JPH0261582A - Ultrasonic detector - Google Patents

Abstract

PURPOSE:To enable detection of an object in a short range by turning ON a gate simultaneously with a drop of a reverberation level to a specified level immediately after the feeding of an ultrasonic wave. CONSTITUTION:A level detection means is provided which checks a reverberation level immediately after the feeding of an ultrasonic wave to detect a drop of the reverberation level to a specified level and a gate control means is provided to turn ON a gate when an output of a level detection means is outputted. The gate is turned ON by the gate control means simultaneously with a drop of the reverberation level to a specified level immediately after the feeding of an ultrasonic wave so that the reception of an ultrasonic wave. On the other hand, when time to the drop of the reverberation level to the specified level exceeds a preset time from the transmission thereof, the gate is turned ON forcibly after a fixed time elapses. Thus, the gate is also turned ON forcibly after a fixed time from the transmission while always being turned ON at the end of the reverberation regardless of a change in duration of the reverberation to make detection ready thereby enabling detection in a short range.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses ultrasound pulses to detect the presence or absence of a target at a relatively short distance, such as a human body detector for an automatic door or a visitor alarm. Regarding the detector.

[Conventional technology]

For example, the one shown in FIG. 4 is generally known as a human body detector for automatic doors. That is, in the figure, the transducer E of the ultrasonic detector is installed at an appropriate height position of the door C installed between the ceiling A and the floor 8, that is, at a blind spot. This transducer E is installed at a position slightly higher than a person's height, and is directed diagonally downward so that when a person coming in or out pauses in front of the door C, the ultrasonic wave is irradiated onto their head F. is oriented to.

By repeatedly transmitting and receiving ultrasonic pulses from this transducer E, reflected waves from the head F are received.
By detecting the presence of this reflected wave, door C is controlled to be open for a certain period of time.

The wave receiving operation by the transducer E starts after transmitting the ultrasonic pulse, but in order to improve the minimum detection distance performance and enable detection even by tall people such as foreigners, the pulse width must be narrow. , and it is desirable to start receiving waves at the same time as transmitting ends.

By the way, when a transducer is excited by supplying power,
Even if the power supply is stopped, the vibrations do not stop immediately, but continue asymptotically for a certain period of time (called reverberation). Therefore,
If wave reception is started immediately after wave transmission ends, this reverberation will be mixed into the received signal, causing malfunction of the detector.

For this reason, conventionally, although it is preferable to start the wave receiving operation early, the wave receiving operation is started from a predetermined time point when the above-mentioned reverberation is considered to have disappeared, and the reverberation is included in the wave receiving period. I'm trying to make sure it doesn't get lost.

On the other hand, the duration of the reverberation is not fixed, and is greatly influenced by external conditions such as temperature in addition to slight variations between the transducers. Therefore, by determining the start point of wave reception in consideration of the time in which reverberation lasts the longest, it is possible to completely prevent reverberation from being mixed in.

[Problem to be solved by the invention]

However, as a result, it becomes difficult to detect tall people, and in order to do this effectively,
It would be possible to install the transducer at a high place, but doing so would force an improvement in the transmitting/receiving power or the receiving sensitivity, which would cause problems in terms of economics, structure, and price.

The present invention was made by focusing on the fact that the duration of reverberation is relatively variable, and an object of the present invention is to start the wave receiving operation immediately after the reverberation disappears, so that detection at short distances can be performed sufficiently. shall be.

[Means to solve the problem]

The present invention detects the presence or absence of reflected waves from a target object by repeatedly transmitting sonic pulses using an ultrasonic transducer, and after a predetermined time has elapsed since the transmission, by turning on a gate and receiving the waves. In the ultrasonic detector, a level detection means detects a reverberation level immediately after transmitting a wave and detects that the reverberation level has decreased to a predetermined level, and a gate control means turns on the gate when the output of the level detection means is output. The present invention provides an ultrasonic detector characterized by having the following features.

