Bernet Stefan, Harm Walter, Jesacher Alexander, Ritsch-Marte Monika
Division for Biomedical Physics, Innsbruck Medical University, A-6020 Innsbruck, Austria.
Opt Express. 2011 Dec 5;19(25):25113-24. doi: 10.1364/OE.19.025113.
Microscopic imaging with a setup consisting of a pseudo-random phase mask, and an open CMOS camera, without an imaging objective, is demonstrated. The pseudo random phase mask acts as a diffuser for an incoming laser beam, scattering a speckle pattern to a CMOS chip, which is recorded once as a reference. A sample which is afterwards inserted somewhere in the optical beam path changes the speckle pattern. A single (non-iterative) image processing step, comparing the modified speckle pattern with the previously recorded one, generates a sharp image of the sample. After a first calibration the method works in real-time and allows quantitative imaging of complex (amplitude and phase) samples in an extended three-dimensional volume. Since no lenses are used, the method is free from lens abberations. Compared to standard inline holography the diffuse sample illumination improves the axial sectioning capability by increasing the effective numerical aperture in the illumination path, and it suppresses the undesired so-called twin images. For demonstration, a high resolution spatial light modulator (SLM) is programmed to act as the pseudo-random phase mask. We show experimental results, imaging microscopic biological samples, e.g. insects, within an extended volume at a distance of 15 cm with a transverse and longitudinal resolution of about 60 μm and 400 μm, respectively.
本文展示了一种微观成像方法，该方法采用由伪随机相位掩膜和开放式互补金属氧化物半导体（CMOS）相机组成的装置，且不使用成像物镜。伪随机相位掩膜充当入射激光束的散射器，将散斑图案散射到CMOS芯片上，该图案被记录一次作为参考。随后，在光束路径中的某个位置插入的样品会改变散斑图案。通过将修改后的散斑图案与先前记录的图案进行比较这一单一（非迭代）图像处理步骤，可生成样品的清晰图像。经过首次校准后，该方法可实时工作，并能对扩展三维体积内的复杂（幅度和相位）样品进行定量成像。由于未使用透镜，该方法不存在透镜像差。与标准同轴全息术相比，漫射样品照明通过增加照明路径中的有效数值孔径来提高轴向切片能力，并抑制不需要的所谓孪生图像。为进行演示，对高分辨率空间光调制器（SLM）进行编程，使其充当伪随机相位掩膜。我们展示了实验结果，即对微观生物样品（如昆虫）进行成像，在15厘米的距离处，在扩展体积内，横向分辨率约为60微米，纵向分辨率约为400微米。
