JP2540402B2 - Moving object detection method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for optically detecting a moving object, and more particularly to a technique for detecting a moving object by capturing light from a detected object without a light projecting portion.

[0002]

2. Description of the Related Art Conventionally, there is a system using a wide-angle lens as this kind of technique. That is, in the method of forming an image of the detected object on the light receiving surface through the lens system without a light projecting portion, generally, ambient light is reflected on the detected object except when the detected object is a light emitting object. Incident on the detector. When the detected object does not move, if the intensity of ambient light is constant, the amount of light incident on the detector is constant with time. When the object to be detected moves, the amount of light incident on the detector changes with time, except in special cases such as a plain plate where the object to be detected is infinitely large. Then, the moving body can be detected by the temporal change of the light amount. This method is extremely simple, but it is not practical because of large optical noise. That is, the change in the amount of light on the light-receiving surface caused by the movement of the detected object is extremely small, and cannot be distinguished from the change in the amount of light on the light-receiving surface except when the detected object moves. One of the largest optical noises is AC light noise from fluorescent lamps.

On the other hand, for example, 2N on the light receiving surface
The light receiving element divided into pieces is arranged, and these are alternately connected to the plus terminal and the minus terminal, and the difference signal of the signals collected at the plus terminal and the minus terminal is made. For example, there is a method of removing the influence of AC light of a fluorescent lamp or the like by extracting a frequency component sufficiently lower than 50 Hz or 60 Hz. According to this method, for example, it is possible to detect a pedestrian in a place with a predetermined brightness. That is, even if the uniformly incident light changes with time, there is no difference between the two signals. When the detected object moves, the image of the detected object on the light receiving surface moves,
Since a difference occurs between the two signals, the moving body can be detected by the difference between the two signals. In this method, a signal change occurs only when the brightness moves on the light receiving surface, so that the optical noise can be considerably improved as compared with the above method, and the sensitivity can be increased accordingly.

In order to widen the detection range in this method, the number of divisions of the light receiving element is increased, and as shown in FIG.
A method is conceivable in which the light receiving lens 4 is a lens having a wide angle θ, that is, a wide angle lens. According to this method, 1
Although it is possible to set the detection range to a certain extent with one detector, a dedicated light receiving element 5 designed and created for this purpose is usually required. Further, if a wide-angle lens is used, the image on the light-receiving surface 9 is reduced by that amount, so that resolution is required for the image of the detection area, and this causes a problem that a precise lens system is required.

In view of such a problem, the inventor previously invented the method shown in Japanese Patent Application No. 1-2221798, that is, FIG. The gist of the present invention is equivalent to arranging a plurality of light receiving elements 5 on the light receiving surface 9 by providing the mirror 8 between the lens 4 and the light receiving element 5 and forming a virtual image of the light receiving element 5.
A moving object detector having a wide detection range and a small sensor 2 size can be realized with one light receiving element 5 having a small number of divisions.

However, according to the method shown as the conventional example, when the sensor 2 is detected in an oblique direction with respect to the front, there is a problem that the sensitivity rapidly decreases with the angle when the angle becomes large. That is, in the case of 45 degrees with respect to the axis of the sensor, the incident light amount itself is
In addition to s45 = 0.7 times, the aberration of the lens system becomes large and, for example, one lens does not actually function as an imaging lens system. Much larger. Aberration can be reduced by using an expensive and precise lens group, but the entire sensor becomes large and expensive. As described above, the conventional detection method has a problem that the sensitivity in the oblique direction is significantly reduced when the viewing angle is extremely widened.

[0007]

SUMMARY OF THE INVENTION The problem to be solved by the present invention is that, when the sensor is detected in an oblique direction with respect to the front, the sensitivity decreases rapidly with the angle as the angle increases. . That is, if the viewing angle is made extremely wide, the sensitivity in the oblique direction is significantly reduced.

