- The history of the peephole
- Device and types of door eyes
- How to choose the right door peephole
- Reverse door peephole
- At the end
In this Article: Peephole – History; design and types of eyes; how to choose a door peephole; reverse door peephole; a stranger behind your door – what to do?
The front door to the house separates the personal space of its inhabitants from the street, depending on the strength of the door leaf and frame, it reliably prevents strangers from entering the house. There is only one problem – the stronger and more reliable the door leaf, the less opportunities to find out who is on the threshold and knocking on the house. Most often, these strangers are utility workers or neighbors, but how can you identify them without opening the door? The easiest way to establish the identity of a visitor is with the help of special accessories – a peephole.
The history of the peephole
What is a peephole in essence? A small hole in the door, enough to more or less make out the opponent behind the door leaf, with the condition that he could not use this hole to enter the room behind the door or cause some harm to the abodes of the house through it. The prototype of the modern door peephole for several centuries in a row was a rectangular opening in the door, located at human eye level and covered from the inside of the room by a sliding panel or hinged cover, the opening of such an opening was usually covered with a metal grate. A peephole with a sliding lid remains popular in penal institutions to this day.
On the territory of the USSR at the beginning of the last century, the function of a door peephole was performed by a mailbox – the receiver of letters was located on the inner side of the door, letters and other correspondence entered it through a narrow rectangular slot in the door leaf, blocked from the outer side of the door by a hinged cover. Through this slot, the tenants of the apartment could see who was on the threshold – for this it was necessary to move the flip cover with a finger or some narrow and elongated object. The disadvantages of such a peephole are obvious – surveillance through a slot in the mailbox could not be hidden from the visitor and an attacker could easily prevent the cover from opening.
At the beginning of the 20th century, inventors of the entire planet worked on the invention of an effective door peephole – what designs they did not create! There were options for door peepholes with a hollow, water-filled magnifying glass, with a one-sided (external) mirror surface, under observation with two eyes at once, etc. But all the invented eyes had one common drawback – the small viewing angle did not allow to really see the visitor, even if he was a few steps from the door leaf.
The modern door peephole with a special lens that allows you to see the visitor behind the door in full growth, appeared thanks to the American scientist, inventor and writer Robert William Wood.
Robert Williams Wood, American experimental physicist
It was he who in 1906 created the fisheye lens – the basic element of all wide-angle lenses of our time. However, for 44 years from the date of invention, the wide-angle lens created by Wood did not enjoy much popularity, and only from the beginning of the 60s of the last century, manufacturers of camera lenses paid attention to it, followed by companies producing door fittings. Thus, a full-fledged peephole was created about 70 years ago..
Device and types of door eyes
Structurally, any door peephole consists of a body, an eyepiece through which a staircase or porch is inspected, as well as a lens located on the outside of the door. The part of the peephole body, on which the lens is installed, has retaining protrusions that prevent it from being twisted outside the door. The eyepiece is usually closed off by a flap or sliding shutter attached to the body of the eye. In some models, the role of the shutter is performed by mirror coating on the lens, which prevents the passage of light rays in the opposite direction, i.e. the observer from the outside of the door will not know whether someone is looking through the peephole or not. However, the mirror “shutter” passes the light flux worse and interferes with observation in the dark – the light source on the staircase will look like a bright spot that illuminates the visitor’s image.
The minimum number of lenses in the door peephole is 2, the maximum is 15. The number of lenses depends on the length of the peephole body; the longer it is, the more lenses are needed for a quality view. The optimal set of lenses for a door peephole up to 55 mm long, providing a 180o viewing angle, is performed in the following sequence: fisheye lens; two consecutive minus (reducing) lenses, the focuses of which are directed towards each other; plus (magnifying) lens in front of the eyepiece.
Cheap models of door eyes contain plastic lenses – they are more resistant to mechanical damage, but lose transparency over time and transmit less light flux than glass lenses. Optical elements of more expensive models are made of ordinary, special optical glass or glass intended for glasses – the latter two types of lenses are much stronger and better transmit the light flux.
As already mentioned, the standard door peephole length is 30-55 mm. There are also “elongated” models with a body length from 55 to 100 mm and “extra-long” models with a body length of more than 100 mm (it is most difficult to find them in retail outlets). The diameter of the body of the eyes of different models and manufacturers is usually from 13 to 26 mm.
The design of the security door viewers is distinguished by a large number of lenses (at least 12) and an additional insert of armored transparent glass. These eyes are considered bulletproof, i.e. a bullet fired from a short-barreled rifled firearm (pistol) is guaranteed to get stuck inside the peephole.
Interesting models are designed for double doors – for example, metal exterior and wooden interior. Such a door peephole consists of two parts: the first is built into the outer door leaf, the second into the inner leaf. Two parts of one peephole located in one line allow observing the visitor without opening the inner door, i.e. the luminous flux is transferred from the external optical unit to the internal one, equipped with an eyepiece. The quality of the light flux transmission and, accordingly, the angle of view from the lens on the front door to the eyepiece on the inner sash depends on the distance between them – 20 mm is the most optimal.
There are also door peephole models in which the lens and eyepiece are at different heights, i.e. not on the same line – they are also called periscopes. Light transmission in the eyes of this design is due to a system of mirrors installed inside the body, i.e. periscope eyes will also protect the inhabitants of the house from a pistol shot.
The eye-periscope is convenient if there are children in the house who are unable to reach the upper eyepiece.
