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Condenser (optics) A condenser is an optical lens that renders a divergent light beam from a point light source into a parallel or converging beam to illuminate an object to be imaged. Condensers are an essential part of any imaging device, such as microscopes, enlargers, slide projectors, and telescopes. The concept is applicable to all kinds ...
Scientist using an optical microscope in a laboratory. The optical microscope, also referred to as a light microscope, is a type of microscopethat commonly uses visible lightand a system of lensesto generate magnified images of small objects. Optical microscopes are the oldest design of microscope and were possibly invented in their present ...
Phase-contrast microscopy (PCM) is an optical microscopy technique that converts phase shifts in light passing through a transparent specimen to brightness changes in the image. Phase shifts themselves are invisible, but become visible when shown as brightness variations. When light waves travel through a medium other than a vacuum, interaction ...
Köhler illumination is a method of specimen illumination used for transmitted and reflected light (trans- and epi-illuminated) optical microscopy. Köhler illumination acts to generate an even illumination of the sample and ensures that an image of the illumination source (for example a halogen lamp filament) is not visible in the resulting image.
Bright-field microscopy ( BF) is the simplest of all the optical microscopy illumination techniques. Sample illumination is transmitted (i.e., illuminated from below and observed from above) white light, and contrast in the sample is caused by attenuation of the transmitted light in dense areas of the sample.
Dark-field microscopy (also called dark-ground microscopy) describes microscopy methods, in both light and electron microscopy, which exclude the unscattered beam from the image. Consequently, the field around the specimen (i.e., where there is no specimen to scatter the beam) is generally dark. In optical microscopes a darkfield condenser lens ...
When used in a compound microscope, the light must be directed from below and parallel to the optical axis. Thus, the illumination is different from the conventional Köhler illumination setup, where a condenser forms a light cone with the specimen at its focus. Instead, light passing laterally past the specimen is reflected at the Lieberkühn ...
Transmission electron microscopy ( TEM) is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. The specimen is most often an ultrathin section less than 100 nm thick or a suspension on a grid. An image is formed from the interaction of the electrons with the sample as the beam is transmitted ...