JPS6276467A - Moving speed detector for moving body by using pyroelectric sensor - Google Patents

Abstract

PURPOSE:To improve responsiveness with a comparatively simple constitution, to detect the speed of a quickly moving body and to minimize a speed detection error by detecting the speed of the moving body from two difference signal obtained by using four pyroelectric sensors. CONSTITUTION:The pyroelectric sensors 1a-1d output detection signals S1-S4 accompanied with time delay according to the moving speed of an incident infrared ray in the incident order. The detecting signals S1 and S2 are given to a differential amplifier circuit 3a through impedance conversion circuits 2a and 2b to output a difference signal S5. On the other hand, a differential amplifier circuit 3b given with detection signals S3 and S4 through impedance conversion circuits 2c and 2d outputs a differential signal S6 slightly after the differential signal S5 in terms of hour. Since the rise of the peak part of the differential output is extremely quick in order to take a difference between sharply changing parts of the pyroelectric sensors 1a-1d even if the rises of the detection signals S1-S4 are slow, the difference signals S5 and S6 can obtain a sufficiently large difference output even if a speedily moving body is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a device for detecting the moving speed of a moving object, and particularly relates to a device for detecting the moving speed of a moving object using a pyroelectric optical sensor. .

(Prior Art) Consider the following moving speed detection device using a pyroelectric sensor. That is, two pyroelectric sensors A and B are arranged along the direction of movement of a moving object, and both the pyroelectric sensors receive infrared rays from the moving object to perform detection as shown in FIG. Signals Sa and Sb are output in sequence. Next, the time difference TI when these detection signals Sa and Sb each reach a predetermined setting level VO is determined.
be detected. The separation distance between both pyroelectric sensors, which is known in advance, is divided by this time difference TI, and the division result (L
/TI), the speed of the moving object is detected.

(Problems to be Solved by the Invention) However, it is generally known that the response speed of pyroelectric optical sensors is not very fast.

For this reason, although this type of pyroelectric sensor can be used to detect the moving speed of objects moving at low speed, it is difficult to detect the moving speed of objects moving at high speed. Unable to obtain sufficient sensor output. Therefore, the conventional detection device has a problem in that it is not suitable for detecting the moving speed of a high-speed moving object.

Also, the level V set for speed detection as described above.
If o is set high in accordance with a sufficiently large detection signal, if the pyroelectric sensor outputs a small detection signal, this will not be detected. Therefore, the conventional detection device has the trouble of having to change the level setting value according to the magnitude of the detection signal of the jQ electric type sensor.

Furthermore, if there are variations in the sensitivity and response speed of the pyroelectric sensors, the rise time of the detection signal of each sensor will be different, resulting in a problem of poor speed detection accuracy. For example, because the sensitivity of one sensor is low, a low level detection signal Sb° as shown in FIG. 4(B) is generated.
Suppose that is output. At this time, rain detection signal 5aSSb'
The time difference T2 until the output voltage reaches the set level Vo is longer than the time difference T1 when the detection signals Sa and Sb of the same level are output. Therefore, the accuracy of speed detection deteriorates. If an attempt is made to solve the influence of such variations in sensor characteristic values on speed detection using known means, the circuit configuration of the detection device will become extremely complex.

The present invention was made in view of the above circumstances, and is capable of not only detecting the moving speed of objects moving at low speed, but also detecting the moving speed of objects moving at low speed.
It is an object of the present invention to make it possible to reliably detect the moving speed of an object moving at high speed.

Furthermore, it is an object of the present invention to easily reduce the error in detecting the speed due to variations in sensitivity and response speed between the pyroelectric sensors.

