JPH059755B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that measures the number of people from infrared radiation emitted by a human body, and more specifically, a device that measures the number of people from infrared radiation emitted by a human body, and more specifically, a signal based on infrared radiation from a human target, which is detected by internal radiation of a detection unit or background. This invention relates to a signal processing circuit that separates and detects signals based on infrared radiation from the floor.

For example, it is very effective when it is required to understand the number of people in a given place such as an underground mall, a station, a road intersection, an elevator hall or an escalator entrance, and to know the degree of congestion depending on the situation. As such, the applicant has previously proposed a congestion degree detection device. This congestion detection device uses a scanning mirror to scan at regular intervals, and the width of the output signal waveform of an infrared detection element (hereinafter simply referred to as the detection element refers to the infrared detection element) that responds to changes in incident infrared radiation. The number of people is measured using the relationship that the number of people is proportional to the number of people being measured, and this will be explained below.

FIG. 1 is a diagram for explaining the above-mentioned scanning method, where a shows the object plane scanning method and b shows the image plane scanning method. In FIG. 1, 1 is a scanning mirror, 2 is a condensing lens, 3 is a detection element, 4 is an imaging plane, and 5 is infrared rays emitted from a measurement target.
In object plane scanning (a), the detection element is placed on the optical axis or very close to it, and the mirror is rotated. This method scans by changing the direction of the optical axis by swinging. In this scanning method, the detection element is placed on the optical axis or very close to the optical axis, so the angle of view of the optical system only needs to be small, and good optical performance only needs to be achieved very close to the optical axis. .

However, the scanning mirror needs to have a large aperture, and rotating or swinging it involves various difficulties. On the other hand, the image plane scanning method b is a method in which scanning is performed by moving a detection element arranged on the image plane without changing the direction of the optical axis. In this case, the detection element is actually fixed and the scanning mirror placed after the condensing system is rotated. Due to the oscillation, the focused energy is imaged onto the sensing element. This method requires that the entire target scanning width is focused on the image plane, so it requires an optical system with a wide angle of view, and it is also required to have good optical performance even in areas far from the optical axis. However, since the scanning mirror can be placed close to the image plane, it can be small and the scanning mechanism can be simplified. In principle, the scanning method of this congestion degree detector may be any method, but an example will be described below in which the image plane scanning method is adopted in order to simplify and downsize the mechanism.

Figure 2 shows that a congestion level detection device 10 is installed with an angle of depression on the ceiling of an elevator hall, and a waiting customer 1
3 shows an example of detecting infrared rays 14 emitted from 3. 12 is an elevator car.
FIG. 3 shows the optical system of the congestion level detection device. 11 is an optical system housing case, 15 is a rotary plane mirror (scanning mirror), and its structure is made of synthetic resin (glass etc. may also be used) with aluminum or chromium, which has a high infrared reflectance, deposited on the surface, and a small motor. 1
6 rotates together with the rotating shaft 16a. Reference numeral 17 denotes a synchronization pulse detection section which generates a signal synchronized with rotation by a photointerrupter and sends it to a synchronization circuit to be described later.

Reference numerals 18a to 18e indicate infrared detection elements, in which a plurality of inexpensive pyroelectric detection elements having high quality and stable characteristics are arranged. In order to eliminate the influence of sunlight and illumination light, these elements use window materials (not shown) equipped with cut-on filters that block light with wavelengths of 6 μm or less. 19 is an infrared lens that covers the wavelength range of infrared rays emitted from the human body from 4.5 to 20μ.
It is required to have high transmittance for things with a diameter of m.
Germanium lenses and silicon lenses are suitable for this purpose. The purpose of using this lens is to ensure the operation of the infrared detector by concentrating infrared rays with the lens, increasing the energy density of the element's receiving surface and increasing the output signal. If there is a distance (within a few meters), depending on the application, it may not be necessary to use a lens (the radiant energy density decreases in inverse proportion to the square of the distance). The important points in an optical system like the one shown in Figure 3 are as follows.

(1) The two-dimensional field of view is covered by rotational scanning of the scanning mirror 15 in the x direction and by a plurality of infrared detection elements 18a to 18e arranged in the y direction. Note that the number of detection elements is not limited to five, and may be selected depending on the resolution of the field of view in the y direction and the degree of accuracy required.

