JP2000338225A - Device and system for detecting object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a device and system for detecting object to surely identify a lane marker from other reflecting objects. SOLUTION: An object detecting system is constituted by embarking radar equipment 12 and a polarizer 14 on a vehicle 18 so as to alternately transmit a circularly polarized wave and a linearly polarized wave. The system discriminates a reflecting object based on the ratio (PC/PL) of the receiving intensity PC of a circularly polarized wave received by means of the radar equipment 12 to that of a linearly polarized wave also received by means of the equipment 12. When the ratio PC/PL is sufficiently smaller than '1', the system discriminates that the reflecting object is an unnecessary reflecting body other than a lane marker 100 and, when the ratio PC/PL is sufficiently larger than '1', the system discriminates that the object is the marker 100. When the ratio PC/PL is nearly equal to '1', the system discriminates the object as a special object having a rugged surface and a noncoherent reflecting characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object detection apparatus and an object detection system, and more particularly to an object detection technique using circularly polarized light and linearly polarized light.

[0002]

2. Description of the Related Art Conventionally, a radio wave reflector that reflects an incident radio wave in an incident direction is used as a lane marker, and a lane is recognized by transmitting a radio wave from a radar device mounted on a vehicle and receiving a reflected radio wave from the lane marker. Techniques for doing so are known.

[0003] The lane marker has a characteristic of reflecting an incident circularly polarized wave as a circularly polarized wave (a circularly polarized wave whose polarization direction is the same turning direction) so that it can be distinguished from a reflector other than the lane marker. be able to. In other words, the reflected radio wave from a normal reflector is a reverse circularly polarized wave (a circularly polarized wave whose turning direction is opposite).
Therefore, the processing device mounted on the vehicle can detect only the lane marker in principle by distinguishing whether the received radio wave is the co-circular polarization or the counter-circular polarization.

[0004]

However, there are various objects on an actual road surface, and in addition to lane markers, there are also objects having extremely large reflection cross-sectional areas and objects having complicated reflection surface irregularities. In particular, in the case of an object having a large number of irregularities on the surface, the reflected radio wave does not have a specific plane of polarization, but becomes non-coherent having various polarization directions, and is not limited to reverse circularly polarized waves. It also includes concentric circular polarization. Therefore, in a configuration in which the receiving side simply receives only a circularly polarized wave having the same rotation as the transmission radio wave, there is a possibility that these objects are erroneously recognized as lane markers.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned problems of the related art, and has as its object to detect an object such as a lane marker which can be reliably detected from other objects and to detect the object. It is to provide an apparatus and a system.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to an object detection apparatus for detecting an object by transmitting a radio wave and receiving a reflected radio wave from the object, comprising: Transmitting and receiving means for alternately transmitting and receiving linearly polarized waves, and processing means for identifying an object based on a ratio of the received intensity in the circularly polarized waves and the received intensity in the linearly polarized waves from the transmitting and receiving means. I do. Reflecting objects include those that reflect circularly polarized light with concentric circular polarization, those that reflect with counter-rotated circular polarization, or those that include both; those that reflect linearly polarized light with the same polarization, and those that reflect orthogonally. There is a type that reflects with a polarized wave, and a type that includes both. Therefore, by calculating the combination of the reception intensities of the circular polarization and the linear polarization, specifically, the ratio of the two intensities, it is possible to identify what kind of reflection object is. By calculating the ratio of the reception intensity, it is necessary to strictly adjust the conditions of the circular polarization and the linear polarization as compared with a case where the values of the reception intensity of the circular polarization and the linear polarization are simply compared in magnitude. Can be compared without fail.

Based on the ratio, the processing means converts an object which reflects a circularly polarized wave to a circularly polarized wave, an object which reflects a circularly polarized wave against a circularly polarized wave, and a circularly polarized object. Objects that reflect incoherently to each other are distinguished from each other. An object that reflects circularly polarized waves with respect to circularly polarized waves reflects linearly polarized waves whose polarization planes are orthogonal to linearly polarized waves. Is greater than 1. An object that reflects a reverse circularly polarized wave with respect to a circularly polarized wave reflects a linearly polarized wave having the same plane of polarization with respect to a linearly polarized wave. Becomes smaller than 1. For objects having non-coherent reflection characteristics, both circularly polarized light and linearly polarized light include reflections having the same polarization plane (non-coherent means having various polarization planes). The reception intensity of the linearly polarized wave becomes approximately equal to 1. Therefore, they can be identified based on the ratio.

