Protecting from incorrect treatment

The design of a microscope will often times (partially) excuse incorrect treatment. However, the front nosecone of the objective with the sensitive front lens element is one particularly critical area. A number of precautions should be taken to ensure the objective lens is not damaged. The entire front optics of objectives with a high magnification are (in most cases) contained in a resilient, spring loaded mount. When touched, this mount backs away slightly (Figure 4). However, the distance available for this movement is very small (approximately 2 3 millimeters). Therefore, make sure that you do not move the stage too far upwards while focusing. In such cases, the sample will press against the objective tip, and once the front lens cannot retreat any further, the outcome may be an expensive breakage of glass. Immersion objectives have an additional protection facility to the one described above. Some varieties can be locked in the topmost position by carefully turning the front lens group housing (nosecone). The objectives can thus be parked at a safe distance. On the other hand, the escape route described above is then no longer available, and if one tries to use the objective in this retracted mode, the image will be distorted and there will be the danger of the stage colliding with other objectives when the nosepiece turret is rotated.