(2) Image plane scanning is performed by the scanning mirror 15, and in order to maximize the field of view in the x direction, the lens 19 and the detection elements 18a to 18e are installed closest to the rotating outer edge of the scanning mirror 15. However, compared to the field of view in the y direction (determined by the position of the sensing element in the y direction, the theoretical limit angle is possible up to nearly 180°), the field of view in the x direction is relatively narrow, determined by the F value (focal length/aperture) of the lens. Becomes a corner.

(3) Because of the image plane scanning method using the scanning mirror 15, as the scanning angle (left and right) increases from the central optical axis of the lens 19, the optical gain ( lens 1
In addition to reducing the effective area of the sensing element 18
(the angle of incidence on a to e increases) occurs,
It becomes zero at the limit of visual field. From there on, the contribution of radiation inside the detection elements 18a to 18e (referring to the entire inside of the case including the optical system housing case) increases. Therefore, the internal temperature of the optical system housing case 11 has an important meaning.

(4) Depending on the setting of the optical gain including the infrared transmittance of the lens 19, the equivalent temperature of the amount of infrared radiation incident on the detection elements 18a to 18e generally differs from the actual temperature (the equivalent temperature is (Based on the internal radiation amount based on the internal temperature of the detection part).

(5) Since pyroelectric elements are used as the detection elements 18a to 18e, a feature of their operation and function is that they do not respond to constant incident infrared rays. Therefore, although information on the ambient temperature of the sensing elements 18a to 18e is lost, information on the difference from other radiation, that is, information on the alternating current component, survives through scanning. Therefore, the electric signal waveforms from the detection elements 18a to 18e reflect the amount of radiation variation with respect to radiation based on the inner surface temperature of the detection part, and the absolute values of all voltage levels have no meaning, and the values between them are Only the potential difference has meaning.

Based on the scanning characteristics of the optical system described above, the scanning mirror 15
The waveform of the amount of infrared radiation incident on the detection elements 18a to 18e obtained as the sensor rotates will be explained. For convenience,
Here, only the detectable field of view of the detection element 18c will be considered (the other four detection elements also differ only in the field of view to be detected, and the functions described below are completely the same). FIG. 4a shows an example where there are three targets, one near the edge of the visual field and one at the center of the visual field. The dash-dotted line represents the internal radiation of the detection unit, which decreases from the viewing edge toward the center of the visual field, rises again, and reaches the internal-only radiation level again at the opposite viewing edge. On the other hand, for the target, as shown by the solid line, it is maximum at the center of the visual field and small near the edges of the visual field. The dashed line represents the optical gain curve. The vertical lines indicate the amount of radiation as an absolute amount. The sum of the radiation from the target and the internal radiation of the detection section enters the sensing element 18c. In reality, radiation from the indoor floor comes in, but we will ignore it here for simplicity. The total radiation dose distribution is shown in Figure 4b. As you can see from the figure, due to the optical gain curve, the radiation from the target is quite small near the edge of the field of view, but on the contrary, the internal radiation is large, so the two are added together, and the peak value of the radiation distribution within the field of view is almost the same. Become. However, as mentioned above, the absolute level in Fig. 4b is not preserved (for example, the internal radiation level fluctuates up and down depending on the waveform),
Only the radiation variation is important.

That is, since the output voltage e of the detection element 18c is proportional to the change in the amount of incident radiation W,
If the amount of change is taken based on the waveform in FIG. 4b, the peak value will be approximately constant, and if an appropriate threshold value is provided, relatively uniform pulsing within the visual field will be possible.
As for the signal waveform, due to the resolution of the optical system and the response characteristics of the detection element, the target waveform is considerably blurred and the shape is roughly triangular. However, since the falling time constant is particularly long, it is slightly transformed into an integral wave shape. Therefore, compared to the peak value of the isolated waveform when the target is one person, the peak value of the waveform for two people standing close to each other is approximately twice as high. Since the general shape is triangular, the signal width at that time is also approximately doubled (if the sensing element is of a high-speed response, small resolution type, the peak value remains the same and only the width is doubled). Experiments have shown that when there are three or more people, the peak value is about twice that of one person, and only the width is multiplied by the number of people (three times as much for three people and four times as much for four people). ). In other words, only the width shows a proportional relationship with the number of people. The congestion level detection device utilizes this relationship, making it possible to detect the number of people regardless of their density or location (as the peak of the signal is not used). From the results of experiments, it has been found that a large number of people can be detected with high accuracy by determining the number of people from the width of each waveform using the width of the waveform for two targets (in a continuous state) as a reference.

