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As you know, for every action there is a counteraction. As soon as a new «bug» appears, specialists begin working on creating means of searching for and neutralizing wiretapping. Over time, security devices develop, improve, acquiring more and more useful functions and becoming more and more convenient to use. Similar processes occurred with devices for detecting hidden video cameras.
Various types of spying (hidden photography and video recording, use of night vision devices, etc.) have always attracted spies; a lot of effort was spent by criminals on their creation and improvement. The size of video cameras over time became smaller and smaller, and the characteristics of the resulting image improved. Wired and wireless video cameras, cameras transmitting images via radio, and cameras that can be turned on remotely — according to the needs of the spy appeared. As a result of all the work, today a hidden video camera can be discreetly installed literally anywhere: in furniture, walls, an item of clothing — it all depends on the imagination of the intruder — and filming can be carried out almost unnoticed by a person.
There are several currently known ways to detect these numerous video cameras:
- using a field indicator (if the information from the camera is transmitted via a radio channel);
- optically (a laser beam sent from an optical detector is reflected from the lens of the video camera);
- an electromagnetic camera detector.
The first type of devices are quite common in the West, but they are ordinary field indicators, so we will look at the last two in more detail.
Optical detectors operate on the basis of the retroreflection effect. This effect can be described as follows. Since all optical surveillance devices (in our case, we are talking about cameras) contain a light-sensitive element (for example, a CCD matrix), a beam directed at this element will be reflected from it and return back to the source, i.e. to the detector. Thus, the operator sends a probing beam to the supposed location of the hidden video camera, and if the camera is actually installed, he will see a glare reflected from the light-sensitive element. However, in addition to the desired signal, radiation from other elements will fall into the field of view; to get rid of them, a system for filtering out such noise is included in optical detectors. In some devices, an IR-transmitting filter is used for this. In this case, the parameters of the laser beam (or LED backlight) also play a large role in detection; during production, they are carefully selected empirically.
This operating principle has its advantages and disadvantages: on the one hand, it allows detecting optical devices of various types (from sniper rifles to binoculars), and on the other hand, means of counteracting optical detectors have already been invented — special light filters for filtering out light waves of a certain length.
There is another way to detect video cameras — using electromagnetic detectors. To understand the operating principle of such devices, it is necessary to say a few words about the structure of hidden video cameras. As has already been noted earlier, in the vast majority of modern hidden video cameras, a CCD matrix (charge-coupled device) is used as a photodetector (a device for transforming a light signal into an electrical one). It is serviced by a processor, i.e. a signal reader, which then generates a video signal. The processor contains an oscillator that emits at a certain fixed frequency. The oscillator itself emits at a certain frequency over a short distance, but it has side emissions consisting of harmonics of the fundamental frequency. These harmonics are multiples of the fundamental frequency and also emit over short distances (the higher the harmonic, the shorter the distance), but among them there are harmonics that penetrate the body of the video camera very well. A certain type of camera emits well at certain harmonics, this is usually determined experimentally, and then the resulting radiation image is recorded in the memory of the video camera detector. The number of harmonics recorded in the memory for each type of camera may be different.
The range of electromagnetic detectors depends mainly on the type of camera and how the camera emits. Poorly emitting cameras are usually located at a distance of about 3 m, and well emitting ones — up to 50, the average detection range is 7-10 m. That is, these characteristics are basically the same for all electromagnetic detectors.
The search time for electromagnetic detectors largely depends on the number of video camera types stored in the detector's memory. Modern electromagnetic detectors are capable of searching for video cameras almost unnoticed by others: most of them have light, sound and vibration indication. There are also devices equipped with a hidden antenna, which allows for a search to be conducted as unnoticed as possible. However, it is worth noting that the antenna's proximity to the human body significantly reduces its sensitivity; it is more convenient to conduct a search by holding the detector in an outstretched arm in an open space. Some models provide the ability to continuously monitor the premises and send data on a suspicious signal to a remote PC or exchange information with a PC via a mini USB port in the event of detection, which allows you to download database and software updates. Optical detectors are not capable of conducting a hidden search, and this can serve as a serious argument in favor of electromagnetic devices. A person inspecting a room using an optical detector will definitely not go unnoticed, which in many cases may be undesirable. It should also be noted that searching using optical detectors requires time, as well as patience and extreme attentiveness of the operator. However, optical detectors, unlike electromagnetic ones, are capable of detecting all types of video cameras, regardless of whether they are turned off or on. In conclusion, I would like to say that when choosing the type of detector, it is necessary to start from the task that needs to be performed: in a situation where the speed and stealth of the search do not play a fundamental role, you can use optical detectors, the price of which is at least two times lower than the cost of electromagnetic devices.
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