JPH05180928A - Underwater detecting device - Google Patents

Abstract

PURPOSE:To fetch signals received through an ultrasonic receiver without saturation and to arbitrarily execute gain adjustment by compressing and digitizing the received signals. CONSTITUTION:When a transmitting section 4 outputs a drive signal to a transmitter-receiver 2 in accordance with a trigger signal from a controller 22, ultrasonic waves are radiated into the sea. Upon receiving echoes, the transmitter-receiver 2 outputs received signals at a voltage level corresponding to the intensity of the echoes. The received signals are inputted to a signal compression circuit 8 after they are amplified and detected at a reception circuit 6. The circuit 8 outputs the received signals after logarithmic compression. As a result, the received signals are fetched over a wide dynamic range. Then the received signals are digitized by means of an A/D converter 10 and stored in a memory 14. A gain adjustment processing section 16 performs gain adjustment by reading out the data stored in the memory 14. Namely, the section 16 changes the dynamic range by changing a gain by raising or lowering a quantization level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underwater detection device,
In particular, it relates to improvement of gain adjustment of a reception signal obtained by an ultrasonic transmitter / receiver.

[0002]

2. Description of the Related Art Conventionally, some underwater detection devices such as a fish finder employ the configuration shown in FIG.

In this underwater detecting apparatus, an ultrasonic wave drive signal is output from the transmitting section b to the ultrasonic wave transmitter / receiver c in response to a trigger signal for ultrasonic wave emission from the controller a, whereby the ultrasonic wave transmitter / receiver c is output. Ultrasonic waves are emitted from the sea, for example. When ultrasonic echoes from the sea and the bottom of the sea are received by the ultrasonic transducer c, the ultrasonic transducer c outputs a reception signal having a voltage level corresponding to the strength of the ultrasonic echo. The received signal is amplified and detected by the receiving circuit d, and then input to the gain adjusting circuit e. The gain adjusting circuit e is composed of a gain controllable linear amplifier. The received signal amplified to a predetermined level by the gain adjusting circuit e is digitized by the A / D converter f and then stored in the memory g. It And
Received signal data read by the controller a from the memory g in synchronism with TV scanning is output to CRTh to display an image.

By the way, in the above gain adjusting circuit e, the automatic gain control for automatically changing the gain according to the magnitude of the received signal level by the gain control signal from the controller a.
(AGC) processing, time gain control (TVG) processing for changing the gain with respect to the received signal over time, and the like are performed so that a received signal having an appropriate S / N ratio can be obtained.

[0005]

However, in the conventional gain adjusting circuit e, the gain adjustable dynamic range is still narrower than the dynamic range of the ultrasonic echo. That is, the dynamic range of the ultrasonic echo is 100 dB or more, whereas the dynamic range of the conventional gain adjusting circuit e is 40 dB or less. Therefore, if the gain setting of the gain adjustment circuit is increased in order to display the received signal based on the weak ultrasonic echo, the received signal will be saturated with the ultrasonic echo from the school of large fish or the seabed. , These are indistinguishable. On the contrary, if the gain setting is made small, the seabed and the like can be discriminated, but the ultrasonic echo from a small fish such as plankton is weak, which makes it difficult to discriminate the fish school.

Further, in the conventional one, the controller a
Since the gain control circuit e directly changes the gain of the gain control circuit e, there is a problem that the gain control circuit e is easily affected by noise.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is reflected from a strong ultrasonic echo reflected at a short-distance seabed or the like to a long-distance small fish or the like. The reception signal obtained over a wide range up to a weak ultrasonic echo can be captured without being saturated, and is less susceptible to noise, and the gain can be adjusted arbitrarily.

Therefore, in the underwater detection apparatus of the present invention, a signal compression circuit for signal-compressing the reception signal obtained by the ultrasonic transmitter / receiver and an A / D for digitizing the reception signal compressed by the signal compression circuit. The conversion means, the memory for storing the reception signal data obtained by digitization by the A / D conversion means, and the gain adjustment processing means for performing the gain adjustment processing on the reception signal data stored in the memory are provided. ..

[0009]

In the above structure, since the received signal obtained by the ultrasonic wave transmitter / receiver is compressed by the signal compression circuit,
Received signals based on ultrasonic echoes with a wide dynamic range can also be captured. Moreover, in this case, since the gain adjustment by the control from the controller is not performed, it is hard to be affected by noise. Then, the received signal data obtained by being digitized by the A / D conversion means after being signal-compressed by the signal compression circuit is stored in the memory. The gain adjustment processing means performs gain adjustment processing on the received signal data. For example, the gain is changed by raising or lowering the range of the quantization level to be the data clipping target, and the dynamic range is changed by expanding or reducing the range.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the overall structure of an underwater detecting apparatus according to an embodiment of the present invention.

In the figure, 1 is the whole of the underwater detection apparatus, 2 is an ultrasonic wave transmitter / receiver, 4 is a transmitter for outputting a drive signal for ultrasonic wave emission to the ultrasonic wave transmitter / receiver, and 6 is an ultrasonic wave transmitter / receiver. A receiving circuit that amplifies and detects the received signal obtained by the wave filter 8,
Is a signal compression circuit for compressing the received signal that has passed through the reception circuit 6, and a logarithmic amplifier is applied in this example. Reference numeral 10 is an A / D converter for digitizing the reception signal compressed by the signal compression circuit 8, and 12 is a CPU.

The CPU 12 mainly comprises a memory 14, a gain adjustment processing section 16, a video RAM 18, a setting section 20, and a controller 22.

