JP5034809B2 - Vehicle road surface state estimating device - Google Patents

Description

  The present invention belongs to a technical field related to a vehicular road surface state estimation device that includes an imaging unit that captures an image of a traveling road surface of a vehicle and performs dry / wet determination on the traveling road surface based on an image captured by the imaging unit.

  Conventionally, as this kind of vehicle road surface state estimating device, there is provided a polarizing means disposed on the front side of the imaging means and capable of switching the polarization plane in both the horizontal and vertical directions, and the reflected light from the traveling road surface By comparing the horizontal polarization image and the vertical polarization image captured by the imaging unit by dividing the polarized light component into the horizontal polarization component and the vertical polarization component by the polarization unit, and determining the dryness and humidity on the road surface of the vehicle. What is known to do is known.

  For example, a vehicle road surface state estimation device disclosed in Patent Document 1 includes one television camera as an imaging unit, and a horizontal polarization filter and a vertical polarization filter (polarization unit) disposed on the optical axis of the television camera. The horizontal and vertical polarization filters are switched and set by the filter conversion unit (polarization means) for the television camera, so that a single television camera can capture both horizontal and vertical polarization images. It is possible.

The vehicle road surface state estimation device is caused by the fact that the light energy reflectance on the water surface is different between both horizontal and vertical polarization components in the wet road surface (in the state where moisture exists). Thus, the wet and dry determination of the traveling road surface is performed by utilizing the difference in brightness between both the horizontal and vertical polarization images captured by the television camera.
JP 2007-64888 A

  However, in the vehicle road surface state estimation device shown in Patent Document 1 described above, both a horizontally polarized image and a vertically polarized image are captured by a single television camera (imaging means). A control device such as a filter conversion unit for switching between the filter and the vertical polarization filter is required. As a result, the number of parts increases, the entire device becomes larger, and the processing for the switching control becomes complicated. is there.

  So, for example, the road surface of the vehicle is picked up by two television cameras, and the horizontal polarization filter and the vertical polarization filter are set in each camera, so that the control device such as the filter conversion unit is eliminated and controlled. Although it is conceivable to simplify the processing, even if it is done in this way, it is attempted to perform dry / wet determination on the traveling road surface based on the idea that the light component is divided into the horizontal component and the vertical component as described above. Therefore, polarizing means such as a horizontal polarizing filter and a vertical polarizing filter are necessary, and therefore there is still room for improvement in terms of reducing the number of parts and reducing the size of the entire apparatus.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a configuration and dry / wet determination for a vehicle road surface state estimation device including an imaging unit that images a road surface of a vehicle. By devising the method, it is intended to speed up the dry / wet determination process while reducing the size of the entire apparatus.

In concrete terms, in the first aspect of the present invention, directed to a vehicular road surface condition estimating apparatus for estimating the wet and dry state of the traveling road surface of the vehicle.

Then, the luminance information is obtained by imaging the traveling road surface of the vehicle with the first imaging unit and the second imaging unit that capture at least a part of the captured images, and the first and second imaging units, respectively. A predetermined area is set in an overlapping portion between the image information storage means for storing the first image and the second image composed of a plurality of pixels having the second image in the first image stored by the image information storage means. By comparing the first image and the second image stored by the predetermined area setting means and the image information storage means based on the luminance information of the pixels of each image, at least the predetermined area of the first image And detecting corresponding points with the second image and calculating the number of corresponding points in the detected predetermined area; and corresponding points in the predetermined area calculated by the corresponding point detecting means Based on応点number, and a wet and dry determination means for performing one of the dry-wet determined in any state of the road surface portion is dry and wet state corresponding to the predetermined region in the traveling road surface of the vehicle, the wet and dry determination means When the number of corresponding points calculated by the corresponding point detecting means is equal to or less than a predetermined threshold value set in advance, it is determined that the road surface portion corresponding to the predetermined area on the road surface of the vehicle is in a wet state. When the number of corresponding points exceeds the predetermined threshold, the wet and dry determination is performed to determine that the road surface portion is in a dry state.
The predetermined area setting means sets a plurality of the predetermined areas having different vertical coordinate values that are directions corresponding to the traveling direction of the vehicle in the first image with respect to the overlapping portion of the first image. The corresponding point detecting means detects a corresponding point with the second image in at least each predetermined area of the first image and calculates the number of corresponding points in each detected predetermined area. The dry / wet determination means is configured to make the dry / wet determination for each of the road surface portions corresponding to the predetermined areas on the traveling road surface of the vehicle, and the dry / wet determination means by the dry / humidity determination means. The predetermined threshold value used at the time of determination is set in advance for each predetermined area, and is set to a smaller value as the vertical coordinate value of each predetermined area is larger .

According to the above configuration, the traveling road surface of the vehicle is imaged by the first and second imaging units so that at least a part of the mutual imaging area overlaps, and the first and second image information storage units are used. A first image and a second image, each of which is picked up by the image pickup means and includes a plurality of pixels having luminance information, are stored. Then, the predetermined area is set by the predetermined area setting means in the overlapping portion of the first image stored in the image information storage means with the second image, and the corresponding point detection means sets the first image and the second image. By comparing the image with the luminance information of the pixels of each image, a corresponding point with the second image is detected in at least the predetermined area of the first image, and the detected predetermined area is detected. The corresponding number of points is calculated. Then, the dry / humidity determination means performs dry / humidity determination of the road surface portion corresponding to the predetermined area on the traveling road surface based on the number of corresponding points in the predetermined area calculated by the corresponding point detection means.

  By the way, when the traveling road surface is in a dry state, the reflected light reflected on the road surface is dominated by diffuse reflected light reflected with the same intensity in all directions, while the traveling road surface is in a wet state. Directive specularly reflected light is dominant. Therefore, when the traveling road surface is in a dry state, the intensity of the reflected light that is reflected on the road surface and is incident on each of the first and second imaging means is approximately the same intensity due to its diffusivity. The luminance difference (luminance distribution difference) between the first and second images picked up by the respective image pickup means is relatively small. On the other hand, when the traveling road surface is in a wet state, the intensity of the reflected light incident on each imaging means is different due to the directivity, and therefore, the luminance difference between the first and second images. Is larger than when the traveling road surface is in a dry state.

  Therefore, when the corresponding point detection means performs a corresponding point search (detection) by a matching method based on the luminance values of both the images, for example, the traveling road surface (the road surface portion corresponding to a predetermined region on the traveling road surface) is dry. Since the brightness difference between the two images is small when the vehicle is in a state, the matching accuracy can be improved and the corresponding points can be reliably detected. On the other hand, when the road surface is wet, the brightness difference between the two images is detected. Therefore, matching accuracy is lowered and it is difficult to detect corresponding points. For this reason, when the traveling road surface is in a dry state, the number of corresponding points detected by the corresponding point detection unit (the number of corresponding points calculated by the corresponding point detection unit) is compared to when the road surface is in a wet state. Will increase. Therefore, for example, when the number of corresponding points detected by the dry / wet determination unit exceeds the predetermined threshold, the traveling road surface can be determined to be dry, and otherwise, it can be determined to be wet. Thus, it is possible to easily and accurately perform the dry / wet determination on the traveling road surface.

  In addition, as described above, the wet / dry determination of the traveling road surface based on the number of corresponding points is performed by the dry / wet determination unit, and for example, the captured traveling road surface is divided into a horizontally polarized image and a vertically polarized image and processed. Compared to the case, a polarizing means such as a filter becomes unnecessary, and as a result, the number of parts can be reduced and the entire apparatus can be downsized. In addition, the switching process between the horizontally polarized image and the vertically polarized image can be abolished. For this reason, it is possible to reduce the control processing load of the entire apparatus, and from the imaging of the traveling road surface by both imaging means to the dry / wet determining means It is possible to shorten the processing time until the determination of the dry / wet determination result by.

