PERISCOPE, an optical device that makes it possible to examine 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 ground army - for safe and inconspicuous observation of the enemy from protected points, in technology - for examining inaccessible internal parts of products. In its simplest form, a periscope consists of a vertical pipe (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 pipe and facing each other with their reflective surfaces . However, the periscope reflective system can be designed in different ways. A system of two parallel mirrors (Fig. 2a) gives a direct image, the right and left sides of which are identical to the corresponding sides of the observed object.
A system of two perpendicular mirrors (Fig. 2b) gives a reverse image, and since it is viewed by an observer standing with his back to the object, the right and left sides change their places. Inverting the image and shifting the sides is easy to achieve by placing a refractive prism in the system, but the need to observe with your back to the object, and therefore difficulty in orientation, remains, and therefore the second system is less suitable. The disadvantages of the periscope shown in Fig. 1 and used in trench warfare, are a small angle of view α (about 10-12°) and a small aperture ratio, which forces us to limit ourselves to a length of no more than 1000 mm with a relatively large pipe diameter - 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 reflective system of the periscope. Moreover, since a conventional astronomical tube gives a reverse image with displaced sides, the combination of perpendicular mirrors with such a tube will give a direct image with correctly positioned 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 out upside down, with the sides facing away. Therefore, a periscope usually combines a system of parallel mirrors and an earthly telescope, which gives a direct image. However, installing two astronomical tubes after two inversions will also give a direct image, which is why it is also used in a periscope. In this case, the pipes are positioned with lenses facing each other. The refractive system of a periscope does not present any special features in comparison with a telescope, however, the choice of one or another combination of telescopes (or rather 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 is reduced by ≈30%, depending on the system and type of lens.
Since the clarity of the image also depends on the color of objects, improved 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 collecting lens U also creates at point B 2 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. Tubes typically use achromatic lenses and take steps to eliminate other aberration distortions. By installing two telescopes one after the other, operating similarly to the one described above, it is possible to increase the distance between the prisms without compromising the aperture 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 provided a field of view of 45° and a magnification of 1.6 with an optical length of 5 m and a pipe diameter of 150 mm.
Because observation with one eye is tiring, periscopes were proposed that provide an image on frosted glass, but this image significantly lost in clarity, and therefore the use of frosted glass in periscopes did not become widespread.
The next stage in the development of the idea of periscopes was attempts to eliminate the need to rotate the periscope tube when viewing the horizon 360°. This was achieved by connecting several (up to 8) periscopes on one pipe; the corresponding part of the horizon was examined through each of the eyepieces, and the observer had to walk around the pipe. This kind of multiplier periscopes did not give the whole picture as a whole, and therefore omniscopes were proposed that give the entire horizon in the form of a ring picture by replacing the lens with a spherical refractive surface. This kind of devices, being characterized by considerable complexity, did not provide an increase in the vertical field of view, which interfered with the observation of aircraft, and distorted the image, and therefore fell out of use. More successful was the strengthening of the optical system in the inner tube, which could rotate inside the outer one independently of the latter (Fig. 5).
This kind of panoramic periscope, or kleptoscope, requires some additional optical device. The light beam, penetrating the periscope head through the ball glass cover H, which protects the device from water and does not play an optical role, spreads through the optical system P 1, B 1, B 2, etc., which is fixed in the inner tube J. The latter rotates using a cylindrical gear train, shown at the bottom of the device by 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 a vertical axis using planetary gears K 1, K 2, K 3 at half speed and straightening the image.
The optical essence of the device is clear from Fig. 6, showing how rotating 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 zenith periscope by installing a prism in the objective part of the device, rotating about a horizontal axis, regardless of the rotation of the entire upper part about a 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 should be visible in life size. At the same time, it has been practically established that for accurate reproduction with monocular observation of objects usually observed binocularly with the naked eye, the magnification of the device must be increased. more than 1.
Currently, all submarine periscopes have a magnification of 1.35-1.50 for easy orientation. For a thorough examination of individual objects, magnification should be used. more, with the maximum possible illumination. Currently, an increase of X 6 is used. Thus. Periscopes have a double requirement regarding the magnification of the device. This requirement is satisfied in bifocal periscopes, the optical part of the lens of which is shown in Fig. 8.
