JPH0143916B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an echo detection device that transmits pulses such as ultrasonic pulses and radio wave pulses, and receives and displays reflected waves thereof.

[Conventional technology]

In fish finders, there are relatively small noises such as reflected waves from plankton and other underwater noise, while in radars there are relatively small noises such as wave noise and reflected waves from rain. Therefore, in either case, the state of the reflection point may not be detected well even by looking at the display on the display.

There are various other noise components, and as a means to remove these noise components, the reflected signal is sampled at predetermined intervals, and the sampling level obtained during past sampling and the sampling level obtained during current sampling are compared. Japanese Patent Application Laid-Open No. 145165/1984 discloses a means for converting a noise signal that appears unevenly in the outline of the signal amplitude into a smoothed signal and removing the noise by storing the signal while averaging it.

In addition, by setting multiple sections for both direction and distance, determining a different subtraction value for each section, and giving the corresponding subtraction to the received signal obtained for each section, it is possible to Japanese Patent Laid-Open No. 53-92689 discloses means for removing particularly large clutter that exists only in a range section.

Furthermore, the reverberation level obtained from the first preliminary transmission and a received signal corresponding only to other noise components are obtained and memorized, and the reverberation level memorized from the regular received signal obtained thereafter. A means for removing noise components including reverberation by means for removing other noise components is disclosed in Japanese Patent Application Laid-Open No. 18777/1983.

[Problem to be solved by the invention]

When the above-mentioned conventional means are used as a means for removing relatively small noise components that occur immediately after transmission, the former and middle of these means, that is, Tokukai Akira
54-145165, JP-A-53-92689, etc. have the disadvantage that the configuration is too complicated.

Also, the latter means, that is, JP-A-56-18777
With such means, the reflected signal obtained by preliminary transmission includes the reflected signal of the target detected target, so there is an inconvenience that the reflected signal of the detected target is removed at the same time as the noise component. be.

Furthermore, although the configuration of either means is complicated, there is a disadvantage that it is not possible to perform variable processing while observing the reflected signals obtained from time to time before and after processing.

For this reason, there is a problem in that it is desired to provide something that solves these disadvantages with a simple and inexpensive configuration.

[Means to solve the problem]

This invention uses so-called STC, which reduces the gain sufficiently at the time of transmission and increases the gain as time passes, to remove the reverberation component immediately after transmission of the reflected signal obtained by periodically transmitting pulse waves, and After converting the received signal into a digital signal by AD converting it, a series of reflected signals obtained in response to the pulse wave (hereinafter referred to as detection signals) are captured, and each detection signal is arranged on the display screen in chronological order. A digital signal obtained by storing the oldest detection signal in the main memory so as to be erased and repeatedly reading the main memory in accordance with the display control of the raster scanning display (hereinafter referred to as a storage read digital signal) By converting each detection signal into a color signal corresponding to each digital value and providing it to a raster scanning type display, the echo detection device can display each detection signal in color. , and subtracts a low-level digital value to remove small noise in the detection signal, and when the subtraction result is less than or equal to the 0-level digital value, the 0-level digital value is subtracted. In the subtraction circuit that outputs depending on the value,
subtractive color conversion means for obtaining the above color signal based on each digital value obtained by applying the above storage readout digital signal; a variable gate generating means for generating a variable gate that corresponds to the detection signal; a variable operation means for variably operating the end point of the variable gate to a point corresponding to the end point of the detection signal; The above problem can be solved by providing a subtraction operation means for operating the subtraction means.

〔Example〕

Examples will be described below with reference to the drawings.

In FIG. 1, a transmitter 12 is driven by a control signal from a transmitter/receiver controller 11, which excites a transducer 14 through a transmitter/receiver switch 13.
Ultrasonic pulses are emitted into the ocean. The reflected wave is received by the transducer 14, and the transducer 1
3 and is received by the receiver 15. This received signal is converted into, for example, a 4-bit digital signal by the AD converter 16, and the digital signal is supplied to a buffer memory 18, as will be explained later. A series of reflected signals corresponding to one radiation pulse stored in the buffer memory 18 is transferred to the main memory 19.

The main memory 19 is repeatedly read out under the control of a display controller 22 for a raster scanning display 21, and the read signals are converted by a color converter 23 into color signals corresponding to each digital value and then displayed on the display. 21. A series of reflected signals corresponding to one transmitted pulse, that is, one detection signal, is displayed as one display line on the display screen of the display 21. The color converter 23 is configured so that the strongest level of the reflected signal is displayed in red, the weakest level (no signal) is displayed in blue, etc., and the color is displayed in accordance with each level. And indicator 21
The detection signals are arranged in chronological order on the display screen, and each time one detection signal is obtained in the buffer memory 18, it is transferred to the main memory 19.
The display on the display 21 is shifted in a certain direction,
The oldest display is deleted. In this way, a display similar to the display using conventional recording paper can be obtained on the display screen of the display 21.

