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The development of optical lens coating and the classification of microscope filters
Optical lens coating and its development, whether it is spectacle lenses made of inorganic or organic materials, in daily use, due to friction with dust or grit (silicon oxide) will cause the lens to wear and scratches on the surface of the lens. mark. Compared with glass flakes, organic materials have lower hardness and are more prone to scratches. Through the microscope, we can observe that the scratches on the lens surface are mainly divided into two types. One is the scratches caused by grit, which is shallow and small, and it is not easy for the wearer to detect; the other is the scratches caused by the larger grit. , Deep and rough periphery, in the center area will affect vision.
Anti-wear film began in the early 1970s, when it was thought that glass lenses were not easy to grind because of their hardness High, while the organic lens is too soft and easy to wear. Therefore, the quartz material is plated on the surface of the organic lens under vacuum conditions to form a very hard anti-wear lens design damage film, but due to the mismatch between its thermal expansion coefficient and the base material, it is easy to peel off and the film is brittle , So the anti-wear effect is not ideal.
The most important thing in modern anti-wear coating technology is the immersion method, that is, the lens is immersed in a hardened liquid after multiple cleanings, and after a certain time, at a certain speed Filed. This speed is related to the viscosity of the hardening fluid and plays a decisive role in the thickness of the anti-wear film. After lifting, polymerize in an oven at about 100°C for 4 to 5 hours, and the coating thickness is about 3 to 5 microns.
The anti-reflection coating on the surface of the lens plated by the vacuum coating machine and vacuum coating equipment is a very thin inorganic metal oxide material (thickness less than 1 micron), hard And crisp. When it is plated on a glass lens, since the base is relatively hard and the grit is scratched on it, the film layer is relatively difficult to scratch; but when the anti-reflection film is plated on an organic lens, the laser lens of the base is soft and the grit Scratch on the film, the film is easily scratched. Therefore, the organic lens must be coated with an anti-wear film before the anti-reflection film is coated, and the hardness of the two film layers must match.
In addition to the application of filters in conventional microscopy, some special filters are used in fluorescence microscopy. Such as wide-spectrum transparent excitation filter, high-performance narrow-spectrum excitation filter, high-performance wide-spectrum excitation filter, interference filter, blocking filter, color and light separation filter, etc. The absorption curves and usage methods of these filters can be introduced in the special chapter on fluorescence microscopy. There are more special 1/2-wavelength wafers, 1/4-wavelength wafers and various interference plates will be described in the chapters on polarized light microscopes and interference microscopes.
These filters can be replaced with liquid filters under difficult conditions, or you can make your own. The specific details will be introduced in the appendix of this chapter.
1. The daylight filter will turn yellow when using artificial light sources. It is difficult to distinguish the details of red staining and yellow staining of stained specimens. The light blue No. 209 filter can change the artificial light source to approximate natural light. The light blue glass slide attached to the ordinary microscope belongs to this kind of filter.
2. Green filter When observing the red details on the specimen, using the green filter can increase the contrast of the specimen details, that is, the contrast. It is even more important when taking photomicrographs on black and white negatives. Because the general full-color film is particularly sensitive to blue and green light, but slow to red light. The negative of hematoxylin-eosin stained specimens is too bright without the green filter. When the green filter is used, the blue color of the details of the specimen is absorbed to show a natural image. Therefore, when performing microphotographs on black and white film, it is better to adopt the No. 211 transmission curve 510-reflector 590nm filter in the Livi filter series.
3. The yellow-green filter with high absorption rate of the yellow-green filter is very important for the observation of unstained specimens such as cultured cells with low contrast.
4. Yellow filter Livi series 510nm 212 filter is also very good for the observation of living cells. The contrast of the microscopic R image is too large, and the yellow filter can properly display the blue details of the specimen when the details of the object image are not clear.
5. Blue filter The 209th filter in the Livi series has a transparent 430-480nm, and is best used to observe yellow and green stained specimens and their display. Microphotograph.
6. Heat-absorbing filter In an earlier period, a liquid heat-absorbing filter was used to prevent infrared thermal radiation from damaging the optical system. Modern large-scale microscopes are equipped with heat-absorbing glass filters that can be placed in or out of the light path in the illumination light source assembly of modern large-scale microscopes.