Changing the magnification is achieved by rotating the system 180°, while the lens O 1 and lens K 1 do not move. For greater magnification, use the system V' 1, P" 2, V' 2; for smaller magnification, use the system V 1, P 1, V 2. The appearance of the lower part of the anti-aircraft bifocal periscope is shown in Fig. 9.
The described design for changing magnification is not the only one. More simply, the same goal is achieved by removing excess 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. To find direction of objects, determine their distance, course, speed and to control torpedo firing, periscopes are equipped with special devices. In fig. 10 and 11 show the bottom of the periscope and the observed field of view for a periscope equipped with a vertical base rangefinder.
In fig. Figure 12 shows the field of view of the periscope for determining the distance and heading angle using the alignment principle.
In fig. 13 shows the lower part of a periscope equipped with a photographic camera, and FIG. 14 - lower part of the periscope with a device for controlling torpedo firing.
When the periscope head moves, it 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 in diameter as possible, which reduces the periscope's aperture and requires overcoming significant optical difficulties. Usually, only the upper part of the pipe is made narrow, gradually widening it downwards. The best modern periscopes, with a tube 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, experience has now established that the discovery of a submarine is achieved not by detecting 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 surface of the sea periodically for a few seconds, necessary for making observations, and is now hidden until it reappears after a certain period of time. The wave formation caused in this case is significantly closer to the usual disturbance of sea water.
The difference in temperature in the pipe and in the environment, combined with air humidity inside the periscope, leads to fogging of the optical system, to eliminate which devices are installed for drying the periscope. An air tube is installed inside the periscope, led 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 pumped 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, the 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 seal through which the periscope extends from the boat’s hull will be disrupted. Finally, the geometric shape of the pipes must be particularly accurate, which, if they are long, 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 sea water from getting between the periscope tube and the hull of the boat, and on the vibration of the latter, which interferes with the clarity of the image. The elimination of these difficulties lies in the design of an oil seal that is 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 the periscope weighing hundreds of kg, leads to mechanical difficulties and the need to install motors 1, which rotate winches 2, 4 (3 - inclusion 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 quickly moves vertically. At the same time, the need for observation is especially great when the boat surfaces. To eliminate this, a special platform for the observer is used, connected to the periscope and moving with it. However, this causes overload of the periscope pipes 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, allowing the observer to maintain his position and not interrupt his work while moving the periscope.
This system (Fig. 17) separates the ocular and objective parts of the periscope; the first remains stationary, and the second moves vertically with the pipe. To connect them optically, a tetrahedral prism is installed at the bottom of the pipe, etc. 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 various points (depending on the position of the tube), which disrupts 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, submarines have at least two periscopes installed. Initially, this was caused by the desire to have a spare device. Currently, when two periscopes of different designs are required - for observation and attack, the periscope used during the attack is at the same time a spare one in case one of them is damaged, which is important for performing the main task - surveillance. Sometimes, in addition to the indicated periscopes, a third, spare one is installed, used exclusively when both main ones are damaged.
Army periscopes are distinguished by greater simplicity of design compared to naval ones, while at the same time maintaining the main features and improvements of the device. Depending on the purpose, their design is different. A conventional trench periscope consists of a wooden pipe with two mirrors (Fig. 1). The design of the periscope tube is more complex, including an optical refractive system, but not distinguished by any special dimensions; such a pipe is usually designed on the principle of a panoramic periscope (Fig. 18).
The dugout periscope (Fig. 19) is similar in design to the simplest type of naval periscope and is intended for making observations from shelters.
A mast periscope is used to observe distant objects or in the forest, replacing inconvenient 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 large-diameter pipes. 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 magnification (up to x 10), with a low mast position 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 technology to inspect holes drilled in long forgings (shafts, gun channels, etc.), to check the absence of cavities, cracks, and other defects. The device consists of a mirror located at an angle of 45° to the axis of the channel, mounted on a special frame and connected to the 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 is placed outside the forging under study; it serves not to transmit an image, as in an ordinary periscope, but to better view the field of view captured by the periscope.
Periscope is the most popular platform for broadcasting live broadcasts via a mobile device. Nowadays, people like to follow the lives of other users online. This is a good way to find out how your idols live and chat with them in real time.
You don't need deep technical knowledge to join the world of broadcasting. The creators of the application and web service ensured that the barrier to entry was low. 5 minutes will be enough for training, and the hardware requirements are limited only to the Internet and a good camera. Let's take a closer look at what Periscope is and how to use it on different devices.
