PACINI MONOCULAR COMPOUND MICROSCOPE Filippo Pacini was an Italian instrument maker who excelled in microscope design and construction during the mid nineteenth century. The microscope illustrated below is an example of the microscopes produced by Pacini. An original version of the microscope was photographed and described by Gerard Turner in his book Catalogue of Microscopes. The base is a flat semi-circular brass plate, similar to another Pacini microscope featured in the museum, supported by three short tapered feet, with the limb and two large columns emerging from the flat surface. This version has longer feet than its cousin, the rotatable stage is not divided, and the eyetube/ocular combination is much shorter. In addition, this Pacini model has an Amici prism with an aperture on a hinged brass arm that protrudes from the front of the stage. An oval stage housing is positioned at the top of the columns and has plenty of room to accommodate a wide spectrum of specimens. The back portion of the stage is supported by a large rectangular brass limb, which contains a trapeze-sectioned bar carrying the arm to which the body tube is attached. Read the rest of this entry »

Andrew Ross Monocular Compound Microscope Andrew Ross was a skilled English optician who crafted the monocular compound microscope sometime between 1841 and 1842. The illustration of the instrument provided was drawn from photographs of the original microscope, which was described by Gerard Turner in The Great Age of the Microscope. A compass joint with a clamping screw holds the limb of the brass Ross microscope to the instrument’s short pillar and base. A bearing at the end of the pillar enables rotation and inclination of the instrument. The optical system of the microscope consists of a Huygenian eyepiece and an unsigned objective that was inspired by the achromatic lens designs of Joseph Lister. Attached to the lower part of the microscope’s limb by a brass bar, a plano-concave mirror may be adjusted to gather light. The Ross microscope also features a mechanical stage with an upper plate that rotates and slides as needed. Beneath the stage, a three-aperture rotating disc facilitates control of specimen contrast, resolution, and illumination. Read the rest of this entry »

MONOCULAR COMPOUND MICROSCOPE This simple monocular compound microscope, whose maker is unknown, was produced sometime around 1860. The model featured below was redrawn from photographs of the original microscope, which is part of the Billings microscope collection at Walter Reed Army Hospital in Washington DC. The turned wooden base is approximately two and a half inches in diameter and supports a solid brass pillar that is screwed into the base. A washer-shaped brass stage is attached to the pillar beneath the body tube, which is also made of brass. There is a single eyepiece, with two convex lenses, and an objective screwed into the nosepiece. S.J. RIENKS MONOCULAR COMPOUND MICROSCOPE This brass microscope was made in Holland and is signed “S. J. Rienks, Friesland, 1825″. The model featured below was redrawn from photographs of the original microscope, which is part of the Billings microscope collection at Walter Reed Army Hospital in Washington DC. This unusual microscope is constructed according to the design of the Dr. Robert Smith reflecting microscope with a folding telescopic tripod base. Dr. Smith was an English instrument maker and author of System of Optics, published in London in 1738. Read the rest of this entry »

The nineteenth century witnessed vast improvements in microscope design and function. Objectives and condensers were being built with multiple lenses that had increasing degrees of optical correction. Photomicrography made its debut in mid-century and by the end of the nineteenth century, high-end microscopes performed better than many student models produced today. The first part of the nineteenth century witnessed dramatic improvements in optics with the introduction of achromatic objectives by van Deijl, Amici, and Lister that also raised numerical apertures to around 0.65 for dry objectives and up to 1.25 for homogeneous immersion objectives. Innovations in machine tooling led to greatly improved design and construction of the microscope’s mechanical elements and many well-crafted instruments appeared by designers such as Beck, Chevalier, Nachet, Leitz, Powell & Lealand, Ross, and Zeiss. In 1886, Ernst Abbe’s work with Carl Zeiss led to the production of apochromatic objectives based, for the first time, on sound optical principles and lens design. These advanced objectives provided images with reduced spherical aberration and free of color distortions (chromatic aberration) at high numerical apertures. At the end of the century, in 1893, Professor August Köhler reported a method of illumination, which he developed to optimize photomicrography, allowing microscopists to take full advantage of the resolving power of Abbe’s objectives. The last decade of the nineteenth century saw innovations in optical microscopy, including metallographic microscopes, anastigmatic photolenses, binocular microscopes with image-erecting prisms, and the first stereomicroscope. Read the rest of this entry »

INTRODUCTION TO MICROSCOPY Microscopes are instruments designed to produce magnified visual or photographic images of objects too small to be seen with the naked eye. The microscope must accomplish three tasks: produce a magnified image of the specimen, separate the details in the image, and render the details visible to the human eye or camera. This group of instruments includes not only multiple-lens (compound microscopes) designs with objectives and condensers, but also very simple single lens instruments that are often hand-held, such as a loupe or magnifying glass. The microscope that was invented by British microscopist Robert Hooke sometime in the 1660s is a simple compound microscope. This beautifully crafted microscope has an objective lens near the specimen and is focused by turning the body of the microscope to move the objective closer to or farther from the specimen. Read the rest of this entry »