Further, the processing means can further identify the object based on the values of the reception intensity for the circular polarization and the reception intensity for the linear polarization. That is, two objects having substantially the same ratio, that is, the reception intensity of the circular polarization / the reception intensity of the linear polarization, are further identified based on the value of the reception intensity. As an example, in the case of an object having non-coherent reflection characteristics, an incoming radio wave is scattered, so that the reception intensity is extremely low as compared with the case of a reflector.

Further, the present invention provides a reflector provided on a road surface, which reflects an incident radio wave in an incident direction and reflects an incident circularly polarized wave with a circularly polarized wave; Transmitting and receiving means for alternately transmitting polarized waves and receiving the reflected radio wave, and processing means for detecting the reflector based on the ratio of the received intensity in the circular polarization and the received intensity in the linear polarization from the transmitting and receiving means. It is characterized by having. Since the object can be identified based on the ratio of the reception intensities, even if the reflector and an object other than the reflector are present, only the reflector can be detected. And by providing the reflector on the road surface,
It is possible to recognize the road surface itself.

[0010] The processing means further detects an object having non-coherent reflection characteristics other than a reflector, based on the values of the reception intensity in the circular polarization and the reception intensity in the linear polarization. An object having non-coherent reflection characteristics scatters an incident radio wave, so that the value of the reception intensity becomes small. Thus, by comparing not only the ratio but also the value of the reception intensity, it is possible to reliably detect an object having non-coherent reflection characteristics.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an object detection apparatus according to the present embodiment. The object detection device is
It is configured to include a processing device 10, a radar device 12, a polarizer 14, and a driving device 16.

The radar device 12 transmits a millimeter wave radio wave based on a control signal from the processing device 10, receives a reflected radio wave from an object, and supplies a received signal to the processing device 10. The transmission polarization plane and the reception polarization plane in the radar device 12 are the same.

The polarizer 14 is provided on the front of the radar device 12, and polarizes radio waves from the radar device 12 and radio waves reflected from an object. Specifically, it converts the linearly polarized wave from the radar device 12 into a circularly polarized wave or a linearly polarized wave, and converts the circularly or linearly polarized wave from the object into a linearly polarized wave. The polarizer 14 is driven to rotate by a driving device 16. By rotating the polarizer 14, the plane of polarization of the polarizer 14 can be changed to switch between circular polarization and linear polarization.

The driving device 16 drives the polarizer 14 to rotate based on a control signal from the processing device 10. As a driving method, the optical disk is rotationally driven to transmit circularly polarized waves for a predetermined time and receives circularly polarized waves from an object. Thereafter, it is driven to rotate so as to transmit linearly polarized waves for a predetermined time, and receives a reflected radio wave from an object. As a result, circularly polarized waves and linearly polarized waves are transmitted and received alternately at predetermined time intervals.

The processing device 10 calculates the ratio between the reception intensity of the circularly polarized wave and the linearly polarized wave received from the object received by the radar device 12, and identifies the reflected object based on the ratio. In the present embodiment, specifically, a lane marker that reflects a circularly polarized wave having the same turning direction as the transmitted circularly polarized wave, and reflects a reversely circularly polarized wave that has a rotating direction opposite to the transmitted circularly polarized wave. Other objects and special objects that reflect non-coherently the incoming radio waves.

FIG. 2 shows an example of a system configuration to which the object detection device of the present embodiment is applied. The object detection device shown in FIG. Radar device 1
The circularly polarized light or the linearly polarized light from the polarizer 2 and the polarizer 14 is transmitted toward the front of the vehicle with a ground angle of θ with respect to the horizontal plane.

Lane markers 100 are arranged at predetermined intervals on the road surface on which the vehicle travels. The radar device 12 receives the radio waves reflected by the lane markers 100 and receives signals from other objects other than the lane markers 100 on the road surface. The reflected radio waves are also received. By the processing described later, the processing device 10 mounted on the vehicle 18 detects only the reflected radio wave from the lane marker 100, and
The distance and the azimuth to 0 are detected. The detected distance and direction can be used for, for example, steering control of the vehicle 18.

