Colloid particles in additively colored CaF2 crystal

A series of natural color wide-field microscopic views obtained while refocusing/submerging into the additively-colored CaF2 crystal. The LSM images show the presence of relatively large colloids. Many of them have visible radii of about 0.1 µm that is likely to be due to diffraction limit, while their real size may be a bit smaller. The microstructure of additively colored sample was visualized in transmitted and reflected light of 405 nm laser using Zeiss LSM-710 laser scanning microscope (LSM) with dry 50x/0.95 and oil immersion 40x1.3 objective lenses, the wavelength at the shortest border of the visible range and large numerical aperture chosen to improve spatial resolution. With the pinhole of the confocal microscope, the out-of-focus reflected light is filtered out, thus providing the depth of field – optical slice thickness – as small as 0.3 µm, and lateral spatial resolution down to 0.15 µm, but only in reflection mode. The resolution of the transmitted-light image (0.2 µm lateral, 0.6 µm axial) is limited by numerical aperture 0.9 of the condenser that serves as an objective lens.