Apparatus for receiving reflected ultrasonic waves in ultrasonography

In an ultrasonographic system comprising means for emitting ultrasonic waves into a test body, said test body or parts thereof reflecting said ultrasonic waves as echo signals, apparatus for receiving said reflected echo signals, and means for displaying said echo signals as B-scan echograms;

• the improvement comprising said apparatus comprising a filter for processing said echo signals in response to instantaneous levels of said echo signals;
• wherein said filter is capable of receiving said echo signal in a range of higher frequencies when the echo signal has a higher level, and in a range of lower frequencies when the echo signal has a lower level;
• and where said filter comprises an input terminal for receiving said echo signal, a detector for detecting said echo signal, an amplifier connected between said input terminal and said detector and having at least one circuit for varying frequency characteristics, at least one source of reference voltage, and a comparator or differential amplifier for receiving an output from said detector and a reference voltage from said source, wherein said echo signal is received while characteristics of said at least one circuit for varying frequency characteristics are changeable depending on an output from said comparator.

In an ultrasonic system comprising means for emitting ultrasonic waves into a test body, said test body or parts thereof reflecting said ultrasonic waves as echo signals, apparatus for receiving said reflected echo signals, and means for displaying said echo signals as B-scan echograms;

• the improvement comprising said apparatus comprising a filter for processing said echo signals in response to instantaneous levels of said echo signals;
• wherein said filter is capable of receiving said echo signals in a range of higher frequencies when the echo signal has a higher level, and in a range of lower frequencies when the echo signals has a lower level;
• and wherein said filter comprises a successive saturation type logarithmic amplifier circuit including a plurality of series connected logarithmic amplifiers and a plurality of limiters preceding said logarithmic amplifiers, respectively, for limiting the amplitude of input signals, a plurality of bandpass filters connected respectively to outputs of said logarithmic amplifiers and having mutually different characteristics, a plurality of detectors for detecting outputs from said bandpass filters, and an adder amplifier for adding and amplifying outputs from said detectors into a logarithmically compressed video signal.

In an ultrasonographic systems comprising means for emitting ultrasonic waves into a test body, said test body or parts thereof reflecting said ultrasonic waves as echo signals, apparatus for receiving said reflected echo signals, and means for displaying said echo signals as B-scan echograms;

• the improvement comprising said apparatus comprising a filter for processing said echo signals in response to instantaneous levels of said echo signals;
• wherein said filter is capable of receiving said echo signal in a range of higher frequencies when the echo signal has a higher level, and in a range of lower frequencies when the echo signal has a lower level;
• and wherein said filter comprises a successive saturation type logarithmic amplifier including a plurality of series connected logarithmic amplifiers, a plurality of filters preceding said logarithmic amplifiers, respectively, and having different frequency bands, and a plurality of limiters preceding said logarithmic amplifiers, respectively, for limiting the amplitudes of input signals, a plurality of detectors for detecting outputs from said logarithmic amplifiers, respectivey, and an adder and amplifier for adding and amplifying outputs from said detectors into a logarithmically compressed video signal.

In an ultrasonographic system comprising means for emitting ultrasonic waves into a test body, said test body or parts thereof reflecting said ultrasonic waves as echo signals, apparatus for receiving said reflected echo signals, and means for displaying said echo signals as B-scan echograms;

• the improvement comprising said apparatus comprising a filter for processing said echo signals in response to instantaneous levels of said echo signals;
• wherein said filter comprises a variable filter having a cutoff frequency which is variable depending on the level of the echo signal.

In an ultrasonographic system comprising means for emitting ultrasonic waves into a test body, said test body or parts thereof reflecting said ultrasonic waves as echo signals, apparatus for receiving said reflected echo signals, and means for displaying said echo signals as B-scan echograms;

• the improvement comprising said apparatus comprising a filter for processing said echo signals in response to instantaneous levels of said echo signals;
• wherein said filter comprises a variable low cut filter or band pass filter, for receiving said echo signal, a logarithmic amplifier for logarithmically amplifying said echo signal, and means for producing a voltage signal corresponding to a peak value of an output signal from said logarithmic amplifier, said variable low cut filter having a cutoff frequency controllable by the output voltage of said means for producing a voltage signal.