JP5210544B2 - Detecting device - Google Patents

Description

  The present invention relates to a detection device that transmits ultrasonic pulses in water and displays them with different display colors according to the signal intensity of ultrasonic echoes reflected by underwater objects.

  2. Description of the Related Art Conventionally, a detection device that emits an ultrasonic pulse into water and confirms the underwater object from an ultrasonic echo reflected by the underwater object is known. In this type of detection device, the display color is changed according to the signal intensity of ultrasonic echoes to display underwater objects (see Patent Document 1).

  FIG. 6 is a block diagram of a detection device 60 according to this type of general detection device. In the detection device 60, the transmission control unit 14 outputs a pulse signal to the pulse transmission unit 16 at a predetermined transmission interval in order to transmit an ultrasonic pulse from the ultrasonic transducer 12 to the water. The pulse transmitter 16 creates a gate pulse signal based on the pulse signal and transmits the gate pulse signal to the ultrasonic transmitter / receiver 12, and the ultrasonic transmitter / receiver 12 has a time corresponding to the pulse width of the gate pulse signal. Fire an ultrasonic pulse into the water. The ultrasonic transmitter / receiver 12 receives an ultrasonic echo in which an ultrasonic pulse emitted into water is reflected by an underwater object, and outputs an echo signal converted into an electric signal to the analog receiver 18.

  The analog receiving unit 18 amplifies the signal intensity that can be displayed on the display unit 44, extracts a frequency component to be displayed by a band filter (not shown), converts the frequency component into a digital signal by the A / D conversion unit 20, Input to the detector 31. In the first detection unit 31, the echo signal that has passed through the first filter 21, which is a bandpass filter of the bandwidth Bw 1, is envelope-detected by the envelope detection unit 24 and then output to the display control unit 34. In the display control unit 34, the echo signal from the first detection unit 31 received between the reception of the pulse signal output from the transmission control unit 14 and the reception of the next pulse signal is set as a display control target. The signal intensity of the echo signal is detected and displayed on the display unit 44 in a display color corresponding to the signal intensity. Usually, an ultrasonic echo includes white noise in addition to a target signal indicating underwater, and it is important to remove the white noise.

  It is known that ultrasonic echoes from underwater appear at predetermined positions in synchronization with the transmission period of ultrasonic pulses, while white noise appears irregularly. By utilizing this property, only ultrasonic echoes that appear continuously at the same position are displayed, and the ultrasonic echoes that appear irregularly are considered to be white noise and are removed (see Patent Document 2). ).

JP 2002-116249 A Japanese Patent Laid-Open No. 4-5594

  However, the above white noise removal method is effective when the signal strength of the ultrasonic echo from the underwater is larger than the signal strength of the white noise, but the signal strength of the ultrasonic echo is a signal of white noise. When the intensity is equal to or smaller than the intensity, it is difficult to remove only the white noise because the ultrasonic echo from the underwater and the white noise cannot be distinguished.

  The present invention has been made in consideration of the above problems, and distinguishes between white noise and underwater objects even when the signal intensity of the ultrasonic echo is equal to or smaller than the signal intensity of the white noise. It is an object of the present invention to provide a detection device that can do this.

The detection apparatus according to the present invention includes first detection means for emitting an ultrasonic pulse into water and detecting an envelope of an ultrasonic echo reflected by the underwater through a first filter, from the first detection means. Second detection means for detecting an envelope through a second filter having a narrower bandwidth than the first filter, the detection device displaying different display colors according to the signal intensity of the output signal Reliability calculation means for calculating the reliability of the echo signal based on the signal strength of the output signal from the first detection means and the signal strength of the output signal from the second detection means; and And a shade display control means for changing the shade of the display color based on the reliability .

According to the present invention, the reliability of the echo signal is calculated based on the signal strength of the output signal from the first detection means and the signal strength of the output signal from the second detection means, and the reliability of the echo signal is calculated. By changing the shade of the display color based on the degree, even if the target signal is equal to or smaller than the signal intensity of the white noise, the target underwater object and the white noise can be visually distinguished. It becomes possible.

