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. Research-level microscopes also contain one or more of several light-conditioning devices that are often positioned between the illuminator and condenser, and a complementary detector or filtering device that is inserted between the objective and the eyepiece or camera. The conditioning device(s) and detector work together to modify image contrast as a function of spatial frequency, phase, polarization, absorption, fluorescence, off-axis illumination, and/or other properties of the specimen and illumination technique. Even without the addition of specific devices to condition illumination and filter image-forming waves, some degree of natural filtering occurs with even the most basic microscope configuration.
Choosing objective lenses: The importance of numerical aperture and magnification in digital optical microscopy. Biological Bulletin 195: 1-4 (1998). A comprehensive discussion of microscope objectives focused on the critical aspects of objectives for imaging. Included are basics of image formation and an overview of objectives for widefield and confocal fluorescence microscopy.
Basic principles of microscope objectives. BioTechniques 33: 772-781 (2002). The authors describe the properties of microscope objectives, including resolution and numerical aperture, effects of design on magnification factors, correction for various degrees of aberration, infinity optical systems, and oil immersion fundamentals.
Proper alignment of the microscope. Methods in Cell Biology 56: 135-146 (1998). Addressed in this book chapter are the key components of optical microscopes and alignment for Köhler illumination. Among the topics discussed are the light source and collector, diffusers, condensers, stages, objectives, nosepiece, tube lens, eyepieces, and video adapters.
Microscope Basics. Methods in Cell Biology 81: 1-10 (2007). Drs. Sluder and Nordberg review finite and infinity microscope optical systems, objectives (including mixing and matching), coverslip selection, empty magnification, camera pixel number and resolution, mounting cameras on the microscope, and many of the basic fundamentals of digital cameras.
Microscopy overview. Encyclopedia of Analytical Science: 32-41 (2005). The authors provide a comprehensive review of all phases of the optical microscope. Addressed are lenses, magnification, simple and compound microscopes, numerical aperture, illumination, reflected light microscopy, diffraction, resolution, aberrations, contrast, confocal microscopy, and limitations of the microscope.
Optical Microscopy Encyclopedia of Imaging Science and Technology 2:1106-1140 (2002). A thorough review of microscope optical systems and contrast-enhancing techniques. Eyepieces, condensers, and objectives are discussed in detail, as are finite and infinity optical systems. Included contrast techniques are phase, DIC, polarized light, Hoffman modulation contrast, and fluorescence.
The compound microscope: Optical tube length or parfocalization? European Journal of Physics 26: 1101-1105 (2005). A theoretical study of standardized distances in compound microscopes. The authors examine the optical tube length with regards to requirements of parfocalization and discuss the German and Japanese industry standards employed for standardization of specimen-to-intermediate image distance.
Optical Microscopy. Encyclopedia of Condensed Matter Physics: 175-182 (2005). A thorough review of microscope system optical components, including light sources, condensers, filters, objectives, eyepieces, the stage, stand, resolution, and depth of field. Also covered are various imaging modes, such as brightfield, oblique illumination, darkfield, polarized light, and DIC microscopy.
The development of the microscope objective. Journal of the Optical Society of America 33: 123-128 (1943). Largely of historical interest, this review describes the invention of the microscope, early developments in lens design, correction for chromatic aberration, increasing numerical aperture, immersion objectives, and early progress in the design of apochromatic objectives.
Microscopy and Micrometry Methods in Microbiology 5: 1-103 (1971). A comprehensive 100-page review on all aspects of microscopy, including light and color, magnification, Abbe theory, image formation, resolution, depth of focus, objectives, eyepieces, and condensers, and configuration for illumination. Phase contrast is described in detail as are making measurements with stage micrometers and reticules.