JPH0627226A - Ultrasonic distance detector with variable beam width - Google Patents

Abstract

PURPOSE:To widen the beam width of transmitting/receiving wave for short maximum detectable distance and make narrow the beam width as the maximum detectable distance increases in response to selection switching of the maximum detectable distance. CONSTITUTION:A weighting control signal corresponding to a selected maximum detectable distance is delivered from a weighting control means (weighting control section 5) to a weighting section 2 comprising weighting circuits SA1-SAN corresponding to oscillators Z1-ZN in a transceiver 4 in order to weight the amplitude of signal outputted from a transmission signal generating means (transmission signal generating section 1). Weighted signal is delivered to each oscillator in the transceiver 4 and the beam width is determined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for improving the detection performance and the detection range by changing the beam width of a transmission beam of an ultrasonic detection device according to a selected maximum detection distance.

[0002]

2. Description of the Related Art Ultrasonic detectors such as sonars for fish detection and active sonars transmit sound waves into the water and receive sound reflected from fish schools and other reflective objects (also referred to as targets) to record them in a recorder or CRT. By displaying on a display device, a reflective object is detected, and the distance and azimuth to the reflective object are known. Then, normally, the maximum detection distance displayed on the recorder or the display device can be switched in several steps such as 100 m, 200 m, 400 m, and 800 m, and the selection is switched according to the distance to be detected. For example, selecting a maximum detection distance of 100m is 100m
This is a case where the information of the short distance within the range is required and the information of the distance of 100 m or more is unnecessary.

On the other hand, the maximum detection distance of 800 m is selected when it is desired to obtain target information from 400 m to 800 m which is invisible when the maximum detection distance is 400 m. The maximum detection distance is thus selected according to the distance of the target to be observed. However, in the conventional ultrasonic detection device, the beam width of the transmitted beam is fixed to a constant width even if the maximum detection distance is selected.

[0004]

However, generally, if the transmission power input to the transducer is the same, the sound pressure energy in the directivity direction will be concentrated because the sound energy is concentrated in a narrow angular range as the beam width becomes narrower. It becomes high and the reflection level from a distant target also becomes high, which is suitable for detecting a distant target. Even if the beam width is narrow, the beam irradiation area becomes large at a distant position, so that a sufficient beam irradiation space can be obtained.

On the other hand, when the beam width is widened, the acoustic energy is dispersed in a wide angle range, so that the sound pressure level in each direction within the beam width becomes relatively low. Therefore, short-range targets are targets for detection. Since the beam width is wide, the beam irradiation area is large even at a short distance, and a sufficient beam irradiation space can be obtained.

As described above, a narrow beam width is suitable for detecting a long-distance target, and a wide beam width is suitable for detecting a short-distance target. However, since the beam width has been constant in the past regardless of the distance of the detection target, the following problems occur.

That is, in the case of a narrow beam width, it is suitable for distant detection, but naturally the beam irradiation area is small at a short distance, and the beam width at a short distance does not deviate from the beam width at a long distance. It is easy to miss the detection. On the other hand, when the beam width is wide, it is possible to detect a target at a short distance in a wide angle range, but it becomes difficult to detect a target at a long distance. In addition, there is a problem that the advantages and disadvantages of both wide and narrow are mixed in the middle beam width.

The object of the present invention is to solve the above problems.
By changing the beam width according to the selected maximum detection distance, widening the beam width when the maximum detection distance is short and narrowing the beam width as the maximum detection distance becomes longer, An object of the present invention is to provide an ultrasonic detection device that detects a target in a wide range.

[0009]

The present invention has the following means for achieving the above object. That is, the transmitted beam width variable ultrasonic detection device of the present invention includes a transducer including a plurality of transducers arranged therein; and a maximum detection distance selecting means;
Transmission signal generating means for generating a pulsed transmission signal having a transmission time and a transmission cycle corresponding to the selected maximum detection distance; and a weighting control means for generating a weighting control signal corresponding to the selected maximum detection distance And; a weighting unit for weighting the amplitude of each transmission signal supplied to each transducer of the transducer according to a weighting control signal.

[0010]

The operation of the transmitted beam width variable ultrasonic detecting apparatus of the present invention having the above-mentioned constitution will be described below. First, it is possible to change the width of the main transmission beam by changing (weighting) the excitation amplitude of each transducer of a transducer with multiple transducers arranged from the same amplitude state. Will be explained.

Now, as shown in FIG. 3A, Z ₁ to Z ₈
8 is arranged linearly, and the transmission beam is as shown in FIG. 3B when the excitation amplitude of each vibrator is the same. On the other hand, when the excitation amplitude of each oscillator is weighted, for example, the excitation amplitude of Z ₄ and Z ₅ is set to be maximum, and this is set to 1. Z ₁ and Z ₈ are 0.1 and Z ₂ and Z ₇ are 0.3. , Z ₃ and Z ₆ are 0.7
When the excitation is performed with the ratio, the transmitted beam becomes as shown in FIG.

It can be seen that the width of the main transmission beam is wide compared with FIG. The ratio of another excitation amplitude to the maximum excitation amplitude when weighting is called a weighting coefficient, and the width of the main transmission beam can be variously changed by changing the value of this weighting coefficient. The present invention is based on the fact that the width of the main transmission beam can be changed by thus weighting the excitation amplitude of each transducer.

In the device of the present invention, the maximum detection distance that can be displayed on the display surface of the display device can be selected by the maximum detection distance selection means, and the transmission signal generation means transmits according to the selected maximum detection distance. A pulse-shaped transmission signal is generated with time and a transmission repetition period (also simply referred to as a transmission period). That is, when the maximum detection distance is short, the operation is performed with a short transmission cycle, and the longer the maximum detection distance is, the longer the transmission cycle is. However, this does not mean that it is not possible to display a short maximum detection distance in a long transmission cycle, but it is not possible to normally detect a target longer than the distance corresponding to the transmission cycle.

Further, the longer the transmission time is, the easier it is to detect a distant target. Therefore, the transmission time is set according to the maximum detection distance. However, since it does not have to be changed every time the maximum detection distance changes, the same transmission time may be used for the maximum detection distances in multiple stages.

In this way, the transmission signal generating means operates according to the selected maximum detection distance, while the weighting control means outputs the weighting control signal for performing the preset weighting on the selected maximum detection distance. Occur. At the time of presetting, a weighting control signal with a weighting coefficient that widens the transmitted beam width as the maximum detection distance becomes larger is generated, so that transmission is performed in conjunction with selection of the maximum detection distance. The wave beam width will change. The weighting means can receive the weighting signal from the weighting control means and weight the excitation amplitude of each transducer to form a transmitted beam having a beam width corresponding to the selected maximum detection distance.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of the device of the present invention. The range switch 6 is a maximum detection distance selection means, and when the maximum detection distance selected in advance in several stages is selected, the selection signal is sent to the transmission signal generator 1 and the weighting controller 5. The transmission signal generator outputs the transmission signal of the ultrasonic frequency at the transmission time and the transmission cycle that are predetermined for the selected maximum detection distance. The output transmission signal is applied to each of the weighting section 2 weighting circuits SA ₁ -SA _N.

On the other hand, the weighting control section which receives the selection signal from the range switcher 6 sends each weighting circuit SA _{1 a} weighting control signal which gives a predetermined beam width to the selected maximum detection distance. and it sends it to the ~SA _N. The weighting circuits SA _{1 to} SA _N use the same type of circuit, and the details thereof are as shown in FIG. Reference numeral 7 denotes an operational amplifier (hereinafter referred to as an operational amplifier). The transmission signal from the transmission signal generation unit 1 is added to one input end of the operational amplifier 7 after being inverted in polarity after passing through the resistor R ₅ , and the other input end is It is kept at a constant potential. The output signal of the operational amplifier 7 is output to the outside and fed back to the output side of the resistor R ₅ via field effect transistors (hereinafter referred to as FETs) Q _{1 to} Q ₄ and resistors R _{1 to} R ₄ .

The FETs Q _{1 to} Q ₄ function as switches which are turned on and off by control signals CT _{1 to} CT ₄ applied to their respective bases. Control signal CT ₁ to CT ₄ from weighting controller 5 is added to FETs Q ₁ to Q ₄ as weighting control signal in this embodiment. Then, only _{one of the} control signals CT _{1 to} CT ₄ becomes a signal for turning on the FET. For example, when the control signal CT ₁ turns on the FET Q ₁ , the resistor R ₁ forms a feedback circuit. The gain G of such a feedback amplifier circuit is expressed by the ratio of the resistance value of the resistor R ₅ on the input side to the resistance value of the feedback resistor, and is given by Formula 1.

[0019]

[Equation 1]

Therefore, the weighting control signals CT _{1 to} CT ₄
By selecting which of the FETs Q _{1 to} Q ₄ is turned on by the feedback resistor, the feedback resistors are set to the resistors R _{1 to} R _4.
Since the gain of the weighting circuit can be changed by selecting from among these, the input transmission signal can be weighted and output. Weighting control signal CT ₁ to CT ₄ from weighting controller 5 is directed in the same way to all the weighting circuits SA ₁ -SA _N.

