#Video Peephole
Video Peephole — a phenomenon of Russian television surveillance.
Chura Nikolay Iosifovich
VIDEO PEEPHOLE — A PHENOMENON OF RUSSIAN TELEVISION SURVEILLANCE
A video peephole, as a specialized television camera that has the external appearance of a typical door peephole and is located in the door instead of it, is essentially a purely Russian invention.
Its appearance in our country is due, as it seems to us, to obvious socio-economic and historical factors that have developed in Russia over the past decade.
First of all, this camera is for hiddeninstallations, and hidden installation of equipment is widespread in Russia not at all due to the general “spy mania”, but as a result of the desire to preserve the equipment and protect it from sophisticated domestic vandalism.
In the West, the population is content with video intercoms.
In developed countries, a law-abiding citizen stands at the intercom intercom and allows himself to be examined without hindrance.
Therefore, the horizontal viewing angle of the video intercom camera of 70-90 degrees with infrared illumination of the center of the field of view in the near zone is quite sufficient.
In our conditions, when you ring the doorbell, you can feel relatively calm if you can see the entire staircase from floor to ceiling, and preferably the flights of stairs, from the back room of the apartment.
Given the fragmentary and episodic lighting of our entrances, invisible infrared illumination is required with a range of at least 3-4 m across the entire angle of view of the video peephole.
For known reasons, the light source should also be maximally disguised.
Such demands of life have pushed to the wide use of infrared illumination with camouflaged radiation sources.
The first video peepholes, which appeared in our country in the first half of the 90s, were frameless mono-board CCD television cameras with a black-and-white image and a standard built-in lens. From the outside of the door, the lens was hidden behind a decorative element from a regular door peephole.
In addition to the absolutely insufficient viewing angle, the camera lens is quite easily visually recognized in such a video peephole.
Soon, afocal optical attachments for the camera lens were developed, providing observation in viewing angles of up to 180 degrees horizontally, and in appearance almost identical to conventional door peepholes.
With the help of such attachments, almost any frameless or small-sized body-type TV camera with a built-in lens can be turned into a video peephole.
Two groups of video peepholes have been practically defined — large (160 — 180 degrees) and medium (120 — 90 degrees) viewing angles. In accordance with this, a combination of a TV camera lens and an optical attachment is selected.
Along with afocal optical attachments, specialized extended wide-angle lenses with image plane transfer have become somewhat widespread.
Such lenses allow the video peephole to be installed in the existing opening of a standard door peephole with a minimum amount of structural modifications to the door.
In this case, the entire camera is located outside the door. Such an optical system, with satisfactory image quality, has a high cost, often much higher than the cost of the camera.
When implemented in a makeshift manner, it has a limited field of view and a significant loss of resolution, especially at the edges of the image.
The image quality of a typical mid-priced video peephole significantly exceeds the image quality of a regular door peephole.
This is especially noticeable when using a monitor or TV with a diagonal of more than 10 cm (9 ″) for surveillance.
At the same time, there are consumers who want to retain the ability to visually observe along with video surveillance.
Since two peepholes on the door look unnatural, in this case it is advisable to install a camera with a pin-hole lens with a lens opening of about 1 mm. Such cameras are currently widely used in Russian-made video intercom intercom panels. It should be noted that most of the proposed cameras, strictly speaking, are not pin-hole cameras, since they simply have a single-lens lens with an aperture diaphragm. The typical angle of view of such a lens does not exceed 74 degrees.
A viewing angle close to 90 degrees requires replacing the lens with a more advanced one, and therefore more expensive. Larger angles are almost impossible to achieve. Naturally, such a TV camera is inferior to a video peephole in both viewing angle and sensitivity, and with the simplest lens, in resolution, especially at the edges of the image.
Another solution to the problem is to use a complex optical system with a beam splitter in the path.
In this case, part of the light flux coming for visual observation is branched off through a dividing prism to a television camera. Due to the complexity and extremely high cost, such devices exist as individual samples and have not found wide application.
When choosing the viewing angle, you have to take into account the location of the door. If the door is on the side wall of the corridor, it is advisable to use a video peephole with a maximum viewing angle. In this case, the space in both directions along the corridor will be clearly visible, including the walls adjacent to the door.
The width of the corridor will naturally limit the range of the required observation to values of 1.5-2 m, which is quite realistic for wide-angle video peepholes. On the other hand, for a video peephole of a door at the end of the corridor, a viewing angle of no more than 120 degrees is preferable, allowing effective observation at a distance of more than 3 m.
The entire variety of video peepholes currently offered can be divided into several groups, differing in technical parameters and cost.
The most common models are characterized by the use of CCD cameras with a built-in lens f = 6 or 3.6 mm and an afocal attachment. Combinations of different lenses and attachments allow for horizontal/vertical viewing angles of 90/67, 120/90 or 170/120 degrees.
1. Low-cost, ultra-miniature video peephole based on a frameless camera using CMOS technology
- Resolution 240 — 300 TVL
- Sensitivity 1 lx
- Internal electronic shutter 1/50 — 1/2000 or 1/6000
- Power consumption no more than 20 mA/7-16 V
Advantages:
- low cost;
- small size (practically does not exceed the dimensions of the attachment);
- economical.
Disadvantages:
- mediocre image quality (low resolution);
- insufficient range of illumination compensation.
2. Average quality video peephole
Optimal image quality, low-light performance. Effective use of IR illumination.