Next, a fifth example of the circuit configuration of the congestion level detection device is shown. Components that are the same as those in FIG. 3 are designated by the same reference numerals. In FIG. 5, 18a' to 18e' are the output signals of the detection elements 18a to 18e in FIG. (18a' to 18e' are connected to the respective amplifiers). The outputs of each preamplifier constitute five systems 20a to 20e, and are input to a group of band filter circuits 21. Here, the low cutoff frequency of the filter can be determined by considering the scanning period of the scanning mirror, and is approximately 0.1Hz.
(The higher the chopping frequency, the lower the response sensitivity of the sensing element.) Further, the high cutoff frequency may be set to approximately 40 Hz in order to remove noise components caused by the commercial power frequency. 5
Outputs 21a to 21 from the band filter 21 of the system
e is input to the main amplifier circuit group (5 systems) 22. The configuration of the main amplifier circuit group 22 is as shown in FIG. 6, and there are five systems, but for the sake of simplicity, only the band filter output 21c will be considered for one system (FIG. 3, 18c).
signal). 31 is an amplifier, 31c is its output,
A comparator 32 outputs a pulse signal 32c with a signal higher than a predetermined threshold level. 33 is an AND circuit that can be detected only during the time of a timing pulse 26a (details will be described later) and outputs an output 22c. FIG. 7 shows the waveforms and timing of each part in FIG. 6. Figure 7 a is 3
1c, and if there is no person within the detection field of view, the waveform will be as shown by the broken line in the figure. Figure b shows a signal waveform 32c, in which the comparator 32 picks out only signals above the threshold level TL, resulting in pulses of positive logic level. Figure c shows the waveform and timing of the timing pulse 26a.
It is created by the synchronization circuit 26 in the figure (details will be described later).
The time between CTs is the time width of this channel.
By providing this timing pulse 26a, the field of view of the detector can be adjusted. Furthermore, it is possible to avoid malfunctions due to fluctuations in the internal temperature of the optical housing case. In the example in Figure 7, when there are four people in the field of view, b' is 2.
This is the waveform when there is one person (a series of people) and one person b″b.In this way, the main amplifier circuit group 2
Reference numeral 2 denotes a circuit that extracts only a signal (signal corresponding to a person within the field of view) that exceeds a predetermined value within the field of view set by the timing pulse from the output signal of the detection element.

Returning to FIG. 5, 23 is a digital multiplexer circuit which outputs five systems of pulse inputs as one system of pulse trains. This digital multiplexer circuit 23 measures the width of the pulses as shown in FIG. The output 23a is taken out as a column. Figure 8 shows the digital multiplexer circuit 23.
The configuration is shown below. In FIG. 8, an astable multivibrator 31 generates a clock pulse 31a, which is further frequency-divided by a decimal ring counter 32 to generate five groups of clock pulses 32a to 32e shifted by 1/5 period. 33-37 are
NAND gate circuit, 43 to 47 are diodes,
50 is an inverter, and P is a positive power supply. Therefore, when a pulse is input to 22a to 22e, a sequence of the number of clock pulses corresponding to the width of the pulse can be taken out as output 23a.

