Galvo Scanner Research Articles

Instrumentation Design of a High-Speed Fluorescence Lifetime Imaging Microscope Tailored to High-Throughput Screening for Drug Discovery

Fluorescence lifetime imaging microscopy (FLIM) is a powerful imaging modality that can provide unique information related to the biological microenvironment of a sample. For instance, when applied to quantifying Förster resonant energy transfer (FRET), the decay characteristics of the fluorescence can be indicative of the degree of protein-protein interaction occurring at a subcellular level. There is a clear interest at the drug discovery level to harness the potential of FLIM-FRET and other FLIM techniques to better characterize and understand the mechanisms of their drug leads.To properly test and isolate the effectiveness of drug leads under varied conditions and doses, the drug discovery process uses high-content screening (HCS) microscopes to image 100,000 samples per day. FLIM techniques have so far been unable to provide a suitable combination of acquisition speed and resolution to fill this demand. Widefield FLIM techniques suffer from out-of-focus light, which is especially detrimental to fitting the lifetimes of fluorescence decays. Typical raster-scanning confocal approaches can offer excellent spatial and temporal resolution with a photomultiplier tube as a single-point detector, but are inherently slow to collect a full FLIM image.We are designing a system to meet these HCS requirements by combining a multiplexed raster scanning approach with a streak camera and high-speed readout camera. In a streak camera, photons incident on the entrance slit are focused to a photocathode. The photoelectrons generated at the photocathode are accelerated through a vacuum tube, across a perpendicular time-varying electric field, which can deflect the electrons to the left or right based on their arrival time. The resulting readout would consist of a spatial axis and a temporal axis. The slit of a streak camera is an excellent method of multiplexing the fluorescence lifetime capture along its spatial axis. Our streak camera (Optronis SC-10) can be filled with up to 100 resolvable optical fiber channels.A lenslet array is used to generate 10x10 focal points on the sample, which can then be scanned over the sample with an x-y galvo system. Given sufficient excitation power, this offers a 100x improvement on acquisition speed. The galvo scanner also provides a descan of the fluorescent signals on the return path, such that the fluorescence signals can be focused into a fixed 2-dimensional optical fiber array. To accommodate the streak camera slit, the 100 fiber channels are rearranged from 10x10 to 1x100.We will discuss the current performance of the system, and the potential improvements for each component to get closer to the required acquisition speed. In particular, there is interest in investigating the use of solid-state devices to replace the streak camera. Single-photon avalanche diode (SPAD) arrays are an emerging technology that could greatly simplify the instrumentation, reduce the acquisition time, and improve the light collection efficiency. There are also potential improvements in frame rate and light economy concerning our excitation sources, optics and readout camera.

MONTE CARLO SIMULATION OF MULTIFOCAL STOCHASTIC SCANNING SYSTEM

Multifocal multiphoton microscopy (MMM) has greatly improved the utilization of excitation light and imaging speed due to parallel multiphoton excitation of the samples and simultaneous detection of the signals, which allows it to perform three-dimensional fast fluorescence imaging. Stochastic scanning can provide continuous, uniform and high-speed excitation of the sample, which makes it a suitable scanning scheme for MMM. In this paper, the graphical programming language — LabVIEW is used to achieve stochastic scanning of the two-dimensional galvo scanners by using white noise signals to control the x and y mirrors independently. Moreover, the stochastic scanning process is simulated by using Monte Carlo method. Our results show that MMM can avoid oversampling or subsampling in the scanning area and meet the requirements of uniform sampling by stochastically scanning the individual units of the N × N foci array. Therefore, continuous and uniform scanning in the whole field of view is implemented.

A parametric piecewise-linear approach to laser projection

A parametric approach to sketching two-dimensional piecewise linear curves by a scanning galvo mirror system is presented. The proposed method uses a decomposed piecewise linear model that is based on the one-dimensional description of Chua-Kang. The curves to be drawn are treated as a parametric system composed of two positional equations, $$X$$ and $$Y$$ , which are related to each other by an artificial parameter $$\mu $$ . To verify the effectiveness of this approach, the proposed formulation is applied to a dual-axis motor/mirror assembly Scanner Galvo Mirror System model LP20 showing its capability to sketch accurately any piecewise linear curve.