History of the service creation
Most Periscope users don’t even know who created this application and when. In 2014, the idea of creating a service for streaming video streams to a large audience came to the mind of Kayvon Bikpour. Together with his friend Joe Bernstein, he drew up a detailed plan for future development. At the programming stage, it was Bernstein who was the main ideologist.
At the beginning of 2014, a beta version called Bounty was released. A large advertising campaign and investments bore fruit - in a matter of months the program gained $1.5 million. After this, users gradually began to decline or switch to competitive services - the presence of numerous bugs and the lack of updates affected them.
At the beginning of 2015, Twitter completely bought the rights to Bounty and called it Periscope. The company began promoting through Twitter, which brought success. In March of the same year, a test version was released on the App Store. A couple of months later the program reached the Android platform. That same year, the company announced it had reached 10 million users worldwide. Now you know what Periscope is.
How to use it?
To get started, download the free application via the AppStore or Play Market. You cannot broadcast from personal computers - you can only view broadcasts through the website. After installation you need to register. To do this, use one of two methods:
- existing Twitter account. The creators completely synchronized the two social networks with each other;
- Mobile phone number.
After registration, you can start working with the service. Let's figure it out
The application has 4 main tabs.
The first contains a list of people with your subscriptions (accounts whose broadcasts you follow). The list shows active channels. To go live, you just need to click on the channel nickname and wait for the video to load. Here is a list of guests for the last 24 hours of broadcasts.
The second tab shows all included broadcasts around the world. You can view them both in list mode (which is not very convenient) and on an interactive map. The user's location can be immediately determined on the map.
The third tab was created to enable personal broadcasts. Here you can set any settings and name of the future stream. More about this below.
And finally, the fourth tab is responsible for searching for users. Here you can find people, follow them, view channel statistics and any other information within this social network. Here you can open the settings menu, change personal information, and so on.
How does Periscope work?
When you visit another user's stream, you will see on the screen:
- background - user's camera image;
- field for entering messages at the bottom;
- text chat;
- flying hearts on the right will show the number of likes during the broadcast;
- the number of spectators is written in the lower corner;
- the upper right corner is a cross to exit the air.
You will be able to communicate with another user only in text format, and he will respond by voice on the stream if he reads your message. Each entry is stored for exactly 24 hours, unless the owner himself saves it. At this time, you can view it, like and comment.
Let's move on to hosting our broadcast. By opening the corresponding tab, you will see a window with settings: turn on the camera, turn on the microphone, turn on the location. The first two points must be included, the third is optional. Next, the broadcast window will open. Now write the name of your broadcast. The 4 icons on the screen perform the following functions (from right to left):
- enable/disable geolocation;
- hide broadcast (privacy);
- chat access settings;
- creating a Twitter alert.
To start streaming, click on the "Start broadcast now" button. After completion, your broadcast will also be saved in the channel archive. Now you know what Periscope is and how to broadcast on it!
Quite recently, Twitter Inc launched a new mobile streaming service - Periscope. Broadcasts became immediately available to Android and iOS users in March 2015. This software appeared a year earlier thanks to Kayvon Beykopour 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 sum up its results: it counted more than 10 million registered users, and this was in 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 this word was. Previously, it could be heard, for example, in the film “Raise the Periscope.” This American comedy appeared back in the 60s. Back then, no one knew exactly about smartphones and programs for them. In 1996, another comedy with a similar name was released. "Remove the Periscope" is a very popular wartime film.
But, one way or another, none of these films are 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 and tanks. Thanks to it, you can conduct surveillance from cover. It looks like an ordinary pipe, with mirrors attached on both sides. They are located so that the path of light rays changes. The periscope can also be a hand-held or stereo scope. One way or another, it is used in military affairs. Now it becomes clear regarding the two above-mentioned war films. There they were talking about submarine captains.
This is a strange name for software, although it can be explained. The developers wanted to show the user that he can observe 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 go to Paris or New York and 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 broadcasts, but gather your circle and conduct broadcasts for them. This way, you meet new people, find friends with similar interests, learn a language and just travel without leaving your room.
Many people are still interested in what Periscope is: a social network or regular software? But everyone is already accustomed to answering this question in their own way. Those who use Periscope for communication can confidently 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 believe that Periscope is more addictive than other social networks. This is due to numerous broadcasts. For example, if a photo on Instagram can be seen tomorrow, then you won’t be able to watch the broadcast later. It will start at a certain moment and will force you to abandon all your affairs and bury yourself in the smartphone screen.