Returning to FIG. 5, reference numeral 26 is a synchronous circuit, which provides the operation timing of the main amplifier circuit 22 and the counting circuit 24, and outputs 26a, 26b, 2, respectively.
Controlled by 6c. Synchronous circuit 26
The configuration is shown in Figure 9, and the timing chart is shown in Figure 1.
Shown in Figure 0. 17a in Figures 9 and 10
is a synchronizing signal taken out by the photo interrupter 17 shown in FIG. 3, which generates one pulse every time the scanning mirror 15 rotates once, and its waveform is
Shown below. 26b is a reset pulse obtained by the synchronizing signal 17a via the delay circuit 65, which is used to reset the contents of the counter in the counting circuit 24, and its waveform is shown in FIG. 10b. 61
A is a start pulse obtained via the monostable multivibrator 61, and its waveform is shown in FIG. 10c, but the time width T can be set arbitrarily. 6
2a is a pulse for determining the opening timing of the timing pulse 26a, and 63a is a pulse for determining the closing timing of the timing pulse 26a.
3, and the waveforms are shown in FIGS. 10d and 10e. Reference numeral 64 consists of a NOT circuit and an AND circuit, and by inputting the pulse 62a to the NOT circuit and combining this output and the pulse 63a with the AND circuit, a timing pulse 26a can be obtained as shown in FIG. 10f. As described above, by providing the timing pulse 26a, the detection field of view can be limited, and the temperature inside the optical system housing case (back surface portion) is not detected, so malfunctions caused by this can be avoided. 26c is the same as the synchronizing signal 17a and is sent to the counting circuit 24, and the contents of the counter are latched until the next pulse. FIG. 10g shows that there are four people within the detection field of the detection element 18c as explained in FIG.
Output 22c of main amplifier circuit group 22 when there are people
This figure shows the waveform for . Figure 10h
is the waveform of the clock pulse 31a in FIG. 8, and FIG.
2e waveform. Therefore, 22 in Figure 10 n-g
Figure 8 2 synthesized from the signal 32c of c and k
3a represents the pulse width of 22c, that is, a pulse train corresponding to the number of people within the visual field can be obtained.

Returning to FIG. 5, 24 is a counting circuit composed of a counter. In this circuit, a sequence of pulse numbers inputted by a signal 23a is counted each time the scanning mirror rotates once, and a signal 24 representing the number of people in the field of view is counted.
Output a. In this way, the main amplifier circuit group 22
The digital multiplexer circuit 23 converts the signal corresponding to the person in the visual field into the number of clock pulses corresponding to the width of the waveform, and the counting circuit 24 counts this clock pulse number to calculate the number of people in the visual field or crowding. degree can be determined. 25 is an output device. Output devices include a number of people display and a control signal device that outputs signals according to the degree of crowding. To display the number of people, for example, a 7-segment LED may be driven by a decoder (omitted). Further, a control signal output according to the degree of congestion can be obtained using, for example, a flip-flop circuit (omitted).

In the above embodiment, the field of view of each detection element in the x direction in FIG. 3 differs depending on the characteristics of the lens system (18a and 18e are the minimum, and 18c is the maximum). Therefore, by making the timing pulse variable for each channel, unnecessary areas can be cut out, making it possible to have a clear field of view for each channel, and avoiding the effects of temperature fluctuations on the inner surface of the case (especially on the sensing elements at both ends). Furthermore, by making the timing pulse variable, the detection field of view can be set arbitrarily, increasing the degree of freedom in the installation environment.

Moreover, if the threshold level of the comparator shown in FIG. 632 can be automatically adjusted according to the ambient temperature, sensitivity unevenness due to seasonal temperature fluctuations can be suppressed. To achieve this, a temperature sensor can be built into the optical system housing case (a thermistor or an IC as a temperature sensor controller), and the threshold level can be set using the temperature-related fluctuations in the output voltage ( (circuit omitted).

Furthermore, in the above embodiment, the coating on the back surface of the scanning mirror was applied only to one side of the flat plate.
The coating may be applied to both sides of the flat plate,
In this case, the synchronization signal extracted by the photointerrupter only needs to generate two pulses each time the scanning mirror rotates once. In this case, the rotational speed of the motor may be reduced to 1/2, which is effective in reducing rotational noise. Further, the shape of the scanning mirror is not limited to a flat surface, but may be a polygonal column (polygon mirror) or a curved surface.

FIG. 11 shows another embodiment of the scanning mirror,
In this example, the scanning mirror 70 includes a coating surface 70a parallel to the rotation axis 71 and a coating surface 70b oblique to the rotation axis 71. With such a configuration, the output signal from the detection element obtained by parallel scanning of the coating surface 70a (parallel to the x-axis in FIG. 3) and the oblique scanning of the coating surface 70b (parallel to the x-axis in FIG. 3) By combining the output signal from the sensing element obtained by
The resolution can be further improved, and the presence of a field of view (dead zone) where detection is insufficient due to gaps between sensing elements can be eliminated.

The above is the congestion level detection device proposed earlier (patent application 1983).
-172379).

