Object detecting device

Details Object detecting device Object detecting device

1999-07-14

2001-05-08

Buczinski, Stephen C. (Department: 3662)

Optics: measuring and testing

Range or remote distance finding

With photodetection

C180S169000, C342S139000, C342S146000, C356S005010, C356S141100

Reexamination Certificate

active

06229597

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an object detecting device for detecting an object by transmitting an electromagnetic wave comprising a laser or a millimeter wave to the object and receiving the reflected wave thereof.
2. Description of the Related Art
FIG. 14
shows a prior art object detecting device for detecting the distance from a vehicle to another vehicle T traveling ahead of the vehicle (which will be referred to as a preceding vehicle) and the direction of the preceding vehicle. The prior art object detecting device is designed to detect the distance and direction of the preceding vehicle T by vertically and laterally scanning with an electromagnetic wave transmitted forwards from a radar device provided at a front portion of the vehicle V and receiving the wave reflected by the preceding vehicle T.
In the above prior art device, the electromagnetic wave transmitted forwards from the radar device is diffused radiantly. For this reason, the width of the area for detecting the preceding vehicle T is narrower at a location closer to the vehicle V and wider at a location farther from the vehicle V. For example, in an object detecting device having a maximum detecting distance of 100 m, if the width of an area equal to 0.8 m which is approximately one-half of the lateral width of the preceding vehicle T, is ensured at a location 100 m ahead of the vehicle V, the width of the area is as small as 0.08 m at a location 10 m ahead of the vehicle V and hence, the reflected wave cannot be received with the preceding vehicle defined as a lump of object. For this reason, when distance from the vehicle V to the preceding vehicle T is farther, the preceding vehicle T can be detected. However, when the distance becomes short, only the reflected wave from a portion of a vehicle body of the preceding vehicle T is received. If the reflection state of the electromagnetic wave reflected from such portion of the vehicle body is bad, there is a possibility that the preceding vehicle could not be detected.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an object detecting device, wherein an object can be reliably detected irrespective of the magnitude of a distance from the vehicle to the object.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided an object detecting device for detecting an object by transmitting an electromagnetic wave, and receiving a reflected wave produced by reflection of the electromagnetic wave from the object. The device comprises a transmitting and receiving means for conducting the transmission of an electromagnetic wave and the reception of the reflected wave in each of a plurality of small areas into which an area for detecting the object is divided, an adding means for adding signals indicative of reception levels of the reflected waves in a plurality of basic areas defined by grouping adjacent ones of the small areas each having a predetermined lateral width, in accordance with a time lag from the transmission to the reception of the waves, and object detecting means for detecting a distance from the object detecting device to the object, based on the result of addition by the adding means.
With the above arrangement, the plurality of basic areas are formed by grouping the adjacent smaller areas to establish the predetermined lateral width, and the distance from the vehicle to the object is detected based on the result of the addition of the reception level signals of the reflected waves in the basic areas in accordance with the time lag from the transmission to the reception of such waves. Therefore, it is possible to reliably detect the distance from the vehicle to the object irrespective of the magnitude of the distance by adding together the reception level signals from a sufficiently wide area which covers the entire object. Even when the reception level signals of the reflected waves in the small areas, are small because it is difficult for the object to reflect the electromagnetic wave, it is possible to reliably detect the object in the entire basic area comprising the plurality of small areas grouped together. Moreover, since the detection is carried out based on the added reception level signals of the reflected waves, the influence of the rain or snow at random distances to the reflected waves can be eliminated, whereby the distance from the vehicle to the object can be reliably detected.
The predetermined lateral width is set at 0.8 m in the disclosed embodiment, but such value is a matter of design, which may be changed as desired in accordance with the size of an object to be detected. In a first embodiment, a beam transmitting section
1
, a transmitted-beam scanning section
2
, a beam receiving section
3
and a received-beam scanning section
4
form the transmitting and receiving means. In a second embodiment, the beam transmitting section
1
, the transmitted-beam scanning section
2
, the beam receiving section
3
and a transmitted and received-beam scanning section
4
′ form the transmitting and receiving means.
According to a second aspect and feature of the present invention, the transmitting and receiving means transmits electromagnetic waves sequentially in a lateral direction, and the object detecting means detects a lateral position of the object based on the timing of transmission of the electromagnetic waves to the small areas.
With the above arrangement, the transmitting and receiving means transmits the electromagnetic waves sequentially in the lateral direction, and therefore, the lateral position of the object detected by the electromagnetic waves can be detected based on the timing of transmission of the electromagnetic waves by the transmitting and receiving means.
According to a third aspect and feature of the present invention, a plurality of detection areas are established by grouping adjacent ones of the plurality of basic areas together, and the adding means adds the signals indicative of reception levels of the reflected waves in the detection areas in accordance with the time lag from the transmission to the reception of such waves.
With the above arrangement, since the plurality of detection areas are established by grouping adjacent plurality of basic areas, the reception level signals of the reflected waves from the detection areas each having any area such as to cover an object depending on the size of the object, are added together, whereby the distance from the vehicle to the object can be reliably detected.
According to a fourth aspect and feature of the present invention, the object detecting means detects the lateral position of the object based on the lateral position of a detection area in which the object has been detected.
With the above arrangement, the lateral position of each of the detection areas is previously determined in accordance with the combination of the basic areas and hence, the lateral position of the object can be detected based on the lateral position of the detection area in which the object has been detected.
According to a fifth aspect and feature of the present invention, the plurality of detection areas are established in such a manner that the detection areas are overlapped by one half by sequentially grouping the adjacent two basic areas.
With the above arrangement, the plurality of detection areas are established in such a manner that they are overlapped by one half by sequentially grouping the adjacent two basic areas. Therefore, even when an object exists astride the two basic areas, the object can be reliably detected through the covering-up by any detection area.
According to a sixth aspect and feature of the present invention, the object detecting device is mounted on a vehicle to detect an object existing ahead of the vehicle in the direction of movement of the vehicle, and the lateral width of the detection area is set based on the lateral width of the vehicle or the width of a lane of the road on which the veh

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