de Leon Erich E, Brownlee Jonathan W, Gelsinger-Austin Paul, Kostuk Raymond K
College of Optical Sciences, University of Arizona, Tucson, Arizona 85721, USA.
Appl Opt. 2012 Oct 10;51(29):6952-61. doi: 10.1364/AO.51.006952.
Confocal microscopy rejects out-of-focus light from the object by scanning a pinhole through the image and reconstructing the image point by point. Volume holographic imaging systems with bright-field illumination have been proposed as an alternative to conventional confocal-type microscopes that does not require scanning of a pinhole or a slit. However, due to wavelength-position degeneracy of the hologram, the high Bragg selectivity of the volume hologram is not utilized and system performance is not optimized. Confocal-rainbow illumination has been proposed as a means to remove the degeneracy and improve optical sectioning in these systems. In prior work, two versions of this system were illustrated: the first version had a separate illumination and imaging grating and the second used a single grating to disperse the incident light and to separate wavelengths in the imaging path. The initial illustration of the dual-grating system has limited depth resolution due to the low selectivity of the illumination grating. The initial illustration of the single-grating system has high depth resolution but does not allow optimization of the illumination path and requires high optical quality of the holographic filters. In this paper we consider the design and tolerance requirements of the dual-grating system for high depth resolution and demonstrate the results with an experimental system. An experimental system with two 1.8 mm thick planar holograms achieved a depth resolution of 7 μm with a field of view of 1.9 mm and a hologram dispersion matching tolerance of ±0.008°.
共聚焦显微镜通过在图像上扫描针孔并逐点重建图像来排除来自物体的离焦光。已提出具有明场照明的体积全息成像系统作为传统共聚焦型显微镜的替代方案，该系统不需要扫描针孔或狭缝。然而，由于全息图的波长 - 位置简并性，体积全息图的高布拉格选择性未被利用，系统性能未得到优化。已提出共聚焦 - 彩虹照明作为消除这些系统中的简并性并改善光学切片的一种方法。在先前的工作中，展示了该系统的两个版本：第一个版本有单独的照明光栅和成像光栅，第二个版本使用单个光栅来分散入射光并在成像路径中分离波长。双光栅系统的最初展示由于照明光栅的低选择性而具有有限的深度分辨率。单光栅系统的最初展示具有高深度分辨率，但不允许优化照明路径，并且需要全息滤波器具有高光学质量。在本文中，我们考虑了用于高深度分辨率的双光栅系统的设计和公差要求，并用一个实验系统展示了结果。一个带有两个1.8毫米厚平面全息图的实验系统实现了7微米的深度分辨率，视场为1.9毫米，全息图色散匹配公差为±0.008°。