High Precision Surface Structuring with Ultra-Short Laser Pulses and Synchronized Mechanical Axes

For surface and 3D structuring in a 2.5D process, ultra-short pulsed laser systems are mostly used in combination with mechanical axes, whereas the mechanical axes can include electrical motor as well as beam deflecting systems like a galvo scanner. The motion of the axes is synchronized with the clock of the laser pulses, by a modification of the electronic axes control. This work shows the scalability of the ablation process up to MHz-regime in relation to surface quality and ablation efficiency, drilling of thin foils without any heat accumulation and deforming problems of the foil. Furthermore the transfer of the machining strategy from a synchronized galvo scanner to a rotating cylinder setup is shown.

Multifocal multiphoton microscopy based on a spatial light modulator.

We present a new multifocal multiphoton microscope that employs a programmable spatial light modulator to generate dynamic multifocus arrays which can be rapidly scanned by changing the incident angle of the laser beam using a pair of galvo scanners. Using this microscope, we can rapidly select the number and the spatial density of focal points in a multifocus array, as well as the locations and shapes of arrays according to the features of the areas of interest in the field of view without any change to the hardware.

A scanning surface plasmon resonance sensor based on the phase shift algorithm

A novel surface plasmon resonance setup is introduced in this paper. By applying a galvo scanner to modulate the incident beam, the interference noise caused by the coherent light source and mismatching optical interfaces can be reduced significantly and a wide measurement range can be acquired meanwhile. In order to calculate the tiny shift of the resonance angle, a new algorithm called the phase shift algorithm based on discrete Fourier transform is proposed. The method measures the angle shift by detecting the signal phase shift in the frequency domain. According to the simulation and experimental results, this method has better resolution, good immunity of light source drift and fast computation speed. The experimental results demonstrate that a resolution of 1.8 × 10−6 RIU (3 standard derivations) is finally acquired with a measurement range from 1.33 to 1.385. It suggests a good potential value in small molecule interaction detection.

Addressable multiregional and multifocal multiphoton microscopy based on a spatial light modulator

Through a combination of a deflective phase-only diffractive spatial light modulator (SLM) and galvo scanners, an addressable multiregional and multifocal multiphoton microscope (AM-MMM) is developed. The SLM shapes an incoming mode-locked, near-infrared Ti:sapphire laser beam into multiple beamlet arrays with addressable shapes and sizes that match the regions of interest on the sample. Compared with conventional multifocal multiphoton microscope (MMM), AM-MMM achieves the effective use of the laser power with an increase of imaging rate and a decrease of photodamage without sacrifice of resolution.

Strategies for Polymer Welding with High-Power Diode Lasers

Diode lasers have become an important tool for polymer welding in automotive industries, in medical and electronics manufacturing. High efficiency and well fitting beam quality make them a perfect tool for industrial applications. With adapted optics it is possible to fit the laser spot shape to the geometry of the work piece. Galvo scanners are the most flexible tool to apply local and precise dose of heat to the work piece. If this flexibility is not needed, the laser spot can be customized by optics to line, circular or arbitrary shaped geometries. For joining transparent parts either an absorbing layer or diode lasers with a wavelength of 1940 nm can be used.

High Speed and High Precision Fs-laser Writing Using a Scanner with Large Numerical Aperture

Currently available high speed scanning systems based on galvo mirrors are equipped with objectives with small numerical apertures (NA < 0.2) which are not sufficient for most of the involume micro structuring processes. Whereas high precision air bearing translation stages are used with microscope objectives the speed is limited to approximately 100 mm/s. In order to overcome these limitations we integrated a galvo scanner into a system with large maximum scanning velocity (50 - 400 mm/s), large numerical aperture (NA = 0.4-1.2), small focus size (0.6 - 2.2 μm), high precision (100 - 400 nm) and computer controlled pre-compensation of spherical aberrations for involume focusing. Furthermore, we combined the scanning system with a computer controlled three axis translation stage to process large flat work pieces such as wafers up to 2 mm in thickness. As application of the scanner high speed direct writing of waveguides, markings, nano structures inside transparent materials as well as the high speed fabrication of 3D micro structures by in-volume selective laser etching are demonstrated.

