JP2009014645A - Vehicle distance measuring device - Google Patents

Abstract

An object of the present invention is to accurately measure the distance from a host vehicle to a road sign.
An outside camera that captures a road sign ahead of the vehicle, a travel distance measurement unit that measures a travel distance of the vehicle, and a sign image size calculation unit that calculates a detection amount corresponding to the size of the road sign image. 11, a parallax detection unit 13 that calculates a change amount of the detected amount with respect to the travel distance, and a relationship between the amount corresponding to the size of the road sign image and the change amount with respect to the travel distance for each size of the road sign. A data storage unit 4 stored in advance, a sign size determination unit 14 that compares the detected amount, the change amount, and the relationship stored in the data storage unit 4 to determine the size of the road sign, and the viewing angle with respect to the road sign A visual angle detection unit 15 for detecting the road sign, and a distance calculation unit 16 for calculating a distance to the road sign based on the size of the road sign determined by the sign size determination unit 14 and the visual angle detected by the visual angle detection unit 15. Obtain.
[Selection] Figure 1

Description

  The present invention relates to a vehicle distance measuring device that measures a distance to a road sign ahead of a vehicle.

Take a road sign in front of the vehicle, classify the type of the object by image processing, and the distance to the object based on the size data stored in the knowledge base and the viewing angle for the object There is known a distance measuring device that calculates the value (for example, see Patent Document 1).
JP-A-8-219775

  By the way, there are road signs of different sizes even if they are the same type (for example, a stop sign). For example, as shown in FIG. 6, the stop sign has an inverted triangle, and the characters, colors, and the like have the same form, but the maximum width dimension X has four sizes of 533 mm, 800 mm, 1200 mm, and 1600 mm. The dimension X is standardized and is not an arbitrary dimension.

  Therefore, in the conventional distance measuring device, even if it is classified as the same type of road sign, if the size of the road sign is different from the size of the road sign stored in the knowledge base, the distance measurement has an error. There is a problem that it may occur.

  Therefore, the present invention provides a vehicular distance measuring apparatus that can accurately measure a distance even when road signs have different sizes.

The vehicle distance measuring device according to the present invention employs the following means in order to solve the above problems.
The invention according to claim 1 includes imaging means (for example, an external camera 2 in an embodiment described later) that is provided on the vehicle and images a road sign ahead of the vehicle (for example, a stop sign S in the embodiment described later). In a vehicle distance measuring device (for example, a vehicle distance measuring device 1 in an embodiment described later) that measures a distance to the road sign based on a road sign image picked up by the image pickup means, the travel distance of the vehicle is measured. Travel distance measuring means (for example, a travel distance measuring unit 12 in the embodiment described later) and first calculation means (for example, a sign in the embodiment described later) for calculating a detection amount corresponding to the size of the road sign image. An image size calculation unit 11) and second calculation means for calculating a change amount of the detection amount with respect to the travel distance (for example, the parallax detection unit 1 in an embodiment described later) ) And an amount corresponding to the size of the road sign image and the amount of change with respect to the travel distance for each size of the road sign (for example, the data storage unit 4 in the embodiment described later) ) And the detected amount calculated by the first calculating unit, the change amount calculated by the second calculating unit, and the relationship stored in the storage unit are compared to determine the size of the road sign Road sign size judging means (for example, a sign size judging unit 14 in the embodiment described later), a viewing angle detecting means for detecting a viewing angle with respect to the road sign (for example, a viewing angle detecting unit 15 in the embodiment described later), and the road Distance calculating means for calculating the distance to the road sign based on the size of the road sign determined by the sign size determining means and the visual angle detected by the visual angle detecting means (for example, rear A distance calculation unit 16) in the embodiment is characterized in that it comprises a.

  With this configuration, when there are a plurality of road signs of the same type and different sizes, the detection amount calculated by the first calculation means and the second calculation means are calculated. The size of the road sign can be determined based on the amount of change, and the distance from the host vehicle to the road sign is measured based on the determined size of the road sign and the visual angle detected by the visual angle detection means. Can do.

  According to the first aspect of the present invention, when there are a plurality of road signs of the same type and different in size, the accuracy of recognition of the size of the road sign is improved, and from the own vehicle to the road sign Can be measured with high accuracy.

Embodiments of a vehicle distance measuring apparatus according to the present invention will be described below with reference to the drawings of FIGS.
As shown in FIG. 1, the vehicle distance measuring device 1 in this embodiment includes an external camera (imaging unit) 2, a vehicle speed sensor 3, a data storage unit (storage unit) 4, and a processing device 10. The output signal of the processing device 10 is output to a control device 20 such as a driving support control device.

  The external camera 2 includes, for example, a camera such as a CCD camera or a CMOS camera that can be imaged in the visible light region and an image processing unit. For example, the camera disposed in the passenger compartment moves in the traveling direction of the host vehicle through the front window. The outside world of the predetermined detection range ahead is imaged at predetermined time intervals. Then, the image processing unit performs predetermined image processing such as filtering on the image obtained by photographing with the camera, generates image data including pixels of a two-dimensional array, and outputs the image data to the processing device 10.

