Levenhuk 850B Binocular Microscope is ideal for biochemical, pathologo-anatomic, cytologic, hematologic, urologic, dermatologic, biologic, and general clinical research in laboratories of any medical institution. It allows examinations using both bright field and dark field methods.
It also features a binocular rotatable nosepiece. Its revolving head allows positioning of four objectives, is inclined at 30 degrees and rotates 360 degrees around its axis. The microscope features the classic Koehler illumination system, with field and aperture diaphragm adjustment.
The focusing mechanism features integrated coarse- and fine-adjustment screws. Focus accuracy is achieved due to the vertical move of the stage relative to the fixed objective with use of focusing handles. Bi-coordinate stage can move in horizontal and vertical directions. The stage dimensions are 140x155 mm (5.5x6.1 in). The focusing mechanism and stage move smoothly, without jerks or backlash. Increment is 25 mm (1 in) for coarse focusing and 0.002 mm (0.00008 in) for fine focusing.
The microscope’s illumination system includes a halogen lamp 6V/20W, with smooth brightness adjustment.
The microscope is equipped with a build-in dark field condenser, which works while the Abbe condenser is at full length upwards. To run it, rotate the illumination ring counterclockwise until you achieve the desired result. When turning it clockwise, you will return to the bright field. The method of dark field in the transmitted light is used to get images of transparent objects that are invisible when using the bright field method. This method is widespread, for instance in in hemoscanning, a unique method of blood examination.
About the dark field method:
When the light is coming out of the condenser, the main part of light rays have not changed their direction while coming through the transparent specimen, so they form a beam in the shape of a hollow cone and do not reach the objective (located inside of this cone).
The observed image is formed in the microscope with help of just a small part of rays that have been dispersed into the cone by the specimen micro particles and then passed through the objective. As a result, bright images of the specimen structure elements whose refractive index differs from the environment are visible in the field of view against the dark background. For large particles, only brighter edges dispersing the light rays are visible.