[Effect]

According to the present invention, at the same time as the reverberation level immediately after transmission drops to a predetermined level, the gate is turned on by the gate control means and reception of waves is started.

On the other hand, if the time required for the reverberation level to drop to a predetermined level exceeds a predetermined time from wave transmission, the gate is forcibly turned on when the time elapses.

〔Example〕

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

In the figure, 1 is an ultrasonic transducer that transmits ultrasonic pulses. Transmission of ultrasonic pulses by the ultrasonic transducer 1 is performed by the following closed circuit.

That is, the power supply circuit 2 supplies a constant current to the integrating circuit 3 at a predetermined voltage, and the monostable multi 4 outputs a pulse signal of a constant width each time the output of the integrating circuit 3 reaches a predetermined level. . Further, this monostable multi 4 outputs the above-mentioned pulse signal to a gate signal generation circuit 5 (hereinafter referred to as gate 5). The gate 5 is activated after a certain period of time has elapsed after the input of the pulse signal, that is, at t2.
A pulse signal that lasts from time t3 to time t3 is sent out.

The switching circuit 6 outputs a signal at the rising or falling timing of the monostable multi 4, and discharges the charge accumulated in the integrating circuit 3, so that the integrating operation by the integrating circuit 3 is repeated at a constant cycle. There is.

The monostable multi 7 outputs a pulse with a width ts at every rising timing of the monostable multi 4, and the oscillation circuit 8 continues oscillation at a predetermined high frequency for a period of the width ts.

This oscillation output is power amplified by a driver 9 in the next stage for driving the transducer 1.

In this way, an ultrasonic pulse having a width ts (FIG. 2a) is transmitted from the transducer 1 in a predetermined direction.

The return wave reflected by the target is also received by the transducer 1 (Fig. 2b), amplified and detected by the amplifier circuit 10 and the next stage detection circuit 11 (Fig. 2d), and then level detected. The signal is sent to circuit 12. The level detection circuit 12 detects the received signal level immediately after transmission, and at the time t1 when the received signal level reaches a predetermined threshold level Vs, the memory 1
3 outputs the comparison signal. That is, level detection circuit 1
2 detects the point in time when the reverberation included immediately after transmission (Dl in FIG. 2, 81) drops to level Vs.

When the detection signal from the level detection circuit 12 is input, the memory 13 outputs a signal to turn on the gate 5 from time t1 to at least time t2.

As a result, if the reverberation immediately after transmission has decreased to level V8 by time t2, the gate 5 will send out a pulse from time t1 to time t3, which is the time when the reverberation has decreased (Fig. 2C).
, on the other hand, if the level does not decrease to V8 by time t2, a pulse is sent from time t2 to time t3 (Fig. 3C).
). In other words, even if the duration of reverberation becomes longer due to temperature or the like and exceeds time t2, the gate 5 is activated at time t.
2, it is forcibly turned on.

The integrating circuit 14 extracts only received signals having a certain width or level and removes white noise and other noises to prevent malfunctions. This integrating circuit 14 is designed to operate only during the period when the pulse signal (C in FIG. 2 and C in FIG. 3) is sent from the gate 5.

The flip-flop 15 is reset in synchronization with the transmission or immediately after receiving the signal from the monostable multi 7, and is configured to send out the output signal from the integrating circuit 14, that is, when a target object is detected. is being done. The switching circuit 16 continues to output an output while the flip-flop 15 outputs an output signal, and operates the six relays 17 that drive other loads such as automatic doors. In addition, the first
In the illustrated embodiment, the relay 17 is operated when the output signal from the integrating circuit 14 is detected twice in a row to prevent false detection.

In the above circuit configuration, the reception operation will next be explained using FIGS. 2 and 3. Note that FIG. 2 shows a time chart when the reverberation is within time t2, that is, when the gate 5 is turned on from time t1, and FIG. 3 shows a time chart when the reverberation is beyond time t2,
That is, a time chart is shown when the gate 5 is turned on from time t2.

