User Guide

490 Series Microscope
AmScope Proprietary Page 19 of 64
2.16 Using Darkfield Condenser Lenses (Optional Accessories)
Darkfield Illumination is a lighting method for increasing contrast. A darkfield
condenser lens produces bright images against a dark background for low contrast
specimens.
The dry darkfield condenser is for low power magnifications,
such as with the 4X, 10X or 40X objective lenses, with
numeric apertures of .65 or less.
The oil darkfield condenser is for high power magnifications,
the 40X and 100X objective lenses, with numeric apertures
up to 1.25 or less.
2.16.1 Installing a Darkfield Condenser Lens
1. Use the condenser lens adjustment knob to lower the condenser so you have
easy access to the condenser knob.
2. Loosen the condenser lock screw and replace the
condenser lens.
3. Install the darkfield condenser lens and tighten the
condenser lock thumb screw on the condenser holder.
When choosing a darkfield condenser, be sure the
condenser’s numerical aperture is larger than the
numerical aperture of the objective lens.
If the objective lens aperture is larger than the aperture of
the darkfield condenser, direct light will be transmitted and
a darkfield will not be achieved.