[0008]

According to a first aspect of the present invention, a detection area is divided into a plurality of small areas, and a line connecting the center of each small area to the center point of the light receiving surface shields light between the light receiving surface and the detection area. A light-shielding plate having a hole is arranged at a position passing through the surface, a light-receiving element divided into 2N elements is arranged at the center point of the light-receiving surface, and light incident on the light-receiving plate through a plurality of holes of the light-shielding plate Two
An AC component of a difference signal (AB) between a total A of outputs of predetermined N elements and a total B of outputs of the remaining N elements of the photocurrents generated in the N elements,
The moving object in the detection area is detected by the DC component of the sum signal (A + B). According to a second aspect of the present invention, the detection area is divided into a plurality of small areas, and a hole is provided where a line connecting the center of each small area and the center point of the light receiving surface passes through the light shielding surface between the light receiving surface and the detection area. A light-shielding plate is arranged, and the light-receiving element divided into 2N elements is arranged at the center point of the light-receiving surface, and the photocurrent generated in the 2N elements of the light-receiving element by the light incident through the plurality of holes of the light-shielding plate Among them, the total A of the outputs of the predetermined N elements and the total B of the outputs of the remaining N elements are multiplied by a current amplification factor β by a pair of transistors, and this difference signal β (AB) AC component and the DC component of the signal βA, the DC component of the signal βB, or the sum signal β (A +
The moving body in the detection area is detected by the DC component of B).

Thus, when a moving body is present in the direction connecting the holes of the light shielding plate and the light receiving element, the light incident on the light receiving element changes in position. A positional change of the incident light on the light receiving surface appears as a temporal change of the difference signal (AB). That is, an AC component appears in the difference signal (A-B). The amplitude of the AC component of the difference signal (A-B) depends on the movement of the detected object, but in addition to this, it is proportional to the ambient illuminance. Since the environmental illuminance can be detected by the DC component of the sum signal (A + B), the first invention moves by comparing the amplitude of the DC component of the sum signal (A + B) and the amplitude of the AC component of the difference signal (AB). To detect the body. The second invention is the sum signal β (A + B)
The moving object is detected by comparing the DC component of the signal with the amplitude of the AC component of the difference signal β (A-B).

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. That is, the sensor 2 that detects the detected object 1
As shown in FIG. 3, a four-divided light receiving element 5 is formed on a silicon substrate 3, and a light shielding plate 7 is provided on the front surface of the light receiving element 5. And this sensor is the four-division light receiving element 5
Are arranged on the light receiving surface 9. As shown in FIG. 4, a plurality of holes 10 are provided in the light shielding plate, and each hole has a line from the center of the light receiving element to the center of each small region ws of the detection region W as shown in FIG. It is located where it intersects with the board 7. Optical signal L incident from the hole 10 of the light shielding plate 7
FIG. 6 shows a configuration block diagram of the first invention of the processing circuit of FIG. In FIG. 6, assuming that the four-division light-receiving element 5 for detecting incident light and each element of the four-division light-receiving element 5 are divided into two groups and the signals of each group are A and B, this difference signal (A-B ) Is added to the differential amplifier 11 and the sum signal (A + B) thereof is taken out. A differential amplifier 11 that amplifies the difference signal (A-B), a bandpass filter 13 that extracts a predetermined frequency component, a high-cut band amplifier 14, a bandpass filter 15, and a window comparator 16 are sequentially connected. Adder 1
The sum signal (A + B) added in 2 is amplified by the amplifier 18 via the low-pass filter 17, and the DC component is connected to the reference input side of the window comparator 16. According to such a configuration, since the condenser system such as a lens is not provided, the photocurrent is extremely small.

In consideration of this point, the circuit configuration shown in FIG. 7 may be adopted. The configuration of FIG. 7 is different from the configuration of FIG. 6 in that the portion surrounded by the broken line in FIG. 6 is configured as shown in FIG. The difference is that the signal βA and the signal βB are processed instead of the signal A and the signal B.
An amplifier 20 is connected between the differential amplifier 11 and the adder circuit 12.