First, in FIG. 2, an ultrasonic pulse A1 with a width ts is transmitted, and immediately after that, a remaining FB1 and a target signal B2 are transmitted.
is detected by the detection circuit 11. Then, the level detection circuit 12 detects the level of the remaining gD1 immediately after transmission, and sends a detection signal to the memory 13 when the level drops to Vs. Therefore, the memory 13 turns on the gate 5 from the time it receives the detection signal, that is, from the time t1. The gate signal C1 from the gate 5 continues until time t3, and thereby all people from tall to short are detected.

Further, the above-mentioned time t3 can be set outside the detection range, for example, in the case of a place where entry of children and the like is restricted.

Then, the signal D received immediately after the generation of the gate signal C1
2 is extracted by the integrating circuit 14 and subjected to so-called correlation processing by the switching circuit 16. When the output from the integrating circuit 14 is detected twice in a row, it is determined that there is a target.
Switching circuit 16 sends output E1 to relay 17
operate.

Next, in FIG. 3, an ultrasonic pulse A1 having a width ts is transmitted, and immediately after that, a reverberation B1 and a target signal B2 are detected by the detection circuit 11. Then, the level detection circuit 12 detects the level of the reverberation D1 immediately after transmission. in this case,
Since the reverberation is long and its level has not decreased to Vs at time t2, the level detection circuit 12 does not output a detection signal, and therefore the gate 5 turns on from time t2.

The gate signal C1 from the gate 5 continues until time t3, whereby a person of normal height can be detected. and,
A signal D2 received immediately after the gate signal C1 is generated is extracted by an integrating circuit 14, and subjected to so-called correlation processing in a switching circuit 16.

When the output from the integrating circuit 14 is detected twice in a row, it is determined that there is a target, and the switching circuit 16 outputs E.
1 to activate relay 17.

According to the above embodiment, the gate is forcibly turned on after a certain period of time after transmission, that is, after time t2, and the gate is always turned on from the point at which the reverberation ends, regardless of fluctuations in the duration of the reverberation. This enables detection at short distances.

Next, FIG. 5 is a circuit diagram showing a second embodiment of the present invention.

In summary, the present embodiment involves alternately and repeatedly transmitting a detection pulse with a long pulse width and a detection pulse with a short pulse width, and will be explained below with reference to the time charts of FIGS. 5 and 6.

Note that in the figure, the same numbers as in FIG. 1 indicate the same items.

In the figure, a transmission pulse with a long width ts1 (Fig. 6 A1) is transmitted by an integrating circuit 3, a monostable multi 4a, and a monostable multi 7°t.
1) Determined. That is, the monostable multi 4a is configured to send out a pulse signal of a constant width each time the output of the integrating circuit 3 reaches a predetermined level. monostable multi 7
a outputs a pulse having a width tsl at each rise timing of the monostable multi-channel 4a. The oscillation circuit 8 continues to oscillate at a predetermined high frequency during the period of width ts1, and the oscillation output is power amplified by the driver 9 in the next stage for driving the transducer 1. In this way, the ultrasonic pulse A1 having the width tsj is transmitted from the transducer 1 in a predetermined direction.

On the other hand, the transmission pulse having a short width ts2 (A2 in FIG. 6) is determined by the integrating circuit 3, the monostable multi 4b, and the monostable multi 7b. That is, the monostable multi 4b is configured to send out a pulse signal of a constant width each time the output of the integrating circuit 3 reaches a predetermined level. The monostable multi 7b outputs a pulse having a width ts2 at each rising timing of the monostable multi 4b. The oscillation circuit 8 continues to oscillate at a predetermined high frequency during the period of width ts2, and the oscillation output is power amplified by the next stage driver 9 for driving the transducer 1. In this way, a superordinate wave pulse A2 having a width ts2 is transmitted from the transducer 1 in a predetermined pointing direction.

