"Periscope" project in physics (grade 8) on the topic. See what "Periscope (optical device)" is in other dictionaries

City Mosin scientific readings for schoolchildren

"Step into Science"

MBOU - lyceum №4

Section No. 3 "World of technology and technology"

Project work in physics on the topic:

"Periscope device"

8th grade student A

Malofeeva Ilya

Supervisor: Andrey Matvievsky, teacher of physics

Tula 2012

Introduction………………………………………………………………….2

Goals and objectives of the work………………………………………………………3

1. Ray propagation laws……………………………….….3
2. Flat mirror…………………………………………………...4
3. Periscope device……………………………………………….4
4. The first periscopes………………………………………………...4
5. Do-it-yourself periscope……………………………………………5
6. Areas of application of periscopes………………………………...6

Conclusions…………………………………………………………….10

List of literature and Internet resources………………………..11

Introduction

I chose the topic “Periscope” because I have always been interested in how the trick is performed with a tube, which makes it possible to see “through opaque objects” (Fig. 1).

Rice. one

An imaginary "X-ray machine" distinguishes the surroundings not only through thick paper, but also through a knife blade, which is impenetrable even for real X-rays. It turned out that the secret of the trick is simple. Four mirrors tilted at an angle of 45° reflect the rays several times, leading them around an opaque object.

The chosen topic seems relevant to me, because it reminds me that physics is a “living” science, very closely related to life. Based on this, they formulated

Goals and objectives of the work

The purpose of this work: To assemble a working model of the periscope and evaluate the possibility of its practical application.

To do this, it is necessary to solve the following tasks:

1. To study the principle of operation and the device of the periscope.
2. To study the physical laws underlying the operation of the periscope.

3. Get acquainted with the possibilities of using periscope systems in various fields of technology.

1. Laws of Ray Propagation

It turned out that the laws of propagation of a light beam in transparent media are described by physics in the section "Geometric optics". These laws are applied to the creation and calculation of all kinds of optical instruments: glasses, microscopes, cameras, periscopes, and so on.

All of these devices use light reflection, a physical phenomenon in which light incident from one medium (eg air) at the interface with another medium (eg mirror surface) returns back to the first medium.

When we hear the word "reflection", the first thing we think of is a mirror. In everyday life, we most often use flat mirrors. With the help of a flat mirror, a simple experiment can be carried out to establish the law by which light is reflected.

Surely everyone paid attention to the fact that our reflection in the mirror raises our left hand when we raise our right hand in front of the mirror. The clock, showing fifteen minutes past twelve, is mirrored as showing fifteen minutes to twelve, and the text on the page in the reflection looks like some kind of gibberish.

The reason is that when light falls on a mirror surface, light is reflected, and the incident beam, the reflected beam and the normal to the reflecting surface lie in the same plane. The angle of incidence is equal to the angle of reflection: q 1 = q" 1 . The law of reflection is valid for both flat and curved surfaces (Fig. 2).

When light rays emanating from some object are reflected from a flat mirror surface, aimaginary imageobject (Fig. 3). The object and its imaginary image are located symmetrically relative to the mirror surface. The image of an object in a flat mirror is equal in size to the object itself.

2. Flat mirror

This property of flat mirrors is used in such a device as a periscope.

3. Periscope device

Periscope (from the Greek. Periskopeo - I look around, I look around), an optical device for observing from shelters. Many periscopes allow you to measure horizontal and vertical angles on the ground and determine the distance to the observed objects. The device and optical characteristics of the periscope are determined by its purpose, installation location and the depth of the shelter from which observation is carried out. The simplest periscope is an elongated optical system for observation, enclosed in a long tube, at the ends of which at an angle of 45 about mirrors are located to the axis of the pipe, twice refracting the light beam at a right angle and shifting it. The amount of offset (periscopic offset) is determined by the distance between the mirrors. The diagram of the simplest periscope is shown in fig. 7.

