Principles of construction of the laser radiation sensor

DOI: 10.31673/2412-4338.2020.019724

Abstract

A laser microphone for acoustic surveillance or a device for long-distance laser listening is a high-tech device for collecting information, which uses an invisible infrared laser beam, which is used to eavesdrop on the conversations of the target object. This device is a fairly efficient device and allows the operator to listen to audio signals coming from any target room having at least one window, at a considerable distance of 300-1000 meters. Such a device is specifically designed for use in situations where entry into the premises of personnel to place the eavesdropping device in the target area is undesirable or impossible. The laser microphone is difficult to detect during operation because the infrared laser beam is completely invisible to the naked eye. If you know that laser listening equipment is used, then finding it is not difficult. Its reconnaissance feature is a laser spot on the window glass with a size of 2 to 20 mm. It is not visible to the naked eye, but in any night vision device this spot will look like the second sun. The shape of this spot will give additional information about the location of the laser source: a round spot - the source in front of the window, an ellipse - on the side. This article is devoted to the principles of detection of laser listening equipment by a passive sensor, which is placed in a controlled room separately or as part of other technical means of information protection. This sensor simulates the receiving part of a standard laser microphone. To detect such laser radiation, an optical system, a photodetector (FPP) and an electronic circuit with a threshold device are required, and a number of features must be taken into account.

Keywords: laser microphone, laser, photodetector, laser listening equipment, information security.

References
1. Durduran, T., Choe, R., Baker, W. B. & Yodh, A. G. (2010) Diffuse optics for tissue monitoring and tomography. Rep. Prog. Phys. 73, 076701.
2. Hemani Kaushal, Georges Kaddoum. (2017) Applications of Lasers for Tactical Military Operations. Digital Object Identifier 10.1109/ACCESS.2017.2755678. Vol. 5.
3. Laser Window Bounce Systems Url: https://russian.alibaba.com/product-detail/laser-listening-50011848821.html. Date: 25/05/2020.
4. Matthew S. Hoehler and Christopher M. Smith. (2016) Application of Blue Laser Triangulation Sensors for Displacement Measurement Through Fire. Meas Sci Technol. Nov 2016, 27(11): 115201.
5. Raf Vandersmissen. Laser beam profiling and infrared cameras. MKT‐2017‐AN012‐R001 Belgium, Leuven. Date: 29/06/17. Page 1 of 10.
6. Udd Eric, Spillman William. (2011) Fiber optic sensors an Introduction for Engineers and Scientists. John Wiley & Sons, Inc.: 506.
7. Yun Ying Wang, Qi Lan Huang, Gong Yuan Yang. (2011) Advanced Materials Research (Volume 298). July 2011: 35-39.
8. Baranochnikov M.L. (2017) Radiation receivers and detectors. Part 2: Optical radiation receivers. Moscow, DMK Press: 586.
9. V.I. Oleynik, V.N. Shmarov. (2005) Some issues of reflection of laser radiation from rough metal surfaces. Information processing systems. 3 (43).
10. І.О. Braginets, Yu.O. Masyurenko. (2019) Fiber optic sensor for linear measurements. Technical Electrodynamics (Institute of Electrodynamics of the National Academy of Sciences of Ukraine). 6: 81-86.
11. Light V.N., Galun B.V., Sankov O.V. (2011) Optoelectronic elements and devices of special-purpose systems. - Novosibirsk: Publishing House of NSTU: 455.
12. Laser light sensor. Url: https://www.robostore.com.ua/moduli-i-datchiki/datchiki-osveshennosti/sensor-lazernogo-izlucheniya). Date 25.05.2020.
13. Earth's laser scanning technologies are opening up new possibilities. (2015) Knowledge is power. 2.
14. Yu.M. Klimkov, V.S. Mayorov, M.V. Khoroshev. (2014) The interaction of laser radiation with matter: a training manual. Moscow MIIGA&K: 108.