Microscope objectives are classified according to their use
The use of optical microscopes can be roughly divided into two categories: "biological use" and "industrial use". Objective lenses can also be divided into "biological" lenses and "industrial" lenses according to these two purposes. In biological applications, biological specimens are generally placed on glass slides and fixed with cover slips from above. Due to the need for biological objective lenses to observe samples through cover glass, an optical system design was adopted that takes into account the thickness of the cover glass (usually 0.17 mm). In industrial applications, observations are generally conducted without covering specimens such as metal mineral slices, semiconductor wafers, and electronic components. Therefore, the industrial objective lens adopts the optimal optical system design without a cover glass between the front end of the objective lens and the specimen.
Classify according to observation methods
Various observation methods have been developed based on the use of optical microscopes, and specialized objective lenses have also been developed to correspond to these observation methods. Objective lenses can be divided according to observation methods. For example, "reflective dark field objective lens (with a circular illumination path around the internal lens)", "differential interference objective lens (reduces internal distortion of the lens and optimizes the optical characteristics combination with the differential interference prism)", "fluorescence objective lens (improves transmittance in the near ultraviolet range)", "polarized light objective lens (greatly reduces internal distortion of the lens)", and "phase difference objective lens (with built-in phase plate)".
Classified by magnification
An optical microscope is equipped with multiple objective lenses on a device called an objective lens converter. In this way, as long as the objective lens converter is rotated, low magnification can be switched to high magnification, and magnification conversion can be easily completed. So generally, a set of objective lenses with different magnifications are installed on the objective lens converter. Therefore, the product lineup of objective lenses consists of low magnification (5 ×, 10 ×), medium magnification (20 ×, 50 ×), and high magnification (100 ×) objectives. Among them, especially in high magnification products, in order to obtain high-definition imaging, we have introduced a liquid immersion objective that fills the front end of the objective lens with a special liquid with high refractive index such as synthetic oil and water between the specimen and the sample. In addition, ultra-low magnification (1.25 ×, 2.5 ×) and ultra-high magnification (150 ×) objective lenses have been introduced for special purposes.