Further , as described above, the number of corresponding points detected by the corresponding point detection means is larger when the traveling road surface is in a dry state than when it is in a wet state. If the number of corresponding points detected by the corresponding point detection means is less than or equal to a predetermined threshold value, the dry / wet determination means determines that the road surface portion corresponding to the predetermined area of the traveling road surface of the vehicle is in a wet state, and When the score exceeds the predetermined threshold value, it is determined by the dry / wet determining means that the road surface is in a dry state. Therefore, for example, in each case where the traveling road surface is in a dry state or in a wet state, the number of corresponding points detected by the corresponding point detecting means is obtained in advance through experiments or the like and detected in each case. By setting the intermediate value of the corresponding points to be the predetermined threshold value, it is possible to reliably perform the wet / dry determination by the dry / wet determination means with high accuracy.

The predetermined region setting means sets a plurality of the predetermined regions having different vertical coordinate values corresponding to the traveling direction of the vehicle in the first image for the overlapping portion of the first image. The The corresponding point detecting means detects corresponding points with the second image in at least each predetermined area of the first image, and calculates the number of corresponding points in each predetermined area. Then, the dry / wet determination means executes dry / wet determination based on the magnitude relationship between the number of corresponding points and the predetermined threshold as described above for each road surface portion corresponding to each predetermined region on the traveling road surface.

  By the way, in general, the resolution (resolution) of a subject imaged in an image is longer as the distance from the vehicle in the actual environment is longer, that is, the vertical coordinate value of the object to be imaged is larger in the image. It gets lower. For this reason, since the image resolution becomes lower as the predetermined area has a larger vertical coordinate value, the number of corresponding points detected by the corresponding point detecting means is also reduced. Therefore, the predetermined threshold value used when the wet / dry determination is performed by the dry / humidity determination unit is set with reference to, for example, a predetermined area where the vertical coordinate value is minimum (a predetermined area where the vehicle front distance in the actual environment is the shortest). Then, in other predetermined areas excluding the reference predetermined area, the image resolution is lower than that of the reference predetermined area, and the corresponding points are difficult to be detected by the corresponding point detecting means. As a result, the running road surface portion corresponding to each predetermined region excluding the reference predetermined region is wet by the dry / wet determination means when the detected number of corresponding points is equal to or less than the predetermined threshold value even though it is actually in a dry state. There is a problem that it is erroneously determined to be in a state, and as a result, the accuracy of wet / dry determination is reduced. However, according to the present invention, the predetermined threshold value is set to a smaller value in a predetermined region having a larger vertical coordinate value. Therefore, erroneous determination by the dry / wet determination unit is prevented, and the wet / dry determination accuracy is further increased. It becomes possible to improve.

According to a second aspect of the present invention, in the first aspect of the invention, the vehicle further includes vehicle speed detection means for detecting the speed of the vehicle, further includes vehicle speed detection means for detecting the speed of the vehicle, and the wet / dry determination by the dry / humidity determination means. It is assumed that the predetermined threshold used sometimes is set to a smaller value as the vehicle speed detected by the vehicle speed detecting means is higher.

  Thereby, it becomes possible to improve the dry / wet determination accuracy of the traveling road surface by the dry / wet determining unit more reliably.

  In other words, the vehicle vibration usually increases as the vehicle speed increases. For this reason, when the vehicle is traveling at high speed, image blurring occurs in the images picked up by the two image pickup means due to the vehicle vibration, and the image pickup accuracy is lowered. As a result, it becomes difficult to detect corresponding points by the corresponding point detecting means, and therefore, the number of detected corresponding points is predetermined even though the traveling road surface corresponding to the predetermined area is actually in a dry state. When the value is less than or equal to the threshold value, there is a problem that the wet / dry determination means erroneously determines that the wet state is present. However, according to the present invention, the vehicle speed detecting means for detecting the speed of the vehicle is provided, and the predetermined threshold value is set to a lower value as the vehicle speed detected by the vehicle speed detecting means is higher. For this reason, when the vehicle is traveling at high speed, it is possible to reliably prevent erroneous determination of the dry / wet determination means due to an increase in traveling vibration, thereby further improving the dry / wet determination accuracy.

According to a third aspect of the present invention, in the first aspect of the invention, the predetermined area setting means sets, as the predetermined area, a part of the image area corresponding to the traveling road surface of the vehicle in the overlapping portion of the first image. The corresponding point detecting means is configured to detect a corresponding point with the second image only in a predetermined region of the first image.

  According to this configuration, a part of the image area corresponding to the traveling road surface of the vehicle in the overlapping portion of the first image is set as the predetermined area by the predetermined area setting unit, and the corresponding point detecting unit Detection of corresponding points with the second image is executed only in a predetermined region of the first image.

  For this reason, it is possible to limit the search (detection) area of the corresponding points performed by the corresponding point detecting means to a part of the first image, and to reduce the processing load. It is possible to further shorten the time from the imaging of the traveling road surface by the determination of the wet / dry determination result by the dry / humidity determination means.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the overlapping portion of one of the first image and the second image stored in the image information storage unit with the other is the above. Luminance determination area setting means for setting an image area corresponding to the traveling road surface of the vehicle as a luminance determination area, and luminance information of each pixel of the first or second image in which the luminance determination area is set by the luminance determination area setting means Based on the above, the relationship between the luminance level in the luminance determination area of the set first or second image and the number of pixels corresponding to the luminance level is drawn on a biaxial graph to obtain a luminance distribution curve. A luminance distribution calculating means, wherein the dry / wet determining means has the dry distribution when the luminance distribution width at a predetermined ratio of the peak value of the number of pixels of the luminance distribution curve obtained by the luminance distribution calculating means is smaller than the predetermined width. While not executed the judgment, if the luminance distribution width is said predetermined fixed width or more is assumed to be configured to perform the determination humidity wherein the drying.

  According to this configuration, the brightness determination area setting means sets an image area corresponding to the traveling road surface of the vehicle as a brightness determination area with respect to an overlapping portion of one of the first image and the second image with the other. Based on the luminance information of each pixel of the first or second image in which the luminance determination area is set by the luminance determination area setting means by the luminance distribution calculation means, the set first or second The relationship between the luminance level and the number of pixels in the luminance determination area of the image is graphed to obtain a luminance distribution curve. And when the luminance distribution width at a predetermined ratio of the peak value of the number of pixels of the luminance distribution curve obtained by the luminance distribution calculating means is smaller than the predetermined width, the dry / humidity determination by the dry / humidity determining means is not executed, When the luminance distribution width is equal to or greater than the predetermined width, the dry / wet determination by the dry / wet determining unit is executed.

  By the way, the luminance distribution curve calculated by the luminance distribution calculating means is a graph showing the relationship between the luminance level of the image in the luminance determination region and the number of pixels as described above. Is a normal distribution with a peak value, but when the surroundings are relatively dark at dusk, rainy weather, etc., the image is picked up by each of the above imaging means compared to when the surroundings are relatively bright during the daytime, etc. Since the luminance value of the image is lowered as a whole, the luminance distribution curve has a peak value and a steeper curve than the low luminance.

