JP2000082186A - Active mobile object detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive and simple active mobile object detecting device capable of detecting a mobile object. SOLUTION: This device is provided with a transmission source 2 for transmitting a detection wave, a first oscillation circuit 3 for oscillating an electric signal S1 with first frequencies, a modulation driving circuit 4 for driving the transmission source 2 for transmitting a detection wave W1 modulated by the electric signal S1 oscillated by the first oscillation circuit 3, a reception circuit 5 for receiving a reflection wave W2 obtained when the modulated detection wave W1 is reflected on an object, and for converting this into an electric signal S2, a demodulation circuit 6 for demodulating the converted electric signal S2, a second oscillation circuit 7 for oscillating an electric signal S4 with second frequencies in the neighborhood of the first frequencies, a mixing circuit 9 for mixing a demodulated electric signal S3 with the electric signal S4 with a second frequencies, a low pass filter 11 for removing high frequencies from a signal S6 generated by the mixing circuit 9 and extracting a signal S8 with low frequencies almost equal to a difference between the first frequencies and the second frequencies, and a phase change detecting means 13 for detecting the phase change of the signal S8 with the low frequencies, and for detecting the presence of a mobile object.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active type moving object detecting apparatus for transmitting a modulated detection wave and detecting the presence of a moving object based on a change in phase of the detection wave reflected by the object. (Hereinafter, it may be simply referred to as “detection device”.)

[0002]

2. Description of the Related Art As a device for detecting the presence of a moving object such as an intruder, an active moving object detecting device 1 shown in FIGS. 4A and 4B is known. In FIG. 4A, the detection device 1 emits a detection wave W1 such as near-infrared light, and receives a reflection wave W2 reflected by a stationary object M1 such as a wall or a floor. As shown in FIG. 4B, when the moving object M2 is present, the detection wave W1 transmitted by the detecting device 1 is reflected by the moving object M2, and the detecting device 1 receives the reflected wave W2.

FIG. 5 shows an example of the configuration of this conventional active moving object detection device. The detection device 1 includes a first transmission source 2 that transmits a detection wave W1, a second transmission source 102 that transmits a zero-adjustment signal wave W3 of the device, and a first oscillation that oscillates an electric signal of a first frequency. The circuit 3 is provided. Detection device 1
Includes a signal selection circuit 100, a first modulation driving circuit 4, and a second modulation driving circuit 104. The signal selection circuit 100 inputs the electric signal S1 oscillated by the first oscillation circuit 3 to each of the first and second modulation driving circuits 4 and 104, and each of the modulation driving circuits 4 and 104 outputs the first oscillation signal. The detection wave W1 modulated by the electric signal S1 oscillated by the circuit 3 is transmitted from each of the first transmission source 2 and the second transmission source 102.

The modulated detection wave W1 transmitted from the first transmission source 2 is reflected by a stationary object M1 (FIG. 4 (a)) or a moving object M2 (FIG. 4 (b)).
2 is received by the receiving circuit 5 and converted into an electric signal S2. The electric signal S2 is demodulated by the demodulation circuit 6, and the electric signal S3 is extracted.

In the first transmission source 2, the first modulation drive circuit 4, the reception circuit 5, etc., the signal is delayed. Therefore, in order to obtain the absolute distance between the sensing device and the object, it is necessary to use the delayed signal as a reference. Therefore, the zero adjustment signal wave W3 of the modulated device transmitted from the second transmission source 102 is received. The light enters the circuit 5. The electric signal S2 output from the receiving circuit 5 is based on the signal wave W3.

[0006] The detecting device 1 further oscillates an electric signal of a second frequency near the first frequency from the second oscillating circuit 7. The mixing circuit 9 mixes the electric signal S3 demodulated and extracted with the electric signal S4 oscillated by the second oscillation circuit 7 to generate an electric signal S6. Here, the mixing circuit is a circuit that generates an electric signal having a frequency equal to the sum or difference of the input electric signals. The electric signal S6 is filtered by the low-pass filter 11 to remove harmonics,
An electric signal S8 having a low frequency substantially equal to the difference between the frequency and the second frequency is extracted.