Rice. 7

The most common are prismatic periscopes (Fig. 8), in the tube of which rectangular prisms are installed instead of mirrors, as well as a telescopic lens system and an inverting system, with which you can get an enlarged direct image. The field of view of periscopes at low magnification (up to 1.5 times) is about 40 about ; it usually decreases as magnification increases. Some types of periscopes allow all-round visibility.

Rice. eight

4. The first periscopes

In the 19th century in Paris, on the embankment near the Louvre, passers-by were shown magic mirrors, with the help of which they could freely look through thick stone walls (Fig. 9). This experience exactly repeats the trick I described at the very beginning.

Rice. nine

This device likewise consisted of a spotting scope split in the middle (where a thick stone was placed) and containing four flat mirrors at an angle of 45°. So for the first time a new optical device was advertised - a periscope (Fig. 10).

Fig.10

5. Do-it-yourself periscope

I decided to build a simple periscope with my own hands. I started with a pipe. At first I tried to use a cardboard, rectangular section. I made cutouts at the bottom of one half and at the top of the other. Eyepieces made of thick drawing paper are glued to the ends of the tube. Two rectangular mirrors were bought in a haberdashery.
I glued the mirrors to the drawing paper supports. After that, the stands, together with the mirrors, were put into the pipe through the eyepieces and glued.

However, the cardboard periscope did not survive to protect the project, so a more reliable structure had to be built, made of a plastic box for wiring. A plastic or tin box for ventilation may also be suitable. The design will be more reliable, durable and spectacular. Therefore, all steps were repeated anew.

The periscope is ready. You can stand behind some opaque partition, put the periscope beyond its edge, and, looking through the eyepiece, see the "invisible".

6. Fields of application of the device

The periscope has found wide application in military equipment. Through the periscope, you can follow the enemy without leaning out of the trench. The image caught by the upper mirror is transmitted to the lower one, into which the observer looks (Fig. 11).

Rice. eleven

Periscopes allow you to conduct circular observation of the area with the minimum size of viewing holes.

Rice. 12

Depending on the purpose, the offset (height) of the periscope can be different, reaching, for example, in a special mast periscope for observation in the forest, up to tens of meters. A periscope is also used on submarines for visual observation of the enemy. The periscope extends telescopically above the surface of the water, while the submarine itself is under water at this time (Fig. 12).

Domestic submarines were equipped with attack periscopes (PA), or commander's, as well as anti-aircraft (PZ). Commander's periscopes served to determine the distance to the target, bearing and its heading angle to it, heading angle of the target and its speed.
Periscopes are also installed on modern tank technology. In military periscopes, not mirrors are often used, but prisms, which are also capable of changing the course of light rays, and in addition, the image received by the observer is enlarged using a lens system.

Rice. 13. And this is how the police use periscopes

The periscopic system of mirrors shown in fig. 14, is used for visual inspection of vehicles, cargo, hard-to-reach and poorly lit places in the premises. The device is indispensable in the work of law enforcement agencies, security services, and can also be used in everyday life.

Rice. fourteen

Currently, a periscope mirror system is also used for right-hand drive cars, which simplifies overtaking on the left (Fig. 15). In the information mirror of the system, the driver sees the situation in the neighboring left lane, and in front, in the oncoming section.

Rice. fifteen

The development of fiber optics has led to the creation of other typesperiscopes that allow doctors to examine the humanbody from the inside without the need for surgery.Such types of periscopes are called endoscopes and are simply indispensable in medicine for diagnostics or endoscopic operations.
The periscope is one of the simplest, but at the same time the most interesting optical instruments. Used to shift the observer's line of sight. It is convenient for "seeing" through the heads of the crowd at races and competitions, at sports games.

findings

From this work, I have drawn the following conclusions.