(Means for Solving the Problems) In order to achieve the above object, the present invention outputs a detection signal in response to light from a moving object within the Sennonk area, and Four pyroelectric sensors are arranged in a line at predetermined intervals along the direction of movement of a moving object, and two of the pyroelectric sensors (1:, pyroelectric sensors are individually provided from the pyroelectric sensors). In response to the two detection signals, a differential signal is output or in response to two detection signals obtained from the first differential signal output means and the other two pyroelectric processors individually, a second differential signal output means for outputting a differential signal, a signal processing means for detecting a time difference between the two differential signals, a time difference between the differential signals and a separation distance between the pyroelectric sensors; Based on the above, the present invention is characterized by comprising a margin calculation processing means for calculating the moving speed of a moving object.

(Function) Depending on the moving direction of the moving object, a time lag occurs in the output of each pyroelectric sensor. As a result, each of the differential signal output means provides a differential signal. When the time difference between the two differential signals is detected, the arithmetic processing means calculates the moving speed of the moving object based on this time difference and a previously known separation distance between the two sets of pyroelectric sensors. .

On the other hand, since the differential signal output means provides a differential output of a sharply changing portion of the detection signal of the pyroelectric sensor, it is possible to magnify and extract changes in the sensor output. As a result, the response speed of this detection device is defeated, and the moving speed of a relatively high-speed moving object can be detected.
Errors in speed detection due to variations in sensitivity and response time of each pyroelectric sensor are significantly reduced.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings. FIG. 1 is a circuit diagram schematically showing the configuration of a moving speed detecting device that also serves to detect the moving direction of a moving object, using a pyroelectric sensor according to an embodiment of the present invention.

The pyroelectric sensors 1a to 1d of this embodiment each have a sensing area that detects infrared rays from within a certain range. The pyroelectric sensors 1a-1d are integrally formed as a sensor element 20, as shown in FIG. This sensor element 20 has a structure in which infrared light receiving sections 22a to 22d are arranged on a pyroelectric substrate 21 at a certain distance apart and substantially parallel to the moving direction. These infrared light receiving parts 22a to 22d are the pyroelectric sensor 1.
It corresponds to a -1d. The pyroelectric substrate 21 is made of, for example, a pyroelectric material such as PbZr03-PbZr03 (PZT)-based solid solution porcelain. One end of the extraction electrodes 23a to 23d is connected to each of the infrared light receiving sections 22a to 22d, respectively. Drawer type! The other ends of 23a to 23d are respectively connected to impedance conversion circuits 2a to 23d, which will be described later.
External connection terminals 24a to 2 should be connected to each human power 1< of 2d.
・Terminates with 1 (].

Such pyroelectric sensors 1a to 1d are equipped with an impedance conversion circuit 2a composed of a field effect transistor or the like.
~2d, the negative (-) of the differential amplifier circuits 3a, 3b.
Connected to each positive (+) input terminal. Each output terminal of the differential amplifier circuits 3a, 3b is connected to an l mixer 4 via a DC blocking capacitor C. The mixer 4 is connected to a polarity determining circuit 5 and a waveform shaping circuit 6. The waveform shaping circuit 6 is connected to a trigger circuit 7, which is further connected to one input terminal of a counting circuit 8. An oscillation circuit 9 is connected to the other input terminal of the counting circuit 8. The output side of this counting circuit 8 is connected to an arithmetic processing circuit 10. The arithmetic processing circuit 10 is connected to a drive circuit 11 that drives a moving direction/speed indicator 12. Further, the output side of the polarity determining circuit 5 is connected to this drive circuit 11. Note that since the outputs of the polarity discrimination circuit 5 and the arithmetic processing circuit 10 can themselves detect the moving direction and speed of the moving object, the drive circuit 11 and the display 12 are not necessarily essential elements of the present invention.

In addition, on the front of the pyroelectric sensor la-1d, there is a
Attach the imaging lens 100 as shown in A),
If a method such as image formation by reflection by a concave mirror 101 as shown in FIG. 2B is used, it is possible to detect the moving direction and speed of an object located at a distance from the sensor. In addition,
In FIG. 5, 102 indicates a sensor receiving surface.

Next, the operation of this embodiment will be explained.

