Step-by-step guide to reduce spatial coherence of laser light using a rotating ground glass diffuser
Step-by-step guide to reduce spatial coherence of laser light using a rotating ground glass diffuser
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DOI：
10.1364/ao.56.005427
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发表时间：
2017-07-01
期刊：
影响因子：
1.9
通讯作者：
Andersson, Magnus
中科院分区：
文献类型：
--
作者：
Stangner, Tim;Zhang, Hanqing;Andersson, Magnus
在显微镜中快速过程的宽视场成像需要高的光强度，这促使使用激光作为光源。然而，由于其长的空间相干长度，激光器不适合这种应用，因为它们产生相干噪声和寄生反射，例如散斑，降低图像质量。因此，我们提供了一个分步指南，用于构建一个无散斑和高对比度的激光照明设置使用旋转毛玻璃扩散器由步进电机驱动。该装置易于构建，价格便宜，并且允许48%的显著光通量，与报道的装置中常用的单个透镜收集器相比高出40%。这是通过仅使用一个物镜来收集来自毛玻璃漫射器的散射光来实现的。我们验证我们的设置在图像质量，散斑对比度，电机引起的振动，和光通量。为了突出后者，我们记录布朗运动的微粒使用100倍油浸物镜和高速摄像机在2000赫兹的激光输出功率只有22毫瓦。此外，通过将物镜放大倍率降低到50倍，可实现高达10，000 Hz的采样率。为了帮助具有基本或高级光学知识的读者实现此设置，我们提供了完整的组件列表，3D打印CAD文件，设置协议和运行步进电机的代码。(C)2017美国光学学会。
Wide field-of-view imaging of fast processes in a microscope requires high light intensities motivating the use of lasers as light sources. However, due to their long spatial coherence length, lasers are inappropriate for such applications, as they produce coherent noise and parasitic reflections, such as speckle, degrading image quality. Therefore, we provide a step-by-step guide for constructing a speckle-free and high-contrast laser illumination setup using a rotating ground glass diffuser driven by a stepper motor. The setup is easy to build, cheap, and allows a significant light throughput of 48%, which is 40% higher in comparison to a single lens collector commonly used in reported setups. This is achieved by using only one objective to collect the scattered light from the ground glass diffuser. We validate our setup in terms of image quality, speckle contrast, motor-induced vibrations, and light throughput. To highlight the latter, we record Brownian motion of micro-particles using a 100x oil immersion objective and a high-speed camera operating at 2000 Hz with a laser output power of only 22 mW. Moreover, by reducing the objective magnification to 50x, sampling rates up to 10,000 Hz are realized. To help readers with basic or advanced optics knowledge realize this setup, we provide a full component list, 3D-printing CAD files, setup protocol, and the code for running the stepper motor. (C) 2017 Optical Society of America.