The vehicle speed sensor 3 detects the speed of the host vehicle (vehicle speed) and outputs an output signal corresponding to the vehicle speed to the processing device 10.
The data storage unit 4 stores a model image corresponding to the type of road sign (for example, a triangular shape that is the outer shape of the stop sign S shown in FIG. 6) and a size of the road sign described later. A road sign dimension determination map and the like are stored in advance.

The processing device 10 includes a sign image size calculation unit (first calculation unit) 11, a travel distance measurement unit (travel distance measurement unit) 12, a parallax detection unit (second calculation unit) 13, and a sign size determination unit. (Road sign size determination means) 14, a viewing angle detection unit (viewing angle detection unit) 15, and a distance calculation unit (distance calculation unit) 16.
The sign image size calculation unit 11 calculates the number of pixels of the representative dimension part of the road sign in the road sign image (hereinafter abbreviated as the number of pixels of the road sign image) θ based on the image data input from the external camera 2. In this embodiment, when the road sign is a temporary stop sign, the representative dimension part of the road sign is the maximum width dimension part corresponding to the dimension X in FIG. However, the representative dimension portion of the road sign is not limited to this, and may be the maximum dimension portion in the height direction.

The travel distance measuring unit 12 calculates a travel distance (that is, travel distance) L of the host vehicle for a predetermined time based on the output signal of the vehicle speed sensor 3.
The parallax detection unit 13 determines the number of pixels θ of the road sign image with respect to the travel distance L based on the number of pixels θ of the road sign image calculated by the sign image size calculation unit 11 and the travel distance L calculated by the travel distance measurement unit 12. Is calculated, that is, the parallax θa is calculated.

For example, as shown in FIG. 2, when there is a T-shaped intersection in front of the host vehicle V and there is a stop sign S in front of the intersection, the number of pixels of the road sign image captured by the external camera 2 at time t1 Is θ1 (pixel), the number of pixels of the road sign image captured by the external camera 2 at time t2 after a predetermined time is θ2 (pixel), and the travel distance of the host vehicle between time t1 and t2 is L In the case of (m), the parallax θa is calculated from the equation (1).
θa = (θ2−θ1) / L (1)

  The sign size determination unit 14 includes the number of pixels θ of the road sign image calculated by the sign image size calculation unit 11, the parallax θa detected by the parallax detection unit 13, and the road sign size determination map stored in the data storage unit 4. Based on the above, the size of the road sign (dimension X of the representative dimension portion) that is the subject of the external camera 2 is determined.

  Here, the road sign dimension determination data stored in the data storage unit 4 will be described. In general, when the same subject is photographed by the external camera 2, the parallax (the amount of change in the number of pixels with respect to the travel distance) of the subject image is constant according to the size (number of pixels) of the photographed subject image. Therefore, when there are a plurality of signs of the same type having the same shape but different dimensions as in a road sign, if the relationship between the number of pixels θ of the road sign image and the parallax θa is known in advance for each dimension, It is possible to know the size of the road sign based on the number of pixels and the parallax of the road sign image taken by the external camera 2 of the traveling vehicle.

  Therefore, in this embodiment, for example, for a stop sign, a relationship between the number of pixels θ of the road sign image and the parallax θa is experimentally obtained in advance for each sign size (representative dimension X). The data is stored in the data storage unit 4 as a road sign dimension determination map shown in FIG. In the map shown in FIG. 3, three sizes of the representative dimension portion of the stop sign X = 533 mm, 800 mm, and 1200 mm are shown, and X = 1600 mm is omitted.

The viewing angle detection unit 15 detects the viewing angle α with respect to the road sign that is the subject based on the number of pixels θ of the road sign image calculated by the sign image size calculation unit 11. For example, in the case of 0.0252 deg / pixel, the viewing angle α is calculated from Equation (2).
α = 0.0252θ Equation (2)

The distance calculation unit 16 determines the road sign S from the host vehicle V based on the size of the road sign determined by the sign size determination unit 14 (the dimension X of the representative dimension part) and the viewing angle α detected by the viewing angle detection unit 15. The distance D is calculated by the equation (3) (see FIG. 4).
D = X / tan α (3)
Then, the distance calculation unit 16 outputs an output signal corresponding to the calculated distance D to the control device 20.

  For example, the control device 20 sets a travel support level according to the distance data obtained from the distance calculation unit 16 and the vehicle state (vehicle speed, etc.) of the host vehicle, and information that prompts execution of a pause according to the travel support level. And control such as executing deceleration support for the host vehicle.

