Anti-Eavesdropping Film


Anti-Eavesdropping Film

    At present, high-tech monitoring methods emerge in an endless stream, and one of the most concealed methods is “laser eavesdropping”.

    Sound is produced by vibration, and sound also causes surrounding objects to vibrate. Laser eavesdropping technology refers to emitting a beam of laser invisible to the naked eye, hitting objects near the sound source, collecting and analyzing the vibration of the object caused by the sound source, so as to restore the sound and achieve the purpose of monitoring with the laser. The laser anti-eavesdropping film achieves the purpose of preventing laser eavesdropping by blocking the laser of the laser eavesdropping device.

    After years of development of eavesdropping technology, a variety of eavesdropping devices have been developed. There are roughly the following types: miniature microphone bugs, radio wave bugs, line carrier bugs, telephone bugs, cell phone bugs, and laser bugs. The first several eavesdropping methods are relatively easy to evade, and can be protected through institutionalized management and on-site inspections. However, the laser eavesdropping device does not interfere with the eavesdropping scene, the light wave is invisible, and the eavesdropping distance is long, and it is not easy to be found, so the harm caused is particularly serious.

    The laser eavesdropping gun can also reflect a laser light through the window glass of the room, or an object in the room, such as a filing cabinet, clothes hanger, and flipchart, etc., and then demodulated by the receiver, it can clearly restore the voice of everyone in the room. 

    Laser bugs appeared late, are hidden, have low exposure, and are often ignored by many departments. Therefore, it is imperative to increase laser protection means in high-risk locations such as important departments.

Principle of laser bug

    The system emits an invisible laser beam, which irradiates the object near the detected source information, and through related processing, it can restore the sound information at a distance of more than one kilometer.

    Features: non-implantation, non-contact, non-inductive detection, long working distance, and little influence by electromagnetic waves.

The schematic diagram

The working mode

anti-laser eavesdropping technology and application

    Laser eavesdropping blocking film has been successfully used in many secret rooms and other units.

    The laser anti-eavesdropping technology mainly uses the laser eavesdropping film blocking technology to absorb the laser light irradiated on the window glass, so as to achieve the purpose of blocking the interference of indoor voice vibration on the laser irradiation, and realize the purpose of anti-laser eavesdropping.

    The laser eavesdropping blocking film is composed of infrared absorber, resin matrix and auxiliary agent.

The resin matrix is mainly used as a film-forming substance, which has the function of bonding other components to form a film layer. Although it does not have the function of absorbing infrared rays, it plays a decisive role in the physical and mechanical properties of the film layer.

    Laser eavesdropping blocking film preparation technology includes coating technology, physical vapor deposition, chemical vapor deposition and so on. Among them, physical vapor deposition also includes methods such as vacuum evaporation, magnetron sputtering and ion plating.

    All components that make up the coating liquid must be mixed, dissolved, dispersed and other processes to obtain the smallest dispersed particle size as possible, and then one or more coating methods are used to uniformly coat the coating liquid delivered to the coating head on the coating head. The substrate is then heated to evaporate the solvent, or the coating is cured with UV light or electron beams to produce the final desired film.

The principle of laser eavesdropping blocking film

    In the atoms that make up the substance, there are different numbers of particles (electrons) distributed in different energy levels. The particles at the high energy level are excited by some kind of photons and will jump from the high energy level to the low energy level. It will radiate light energy of the same nature as the excitation it, the energy level with the lowest light energy is called the ground state, and the other energy levels are called excited states. The state in which the electron is “away” from the nucleus and is no longer attracted by the nucleus is called the ionized state, and the energy level of the ionized state is zero (the energy absorbed by the electron is the largest when it transitions from the ground state to the ionized state).

Three laser wiretap blocking film test

    German Polytec company RSV-150 long-distance laser vibrometer, the carton used to reflect the vibration of the acoustic signal as the sound signal source.

test demo

test demo

Test Results

The sound signal recovered from a distance of 700 meters without a blocking film.

There is a sound signal recovered by the blocking membrane 5 meters away.



Total Solar Energy Transmitted

Total Solar Energy Rejected

Total Solar Energy Reflectance

Total Solar Energy Absorbed

Visible light Transmitted

Visible light Reflected exterior

Visible light Reflected interior

Infrared rejection

UV rejection

Visible light Glare reduction

Solar heat Gain coefficient

Shading coefficient

Coefficient of conductivity


“U” factor


















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