If the output signal of the mixing circuit when there is no phase difference between the two electric signals input to the mixing circuit is used as a reference signal, the output signal of the mixing circuit is
It has the characteristic that the phase advances with respect to this reference signal by the phase difference between two input electric signals. Therefore, S
If there is no phase difference between 3 and S4, that is, if the distance from the detection device 1 to the object is 0, the absolute distance from the detection device 1 to the object is determined by the phase difference between S3 and S4. Can be derived.

The electric signal S8 is shown in FIG.
As shown in (b) and (c), both are square waves with a fixed period. As described above, since the case where the distance from the detection device 1 to the object is 0 is the reference signal, the phase shift of the electric signal S8 from the case where the distance from the detection device 1 to the object is 0 is different from that of the detection device 1. It is almost proportional to the distance between the object and the object that reflects the detection wave W1. Specifically, when the detection wave is reflected by the stationary object M1 as shown in FIG. 4A, as shown in FIG. 6B, the electric signal S8 in this case and the signal from the detection device 1 to the object are output. The time shift Δt1 indicating the phase shift from the electric signal 8 (FIG. 6A) when the distance is 0 is almost equal to 2 × D1, which is twice the distance D1 between the detection device 1 and the stationary object M1. Proportional. On the other hand, when the detection wave is reflected by the moving object M2 as shown in FIG. 4B, the electric signal S8 in this case and the distance from the detection device 1 to the object are 0 as shown in FIG. In this case, the time shift Δt2 indicating the phase shift from the electric signal (FIG. 6A) is substantially proportional to 2 × D2 which is twice the distance D2 between the detection device 1 and the object M2. Although the direction of the detection wave W1 and the direction of the reflection wave W2 are different from each other by the angle θ1 or the angle θ2, the distances D1, D
Since 2 is large, it can be considered that θ1 ≒ 0 and θ2 ≒ 0.

The phase difference detecting means 12 shown in FIG. 5 detects the time lag Δt1 or Δt2 to calculate the absolute distance between the moving object detecting device 1 and the stationary object M1 or the moving object M2. When the time difference becomes a value different from Δt1, it is determined that there is a moving object that blocks between the stationary object M1 and the detection device 1. When the phase difference detecting means 12 determines that a moving object exists, a signal is sent to the alarm output circuit 20.

The moving object detecting apparatus 1 shown in FIG. 5 has a different configuration from the moving object detecting apparatus 1 and does not include the second transmitting source 102.
A device for injecting the zero-adjustment signal wave W3 into the receiving circuit 5 is also generally used.

[0011]

However, the measurement of the absolute distance requires a transmission source for transmitting a zero-adjustment signal wave of the device and an internal path inductor as described above. However, there is a problem that the device becomes complicated.

In addition to the above-described devices, there are distance measurement using the principle of triangulation and distance measurement by measuring the amount of light reflected from an object. A moving object can be detected by these distance measurements, but in any case, it is necessary to increase the accuracy of the device in order to accurately measure the distance, and the problem of increased cost is inevitable.

Furthermore, in distance measurement by measuring the amount of light reflected from an object, the change in distance cannot be measured correctly because the amount of reflected light changes depending on the brightness of the object reflecting the light beam, that is, whether the object is black or white. There is a problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide an active moving object detecting device which can detect a moving object while being inexpensive and simple.

[0015]

In order to achieve the above object, an active moving object detection device according to the present invention comprises a transmission source for transmitting a detection wave, and a first oscillation device for oscillating an electric signal of a first frequency. A circuit, a modulation driving circuit for driving the transmission source to transmit a detection wave modulated by the electric signal oscillated by the first oscillation circuit, and a reflected wave obtained by reflecting the modulated detection wave on an object. A receiving circuit for receiving and converting the converted electric signal; a demodulating circuit for demodulating the converted electric signal;
A second oscillation circuit that oscillates an electric signal of a second frequency near the frequency, a mixing circuit that mixes the demodulated electric signal with the electric signal of the second frequency, and a signal generated by the mixing circuit. A low-pass filter that removes harmonics and extracts a low-frequency signal substantially equal to the difference between the first frequency and the second frequency; and a phase change that detects a phase change of the low-frequency signal and detects the presence of a moving object. Detecting means.

According to this configuration, since the presence of the moving object can be detected by detecting that the phase of the signal has changed, it is not necessary to measure the absolute distance between the detecting device and the object. Therefore, since a transmission source for transmitting a zero-adjustment signal wave of the device or an internal path inductor is not required, the detection of a moving object can be realized with an inexpensive and simple device.

