JPS6161072B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sonar video signal processing device.

Conventionally, the threshold control method in the video signal processing device of a sonar device compares the magnitude of the video signal with respect to the threshold level, and if the video signal is larger, it is output, and if it is smaller, it is not output. , the threshold level is fixed or manually set. This relationship will be explained in more detail with reference to FIGS. 1 to 3.

Figure 1 shows the flow of video signals from the detection circuit of the sonar device to the CRT. Signals 101(1) to 101 input to the detection circuit 1
(n) is an n-channel sonar reception signal, which is also detected by the n-channel detection circuit and sent to the scanning circuit 2. The scanning circuit 2 uses the n-channel detection output signals 102(1) to 102(n) in FIG. 2 as input signals, and samples and scans the n-channel detection output signals at regular intervals in synchronization with the deflection signal of the sonar device. The scanning output signal (Fig. 3a) is sent to the video amplification circuit 3.
Output to.

The video amplifier circuit 3 compares the scanning output signal with the threshold level TH set by the variable resistor 5, outputs only the scanning output signal with a level higher than the level TH, and blocks it when it is lower than the level TH. The threshold control output signal b in FIG. 3 is output to the CRT 4. CRT
4 modulates the brightness of an electron beam deflected by a deflection signal using a threshold control output signal 301 to display a sonar video on a CRT.

As mentioned above, for the scanning output signal 201, the level
Performing threshold control on the TH is equivalent to performing threshold control on the n-channel detection output signal at the level shown by the broken line in FIG. As can be seen from Figure 2, with this kind of threshold control, the threshold is insufficiently applied during the period when the reverberation level is high immediately after the sonar reception signal is transmitted, and the reverberation level is low during most of the CRT's video dynamic range. Even if there is a true echo signal, it may become saturated and cannot be detected by the operator. On the other hand, for signals received from a long distance, the threshold level is too high, and even if true echo sounds arrive, they are not displayed below the threshold level.

The present invention sets the threshold level to the reverberation level.
The present invention provides a sonar video signal processing device that automatically changes the noise level to solve the above drawbacks.

The present invention stores the detection output signal in a storage circuit, detects its peak value from the stored signal, and calculates TH by a constant _K1 that determines a preset automatic threshold level for the detected peak value Vmax. = Vmax/K With ₁ as the threshold level, detect the time (echo width) Tn in which the detected output signal including Vmax is greater than TH, and obtain the minimum echo width Tmin preset from the sonar device's transmission pulse width and target length. And from the maximum echo width Tmax, it is determined whether the echo width Tn is within the range of Tmin≦Tn≦Tmax. If it is within the range, the signal between Tn is left, and if the echo width is outside the range, it is a reverberation or noise. The threshold level is automatically determined from the momentary peak value of the detection output signal by erasing the stored detection output signal and sequentially outputting it to the scanning circuit. .

Embodiments of the present invention will be described below with reference to FIGS. 4 to 7.

In FIG. 4, the same reference numerals as in FIG. 1 indicate the same members, and detailed explanation thereof will be omitted. In FIG. 4, the detection output signals 102(1) to 102(n) of the n-channel detection circuit 1 are automatically threshold-controlled by the n-channel threshold control circuit 6 as described below, and the output signals 501(1) to 501 are
(n) is sent to the scanning circuit 2. Next, the details of the threshold control circuit will be explained in the fifth section.
This will be explained with reference to the figures.

In FIG. 5, 51 is a storage circuit that temporarily stores samples of the detection output signal 102(n) that change every moment at a constant sampling period. New data is stored for each sample, and the oldest data is stored in the scanning circuit. It operates to send out. Also, the data length temporarily stored in the storage circuit is the transmission pulse width +
Try to memorize more than the target length. The peak detection circuit 52 detects the peak value from the stored detection output signal, an example of which is shown in FIG.

In FIG. 6, a indicates an example of the detection output signal stored in the storage circuit, and the peak detection circuit 52
detects its peak values Vmax ₁ to Vmax ₉ . The peak value 503 is sent to the threshold level setting circuit 53, which determines a threshold level THn 504 for each peak value, and sends it to the echo width detection circuit 54.

Here, the threshold THn is THn=Vmaxn/
Determined by K ₁ . The constant K ₁ is a value of 1 or more, and the tendency is that as K ₁ increases, the threshold level decreases, and the detection accuracy of the target echo increases, but the detectable S/N also increases. Generally K ₁
= around 2, and it is also possible to set the value of _K1 externally using a regulator or the like. Figure 6a
The dashed line is for peak detected Vmax ₁ to Vmax ₉ .
TH ₁ to _{TH 9} determined as K ₁ =2 are shown. The echo width detection circuit 54 sets the detection output signal to a threshold level THn for each peak value Vmaxn.
A time Tn 505 at which the time is equal to or greater is detected and sent to the echo width determination circuit 55. In Figure 6b, T ₁ to _{T 9}
indicates the detected echo width for each of Vmax ₁ to Vmax ₉ .

