Duan Yubo, Sheppard Colin J R, Rehman Shakil, Chen Nanguang
Opt Lett. 2014 Mar 15;39(6):1677-80. doi: 10.1364/OL.39.001677.
Focal modulation microscopy (FMM) has been demonstrated more effective than confocal microscopy for imaging of thick biological tissues. To improve its penetration depth further, we propose a simple analytical method to enlarge the modulation depth, the unique property of FMM directly linked to its signal-to-noise ratio. The modulation depth increases as the excitation intensity of the binary phase aperture status is pushed further away from the focal region of the detection optics, thereby creating a dark region in the focal volume, which we call maximally flat crater (MFC). By direct algebraic manipulation, MFCs are achieved for both scalar and vector diffraction optics. Numerical results show that the modulation depth from MFC is very close to the maximum values, with a small difference less than 3% for the same number of subapertures. Applications of bifocus produced by MFC apertures are also discussed.
聚焦调制显微镜（FMM）已被证明在对厚生物组织成像方面比共聚焦显微镜更有效。为了进一步提高其穿透深度，我们提出了一种简单的分析方法来增大调制深度，调制深度是FMM的独特属性，直接与其信噪比相关。随着二元相位孔径状态的激发强度进一步远离检测光学器件的焦区，调制深度增加，从而在焦体积中产生一个暗区，我们将其称为最大平坦坑（MFC）。通过直接代数运算，标量和矢量衍射光学器件均可实现MFC。数值结果表明，MFC产生的调制深度非常接近最大值，对于相同数量的子孔径，差异小于3%。还讨论了由MFC孔径产生的双焦点的应用。