More specifically, the portion surrounded by the broken line in FIG. 7 is shown in FIG. In FIG. 8, the optical signal currents A and B are created by dividing the respective element outputs of the four-division light receiving element 5 into two groups and connecting them. The optical signal currents A and B are connected to the bases of the pair transistors Q1. The emitters of the pair transistor Q1 are coupled to each other and connected to the ground by the resistor R1. Each collector of the pair transistor Q1 is connected to each collector of the pair transistor Q2 forming a current mirror circuit. Q
A resistor R3 for current-voltage conversion on the output side of the current mirror 2
Is connected. The capacitor C1 provides a predetermined frequency filter characteristic, and the capacitor C2 is a coupling capacitor. An intermediate potential is given by R2 and D2 to D4.

Next, the operation in FIG. 6 will be described.
First, consider a case where the distance from the light shield plate 7 to the detected object 1 is sufficiently large with respect to the distance between the light shield plate 7 and the light receiving element 5. In this case, the light reaching the hole 10 of the light shielding plate 7 from the detected object 1 can be regarded as parallel light. In this case, like the pinhole camera, one image is captured on the light receiving surface 9 for one hole 10 of the light shielding plate 7. The image projected on the four-division light-receiving element 5 is a small area ws centered on the point where the line connecting the center of each hole 10 of the light-shielding plate 7 and the center of the four-division light-receiving element 5 intersects the detection area W. The size of this small region is determined by the ratio of the distance L1 between the light receiving element and the light shielding plate 7 and the distance L2 between the light shielding plate 7 and the detection region W. Small area ws corresponding to the number of holes 10 of the light shielding plate 7
Image is superimposed on the four-division light receiving element 5. Even if the detection area W receives light having an AC component such as a fluorescent lamp, if the light is evenly incident on the four-division light receiving element 5, the difference between the signals A and B of the two groups of the light receiving elements is detected. Signal (A
No AC component appears in -B). When a moving object is present in the small area ws of the detection area W, the image on the four-division light receiving element 5 moves in position. Therefore, an AC component is generated in the difference signal (AB) of the two groups of the outputs of the respective elements of the four-division light receiving element 5. Since the AC component of the difference signal (A-B) is minute, a predetermined amplification K1 is performed and the result is input to the determination input of the window comparator. The signal at this time is the difference signal K1 (A-
B). The magnitude of the AC component of the difference signal (AB) depends not only on the moving state of the moving body but also on the illuminance of the detection area W in which the moving body exists. For example, the detection area W
When the illuminance of is halved, the difference signal (A-B) is also halved.
Therefore, when the magnitude of the difference signal (A-B) is judged, it is less likely to be affected by the illuminance of the detection area W when compared with a signal corresponding to the illuminance of the detection area W, instead of being compared with a constant value. You can Since the DC component of the sum signal (A + B) becomes a signal corresponding to the illuminance of the detection area W, this is amplified by a predetermined magnification and then used as the reference input of the window comparator. The signal at this time is the sum signal K2 (A + B). The window comparator issues a moving object detection signal when the absolute value of the AC component of the difference signal K1 (A-B) signal exceeds the value of the sum signal K2 (A + B).