According to another aspect of the present invention, there is provided a detection device including first detection means for emitting an ultrasonic pulse into water and detecting an ultrasonic echo reflected by the underwater object through an first envelope through an envelope. A detection device that displays different display colors according to the signal intensity of an output signal from a detection means, and detects an envelope of the ultrasonic echo through a second filter having a narrower bandwidth than the first filter. Second detection means, third detection means for directly detecting the ultrasonic echo in an envelope, signal intensity of an output signal from the second detection means, and signal intensity of an output signal from the third detection means A reliability calculation means for calculating the reliability of the echo signal based on the image quality; and a shade display control means for changing the density of the display color based on the reliability of the echo signal .

According to the present invention, the reliability of the echo signal is calculated based on the signal strength of the output signal from the second detection means and the signal strength of the output signal from the third detection means, and the reliability of the echo signal is calculated. By changing the shade of the display color based on the degree, even if the target signal is equal to or smaller than the signal intensity of the white noise, the target underwater object and the white noise can be visually distinguished. It becomes possible.

  Further, a ratio between the bandwidth of the first filter and the bandwidth of the second filter is determined based on each attenuation factor of the first filter and the second filter.

According to the present invention, the signal strength of the output signal from the first detection means, the signal strength of the output signal from the second detection means, or the signal strength of the output signal from the second detection means, Based on the signal strength of the output signal from the third detection means, the reliability of the echo signal is calculated, and the shade of the display color is changed based on the reliability of the echo signal, so that the target signal is white noise. Even if the signal intensity is equal to or smaller than the signal intensity, it is possible to visually distinguish the target underwater product from the white noise.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a detection device 10 according to the first embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the component same as the detection apparatus 60 shown in FIG.

  The detection device 10 has a second detection unit 32 added to the detection device 60, and a gradation display control unit 40 is added instead of the display control unit 34.

  The second detection unit 32 includes a second filter 22 that is a bandpass filter having a bandwidth Bw2, and an envelope detection unit 24b that performs envelope detection of an echo signal output from the A / D conversion unit 20 through the second filter 22. Is provided. The bandwidth Bw2 of the second filter 22 is set to be narrower than the bandwidth Bw1 of the first filter 21. The second filter 22 is not particularly limited as long as it is a band filter, but is preferably an active band filter.

  The grayscale display control unit 40 includes a delay circuit 46 for synchronizing the output signal from the first detection unit 31 and the output signal from the second detection unit 32, the output signal from the first detection unit 31, and the second signal. The reliability calculation unit 48 that calculates the reliability of the echo signal based on the output signal from the detection unit 32 and the signal intensity of the output signal output from the first detection unit 31 are displayed in different colors according to the reliability. And a display control unit 42 that generates a display signal for display and outputs it to the display unit 44.

  The detection device 10 according to the embodiment of the present invention is basically configured as described above, and its operation will be described.

  In the detection device 10, the transmission controller 14 outputs a pulse signal to the pulse transmitter 16 in order to transmit an ultrasonic pulse from the ultrasonic transducer 12 to the water. The pulse transmitter 16 creates a gate pulse signal based on the pulse signal and transmits the gate pulse signal to the ultrasonic transmitter / receiver 12, and the ultrasonic transmitter / receiver 12 has a time corresponding to the pulse width of the gate pulse signal. Fire an ultrasonic pulse into the water.

  The ultrasonic transmitter / receiver 12 receives an ultrasonic echo in which an ultrasonic pulse emitted into water is reflected by an underwater object, and outputs an echo signal converted into an electric signal to the analog receiver 18.

  The analog receiving unit 18 amplifies the signal intensity that can be displayed on the display unit 44, extracts a frequency component to be displayed by a band filter (not shown), converts the frequency component into a digital signal by the A / D conversion unit 20, The signals are input to the first filter 21 of the detection unit 31 and the second filter 22 of the second detection unit 32.

  A frequency component of the echo signal that has passed through the first filter 21 is extracted according to the bandwidth Bw1, envelope detected by the envelope detector 24a, and displayed via the delay circuit 46 in the grayscale display controller 40 via the display control unit 42. And output to the reliability calculation unit 48. The echo signal that has passed through the second filter 22 has a frequency component extracted in accordance with the bandwidth Bw2, is envelope-detected by the envelope detector 24b, and is output to the reliability calculator 48.

  The reliability calculation unit 48 calculates the reliability R based on the output signal F that is an echo signal output from the first detection unit 31 and the output signal S that is an echo signal output from the second detection unit 32. Is done. The reliability R is obtained as a ratio between the output signal S and the output signal F, that is, R = S / F. The reliability R has a correlation with the content rate of the target signal, which is an echo signal indicating the underwater contained in the ultrasonic echo.

