is moved laterally by an optical mirror scanner. Inclined cross-sectional images of a 3D object are projected in accordance with the position of the image plane. A 3D real image is formed as a stack of 2D cross-sectional images as a result of high-speed scanning. This 3D image can satisfy all the criteria for stereoscopic vision. An experimental system using a galvanometer mirror and a digital micromirror device was constructed, and generated three-dimensional images consisting of 1024×768×200 voxels. A multilevel image can be formed by a spatial dithering technique, even though the binary display device was used.

Linear terrestrial laser scanning using array avalanche photodiodes as detectors for rapid three-dimensional imaging

As an active remote sensor technology, the terrestrial laser scanner is widely used for direct generation of a three-dimensional (3D) image of an object in the fields of geodesy, surveying, and photogrammetry. In this article, a new laser scanner using array avalanche photodiodes, as designed by the Shanghai Institute of Technical Physics of the Chinese Academy of Sciences, is introduced for rapid collection of 3D data. The system structure of the new laser scanner is first presented, and a mathematical model is further derived to transform the original data to the 3D coordinates of the object in a user-defined coordinate system. The performance of the new laser scanner is tested through a comprehensive experiment. The result shows that the new laser scanner can scan a scene with a field view of 30° × 30° in 0.2 s and that, with respect to the point clouds obtained on the wall and ground floor surfaces, the root mean square errors for fitting the two planes are 0.21 and 0.01 cm, respectively. The primary advantages of the developed laser scanner include: (i) with a line scanning mode, the new scanner achieves simultaneously the 3D coordinates of 24 points per single laser pulse, which enables it to scan faster than traditional scanners with a point scanning mode and (ii) the new scanner makes use of two galvanometric mirrors to deflect the laser beam in both the horizontal and the vertical directions. This capability makes the instrument smaller and lighter, which is more acceptable for users.