1. As a result of the work, the device and the principle of operation of the periscope were studied.
2. The law of reflection of light from a reflective surface has been studied
3. A working model of the periscope was made.
4. The manufactured device can find practical application:

At sports competitions, stadiums in a large crowd for "vision" over their heads;

Made of large-section pipes, the periscope can be used to additionally illuminate dark household utility rooms (basements, sheds, storerooms, etc.) with sunlight, which does not require additional energy costs.

5. The possibility of using periscope systems in various areas of human life and activity is considered.

And for myself, I made a few more "informal" conclusions. In my opinion, physics is an amazingly interesting science that allows you to simply and clearly explain phenomena that seem incredible at first glance. Knowledge of the laws of physics can help in everyday life and even organize interesting leisure activities. I think that now studying physics will become much more interesting for me.

List of literature and Internet resources

1. dic. academic.ru/Scientific and technical encyclopedic dictionary
2. scilip-military.narod.2/ Solodilov K. E. Military optical-mechanical devices
3. zarnici.ru/arsenal-razvedchica/Zarnitsa
4. class-fizika.narod.ru/class!physics for the curious
5. rifmovnic.ru/Models and devices
6. potomu.ru/Periscope
7. www.submarine.narod.ru/Museum submarine fleet

Quite recently, Twitter Inc launched a new mobile streaming service called Periscope. Broadcasts became available immediately for Android and iOS users in March 2015. This software appeared a year earlier thanks to Keivon Beykopur and Joe Bernstein. After its creation, it was bought by Twitter for a huge amount of money - $ 120 million.

In July 2015, the company was able to take stock: it counted more than 10 million registered users, and this is just 4 months of existence. The functionality of the software is quite wide, but the main task of the program is video broadcasting and communication.

Appearance

For many who became the first users of Periscope, it was not clear what the word was. Previously, it could be heard, for example, in the movie "Raise the Periscope". This American comedy appeared in the distant 60s. At that time, no one knew exactly about smartphones and programs for them. In 1996, another comedy with a similar title came out. Down Periscope is a very popular wartime movie.

But, one way or another, none of these films is in any way connected with the program. So why does it have such a strange name?

"Periscope"

This is an optical device that is installed on submarines, tanks. Thanks to him, you can observe from the shelter. It looks like an ordinary pipe, on both sides of which mirrors are fixed. They are arranged so that the course of light rays changes. The periscope can also be hand held or a stereo tube. One way or another, it is used in military affairs. Now it becomes clear about the two aforementioned war films. There it was just about the captains of submarines.

For software, such a name is strange, although it can be explained. The developers wanted to show the user that he can watch the whole world through this program. He has access to broadcasts of absolutely all participants. Although the software allows users to hide their streams.

However, anyone who has downloaded Periscope can easily travel to Paris or New York, watch broadcasts from Australia or Britain. In this case, the smartphone screen will become a kind of periscope tube.

Communication

We already know what a social network is. "Periscope" in this case remains between this concept and the term "application". The software still has social network functions. You can not only connect to the broadcasts, but collect your circle and conduct broadcasts for them. Thus, you meet new people, find friends with the same interests, learn the language and just travel without leaving the room.

Many are still interested in what Periscope is: a social network or regular software? But everyone is already used to answering this question in their own way. Those who use Periscope for communication can safely call it a social network, those who only "spy" on the lives of others can consider it just an entertainment application.

Danger

To the question of what "Periscope" is, many can answer - life. Indeed, some users spend the whole day there. They can share the events of their lives with other people, broadcast their breakfast, lunch and dinner, going to school or work, holidays and entertainment.

Many users are sure that Periscope draws them worse than other social networks. This is due to the numerous broadcasts. For example, if a photo on Instagram can be seen tomorrow, then you won’t watch the broadcast later. It will start at a certain moment and force you to abandon all your affairs and bury yourself in the screen of your smartphone.

Sympathies

Many users believe that it is through Periscope that you can look real. Videos are recorded instantly and immediately published. Nothing can be duplicated, let alone cut.