The above configuration is known as a so-called color display fish finder, and as shown in FIG. 2A, in response to the transmitted pulse 25, a reflected signal 26 is obtained from the fish school later than this, and then a seabed reflected signal 27 is obtained. . However, in reality, when an ultrasonic pulse is transmitted, a so-called reverberation signal 28 is obtained immediately after the transmitted pulse 29, as shown in FIG. 2B. Further, when background noise such as plankton in the water or underwater noise generated from a screw or a distant place is at a weak level, noise 29 as shown in FIG. 2C is obtained. For example, as shown in FIG. 3, scanning lines 32 are formed above and below on the display surface 31 of the display 21, and a display 3 corresponding to the transmitted signal 25 is formed at a certain height of each scanning line 32.
3 appears, and a display 34 corresponding to the fish reflection signal 26 and a display 35 corresponding to the seabed appear, respectively. Furthermore, a small display 36 corresponding to the noise 29 appears. If a large number of displays 36 due to this noise are distributed on the screen, it becomes difficult to read the display 34 for the school of fish.

From this point of view, conventionally a so-called STC method has been adopted in which the gain of the receiver 15 is sufficiently lowered immediately after transmission, and the gain is increased over time. Using this method, the reverberation signal shown in FIG. 2B can be removed from the display screen. However, the level of background noise and reflected noise 29 from plankton is low and close to the level of the reflected signal 26 from the fish school, so if the gain of the receiver 15 is lowered, there is a risk that the display of the fish reflected signal 26 will not be visible on the display screen 31. be. Since the level of the fish school reflection signal 26 and the level of the noise 29 are relatively close to each other, when their display colors become the same, the fish school display 34 and the noise display 3
Even if the display colors of the fish reflection signal 26 and the noise 29 are different, the noise display 36 is very conspicuous in the color display.In other words, the display, which is a characteristic of the color display, becomes easier to see. Therefore, this background noise display 36 becomes conspicuous and the fish school display 34 becomes less conspicuous, making it difficult to identify it in a single time.

The present invention takes measures to remove such background noise display 36, that is, small noise components generated immediately after transmission, based on the following concept.

That is, a variable gate signal generator generates a gate signal that rises in synchronization with the transmission pulse, and the period of this gate signal is subtracted by a predetermined value from the reflected digital signal by a subtracting means. The gate width of this gate signal can be changed manually, the maximum is such that the gate signal falls at the end of one detection signal, and the end point of this gate signal can be changed. . With this configuration, background noise is removed by the subtraction during the period of the gate signal, and these noises do not appear as an image on the display surface of the display. An easy-to-read display image can be obtained by adjusting the variable gate signal generator to generate a gate signal in an area where background noise is present while viewing the display image on the display.

By applying a configuration for obtaining the same effect to the readout output of the main memory 19, it is possible to compare past reflected signals with the original state while looking at the display screen of the display 21. It is constructed so that it can be adjusted while

The variable gate signal generator 38 is constituted by, for example, a monostable multivibrator, and each time a trigger pulse is input, the gate signal becomes high level for a period of time determined by the time constant of the monostable multivibrator (see Fig. 2D). ) occurs. By adjusting the knob 39, the time constant can be changed, that is, the gate width _T1 of the gate signal can be adjusted. The variable gate signal generator 38 is constituted by a counter, and when a trigger pulse is applied, it starts counting clocks and its output becomes high level, and when it counts a predetermined number, its output becomes low level, and the output reaches the predetermined value. The number may be adjusted using a knob 39.

The gate signal from the variable gate signal generator 38 is supplied to the subtracter 17, and while the gate signal is input, the subtracter 17 inputs a predetermined value, for example 1 (or 2), from each output digital signal in the main memory 19. The subtraction result is supplied to the color converter 23, and when the gate signal is not applied, the output of the main memory 19 is supplied as is to the color converter 23.

For example, as shown in FIG. 4, the subtracter 17 receives the output digital signal from the main memory 19 to one input side of the adder 43, and inputs a predetermined signal from the fixed register 44 to the other input side of the adder 43. When subtracting a number, for example 1, its two's complement is input. However, this fixed register 44 is given the output gate signal of the variable gate signal generator 38, and the contents of the fixed register 44 are output only while this gate signal is given, but otherwise. High impedance is output. Therefore, the output of the adder 43 is a value obtained by subtracting a predetermined number, for example, one, from the output of the main memory 19 while the gate signal is present, and the output of the main memory 19 is output as is during other times. Ru.

Furthermore, in this example, the high level is saturated. In other words, the main memory 19 outputs the input level as a 4-bit digital signal depending on one of the 16 levels, but the output of the subtracter 17 saturates the high level and outputs a digital signal indicating the 9 levels. . That is, the output of the main memory 19 is a digital signal indicating any level from 0 to 15, and the output from the adder 43
If the output is not subtracted, it indicates a level between 0 and 15, and when it is subtracted, it indicates a level between 0 and 14. However, as the output of the subtractor 17, all levels 8 to 15 are output as 8 levels,
The output of the subtracter 17 is made to indicate any level from 0 to 8. For example, the output of the adder 43 is input to the inhibit gate 45, and the most significant bit in the output of the adder 43 inhibits the inhibit gate 45.
This most significant bit controls the opening and closing of the gate 46, and the gate 46 stores a fixed level from the register 47, a binary number "1000" indicating the 8th level in this example. The outputs of the gates 45 and 46 are outputted from the subtracter 17 through an OR gate 48.
When the most significant bit of the output of the adder 43 is "0", the output of the adder 43 becomes the output of the subtracter 17 as is, and when the most significant bit is "1", "1000" is the output of the subtracter 17. is output from.

