RU2141676C1 - Sonar system for optico-acoustic examination of underwater object - Google Patents

Abstract

FIELD: underwater acoustics, acoustic and optical monitoring of noiseless underwater objects. SUBSTANCE: essence of invention consists in formation of laser beam with hollow core that heats surface of object which begins to emit acoustic waves as result of it. Zone with increased temperature along beam periphery is created in aqueous medium which leads to formation of sound conducting channel over which acoustic waves go to acoustic converter that forms acoustic image of object by means of reflector and scanner. Proposed sonar system includes video camera recording image and programming device controlling operation of sonar system. EFFECT: increased examination efficiency of underwater objects thanks to use of its optical and acoustic characteristics. 2 cl, 1 dwg

Description

 The invention relates to the field of hydroacoustics and can be used for acoustic and optical monitoring of silent underwater targets.

 A device of a similar purpose is known, comprising an optically matched laser, a hollow core laser beam shaper and a deflector, as well as a hydrophone with a uniform directivity characteristic located on the laser optical axis behind the deflector.

 A disadvantage of the known optical-acoustic noise finder is the lack of an optical image of an underwater object at the output of the device and the inability to examine silent targets.

 Known sonar for optical-acoustic inspection of an underwater object, adopted as a prototype.

 The prototype contains an optically matched source of electromagnetic energy, an optical system and a deflector, as well as an acoustic transducer and an amplifier, a processing unit, and a recorder connected in series to it.

 The prototype is based on the formation of an acoustic signal near the underwater object when the object absorbs electromagnetic energy from a source located on the platform, and the reception of this signal by an acoustic transducer. Such a technique allows an acoustic survey of silent underwater targets.

 The disadvantage of the prototype is the lack of output of the sonar optical image of the underwater object and the poor spatial resolution of silent underwater targets due to the formation of a wide beam of electromagnetic energy.

 The technical result obtained from the implementation of the invention will be to increase the efficiency of optical-acoustic inspection of an underwater object by additionally forming along with the acoustic optical image of the target, as well as by increasing the spatial resolution when forming the acoustic image of the target by using a narrow laser beam.

 This technical result is obtained due to the fact that the proposed sonar for optical-acoustic inspection of an underwater object, containing an optically matched source of electromagnetic energy, an optical system and a deflector, as well as an acoustic transducer and an amplifier, processing unit, and recorder connected in series to it, additionally contains optically a scanner and an optical converter, as well as a software device and a video camera, compatible with the source of electromagnetic energy, when The electromagnetic energy source is made in the form of a laser, the optical system is in the form of a hollow core laser beam former, and an acoustic transducer with a uniform directivity characteristic located on the optical axis of the laser behind the scanner and deflector is used as an acoustic transducer, with the optical transducer installed in front of the deflector , and the software device is connected by its outputs to the optical converter, scanner and deflector, as well as to the reg sync inputs istrator and camcorders.

 The laser beam former can be equipped with a drive for its displacement relative to the axis of the laser, while the control input of the drive is connected to one of the outputs of the software device.

 The invention is illustrated in the drawing, which shows a block diagram of a sonar.

 The sonar contains an optically matched laser 1, an optical transducer 2 for converting the spectral composition of the laser radiation, a hollow core laser beam shaper 3, a rotary reflector 4, a deflector 5 and a scanner 6.

 There is also an acoustic transducer 7 with a uniform directivity characteristic mounted on the optical axis of the laser behind the scanner 6 and deflector 5, as well as an amplifier 8, a processing unit 9, and an acoustic image recorder 10 (the block connection diagram is shown in the drawing).

 The sonar includes a video camera 11, containing, in addition to the video head 12, a video amplifier 13, a processing unit 14, and an optical image recorder 15.

 The sonar also includes a software device 16, the outputs of which are connected to blocks 2, 3, 5, 6, 10, 15.

 The software device 16 can be made in the form of a command pulse generator, following at specified time intervals on the blocks connected to it.

 Laser 1 can be made in the form of a neodymium or ruby laser operating in the free pulse generation mode.