  Next, distance calculation processing by the processing apparatus 10 in this embodiment will be described with reference to the flowchart of FIG. In this distance calculation process, edge extraction is performed on the image data output from the external camera 2 to generate an edge image, and a road sign model stored in the data storage unit 4 is generated for the edge image. It is assumed that a pattern matching process using an image is performed, and the road sign in front of the photographed vehicle is determined to be a stop sign and is executed at the same time.

First, in step S101, image data output from the external camera 2 is acquired.
In step S102, the number of pixels θ of the road sign image is calculated based on the acquired image data.
Next, proceeding to step S103, the amount of change in the number of pixels θ of the road sign image with respect to the travel distance L, that is, the actual parallax θa is calculated. For example, the number of pixels θ2 of the road sign image calculated in step S102 when this distance calculation processing routine is executed this time, and the number of pixels θ1 of the road sign image calculated in step S102 when this distance calculation processing routine is executed last time. The actual parallax θa is calculated (θa = (θ2−θ1) / L) based on the difference (θ2−θ1) between the two and the travel distance L of the host vehicle during the period of the distance calculation processing routine.

Next, proceeding to step S104, the parallax θn corresponding to the number of pixels θ of the road sign image calculated in step S102 is calculated for each road sign size with reference to the road sign size determination map shown in FIG.
Next, proceeding to step S105, an absolute value Δθn of a difference between the actual parallax θa calculated at step S103 and the parallax θn for each road sign size calculated at step S104 is calculated (Δθn = | θn−θa |). .
Next, the process proceeds to step S106, and the road sign size that is the smallest among the absolute values Δθn of the parallax differences calculated for each road sign size is selected as the size of the road sign ahead of the host vehicle.

  For example, when the distance calculation processing routine is executed this time, the number of pixels of the road sign image θ2 = 40 pixels, when the distance calculation processing routine is executed last time, the number of pixels of the road sign image θ1 = 39 pixels, the cycle of the distance calculation processing routine The actual parallax θa is 1 pixel / m when the travel distance L of the host vehicle is 1 m. In this case, the difference in parallax is minimized for the road sign size with the dimension X = 800 mm in the representative dimension portion. Then, a road sign size with a dimension X = 800 mm of the representative dimension portion is selected.

  Next, the process proceeds to step S107, where the viewing angle α for the road sign is calculated based on the pixel number θ of the road sign image calculated in step S102, and the representative dimension in the road sign of the road sign size selected in step S106. The distance D from the host vehicle V to the road sign S is calculated based on the dimension X of the part (D = X / tan α), and the execution of this routine is temporarily terminated.

  According to the vehicle distance measuring device 1 of this embodiment, the size of the stop sign can be determined based on the number of pixels of the road sign image and the parallax, and based on the determined size and viewing angle of the stop sign. Since the distance from the host vehicle to the stop sign can be measured, the accuracy of the distance measurement to the stop sign is improved. As a result, reliability such as driving support control by the control device 20 is improved.

[Other Examples]
The present invention is not limited to the embodiment described above.
For example, in the above-described embodiment, the description has been given by taking the stop sign as an example of the road sign. However, the present invention can be applied to other kinds of road signs as long as the size is standardized. Signal lights are also included in the road signs in the present invention.

It is a block diagram in the Example of the distance measuring device for vehicles which concerns on this invention. It is a figure explaining the parallax of a road sign image. It is a figure which shows an example of the road sign dimension determination map used in the vehicle distance measuring device of the said Example. It is a figure explaining the distance calculation principle from the own vehicle to a road sign. It is a flowchart which shows the distance calculation process of the vehicle distance measuring device in the said Example. It is a front view of a stop sign.

Explanation of symbols

1 vehicle distance measuring device 2 external camera (imaging means)
4 Data storage unit (storage means)
11 Sign image size calculation unit (first calculation means)
12 Travel distance measuring unit (travel distance measuring means)
13 Parallax detector (second calculation means)
14 sign size judgment part (road sign size judgment means)
15 viewing angle detection unit (viewing angle detection means)
16 Distance calculation part (distance calculation means)

Claims (1)

In a vehicle distance measuring device that includes an imaging unit that is provided in a vehicle and that images a road sign ahead of the vehicle, and that measures a distance to the road sign based on a road sign image captured by the imaging unit.
Mileage measuring means for measuring the mileage of the vehicle;
First calculating means for calculating a detection amount corresponding to the size of the road sign image;
Second calculating means for calculating a change amount of the detected amount with respect to the travel distance;
Storage means for storing in advance a relationship between the amount corresponding to the size of the road sign image and the amount of change with respect to the travel distance for each size of the road sign;
A road sign that compares the detected amount calculated by the first calculating means, the change amount calculated by the second calculating means, and the relationship stored in the storage means to determine the size of the road sign Dimension determination means;
Viewing angle detecting means for detecting a viewing angle with respect to the road sign;
Distance calculating means for calculating the distance to the road sign based on the size of the road sign determined by the road sign size determining means and the visual angle detected by the visual angle detecting means;
A vehicle distance measuring device comprising:

Images