  The reliability R will be described with reference to FIGS. 2A to 2C. FIG. 2A is an explanatory diagram showing the signal strength with respect to the frequency component of the echo signal output from the A / D converter 20 before being input to the first detector 31 and the second detector 32, and FIG. FIG. 2C is an explanatory diagram showing the signal strength with respect to the frequency component of the output signal F output from the first detection unit 31, and FIG. 2C shows the signal strength with respect to the frequency component of the output signal S output from the second detection unit 32. It is explanatory drawing represented.

As shown in FIG. 2A, the echo signal output from the A / D converter 20 is composed of a target signal and white noise. The target signal corresponds to a raised portion near the center frequency f ₀ , and this raised region is _denoted as G. In general, white noise has a constant signal strength with respect to frequency, and the region of this constant signal strength is W.

The output signal F from the first detection unit 31, as shown in FIG. 2B, the first filter 21, f ₀ -Bw1 / 2 or less of the frequency band and f ₀ + Bw1 / 2 or more frequency bands are cut. Note that this cut area is A.

The output signal S from the second detection unit 32, as shown in Figure 2C, the second filter 22, f ₀ -Bw2 / 2 or less of the frequency band and f ₀ + Bw2 / 2 or more frequency bands are cut. Note that the cut f ₀ -Bw1 / 2 or f ₀ -Bw2 / 2 or less parts and f ₀ + Bw2 / 2 or f ₀ + Bw1 / 2 following regions as B.

From FIG. 2B, the region FD corresponding to the output signal F is expressed as the following equation (1).
FD = G + W-A (1)

From FIG. 2C, the region SD corresponding to the output signal S is expressed as the following equation (2).
SD = G + W−A−B (2)

The reliability R is the ratio between the output signal S and the output signal F. Since this ratio corresponds to the ratio between the region SD and the region FD, the reliability R can be expressed using equations (1) and (2). Is expressed as the following equation (3).
R = S / F = SD / FD = (G + W−A−B) / (G + W−A) (3)

Moreover, when the content rate of the target signal contained in the output signal F is set to P, it represents as following Formula (4).
P = G / (W−A) (4)

When the formula (4) is substituted into the formula (3) and rearranged, the reliability R is expressed as the following formula (5).
R = 1−β / (P + 1) (5)
Note that β = B / (W−A).

  As is clear from this equation, the reliability R approaches 1 as the content rate P increases, and the reliability R approaches 0 as the content rate P decreases, so the reliability R is included in the ultrasonic echo for the echo signal. It will be understood that this corresponds to the content of the target signal, which is an echo signal indicating the submerged object.

  Next, the relationship between the bandwidth Bw1 of the first filter 21 and the bandwidth Bw2 of the second filter 22 will be described.

When the input signals to the first detection unit 31 and the second detection unit 32 are composed of only white noise, the ratio between the output signal S from the second detection unit 32 and the output signal F from the first detection unit 31 Corresponds to the ratio of the bandwidth of the second filter 22 and the first filter 21, so the relationship of the following equation (6) is established. Further, since the relationship between the bandwidths of the first filter 21 and the second filter 22 is Bw2 <Bw1, the output signal S is smaller than the output signal F, so the relationship of the following equation (7) is established.
S / F = √ (Bw2 / Bw1) (6)
S / F <1 (7)

If the signal intensity of the target signal is Sig and the signal intensity of white noise is Nw, the output signal F output through the first filter 21 is the sum of Sig and Nw. Is done.
F = Sig + Nw (8)

The output signal S output through the second filter 22 is expressed by the following equation (9).
S = BLvl × Sig + Nw × √ (Bw2 / Bw1) (9)

  Here, in each attenuation factor when the target signal which is a pulse signal passes through the first filter 21 and the second filter 22, the ratio of the attenuation factor of the second filter 22 to the attenuation factor of the first filter 21 is BLvl. . The attenuation rates of the first filter 21 and the second filter 22 are determined by the filter configuration, the distribution constant, the pulse width of the target signal, and the like.

