The English name of a doublet lens is doublet. It is a light group composed of two lenses cemented together, which is mainly convergent, called a double (cemented) lens. The purpose is to correct spherical aberration, coma, and chromatic aberration. Most telescopes are of this type. The doublet lens can be crowned glass early Amo, called doublet lens, the curvature is relatively flat, easy to manufacture, can also be flint glass in front, aberration correction is better, but the chemical stability is poor, less used. As for the Gauss doublet lens, it is not cemented, but it can better correct spherical aberration. A doublet lens is also used in a simple camera. In order to correct astigmatism, the object surface is concave, and the diaphragm position is used to correct coma. The concave mirror is made of flint glass.
Monochromatic filters, generally interference filters are used. , Gu can do cut-off filters, cold (reflective) mirrors, subtractive color filters, frustrated total reflection interference filters and lens design induced transmission interference filters. There is also a monochromatic filter composed of two pieces of glass, but the band is wider.
Monochromatic light: The ideal monochromatic light should be a single-frequency light, a sine wave with no beginning and no end, but in fact only a very narrow band of multi-frequency light can be obtained , Is a mixture of sine waves, called composite light, hybrid light, and polychromatic radiation. Of course, it is more clear that it is quasi-monochromatic light, which is usually called monochromatic light or multi-frequency light. This is the case with the usual spectral lines. If it is generalized to invisible radiation, it is logical that there will be monochromatic radiation.
John Porter's dark night classification is also a light pollution (light pollution) rating table. The higher the number, the heavier light pollution
1 Black, completely dark observation point in the sky, you can see the ecliptic light, the sun and the zodiac; the naked eye can directly and clearly see the Triangulum galaxy; the Milky Way between the Scorpio laser lens and Sagittarius is bright enough to be on the ground Cast shadows of things; easy to see atmospheric light.
2 gray, a typical truly dark observation point, along the horizon, the atmospheric light is faintly visible; it is easy to see the Triangulum galaxy with the naked eye; in summer, the Milky Way can be seen Most structure; the emerging clouds look like black holes in the starry sky.
3 blue, starry sky in the countryside, there will be some signs of light pollution at the horizon; the clouds near the horizon are slightly illuminated, and the clouds above the head are dark; The Milky Way still has rich details; the star clusters can still be clearly seen with the naked eye; the Triangulum galaxy can also be easily seen with the corner of the eye.
4 green-yellow, a transitional zone between rural and suburban areas. Arched light pollution can be seen in multiple directions above the horizon; the ecliptic light is still visible; above the horizon Galaxy’s high-power laser mirror group can still leave a deep impression on people.
5 orange, the starry sky in the suburbs, you can only see a little zodiacal light on the night of the spring and autumn season; the Milky Way at the horizon is very dim or even invisible, and the clouds are larger than the background sky brighter.
6 red, bright suburban starry sky, you can't see the zodiacal light; the Milky Way can only be seen in the direction of the zenith, and the naked eye can only see the Andromeda galaxy clearly.
7 red, the entire sky appears pale gray in the suburban/urban transition zone or full moon; strong light sources of light pollution are clearly visible in all directions; the Milky Way is no longer visible The naked eye can barely see the Pleiades or the Andromeda galaxy, but it is very blurry; the clouds are very bright.
Injury and other biological populations
A study by Austrian scientists shows that an advertising light box can lead to 350,000 Insects that reflect the light characteristics of the mirror die. Nocturnal animals such as owls, bats, possums, and badgers will become panicked under the light environment, and it will be more difficult whether it is foraging and breeding or hiding and avoiding danger. In summer and autumn, the fireflies that were common in the past have now disappeared in many cities. The light throughout the night decorated all corners of the city, but made the fireflies completely lose their breeding conditions. Light pollution during the day-glass curtain wall
The glass curtain wall originally brought modern colors and fashion aura. However, the noise generated by the reflection of the glass curtain wall can cause dizziness and temporary blindness, thus causing accidents.
In addition, the glass curtain wall is still a big energy consumer. Researchers have found through experiments that in summer, buildings with glass curtain walls need to use one horse of air conditioner for every 5 square meters of lighting area, and the energy consumption is 4 times that of ordinary buildings!
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