  Therefore, for example, when the distribution width at a predetermined ratio of the peak value of the luminance distribution is smaller than the predetermined width, it can be estimated that the surrounding is relatively dark. In this case, because the surroundings are dark, the overall brightness of the captured images captured by the two imaging units is insufficient, resulting in a decrease in the corresponding point detection accuracy by the corresponding point detection unit, and thus a decrease in the wet / dry determination accuracy by the wet / dry determination unit However, the dry / humidity determination process is performed unnecessarily by the dry / humidity determination unit as in the present invention, so that the dry / humidity determination process is unnecessarily performed even though the dry / humidity determination accuracy of the dry / humidity determination unit is reduced. It is possible to prevent the processing load from increasing. On the other hand, when the distribution width at a predetermined ratio of the peak value of the luminance distribution is equal to or larger than the predetermined width, it can be estimated that the surrounding is relatively bright. In this case, since the detection accuracy of the corresponding points by the corresponding point detection means can be sufficiently ensured, the dry / humidity determination is ensured by executing the dry / humidity determination of the traveling road surface by the dry / humidity determination means as in the present invention. It can be performed with high accuracy, and the dry / wet determining means can be operated efficiently without waste.

According to a fifth aspect of the invention, in the first aspect of the invention, the corresponding point distribution calculating means for obtaining distance image data of each corresponding point in the predetermined area of the first image detected by the corresponding point detecting means, Road surface determining means for determining whether or not the object to be imaged projected on the image in the predetermined area of the first image is a traveling road surface based on the distance image data obtained by the corresponding point distribution calculating means, The determination unit performs the dry / wet determination when the object to be imaged is determined to be a traveling road surface by the road surface determination unit, while the dry / wet when the object to be imaged is determined not to be a traveling road surface. It is assumed that the determination is not executed.

  According to this configuration, distance image data of each corresponding point in the predetermined area of the first image detected by the corresponding point detecting unit is obtained by the corresponding point distribution calculating unit, and the corresponding point is obtained by the road surface determining unit. Based on the distance image data obtained by the distribution calculating means, it is determined whether or not the object to be imaged projected on the image in the predetermined area of the first image is a traveling road surface, and the object to be imaged is determined by the road surface determining means. Is determined to be a traveling road surface, the dry / humidity determination is performed by the dry / humidity determination unit, whereas when it is determined that the imaged object is not the traveling road surface, the dry / humidity determination is not performed by the dry / humidity determination unit. The

  As described above, when the object to be imaged in the predetermined area of the first image is determined not to be the traveling road surface by the road surface determination unit, the dry / humidity determination unit does not execute the dry / humidity determination. Although the imaged object is a preceding vehicle, it is possible to prevent the dry / wet determination from being performed by viewing the preceding vehicle as a traveling road surface. Therefore, it is possible to reliably reduce the processing load by preventing execution of unnecessary determination processing (determination processing performed even when the imaged object in the predetermined area is not a traveling road surface) by the dry / wet determination means. Become. On the other hand, when the object to be imaged in the predetermined area of the first image is determined not to be a traveling road surface by the road surface determination means, the dry / humidity determination means is executed by the dry / humidity determination means. Can be activated automatically.

As described above, according to the vehicle road surface state estimating device of the present invention, the first and second imaging means for imaging the traveling road surface of the vehicle, and a plurality of images having luminance information captured by the respective imaging means. The image information storage means for storing the first image and the second image made up of pixels, the predetermined area setting means for setting a predetermined area for the overlapping portion of the first image, and the first image and the second image are compared. Thus, a corresponding point with the second image is detected in at least a predetermined region of the first image, and a corresponding point detecting unit that calculates the number of corresponding points in the detected predetermined region, and the corresponding point detecting unit calculates Based on the number of corresponding points in the predetermined area, a dry / wet determination means for performing dry / wet determination on the road surface of the vehicle, wherein the dry / wet determination means sets the corresponding points calculated by the corresponding point detection means in advance. Specified threshold If it is below, it is determined that the road surface portion corresponding to the predetermined area on the road surface of the vehicle is in a wet state, while if the corresponding number of points exceeds the predetermined threshold, the road surface portion is The predetermined area setting means is in a direction corresponding to the traveling direction of the vehicle in the first image with respect to the overlapping portion of the first image. A plurality of the predetermined regions having different vertical coordinate values are set, and the corresponding point detecting means detects corresponding points with the second image in at least each predetermined region of the first image image. In addition, it is configured to calculate the corresponding points in each detected predetermined area, and the dry / wet determination means is configured to perform the above for each road surface portion corresponding to each predetermined area on the traveling road surface of the vehicle. The predetermined threshold value that is configured to perform humidity determination and is used when the wet / dry determination unit performs the dry / wet determination is set in advance for each of the predetermined areas, and the vertical coordinate value of each predetermined area by was so that is set to a smaller value the larger, it becomes possible to achieve faster dry-wet determination processing while reducing the size of the entire apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a vehicular road surface state estimating device 1 according to Embodiment 1 of the present invention. The vehicular road surface state estimating device 1 is mounted on a vehicle A (see FIG. 2) and is in a wet and dry state of its traveling road surface 20. And the determined wet / dry information of the road surface is transmitted to the skid prevention device 11 (hereinafter referred to as a DSC (Dynamic Stability Control) control device 11).

  Specifically, the vehicle road surface state estimation device 1 is imaged by a pair of left and right cameras (stereo cameras) 2R and 2L disposed on the ceiling of the front end of the vehicle, and the cameras 2R and 2L. ECU100 which performs various calculations based on an image is provided.

  Each of the cameras 2R and 2L is arranged with its optical axis directed in a predetermined direction so as to image the traveling road surface 20 in front of the vehicle so that the respective imaging regions (captured images) match (overlap). Thus, the left and right cameras 2R and 2L constitute a first imaging unit and a second imaging unit that respectively image the traveling road surface 20 of the vehicle A so that all of the captured images overlap each other. The entire left camera image GL as the first image captured by the camera 2L corresponds to the overlapping portion of the first image, and the entire right camera image GR as the second image captured by the right camera 2R is the second image. It corresponds to the overlapping part.

  Each camera 2R, 2L is configured by a digital camera having an image sensor such as a CCD (Charge coupled device), and transmits the captured image to the ECU 100 as an image signal.

  The ECU 100 includes a CPU, a ROM, a RAM, and the like. As shown in FIG. 1, the ECU 100 acquires a camera image acquisition unit 3, a luminance determination region setting unit 4, a luminance distribution calculation unit 5, and a dry / wet determination region setting unit. 6, a corresponding point detection unit 7, a road surface determination unit 8, a road surface wet / dry state determination unit 9, and a main control unit 10.

  The camera image acquisition unit 3 includes, for example, a frame memory having a plurality of RAMs. The camera image acquisition unit 3 receives (acquires) image signals transmitted from the cameras 2R and 2L, and captures images by the cameras 2R and 2L. The processed image is stored as digital image data.

  Specifically, the camera image acquisition unit 3 includes a right camera image acquisition unit 3R that stores the right camera image GR captured by the right camera 2R, and a left camera that stores the left camera image GL captured by the left camera 2L. The digital image data includes an image acquisition unit 3L, and the digital image data includes a coordinate position (x, y) on the image plane of each pixel constituting each camera image GR, GL, and a luminance value (luminance information) of each pixel. Consists of. Thus, the camera image acquisition unit 3 constitutes an image information storage unit that stores a first image and a second image each of which is captured by the first and second imaging units and has luminance information. It will be.

  The luminance determination area setting unit 4 receives a command from the main control unit 10 and reads the left camera image GL (digital image data of the left camera image GL) stored in the left camera image acquisition unit 3L and A luminance determination region R (see FIG. 4) is set for the camera image GL. The luminance determination region R is an image region for acquiring a luminance distribution necessary for determining whether to perform the wet / dry determination by the road surface wet / dry state determination unit 9 as will be described later. The brightness determination area setting unit 4 performs white line recognition processing on the left and right of the traveling road surface 20 (travel lane) based on the brightness information (the brightness value of each pixel) on the left camera image GL. An area sandwiched between both white lines is set as the luminance determination area R. Thus, the luminance determination area setting unit 4 constitutes a luminance determination area setting means.

