Perfect oblique illumination

Oblique illumination certainly is the oldest method to enhance contrast in microscopy and is a technique of interference contrast. This work provides an overview about its origins, historical development and theory. Oblique illumination was a key to the theory of microscopic resolution. During development of the modern illumination of the microscope, oblique illumination was abandoned, and rediscovered in the second half of the 20th century. Oblique illumination with aperture diaphragms provides improved relief contrast, but does not change resolution. Fourier optics explains well oblique illumination and its unwanted effects resulting from non-optimal adjustment, like broad lights and shadows. The work describes optimal adjustment of oblique

illumination with best results in digital photomicrography.

Keywords: Oblique illumination – resolution of the microscope – Fourier optics – diffraction – interference contrast

Bauer, T. Die perfekte schiefe Beleuchtung. Mikroskopie 4/2020. Dustri Verlag.