Classification of Condensers for Nikon Microscopes
The condenser of the microscope is mounted below the stage. Small optical microscopes often do not come with a condenser. A condenser is mandatory when using objectives with a numerical aperture above 0.40. The condenser compensates for insufficient light volume, appropriately modifies the properties of light from the light source, and focuses light onto the specimen to achieve optimal illumination.
Microscope condensers are available in various configurations, and the requirements for the condenser vary according to the numerical aperture of the objective lens.
① Abbe condenser Designed by Ernst Abbe, a German pioneer in optics, the Abbe condenser consists of two lenses. It offers good light-gathering performance, yet chromatic aberration and spherical aberration become obvious when the objective numerical aperture exceeds 0.60. Therefore, it is mostly used on general-purpose microscopes.
② Achromatic aplanatic condenser Also known as an achromatic and spherically corrected condenser or aplanatic condenser, this type is composed of a set of lenses. It provides excellent correction for chromatic and spherical aberration to deliver ideal images. It is one of the highest-quality condensers for brightfield microscopy, with an NA value up to 1.4. For this reason, it is commonly equipped on research-grade microscopes. It is not suitable for low-power objectives below 4×; otherwise the illumination cannot fill the entire field of view.
③ Swing-out condenser When low-power objectives (such as 4×) are used, the light cone formed by the light source cannot cover the large field of view, resulting in dark peripheral areas and only the central region being illuminated. To achieve full-field illumination, the upper lens of the condenser can be swung out of the optical path.
④ Other types of microscope condensers Apart from the brightfield condensers mentioned above, there are condensers designed for special applications, including darkfield condensers, phase contrast condensers, polarizing condensers, differential interference contrast (DIC) condensers, etc. These condensers match their corresponding observation methods respectively.
