SU37366A1 - Optical system for projecting images over long distances at low magnification - Google Patents

Description

When designing a conventional projection installation (designing transparencies, film projections and microprojections), there are two tasks: 1) to give an image on a screen of sufficiently large dimensions and 2) to obtain the greatest image brightness. The solution of these problems is reduced to a device of sufficiently high-aperture systems with a focal distance determined by the distance to the screen, and to the use of intense light sources. The latter circumstance is feasible only if there is a cooling system. Such types of projection are also present when there is no need for a strong magnification of the picture, and sometimes it is even desirable to design it with a slight decrease. However, by virtue of the habit of conventional projection technology, in these cases, conventional projection systems and associated lighting and cooling devices are used. In this case, if the image on the screen should be small, then they resort to making transparencies with correspondingly reduced images.

The need to have sufficient image brightness on the screen makes the light source even more powerful and, therefore, complicates the cooling system. If you resort

If a projection system is special for these purposes, then in most practically necessary cases it is possible to get along with ordinary light sources, and therefore cooling systems will not be required; The brightness of the image on the screen will be at small magnifications almost equal to the brightness of the transparency. However, for purposes of low magnification design, it is not possible to use ordinary lenses of large focal length, since they would require a very large size of projection devices. The proposed projection system, shown schematically in the drawing, has all the necessary properties for designing over long distances with small magnifications, is of the most ordinary size and can be supplied in conventional projection apparatuses that do not require any alterations or additions. This optical system is built on the principle of an inverted telephoto lens with the only difference that the front main plane (in the rear telephoto lens) // i by special calculation of the positive p and negative system components is carried beyond the rear rear plane // 2. which further shortens both the frame of the system and its working (free) distance d to the main focus point F of the entire system; the equivalent focal distance of the system / is determined by the well-known formula:

f p

7 d

where / p is the focal distance of the positive component, / c is the focal distance of the negative component, and D is the distance between the points of their main foci FP and FJ ,.

When using the system, it is put as a negative component n to the transparency and is focused by moving the positive component (by changing the value of E). This makes it possible, at usual distances x between the front lens of the system and the slide plane, to project for tens of meters at a magnification of 1: 1, and the length of the system itself is almost equal to the length of an ordinary projection lens.

In order to verify the correctness of the principle of this system, it is enough to take an ordinary telephoto lens or theatrical binoculars, place it at a distance

12–15 cm from the incandescent lamp, turning the negative lens (eye in binoculars) to the lamp and directing the light beam emanating from the positive lens to the white wall 4–5 m from the lamp. By changing the distance between the lenses of the system, it is possible to obtain a completely sharp image of the lamp on the wall, which is almost equal in magnitude to the size of the lamp.

The subject matter of the invention.

An optical system for projecting images over a large distance with a small magnification, consisting of positive and negative components, characterized in that the components n vi p are designed so that both the main planes // i and H are removed from the system far back and front the main plane // i of the system is separated from the main focus / farther than the rear main plane // a, and the distance d between the front lens of the negative component and the main focus F is several centimeters with an equivalent focal length and the whole system in a few meters.

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