Obstacle detection device for vehicle
If the maximum time width Lt of the intensity of received light of reflected waves from a vehicle ahead is smaller than a reference time width, it is judged that the vehicle ahead is positioned in proximity to the detection limit distance of an obstacle detection device for vehicle. Thus, there is no problem, for example, even if a cut-in vehicle is present in reality between the vehicle ahead and the vehicle of interest and nevertheless, the distance to the cut-in vehicle cannot be detected. It can be judged whether the vehicle ahead is positioned in proximity to the detection limit distance of the device by judging the magnitude relation between Lt and the reference time width. As a result, the detecting capability of the device can be judged with accuracy.
1. An obstacle detection device for a vehicle comprising:
radar means which radiates transmitted waves outside the vehicle and detects reflected waves of the transmitted waves;
sensing means which senses a distance to an obstacle around the vehicle based on a result of detection of the reflected waves by the radar means;
determining means which determines a limit distance within which the sensing means is capable of sensing, wherein the determining means determines the limit distance based on a result of detection of reflected waves whose signal level is lower than a preset signal level; and
judging means which compares the limit distance determined by the determining means with a preset sensing reference distance and thereby judges an operating state of the device,
wherein the sensing means includes signal level judging means which judges a signal level of the reflected waves.
2. The obstacle detection device according to claim 1 ,
wherein the radar means radiates light waves and detects reflected waves of the radiated light waves,
wherein the signal level judging means judges a time width in which a voltage value corresponding to an intensity of light in the reflected waves is over a predetermined value, and
wherein the determining means determines the limit distance based on a result of detection of reflected waves whose time width is smaller than a preset reference time width.
3. The obstacle detection device according to claim 2 ,
wherein the determining means presets as the reference time width a time width in which a voltage value corresponding to an intensity of light in given reflected waves sensed by the sensing means is over the predetermined value, wherein the given reflected waves are reflected by an obstacle positioned in proximity to the limit distance.
4. The obstacle detection device according to claim 2 ,
wherein the sensing means recognizes a position of an obstacle as a segment formed of unified dots that gather adjacently, wherein the segment of unified dots are a subset of discontinuous dots that are obtained based on a result of detection of reflected waves, and
wherein the determining means determines the limit distance based on a result of detection of reflected waves of a given dot included in the segment, wherein the given dot has a time width in which the predetermined value is exceeded is largest among the dots included in the segment.
5. The obstacle detection device according to claim 1 ,
wherein when the limit distance becomes less than the preset sensing reference distance, the judging means judges that the device's capability to detect distances has degraded.
6. The obstacle detection device according to claim 1 ,
wherein, when the sensing means continuously senses a given obstacle for a predetermined time or longer after the sensing means senses the given obstacle for a first time, the determining means determines the limit distance based on a distance at which the sensing means senses the given obstacle for the first time.
7. The obstacle detection device according to claim 1 ,
wherein, when the sensing means continuously senses a certain obstacle for a predetermined time or longer and then becomes incapable of sensing the certain obstacle, the determining means determines the limit distance based on a distance at which the sensing means becomes incapable of sensing the certain obstacle.