Zeiss Standard 25 ICS Operating Manual

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Zeiss Standard 25 ICS Operating Manual Manual pdf 36 page image

Standard 25 ICS3-8 B 40-029 e 01/983.4 Setting of transmitted-light darkfieldDarkfield is mainly used for small or minute objects such as treponema, spirochaeta, cilia and bacteria,but also for emulsions or unstained objects in watery solutions.The special benefit of the darkfield technique is its natural, true rendition of the original colors (colorfidelity).The equipment required for darkfield always includes a condenser with central stop, the numericalaperture of which exceeds that of the objective used. For further details please see the following table.Condenser with illumination aperture suitable objective aperturesPh condenser II Z 0.9 in position Ph 3 0.44Ph condenser II Z 0.9 in position D 0.6/0.9) 0.40.4 -0.55dry darkfield condenser 0.7 - 0.85on condenser holder Z0.4 - 0.6dry darkfield condenser 0.8 - 0.95on condenser holder Z0.6 - 0.75Ultracondenser 1.2 - 1.4on condenser holder Z0.75 - 1.0Higher objective magnifications or apertures require objectives with an integrated iris aperture.As described in chapter 2, the microscope is ready for operation and switched on according to section3.1.The microscope must be set for transmitted-light brightfield, as described in section 3.2.Settings: Correct condenser height until image background appears in optimum darkness. Checking the objective pupil reveals whether it is dark indeed; for this purpose, remove the eyepiecefrom the tube and view the objective exit pupil. Setting of darkfield is made easier by performing precentration using an objective of a lower power.Since the luminous field is visible only where particles light up, while the final specimen, however,might be "empty" over large areas, we would recommend you to use a specimen for initial settingwhich features a homogeneous distribution of details, e.g. a blood smear.Darkfield microscopy requires specimens and optical surfaces to be extremely clean. Fingerprints and traces of grease in particular have negative effects, since they brighten thebackground of the field of view.