Likes
Many users believe that it is through Periscope that one can look real. Videos are recorded instantly and published immediately. You can’t duplicate anything, much less cut it out.
To gather an army of fans around you, you need to broadcast regularly. Then, in addition to subscribers, you can collect a lot of “hearts”. To find interesting broadcasts, the program will recommend you random users.
But you will never understand what Periscope is unless you try this application yourself. We'll look at how to work with it next.
To get started, download
It is clear that before you start using the software, you need to install it on your gadget. To do this, go to the application store. For devices with the iOS operating system, go to the App Store, for Android OS, to the Play Market, and for Windows Phone, go to the Windows Phone Store. Enter Periscope into the search and click “install”.
Registration
Now that the new application icon has appeared on the desktop, select it and go into the software. Before we start, the program will tell us what Periscope is. We will see a slide show demonstrating our capabilities.
We need to select “get started” and we will be redirected to “register or login”. Since you are a new user, you will have to create an account. This can be done in two ways:
- Via Twitter.
- Using a phone number.
If you are a Twitter user, then registering will be easy for you. To do this, click “login via Twitter”. The program will automatically redirect you to its first tab. If you do not have your Twitter account information 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 and enter a number. Next, you will receive an SMS on your phone containing a confirmation code.
Registration does not end there. Before us is your future profile. Now you just need to fill it out. Enter your first and last name, also come up with a username (nickname), and add your photo.
Find and don't give up
Now that we are registered, I want to test the program. To do this, we need to find interesting users. The first tab will contain those you have subscribed to, and below are recommended broadcasts. The first three of them are new people, and below are the ones you've already watched.
Always be in the know
If you missed the broadcast, it will be available for another 24 hours. Also with the people you recommend. Those who are currently online will not always be displayed there. Sometimes the software recommends viewing already completed streams. The recording 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. You will be presented with a world map with a huge number of points. These are all the broadcasts that are currently happening around the world. You can select, for example, your city and see the people who are currently streaming, perhaps your friend or neighbor will be among them.
A periscope is a device with which you can observe objects outside our field of vision. For complex and precise observations, complex and precise instruments are made. In these cases, periscopes are equipped with a very complex optical system. However, for amateur purposes, you can construct a simple periscope from two pocket mirrors. It will allow you to penetrate the secrets of life of shy birds and other animals.
The proposed design has an important additional advantage: the periscope can be significantly lengthened if the object of interest is hidden behind a high obstacle. The necessary materials are sold in stationery and haberdashery stores. You will need two sheets of flexible cardboard and two pocket mirrors. The shape of the mirrors does not matter - they can be either round or rectangular. - but definitely the same.
In accordance with the size of the mirrors, glue two tubes about 50 cm long from cardboard or paper, and one of them should be slightly larger in diameter so that the tubes fit into each other. (If you have rectangular mirrors, then, naturally, the “holders” in cross-section can be square).
When the glue dries, cut one hole in the side walls of the tubes, at their ends, with a sharp knife. Moreover, make the hole through which you will look into the periscope with a diameter of approximately 1 cm. And the hole in the second tube should be the same size as the mirror inserted into it.
Cutting a hole in a tube with a square cross-section is very simple, but if the cross-section is round, the matter is more complicated. It is very important to keep in mind that the center of the holes must coincide with the center of the mirrors. Glue sun protection devices to the holes; they make observations much more convenient.
From pieces of cardboard or foam plastic, make two stands with holders for setting the position of the mirrors in the tubes.
After the glue connecting the stands, holders and Mirrors has dried, the finished units of our periscope are inserted into one another. And again, it is necessary to precisely adjust their position in relation to the holes cut in the side walls of the tubes. The mirrors should be at an angle of 45° to the longitudinal axis of the device and direct the observed image as shown in the figure.
Before the final installation of the periscope, one more operation needs to be performed - painting. The internal surfaces of the periscope are painted black, for example, with drawing ink. This improves observation conditions. Paint the outside of the periscope with gray or gray-green water-repellent paint. These colors are maximal, they blend well with surrounding objects.
ROMAN KOZAK
Magazine “Technology Horizons for Children” No. 8-85.