A Progressive Laser Joining Method

AbstractA newly designed galvo scanner combines the advantages of closed‐loop temperature control by integrated onaxis pyrometer and fast beam deflection. It is used in quasi‐simultaneous polymer welding as well as in selective reflow soldering where several solder joints have to be processed within the working area without using mechanical positioning. The temperature controlled processes are characterized by robustness and increased stability.

High Power Diode Lasers for Industrial Applications

AbstractNew wavelengths, high brightness and increasing reliability are breaking new ground for diode lasers. The higher brightness allows direct fiber coupling of several 100 W in 200 μm and 400 μm fibers and therefore i.e. the pumping of fiber lasers. Such high power fiber coupled laser diodes combined with fast beam deflection units (galvo scanners) have been implemented in industrial processes and used for quasi‐simultaneous welding of polymers, heat treatment in the sub millimeter range or selective soldering in solar cell production. Besides pumping of solid state lasers, high power diode lasers become more and more a competitive tool for many applications in material processing.

Quantification of a three-dimensional velocity vector using spectral-domain Doppler optical coherence tomography

Multiangle, fiber-based, spectral-domain Doppler optical coherence tomography with a phase-resolved algorithm is presented to measure three components of an arbitrary velocity vector. A beam divider that divides a probe beam to have five independent viewpoints and path length delays was designed. The divider was inserted into the sampling arm of a Doppler optical coherence tomography system between the collimator and the first galvo mirror of a two-axis galvo scanner. The divider produced five independent D k's (the average difference between the wave vectors of incoming and outgoing beams) after passing through the focusing lens while keeping two-axis scanning capability. After calibration, an unknown velocity vector field inside a microtube was quantified by solving a three-dimensional minimization problem.

Multiphoton multifocal microscopy exploiting a diffractive optical element.

Multiphoton multifocal microscopy (MMM) usually has been achieved through a combination of galvo scanners with microlens arrays, with rotating disks of microlens arrays, and cascaded beam splitters with asynchronous rastering of scanning mirrors. Here we describe the achievement of a neat and compact MMM by use of a high-diffraction-efficiency diffractive-optic element that generates a multiple-spot grid of uniform intensity to achieve higher fidelity in imaging of live cells at adequate speeds.

Construction of a laser scanning microscope for multiphoton excited optical fabrication

We present the construction and performance of a simple, programable, laser scanning nonlinear optical microscope for three-dimensional (3D) submicron fabrication. While the primary purpose of the microscope is for optical fabrication this instrument can also perform routine nonlinear optical imaging. The instrument consists of a commercial femtosecond laser system, an upright optical microscope, programable x–y scanning galvo mirrors, axial focus motor with an optical encoder, and single photon counting detection electronics. The mirror scanning and data acquisition are synchronous and are controlled by a single multipurpose I/O board and a graphical user interface written in a LabVIEW framework. The scanner is configured to scan a variety of geometrical patterns with user—controllable speeds, sizes, and aspect ratios, in either filled-in or perimeter patterns. Examples of 3D structures include channel-type structures for potential microfluidic applications and open boxes for encapsulation of cells for tissue engineering. Resolution in terms of imaging and fabrication are determined by fluorescence measurements of subresolution beads and scanning electron microscopy, respectively.

Femtosecond laser microstructuring of materials

Femtosecond laser pulses at 790 and 395 nm combined with a scanning galvo mirror system have allowed the ablation of high quality microchannels in Pyrex, fused silica and silicon (100) for microchemical applications. While Pyrex and fused silica can be micromachined in the near infrared or UV, silicon can only be micromachined to the required depths of ∼50 μm in the near UV where the linear absorption coefficient is much higher. Residual roughness on these materials is <1 μm.