According to the above configuration, as described above, while the gate signal exists, the output of the main memory 19 is subtracted by a predetermined value, and for example, the detection signal in FIG. 26 is removed, but the fish school reflection signal 26 in the background noise remains, and since the subtraction operation by the gate signal is not performed for the reflection signal near the seabed, the small level fish school reflection signal 26 remains.
remains. Therefore, although the background noise display 36 disappears on the display surface of the display 31, the fish school reflection signal display 34 remains and can be easily and immediately read. Moreover, since the width _T1 of the gate signal can be adjusted, the operator can turn the knob 3 while looking at the display screen.
9 can be adjusted to arbitrarily adjust the range of background noise to be removed so as to leave a low-level fish school reflection signal near the seabed. Further, the predetermined value to be subtracted can also be changed manually as necessary.

This configuration is shown in the figure with a subtracter 1 for performing the above-mentioned subtraction on the readout output of the main memory 19.
7, and the output of the subtracter 17 is sent to the color converter 2.
Supply to 3.

Further, a variable gate signal generator 38 is provided between the display controller 22 and the subtracter 17 to generate the above-mentioned gate signal necessary to create a subtraction operation period of the subtracter 17.

To generate this gate signal, the display controller 22 supplies a horizontal synchronization signal for the display 21, that is, a trigger synchronized with the main scanning synchronization signal, to the variable gate signal generator 38.
A gate signal from the subtracter 17 is supplied to the subtracter 17.

〔Effect of the invention〕

According to this invention, as described above, the so-called
After the noise component due to the reverberation component immediately after transmission is removed by STC, the noise, for example, background noise, is removed by subtracting a small digital value from each digital value in the readout output of the main memory 19, and this removal is performed. Since the range is variably operated by a variable gate that can vary the range from the point corresponding to each transmission to the end point of the reflected signal obtained by that transmission, that is, the detection signal, it is possible to operate under water or on the sea surface in the detection area. Even if the generation range of the noise to be removed varies depending on the situation, the noise can be removed accordingly.

In other words, such noise occurs immediately after transmission, and the period during which it continues to occur varies depending on, for example, the relationship between the magnitude of the transmission output and the amount of plankton in the water, etc. The original state before subtraction processing is stored in the main memory in an amount corresponding to the display screen, so if you operate the variable gate above, you can see the original state displayed and the state during subtraction processing. It has the advantage that it can be provided with a simple and inexpensive configuration by simply adding a subtracting means and a variable gate means, allowing the user to judge the difference between the screen and the screen on the display screen.

[Brief explanation of drawings]

The drawings show an embodiment, and FIG. 1 is a block diagram of the device, FIG. 2 is a signal waveform diagram for explaining the principle of operation, FIG. 3 is a schematic diagram of the display screen for explaining the display operation, and FIG. 4 is a diagram of the device. is a configuration diagram of a main circuit. 11... Transmission/reception controller, 12... Transmitter, 13
... Transmission/reception switch, 14... Transmitter/receiver, 15... Receiver, 16... AD converter, 17... Subtractor, 1
8... Buffer memory, 19... Main memory, 21
... Display device, 22 ... Display controller, 23 ... Color converter, 38 ... Variable gate signal generator.

Claims (1)

[Claims] 1. The reflected signal obtained by periodically transmitting a pulse wave is sufficiently lowered in gain at the time of transmission, and the gain is increased as time passes, and the received signal is received.
After A/D conversion into a digital signal, a series of the reflected signals (hereinafter referred to as detection signals) obtained in response to the pulse wave are captured, and each of the detection signals is arranged in chronological order on a display screen, and The oldest detection signal is stored in the main memory so as to be erased, and a digital signal obtained by repeatedly reading the main memory in response to display control of a raster scanning display (hereinafter referred to as a storage read digital signal) is obtained. In an echo detection device capable of displaying each detection signal in color by converting it into a color signal corresponding to each digital value and providing it to the raster scanning display, the method comprises: a. removing small noises in the detection signal; When the low level digital value of the digital signal is subtracted, and the subtraction result is less than or equal to the 0 level digital value, the storage read digital signal is sent to a subtraction circuit that outputs the 0 level digital value. subtractive color conversion means for obtaining the color signal based on each digital value obtained by applying the subtractive color conversion means, b. gate generation means; c. variable operation means for variably operating the end point of the variable gate to a point corresponding to the end point of the detection signal; d. subtraction for operating the subtraction means only during the period of the variable gate. An apparatus characterized in that it comprises operating means.