Achromatic microscope of variable magnifying power by G. Oberhauser
Achromatic microscope of variable magnifying power by G. Oberhauser, one o.g., one eyepiece, stage forceps
This is a later form of the microscope introduced by Oberhauser about 1830. The main differences between this and earlier models are the introduction of a rack focusing for the body tube and eyepiece, and the absence of a fine adjustment acting on the limb.
The base is of the heavy 'drum' form and mounted on it is a heavy brass plate which serves as the stage and is capable of rotation about the optic axis of the instrument. This plate supports the limb which carries the body on a bracket.
The body consists of two tubes, the outer one of which is fitted at its lower end with an achromatic objective. Into the lower end of the inner tube fits a lens combination consisting of two achromatic doublets separated by about one in., and into the upper end fits the eyepiece. This consists of two plano-convex lenses of about 2in. focus separated by about 1 3/4in., the convex surfaces being directed towards the object. Extension of the body-tube results in an increase in the magnification obtainable with a given objective.
The mirror fitted inside the drum serves to illuminate transparent objects and is plane and concave.