The switching circuit 18 switches each of the circuits described above to operate alternately, so that detection pulses of pulse widths tsl and ts2 are alternately and repeatedly transmitted.

Furthermore, the gates 5a and 5b are monostable multi-channels 4a and 4b, respectively.
It operates in response to a pulse signal from gate 5.
The gate a outputs a pulse signal from a time later than the time t2 to the time t3, while the gate 5b outputs a pulse signal from a time earlier than the time t2 to the time t3.

In this way, the received signal # (FIG. 6b) based on the transmitted detection pulse A1A2 is amplified and detected by the amplifier circuit 10 and the next stage detection circuit 11, and then sent to the level detection circuit 12. Level detection is performed.

In the case of reception based on the detection pulse A1, since the pulse width is long, the time t11 at which the remaining pulse reaches the predetermined level Vs is delayed. The memory 13 receives the detection signal sent out at this time and outputs a signal that turns on the gate 5a. As a result, the gate 5a receives a pulse (
01) in FIG. 6, and the integrating circuit 14 is operated during this period.

On the other hand, in the case of reception based on the detection pulse A2, since the pulse width is short, the time t12 at which the reverberation reaches the predetermined level Vs is earlier. The memory 13 receives the detection signal sent out at this time and outputs a signal that turns on the gate 5a. As a result,
The gate 5a outputs a pulse (C2 in FIG. 6) that lasts from time t12 to t3, during which time the integration circuit 14 is operated.

According to this second embodiment, by using a long width ts1 transmission pulse with large transmission energy, it is possible to detect even a short person such as a child rather than a short distance including reverberation. To suppress the duration of reverberation as much as possible by transmitting pulses with a small short width ts2 to detect a person at a short distance rather than a long distance, that is, a tall person, and to perform such detection alternately. This makes it possible to reliably detect both near and far distances while compensating for the shortcomings of both.

Next, FIG. 7 is a circuit diagram showing a third embodiment of the present invention.

In summary, in this embodiment, within a period including reverberation immediately after two consecutive transmissions, an object is detected when the output of the detection circuit 11 drops to a predetermined level Vs or when a large change occurs in the waveform itself. It was decided that
This will be explained below with reference to FIGS. 7 and 8.

Note that in the figure, the same numbers as in FIG. 1 indicate the same items.

In the figure, the generation, transmission, and amplification/detection of the detection pulse (FIG. 8a) are the same as in FIG. 1, so a description thereof will be omitted.

The gate 19 operates based on the output signal of the monostable multi-4 from time 15 immediately after transmission to time t0, which can be considered as the duration of reverberation.
It outputs pulses for up to 2 seconds. On the other hand, gate 5 also receives to2 based on the output signal of monostable multi 4.
A pulse is output from the time point to the time point t3. That is, the gate 19 checks the signal state immediately after transmission, and the gate 5 thereafter detects the signal up to a predetermined distance.

The memory 13a takes in the detection signal from the level detection circuit 12a while the output signal of the gate 19 is being sent out, and measures the time. Further, the memory 13a is stored at the time of acquisition of the previous detection signal (E1 in FIG. 8).
M) is stored, and at the time when the current detection signal is taken in (FIG. 8, E2, tlo), the time measurement data at both times of taking in are output to the comparison circuit 20.

The comparator circuit 20 compares both inputted clock data, and outputs a signal if the current clock data is greater than the previous clock data by a predetermined time tK (tl"≧tI+tK). The above t is set to such a time that it can be determined that the time required for the apparent upper reverberation to drop to level VB suddenly increases and that the signal from the target object is mixed in the reverberation.

The monostable multi 21 outputs a pulse signal to the self-holding circuit 22 immediately upon receiving the signal from the comparison circuit 20.