The radio wave reflector used as the lane marker 100 can be constituted by providing a polarizer on the front surface of a well-known corner reflector (a reflector having two reflection surfaces orthogonal to each other). The lane marker 100 reflects an incident radio wave in the incident direction,
The circularly polarized wave is reflected as a circularly polarized wave. Of course, other reflectors, for example, three reflectors, may be used as the radio wave reflector, and one surface may be covered with an insulator so that the incident radio wave is incident at an angle larger than the Brewster angle. The installation height H of the radar device 12 is, for example, 0.6 m,
The distance L can be, for example, 10 m.

FIG. 3 shows a state in which a radio wave enters and reflects on an object (for example, a flat plate) other than the lane marker 100 when the object is present. In the figure,
(A) is a case where a circularly polarized wave is incident and reflected, and (B) is a case where a linearly polarized wave is incident and reflected. In the figure, the arrow indicates the polarization direction. As shown in (A), when the transmitted radio wave is circularly polarized, the radio wave reflected by the flat plate is the same circularly polarized wave, but its turning direction is the reverse circularly polarized wave whose direction is opposite to that of the transmitted radio wave. Becomes Since the polarization directions are opposite, the reception intensity PC1 at the radar device 12 becomes extremely small.

On the other hand, as shown in (B), when the transmitted radio wave is linearly polarized, the reflected radio wave is also linearly polarized having the same polarization direction. Since the polarization directions are the same, the reception intensity PL1 at the radar device 12 increases.

Therefore, the ratio of the reception intensities of (A) and (B), that is, the ratio PC1 / PL1 of the reception intensity PC1 of the circular polarization and the reception intensity PL1 of the linear polarization becomes sufficiently smaller than 1.

FIG. 4 shows how a radio wave enters and reflects on a special object having an uneven surface. (A) is a case where a circularly polarized wave is incident and reflected, and (B) is a case where a linearly polarized wave is incident and reflected. As shown in (A), when a circularly polarized wave is incident, the reflected radio wave does not have a fixed polarization direction but reflects non-coherent radio waves having various polarization directions due to the presence of irregularities on the surface. I do. Therefore, even when the incident radio wave is left circular polarization, the reflected radio wave includes both the co-circular polarization and the counter-circular polarization, and the co-polarization component is generated by the radar device 12. Will be received.

On the other hand, as shown in (B), even when linearly polarized waves are incident, the reflected radio waves are reflected as linearly polarized waves having various polarization directions, and the same polarization component is reflected by the radar. Received at device 12.

Therefore, both the reception intensity of the circularly polarized wave and the reception intensity of the linearly polarized wave have a constant magnitude, and (A)
(B), that is, the ratio PC2 / PL2 between the reception intensity PC2 of the circular polarization and the reception intensity PL2 of the linear polarization becomes substantially equal to 1. However, since the incident radio waves are scattered in various directions due to surface irregularities, the value of the received intensity itself is smaller than that of the flat object or the lane marker 100.

FIG. 5 shows how a radio wave enters the lane marker 100 and is reflected. In the figure,
(A) is a case where a circularly polarized wave is incident and reflected, and (B) is a case where a linearly polarized wave is incident and reflected. Lane marker 10
As an example of 0, an example in which the corner reflector 100a and the polarizer 100b are combined is shown. As described above, the reflector used as the lane marker 100 has a characteristic of reflecting an incident circularly polarized wave in the incident direction as a circularly polarized wave. Therefore, as shown in (A), for example, when a left circular polarized wave is incident, the reflected radio wave also becomes a left circular polarized wave of the same circularly polarized wave, and the radar device 12 receives the reflected radio wave.

On the other hand, as shown in (B), when the incident radio wave is a linearly polarized wave (for example, a vertically polarized wave), the reflected radio wave is the same as the incident radio wave because the lane marker 100 has the polarizer 100b. The orthogonal linear polarization (horizontal polarization) is not received by the radar device 12. Accordingly, the ratio of (A) and (B), that is, the ratio PC3 between the reception intensity PC3 of the circular polarization and the reception intensity PL3 of the linear polarization.
/ PL3 is much larger than 1.

