Communications: electrical – Land vehicle alarms or indicators – Of relative distance from an obstacle
Reexamination Certificate
2001-06-28
2003-11-18
Tong, Nina (Department: 2632)
Communications: electrical
Land vehicle alarms or indicators
Of relative distance from an obstacle
C340S436000, C340S903000, C701S301000, C342S070000, C342S054000, C356S004010, C356S021000, C359S196100
Reexamination Certificate
active
06650235
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of recognizing an object.
In addition, this invention relates to an apparatus for recognizing an object which can be mounted on a vehicle. Furthermore, this invention relates to a recording medium storing a computer program for recognizing an object.
2. Description of the Related Art
A known object recognition apparatus for a vehicle emits a forward wave beam such as a light beam or a millimeter wave beam from the body of the vehicle, and enables the forward wave beam to scan a given angular region in front of the body of the vehicle. In the case where an object exists in the given angular region, the forward wave beam encounters the object before being at least partially reflected thereby. A portion of the reflected wave beam returns to the apparatus as an echo wave beam. The apparatus detects and recognizes the object in response to the echo wave beam.
The known object recognition apparatus is used in a warning system for a vehicle which alarms when an obstacle such as a preceding vehicle exists in a given angular region in front of the present vehicle. The known object recognition apparatus is used also in a system for a vehicle which controls the speed of the vehicle to maintain a proper distance between the vehicle and a preceding vehicle.
It is known to use a laser beam as a forward wave beam in an object recognition apparatus for a vehicle. In general, the front end of such an object recognition apparatus has a transparent member through which the forward laser beam travels. A waterdrop encounters the transparent member, changing into a lens-like shape thereon. In some cases, the forward laser beam is scattered when traveling through the lens-like shape of water on the transparent member. The scatter increases the cross-sectional area of the forward laser beam. An increase in the cross-sectional area of the forward laser beam reduces the resolution of detection of an object position and the accuracy of detection of an object size.
In general, a given angular region (a given object detectable area or a given detection area) in front of the body of the vehicle is scanned by the forward laser beam while the angular direction of the forward laser beam is sequentially changed among ones separated at equal unit angles. According to an example, in the absence of a lens-like shape of water from a surface of the transparent member, there occur detected echo beams for 5 successive angular directions of the forward laser beam. On the other hand, in the presence of a lens-like shape of water on the surface of the transparent member, there occur detected echo beams for 10 successive angular directions of the forward laser beam. In this case, a detected width of an object is equal to twice the actual width thereof.
The previously-mentioned scatter sometimes causes the forward laser beam to travel out of the detection area in front of the body of the vehicle. When such a forward laser beam encounters an object outside the detection area and is reflected thereby, an echo beam may return to the object recognition apparatus. On the basis of this echo beam, the apparatus erroneously recognizes the object outside the detection area as an object therein.
A member having a slit is used to narrow and make the cross section of a forward laser beam into an ideal shape. Diffraction at the slit causes an increased intensity of light in a peripheral portion of the beam, so that the shape of the cross section of the beam deviates from the ideal one. Therefore, the theoretical shape of the cross section of the forward laser beam which is used in an object recognition apparatus differs from the actual shape thereof. The difference between the theoretical shape and the actual shape causes a decrease in accuracy of object recognition by the apparatus.
Japanese patent application publication number P2000-180532A discloses a method of detecting an object position which is used in a scanning-type radar for a vehicle. The radar emits a millimeter wave beam. The method in Japanese application P2000-180532A is designed to implement the following process. In the case where there are a plurality of peaks of the power of a reflected beam and a plurality of mountains formed by the plurality of peaks, and where reflection due to a side lobe is included in the power of the reflected beam, a threshold is set to remove the power of the reflection due to the side lobe so that an angle at a width-wise center in angles defined by peaks of both ends among the remaining peaks is detected as a center position of an object.
U.S. Pat. No. 5,627,511 (corresponding to Japanese patent application publication number 8-122437) discloses a distance measuring apparatus for an automotive vehicle that compensates for the influence of particles floating in the air.
The apparatus of U.S. Pat. No. 5,627,511 outputs laser pulse signals at given angular intervals over an object detectable zone, and receives a signal produced by reflection of one of the outputted signals from a reflective object to determine the distance to the object. The apparatus has the function of determining a type of the object present in the object detectable zone. In the case where there are a plurality of signals produced by dispersion of a single shot of the laser pulse signals, and where distances derived by signals reflected from most of the object detectable zone show given shorter distance values, the object present in the object detectable zone is identified as a particle such as snow or fog floating in the air.
U.S. Pat. No. 4,699,507 (corresponding to Japanese patent application publication number 60-201276) discloses an apparatus and method for measuring the distance to a desired light-reflecting object. The apparatus and method in U.S. Pat. No. 4,699,507 are capable of recognizing erroneous measurements due to the presence of light-reflecting particles suspended in the air. The range of intensity of reflected light achievable by air-borne particles is previously stored. When the actual intensity of reflected light falls within the above-indicated range, the outputting of the measured distance to the light-reflecting object is inhibited.
U.S. Pat. No. 5,805,527 (corresponding to Japanese patent application publication number 9-236661) discloses a distance measuring apparatus which includes a wave transmitting device for emitting a transmission wave. The apparatus in U.S. Pat. No. 5,805,527 also includes a wave receiving device for receiving a reflection wave, which results from reflection of the transmission wave by a reflection object, as a reception wave. A time difference measuring device is operative for measuring a time difference between a moment at which the wave transmitting device emits the transmission wave and a moment at which the wave receiving device receives the reception wave. A distance calculating device is operative for calculating a distance to the reflection object on the basis of the time difference calculated by the time difference measuring device. An error correcting device is operative for detecting a time interval during which a signal level of the reception wave remains higher than a predetermined threshold level, and for correcting an error in the calculated distance to the reflection object on the basis of the detected time interval, the error being caused by a difference in intensity of the reception wave.
SUMMARY OF THE INVENTION
It is a first object of this invention to provide a method of accurately recognizing an object.
It is a second object of this invention to provide an apparatus for accurately recognizing an object.
It is a third object of this invention to provide a recording medium storing a computer program for accurately recognizing an object.
A first aspect of this invention provides a method of applying a transmission wave to a predetermined range in a width-wise direction of a subject vehicle, and recognizing objects located ahead of the subject vehicle on the basis of reflected waves which result from reflections of t
Matsuoka Keiji
Samukawa Yoshie
Shirai Noriaki
Denso Corporation
Posz & Bethards, PLC
Tong Nina
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