In a preferred embodiment of the active moving object detection device according to the present invention, the phase change is a change in rising of the low frequency signal. According to this configuration, it is only necessary to detect that the rise of the low-frequency signal substantially equal to the difference between the first frequency and the second frequency changes from the steady state. Can be detected.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, an active moving object detecting device 1 of the present invention includes a transmission source 2, a first oscillation circuit 3, a modulation driving circuit 4, It includes a reception circuit 5, a demodulation circuit 6, a second oscillation circuit 7, a mixing circuit 9, and a low-pass filter 11, but includes a second modulation drive circuit 104 (FIG. 5) and a second transmission source 102 (FIG. 5). This is different from the conventional active moving object detection device in that it is not provided.

The electric signal S1 output from the first oscillation circuit 3
Is a first frequency, for example, a high frequency of about 10 MHz. The detection wave transmitted by the transmission source 2 is in the range from near infrared to visible light, and the modulation drive circuit 4 transmits the detection wave W1 modulated by the electric signal S1. Compared with microwave detection waves, detection waves in the range from near-infrared rays to visible light can be transmitted as spots, so that there is an advantage that the detection area is clear. The reflected wave W2 received by the receiving circuit 5 is converted into an electric signal S2, and the electric signal S3 demodulated and extracted by the demodulation circuit 6 has the first frequency equal to the electric signal S1.
Since the active moving object detection device 1 of the present invention does not measure the absolute distance from the detection device 1 to the object, the zero adjustment signal wave W3 of the device as shown in the conventional example of FIG. 5 is not required.

The second oscillation circuit 7 outputs an electric signal S4 near the electric signal S1, for example, a signal having a second frequency of 10.001 MHz. The mixing circuit 9 outputs the electric signal S3
And the electric signal S4 are mixed to generate an electric signal S6.
The electric signal S6 is filtered by the low-pass filter 11 to remove harmonics, and becomes an electric signal S8 having a frequency substantially equal to the difference between the first frequency and the second frequency, for example, about 1 kHz.

The electric signal S8 is shown in FIGS. 2 (a) and 2 (b).
As shown in FIG. FIG. 2 (a)
4A, when the detection wave W1 is reflected by the stationary object M1 as shown in FIG.
FIG. 2B shows an electric signal S8 whose phase is shifted by a magnitude substantially proportional to the detection signal W1 reflected by the moving object M2 as shown in FIG. An electric signal S8 whose phase is shifted from the signal by a magnitude almost proportional to the distance D2 is shown. As shown in FIG. 1, the phase change detection means 13 has a counter circuit 14, a storage circuit 15, and an arithmetic circuit 16, and detects a phase change of the electric signal S8 by these.

The counter circuit 14 counts the period or timing of the input square wave. When the electric signal S8 shown in FIG.
The rising of the square wave A1 is inspected. Thereby, the period T1 of the electric signal S8 can be obtained. This cycle T
1 is stored in the storage circuit 15. Here, time ta
When the moving object M2 blocks between the detection device 1 and the stationary object M1 as shown in FIG. 4B, and the reflected wave W1 is reflected by the moving object M2, the phase of the electric signal S8 becomes as shown in FIG. (B)
It changes like Therefore, as shown in FIG. 2 (c), the square wave that should rise at time ta in the period T1 has a delayed rise like the square wave A3 and the time tb
And the time interval of the rise of the square wave A3 is T
It becomes 2.

FIG. 3 shows a method by which the arithmetic circuit 16 determines that the phase has changed. First, as described above, the counter circuit 14 obtains a period from the timing at which the rise of the square wave is inspected (S1). Next, the obtained cycle is stored as the "current cycle" (S3), but before that, the value already stored in the "current cycle" is stored in the "previous cycle" (S2). ). Specifically, when the moving object appears and becomes the period T2 when the period T1 when the moving object does not exist is stored in the “current period”, the current period is the “last period”. T1 is set (S2), and the "current cycle" is set to T2 which is the cycle derived in S1 (S3). Next, the arithmetic circuit 16
The current cycle T2 is compared with the previous cycle T1, and if the difference is equal to or greater than a predetermined value, it is determined that a moving object is present (S4). That is, it is determined that | T2−T1 | ≧ C (predetermined value).