There are two models of such door peepholes-periscopes: the lens located in the upper quarter of the door leaf, while the eyepiece is at the level of two-thirds of the door; the usual location of the lens (at the height of two-thirds of the door leaf), the first eyepiece is also at this height (i.e. in line with the lens), the second eyepiece is lower – about one-third of the door. The latter type of design is convenient if there are children in the house younger than middle school age who are unable to reach the upper eyepiece.
Among modern models there are special panoramic eyes. The panoramic viewer lens is split into left and right lenses, which receive light from a wider horizontal angle (panoramic image) than all other door viewers. The eyepiece of panoramic eyes does not require the classical method of observation – we close our left eye and, bringing the right eye closer to the eyepiece, we observe – the light flux passing through it creates a clearly visible image on the large eyepiece already from two steps, and the observer does not have to stand strictly in a straight line to the eyepiece.
In addition to the described designs of door peepers, there are observation devices of the most complex device – secret peepholes. It is absolutely impossible to detect their position from the outside of the door – the lens is installed not on the door leaf, but on one of the ends of the doorway, while outwardly it does not in any way resemble the usual lens of a door peephole and looks like a small head of a nail or screw. The observation eyepiece is also located not on the door leaf, but on the wall – this complex design was once developed for the special services. However, such an observation device cannot be found in free sale, which means that it is almost impossible to purchase it..
How to choose the right door peephole
Before you go in search of a suitable door peephole, find out the thickness of the entrance door, taking into account, if necessary, the upcoming insulation of the door – the upholstery will increase the thickness of the door leaf. If the reason for buying a new peephole was a malfunction of the old one, it is necessary to measure the diameter of the existing hole in the door.
Pay attention to the number of lenses and the material from which they are made – the worst option would be 2 plastic lenses. The maximum viewing angle of such a peephole will not exceed 90about, those. will be too small, and plastic lenses will significantly lose transparency and turn yellow in two years.
On the Russian markets there are door peepholes produced by the Chinese company Apecs, the Spanish companies Mirilla and Amig, the German Abus, the Belarusian manufacturer of optics BelOMO and the Russian company NPF Shvel. The cheapest eyes are made in China and Belarus – from 30 rubles, Russian – about 80 rubles, Spanish – from 110 rubles. The larger the viewing angle given to its owners by this model of the door peephole, the higher its cost – the average cost of a peephole with a 180-200 ° viewing angle and with four glass lenses will be about 700 rubles. The cost of high quality models – bulletproof, panoramic, etc., with lenses only made of “spectacle” glass – starts at 1,000 rubles. and higher.
Installing a door peephole of a classic (linear) design will not be particularly difficult – most manufacturers of door fittings include cardboard templates for marking the hole in the door in the door peephole kit. Before buying a model you like, make sure that the outer nut framing the lens is equipped with locks that prevent the peephole body from being twisted outside the door!
Advice: if you order an entrance metal door for your house from performers, you should not rely on them for the point of placing the door peephole – you do not want the peephole in a new and far from cheap door to be somewhere at chest level! Be sure to visit the workshop of the company from which you ordered the door and decide on the optimal height for placing the door eye.
Reverse door peephole
There are two types of such eyes, and any of them will not please the inhabitants of the house, because the reverse eyes are designed for covert observation of them. The classic peephole is an ordinary peephole, only installed in reverse, i.e. the lens into the apartment, and the eyepiece out. Such a peephole is easy to see, unless it is hidden in the decoration ornamentation. But the more complex and modern version of the reverse peephole deserves special attention..
In 2000, the American corporation “Tab Tabacchi” began to develop an optical device that allows you to look into any house through a peephole, counting on its popularity with law enforcement. By 2002, the peephole was invented and patented – a special combination of lenses in its housing made it possible to change the direction of the light flux and turn any peephole against its owners. Everything is simple – you just need to install the reverse peephole close to the lens of the door peephole and look through its eyepiece, everything that happens inside the room, where the front door leads, will be open to the gaze of an outside observer. Moreover, some models of reverse eyes allow video recording of what is happening indoors! The cost of the back peephole varies from $ 90 to $ 150, and if earlier these optical devices were available only to intelligence officers, today anyone can purchase them..
A reasonable question arises – how to resist observation through the reverse peephole? There is only one way – to equip the door peephole with a hinged or sliding shutter that covers the eyepiece of the peephole all the time until it is used by the inhabitants of the house to observe the staircase or porch. Eyepiece shutter – a simple but effective remedy!
At the end
A knock on the door – you look through the peephole and see a person absolutely unknown to you. What should you do?
You have the right to demand from an unknown person who claims to be an employee of a certain municipal service or police, to show you an identity card. Ideally, the front door should be equipped with a chain that does not allow you or an unknown visitor to open it completely – write down on a piece of paper the data from the identity card presented to you.
The next step is to contact the organization the stranger claims to be speaking on behalf of. In doing so, use the phone number you received through the helpdesk, which you contacted via the Internet or by the phone number in the directory – do not rely on the combination of numbers given by the visitor, because it could be the phone number of his accomplice.
Demonstrate to a stranger your willingness to dial the phone number of the law enforcement services – rescue service “01” and police “02” at any moment. It is more convenient to use a cellular connection, but you need to know exactly the combination of calling emergency services that is allowed by a given cellular operator. An attacker, seeing your willingness to dial the emergency number, will not dare to continue trying to break into your home.