Classification of special objective lenses for metallographic microscopes
Special objective lenses are specially designed and manufactured to achieve certain specific observation effects. They mainly include the following types:
1. Correction collar objective: There is an adjustment ring installed in the middle of the objective lens. When the adjustment ring is turned, the distance between the lens groups in the objective lens can be adjusted, thereby correcting the error caused by the non-standard thickness of the cover glass. Poor coverage. The scale on the adjustment ring can range from 0.11--.023, and this number is also marked on the outer shell of the objective lens, indicating that the error in the thickness of the cover glass can be corrected from 0.11-0.23mm.
2. Objective lens with iridescent diaphragm (Iris diaphragm objective): The iridescent diaphragm is installed in the upper part of the objective lens barrel, and the adjustment ring can also be rotated on the outside. When rotating, the size of the aperture of the aperture can be adjusted. The objective lens with this structure is The purpose of the unique oil immersion objective lens is that during dark field microscopic examination, the background of the field of view is not dark enough, resulting in a decrease in the quality of the microscopic examination. At this time, adjust the size of the aperture to darken the background, make the inspected object brighter, and enhance the microscope inspection effect.
3. Phase contrast objective: This objective is a special objective used for phase contrast microscopy. Its characteristic is that a phase plate is installed at the rear focal plane of the objective.
4. Nocover objective: Some objects to be inspected cannot be covered with a cover glass, so a coverless objective should be used during microscopic examination, otherwise the image quality will be significantly reduced, especially during high-power microscopic examination. . The outer shell of this kind of objective lens is often marked with NC. At the same time, there is no word 0.17 on the thickness of the cover glass, but "0" is marked on it.
5. Long working distance objective lens: The focal length of this objective lens is larger than that of ordinary objective lenses. It is designed to meet the microscopic examination of liquid materials (high temperature metallography), liquid crystals, tissue culture, suspensions and other materials.