Here, BLvl has the relationship of the following equation (10) because the bandwidth Bw2 is smaller than the bandwidth Bw1.
0 <BLvl ≦ 1 (10)

When the tone signal passes with a gain of 0 (dB) within the pass band of the first filter 21 and the second filter 22, the following expression (11) needs to be satisfied.
BLvl = 1 (11)

Furthermore, since the reliability R obtained by substituting Equations (8) and (9) into Equation (3) needs to change according to the Sig of the signal strength of the target signal, the relationship of the following Equation (12) is satisfied. Become.
BLvl ≠ √ (Bw2 / Bw1) (12)

Therefore, the relationship of the following equation (13) is derived from the relationship of the equations (6) to (12).
BLvl> √ (Bw2 / Bw1) (13)

  Next, the reliability R calculated by the reliability calculation unit 48 is output to the display control unit 42. FIG. 3 is a diagram showing a color conversion table used when the display control unit 42 performs display control with different display colors according to the signal intensity of the echo signal. The color conversion table is arranged so that the display color to be displayed on the display unit 44 is determined according to the signal intensity, and the display color corresponds to the vertical direction of the table corresponding to the change from the low signal intensity to the high signal intensity. Has been. Further, in accordance with the reliability R, the display density changes in the horizontal direction of the table in order to change the display color from dark to light in response to the change from high to low reliability R. Is arranged.

  The display control unit 42 detects the signal intensity of the echo signal output from the first detection unit 31 via the delay circuit 46 to determine the display color, and according to the reliability R output from the reliability calculation unit 48. Thus, the display density of the display color is determined. For example, when the signal intensity is the lowest but the reliability is the highest, it is determined as C00 and is output as a display signal to the display unit 44 and displayed on the display unit 44 with the display color and display density determined by C00.

  4A and 4B are diagrams showing display examples of echo signals, FIG. 4A is a display example by a conventional detection device, and FIG. 4B is an explanatory diagram showing a display example by the detection device 10.

  As shown in FIG. 4A, when the signal intensity of the target signal and the white noise is the same in the conventional detection device, the underwater and white noise cannot be distinguished and displayed, and the underwater surrounded by a line in FIG. 4A. The part representing is buried in white noise and displayed.

  On the other hand, according to the detection device 10, as shown in FIG. 4B, even if the signal intensity of the target signal and the white noise is the same, the echo signal is displayed with shading depending on the reliability R. Thus, the display color of the underwater object is displayed darkly, and the display color of the white noise is displayed lightly, whereby the underwater object and the white noise can be distinguished.

  As described above, the detection device 10 according to this embodiment emits an ultrasonic pulse into the water, and detects the ultrasonic echo reflected by the underwater object through the first filter 21 as an envelope detector 31. And a second detector 32 for detecting an envelope through the second filter 22 whose bandwidth is narrower than that of the first filter 21.

  In the detection device 10, the gray level display control unit 40 calculates the reliability R as a ratio between the signal strength of the output signal from the first detection unit 31 and the signal strength of the output signal from the second detection unit 32, By changing the display density according to the reliability R and displaying it, the target underwater and white noise can be visually distinguished even when the signal intensity of the target signal and white noise is equal or smaller. It becomes possible.

  Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a block diagram of a detection apparatus 10A according to the second embodiment of the present invention. The detection device 10A according to the second embodiment has an envelope detection unit (third detection unit) to which the echo signal output from the A / D conversion unit 20 is input to the detection device 10 of the first embodiment. 24 c is added, and a light / dark display control unit 50 is provided instead of the light / dark display control unit 40.

  The grayscale display control unit 50 includes a display control unit 42, a delay circuit 46, a delay circuit 46a for synchronizing the output signal from the envelope detection unit 24c and the output signal from the second detection unit 32, and a delay. A reliability calculation unit 52 that calculates the reliability of the echo signal based on the output signal from the circuit 46 a and the output signal from the second detection unit 32 is provided.

  The operation of the detection device 10A is basically the same as that of the detection device 10. In the detection device 10A, the ultrasonic pulse emitted from the ultrasonic transducer 12 into the water is received by the ultrasonic echo reflected by the underwater object, and the echo signal converted into the electric signal is converted into the analog receiver 18 and the A / A. The signal is input to the first detection unit 31, the second detection unit 32, and the envelope detection unit 24c via the D conversion unit 20.

