What is the development history of zoom lenses?
The development of zoom lenses has a long history. In fact, when it was first born, photography technology had not really entered the practical stage. It was in 1834 that the British mathematician Peter Barlow proposed adding a negative lens to the eyepiece group of a telescopic telescope, "to make the lengthened lens adjustable, so that its magnification can be changed at any ratio, even without using it." The idea that the lens moves away from the eye or causes the line of sight to move away from the object being observed. This was the original idea behind designing a zoom lens.
However, Barlow's idea was not put into practice until more than fifty years later. In 1890 and 1891, essentially very similar telephoto lenses with variable focal lengths were invented by an Englishman, a Frenchman and two Germans respectively.
This kind of lens has been welcomed by photographers as soon as it appeared, but it is still very imperfect technically. First of all, during use, the camera must refocus every time the lens magnification (focal length) is changed; moreover, as the focal length increases, the effective aperture value of the lens will gradually become smaller, making it difficult to control the exposure. Extremely complex. The most serious problem is that the photos taken with this lens have poor sharpness and cannot be compared with ordinary lenses.
In 1902, American optician Charles Allen initially solved the above problem and obtained the patent for the first real zoom lens. Allen's patent was to add a movable lens between two fixed lenses. During use, when the movable lens moves away from the front lens, the focal length will be shortened; on the contrary, when it moves in the other direction, the focal length will increase. In the shortest and longest positions, the image can be "compensated", i.e. the focus remains the same. In the middle position, the focus shifts, but as long as a smaller aperture is used, this shift is still acceptable.
The world's first relatively modern zoom lens (25-80mm, F2.8) was designed by German optician Helmut in 1932 for Siemens' 16mm movable movie camera. This zoom lens is quite complex. It is composed of 8 lenses divided into 6 groups. There is a fixed section behind it, and two groups of independently movable lenses complete the zoom and focus functions respectively. One group, called a "zoom lens," can move linearly from front to back to change the focal length. Another set of movable lenses, called the "compensation lens," is located at the front of the lens. Its movement trajectory is eccentric, first forward and then offset, to ensure that the image has the correct focus at any focal length position. This form of focus correction method is called "mechanical compensation method" because it uses a cam to maintain the required nonlinear motion.
This method continued to be used until the 1950s when it was replaced by the "optical compensation method". The new system uses more than two sets of inner lenses to move synchronously to change the focal length and complete focus compensation. The optical structure of modern zoom lenses is relatively complex. A typical zoom lens is generally composed of 15 lenses divided into several groups. The possibility of assembly errors for a lens with such a complex structure is much greater than that of a simple lens. There are a lot of contact surfaces between air and glass inside the zoom lens, so it is very easy to produce unexpected halos. However, this shortcoming has improved with the development of lens coating technology in the 1950s. With the adoption of coating technology, lens designers can boldly design optical systems containing a large number of air-glass interfaces.
Dr. Frank Buck of a company in New York, USA, designed the world's first zoom lens for cameras in 1958. This 36-82, F2.8 lens was a 35mm from Germany. The single-lens reflex camera was the latest optically compensated zoom lens at the time, but it was quite large and bulky.
In 1963, Japan's Nikon launched the mechanically compensated zoom lens Nikkor 43-86mm.F2.8, paving the way for a truly popular zoom lens design. At the time, Nikon explained this: "This zoom lens is designed for use in sports photography and other fields that require high speed and ease of use. But if the clarity of the image is your first priority, it is best to choose a fixed focus lens.
”
The reason why the zoom lens design has returned from the optical compensation method to the mechanical compensation method is because it can make the zoom lens design lighter, have better focus compensation effect, and facilitate the lens designer to make more adjustments. Clever optical correction. Other related technologies adopted at that time, such as anti-reflective multi-layer coating and extremely low dispersion special optical glass, also made a great contribution to improving the image quality and miniaturization of zoom lenses in the future.
In recent years, the development and production of zoom lenses have made rapid progress. Not only have their technical performance been improved, but they are also more convenient to use. The newly released zoom lenses have the following characteristics: medium and long zoom lenses have larger diameters and are more convenient to use. The size is getting smaller and smaller; commonly used zoom lenses are becoming higher-magnification; the focal length is developing to both long and short ends, and the macro structure has also been greatly improved.