A simple but precise method for quantitative measurement of the quality of the laser focus in a scanning optical microscope.
A simple but precise method for quantitative measurement of the quality of the laser focus in a scanning optical microscope.
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DOI：
10.1111/jmi.12249
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发表时间：
2015-07
影响因子：
2
通讯作者：
McConnell G
中科院分区：
文献类型：
--
作者：
Trägårdh J;Macrae K;Travis C;Amor R;Norris G;Wilson SH;Oppo GL;McConnell G
本文报道了一种在激光扫描显微镜中表征出射物镜的聚焦激光束的方法。该方法提供了光学焦点的大小、光束的发散度、椭圆率和像散。我们使用一个显微尺度的刀口，其形式是一个简单的透射电子显微镜网格连接到玻璃显微镜载玻片上，以及一个集光光纤和样品下面的光电二极管。通过从栅格的反射部分到透射部分扫描激光光斑，可以获得误差函数形式的光束轮廓，并且通过用相对于束腰的不同轴向位置处的刀刃重复该过程，可以获得后物镜激光束的发散度和像散度。所测量的发散度可以用于量化在实践中使用了透镜的多少全数值孔径。我们目前的数据的光束半径，光束发散度，椭圆度和像散获得低（0.15，0.7）和高（1.3）数值孔径透镜和激光共焦和多光子激光扫描显微镜中常用的。我们的刀口法与显微镜中使用的其他刀口法相比具有几个优势，包括刀口易于制备，光束也可以直接在盖玻片下进行表征，必要时可以减少设计用于盖玻片的物镜的球面像差，并且适合与商业激光扫描显微镜一起使用，其中激光束的访问可能受到限制。
We report a method for characterizing the focussing laser beam exiting the objective in a laser scanning microscope. This method provides the size of the optical focus, the divergence of the beam, the ellipticity and the astigmatism. We use a microscopic‐scale knife edge in the form of a simple transmission electron microscopy grid attached to a glass microscope slide, and a light‐collecting optical fibre and photodiode underneath the specimen. By scanning the laser spot from a reflective to a transmitting part of the grid, a beam profile in the form of an error function can be obtained and by repeating this with the knife edge at different axial positions relative to the beam waist, the divergence and astigmatism of the postobjective laser beam can be obtained. The measured divergence can be used to quantify how much of the full numerical aperture of the lens is used in practice. We present data of the beam radius, beam divergence, ellipticity and astigmatism obtained with low (0.15, 0.7) and high (1.3) numerical aperture lenses and lasers commonly used in confocal and multiphoton laser scanning microscopy. Our knife‐edge method has several advantages over alternative knife‐edge methods used in microscopy including that the knife edge is easy to prepare, that the beam can be characterized also directly under a cover slip, as necessary to reduce spherical aberrations for objectives designed to be used with a cover slip, and it is suitable for use with commercial laser scanning microscopes where access to the laser beam can be limited.