In the operation of FIG. 7, even if the detection region W receives light having an AC component such as a fluorescent lamp, the four-division light receiving element 5
If the light is evenly incident on the upper portion, no AC component appears in the difference signal (AB) between the signals A and B of the two groups of light receiving elements, and therefore the difference signal β (AB) is also AC. No ingredients appear. When a moving object is present in the small area ws of the detection area W, the image on the four-division light receiving element 5 moves in position. Therefore, since an AC component is generated in the difference signal (AB) of the two groups of the outputs of the respective elements of the four-division light receiving element 5, an AC component also appears in the difference signal β (AB) multiplied by β. Difference signal β (A-
The AC component of B) is amplified by a predetermined amount M1 and input to the judgment input of the window comparator. The signal at this time is defined as the difference signal βM1 (AB). The magnitude of the AC component of the difference signal (AB) depends not only on the moving state of the moving body but also on the illuminance of the detection area W in which the moving body exists.
That is, for example, when the illuminance of the detection area W becomes half, the difference signal (A-B) also becomes half. Therefore, the difference signal (A-
When comparing the magnitude of B) with a signal corresponding to the illuminance of the detection region W, instead of comparing with a constant value,
It is less likely to be affected by the illuminance of the detection area W. Sum signal (A
Since the DC component of + B) becomes a signal corresponding to the illuminance of the detection area W, this signal is also multiplied by the current amplification factor β of the transistor and then amplified by a predetermined factor before being used as the reference input of the window comparator. The signal at this time is the sum signal βM2
(A + B). Wind comparator is the difference signal β
The absolute value of the AC component of M1 (A-B) is the sum signal βM2 (A
If the value of + B) is exceeded, a moving body detection signal is issued. β
Changes due to temperature changes and the like, the signal amplification factors of the difference signal (A−B) and the sum signal (A + B) are βM1 and βM2, but they change, but they are exactly the same as the influence of the change of the environmental illuminance. That is, for example, when the illuminance of the environment becomes 1/2 and when β becomes 1/2 for some reason, the input signal state of the comparator is the same. Thus, the temperature variation of the value of the current amplification factor β of the transistor,
This is a method in which individual differences among products do not affect, and an extremely large amplification factor can be obtained by a simple method.

In the operation shown in FIG. 8, when photocurrent signals A and B are generated in the four-division light receiving element 5, this current is transferred to the pair transistor Q.
(Β + 1) to each emitter because it flows to each base of 1
The current of A and (β + 1) B flows, and (β + 1) flows to R1.
A voltage drop of the value of (A + B) × R1 occurs. On the other hand, currents βA and βB flow through the collector of the transistor. Since a current obtained by subtracting one collector current from the other collector current by the pair transistor Q2 flows through the resistor R3,
A current β (A-B) flows through the resistor R3, and a voltage drop having a value of β (A-B) × R3 occurs in the resistor R3. β is 1
If it is much larger than, then β times and (β + 1) times can be regarded as β times. Thus, the difference signal β (A
+ B) and the sum signal β (A + B) can be taken out with respective predetermined scaling factors. Therefore, even if the signal A and the signal B are weak because the light collecting system such as a lens is not provided, the signal can be amplified by such a simple method.

When the moving object is detected by comparing the difference signal (AB) and the sum signal (A + B), the difference signal β (A-B) and the sum signal β (A + B) are compared. The case where the moving object is detected has been described above, but since the DC components of the signals A and B are almost the same, the sum signal (A +
Similar results are obtained by using double A or double B instead of B), or double βA or double βB instead of the sum signal β (A + B).

When the illuminance of the detection area W is close to zero, the DC component of the sum signal (A + B) and the sum signal β (A +
The DC component of B) becomes close to zero, and the absolute value of the AC component of the difference signal K1 (A−B) is the same as that of the sum signal K2 (A + B) even if the difference signal (A−B) has a slight noise. There is a risk of causing a malfunction that the value exceeds the value or the absolute value of the AC component of the difference signal βM1 (A−B) exceeds the value of the sum signal βM2 (A + B) to output from the window comparator. For this problem, the sum signal (A +
Even if B) is zero, the reference input value of the window comparator will not be completely zero K2 (A + B) + d
Or βM2 (A + B) + d is effective. If the value of d is made larger than the noise amplitude appearing in the determination input signal section of the window comparator when the illuminance of the detection area W is zero, the above malfunction can be prevented.

Although the above description has been given for the case of the four-divided light receiving element 5 shown in FIG.
You may use the light receiving element divided into pieces. In this case, the distribution of + or − elements may be two-dimensionally arranged regularly, or may be arranged irregularly as shown in FIG. 9B.

The dividing direction of the light receiving element may be a one-dimensional direction as shown in FIG. 9 (c). In this case, the number of elements may be two. In this case, the moving component in the dividing direction of the moving body is detected as a signal.

The light shield plate 7 may be a flat plate or may be curved.

According to the moving object detecting method of the present invention, for example, when the light shielding plate 7 having the holes 8 formed in a square shape as shown in FIG. 10 is used, the detection area W also becomes hollow as shown in FIG. It has a letter shape and can be applied to window security.