By the way, as the detection element of the congestion degree detection device, an inexpensive and high quality pyroelectric type is used. As mentioned above, this is a differential type in principle and can provide an output proportional to the fourth power of the temperature difference between the background temperature and the object to be measured, but it does not respond to constant incident infrared rays. That is, by scanning, only information on the difference from other radiation (information as an alternating current component) is output. Furthermore, due to the influence of ambient temperature, etc., the internal radiation level of the detection section fluctuates up and down, and the detection element output signal waveform also changes. Merely setting a threshold value may cause false alarms. Furthermore, depending on how the threshold value is set, it may be necessary to narrow the width of the timing pulse and, therefore, to narrow the detection field of view.

The present invention has been made in view of these points,
The aim is to be able to separate signals based on infrared radiation from a human body target from signals based on internal radiation without being affected by ambient temperature etc. and without narrowing the detection field of view. An object of the present invention is to provide a device that can accurately measure the number of people.

The feature of the present invention is that instead of simply extracting only signals larger than a predetermined value from the output signal of the infrared sensing element within the field of view, the output signal of the infrared sensing element at the front end of the field of view is sampled and held as a reference value, A circuit extracts only the signal that is larger than the reference value by a predetermined value (threshold value) from the output signal of the infrared detection element. and a synchronization circuit that sets the field of view in synchronization with the scanning mirror so that the front end of the field of view is at the time when the differential coefficient of the output signal waveform of the detection element inverts to positive or at a predetermined time, whichever is earlier. The point is that

Hereinafter, the present invention will be explained based on the drawings.

FIG. 12 is a diagram showing the circuit configuration of the congestion degree detection device according to the present invention, which corresponds to a part of the main amplifier circuit group 22 and synchronization circuit 26 in FIG. Although only (corresponding to Figure 6) is shown, the same applies to other systems. Note that the parts omitted from the drawings are the same as those in FIG. 5, and the same parts as in FIG. 5 are designated by the same reference numerals.

In FIG. 12, 81 is a buffer amplifier for supplying analog signals at low impedance, and 82 is a clamping capacitor. 8
6 is a comparator, 87 is a threshold voltage setting volume, and the part consisting of the buffer amplifier 81, clamping capacitor 82, comparator 86, and threshold voltage setting volume 87 is the main amplifier circuit group in FIG. 22, and the remaining portion corresponds to a part of the synchronous circuit 26. Analog switches 83 and 84 are connected in parallel with a diode 85 to form a switch circuit, one end of which is grounded and the other end connected to point G. Analog switch 8 following capacitor 82
When shorted to ground at 4, current flows through capacitor 82 and the instantaneous value of the analog signal relative to zero volts is sampled. When the analog switch opens,
The sample value at that time is charged in the capacitor 82, and the potential Vg at point G is given as the difference between the potential Vi of 21c and the sample value. That is, Vg(t)=0 (contact of switch 84 is ON) Vg(t)=Vi(t)−Vi(ts) (contact of switch 84 is OFF) (However, t represents time, and ts is when switch 84 is
Indicates the time at the moment it turned off. ) Furthermore, the analog switch 83 is turned ON-
OFF differs from the unconditional sampling mentioned above,
Polarity sampling (conditional sampling) by diode 85 is added. In other words, in the ON state, Vg(t)=0 (Vg(t)<0) Vg(t)=Vi(t)−Vi(ts)(Vg(t)>0) However, ts varies from negative Vg(t) to This is the moment when it became correct.

86 is a comparator, and the potential Vg at point G
and the potential Vr at point R, and outputs V ₀ of 22c. That is, V ₀ =1 (Vg≧Vr) V ₀ =0 (Vg<Vr) where Vr is the threshold given by the volume 87.

P' is the positive power supply voltage, 62' (corresponding to 62 in Figure 9)
is a monostable multivibrator that generates a pulse 62a' (corresponding to 62a in FIG. 9, hereinafter referred to as the opening timing pulse OTP) that defines the period during which polarity sampling is performed (conditional sampling period) by closing the analog switch 83. , 63' (corresponding to 63 in FIG. 9) is a pulse 6 that defines the period from when the analog switch 84 is opened to perform unconditional sampling until the gate is closed.
3a' (corresponding to 63a in FIG. 9, hereinafter referred to as a closing timing pulse, abbreviated as CTP), which are the same as those shown in FIG. 9, respectively. The diode 85 is for performing polar sampling, the analog switch 83 is of a normally open type, and the analog switch 84 for performing unconditional sampling is of a normally closed type. 61a is OTP,
This is the start pulse that determines the timing of CTP and is the same as that shown in FIG.

