A review of high-grade imaging of diatoms and radiolarians in light microscopy optical- and software-based techniques

Abstract

Several optical- and software-based techniques for light microscopy are presented, which can be suggested as suitable means for the enhancement of image quality in observations and photomicrography of 3D specimens, especially diatoms and radiolarians. Sandwich illumination techniques, condenser aperture reduction darkfield, condenser aperture reduction phase contrast, axial darkfield (luminance contrast), traditional incident light and monochromatic illumination techniques can be used for optical improvements of visible microscopic images. In photomicrography, the image quality and visual information can be enhanced further by several software-based post-processing procedures: stacking techniques for deep focus imaging and high dynamic range rendering (HDR), digitized brightfield and interference contrast, inverted and ultra-high contrast amplified brightfield imaging, creation of digital collages and 3D imaging (anaglyphe imagery). All in all, several parameters determining image quality can be improved by these means: depth of field (vertical resolution), 3D appearance, lateral resolution, contour sharpness, image contrast, degree of equalization and balance in brightness and contrast, also the perceptibility of fine structures in thick specimens and very bright or dark zones. Thus, superior results are achievable when compared with conventional techniques.

Keywords:

• diatoms
• radiolarians
• imaging
• illumination
• rendering
• techniques
• light microscopy

Acknowledgements

The author thanks Eberhard Raap and G. Göke for preparations of radiolarians and diatom shells and Timm Piper for the luminance contract image shown in Fig. 11b. The English version was reviewed by Linda Tennant.