To gather an army of fans around you, you need to broadcast regularly. Then, in addition to subscribers, you can score a lot of "hearts". To find interesting broadcasts, the program will recommend random users to you.

But you will never understand what Periscope is unless you try this app for yourself. How to work with it, we will consider further.

To start download

It is clear that before you start using the software, you need to install it on the gadget. To do this, go to the application store. For devices with the iOS operating system, go to the App Store, for Android OS, go to the Play Market, and for Windows Phone, go to the Windows Phone Store. Enter Periscope into the search box and click install.

Registration

Now that the icon of the new application has appeared on the desktop, select it and go to the software. Before starting work, the program will tell us what Periscope is. Before us will appear a slide show demonstrating our capabilities.

You need to select "get started", and we will be redirected to "registration or login". Since you are a new user, you will need to create an account. This can be done in two ways:

• With the help of Twitter.
• With a phone number.

If you are a Twitter user, signing up is easy. To do this, click "login with Twitter". The program will automatically redirect you to its first tab. If you do not have your Twitter account details entered on your smartphone, you will have to spend time filling out your account.

If you do not have the above program, you can register using your phone number. You need to select a country, enter a number. Next, an SMS will be sent to the phone, in which there is a confirmation code.

This is not the end of registration. Before us is your future profile. Now you just need to fill it out. Enter the first and last name, also come up with a username (nickname), add your photo.

Find and don't give up

Now that we are registered, we want to test the program. To do this, we need to find interesting users. The first tab will contain those to whom you are subscribed, and below the recommended broadcasts. The first three of them are new people, and below are the ones you've already watched.

Be always up to date

If suddenly you did not have time for the broadcast, it will be available for another 24 hours. The same goes for the people you recommend. It will not always display those who are currently online. Sometimes the software recommends viewing already completed streams. The entry is interactive. You will see how users were added to it and how they put "hearts". In offline mode, you can rewind the video.

Online

To watch live broadcasts, you need to go to the tab with the globe. Before you will be presented a map of the world with a huge number of points. These are all broadcasts that are happening at the moment around the world. You can choose, for example, your city and see the people who are currently streaming, perhaps your friend or neighbor will be among them.

The program appeared in the early spring of 2015, was introduced to us by Twitter, and that is why you can register on Periscope through your Twitter account. True, there is another affordable way to register - using a mobile phone number. Below we will describe in detail the registration process and the main functions of the application, but for now we recall that Periscope is a streaming service for online broadcasts from the camera of your phone or tablet. Periscope has already united hundreds of thousands of users from all over the world, thanks to the ability to share interesting videos in real time.

How to register on Periscope

To start working with Periscope, it is not at all necessary to have a Twitter account, although having a page will significantly speed up the promotion of your periscope profile and help you quickly gain followers. In any case, all you need to register is your mobile phone number.

PERISCOPE, an optical device that makes it possible to view objects located in horizontal planes that do not coincide with the horizontal plane of the observer's eye. It is used on submarines for observing the surface of the sea when the boat is submerged, in the land army for safe and invisible observation of the enemy from protected points, in technology for studying inaccessible internal parts of products. In its simplest form, the periscope consists of a vertical tube (Fig. 1) with two mirrors S 1 and S 2 inclined at an angle of 45 ° or prisms with total internal reflection, located parallel to each other at different ends of the tube and facing each other with their reflective surfaces . However, the reflective system of the periscope can be designed differently. The system of two parallel mirrors (Fig. 2a) gives a direct image, the right and left sides of which are identical with the corresponding sides of the observed object.