For example, suppose that a moving object is moving from the pyroelectric sensor 1a toward the pyroelectric sensor Id. Jiao 7u Aya Senza la ~ 1d is,
As shown in FIG. 3(A), detection signals 5t-54 with a time delay depending on the moving speed of the incident infrared rays are output in the order in which the infrared rays are incident.

The detection signals Sl and S2 are provided by the impedance conversion circuit 2a,
2b to the differential amplifier circuit 3a. As a result, the differential amplifier circuit 3a outputs a differential signal S5 as shown in FIG. On the other hand, the differential amplifier circuit 3b to which the detection signals S3 and S4 are applied via the impedance conversion circuit 2C12d is delayed by a few thousand hours from the differential signal S5, as shown in FIG. Differential signal S6
Output. These differential signals S5 and S6 are individually applied to the mixer 4 via DC blocking capacitors CI and C2, respectively. The mixer 4 receives the differential signals S5 and S6.
are synthesized to output a composite signal S7 as shown in FIG. This composite signal S7 is sent to the polarity determining circuit 5 in the next stage.
and the waveform shaping circuit 6.

Combined signal S7! The polarity determining circuit 5 determines the moving direction of the moving object by determining the positive or negative polarity of this signal. For example, as mentioned above, if the moving object is j,! When moving in the direction from the +electroelectric sensor Ia toward the pyroelectric sensor 1d, the polarity of the composite signal S7 is set to be positive. Then, when the moving object moves in the opposite direction to the above direction, the detection signal S2 becomes the detection signal S1.
Since the differential signals are outputted first, the polarity of the signal S7, which is a composite of these differential signals, becomes negative as shown in FIG. 1(E). In this way, the moving direction of the moving object can be determined based on the polarity of the composite signal S7. Then, the polarity discrimination circuit 5 outputs the discrimination result to the drive circuit 11, so that the moving direction of the moving object is displayed on the display 12.

On the other hand, the waveform shaping circuit 6 supplied with the composite signal S7 from the mixer 4 converts it into a rectangular pulse S as shown in FIG.
Shape the waveform to 8. This rectangular pulse S8 is given to the trigger circuit 7, and a pulse signal S9 as shown in FIG.
is converted to The pulse width of this pulse signal S9 is equal to the time difference between the two differential signals included in the composite signal S7, that is, −
A set of pyroelectric sensors Ia and Ib to another set of pyroelectric sensors lc.

The distance to Id (corresponding to the distance of two pitches of the arrangement pitch of the light receiving sections shown in FIG. 2) corresponds to the time it takes for the incident infrared rays to travel 13 lines. The transit time of this incident infrared rays corresponds to the travel time of the moving object.

Such a pulse signal S9 is given to the counting circuit 8 as a manual input. Since the lock pulse SlO is given as the other input of the counting circuit 8 from the oscillation circuit 9 as shown in FIG. By doing this, a count value corresponding to the travel time of the moving object can be obtained.

The arithmetic processing circuit 10 multiplies the count value by the period of one clock pulse to obtain the pulse width T of the pulse signal S9.
Calculate. And, the second problem of the arrangement pinch of the light receiving part mentioned above.
By dividing the distance corresponding to the pitch by the pulse width T, the moving speed of the infrared rays passing through the pyroelectric sensors 1a to 1d can be determined.

Then, the moving speed of the moving object is determined from the moving speed of the incident infrared rays. This speed calculation result, drive circuit 1
1, the speed of the moving object is displayed on the display 12. Note that when a lens or a concave mirror as shown in FIG. 5 is used, the actual speed of the moving object and the speed on the sensor light receiving section are different, so further arithmetic processing may be performed.