As described above, when the object is a flat plate, the ratio PC1 / PL1 of the reception intensity between the circularly polarized wave and the linearly polarized wave is sufficiently smaller than 1, and the circularly polarized wave and the linearly polarized light of the object having non-coherent reflection characteristics are obtained. Since the ratio PC2 / PL2 of the wave reception intensity is almost equal to 1 and the ratio PC3 / PL3 of the reception intensity of the circular polarization and the linear polarization of the lane marker 100 is sufficiently larger than 1, the reception intensity of the circular polarization and the linear polarization is obtained. By comparing the ratios, it is possible to identify which of these is the reflective object.

FIG. 6 shows still another example in which two types of markers are mounted on a vehicle other than the vehicle 18 on which the object detection device is mounted. One of the two types of markers mounted is a marker 200 having a characteristic of reflecting an incident radio wave in the incident direction and reflecting a circularly polarized wave as a circularly polarized wave similarly to the lane marker 100, and the other is not having a polarizer. Therefore, the marker 220 has a characteristic of reflecting an incident radio wave in the incident direction but reflecting a circularly polarized wave as a reverse circularly polarized wave. In the figure, (A) shows a case where a circularly polarized wave enters the marker 200 and is reflected, (B)
Is a case where a linearly polarized wave enters the marker 220 and is reflected.

As shown in (A), since the marker 200 has the same characteristics as the lane marker 100, the marker 200 reflects a circularly polarized wave as a circularly polarized wave, receives the same with the radar device 12, and receives the received signal. PC4 has the same value as in the case of the lane marker 100. On the other hand, as shown in (B), since the marker 220 does not include the polarizer 100b, when linearly polarized light enters, the linearly polarized light in the same direction is reflected and received by the radar device 12. Therefore, the reception intensity PL4 in this case has a value equal to or higher than the linear polarization of the flat plate.

Therefore, in the case of FIG. 6, the ratio PC4 / PL4 of the reception intensity between the circularly polarized wave and the linearly polarized wave becomes substantially equal to 1, and the reception intensity from the object having the non-coherent reflection characteristic shown in FIG. Is equal to the ratio of This simply means that the reception intensity ratio PC / P between the circularly polarized wave and the linearly polarized wave is equal to PC / P.
Comparing only L means that an object having non-coherent reflection characteristics cannot be distinguished from other vehicles equipped with the markers 200 and 220.

However, in the case of an object having non-coherent reflection characteristics, the incident radio waves are scattered in various directions on the reflection surface as described above, so that the values of the reception intensities PC2 and PL2 are both small. Marker 200 shown
In the cases of and 220, since the incident radio waves are reflected in the incident direction, the reception intensities PC4 and PL4 are relatively large. Therefore, even if the ratio of the reception intensity is almost 1, by comparing the value of the reception intensity, it is determined whether the reflection object is the object having the non-coherent reflection characteristic or the marker 20.
It is possible to identify whether the vehicle has 0 and 220.

FIG. 7 shows a processing flowchart executed by the processing device 10 based on the above-described principle. First, the processing device 10 selects the circular polarization mode as the mode of the radio wave transmitted from the radar device 12,
6 to rotate the polarizer 14 to a predetermined position to transmit a circularly polarized wave from the radar device 12 (S
101). And receive the circularly polarized wave reflected from the object,
A target is extracted (S102).

Next, the processing device 10 selects the linear polarization mode, causes the radar device 12 to transmit linear polarization, and receives the reflected radio wave from the target (S103). And
The reception intensity (reception level) of the target extracted in the circular polarization mode is compared (S104). In particular,
A ratio PC / PL between the reception intensity PC of the circular polarization and the reception intensity PL of the linear polarization is calculated, and it is determined whether or not this ratio is sufficiently large, sufficiently small, or almost equal to 1. (S105). As a result of comparison, if PC / PL is sufficiently smaller than 1, this target is set to lane marker 1
It is identified as an unnecessary reflector other than 00 (for example, a flat plate) (S106, S107). Also, the ratio of the reception intensity PC /
When the PL is sufficiently larger than 1, this target is identified as the lane marker 100 (S108, S10).
9).