On the other hand, the level detection circuit 12a is configured to allow the detected signal to pass through the gate 5 for a predetermined period (D1 in FIG.
It is designed to be output to .

The self-holding circuit 22 operates during the first half (eighth period) of the reception period after transmission.
Figure 01) accepts the pulse signal from the monostable multi 21, and the latter half (D1 in Figure 8) accepts the received signal from the level detection circuit 12a, and within these two periods, a signal is input manually from at least one side. A signal is output for a predetermined period of time.

This time is set to be a suitable time to keep an automatic door open when a target is detected, for example.

The switching circuit 16 operates the relay 17 while the self-holding circuit 22 sends out an output.

The operation of the above circuit configuration will now be described using the time chart of FIG.

The reflected wave B1 received based on the transmission of the detection pulse A1 with a width ts is amplified and detected, and then sent to the level detection circuit 12a.
guided by. This detected signal E1 is only a reverberation in the example of FIG.

The level detection circuit 12a first detects the reverberation level in the first half C1 of the wave receiving period, and at the time t1 when the level drops to Vs.
Sends out a detection signal. When the memory 13a receives this detection signal, it sends the data at the previous generation point and the current generation point of the detection signal to the comparison circuit 20, and it is compared to see if the difference is greater than or equal to tK. If it is less than tK, the comparator circuit 20 does not send out an equivalent output. And from sending t
After time 02, the reflected wave from the target object is detected during the period of signal D2. In the example of FIG. 8, there is no target signal.

After a certain period of time, the next cycle of detection pulses is transmitted, and the reflected wave B2 received based on the transmission of this detection pulse is amplified.
The signal is detected and guided to the level detection circuit 12a. In the example shown in FIG. 8, the detected signal E2 includes a mixture of reverberation and a target signal. The level detection circuit 12a sends out a detection signal at time t1', and the memory 13a sends the previous data t1 and the current data t1° to the comparison circuit 20. In this case, t1' has a difference of more than tK compared to tl, so
It determines that there is a target signal and sends out an output signal. As a result, the self-holding circuit 22 outputs a signal with a constant width to operate the switching circuit 16 immediately after the target object is detected (FIG. 8f).
During this time, the relay 17 operates to open an automatic door or the like.

In this embodiment, the level detection circuit 12a detects only the point in time when the level Vs decreases, but it is designed to detect the reverberation level itself and also detect when the level changes significantly. It's okay. in this case,
The memory 13a samples the detection output at high speed, and the comparing circuit 20 compares the levels of the previous sampling data and the current sampling data. This comparison may be performed, for example, by integrating level differences between corresponding sampling data, and determining whether the value is greater than or equal to a predetermined value.

According to the third embodiment, it is possible to detect even when the reverberation level or duration changes significantly due to the presence of a target signal in the reverberation.

Next, FIG. 9 is a circuit diagram showing a fourth embodiment of the present invention.

In summary, this embodiment is a system in which a reflector is attached to a transducer and the target is detected by causing multiple reflections between the transducer and the target. This will be explained with reference to FIG.

Note that in the figure, the same numbers as in FIG. 1 indicate the same items.

In FIG. 9, the generation, transmission, and amplification/detection of the detection pulse (FIG. 10a) are the same as in FIG. 1, so their explanation will be omitted. Note that the level detection circuit 12b extracts only signals above a certain level and removes low-level noise signals and the like.

FIG. 12 shows the structure of a wave transmitting/receiving section including the ultrasonic wave transmitting/receiving device 1 according to this embodiment. The reflecting plate 1a is attached so as to surround the transducer 1, and is formed into a parabolic shape, for example, in order to improve the focusing efficiency of sound waves. The blind mounting bracket 1b is a member for attaching the wave transmitting/receiving section to a blind position of the door C.

FIG. 11 is a diagram showing the state of multiple reflections of ultrasonic waves by the transducer. As shown in the figure, the ultrasonic waves transmitted from the transducer 1 are repeatedly reflected between the target object, which is the human head F, and as a result, the ultrasonic waves transmitted from the transducer 1 are reflected from the same target object. The wave signal is received multiple times at regular intervals (see Figure 10).