In this embodiment, the maximum detection distance that can be selected by the range switch 6 is 100 m, 200 m, 400 m, 800.
There are 4 levels of m. When 100 m is selected, the weighting control unit 5 receiving the selection signal causes the weighting control signal C
When T ₁ is turned on, the FET Q _{1 of} each weighting circuit is turned on and the resistor R ₁ of each weighting circuit becomes a feedback resistor. Similarly, when 200 m is selected, FET Q ₂ is turned on and resistor R ₂ becomes a feedback resistor. At 400 m, resistor R ₃
However, at 800 m, the resistor R ₄ becomes a feedback resistor.

Therefore, when the maximum detection distance of 100 m is selected, the gains of the weighting circuits SA _{1 to} SA _N are the resistance value of R ₁ / the resistance value of R ₅ , and at the maximum detection distance of 200 m,
The gain is the resistance value of R ₂ / R ₅ resistance value.
At 0 m, the resistance value of R ₃ / R ₅ becomes 800 m
Then, the resistance value is R ₄ / R ₅ resistance value.

On the other hand, a desirable beam width is separately defined for each maximum detection distance, and a weighting factor for obtaining the beam width is also calculated. Therefore, a gain corresponding to the weighting factor can also be calculated. it can. Therefore, by setting the value of the feedback resistor of each weighting circuit so as to obtain the above-mentioned gain, when the maximum detection distance is selected, a transmission beam having a beam width corresponding to that is formed. Become.

That is, when the maximum detection distance of 100 m is selected, the gain of each weighting circuit is the resistance value of R ₁ / R ₅
Is determined by the resistance value of the resistor R ₅ for each weighting circuit so that the gain ratio of each weighting circuit matches the weighting coefficient.
By setting the values of R ₁ and R _1, a desired beam width can be obtained. The same applies to other maximum detection distances.

In practice, by setting the resistance value of the resistor R ₅ to the same value for the weighting circuits SA ₁ to SA _N , the gain between the weighting circuits can be increased to the maximum detection distance 1
For 00m, it is the ratio of the resistance value of the resistor R ₁ of each circuit. Therefore, it suffices to set the resistance value of the resistor R ₁ of each circuit so that this ratio matches the weighting coefficient. The same applies to the resistors R ₂ , R ₃ , and R ₄ for the maximum detection distances of 200 m, 400 m, and 800 m, respectively.

Thus, the weighting circuit S of the weighting unit 2
A ₁ -SA _N in the corresponding transmission amplifier PA ₁ ~PA _N transducer of the transducer 4 which is amplified to a predetermined transmission level by Z transmission signal subjected to weighting the transmission amplifier 3
_{1 to} Z _N , and these are excited to be transmitted from the wave transmitter / receiver 4 with a predetermined beam width. The weighting circuit in the present invention is not limited to the example of FIG. 2 as long as it is a circuit in which the excitation level to each transducer of the wave transmitter / receiver can be individually set according to the weighting coefficient.

[0027]

As described above, the ultrasonic wave detecting apparatus for variable transmission beam width of the present invention can change the transmission beam width by weighting the signal level for exciting each transducer of the transmitter. In addition, the transmission beam width is narrow when the maximum detection distance is long, and wide when the maximum detection distance is long, in conjunction with the selection of the maximum detection distance set in multiple stages. Compared to the case where the transmission beam width is fixed, the level of transmission and reception is higher for targets far away and the detection performance is improved, while the advantage of being able to detect targets in a wider angle range for targets at short range is there.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a transmission beam width variable ultrasonic detection apparatus of the present invention.

FIG. 2 is a circuit diagram of an example of a weighting circuit used in the embodiment of FIG.

FIG. 3 is an explanatory diagram showing that the transmission beam width is changed by weighting the excitation level of each transducer of the wave transmitter / receiver.

[Explanation of symbols]

1 transmission signal generation section 2 weighting section 3 transmission amplification section 4 transmitter / receiver 5 weighting control section 6 range switch 7 operational amplifier (operational amplifier) CT _{1 to} CT ₄ weighting control signal Q _{1 to} Q ₄ field effect transistor ( FET) R ₁ ~R ₅ resistors SA ₁ -SA _N weighting circuit PA ₁ ~PA _N transmit amplifier Z ₁ to Z _N vibrators

Claims (1)

[Claims] 1. A transducer comprising a plurality of transducers arranged; a maximum detection distance selecting means; and a pulsed transmission signal having a transmission time and a transmission cycle corresponding to the selected maximum detection distance. Transmitting signal generating means for generating a weighting control signal corresponding to a selected maximum detection distance; and weighting the amplitude of each transmitting signal supplied to each transducer of the transducer. A transmission wave beam width variable ultrasonic detection device, comprising: a weighting means for weighting based on a control signal;