Also, the reception intensity ratio PC / PL is approximately 1
(S110), it is an unnecessary reflection object (an object having an uneven surface) having a non-coherent reflection characteristic in principle, but is distinguished from a vehicle equipped with the markers 200 and 220 as described above. In order to do, further receive strength PC
And PL are compared with a predetermined value Vth (S111). Note that the predetermined value Vth is preferably variable according to the distance to the target. This is because the reception intensity changes depending on the distance to the target. Then, as a result of the comparison, if the values PC and PL of the reception intensity are larger than the predetermined value Vth, it can be identified as another vehicle (for example, a bus) having the markers 200 and 220 (S113), and is equal to or smaller than the predetermined value. In this case, it is determined that scattering has occurred on the target surface, and the object is identified as an unnecessary reflector having non-coherent reflection characteristics (S112). This makes it possible to reliably detect the lane marker 100 or another vehicle that should be detected by identifying the object.

As described above, in the present embodiment, the unnecessary reflection object can be reliably distinguished from an object such as a lane marker which should be originally detected. The lane to be driven can be reliably detected. Further, in the present embodiment, since it is possible to further distinguish an object having non-coherent reflection characteristics from another vehicle equipped with a predetermined marker, it is possible to reliably recognize another vehicle regardless of the surrounding environment. Is also possible.

[0037]

According to the present invention, an object to be detected can be reliably distinguished from other unnecessary reflectors.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of an embodiment of the present invention.

FIG. 2 is a system configuration diagram of the embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating reflection characteristics of a flat object according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram of reflection of an object having non-coherent reflection characteristics according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram of reflection of a lane marker according to the embodiment of the present invention.

FIG. 6 is a reflection explanatory diagram of another vehicle equipped with two types of markers according to the embodiment of the present invention.

FIG. 7 is a processing flowchart in the embodiment of the present invention.

[Explanation of symbols]

10 processing device, 12 radar device, 14 polarizer, 16 drive device, 18 vehicle, 100 lane marker.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) G01S 13/91 Z (72) Inventor Yoshihide Kamisato 1-2-28 Goshodori, Hyogo-ku, Kobe City, Hyogo Prefecture F-term in Fujitsu Ten Limited (reference) 5H180 AA01 BB04 CC12 CC14 CC24 LL09 5H301 AA01 BB20 CC03 CC06 DD07 EE02 EE08 EE12 EE32 FF08 FF11 FF21 HH03 LL01 LL06 LL11 LL14 LL16 5J070 AB24 AC01 AD01 A33 AD16

Claims (5)

[Claims] 1. An object detection device for detecting an object by transmitting a radio wave and receiving a reflected radio wave from the object, comprising: a transmission / reception unit for alternately transmitting / receiving a circularly polarized wave and a linearly polarized wave; Processing means for identifying an object based on the ratio of the reception intensity of the circularly polarized wave to the reception intensity of the linearly polarized light from the object. 2. The apparatus according to claim 1, wherein the processing means reflects an object which reflects a circularly polarized light with respect to a circularly polarized wave, and an object which reflects a circularly polarized light with respect to the circularly polarized light based on the ratio. An object detection device, wherein an object that reflects a wave and an object that non-coherently reflects a circularly polarized wave are distinguished from each other. 3. The apparatus according to claim 1, wherein the processing unit further identifies an object based on a value of the reception intensity in the circular polarization and a value of the reception intensity in the linear polarization. An object detection device characterized by the above-mentioned. 4. A reflector provided on a road surface, which reflects an incident radio wave in an incident direction and reflects an incident circularly polarized wave with a circularly polarized wave, and alternates a circularly polarized wave and a linearly polarized wave with respect to the reflector. Transmitting and receiving means for receiving the reflected radio wave, and processing means for detecting the reflector based on the ratio of the reception intensity in the circular polarization and the reception intensity in the linear polarization from the transmission / reception means. An object detection system characterized by the following. 5. The system according to claim 4, wherein the processing unit further detects an object having a non-coherent reflection characteristic based on a value of the reception intensity in the circular polarization and a value of the reception intensity in the linear polarization. An object detection system, characterized in that: