Pulse compression apparatus for ultrasonic image processing

Abstract

A pulse compression apparatus comprises a quadrature detector for converting an echo signal obtained by an ultrasonic transducer into a complex signal, a reference wave oscillator for producing a reference wave signal, and a correlation circuit for deriving a correlation between the complex signal and the reference wave signal to compress the echo signal.

What is claimed is: 
     
       1. A pulse compression apparatus for ultrasonic image processing, comprising: quadrature detection means for converting an echo signal obtained from an ultrasonic transducer means into a complex signal;   reference output means for producing a reference wave signal; and   correlation means for deriving a correlation between said complex signal and said reference wave signal to compress said echo signal.   
     
     
       2. A pulse compression apparatus according to claim 1, wherein said quadrature detection means comprises: continuous wave generating means for generating first and second continuous wave signals with a phase difference of 90 degrees therebetween; and   multiplier means for multiplying said first and second continuous wave signals generated by said generating means by said echo signal, to produce first and second output signals.   
     
     
       3. A pulse compression apparatus according to claim 2, wherein: said echo signal has a frequency band having a predetermined center frequency; and   said continuous wave generating means generates said first and second continuous wave signals such that each has a center frequency equal to said center frequency of said frequency band of said echo signal.   
     
     
       4. A pulse compression apparatus according to claim 2, wherein said quadrature detection means further includes low-pass filter means for filtering said first and second output signals output from said multiplier means. 
     
     
       5. A pulse compression apparatus according to claim 2, wherein said correlation means comprises: means for receiving said complex signal from said quadrature detection means, and delay means for delaying said complex signal by different delay times for producing a plurality of delayed output signals; and   means for convolution-integrating said delayed output signals and said reference wave signal.   
     
     
       6. A pulse compression apparatus according to claim 5, wherein said quadrature detection means further includes low-pass filter means for filtering said first and second output signals output from said multiplier means, said low-pass filter means having a given pass band; and said delay means includes a maximum delay time means for permitting a band twice as wide as said pass band of said low-pass filter means to chirp.   
     
     
       7. A pulse compression apparatus according to claim 1, wherein said correlation means comprises: means for receiving said complex signal from said quadrature detection means, and delay means for delaying said complex signal by different delay times for producing a plurality of delayed output signals; and   means for convolution-integrating said delayed output signals and said reference wave signal.   
     
     
       8. A pulse compression apparatus according to claim 7, wherein said convolution-integrating means comprises: arithmetic operation means for multiplying said delayed output signals produced by said delay means by said reference wave signal for producing first and second real components and first and second imaginary components;   means for subtracting said first and second real components produced by said arithmetic operation means, from each other; and   means for adding together said first and second imaginary components.   
     
     
       9. A pulse compression apparatus according to claim 8, wherein said arithmetic operation means further comprises: a common base type amplifier means for receiving said delayed output signals and said reference wave signal; and   a differential amplifier having an input coupled to an output of said common base type amplifier means.   
     
     
       10. A pulse compression apparatus according to claim 1, wherein said ultrasonic transducer means is disposed within an endoscope. 
     
     
       11. A pulse compression apparatus according to claim 1, wherein said reference output means includes means for generating reference wave signals which vary as a function of variations of said echo signal. 
     
     
       12. A pulse compression apparatus according to claim 1, wherein said correlation complex signals, and which further comprises: quadrature modulation means for quadrature-modulating said compressed complex signals output from said correlation means and for producing an output signal having carrier components;   doppler detection means for detecting doppler signal components from said compressed complex signals;   means for processing said output signal output from said quadrature modulation means for producing a video signal; and   means for converting said doppler signal components and said video signal into a television signal. .Iadd.   
     
     
       13.  A pulse compression apparatus according to claim 2, wherein said continuous wave generating means includes a voltage controlled oscillator for variably controlling the frequencies of said first and second continuous wave signals. .Iaddend. .Iadd.14. A pulse compression apparatus according to claim 2, wherein said continuous wave generating means includes means for generating said first and second continuous wave signals whose frequencies are varied in accordance with the received echo signal. .Iaddend. .Iadd.15. A pulse compression apparatus according to claim 2, wherein said quadrature detection means includes an oscillator means for generating a third continuous wave signal different from said first and second continuous wave signals, additional multiplier means for multiplying said third continuous wave signal by said received echo signal and for outputting an output signal including a predetermined signal corresponding to a predetermined frequency band, and filter means for extracting said predetermined signal from said output signal outputted from said additional multiplier means and for providing the extracted signal to said continuous wave generating means. .Iaddend. .Iadd.16. A pulse compression apparatus according to claim 1, which further includes at least one of first and second memory means provided in an endoscope, said first memory means storing a first signal defining a transmission signal and a second signal defining frequencies of continuous wave signals output from said quadrature detection means, and said second memory means storing a third signal defining a frequency of said reference signal in said correlation means. .Iaddend. .Iadd.17. A pulse compression apparatus according to claim 1, which further includes memory means for storing at least one of a transmission wave data corresponding to said ultrasonic transducer means, a frequency data relative to a continuous wave signal in said quadrature detection means, and a frequency data relative to the reference wave signal in said correlation means. .Iaddend. .Iadd.18. A pulse compression apparatus according to claim 17, wherein said memory means comprises a read only memory provided in a connector of an endoscope. .Iaddend. .Iadd.19. A pulse compression apparatus according to claim 1, wherein said correlation means outputs compressed complex signals, and which further comprises AM (amplitude modulation) detection means for AM detecting the compressed complex signals and outputting an output signal, Doppler detection means for detecting a Doppler signal from the compressed complex signal, from said AM detection means and outputting a video signal, and means for converting said Doppler signal and said 
     
     
        video signal into a television signal. .Iaddend. .Iadd.20.  A pulse compression apparatus according to claim 19, wherein said AM detection means comprises quadrature modulation means for quadrature-modulating the compressed complex signals and adding the quadrature-modulated compressed complex signals to produce an output signal having carrier components, and detection means for detecting the output signal from said quadrature modulation means. .Iaddend. .Iadd.21. A pulse compression apparatus according to claim 19, wherein said AM detection means comprises means for squaring a real component and an imaginary component contained in the compressed complex signals, means for adding the squared real component and imaginary component and means for obtaining a square-root of an output from said adding means. .Iaddend. .Iadd.22. A pulse compression apparatus according to claim 2, further comprising memory means provided in an endoscope for storing a first signal defining a transmission signal generated by said ultrasonic transducer means, a second signal defining frequencies of said first and second continuous wave signals output from said quadrature detection means, and a third signal defining a frequency of said reference signal provided by said reference output means. .Iaddend.