Modern compound microscopes operate using a dual stage magnifying design that incorporates a primary imaging lens, the objective, coupled to a secondary visualizing lens system known as the eyepiece or ocular mounted at the opposite ends of a body tube. The objective is responsible for primary image formation at varying magnifications, while the eyepiece is used to observe the image created by the objective. Advanced microscopes feature infinity optical systems that project a parallel bundle of wavefronts from the objective rear aperture to a tube or telan lens, which in turn focuses the image at the intermediate image plane in the eyepieces. The microscopist is able to observe a greatly enlarged virtual image of the specimen by peering through the eyepieces. Magnification is determined by multiplying the individual values of the objective and eyepiece. Resolution and contrast in optical microscopy are derived through a number of optical strategies and is strongly coupled to the types of reagents used to prepare the specimen. This section discusses the basic concepts necessary for a complete understanding of microscopy, including objectives, eyepieces, condensers, magnification, numerical aperture, resolution, contrast, and optical aberrations, along with a wide spectrum of additional considerations.
Textbooks on Basic Principles in Optical Microscopy - A list of the best textbooks that provide a general knowledge of the principles and practice of optical microscopy, as well as an introduction to contrast-enhancing techniques. The volumes listed here are useful in both the classroom and the research laboratory.
Microscope Optical Systems - The microscope optical train typically consists of an illuminator (including the light source and collector lens), a condenser, specimen, objective, eyepiece, and detector, which is either some form of camera or the observer's eye. These components are often supplemented with contrast-enhancing optical elements.
Specimen Contrast - Control of image contrast in a microscope optical system is dependent upon several factors, primarily the setting of aperture diaphragms, degree of aberration in the optical system, the optical contrast system employed, the type of specimen, and the optical detector.
Phase Contrast Microscopy - Phase contrast was introduced in the 1930's for testing of telescope mirrors, and was adapted by the Carl Zeiss laboratories into a commercial microscope for the first time several years later. The technique provides an excellent method of improving contrast in unstained biological specimens.
Differential Interference Contrast (DIC) Microscopy - Differential interference contrast converts gradients in specimen optical path length into amplitude differences that can be visualized as improved contrast in the resulting image. Images produced in DIC microscopy have a distinctive shadow-cast appearance
Fluorescence Microscopy - The application of fluorescence illumination and detection in optical microscopy has ushered in a wide range of advanced applications for live-cell imaging and in vivo observations. The articles tabulated in this section discuss the basic aspects of fluorescence, microscope configuration, fluorescent probes, software, light sources, detectors, objectives, filter sets, and a variety of other pertinent topics.
Polarized Light Microscopy - The polarized light microscope is designed to observe specimens that are visible due to their birefringent character. Polarizing microscopes must be equipped with a polarizer, positioned in the light path before the specimen, and an analyzer placed in the optical pathway between the objective rear aperture and the observation tubes or camera port.
Microscope Ergonomics - Although conventional microscope design has not necessarily been a problem for short-term use, long-term sessions have in the past created problems for scientists and technicians who used the instruments. Microscope operators often must assume an unusual and challenging position.