Compound Microscopes

Introduction Light Paths Linear Approximation Pros and Cons


Compound microscope is an optical instrument which is used to obtain high magnification. It is an extension of the magnifying glass which are used to see very small things. The magnifying power of a simple lens is very limited. It is difficult to get a magnification better than a few times without using a highly curved lens with a high refractive index. This kind of lens will have a lot of aberrations that one can not see the image clearly. Therefore, we used two or more lenses which builds up the compound microscope.

The Parts of the microscope

In our course, we are mainly learning how the light travels through a lens system. Therefore, let's look at the most important components of the microscopic lens system, which are the Eyepiece and the Objective Lenses, of the microscope and see how light travels into the system.

The Eyepiece

Usually an eyepiece involves two or more lenses build up the piece. The eyepiece is designed to ensure that the image is conjugate. This means that the rays entering the eye from any one point on the object are parallel. Various eyepiece designs are available, each with its advantages and disadvantages. The diagram shows a normal two lenses eyepiece.

Objective Lens

The objective is the most important component of the optical system in terms of the quality of the final image. Most of the compound microscopes have three objective lenses that you can switch around, each with different maginifying power. In the 1870s, Ernst Abbe's introduced apochromatic corrections help made the best objectives capable of resolving the finest detail predicted by theory. The diagram shows the construction of an objective lens.
Introduction Light Paths Linear Approximation Pros and Cons

By James Chien-Chih Yeh 73976995