The memory 14 stores received signal data obtained by digitization by the A / D converter 10, and is composed of, for example, a RAM. Further, the gain adjustment processing unit 16 performs gain adjustment processing on the received signal data stored in the memory 14. The video RAM 18 stores the received signal data whose gain has been adjusted by the gain adjustment processing unit 16 at a predetermined address position corresponding to the display screen, and the setting unit 20 operates to input a setting signal for gain adjustment. Therefore, the controller 22 changes the data clipping target range of the gain adjustment processing unit 16 in accordance with the setting signal from the setting unit 20, and the transmission unit 4,
It controls the memory 14, the video RAM, and the like.

A color CRT 24 displays the received signal data stored in the video RAM as an image.

Next, the operation of the underwater detecting apparatus having the above-mentioned structure will be described.

In response to a trigger signal for ultrasonic wave emission from the controller 22, an ultrasonic wave drive signal is output from the transmitter 4 to the ultrasonic wave transmitter / receiver 2, whereby the ultrasonic wave transmitter / receiver 2 is transmitted.
Ultrasonic waves are emitted from the sea, for example. When ultrasonic echoes from the sea and the sea bottom are received by the ultrasonic transducer 2, the ultrasonic transducer 2 outputs a reception signal having a voltage level corresponding to the strength of the ultrasonic echo. The signal is amplified and detected by the receiving circuit 6, and then input to the signal compression circuit 8.

The signal compression circuit 8 logarithmically compresses the received signal and outputs it. Therefore, the received signal based on the ultrasonic echo can be captured in a wide dynamic range, and since the signal compression circuit 8 does not perform the gain adjustment under the control of the controller 22, the influence of noise is small.

The received signal logarithmically compressed by the signal compression circuit 8 is digitized by the A / D converter 10,
It is stored in the memory 14.

Next, the gain adjustment processing section 16 causes the memory 1
The received signal data stored in 4 is read, and the received signal data is first subjected to a time gain control (TVG) process for changing the gain of the received signal according to the passage of time. This is because, as shown in FIG. 2 (a), a function curve showing the relationship between time and offset amount is stored in advance, and as shown in FIG. The above offset amount is added to the data of the received signal obtained based on For example, for received signal data corresponding to time t ₁ , an offset amount of −Δ ₁ is added, and for received signal data corresponding to time t ₂ (> t ₁ ) −Δ ₂ (however, | Add the offset amount of Δ ₂ | <| Δ ₁ |). This compensates for the attenuation associated with the propagation of ultrasonic echoes.

Subsequently, the gain adjustment processing unit 16 causes the TV
As shown in FIG. 3, with respect to the received signal data after the G process, a process of cutting out the data existing within the range R of the predetermined quantization level to be the gain adjustment target is performed. For example, if the range R of the quantization level that is the target of data cut is lowered, the received signal data with a small quantization level is preferentially taken out, which means that the gain of the received signal is increased, and conversely, the range is increased. If R is increased, received signal data with a large quantization level is preferentially taken out, which means that the gain of the received signal is lowered. Further, if the range R of the quantization level to be cut out is expanded, the received signal data of a wide range of levels is taken out, which means that the dynamic range of the received signal is expanded, and conversely, the range of the quantization level. If R is reduced, the received signal data of a level within a narrow range is taken out, which means that the dynamic range of the received signal is narrowed.
To raise, lower, enlarge, or reduce the range R of the quantization level, when a setting signal for gain adjustment is input from the setting unit 20, the controller 22 responds to this by a gain adjustment processing unit 1.
6 is controlled.

Then, the received signal data which has been subjected to the gain adjustment processing in the gain adjustment processing section 16 and is extracted is the video RAM 1.
8 is stored at a predetermined address position corresponding to the display screen. After that, the controller 22 controls the video RAM 1
Received signal data is read from 8 in synchronism with TV scanning and output to the color CRT 24. As a result, a clear image having an appropriate S / N ratio is displayed.

[0022]

According to the present invention, the signal compression circuit can take in a received signal obtained based on an ultrasonic echo in a wide dynamic range without saturating it, and is less susceptible to noise. Further, since the data is processed after being received as the received signal data in the memory, the gain adjustment according to the S / N ratio can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an underwater detection device according to an embodiment of the present invention.

FIG. 2 Time gain control in the underwater detector of the present invention
It is an explanatory view of (TVG) processing.

FIG. 3 is an explanatory diagram of gain adjustment processing and dynamic range adjustment processing in the underwater detection device of the present invention.

FIG. 4 is a block diagram showing an overall configuration of a conventional underwater detection device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Underwater detection device, 2 ... Ultrasonic wave transmitter / receiver, 8 ... Signal compression circuit, 14 ... Memory, 16 ... Gain adjustment processing part.

Front page continuation (72) Inventor Mitsuhiro Inoue 9-52 Ashihara-cho, Nishinomiya-shi, Hyogo Furuno Electric Co., Ltd. (72) Inventor Mitsuhiro Takeda 9-52 Ashihara-cho, Nishinomiya-shi, Hyogo Furuno Electric Co., Ltd. (72) Inventor Takeshi Yamaguchi 9-52 Ashihara-cho, Nishinomiya-shi, Hyogo Prefecture Furuno Electric Co., Ltd.

Claims (1)

[Claims] 1. A signal compression circuit for compressing a reception signal obtained by an ultrasonic wave transmitter / receiver, A / D conversion means for digitizing the reception signal compressed by the signal compression circuit, and this A / D An underwater detection apparatus comprising: a memory that stores received signal data obtained by digitization by a conversion unit; and a gain adjustment processing unit that performs a gain adjustment process on the received signal data stored in the memory.