Hoffman R, Gross L
Appl Opt. 1975 May 1;14(5):1169-76. doi: 10.1364/AO.14.001169.
A new microscope imaging system, modulation contrast, has been devised that reveals phase gradients; the image intensity is proportional to the first derivative of the optical density in the object. The modulator, a special filter, is placed in the Fourier plane, a plane conjugate with a slit aperture. The image of the slit aperture is registered within a gray region of the modulator; on one side of the gray region is a region of low transmittance and on the other side, a region of maximum transmittance. The modulator processes opposite gradients to produce opposite intensities, creating an optical shadowing effect. The dark region may be outside the optical system when the gray region is offset to the edge of the Fourier plane, to achieve maximum resolution. Modulation contrast is directional and capable of optical sectioning, revealing details without obscuring effects of structures above and below the plane of focus. The imaging theory of microscope optics has been extended to include effects of phase gradients. Phase gradients distribute the zero order across the Fourier plane. Intensity of the gradient's image is controlled by the zero order of the gradient diffraction pattern.
一种新的显微镜成像系统——调制对比度成像系统已被设计出来，它能揭示相位梯度；图像强度与物体光密度的一阶导数成正比。调制器是一种特殊的滤波器，放置在傅里叶平面上，该平面与狭缝孔径共轭。狭缝孔径的图像记录在调制器的灰色区域内；在灰色区域的一侧是低透射率区域，另一侧是最大透射率区域。调制器处理相反的梯度以产生相反的强度，从而产生光学阴影效果。当灰色区域偏移到傅里叶平面的边缘时，暗区可能在光学系统之外，以实现最大分辨率。调制对比度是有方向性的，并且能够进行光学切片，能够揭示细节而不会模糊焦点平面上方和下方结构的影响。显微镜光学的成像理论已得到扩展，以包括相位梯度的影响。相位梯度将零级分布在整个傅里叶平面上。梯度图像的强度由梯度衍射图案的零级控制。