By the way, as can be understood from the waveform diagrams shown in FIGS. 2(A) to 2(C), the differential signals S5 and S6 are the difference between the steep change portions of the detection signals of the pyroelectric sensor Ia=ld. Even if the rise of each of the detection signals 81 to S4 is slow, the rise of the peak portion of the differential output is extremely fast. Therefore, when detecting a high-speed moving object, it is possible to obtain a sufficiently large differential output, so it is not only possible to detect the direction and speed of a low-speed moving object, but also to detect the direction and speed of a high-speed moving object. Detection should also be carried out reliably. In addition, even if there are variations in the sensitivity and response speed of each pyroelectric sensor, it does not significantly affect the time difference between the two differential signals, allowing highly accurate speed detection. You can do something.

In the embodiment, a positive voltage signal from the polarity discrimination circuit 5 hints that the moving object will move from the ear 4 electric sensor Ia to the pyroelectric sensor Id, and a negative voltage signal means the opposite. Did you consider that the moving object moves in the direction of ? This should be the opposite relationship.

Further, in the embodiment, the moving direction of the moving object is detected based on the polarity of the composite signal S7, but this is based on the differential signal S7.
Of course, it can be detected by determining the polarity of at least one of S5 and S6.

Furthermore, in the embodiment, a pyroelectric sensor that generates a voltage of the same polarity with respect to incident infrared rays is used, and a means for obtaining a differential signal of the detection signal of each pyroelectric sensor is used. , a differential amplifier circuit is provided.

However, if the two pyroelectric sensors generate voltages of opposite polarity with respect to incident infrared rays, adder circuits are provided in place of the differential amplifier circuits 3a and 3b, and these It is preferable to obtain differential signals s5 and S6.

Furthermore, in the example, four sensors (two pairs) are arranged, but if more sensors are added, that is, five or more sensors are arranged, it is possible to calculate the average value of the speed. Therefore, it is possible to improve the detection accuracy.

Furthermore, although the pyroelectric sensor according to the present invention is normally used as an infrared sensor, it is also sensitive to visible light, so for example, when a moving object is irradiated with visible light, the reflected light is detected. It's better to do it like that.

(Effects) As mentioned above, the device according to the present invention detects the speed of a moving object using two differential signals obtained using four pyroelectric sensors. The simple configuration improves the responsiveness of the device, makes it possible to detect the speed of a high-speed moving object, and reduces speed detection errors due to variations in sensitivity and response speed of each pyroelectric sensor.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an outline of the configuration of a moving object moving speed detection device using a pyroelectric sensor according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram of a sensor element used in this embodiment. ,
FIG. 3 is an explanatory diagram of the operation of the apparatus shown in FIG. 1, FIG. 4 is an explanatory diagram of speed detection by a conventional detection device, and FIG. 5 is an explanatory diagram of another embodiment of the present invention. la-1d...pyroelectric sensor, 2a-2d...impedance conversion circuit, 3a, 3t+...differential amplifier circuit, 1
・Mixer, 5 Polarity discrimination circuit, 6... Waveform shaping circuit,
7. I-Riga circuit, 8. Counting circuit, 9. Oscillation circuit, 1
0... Arithmetic processing circuit, 11... Drive circuit, +2-fc moving direction/speed indicator.

Claims (3)

[Claims] (1) 4 outputs respective detection signals in response to light from a moving object within the sensing area, and are arranged in a line at predetermined intervals along the moving direction of the moving object.
a first differential signal output that outputs a differential signal in response to the two detection signals individually given from two of the pyroelectric sensors; means, second differential signal output means for outputting a differential signal in response to two detection signals individually given from the other two pyroelectric sensors, and a second differential signal output means for outputting a differential signal; A pyroelectric sensor comprising: a signal processing means for detecting; and an arithmetic processing means for calculating a moving speed of a moving object based on the time difference between the differential signals and the separation distance of the pyroelectric sensor. A device for detecting the moving speed of a moving object using (2) Detection of the moving speed of a moving object using the pyroelectric sensor according to claim 1, which is provided with a condensing lens that focuses only light from within the sensing area onto the pyroelectric sensor. Device. (3) Claim 1 comprising a concave border that focuses only light from within the sensing region onto the pyroelectric sensor.
A device for detecting the moving speed of a moving object using the pyroelectric sensor described in 1.