Apparatus for ultrasound detection

• US 5,042,303 A
• Filed: 04/16/1990
• Issued: 08/27/1991
• Est. Priority Date: 02/21/1986
• Status: Expired due to Fees

• Current Assignee: B.V. Optische Industrie "De Oude Delft"
• Original Assignee: B.V. Optische Industrie "De Oude Delft"
• Inventors: Geluk, Ronald J., de la Fonteijne, Marcel R.
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US07/509,486
• Time in Patent Office: 498 Days
• Field of Search: 73/602, 73/615, 73/620, 73/629, 73/631, 128/660.07
• US Class Current: 73/602
• CPC Class Codes: G01H 15/00 Measuring mechanical or acoustic impedance
• CPC Class Codes: G01H 3/12 by electric means G01H3/14 takes precedence
• CPC Class Codes: G01S 7/52017 particularly adapted to short-range imaging G01S7/53 takes precedence
• CPC Class Codes: G01S 7/5202 for pulse systems
• CPC Class Codes: G01S 7/52025 for pulse systems G01S7/52034 takes precedence

Abstract

An ultrasound transducer generates a received signal in response to a reflected ultrasound signal. Polarity and phase information of the reflected ultrasound signal can be obtained by time-selectively amplifying the received signal with a specific gain function. The specific gain function is derived from the received signal itself and is independent of the polarity of the received signal.

Claims

1. An apparatus for ultrasound detection comprising an ultrasound transducer, means for generating an energizing signal for said transducer, means for detecting a signal received by said ultrasound transducer after reflection, said detection means comprising means for determining polarity of said received signal, said polarity determining means comprising means for deriving an auxiliary signal from said received signal, said means for deriving an auxiliary signal comprising rectifying means, said auxiliary signal having the same or twice the base frequency as said received signal, having a shape independent of polarity of said received signal and having an amplitude which at any point of time is a time-independent predetermined function of the amplitude of the received signal at one or more corresponding points of time and said polarity determining means further comprising means for performing a multiplicative operation with said auxiliary signal on said received signal.

2. An apparatus according to claim 1 wherein said energizing signal generating means produces a signal shaped to the response characteristic of said ultrasound transducer to produce a signal received after reflection of a predetermined shape necessary to obtain said polarity information.

3. An apparatus according to claim 2 wherein G(f) is frequency responsive characteristic of said ultrasound transducer and H(f) is said frequency characteristic of said predetermined shape of a signal received after reflection, a frequency characteristic F(f) of said transducer being defined by:

space="preserve" listing-type="equation">F(f)=H(f)/G(f).

4. The apparatus according to claim 1 wherein said means for performing a multiplicative operation comprises means for multiplying said received signal with said auxiliary signal.

5. An apparatus according to claim 1 wherein said means for performing a multiplicative operation comprises means for dividing said received signal by said auxiliary signal.

6. An apparatus according to claim 1 including at least two parallel signal paths, means in a first one of said signal paths for operating upon the signal in said first path, combining means for combining the signals exiting from said first and second paths, the operating and combining means being operative such that after combining the signals from the first and second signal paths into said auxiliary signal said auxiliary signal is of substantially zero amplitude during part of its duration.

7. The apparatus according to claim 6 wherein said means operating on said signal in said first path comprises delaying means for delaying said signal in said first path by a predetermined number of half cycles and said combining means being operatively connected to add said delayed signal to or subtract said delayed signal from said signal in said second path.

8. The apparatus according to claim 7 wherein said means for deriving said auxiliary signal from said received signal further includes means for forming a modulus of a signal resulting after addition or subtraction.

9. The apparatus according to claim 8 and further including means for dividing said received signal by said modulus of said signal resulting after subtraction, and time delay means for delaying said received signal by a predetermined period of time prior to division.

10. The apparatus according to claim 8 and further including means for delaying said modulus of said signal resulting after addition by half a cycle, means for subtracting said delayed signal from said modulus of said signal resulting after addition, means for multiplying said signal resulting after subtraction by said received signal, and time delay means for delaying said received signal by a predetermined period of time prior to multiplication.

11. The apparatus according to claim 1 wherein said detection means comprises means for determining a modulus of said received signal and means for forming a product of said received signal and said modulus of said received signal.

12. The apparatus according to claim 11 and further including means for integrating said product of said received signal and said modulus of said received signal.

13. The apparatus according to claim 11 and further including a filter for filtering said product of said received signal and said modulus of said received signal to form a filtered output signal and means generating as an output signal the root of said filtered output signal.

14. The apparatus according to claim 1 and further including first and second detection means having an input coupled to said ultrasound transducer and having an output for supplying a first and a second detection signal, respectively, and means for determining quotient of said first output signal and said second output signal to obtain information on a phase shift between said energizing signal and said received signal, said first detection means producing a first output signal of maximum value if said input thereto is an anti-symmetric signal and said second output means producing a second output signal of maximum value if said input thereto is a symmetric signal.

15. The apparatus according to claim 14 wherein said first and second detection means include identical detection circuits and further including means coupling said ultrasound transducer and at least one of said inputs to said first or second detection circuits, said coupling means establishing a phase shift of essentially 90°

between said input to said first and second detection circuit, respectively.

16. The apparatus according to claim 15 wherein said phase shift establishing means includes a differentiator coupled between said ultrasound transducer and said input to said second detection circuit.

17. The apparatus according to claim 15 wherein said phase shift establishing means include a Hilbert transformer coupled between said ultrasound transducer and said input to said second detection circuit.

18. The apparatus according to claims 15, 16 or 17 wherein each detection circuit includes means for forming said auxiliary signal and comprises means for delaying said signal applied to said input to said detection circuit by a predetermined number of half cycles and further including, means for adding said delayed signal and said input signal, means for forming a modulus of said signal resulting after addition, means for delaying by half cycle said signal resulting after addition, and means for subtracting said delayed signal from said modulus of said signal resulting after addition to form said auxiliary signal;

and wherein each of said detection means includes means for delaying said input signal by a predetermined period of time and means for multiplying said delayed input signal and said auxiliary signal to form a first and a second detection signal, respectively.

19. A method for ultrasound detection in which an ultrasound transducer is energized to transmit an ultrasound signal and a reflected ultrasound signal is received by said ultrasound transducer including the step of deriving an auxiliary signal from said received signal, said auxiliary signal having a same or twice the base frequency as said received signal, having a shape independent of polarity of said received signal and having an amplitude which at any point of time is a time independent predetermined function of said amplitude of said received signal at a corresponding point of time and performing a multiplicative operation with said auxiliary signal on said received signal.