  The luminance distribution calculation unit 5 (luminance distribution calculation means) receives a command from the main control unit 10 and the luminance distribution in the luminance determination region R set for the left camera image GL by the luminance determination region setting unit 4. Find a curve. Specifically, the luminance distribution calculation unit 5 creates a luminance distribution curve by classifying each pixel in the luminance determination region R for each of a plurality of preset luminance levels and calculating the number thereof. Thus, the luminance distribution curve created by the luminance distribution calculation unit 5 is normally a normal distribution having a peak portion as shown in FIG. L1 indicated by a broken line in the figure indicates the luminance distribution in a relatively dark state at night, and the peak portion has a lower luminance than the solid line L2 indicating the luminance distribution in a relatively bright daytime state. Further, the distribution width is narrower, and the mountain is steep as a whole.

  The dry / wet determination area setting unit 6 (predetermined area setting means) receives a command from the main control unit 10 and sets a dry / wet determination area Q (see FIG. 4) for the left camera image GL. The wet / dry determination area Q is an area that is set in order to perform dry / humidity determination of the traveling road surface 20 by the road surface wet / dry condition determination unit 9 as will be described later. In the present embodiment, the dry / wet determination area setting unit 6 includes: After identifying the region R (luminance determination region R) sandwiched between the left and right white lines of the traveling road surface 20 (travel lane) in the left camera image GL, the dry / wet determination region Q (see FIG. 4) is set in the region R. It is supposed to be. More specifically, the dry / wet determination area setting unit 6 determines that the forward distance from the vehicle A in the actual environment is within a predetermined distance among the images in the area R of the left camera image GL (in this embodiment, within 10 m). Is determined as a dry / wet determination region Q. Thus, the dry / wet determination area setting unit 6 constitutes a predetermined area setting means.

  The corresponding point detection unit 7 (corresponding point detection means) receives a command from the main control unit 10 and corresponds points included in the dry / wet determination region Q of the left camera image GL set by the dry / wet determination region setting unit 6. Are detected (searched) and the number is counted (calculated).

  Here, the corresponding points are points that are associated with each other between the left and right camera images GL and GR, and the detection of the corresponding points by the corresponding point detection unit 7 is an area method that is a known method in the present embodiment. This is done based on a -based matching method. In the area-based matching method, when searching for a corresponding point of a point in one image from the other image, a local luminance value (density) pattern around that point is searched for. . Specifically, as shown in FIG. 5, the corresponding point detection unit 7 sets a 3 × 3 pixel window around one pixel of the left camera image GL, and displays an image surrounded by the window as a template image GT. As described above, matching is performed within the search range GS set on the epipolar line EL of the right camera image GR. In the present embodiment, this matching process is performed on all the pixels of the left camera image GL, and an SAD algorithm (Sum of Absolute Difference) is adopted as an algorithm used for this matching. That is, the corresponding point detection unit 7 calculates the total value (SAD value) of the luminance difference between corresponding pixels between the template image GT set in the left camera image GL and the image in the right camera image GR to be matched. ) Is calculated by the following equation (1), and when the total value is less than or equal to a predetermined value, the corresponding point is detected and the coordinates on the image plane are stored. Then, the corresponding point detection unit 7 calculates the number of corresponding points included in the dry / wet determination region Q based on the coordinate information of each corresponding point. The algorithm used for the matching is not limited to the SAD algorithm. For example, an SSD (Sum of Squared Difference) algorithm or an NCC (Normalized Cross Correlation) algorithm may be used.

(1)
M _L : Luminance value of the pixel of the left image M _R : Luminance value of the pixel of the right image

  The road surface determination unit 8 receives a command from the main control unit 10, and based on the luminance distribution calculated by the luminance distribution calculation unit 5, the road surface determination unit 8 is projected in the dry / wet determination region Q of the left camera image GL. Road surface determination for determining whether the imaged object is the traveling road surface 20 is executed.

  Specifically, the road surface determination process in the road surface determination unit 8 is performed as follows, for example. First, a process for obtaining distance information according to the principle of triangulation based on the positional deviation amount (parallax) between the left and right camera images GL and GR of the corresponding point detected by the corresponding point detection unit 7 is performed. Distance image data (refer to FIG. 6 and FIG. 7) representing the three-dimensional distribution of corresponding points, that is, position information of each corresponding point in the vehicle width direction and forward distance information from the vehicle A is generated. Then, based on the distance image data, the corresponding point included in the center position in the vehicle width direction (position corresponding to the center pixel row in the x direction of the left camera image GL) Is plotted on a graph with y-coordinate on the image plane to create a distribution map (see FIG. 8). Then, the lower limit line UL corresponding to the ground surface of the traveling road surface 20 is obtained based on the created corresponding point distribution map. In this figure, the corresponding point distribution when the imaged object is a preceding vehicle traveling in front of the vehicle is shown, and a portion corresponding to the preceding vehicle appears as a peak portion V. Further, after obtaining a parallel line PL that is separated from the specified lower limit line by a predetermined distance (distance on the image plane), the correspondence is located in a plane including the parallel line PL (in a plane perpendicular to the paper surface). The density distribution of points is obtained (see FIG. 9).

  Specifically, the road surface determination unit 8 sets the corresponding point density at each position in the vehicle width direction (each x coordinate of the left camera image) for each of the vehicle front distance ranges D1 to D4 (for each vehicle front distance). To calculate. When the calculated corresponding point density is uniform in the vehicle width direction as shown in FIG. 9 (for example, the corresponding point density in each vehicle forward distance range D1 to D4 in the vehicle width direction). When all the change rates of the images are equal to or less than a predetermined value), it is determined that the object to be imaged is the traveling road surface 20. On the other hand, when the corresponding point density is not uniform in the vehicle width direction, the object to be imaged is determined. It is determined that the object is not the traveling road surface 20 (for example, a preceding vehicle or an obstacle). Thus, the road surface determination unit 8 constitutes corresponding point distribution calculation means and road surface determination means.

  When the road surface determination unit 8 determines that the object to be imaged is the traveling road surface 20, the road surface wet / dry state determination unit 9 (dry / humidity determination unit) corresponds to the road surface corresponding to the dry / wet determination region Q on the traveling road surface 20. The part 20a (see FIG. 2; hereinafter referred to as the dry / wet determination road surface part 20a) performs dry / wet determination as to whether it is in a wet state or a dry state. Specifically, the road surface dry / wet state determination unit 9 determines the travel road surface of the vehicle A when the number of corresponding points counted (calculated) by the corresponding point detection unit 7 is equal to or less than a predetermined threshold value set in advance. On the other hand, when the dry / wet determination road surface portion 20a in 20 is determined to be in a wet state, if the number of the corresponding points exceeds the predetermined threshold value, it is determined that the road surface portion 20a is in a dry state. And the road surface wet / dry state determination part 9 memorize | stores the result of the performed dry / wet determination until the next dry / wet determination execution time. Here, the predetermined threshold value is a value set based on an experiment or the like in the design stage, and is a value determined by the camera characteristics of both cameras 2R and 2L. Specifically, in the present embodiment, the number of corresponding points detected by the corresponding point detection unit 7 in each case where the traveling road surface 20 is in a dry state and in a wet state is obtained in advance through experiments or the like. Then, after sampling average, the intermediate value of the sampling average value of the number of corresponding points detected in each case is set as the predetermined threshold.

  Further, when the road surface determination unit 8 determines that the object to be imaged is not the traveling road surface 20, the road surface wet / dry state determination unit 9 does not perform the wet / dry determination of the wet / dry determination road surface part 20 a of the traveling road surface 20. It is like that. Then, the road surface wet / dry state determination unit constitutes a dry / wet determination unit.

  The main control unit 10 executes a series of dry / humidity determination control processes for determining the dry / wet state of the traveling road surface 20 by controlling the processing operations of the components 2 to 9 constituting the ECU 100.

  Specifically, the dry / wet determination control process executed by the main controller 10 of the ECU 100 will be described with reference to the flowchart of FIG.

  In the first step S1, the right camera image acquisition unit 3R is instructed to receive an image signal from the right camera 2R, and similarly, the left camera image acquisition unit 3L receives an image from the left camera 2L. Command to receive signal.

  In step S2, the luminance determination area setting unit 4 is instructed to read the left camera image GL stored in the left camera image acquisition unit 3L, and the luminance determination area R is set in the read left camera image GL. Command to set.

  In step S3, a command is issued to the luminance distribution calculation unit 5 to calculate the luminance distribution in the luminance determination region R of the left camera image GL set in step S2.

  In step S4, based on the luminance distribution calculated in step S3, distribution widths B1 and B2 at a predetermined ratio (for example, 50% in this embodiment) of the peak values W1 and W2 (see FIG. 3) of the distribution are obtained. It is determined whether or not the width is equal to or greater than the predetermined width. If this determination is YES, the process proceeds to step S5, and if NO, the process proceeds to step S12. It can be said that this predetermined width is a threshold width that divides whether or not the surrounding brightness satisfies the brightness required for the dry / wet determination in the road surface wet / dry state determination unit 9.

  In step S5, a command is issued to the dry / wet determination area setting unit 6 to set the dry / wet determination area Q in the left camera image GL.

  In step S6, the corresponding point detection unit 7 is instructed to detect (search) corresponding points in the dry / wet determination region Q of the left camera image GL set in step S5 and to calculate the number thereof.

  In step S7, it is determined whether or not a corresponding point is detected in step S6. If this determination is YES, the process proceeds to step S8, and if NO, the process proceeds to step S11.

  In step S8, a command is issued to the road surface determination unit 8 to determine whether the object to be imaged in the dry / wet determination region Q of the left camera image GL is the traveling road surface 20, and the determination by the road surface determination unit 8 is YES. If YES, the process proceeds to step S9. If NO, the process proceeds to step S12.

  In step S9, the road surface dry / wet state determination unit 9 should determine whether or not the number of corresponding points in each dry / wet determination region Q of the left camera image GL calculated in step S6 exceeds the predetermined threshold ( A wet / dry determination command is issued (in order to execute dry / wet determination). If the determination by the road surface wet / dry state determination unit 9 is YES, the process proceeds to step S10. If NO, the process proceeds to step S12.

  In step S10, the road surface dry / wet state determination unit 9 determines that the dry / wet determination road surface portion 20a of the traveling road surface 20 is in a dry state, and the road surface dry / wet state determination unit 9 determines whether the road surface dry / wet state is dry or wet. A command is issued to transmit information (information indicating that the dry / wet determination road surface portion 20a of the traveling road surface 20 is in a dry state) to the DSC control device 11.

  In step S11, the road surface wet / dry condition determination unit 9 determines that the wet / dry determination road surface part 20a of the traveling road surface 20 is in a wet state, and the road surface wet / dry condition determination unit 9 determines whether the road surface wet / dry condition determination unit 9 is wet or dry. A command is issued to transmit information (information indicating that the dry / wet determination road surface portion 20a of the traveling road surface 20 is in a wet state) to the DSC control device 11. The road dry / wet state determination unit 9 stores the result of the executed wet / dry determination until the next dry / humidity determination is executed, that is, until the process of step S9 is executed again.

  In step S12, the determination unit 9 transmits the wet / dry information of the traveling road surface 20 (information indicating that the wet / dry determination road surface part 20a of the traveling road surface 20 is in a dry / wet state or a wet state) to the DSC control device 11. The command is issued.

  As described above, in the first embodiment, the road surface wet / dry state determination unit 9 of the ECU 100 is based on the number of corresponding points in the dry / wet determination region Q calculated by the corresponding point detection unit 7 on the traveling road surface 20 of the vehicle A. The dry / wet determination road surface portion 20a determines whether the wet / dry state is in a wet state or a dry state. More specifically, the road dry / wet state determination unit 9 receives a command from the main control unit 10, and a predetermined threshold value in which the number of corresponding points counted (calculated) by the corresponding point detection unit 7 is set in advance. In the case of the following (when the determination in step S9 is NO), it is determined that the wet / dry determination road surface portion 20a of the traveling road surface 20 of the vehicle A is in a wet state, while the number of the corresponding points exceeds the predetermined threshold value. When it exceeds (when determination of step S9 is YES), it determines with this road surface part 20a being in a dry state. In this way, the wet / dry determination of the dry / wet determination road surface portion 20a on the traveling road surface 20 can be performed easily and accurately by the road surface wet / dry state determination unit 9. That is, when the wet and dry determination road surface portion 20a of the traveling road surface 20 is in a dry state, as shown in FIG. 11, the reflected light reflected on the road surface is dominated by the diffuse reflected light reflected with the same intensity in all directions. As shown in FIG. 12, when the traveling road surface is wet, the reflected light reflected on the road surface is directional. A certain specular reflection light becomes dominant and enters each of the cameras 2R and 2L with different intensities. Therefore, when the wet and dry determination road surface portion 20a of the traveling road surface 20 is in a dry state, the luminance difference (luminance distribution difference) between the left and right camera images GL and GR captured by the cameras 2R and 2L is the road surface. This is smaller than when the portion 20a is in a wet state. Here, in the first embodiment, the corresponding point detection unit 7 performs corresponding point search (detection) by an area-based matching method based on the luminance values of both the images GL and GR. When the dry / wet determination road surface portion 20a of the traveling road surface 20 is in a dry state, the difference in luminance between the two images GR and GL is reduced as described above, so that the road surface portion 20a is more wet than when the road surface portion 20a is in a wet state. Can be detected (see FIGS. 6 and 7). Therefore, for example, the predetermined threshold value is set to an intermediate value of the sampling average value of the corresponding points detected in each case where the traveling road surface 20 is in a dry state and a wet state as in the first embodiment. Thus, it is possible to easily and accurately determine the wet and dry state of the traveling road surface 20 (dry and wet determination road surface portion 20a) based on the magnitude relationship between the predetermined threshold value and the number of corresponding points.

  In addition, for example, when the wet / dry determination of the road surface 20a is performed by separately processing the image of the dry / wet determination road surface 20a of the traveling road surface 20 captured by a camera or the like into a horizontally polarized image and a vertically polarized image. In comparison, a polarizing means such as a filter becomes unnecessary, and as a result, the number of parts can be reduced and the entire apparatus can be downsized. In addition, processing such as switching processing between the horizontally polarized image and the vertically polarized image can be abolished, and therefore, the control processing burden on the entire apparatus 1 can be reduced. As a result, the road surface of the two cameras 2R and 2L can be reduced. Processing time from imaging 20 to determination of the dry / wet determination result by the road surface wet / dry state determination unit 9 (the time from the execution of the process of step S1 to the completion of the process of step S10 or 11; (Referred to as processing time). Accordingly, the wet / dry information of the dry / wet determination road surface portion 20a of the travel road surface 20 can be quickly transmitted to the DSC control device 11, and the travel control of the vehicle A by the DSC can be performed quickly. Therefore, it is possible to improve the running stability of the vehicle A.

  In the first embodiment, the main control unit 10 uses the luminance distribution calculated by the luminance distribution calculation unit 5 (the luminance distribution calculated in step S3) to obtain the peak values W1 and W2 of the distribution. It is determined whether or not the distribution widths B1 and B2 (see FIG. 3) at a predetermined ratio (for example, 50% in the present embodiment) are equal to or larger than the predetermined width (execution of step S4). When it is determined that the width is less than the predetermined width (when the determination in step S4 is NO), the flow proceeds to step S12 without executing the wet / dry determination by the road surface wet / dry state determination unit 9, and the previous determination result is used as the current traveling road surface. The dry / wet state of the 20 wet / dry determination road surface portion 20a is estimated. That is, the road surface dry / wet state determination unit 9 determines that the distribution widths B1 and B2 at a predetermined ratio of the peak values W1 and W2 of the luminance distribution in the luminance determination region R of the left camera image GL are smaller than the predetermined width (FIG. 3). In other words, when the surroundings are relatively dark, the wet / dry determination of the dry / humidity determination road surface portion 20a of the traveling road surface 20 is not executed.

  Thus, in a situation where the brightness of both images GL and GR captured by both cameras 2R and 2L is reduced because the surroundings are relatively dark, the corresponding point detection accuracy by the corresponding point detection unit 7 due to the lowering of the brightness. In spite of the decrease, the road surface wet / dry condition determination unit 9 prevents the determination of the dry / wet based on the number of corresponding points and making an erroneous determination (the determination accuracy is significantly reduced). can do. Further, it is possible to prevent unnecessary processing by the road surface wet / dry condition determination unit 9 (determination processing performed despite the extremely low determination accuracy) and reduce the processing load.

  In the first embodiment, the main control unit 10 determines that the distribution widths B1 and B2 at a predetermined ratio of the luminance distribution calculated by the luminance distribution calculation unit 5 (the luminance distribution calculated in step S3) are the predetermined width. When it determines with it being above (when determination of step S4 is YES), the corresponding point in the dry / wet determination area | region Q of the left camera image GL is detected in the corresponding point detection part 7 (determination of step S7 is YES) And when the predetermined condition is met when the road surface determination unit 8 determines that the object to be imaged in the dry / wet determination region Q is the traveling road surface 20 (when the determination in step S8 is YES), the road surface wet / dry state determination is performed. A command is issued to the unit 9 to execute dry / wet determination (the process of step S9 is executed). That is, the road dry / wet state determination unit 9 determines that the distribution widths B1 and B2 at a predetermined ratio of the peak values W1 and W2 of the luminance distribution in the luminance determination region R of the left camera image GL are equal to or larger than the predetermined width (solid line in FIG. 3). In other words, when the surroundings are relatively bright, the wet / dry determination of the dry / wet determination road surface portion 20a of the traveling road surface 20 is executed. Thus, when the brightness required for the dry / wet determination in the road surface wet / dry state determination unit 9 (detection of corresponding points in the corresponding point detection unit 7) is sufficiently ensured, the road surface dry / wet state determination is performed as described above. By executing the dry / wet determination of the traveling road surface 20 by the unit 9, the road dry / wet state determination unit 9 is efficiently operated without waste, and effective use of hardware resources such as a CPU constituting the determination unit 9 is achieved. It becomes possible.

  In the first embodiment, the road surface wet / dry state determination unit 9 determines that the object to be imaged projected in the dry / wet determination region Q of the left camera image GL by the road surface determination unit 8 is the traveling road surface 20. If it is determined (if the determination in step S8 is YES), the dry / wet determination (process in step S9) is executed.

  As a result, the road surface wet / dry state determination unit 9 does not detect the object to be imaged in the dry / humidity determination region Q of the left camera image GL, even though it is a preceding vehicle (inappropriate as an object for dry / wet determination). It is possible to prevent the dry / wet determination from being performed by viewing the preceding vehicle as the traveling road surface 20. Therefore, it is possible to prevent erroneous determination by the road surface dry / wet state determination unit 9 and to improve the determination accuracy. In addition, it is possible to prevent unnecessary processing by the road surface wet / dry state determination unit 9 and reduce the processing load.

  Moreover, in the said Embodiment 1, the said road surface wet / dry state determination part 9 will be the above-mentioned when the road surface determination part 8 determines that this to-be-photographed object is not the driving | running | working road surface 20 (when determination of step S8 is NO). Dry / wet determination (the process of step S9) is not performed.

  As a result, when the object to be imaged in the dry / humidity determination area Q of the left camera image GL is appropriate as a determination target, that is, the traveling road surface 20, the road surface / humidity determination unit 9 reliably executes the dry / humidity determination. Thus, the road surface dry / wet state determination unit 9 can be efficiently operated without waste. Therefore, it is possible to effectively use the hardware resources and the like constituting the road surface wet / dry condition determination unit 9.

  In the first embodiment, when the distribution of the corresponding point density calculated by the corresponding point detection unit 7 is uniform in the vehicle width direction, the road surface determination unit 8 determines whether the left camera image GL is wet or dry. While it is determined that the imaged object projected in the determination area Q is the traveling road surface 20, it is determined that the imaged object is not the traveling road surface 20 if it is not uniform.

  By doing so, it is possible to easily and reliably determine whether or not the object to be imaged is the traveling road surface 20 by the road surface determination unit 8.

(Embodiment 2)
FIGS. 13 and 14 show the second embodiment of the present invention. In the wet / dry determination area setting unit 6 of the ECU 100, the number of the dry / humidity determination areas Q set for the left camera image GL and the road wet / dry condition determination unit 9 are shown. Thus, the predetermined threshold used when performing dry / wet determination on the traveling road surface 20 (dry / wet determination road surface portion 20a) is different from that of the first embodiment. In addition, the whole structure (refer FIG. 1) etc. of the road surface state estimation apparatus 1 for vehicles are the same as that of the said Embodiment 1. FIG.

  That is, in the present embodiment, the dry / wet determination region setting unit 6 receives a command from the main control unit 10 and displays a region R sandwiched between the left and right white lines of the traveling road surface 20 (traveling lane) in the left camera image GL. After the identification, a plurality of dry / wet determination areas Q1 to Q8 (see FIG. 13) having different forward distance information from the vehicle A are set in the area R. Specifically, the wet / dry determination area setting unit 6 divides the image in the area R of the left camera image GL into eight areas in the y direction (vertical direction), and each of the divided areas is determined as the dry / humidity determination area Q1. To Q8. The dry / wet determination areas Q1 to Q8 set in this manner have different y-direction positions (coordinate values in the y-direction), and therefore have different vehicle front distance information. In the present embodiment, the number of dry / wet determination regions Q1 to Q8 set by the dry / wet determination region setting unit 6 is eight, but this is not limitative.

  Then, the corresponding point detection unit 7 counts (calculates) the number of corresponding points included in each of the eight dry / wet determination regions Q1 to Q8 set by the dry / wet determination region setting unit 6.

  In addition, the road surface determination unit 8 uses the same method as in the first embodiment, and the object to be imaged in each of the determination regions Q1 to Q8 is the traveling road surface 20 for each of the eight dry / wet determination regions Q1 to Q8. It is determined whether or not there is.