Next, before explaining the operation of this circuit, the characteristics of the waveform to be processed and the necessary items to be processed will be summarized below. FIG. 13 shows an example of the signal 21c to be processed.

(1) When the target does not exist within the field of view (see the solid line waveform in Figure 13), the period B in which the floor is viewed, which is the target field of view, is compared with the detection unit internal scanning periods A to B.
~C, C~D are generally in the negative direction.
The first reason for this is that the temperature of the detection section is higher than the ambient temperature due to self-heating of the detection section (heat generation of the motor and heat generation of the preamplifier). Second, because the detection unit is installed at a higher location than the floor, the ambient temperature around the detection unit is higher than the floor due to the difference in temperature between height and low due to the normal temperature distribution in the room (the ceiling is high and the floor is low). It is. Therefore, the potential difference between A to B and B to D changes every moment. Here, even if there is a change in bed temperature or a change in the temperature of the detection part, it is required that no false alarm is issued and that the target is not missed. Since the target human body temperature is always higher than the floor temperature, the threshold value must be selected higher than the floor temperature level, but the equivalent temperature level of the target is not necessarily higher than the temperature level of the detection part, so it is necessary to choose a threshold value that is somewhere between them or the temperature of the detection part. It is necessary to set a threshold on the level. In this case, some sort of gate function is required to prevent false alarms from being issued near both ends of the field of view. This gate function includes the timing to open the gate and the timing to close the gate.
It is necessary to electrically limit the visual field of CT by generating OTP and CTP from the start pulse generation timing, and it is also necessary to hold the sample value of Vi(t) of OT.

(2) When there is more than one target (see the broken line waveform in Figure 13).

The figure shows an example where an isolated single target exists at the center of the field of view. It is sufficient to add a threshold value Vr to the sample value in OT and to pulse the portion exceeding the threshold value (the hatched portion). here,
If the OT is fixed, the pulse will not be emitted when the target is at the OT position, and in that case, the sample value at the OT will be different from the target even if there are several other targets or the OT is full. Since they correspond to equivalent temperatures, they all have the serious drawback of not being able to obtain pulses.

In other words, in the case of OT fixation, that position becomes a singular point, which is significantly affected by whether or not a person is present there, essentially resulting in a reduction in the viewing angle. Therefore, in order to prevent this, if there is a target during the OTP period, the differential coefficient of the signal waveform will always be positive, so if the positive inversion position is set as the actual OT, the above-mentioned drawback will disappear. The present invention enables preset OT and automatic OT by combining simple elements.
(OT automatic adjustment) has been realized (details are described below).

Next, the operating principle of this circuit will be explained for each operating mode and target distribution.

FIG. 14 shows the relationship between operating modes and timing pulses. A is a start pulse 61a, which corresponds to when T=0 in FIG. 10c, and is the synchronization signal (timing pulse) in FIG. 10a.
FIGS. 14b and 14c show an opening timing pulse (OTP) and a closing timing pulse (CTP), respectively, which are generated based on a synchronization signal generated at a specific position of the scanning mirror rotation angle. Points 62' and 63' in FIG. 12 perform this function. The timing at which OTP changes from 1 to 0 is defined as opening timing (OT), and the timing at which CTP changes from 1 to 0 is defined as closing timing (CT).
For OTP, use analog switch 83 in Figure 12.
CTP is used to control 84. The analog switch 83 circuit is connected to ground through a diode 85, and the analog switch 84
The circuit is unconditionally connected to ground. Therefore, the parallel circuit of analog switches 83 and 84 is
During the period when OTP=1, that is, from the start pulse generation timing (ST) to OT, Vg<
It operates in a conditional short-circuit mode where if it is 0, it is a short circuit, and if Vg<0, it is an open circuit.

Next, during the period from OT to CT, it operates in an unconditionally open mode with no short circuits.

Finally, during the period from CT to ST, it operates in an unconditional short-circuit mode with no open circuits.