  The reliability calculation unit 48 of the detection device 10 calculates the reliability R based on the output signal F from the first detection unit 31 and the output signal S from the second detection unit 32, but the reliability of the detection device 10A. The degree calculation unit 52 is reliable based on the echo signal N output from the envelope detection unit 24c via the delay circuit 46a and the echo signal S output from the envelope detection unit 24b after passing through the second filter 22. The degree R ′ is calculated. That is, the reliability R ′ = S / N. Like the reliability R in the detection device 10, the reliability R ′ in the detection device 10 </ b> A corresponds to the content rate of the target signal that is an echo signal indicating the underwater contained in the ultrasonic echo with respect to the echo signal. It will be understood.

  The display control unit 42 determines the display color by detecting the signal intensity of the echo signal output from the first detection unit 31 via the delay circuit 46, and determines the reliability R ′ output from the reliability calculation unit 52. Accordingly, the display density of the display color is determined.

  As described above, the detection device 10 </ b> A according to this embodiment emits an ultrasonic pulse into the water, and detects the ultrasonic echo reflected by the underwater object through the first filter 21 and detects the envelope. A second detector 32 for detecting an envelope of the ultrasonic echo through a second filter 22 having a narrower bandwidth than the first filter 21, and an envelope detector 24c for directly detecting the ultrasonic echo. Prepare.

  In the detection apparatus 10A, the grayscale display control unit 50 calculates the reliability R ′ as a ratio between the signal strength of the output signal from the second detection unit 32 and the signal strength of the output signal from the envelope detection unit 24c, By changing the display density according to the reliability R ′ and displaying it, the target underwater and the white noise are visually distinguished even when the signal intensity of the target signal and the white noise is equal or smaller. It becomes possible.

  Note that the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted without departing from the gist of the present invention.

1 is a block diagram of a detection device according to a first embodiment of the present invention. FIG. 2A is an explanatory diagram showing the signal strength with respect to the frequency component of the echo signal before being input to the first detection unit and the second detection unit, and FIG. 2B shows the signal strength with respect to the frequency component of the output signal F. FIG. 2C is an explanatory diagram showing the signal strength with respect to the frequency component of the output signal S. It is a figure which shows a color conversion table. 4A and 4B are diagrams showing display examples of echo signals, FIG. 4A is a display example by a conventional detection device, and FIG. 4B is an explanatory diagram showing a display example by the detection device 10. It is a block diagram of the detection apparatus which concerns on 2nd Embodiment of this invention. It is a block diagram of the conventional detection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 10A, 60 ... Detection apparatus 12 ... Ultrasonic transducer 14 ... Transmission control part 16 ... Pulse transmission part 18 ... Analog reception part 20 ... A / D conversion part 21 ... 1st filter 22 ... 2nd filter 24, 24a 24c ... envelope detection unit 31 ... first detection unit 32 ... second detection unit 34, 42 ... display control unit 40 ... grayscale display control unit 44 ... display unit 46, 46a ... delay circuit 48, 52 ... reliability calculation unit 50 .. shade display control unit

Claims (3)

First detection means for emitting an ultrasonic pulse into water and detecting an ultrasonic echo reflected by the underwater through the first filter as an envelope is provided, and according to the signal intensity of the output signal from the first detection means. A detection device that displays different display colors,
A second detector for detecting an envelope of the ultrasonic echo through a second filter having a narrower bandwidth than the first filter;
Reliability calculation means for calculating the reliability of the echo signal based on the signal intensity of the output signal from the first detection means and the signal intensity of the output signal from the second detection means ;
A shade display control means for changing the shade of the display color based on the reliability of the echo signal ;
A detection device comprising: First detection means for emitting an ultrasonic pulse into water and detecting an ultrasonic echo reflected by the underwater through the first filter as an envelope is provided, and according to the signal intensity of the output signal from the first detection means. A detection device that displays different display colors,
A second detector for detecting an envelope of the ultrasonic echo through a second filter having a narrower bandwidth than the first filter;
A third detection means for directly detecting the ultrasonic echo with an envelope;
Reliability calculation means for calculating the reliability of the echo signal based on the signal intensity of the output signal from the second detection means and the signal intensity of the output signal from the third detection means ;
A shade display control means for changing the shade of the display color based on the reliability of the echo signal ;
A detection device comprising: The detection device according to claim 1 or 2,
The detection device according to claim 1, wherein a ratio between the bandwidth of the first filter and the bandwidth of the second filter is determined based on each attenuation factor of the first filter and the second filter.

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