Illumination Methods for the Stereomicroscope, Including Use of Colored Filters for Image Contrast Enhancement

Abstract

Stereo light microscopes (SLM) or dissecting microscopes are used in many different sciences, industries, and technologies. The objective for the SLM falls into two major categories: common main objective (CMO) using a single objective with prisms that split the image for each eye, and the Greenough style employing one microscope for each eye. In Europe, in the late 1800s, Carl Zeiss in conjunction with Otto Schott, designed a SLM using an Italian prism design that made images of the object correctly oriented. Two main illumination methods used with the SLM are transmitted and reflected light. Transmitted light illumination using a light source built into the base or with an attachable substage base utilizing an external light source. Some manufacturers provide additional illumination methods such as darkfield and polarizing light filters. Reflected illumination using visible light can be divided into five common illumination methods and two different ways to achieve fluorescent illumination. After a brief discussion of types of filters and sources, practical application of reflected light with the SLM substage attachable base with diffuse reflector and colored filters is shown to enhance visibility of certain colored particles while minimizing the visibility of unwanted colored particles.