In the above configuration, the operation will be explained below using the time chart of FIG. 10.

When the detection pulse A1 is transmitted, the reverberation B occurs immediately after it.
1 appears, and a reflected wave B2 from the target object is obtained following the remaining uB1. This reflected wave B2 is further reflected by the reflecting plate 1a and transmitted again toward the target object. The target receives this second sound wave pulse and reflects it again, producing a secondary echo B.
It is received as 3. After that, this multiple reflection is repeated,
Within the receiving sensitivity level of the transducer 1, the waves are sequentially received as a third-order echo 84 and a fourth-order echo B5. In this case, since the residual WBt occurs only immediately after transmission, even if the first reflected wave B2 is mixed in the reverberation, the secondary echo and the tertiary echo will appear after the reverberation duration.

The detected reverberation D1 and multiple echoes D2 to D4 are extracted by the level detection circuit 12b and guided to the integration circuit 14. The integration circuit 14 is opened by the gate pulse C1 from the gate 5 from time to3 to time t3. Therefore, the free tube flop 15 is operated by the first signal D3 obtained immediately after the above-mentioned time t03. As a result, the switching circuit 16 outputs a signal e to operate the relay 17 to open an automatic door or the like.

According to this fourth embodiment, a reflector is attached to the transducer to cause multiple reflections, and by receiving the multiple reflections, the target object that appears within the duration of the reverberation is affected by the reverberation. It is possible to accurately detect the period when there is no

〔Effect of the invention〕

As explained above, according to the present invention, the gate is turned on at the same time as the reverberation level immediately after transmission drops to a predetermined level, so the duration of reverberation is relatively variable due to the influence of temperature, etc. However, the wave reception operation can always be started immediately after the reverberation disappears, and it is possible to sufficiently detect targets at short distances.

Furthermore, since the gate is forcibly turned on after a predetermined time has elapsed since the wave was transmitted, the start of detection will not be significantly delayed even if the duration of reverberation varies greatly.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a time chart when the reverberation is within time t2, that is, the gate 5 is turned on from time t1, and FIG. 3 is a time chart when the reverberation is at or above t2, that is, A time chart when the gate 5 is turned on from t2, FIG. 4 is a diagram showing an example of a human body detector for an automatic door, FIG. 5 is a circuit diagram showing the second embodiment of the present invention, and FIG. 5 is a time chart for explaining the operation of the circuit diagram shown in FIG. 5, FIG. 7 is a circuit diagram for explaining the third embodiment of the present invention, FIG. 8 is a time chart for explaining the operation of the circuit diagram shown in FIG. 7, FIG. 9 is a circuit diagram showing a fourth embodiment of the present invention;
The figure is a time chart explaining the operation of the circuit diagram shown in FIG. 9, FIG. 11 is a diagram showing the state of multiple reflection of ultrasonic waves by the transducer, and FIG. 12 is an ultrasonic wave according to the fourth embodiment. 1 is a structural diagram of a wave transmitting/receiving section including a wave transmitting/receiving device 1. FIG. 1... Ultrasonic transducer, 5... Gate, 12...
Level detection circuit, 13...Memory, 14...Integrator circuit, 15...Flipflop, 17...Relay

Claims (1)

[Claims] 1. Repeatedly transmit sonic pulses with an ultrasonic transducer,
In an ultrasonic detector that detects the presence or absence of reflected waves from a target object by turning on a gate and receiving waves after a predetermined time elapses from the transmission of the waves, the reverberation level immediately after the transmission of the waves is detected and the reverberation level is determined. 1. An ultrasonic detector comprising: a level detecting means for detecting that the level has decreased to a predetermined level; and a gate controlling means for turning on the gate when the output of the level detecting means is output.