Apparatus to detect and/or locate an inhomogeneity in a medium comprises a transducer to transmit frequency-modulated ultrasonic energy through the medium and a transducer to receive reflected energy. The transducers are connected to a phase-locked loop which maintains a required relationship between the phase of the transmitted modulation and the phase of the received modulation by adjustment of the modulation frequency. The modulation frequency adjustment is kept within predetermined upper and lower frequency limits so that the loop can lock only on to received ultrasonic energy which has travelled a distance within a predetermined region in the medium. The energy may be scanned across the region to produce a profile of the inhomogeneity, such as tissue at a certain depth within a limb.
An ultrasonic wave signal having its frequency varied continuously is transmitted from an ultrasonic wave transmitter toward a moving body. The wave reflected from the moving body is received by an ultrasonic wave receiver, and the resulting signal is frequency-demodulated to obtain a signal representing a frequency variation. A signal representing the feature of the moving body is produced with use of a signal representing the frequency variation of the transmitted ultrasonic wave and the signal representing the frequency variation of the received ultrasonic wave.
An apparatus for performing ultrasonic flaw detection, wherein an ultrasonic transmitter transmits a pulse signal having a designated carrier frequency and a designated cycle count to an ultrasonic probe. An ultrasonic receiver receives the echo signal output from the ultrasonic probe. The peak frequency and the frequency bandwidth of the echo signal received by the ultrasonic receiving unit are detected by a signal analysis unit. A transmission control unit designates the carrier frequency and the cycle count of the pulse signal output from the ultrasonic transmission unit so that the detected peak frequency and the detected frequency bandwidth become a flaw detection condition peak frequency and a flaw detection condition frequency bandwidth, respectively.
A camera includes a transmitter (2), an imaging system (8) for an object (4) and a receiver (10). According to the invention, in order to adjust the output signal (V.sub.2) of the receiver (10), a feedback is provided from the receiver (10) to the transmitter (2). The receiver includes a comparator (22) to one of whose inputs the spectrum of the actual values is fed in each case as a rectified output signal (V.sub.2) of the receiver (10) and to whose other input are fed corresponding reference values, and which controls the spectrum of the transmitter voltage (V.sub.1) of the transmitter (2) according to the deviation. By means of this feedback it is ensured that the same center frequency is always obtained at the receiver (10). As a result, the ultrasonic image is independent of the attenuation of signal caused by the object (4) and, accordingly, always has the same resolution even for different objects.
A double reference pulse phase locked loop for measuring the phase shift between tone burst signals initially derived from the same periodic signal source (voltage controlled oscillator 16) and delayed by different amounts because of two different paths. A first path is from transducer 12 to surface 14 of sample 11 and back, and a second path is from transducer 12 to surface 15 and back. A first pulse phase locked loop including phase detector 26 and phase shifter 22 forces the tone burst signals delayed by the second path in phase quadrature with the periodic signal source. A second pulse phase locked loop including phase detector 21 forces the tone burst signals delayed by the first path into phase quadrature with the phase shifted periodic signal source.
A method and system determines the density of a liquid, such as aircraft fuel, by measuring the amplitude of the reflections of ultrasonic pulses from the faces of the walls of a reference material. A transducer is used to transmit an ultrasonic interrogation pulse through a liquid to the reference material. The density of the reference material is known, and its boundaries are well defined. The interrogation pulse is reflected from the faces of the reference material boundaries to provide first, second and third return pulses that can be used to determine the density of the liquid. The density determination is accomplished by determining characteristic impedances, reflection coefficients and transmission coefficients as a function of the returned pulse amplitudes.