  The road surface wet / dry state determination unit 9 performs dry / humidity determination only on the dry / wet determination regions Q1 to Q8 in which the road surface determination unit 8 determines that the object to be imaged is the traveling road surface 20. Specifically, the dry / wet determination process by the road surface wet / dry state determination unit 9 is performed based on the magnitude relationship between the number of corresponding points included in each of the dry / wet determination regions Q1 to Q8 and the predetermined threshold, as in the first embodiment. However, in the present embodiment, as shown in FIG. 14, the predetermined threshold value is set for each of the wet and dry determination areas Q1 to Q8 having the front distance information with a long distance from the vehicle A for each of the dry and wet determination areas Q1 to Q8. That is, the wet / dry determination regions Q1 to Q8 having a large coordinate value in the y direction are set in advance so as to have a smaller value. The road surface wet / dry state determination unit 9 then determines the dry / humidity determination road surface part 20a corresponding to the dry / wet determination regions Q1 to Q8 in which the number of corresponding points detected by the corresponding point detection unit 7 exceeds the predetermined threshold. On the other hand, for the dry / wet determination areas Q1 to Q8 where the corresponding number of points is equal to or less than the predetermined threshold, it is determined that the corresponding wet / dry determination road surface portion 20a is in a wet state. Therefore, for example, when the relationship between the number of corresponding points detected by the corresponding point detection unit 7 and the predetermined threshold value is as in the example shown in FIG. 14, the road surface wet / dry state determination unit 9 It is determined that the wet and dry determination road surface portion 20a corresponding to Q1 and Q2 is in a wet state, and it is determined that the dry and wet determination road surface portion 20a corresponding to the dry and wet determination regions Q3 to Q8 is in a dry state.

  The road surface wet / dry state determination unit 9 does not perform the dry / wet determination on the dry / wet determination regions Q1 to Q8 determined by the road surface determination unit 8 that the object to be imaged is not the traveling road surface 20. .

  Regarding the dry / wet determination control process executed by the main control unit 10 of the ECU 100, a plurality of (eight) dry / wet determination regions Q1 to Q8 are set for the left camera image GL in step S5 of FIG. And the point that the control process of steps S6 to S12 is performed on each of the dry / wet determination regions Q1 to Q8 is only different from the first embodiment, and the other processes are the same as in the first embodiment. The description is omitted here.

  As described above, in the second embodiment, the dry / wet determination area setting unit 6 of the ECU 100 performs y for the left camera image GL (in the area R sandwiched between the left and right white lines of the traveling road surface 20 in the left camera image GL). A plurality of (eight) dry / wet determination areas Q1 to Q8 (see FIG. 13) having different direction coordinate values (different forward distance information from the vehicle A) are set. The predetermined threshold value used when the wet / dry determination is performed by the road surface wet / dry state determination unit 9 (during the process of step S9) has a large coordinate value in the y direction (having long forward distance information from the vehicle A). Regions Q1 to Q8 have smaller values (see FIG. 14).

  As a result, the road surface dry / wet state determination unit 9 can reliably and accurately perform the dry / wet determination of the dry / wet determination road surface 20a of the traveling road surface 20 according to the distance from the vehicle A.

  That is, in general, the resolution (resolution) of the subject imaged in the image becomes lower as the forward distance from the vehicle A in the actual environment becomes longer, and therefore the wet / dry determination region where the coordinate value in the y direction is large. Since Q1 to Q8 have lower image resolutions, the number of corresponding points calculated by the corresponding point detection unit 7 is also reduced. Therefore, for example, when the predetermined threshold is set with reference to the dry / humidity determination region Q1 having the smallest coordinate value in the y direction, the road surface portions corresponding to the dry / humidity determination regions Q2 to S8 excluding the dry / humidity determination region Q1 used as the reference are actually In spite of being in a dry state, there is a high possibility that the road surface wet and dry state determination unit 9 will erroneously determine that the vehicle is wet. However, the predetermined threshold value is set to a small value to compensate for a decrease in the image resolution in the dry / wet determination regions Q1 to Q8 having a large coordinate value in the y direction. For this reason, the road surface wet / dry state determination unit 9 can prevent the erroneous determination and improve the wet / dry determination accuracy.

(Other embodiments)
The configuration of the present invention is not limited to the above embodiment, but includes various other configurations. That is, in each of the above-described embodiments, the predetermined threshold value used when performing the wet / dry determination in the road surface wet / dry state determination unit 9 is set regardless of the speed of the vehicle A, but is not limited thereto. For example, it may be changed according to the vehicle speed. Specifically, a vehicle speed sensor (not shown) as a vehicle speed detecting means for detecting the vehicle speed is connected to the road surface wet / dry condition determining unit 9 so that a signal can be transmitted and received. The vehicle speed may be calculated based on a signal from the vehicle speed sensor, and the predetermined threshold value may be set lower as the calculated vehicle speed is higher. In this way, even if the number of corresponding points detected by the corresponding point detection unit 7 decreases due to an increase in vehicle vibration accompanying an increase in the speed of the vehicle A, the dry / wet determination by the road surface wet / dry state determination unit 9 is accurate. It becomes possible to carry out well and reliably.

  In addition, when the dry / wet determination is performed in the road surface wet / dry state determination unit 9, the predetermined threshold may be changed based on, for example, the luminance distribution calculated by the luminance distribution calculation unit 5. Specifically, as the luminance distribution calculated by the luminance distribution calculation unit 5 becomes lower in luminance state (as the distribution widths B1 and B2 at a predetermined ratio of the peak values W1 and W2 of the luminance distribution become narrower), the wet and dry state on the road surface It is preferable to lower the predetermined threshold value used for the dry / wet determination in the determination unit 9. By doing so, it is possible to accurately and reliably perform the dry / wet determination of the traveling road surface 20 by the road surface wet / dry state determination unit 9 even in a relatively dark situation such as dusk.

  Moreover, in each said embodiment, although the said corresponding point detection part 7 performs a corresponding point search (detection) in the whole area | region of the left camera image GL, it is not restricted to this, For example, The corresponding point search may be performed only in the dry / wet determination region Q of the left camera image GL. By doing so, it is possible to limit the corresponding point search area by the corresponding point detection unit 7 and to shorten the corresponding point detection time (matching processing time). As a result, the traveling road surface 20 of both the cameras 2R and 2L can be reduced. It is possible to further reduce the dry / wet determination processing time of the dry / wet determination road surface portion 20a.

  In each of the above embodiments, the cameras 2R and 2L are arranged so that their imaging areas completely match (overlap). However, the present invention is not limited to this. You may arrange | position so that a part may overlap.

  In each embodiment described above, the luminance determination region setting unit 4 sets the luminance determination region R in the left camera image GL. However, the present invention is not limited to this. For example, the right camera image The luminance determination area R may be set in the GR.

  Further, in each of the above embodiments, the road surface determination unit 8 determines whether or not the object to be imaged in the dry / wet determination region Q of the left camera image GL is the traveling road surface 20, but this road surface determination is not necessarily performed. There is no need to provide the section 8 (to make this determination).

  Moreover, in each said embodiment, although the road surface wet / dry state determination part 9 transmits the dry / humidity information of the determined wet / dry determination road surface part 20a of the traveling road surface 20 to the DSC control apparatus 11, it is not necessarily restricted to this. For example, when information indicating that the road surface portion 20a is in a wet state is received, the wet / dry information may be transmitted to an alarm device or the like that issues an alarm to an occupant of the vehicle A.

  In each of the above embodiments, the wet / dry determination region Q is set for the left camera image GL. However, the present invention is not limited to this, and may be set for the right camera image GR, for example. Good.

  In each of the above embodiments, the luminance determination region R is set for the right camera image GR. However, the present invention is not limited to this. For example, the luminance determination region R may be set for the left camera image GL. Good.