Therefore, according to the present invention, when a target exists between ST and OT, a sample value at a timing corresponding to the point of change in the sign of the signal is given as a comparison reference potential, and when a target exists between OT and CT. In contrast, sample values at fixed timings are given as comparison reference potentials, which not only prevents the influence of ambient temperature, etc., but also allows a wide detection field of view regardless of the setting position of the OT. .

Next, the operation will be explained based on specific signal waveforms.

In the case shown in Fig. 13 (a) At the moment when the mode of the previous cycle ends and the mode starts at ST, the contact of switch 84 is closed.
Since it is OFF, the Vi sampled by ST
(t) is held as the potential difference Vi _(ST) across the capacitor 82. The clamping gate voltage Vg(t) is given by Vg(t)=Vi(t)−Vi _(ST) =0.

(b) In the first half of the mode, as shown in Figure 13 A to B, the detector sees internal radiation, and almost all Vi(t)
is constant, Vg(t) is also almost constant, and if it changes with a slightly positive slope (differential coefficient) as shown in the figure, the gate is equivalently open and Vg(t) =Vi(t)-Vi _(ST) =0 However, unless the threshold voltage Vr is exceeded, the output pulse _V0 is not output.

That is, the condition of V ₀ =0 (Vg(t)−Vr=Vi(ST)−Vr<0) is satisfied.

(c) In the second half of the mode, when the end of the visual field becomes visible (from B to OT in Figure 13), if there is no target, the floor becomes visible. Then Vi(t) changes in the negative direction.

When Vg(t)=Vi(t)-Vi _(ST) <0, the diode 85 becomes conductive and short-circuited, closing the gate. That is, Vg(t)=0.

(d) When OT occurs, the mode ends, so switch 83 opens and the sample value at the time of OT is displayed.
When Vi _(OT) becomes the potential difference between both ends of the capacitor 82, the mode shifts to a mode in which the gate is unconditionally opened. Therefore, Vg(t)=Vi(t)−Vi _(OT) is given, and V ₀ =1 (Vg(t)−Vr=Vi(t)−Vi _(OT) −Vr≧0) V ₀ =0 ( A signal is detected under the pulsing condition of Vg(t)-Vr=Vi(t)-Vi _(OT) -Vr<0), and if there is a target, it is pulsed.

(e) The mode of becoming CT ends and the mode shifts to CT mode. That is, since the switch 84 is closed and an unconditional short circuit occurs, Vg(t)=0.

For waveforms where the target is near OT.

After the (a) and (b) modes end, the process up to the first half of the mode is exactly the same as the above-mentioned (a) and (b).

(c) When the mode enters the second half and the floor becomes visible,
Vi(t) changes in the negative direction and becomes Vg(t)=Vi(t)−Vi _(ST) <0, and the diode 85 becomes conductive and short-circuited, closing the gate. That is, Vg(t)=0.

However, if t' is the time when the target becomes visible and Vi(t) starts to change in the positive direction before OT, then Vg(t) = Vi(t) - Vi(t') > 0, and t' The value sampled at the timing becomes a potential difference across the capacitor 82, and the gate is equivalently automatically opened by the action of the diode 85.

Therefore, V ₀ = 1 (Vg(t)−Vr=Vi(t)−Vi(t′)−Vr≧0) V ₀ =0 (Vg(t)−Vr=Vi(t)−Vi(t′ )−Vr<0), and the automatic
It will have the effect of OT, and even if there is a target near OT, it will be detectable.

(d) If OT comes while Vi(t) is still increasing, the potential difference across the capacitor 82 will be
The gate is opened at Vi (t′ _{) instead of Vi (OT)} , and the operation is the same as in (d) above. Vi(t)
If OT comes after decreasing, the result is the same as (e).

(e) After CT, it is exactly the same as in (e) above.

Therefore, even if a target exists before the fixed timing OT, it can be detected and the detection field of view can be widened.

For waveforms that are present throughout the target field of view.

As for the waveform, B→C→D in Figure 13 is A→B.
It comes to the top than when . In other words, the waveform is reversed and A
→ B → C becomes a rising waveform and analog switch 8
3 is closed, but due to the action of the diode 85, the gate equivalently changes to the mode while remaining open at the timing ST.

After that, it is the same as (d) and (e).

As described above, extremely complex signal processing can be realized with a simple combination of the capacitor 82, analog switches 83 and 84, and diode 85.