When the arithmetic unit 16 determines that a moving object exists, it sends a signal to the alarm output circuit 20 (S5). Appropriate measures such as notification from the alarm output circuit 20 to a security company are taken.

Since the intruder is located at a distance from the stationary object to some extent, if the difference between the current cycle T2 and the previous cycle T1 is not more than the predetermined value C, it is determined that a moving object exists. do not do. As described above, by detecting only when there is a change in the predetermined distance, the phase change of the electric signal due to the temperature change of the moving object detection device 1 immediately after the power is turned on and the temperature around the device is not detected. Malfunction of the device can be prevented.

By the above method, without measuring the distance between the moving object detection device and the stationary object or the moving object,
A moving object can be detected. As described above, the moving object detection device does not measure the absolute distance from the device to the object, and thus does not require a transmission source for transmitting a zero-adjustment signal wave of the device or an internal optical path inductor. Therefore, an inexpensive and simple device can be realized.

In the present embodiment, the counter circuit 14 counts the period or timing of the square wave by observing the rise of the square wave, and detects that the phase has changed from the steady state. Therefore, the detection of the presence of the moving object is realized by the simple phase change detecting means 13 including the counter circuit 14, the storage circuit 15, and the arithmetic circuit 16.
On the other hand, the period or timing of the square wave may be counted by observing the falling edge of the square wave.

[0028]

As described above, according to the active moving object detecting device of the present invention, the presence of the moving object can be detected by detecting that the phase of the signal has changed. There is no need to measure the typical distance. Therefore, since a transmission source for transmitting a zero-adjustment signal wave of the device or an internal path inductor is not required, the detection of a moving object can be realized with an inexpensive and simple device.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram of an active moving object detection device according to an embodiment of the present invention.

FIGS. 2A to 2C are timing diagrams of electric signals input to a phase change detection unit of the active moving object detection device according to the embodiment of the present invention, and FIG. If not, (b) is when there is a moving object,
(C) is a case where a moving object appears halfway.

FIG. 3 is a flowchart showing processing of an arithmetic circuit 16 of the active moving object detection device according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing the principle of a conventional active moving object detection device.

FIG. 5 is a block circuit diagram of a conventional active moving object detection device.

6 (a) to 6 (c) are timing charts of electric signals of the conventional active moving object detection device, FIG. 6 (a) is a timing chart of reference electric signals, and FIG. FIG. 8C is a timing chart of an electric signal input to the phase difference detecting means when no moving object is present, and FIG. 9C is a timing chart of an electric signal input to the phase difference detecting means when a moving object is present.

[Description of Signs] 1 Active moving object detection device 2 Transmission source 3 First oscillation circuit 4 Modulation drive circuit 5 Reception circuit 6 Demodulation circuit 7 Second oscillation circuit , 9 ... mixing circuit, 11
... low-pass filter, 13 ... phase change detecting means, S8 ...
Low frequency signal.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroyuki Amano 4-7-5 Nonohama, Otsu-shi, Shiga F-term in Optex Co., Ltd. (Reference) 5C084 AA02 AA04 AA08 BB24 CC16 DD07 GG38 GG44 GG71 GG74 5C086 AA22 AA27 BA01 CA06 EA17 EA25 EA32

Claims (2)

[Claims] 1. A transmission source for transmitting a detection wave, a first oscillation circuit for oscillating an electric signal of a first frequency, and a modulation of an electric signal generated by the first oscillation circuit by driving the transmission source. A modulation driving circuit for transmitting the detected detection wave, a receiving circuit for receiving the reflected detection wave reflected from the object and converting the reflected detection wave into an electric signal, and a demodulation circuit for demodulating the converted electric signal A second oscillation circuit that oscillates an electric signal of a second frequency near the first frequency; a mixing circuit that mixes the demodulated electric signal with the electric signal of the second frequency; A low-pass filter that removes harmonics from the generated signal to extract a low-frequency signal that is substantially equal to the difference between the first frequency and the second frequency; and detects a phase change of the low-frequency signal to detect the presence of a moving object. Detect Active moving object detection apparatus that includes a phase change detection means that. 2. The active moving object detection device according to claim 1, wherein the phase change is a change in rising of the low-frequency signal.