  INDUSTRIAL APPLICABILITY The present invention is useful for a vehicular road surface state estimation device that includes an imaging unit that captures an image of a traveling road surface of a vehicle and performs dry / wet determination on the traveling road surface based on an image captured by the imaging unit.

It is a block diagram which shows schematic structure of the road surface state estimation apparatus for vehicles which concerns on embodiment of this invention. It is the schematic diagram seen from the front diagonal upper direction which shows the vehicle by which the road surface state estimation apparatus for vehicles is mounted. It is a graph which shows the luminance distribution in the luminance determination area | region of the left camera image calculated by the luminance distribution calculation part of ECU. It is a figure which shows the dryness / humidity determination area | region set by the brightness | luminance determination area | region set by the luminance determination area | region setting part of ECU, and the dry / wet determination area | region setting part with respect to a left camera image. It is explanatory drawing of the Area-based matching method used for the corresponding point search by the corresponding point detection part of ECU. It is the distance image which displayed and detected the pixel detected as a corresponding point by the corresponding point detection part of ECU when the driving | running | working road surface is in a dry state with the density | concentration according to the front distance information of this corresponding point. FIG. 5 is a view corresponding to FIG. 4 when the traveling road surface is in a wet state. The corresponding point detected by the corresponding point detection unit of the ECU is the y coordinate on the image surface of each corresponding point on the vertical axis, and the vehicle forward distance corresponding to the forward distance information of each corresponding point on the horizontal axis. It is the distribution map plotted on the coordinate system. FIG. 9 is a distribution diagram showing the distribution of corresponding points obtained by the road surface determination unit of the ECU, and the density of corresponding points located in a plane perpendicular to the paper surface including the PL line separated from the lower limit line of FIG. 8 by a predetermined distance. Is a distribution map in which the vehicle is calculated in each position range in the vehicle width direction for each preset vehicle front distance range and displayed at a density according to the size. It is a flowchart which shows the dry / humidity determination control process performed by the main control part of ECU. It is a schematic diagram which shows a mode that the light reflected on the running road surface in a dry state injects into the left and right cameras. It is a schematic diagram which shows a mode that the light reflected on the driving | running | working road surface in a wet state injects into the camera on either side. FIG. 5 is a diagram corresponding to FIG. 4 of the second embodiment. The number of corresponding points included in each of the plurality of dry / wet determination regions having different y-direction coordinate values on the image plane, and a predetermined threshold set in accordance with the y-direction coordinate values of the respective dry / wet determination regions It is an example of the graph which shows a relationship.

A Vehicle S Dry / wet determination area (predetermined area)
R Luminance determination area 1 Vehicle road surface state estimation device 2L Left camera (first imaging means)
2R right camera (second imaging means)
3 Camera image acquisition unit (image information storage means)
3L left camera image acquisition unit (image information storage means)
3R right camera image acquisition unit (image information storage means)
4. Luminance determination area setting unit (luminance determination area setting means)
5. Luminance distribution calculation unit (luminance distribution calculation means)
6 Dry / wet determination area setting unit (predetermined area setting means)
7 Corresponding point detector (corresponding point detector)
8 Road surface determination unit (road surface determination means, corresponding point distribution calculation means)
9 Road surface wet and dry state determination unit (wet and dry determination means)
20 Traveling road surface 20a Dry / wet determination road surface part (road surface part corresponding to a predetermined area on the traveling road surface)

Claims (5)

A vehicle road surface state estimating device for estimating a wet and dry state of a traveling road surface of a vehicle,
A first imaging means and a second imaging means for imaging the traveling road surface of the vehicle so that at least a part of each captured image overlaps;
Image information storage means for storing a first image and a second image made up of a plurality of pixels having luminance information, respectively imaged by the first and second imaging means;
Predetermined area setting means for setting a predetermined area in an overlapping portion of the first image stored in the image information storage means with the second image;
By comparing the first image and the second image stored by the image information storage means based on the luminance information of the pixels of each image, the second image is at least within the predetermined region of the first image. And corresponding point detecting means for calculating the number of corresponding points in the detected predetermined area,
Based on the number of corresponding points in the predetermined area calculated by the corresponding point detection means, whether the road surface portion corresponding to the predetermined area on the traveling road surface of the vehicle is in a wet state or a dry state. A wet and dry determination means for performing the determination ,
When the number of corresponding points calculated by the corresponding point detection unit is equal to or less than a predetermined threshold value set in advance, the dry / wet determination means has a wet road surface portion corresponding to the predetermined area on the traveling road surface of the vehicle. On the other hand, when the number of corresponding points is greater than the predetermined threshold, it is configured to perform dry / wet determination to determine that the road surface portion is in a dry state,
The predetermined area setting means sets a plurality of predetermined areas having different vertical coordinate values, which are directions corresponding to the traveling direction of the vehicle in the first image, for overlapping portions of the first image. Configured as
The corresponding point detection means is configured to detect a corresponding point with the second image in at least each predetermined region of the first image, and to calculate the number of corresponding points in the detected predetermined region,
The wet and dry determination means is configured to perform the dry and wet determination for each of the road surface portions corresponding to the predetermined areas on the road surface of the vehicle,
The predetermined threshold used at the time of the wet / dry determination by the dry / wet determination means is set in advance for each of the predetermined areas, and is set to a smaller value as the vertical coordinate value of each of the predetermined areas is larger . A vehicle road surface state estimation device characterized by the above. In the vehicle road surface state estimation device according to claim 1 ,
Vehicle speed detecting means for detecting the speed of the vehicle,
The road condition estimation apparatus for a vehicle according to claim 1, wherein the predetermined threshold value used at the time of the dry / wet determination by the dry / humidity determination unit is set to a smaller value as the vehicle speed detected by the vehicle speed detection unit is higher. In the vehicle road surface state estimation device according to claim 1 ,
The predetermined area setting means is configured to set a part of an image area corresponding to the traveling road surface of the vehicle in the overlapping portion of the first image as the predetermined area,
The vehicular road surface state estimating device, wherein the corresponding point detecting means is configured to detect a corresponding point with the second image only in the predetermined region of the first image. In the vehicular road surface state estimating device according to any one of claims 1 to 3 ,
A luminance determination area for setting an image area corresponding to the traveling road surface of the vehicle as a luminance determination area with respect to an overlapping portion of one of the first image and the second image stored in the image information storage means with the other. Setting means;
Based on the luminance information of each pixel of the first or second image in which the luminance determination region is set by the luminance determination region setting means, the luminance in the luminance determination region of the set first or second image A luminance distribution calculating means for obtaining a luminance distribution curve by drawing a relationship between a level and the number of pixels corresponding to the luminance level in a biaxial graph;
When the luminance distribution width at a predetermined ratio of the peak value of the number of pixels in the luminance distribution curve obtained by the luminance distribution calculating unit is smaller than the predetermined width, the dry / wet determination unit does not execute the dry / humid determination, A vehicular road surface state estimating device characterized in that the dry / wet determination is performed when the luminance distribution width is equal to or greater than the predetermined width. The road surface state estimating device for a vehicle according to claim 1 Symbol placement,
Corresponding point distribution calculating means for obtaining distance image data of each corresponding point in the predetermined area of the first image detected by the corresponding point detecting means;
Road surface determining means for determining whether or not the object to be imaged projected on the image in the predetermined area of the first image is a traveling road surface based on the distance image data obtained by the corresponding point distribution calculating means,
The dry / wet determination unit performs the dry / wet determination when the road surface determination unit determines that the imaged object is a traveling road surface, while the dry / humidity determination unit determines that the imaged object is not a traveling road surface. A vehicular road surface state estimating device, wherein the dry / wet determination is not executed.