 The hollow core laser beam generator 3 can be made in the form of a telescopic mirror system, for example, in the form of successively arranged concave and convex mirrors, with the convex mirror facing the laser 1 and the concave mirror, which is made with a central hole and with the possibility of changing the mutual distance between mirrors (a similar embodiment of the laser beam former is not shown in the drawing, since it is known from the analogue).

 Shaper 3 can be mounted on an optical table equipped with a drive that is controlled by a command pulse of a software device 16 (these elements are not shown in the drawing).

 The remaining blocks of the sonar have no features.

 Sonar works as follows.

 The laser beam 17 is directed towards the underwater object under study 18. The software device 16 delivers command pulses to the operation of these blocks to the shaper 3, deflector 5, scanner 6 and the recorder 10 of the acoustic image.

 In this case, the shaper 3 forms a laser beam 17 with a hollow core. Partially absorbed in water, laser pulsed radiation forms in the medium a sound guide channel 19, characterized by an elevated temperature (and hence a higher sound refractive index) along the channel periphery. This ensures almost unhindered passage of sound signals of certain frequencies through the sound channel 19 from the object 18 for a period of several seconds.

 The underwater object 18 begins to “sound” under the action of the same laser pulse, which leads to heating of the surface of the object 18 and a local volume expansion of the irradiation zone.

 Since the deflector 5 and the scanner 6 simultaneously displace the beam 17 in space and scan it with an amplitude equal to approximately half the diameter of the beam 17, the sound signal from the object 18 will propagate through the sound guide channel 19 and reach the acoustic transducer 7 located in the hollow core of the laser beam 17 and in that place where scanning and the angular displacement of the beam by the scanner 6 and the deflector 5 begin. That is, the acoustic transducer 7 located quite close to the deflector 5 and the scanner 6 (in the drawing, not reflected), does not interfere with the movement and scanning of the laser beam 17.

 From the acoustic transducer 7, the signal is sent to the amplifier 8, the processing unit 9, to the recorder 10 of the acoustic image.

 At a certain point in time specified by the software device 16, command pulses are sent to the converter 2 and the synchro input of the video camera 11 (for example, combined with the recorder 15 of the optical image of the object), including blocks 2, 11 and disconnecting blocks 3, 6, 10.

 In this case, with the help of a drive (not shown in the drawing), the shaper 3 is shifted relative to the axis of the laser 1, and the scanner 6 enters the direct transmission mode of the laser radiation.

 If neodymium laser with a wavelength of 1.06 μm is used as laser 1, then a frequency doubler is used as converter 2, which converts the infrared radiation of laser 1 into green, which has the lowest absorption coefficient in water.

 Moving sequentially along the surface of the object 18, the laser beam illuminates it at various points. The camcorder 11 registers an optical image of an object 18.

 At a subsequent point in time, the software device 16 again puts the sonar operation into the registration mode of the acoustic image of the object.

 Thus, using a sonar, you can simultaneously obtain the optical and acoustic image of an underwater object, i.e. carry out optical-acoustic monitoring of the object with high spatial resolution.

Claims (3)

 1. A sonar for optical-acoustic inspection of an underwater object, containing an optically matched source of electromagnetic energy, an optical system and a deflector, as well as an acoustic transducer and an amplifier, a processing unit and a recorder connected in series to it, characterized in that it further comprises an optically matched electromagnetic source an energy scanner and an optical converter, as well as a software device and a video camera, while the electromagnetic energy source is n in the form of a laser, the optical system is in the form of a laser beam shaper with a hollow core, and an acoustic transducer with a uniform directivity characteristic located on the optical axis of the laser behind the scanner and deflector is used as an acoustic transducer, and the software device is connected to the optical transducer by its outputs scanner and deflector.  2. The sonar according to claim 1, characterized in that the software device is additionally connected to the synchro inputs of the recorder and video camera.  3. The sonar according to claim 1 or 2, characterized in that the laser beam shaper with a hollow core is equipped with a drive for its displacement relative to the laser axis, while the control input of the drive is connected to one of the outputs of the software device.