A process for selective graphic representation and/or evaluation of the Doppler spectrum of objects limitedly resistant to sonic intensity, for example biological organs and tissues, by an ultrasonic process wherein a material is introduced in the examination area to be acoustically irradiated, nonlinear oscillations are produced in the examination area by irradiated ultrasonic waves and the signal is evaluated by an ultrasonic converter. Also, a circuit for carrying out the above process is disclosed.

Ultrasonic processes and circuits for performing them

Sonic excitation is used to locate, without contact, an object or defect beneath a surface. Defects may include, for example, damage and flaws in load bearing concrete structures wrapped in plastic, fiberglass or composite sheathing, while buried objects amenable to detection include landmines or above-ground mines.

Acoustic detection of hidden objects and material discontinuities

Acoustic imaging apparatus wherein a beam of high frequency acoustic energy is directed to the object to be imaged to create variations in the transmitted acoustic energy which variations are then detected by a plurality of small particles suspended in the beam path for motion in response to radiation pressure produced by the incident acoustic energy, thus providing a visible image with high contrast sensitivity and excellent image resolution.

Acoustic imaging apparatus

The invention provides a three-wave coupling interaction principle-based nonlinear coefficient measurement method for a non-uniform mixed medium. By emission of three columns of sound waves meeting a coupling work interaction condition to the non-uniform mixed medium and a water medium step by step, comparison of an observation distance at which obvious sound pressure level change occurs to sound waves in mixed medium and an observation distance at which obvious sound pressure level change occurs to sound waves in water medium, and correction the error between a model and a test result, a nonlinear coefficient measurement result of the mixed medium can be indirectly obtained. The method does not depend on the measurement precision of parameters such as a sound wave phase and sound pressure, and can effectively improve the experimental measurement precision of a nonlinear system; the test method is applicable to an experimental water tank condition; furthermore, test steps are simple, the test precision is high, and the method has relatively high application value.

Three-wave coupling interaction principle-based nonlinear coefficient measurement method for non-uniform mixed medium

An underwater display unit for divers consists of a two-component housing with a converter device (2) and an operating and display device (1). Both housing components can also be used separately from one another and are then to be connected to one another via a cable. The converter device (1) comprises transmission and reception converters (4, 5) for scanning an angular area in front of the display units, while the operating and display device (1) has an electroluminescent screen (9), on which the field of vision is reproduced in profiled representation and which also contains various displays for direction, distance, diving depth, battery level, frequency and the like.

Underwater display unit

An object situated in an acoustic medium, such as water or soil, characterized by relatively high acoustic absorption is optically imaged by a novel acousto-optical imaging technique. Relatively low frequency acoustic waves which are subject to relatively low attenuation by the ambient medium are transmitted through the medium to the object and emanate from the object as distorted acoustic waves containing information defining an image of the object. These distorted acoustic waves are received by an acousto-optical coupling medium which is excited by relatively high frequency and large amplitude acoustic waves. The distorted low frequency acoustic waves and high frequency waves undergo non-linear interaction to produce in the coupling medium resultant acoustic wave sets having frequencies equal to the sum and difference, respectively, of the low and high frequencies and each containing essentially the same image information as the distorted waves. A monochromatic light beam is projected through the coupling medium to impinge the wave fronts of one resultant wave set, preferably the sim wave set, at an oblique angle which causes Bragg diffraction of the light waves by the acoustic waves, such that the light waves emerging from the coupling medium form an optical image of the object.

Low frequency parametric acousto-optical imaging method and apparatus

An underwater acousto-optical imaging system for receiving water-borne acoustic waves representing an image of an object in the water and converting the image information to a corresponding optical image of the object. The acoustic waves are focused by an acoustic lens into a Bragg coupling medium wherein a monochromatic light beam is Bragg diffracted by the acoustic waves to produce a modulated light side band defining the optical image. A television camera converts this optical image to electrical signals for viewing of the image at a remote video monitoring station. The imaging system may be driven in a scanning motion for operation in a search made and may include an acoustic source for generating acoustic probing waves which reflect from objects in the water back to and are converted to optical images by the imaging system.

J Jacoby

Papers

Low frequency parametric acousto-optical imaging method and apparatus

Acousto-optical underwater imaging system