[0022]

As described above, according to the present invention, among the photocurrents generated in the 2N elements of the light receiving element by the light incident through the plurality of holes of the light shielding plate, the total A of the outputs of the predetermined N elements and The AC component of the difference signal (A−B) from the total B of the outputs of the remaining N elements and the sum signal (A +
A moving object in the detection area W is detected by the DC component of B), and since no lens is used,
There is an effect that there is no decrease in sensitivity in the oblique direction due to aberrations that cannot be avoided in the imaging system, and there is little decrease in sensitivity in the oblique direction. In addition, the shape of the detection region W is the hole 10
Can be changed very easily at the position. Further, one hole 10 of the light shielding plate 7 corresponds to one small area ws, and a collection of the small areas ws forms the detection area W. Therefore, the detection area W is, for example, a circle, a quadrangle, a triangle, or a U-shape. It is possible to easily form the detection region W having a square shape or a square shape.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a moving body detection device using a conventional wide-angle lens.

FIG. 2 is a configuration diagram showing a moving body detection device that measures a wide angle by using a conventional mirror.

FIG. 3 is a vertical cross-sectional view illustrating the configuration of the sensor of the present invention.

FIG. 4 is a perspective view illustrating a relationship between a four-division light receiving element of the present invention and incident light.

FIG. 5 is a perspective view for explaining the relationship between the detection area and the small area according to the present invention.

FIG. 6 is a block diagram showing an embodiment of a moving body detection method of the present invention.

FIG. 7 is a block diagram showing a second embodiment of the moving body detection method of the present invention.

FIG. 8 is an output preamplifier circuit diagram of a light receiving element in the moving body detection method of the present invention.

FIG. 9 is a plan view showing the relationship between the array of light receiving elements and the number of elements in the moving body detecting method of the present invention.

FIG. 10 is a plan view of a light shielding plate when the detection area in the moving body detection method of the present invention is square-shaped.

11 is a perspective view showing a detection region in the case where the light shielding plate shown in FIG. 10 is used.

[Explanation of symbols]

 1 Object to be detected 2 Sensor 3 Silicon substrate 5 4-division light receiving element 7 Light-shielding plate 9 Light receiving surface 10 Hole 11 Differential amplifier 12 Addition section 13 Bandpass filter 14 High-cut bandpass amplifier 15 Bandpass filter 16 Wind comparator 17 Lowpass filter 18 Amplifier 20 Amplifier Q1 Pair Transistor R1 Resistor Q2 Pair Transistor R3 Resistor C1 Capacitor C2 Capacitor W Detection Area ws Small Area

Claims (2)

(57) [Claims] 1. A light shielding plate is arranged between the light receiving surface and the detection region,
The detection area is divided into a plurality of small areas, and a hole is provided in the place where the line connecting the center of each small area and the center point of the light receiving surface passes through the light shield plate between the light receiving surface and the detection area. The divided light receiving element is arranged at the center point of the light receiving surface, and among the photocurrent generated in the 2N elements of the light receiving element by the light incident through the plurality of holes of the light shielding plate, the predetermined N elements The AC component of the difference signal (A−B) between the total output A and the output B of each of the remaining N elements, the DC component of the signal A, the DC component of the signal B, or the sum signal (A + B). A moving body detection method, which detects a moving body within the detection area based on a DC component. 2. A light shielding plate is arranged between the light receiving surface and the detection area,
The detection area is divided into a plurality of small areas, and a hole is provided in the place where the line connecting the center of each small area and the center point of the light receiving surface passes through the light shield plate between the light receiving surface and the detection area. The divided light receiving element is arranged at the center point of the light receiving surface, and among the photocurrent generated in the 2N elements of the light receiving element by the light incident through the plurality of holes of the light shielding plate, the predetermined N elements The total output A and the total output B of each of the remaining N elements are multiplied by the current amplification factor β of the pair of transistors, and the AC component of the difference signal β (AB) and the DC component of the signal βA. , DC component of signal βB, or sum signal β
A moving body detection method, wherein a moving body in the detection area is detected by the (A + B) DC component.