In the above embodiment, the threshold voltage of the comparator 86 is fixed, but it can also be automatically adjusted to eliminate sensitivity unevenness due to fluctuations in ambient temperature.

In addition, in the above explanation, this congestion degree detection device is explained as measuring only people, but it can also be measured using a moving car or motorcycle (the temperature of the engine part is sufficiently high compared to the ambient temperature). It can also be applied to measuring traffic volume.

As described above, according to the present invention, it is possible to accurately measure the number of people without being affected by the ambient temperature or narrowing the detection range, and the circuit configuration is realized using an extremely simple combination of elements. Therefore, this congestion degree detection device, which essentially requires a multi-channel signal processing circuit, has a very large effect on miniaturization and economical efficiency.

[Brief explanation of the drawing]

Figures 1a and b are diagrams for explaining the scanning method of the congestion level detection device, Figure 2 is a sectional view of the elevator hall, Figure 3 is a diagram showing the configuration of the optical system of the congestion level detection device, and Figure 4 Figures a and b show the distribution of the amount of infrared radiation incident on the detection element, Figure 5 shows the conventional circuit configuration of the congestion detection device, and Figure 6 shows the conventional circuit configuration of the main amplifier circuit group. 7a to 7c are diagrams explaining how to obtain a signal corresponding to the number of people in the visual field from the output of the detection element, FIG. 8 is a diagram showing the circuit configuration of the digital multiplexer circuit, and FIG. A diagram showing the circuit configuration of a synchronous circuit, FIG. 10 a to n are time charts of each signal, FIG. 11 is a diagram showing another embodiment of the scanning mirror, and FIG. 12 is a circuit of the congestion degree detection device according to the present invention. 13 is a diagram showing a relationship between signal waveforms and each timing, and FIGS. 14a to 14d are diagrams showing a relationship between operation modes and timing pulses. 1, 15... Scanning mirror, 2, 19... Lens,
3, 18a to 18e...detection element, 5, 14...
Infrared rays, 13...waiting customers, 20...preamplifier group,
21...band filter circuit group, 22...main amplifier circuit group, 23...digital multiplexer circuit, 24...counting circuit, 25...output device, 26
... Synchronous circuit, 62', 63' ... Monostable multivibrator, 81 ... Buffer amplifier, 82 ...
Capacitor, 83, 84...analog switch,
85...Diode, 86...Comparator, 8
7... Volume for voltage setting.

Claims (1)

[Scope of Claims] 1. A scanning mirror that rotates at a constant cycle, an infrared detection element that outputs a signal according to a change in infrared rays incident on the scanning mirror, and a synchronization circuit that generates a timing pulse for setting the field of view of the detection element; a main amplifier circuit that extracts only a signal that is equal to or higher than a predetermined value within the field of view set by the timing pulse from the output signal of the infrared detection element; A crowding level detection device comprising a circuit that determines the number of people in the field of view or the degree of crowding from a waveform width of a signal that is equal to or greater than a value, wherein the synchronization circuit detects the front end of the field of view from a synchronization signal synchronized with the rotation of the scanning mirror. It consists of a circuit that generates timing pulses for setting the and rear end, and a parallel connection of switches each operated by the timing pulses, one end of which is grounded, and the other end connected to the main amplifier circuit. The main amplifier circuit inputs the output signal of the infrared detection element to a comparator via a clamping capacitor, and the potential on the comparator side of the capacitor is grounded by the switch circuit. Alternatively, the output signal of the infrared sensing element is held as a sample value in the capacitor when the potential is in the grounded state, and the output signal of the infrared sensing element and the sample value are held in the capacitor when the potential is in the grounded state. The difference between the two potentials is input to the comparator, and the potential is set to the ground state before the start of scanning by the timing pulse and the switch circuit, and the front end of the field of view is set from the start of scanning. Until the timing pulse is generated, when the difference between the output signal of the infrared sensing element and the sample value is negative, the state is in the ground state, and when it is positive, the state is in the non-ground state, and the timing pulse that sets the front edge of the field of view is When this occurs, the infrared sensing element is brought into a non-grounded state so that the differential coefficient of the output signal waveform of the infrared sensing element inverts to positive, or the time when a predetermined timing pulse is generated that sets the front edge of the field of view, whichever is earlier. A congestion degree detection device characterized in that the point in time is the front edge of the field of view.