A system of two perpendicular mirrors (Fig. 2b) gives an inverse image, and since it is viewed by an observer with his back to the object, the right and left sides change their places. Reversing the image and shifting the sides is easy to achieve by placing a refractive prism in the system, but the need to observe with the back to the object, and hence the difficulty in orientation, remains, and therefore the second system is less suitable. The disadvantages of the periscope shown in Fig. 1 and used in positional warfare, are an insignificant angle of view α (about 10-12 °) and a small aperture, which forces us to limit ourselves to a length of no more than 1000 mm with a relatively large diameter of the pipe - up to 330 mm. Therefore, in a periscope, the reflective system is usually associated with a lens system. This is achieved by attaching one or two telescopes to the periscope reflection system. Moreover, since an ordinary astronomical tube gives an inverse image with displaced sides, a combination of perpendicular mirrors with such a tube will give a direct image with correctly located sides. The disadvantage of such a system is the position of the observer with his back to the subject, as mentioned above.

Attaching an astronomical tube to a system of parallel mirrors is also impractical, since the image will turn upside down, with the sides turned. Therefore, a system of parallel mirrors and a terrestrial spotting scope, which gives a direct image, are usually connected in a periscope. However, the installation of two astronomical tubes after two inversions will also give a direct image, which is why it is also used in the periscope. Pipes in this case are arranged with lenses to each other. The refractive system of the periscope does not present any features in comparison with the telescope, however, the choice of one or another combination of telescopes (more precisely, lenses), their number and focal length is determined by the required angle of view and aperture ratio of the periscope. In the best periscopes, image brightness decreases by ≈30% depending on the system and lens grade.

Since the clarity of the image also depends on the color of objects, an improvement in visibility is also achieved by using color filters. In the simplest form of a periscope (Fig. 3), the upper lens O 1 gives a real image of the object at point B 1, refracting the rays reflected by the prism P 1 . The converging lens U creates at point B 2 also a real image of the object, which is reflected by the prism P 2 and viewed through the eyepiece O 2 by the eye of the observer. Achromatic lenses are commonly used in tubes, and steps are taken to eliminate other aberrational distortions. By installing two telescopes one after the other, acting as described above, it is possible to increase the distance between the prisms without compromising the aperture ratio of the periscope and its field of view. The simplest periscope of this type is shown in Fig. 4. Already the first periscopes of this type gave a field of view of 45 ° and an increase of 1.6 with an optical length of 5 m with a tube diameter of 150 mm.

Because observation with one eye is tiring, then periscopes were proposed that give an image on frosted glass, however, this image significantly lost clarity, and therefore the use of frosted glass in periscopes was not widespread.

The next step in the development of the idea of ​​periscopes were attempts to eliminate the need to rotate the periscope tube when viewing the horizon at 360 °. This was achieved by connecting several (up to 8) periscopes on one pipe; a corresponding part of the horizon was examined through each of the eyepieces, and the observer had to bypass the pipe. Nevertheless, multiplier periscopes of this kind did not give the whole picture as a whole, and therefore omniscopes were proposed, giving the entire horizon in the form of an annular picture due to the replacement of the lens with a spherical refractive surface. This kind of devices, differing in considerable complexity, did not provide an increase in the vertical field of view, which prevented the observation of aircraft, and distorted the image, and therefore fell into disuse. More successful was the strengthening of the optical system in the inner tube, which could rotate inside the outer tube, regardless of the latter (Fig. 5).

Panoramic periscopes of this kind, or kleptoscopes, require some additional optical device. The light beam, penetrating into the head of the periscope through a spherical glass cover H, which protects the device from water ingress and does not play an optical role, propagates through the optical system P 1, B 1, B 2, etc., which is fixed in the inner tube J. The latter rotates with the help of a cylindrical gear, shown at the bottom of the device by the handle G, regardless of the outer casing M. In this case, the image falling on the lens B 3, refracted by the prism P 2 and viewed by the eyepiece, will rotate around the light axis of the eyepiece. To avoid this, a quadrangular prism D is fixed inside the inner tube, rotating about the vertical axis with the help of a planetary gear K 1, K 2, K 3 at half speed and straightening the image.