- Resolution 380 — 420 TVL
- Sensitivity 0.5 — 0.1 lux
- Horizontal/vertical viewing angle 90/67, 120/90 or 170/120
- Internal electronic shutter 1/50-1/100000
- Power consumption no more than 150 mA/12 V
Depending on the design of the camera, there are at least three main options for a video peephole:
2.1. Option with a frameless single-board camera.
Figure 1 shows installation in a hollow metal door.
Advantages:
- low cost;
- short length, allowing the video peephole to be mounted in a standard door without protruding elements.
Disadvantages:
- the need for a fairly large hole in the door is due to;
- the transverse dimensions of the camera (from 44×44 mm to 28×28 mm).
Fig. 1. Installing a video peephole in a hollow metal door.
2.2 Option with a housing single-board camera.
Fig. 2 shows installation in a solid wooden door.
Advantages:
- good protection against possible damage during installation;
- acceptable thermal insulation when installed in exterior doors.
Disadvantages:
- somewhat large dimensions and cost.
Fig. 2. Installing a video peephole in a solid wooden door.
2.3 Option with a cylindrical camera.
“Quick-installation video peephole”
Fig. 3 shows the mounting of the video peephole in a solid wooden door using an external nut, Fig. 4 shows the mounting of the video peephole in a metal hollow door using a cover with thrust rings.
Advantages:
- convenience and speed of installation.
Disadvantages:
- as a result of the long length of the camera, its rear part protrudes from the door;
- even higher cost, due to the more complex design of the camera and attachment.
Fig. 3. Fastening the video peephole to a solid wooden door using an external nut.
Fig. 4. Fastening the video peephole to a hollow metal door using a cover with thrust rings.
3. High-quality video peephole
Good image quality, low-light performance. IR illumination is very effective.
It is advisable to use high-quality optics.
- Resolution 450 — 600 TVL
- Sensitivity 0.05 — 0.01 lux
- Internal electronic shutter 1/50 — 1/100000
- Power consumption no more than 200 mA/12 V
Depending on the design of the camera, the video peephole can be made either without a frame or in various framed versions described above.
Advantages:
- image quality allows for observation at maximum range in maximum viewing angles.
Disadvantages:
- high cost.
4. Color video peephole
- Resolution 330 — 400 TVL
- Sensitivity 1.0 — 5.0 lux
- Internal electronic shutter 1/50 — 1/100000
- Power consumption no more than 300 mA/12 V
Advantages:
- increased information content of color images.
Disadvantages:
- relatively low sensitivity;
- inability to use IR illumination;
- high cost.
Video peepholes based on CMOS technology cameras have not yet found wide application despite their low cost. This is explained, first of all, by their insufficient resolution. Therefore, at present, CMOS cameras are used mainly where size and cost-effectiveness are decisive factors.
Video peepholes of medium quality have received the greatest distribution and popularity. They are characterized by an optimal price/quality ratio.
Moreover, the frameless version is notable as the cheapest, while maintaining fairly high technical characteristics.
The case mono-board version is preferable for single metal, wooden and, of course, street doors. In the latter case, the case serves as additional thermal insulation. A significant advantage of these video peepholes is their small thickness, due to which they can be completely built into the door.
Quick-installation video peepholes are the most popular due to the integrity of the design, simplicity and ease of installation. It is interesting that their popularity is maximum both among amateurs who are going to install the product themselves, and among professional installers who value their time and labor costs.
High-quality video peepholes with color images can currently be considered mainly as technical exotics, except for those cases where color is a decisive information quality. The minimal need for them is due, first of all, to their high cost.
Many models of TV cameras used in video peepholes have modifications with a one-way audio channel (active microphone). It would seem that such a combination can allow you to monitor the situation in front of the entrance door by ear, and if the acoustic environment is satisfactory, in the entire entrance.
However, the built-in microphones of body-mounted TV cameras have relatively low sensitivity, and most importantly, they are located in the camera body behind an extremely small hole, usually about 1 mm.
In the case of a video peephole, this hole is located quite far from the front surface of the door.
The forced use of a sound guide additionally reduces the sensitivity of the microphone, significantly worsens speech intelligibility as a result of uncontrolled distortions of the frequency response.
These shortcomings are even more inherent in cylindrical television cameras, where the microphone hole is located on the side surface of the housing cylinder.
Satisfactory results can be obtained with a remote electret microphone of a frameless television camera.
In this case, the microphone must be well vibration-insulated from the structural elements of the door, and in the case of a hollow metal door, sound-insulated from the interior. Otherwise, a high level of man-made and anthropogenic noise from the building, penetrating through the resonant structures of the door, is inevitable.
When setting a high volume on a video monitor located in the hallway, the system is prone to self-excitation.
Significantly better results can be obtained by using a separate active microphone installed on a load-bearing wall in an area with a minimal reverberation component.
In conclusion, it should be noted that the video peephole, as a purely Russian product, takes into account our national specifics well.
It is simple, relatively cheap and accessible, but at the same time a very effective means of round-the-clock TV surveillance for apartments and private houses.
A system with a video peephole, due to its simplicity, does not require maintenance and operational control, at the same time, in comparison with a video intercom, it has significantly higher video path characteristics.
Thus, Moreover, if there is an absolute need for two-way communication, the video peephole can easily be used as a video channel in a video intercom system.