Video and UV microscopy

Video microscopy utilizes video cameras and CCDs for the improvement of the conventional light microscope. In connection with electronic image processors, resolution thus can be more than doubled and small cytoplasmic details like Golgi vesicles and thin elements of endoplasmic reticulum, which so far were known only from pictures of the electron microscope, can be observed in the living cell.

Resolution is enhanced either by reduction of the wave length of the microscope illumination, i.e. by the use of ultraviolet (UV) light, leading to UV microscopy, or by the complete opening of the condensor diaphragm, allowing for bright-field and differential interference contrast with highest possible numerical apertures in condensor and objective; the contrast, which in the conventional light microscope is gained by closing the condensor iris, in this case is generated by the video camera and image processor, wherefore this technique is referred to as Video Enhanced Contrast or VEC microscopy. Video intensification of weak optical signals from the fluorescence microscope (Video Intensified Fluorescence or VIF microscopy) is facilitated by low-light-level cameras and CCDs which in combination with an image processor generate excellent images. Thus, even weakly fluorescent moving structures of living cells can be monitored and visualized on a monitor screen.

UV microscopy

A bright-field microscope equipped with a monochromator and with collector, condensor and objective lenses all made from quartz is operated with light of 280-360 nm wavelength. The image is picked up by a UV-sensitive video camera. The resolution thus is more than doubled, and in addition the contrast is very good, due to the absorption by proteins and DNA in the UV range. Cells, however, are sensitive to UV light and observation time therefore is limited. In addition, cells with UV-absorbing content in cell wall or vacuole cannot be observed.

VEC microscopy

In bright field and differential interference contrast (DIC) microscopy, contrast usually is generated by closing the aperture diaphragm in the condenser. This reduces the numerical aperture of both condenser and objective and hence also resolution. When the image is picked up by a high-resolution video camera or CCD, contrast can be gained electronically, wherefore resolutions similar to the UV microscope can be achieved. In combination with an image processor, the quality of the image is further improved (e.g. by electronic contrast enhancement, signal/noise reduction, background subtraction).

VIF microscopy

Weak fluorescence signals are amplified by the use of low light sensitive video cameras and CCDs; in combination with further improvement by an image processor they give excellent pictures of small structures. Less dye is needed, wherefore the fluorescence intensity is weaker, and out-of-focus details remain invisible; in addition, this allows for three-dimensional analysis of the object.