The optical nature of the device is clear from FIG. 6 showing how the rotation of the prism rotates the image at twice the speed. An increase in the field of view in the vertical direction from 30 ° in a conventional periscope to 90 ° is achieved in an anti-aircraft periscope by installing a prism in the objective part of the device that rotates about the horizontal axis, regardless of the rotation of the entire upper part about the vertical axis to view the horizon. The optical part of a periscope of this type is shown in Fig. 7.

Periscopes are used on submarines for two purposes: observation and control of torpedo fire. Observation may consist of simple orientation in the environment and a more careful examination of individual objects. For observation, objects b. visible in full size. At the same time, it has been practically established that for accurate reproduction with monocular observation of objects that are usually observed binocularly with the naked eye, the increase in the device should be. more than 1.

Currently, all submarine periscopes have a magnification of 1.35-1.50 for simple orientation. For a careful examination of individual objects, the increase should be. more, with the maximum possible illumination. Currently, an increase in X 6 is used. periscopes are subject to a double requirement regarding the increase of the device. This requirement is satisfied in bifocal periscopes, the optical part of the objective of which is given in Fig. eight.

The change in magnification is achieved by rotating the system by 180°, while the O 1 lens and the K 1 lens do not move. For a larger magnification, the V’ 1, P "2, V’ 2 system is used, for a smaller one, the V 1, P 1, V 2 system. The appearance of the lower part of the zenith bifocal periscope is given in Fig. 9.

The described construction for changing the magnification is not the only one. More simply, the same goal is achieved by removing unnecessary lenses from the optical axis of the device, mounted in a frame that can be rotated around the axis at will. The latter is designed vertically or horizontally. For direction finding of objects, determining their distance, course, speed, and for controlling torpedo fire, periscopes are equipped with special devices. In FIG. 10 and 11 show the lower part of the periscope and the observed field of view for a periscope equipped with a vertical baseline rangefinder.

In FIG. 12 shows the field of view of the periscope for determining the distance and heading angle according to the principle of alignment.

In FIG. 13 shows the lower part of a periscope equipped with a photographic camera, and FIG. 14 - the lower part of the periscope with a device for controlling torpedo firing.

The head of the periscope, when moving, causes waves on the surface of the sea, which make it possible to establish the presence of a submarine. To reduce visibility, the head of the periscope is made as small as possible in diameter, which reduces the aperture ratio of the periscope and requires overcoming significant optical difficulties. Usually, only the upper part of the pipe is narrow, gradually expanding it downwards. The best modern periscopes with a pipe length of more than 10 m and a diameter of 180 mm have an upper part about 1 m long with a diameter of only 45 mm. However, it has now been established by experience that the discovery of a submarine is achieved not by the detection of the periscope head itself, but by the visibility of its trace on the surface of the sea, which persists for a long time. Therefore, at present, the periscope is protruded above the sea surface periodically for a few seconds, which are necessary for the observation, and immediately hidden until it reappears after a certain period of time. The wave formation caused in this case is much closer to the usual wave of sea water.

The difference in temperature in the pipe and in the environment, combined with the humidity of the air inside the periscope, leads to fogging of the optical system, to eliminate which devices are arranged to dry the periscope. An air tube is installed inside the periscope, drawn into the upper part of the pipe and coming out at the bottom of the periscope. On the other side of the latter, a hole is made from which air is sucked out of the periscope and enters a filter charged with calcium chloride (Fig. 15), after which it is forced into the upper part of the periscope by an air pump through the inner pipe.

Periscope tubes must meet special requirements for strength and rigidity, in order to avoid damage to the optical system; in addition, their material should not affect the magnetic needle, which would disrupt the operation of ship compasses. In addition, pipes should be especially resistant to corrosion in sea water, because in addition to the destruction of the pipes themselves, the tightness of the connection in the stuffing box through which the periscope extends from the boat hull will be violated. Finally, the geometric shape of the pipes must be particularly precise, which, given their long length, creates significant difficulties in production. The usual material for pipes is low-magnetic stainless nickel steel (Germany) or special bronze - immadium (England), which has sufficient elasticity and rigidity.