Here, the width of the echo (target echo) received by the sonar device is related to the length of the target (submarine, mine, etc.). In FIG. 7a, when a sound wave S (transmitted pulse Tp) arrives at the target and is reflected, the reflection first starts from part A and continues to be reflected until the sound wave passes past B. This distance is l×
sinθ, and the echo sound duration Te is Fig. 7b
As shown in , Te=Tt+Tp(l・sinθ/C+Tp)(C
: speed of sound). Therefore, if various postures of the target are taken into account, it is expected that the echo sound duration Te will have a minimum value of the transmission pulse width Tp and a maximum value of the transmission pulse width Tp+target length l/c. Generally, this echo sound becomes slightly shorter as a result of various signal processing within the sonar device, and the minimum value Tmin of the echo sound duration Te is Tmin.
= Tp/K ₂ (K ₂ 1) The maximum value Tmax is Tmax = Tp
+l/c.

The echo width determination circuit 55 is the echo width detection circuit 54
Tmin for the detected echo width Tn505 detected at
≦Tn≦Tmax (1) is determined and a determination signal 507 is sent to the erase control circuit 56. The erasure control circuit 56 receives the judgment signal 507 of the echo width judgment circuit.
If the following detection echo width Tn does not satisfy equation (1), the erasure control signal 508 operates to erase the detection output signal stored in the storage circuit 51 for that section.

To explain this relationship in detail with reference to Fig. 6, when the transmission pulse width and target length (l/c) are as shown in Fig. 6d, K ₂ = 1.5 and the echo width detection signals T ₁ to _{T 9} in Fig. 6b are obtained. On the other hand, the echo width determination circuit 55 performs determination using equation (1). The results show that T ₃ , T ₆ and T ₇ are within the range of equation (1), and for T ₁ T ₂ T ₄ T ₅ T ₉ , T ₈ is below Tmin.
Tmax or higher. Therefore, the erase control circuit 5
6 is T ₃ T 6 and T 3 T ₆ from among the memory signals of the memory circuit 51
It operates to leave only the detection output signal of the _T7 interval and erase the others, and as a result, the detection output signal as shown in FIG. 6c remains in the storage circuit and is sequentially sent to the scanning circuit 2.

In this way, this device sets a threshold level based on the peak value of the detected output signal, and determines whether the detected output signal is appropriate as the target reverberation sound at that threshold level. It operates so that only the output is output.

As explained above, according to the present invention, it is possible to perform threshold control that follows the reverberation level noise level, compared to the conventional method that performs threshold control at a fixed threshold level. This has the advantage that a uniform screen can be obtained from areas with high noise levels to areas where navigation noise occurs.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional device, FIG. 2 is a diagram showing the waveform of a detection output signal, FIG. 3 is a diagram showing a scanning output signal and a threshold control output signal, and FIG. 4 is an embodiment of the present invention. A block diagram showing
FIG. 5 is a detailed block diagram of FIG. 4, FIG. 6 is a diagram illustrating the threshold control method according to the present invention, and FIG. 7 is an explanatory diagram illustrating the target echo width. 1...Detection circuit, 2...Scanning circuit, 3...Video signal amplification circuit, 4...CRT, 5...Variable resistor, 6...Threshold control circuit, 5
1... Memory circuit, 52... Peak detection circuit, 53
...Threshold level setting circuit, 54...Echo width detection circuit, 55...Echo width judgment circuit, 5
6... Erasing control circuit.

Claims (1)

[Claims] 1. A storage circuit that detects the sonar reception signal and temporarily stores this detection output signal, a peak detection circuit that detects the peak value from the stored signal, and determines the threshold level of the video signal from the detected peak value. a threshold level setting circuit for
an echo width detection circuit that compares the threshold level with the stored signal to detect an echo width Tn, and a minimum echo width preset from the transmission pulse width and target length of the sonar device.
The echo width from Tmin and maximum echo width Tmax
By having an echo width determination circuit that determines whether Tn is within Tmin≦Tn≦Tmax, and an erasure control circuit that erases the memory signal of the memory circuit using a determination signal output from this echo width discrimination circuit, automatic 1. A sonar video signal processing device characterized by determining a threshold level of a detection output signal.