AODs use radio frequency sound waves to create a tunable diffraction grating that is used to control laser beam output angle. Another disadvantage of polygonal mirrors is that the rotation axis is distant from the mirror face, meaning over the scan period of each mirror face, the axial path length varies during a scan. In contrast to resonant mirrors, the angular range is limited by the number of facets, effectively fixing the field of view. Polygonal mirrors enable rapid scanning (1–4 kHz line rates) with adjustable speed. To a lesser extent, rotating polygonal mirrors and acousto-optic deflectors (AODs) are also used in laser scanning applications, and they present their own advantages and drawbacks. Also, resonant scanning is not performed at constant velocity, so illumination dwell time is not constant, resulting in non-uniform detection sensitivity across the region of interest. However, the fixed-frequency sinusoidal motion of resonant scanners impedes imaging at variable rates or random-access scanning (where only discrete portions of the field of view are scanned ). Resonant galvanometer-controlled mirrors are capable of much higher speeds than conventional galvanometric scanners, on the order of ~10 4 lines per second, enabling video rate or faster frame rates. For most moderate fields of view (FOVs), these mirror scanning systems have traditionally limited imaging frame rates to several Hz. Galvanometer-controlled mirrors are fundamentally speed limited by their size, inertia, and the requirement to slow down and reverse direction. Larger (~5mm) non-resonant galvanometers, traditionally used for slow scanning and step-stop operation, are very accurate and feature low settling times (100–300 μs) for small motions. Many modern laser scanning microscopy techniques use galvanometer-controlled mirrors to move the illumination beam relative to the sample. Regardless of the particular application, temporal resolution is often limited by choice of scanning hardware and scanning mechanism. Similarly, in light sheet microscopy, strict synchronization of the illumination beam with the camera’s rolling shutter enables real-time rejection of out-of-focus light. In rescan confocal microscopy, a super-resolution imaging technique, accurate synchronization of excitation and emission scanning is essential in order to extract sub-diffractive spatial information from the sample. For example, imaging at frame rates of tens to hundreds of Hz is necessary to capture functional dynamics in neural tissue. The ability to perform accurate, controllable, high speed scanning is fundamental to most of these methods. Imaging techniques now provide spatial resolution at or surpassing the diffraction limit, and temporal resolution down to the sub-millisecond level. Many applications in biomedical microscopy require imaging with high spatiotemporal resolution. This does not alter our adherence to PLOS ONE policies on sharing data and materials. is currently employed by Calico Life Sciences LLC. during preparation of the manuscript, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: Author A.G.Y. provided support in the form of salary for author A.G.Y. The work is made available under the Creative Commons CC0 public domain dedication.ĭata Availability: All values used to build graphs are available on figshare ( ).įunding: This work was supported by the National Institute of Biomedical Imaging and Bioengineering ( ) at the National Institutes of Health.
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This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. Received: Accepted: SeptemPublished: October 3, 2017 PLoS ONE 12(10):Įditor: Thomas Abraham, Pennsylvania State Hershey College of Medicine, UNITED STATES
Citation: Giannini JP, York AG, Shroff H (2017) Anticipating, measuring, and minimizing MEMS mirror scan error to improve laser scanning microscopy's speed and accuracy.
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