Strengthening the periscope in the hull of a submarine (Fig. 16) causes difficulties, depending both on the need to prevent the ingress of sea water between the periscope tube and the hull of the boat, and on the vibration of the latter, disturbing the clarity of the image. The elimination of these difficulties lies in the design of the stuffing box, sufficiently waterproof and at the same time elastic, securely connected to the hull of the boat. The pipes themselves must have devices for quickly raising and lowering them inside the boat hull, which, with a periscope weighing hundreds of kg, leads to mechanical difficulties and the need to install motors 1 that rotate winches 2, 4 (3 - switching on for the middle position, 5 - manual drive , 6, 7 - handles for the clutch mechanism). When the tube is raised or lowered, observation becomes impossible because the eyepiece moves rapidly vertically. At the same time, the need for observation is especially great when the boat emerges. To eliminate this, a special platform is used for the observer, connected to the periscope and moving with it. However, this causes an overload of the periscope tubes and the need to allocate a special shaft in the ship's hull to move the observer. Therefore, a stationary periscope system is more often used, which allows the observer to maintain his position and not interrupt his work while the periscope is moving.

This system (Fig. 17) dismembers the ocular and objective parts of the periscope; the first remains motionless, and the second moves with the pipe vertically. For their optical connection, a tetrahedral prism is installed at the bottom of the pipe, and so on. the light beam in the periscope of this design is reflected four times, changing its direction. Since the movement of the tube changes the distance between the lower prism and the eyepiece, the latter intercepts the light beam at its various points (depending on the position of the tube), which violates the optical unity of the system and leads to the need to include another movable lens that regulates the beam rays according to the position of the pipe.

Typically, at least two periscopes are installed on submarines. Initially, this was caused by the desire to have a spare device. At present, when two periscopes of various designs are required - for observation and attack, the periscope used in the attack is at the same time a spare in case one of them is damaged, which is important for performing the main task - observation. Sometimes, in addition to the indicated periscopes, a third, spare, is used exclusively in case of damage to both main ones.

Army periscopes are more simple in design compared to naval ones, while maintaining the main features and improvements of the device. Depending on the purpose, their design is different. An ordinary trench periscope consists of a wooden pipe with two mirrors (Fig. 1). More difficult is the device of the periscope tube, which includes an optical refractive system, but does not differ in special dimensions; such a tube is usually arranged on the principle of a panoramic periscope (Fig. 18).

The dugout periscope (Fig. 19) is similar in design to the simplest marine type and is intended for making observations from shelters.

The mast periscope is used to observe distant objects or in the forest, replacing uncomfortable and bulky towers. It reaches a height of 9-26 m and consists of a mast that serves to strengthen the optical system, mounted inside two short pipes of large diameter. The eyepiece tube is mounted on a carriage at the bottom of the mast, and the objective tube is mounted on the retractable top of the mast. Thus, in this type there are no intermediate lenses, which, despite a significant increase (up to x 10), at a low position of the mast, causes a decrease in the latter as the mast extends, with a simultaneous decrease in image clarity. The mast is mounted on a special carriage, which also serves to transport the device, and the mast moves. The carriage is quite stable and only in strong winds requires additional fastening with bends. The periscope is successfully used in engineering for examining holes drilled in long forgings (shafts, tool channels, etc.), to check for the absence of shells, cracks, and other defects. The device consists of a mirror located at an angle of 45° to the channel axis, mounted on a special frame and connected to an illuminator. The frame moves inside the channel on a special rod and can rotate around the axis of the channel. The telescopic part is mounted separately and placed outside the forging under study; it serves not to transmit an image, as in an ordinary periscope, but to better examine the field of view captured by the periscope.