JP2004343303A - Exposure controller of in-vehicle camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure controller of an in-vehicle camera in which the exposure of the camera is appropriately controlled even if a preceding vehicle exists. <P>SOLUTION: When the preceding vehicle 120 is detected in front of an own vehicle, photometry windows L4 to L6 and R4 to R6 are shifted in right/left directions and are set so that they are not overlapped with the preceding vehicle 120 when the photometry windows are set on an image-picked up image. A concentration value of a lane mark in the photometry window shifted by using a concentration ratio of a road surface and a lane mark in the photometry window which is not shifted and the concentration value of the road surface in the shifted photometry window is estimated. The exposure of the camera is controlled by using the estimated concentration value of the lane mark and the concentration value of the lane mark in the photometry window which is not shifted. Thus, a brake lamp or the like of the preceding vehicle is prevented from being reflected in the photometry window. Exposure can precisely be controlled and the lane mark can stably be detected. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exposure control device that controls exposure of a camera mounted on a vehicle.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there has been known an apparatus which captures a road image ahead by a camera mounted on a vehicle and detects a lane mark (a so-called lane marking such as a white line) from the captured image. In such exposure control of a camera, a density value at a position corresponding to a lane mark in a picked-up image is calculated, and the exposure for the next image pickup is controlled based on the calculated density value.
[0003]
[Problems to be solved by the invention]
In such a conventional vehicle-mounted camera exposure control device, when a preceding vehicle is present in front of the own vehicle, if the camera reflects the sunlight reflected by the body of the preceding vehicle, the next camera is used. There is a problem that exposure control is performed in accordance with sunlight when capturing an image, and there is a possibility that a lane mark cannot be detected from a captured image. Also, at night, when the preceding vehicle turns on the brake lamp, the exposure control according to the light of the brake lamp is performed in the same manner as described above.
[0004]
SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a vehicular camera exposure control device that can appropriately perform camera exposure control even when a preceding vehicle is present.
[0005]
[Means for Solving the Problems]
The present invention provides a camera for imaging a road in a traveling direction of a vehicle, a photometric window setting means for setting a photometric window at a position corresponding to a lane mark of a road in a road image captured by the camera, and a photometric window. Density value calculating means for calculating the density value of the camera, exposure control value setting means for setting the exposure control value of the camera from the calculated density value in the photometric window, and preceding vehicle detecting means for detecting the preceding vehicle The photometric window setting means shifts the photometric window overlapping the preceding vehicle from a position corresponding to the lane mark of the road to a position not overlapping the preceding vehicle when the preceding vehicle is detected by the preceding vehicle detecting means. And set it.
[0006]
【The invention's effect】
According to the present invention, when a preceding vehicle is present, a photometric window is set at a position that does not overlap with the preceding vehicle on a road image captured by a camera, so when calculating a density value in the photometric window, For example, when sunlight is reflected from the body of the preceding vehicle and the reflected light is imaged by a camera, or when the preceding vehicle turns on the brake lamp at night, the reflected light of sunlight and the density value of the brake lamp are also used. Is prevented from being calculated, and the exposure control value of the camera can be set correctly.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to examples.
FIG. 1 shows a block diagram in this embodiment.
A camera 100 that captures a road ahead of the host vehicle is connected to the edge image extraction unit 101, and a road image captured by the camera 100 is output to the edge image extraction unit 101. The camera 100 captures an image every 50 msec, for example.
The edge image extraction unit 101 performs an edge extraction processing operation from the road image to obtain vertical and horizontal edge images. The edge image obtained by the edge image extraction unit 101 is output to the lane mark detection window setting unit 102.
The lane mark detection window setting unit 102 sets a lane mark detection window for detecting a lane mark (white line) position with respect to the input edge image.
[0008]
The edge image in which the lane mark detection window is set is output to the lane mark position detection unit 103, and the lane mark position detection unit 103 detects the position of the lane mark by straight line estimation or the like from the edge image in each lane mark detection window. .
The lane detecting unit 104 estimates the traveling lane from the position of the lane mark detected by the lane mark position detecting unit 103. By performing curve estimation from the lane mark position in each lane mark detection window, it is possible to estimate the overall shape of the traveling lane.
[0009]
The rotation angle of the steering wheel is detected by a steering angle detection unit 105 attached to a steering wheel (not shown) of the vehicle, and the detection result is output to a steering control unit 106.
The rotation angle of the steering wheel detected by the steering angle detection unit 105 is used to determine whether or not the own vehicle may deviate from the traveling lane or to determine whether or not there is steering intervention by the driver. Used.
That is, the steering control unit 106 uses the traveling lane estimated by the lane detecting unit 104 and the steering wheel rotation angle detected by the steering angle detecting unit 105 to move along the lane mark position obtained from the estimated traveling lane. The vehicle is automatically steered so that the host vehicle runs, and when the vehicle is about to deviate from the traveling lane, the vehicle is automatically steered to prevent the departure.
[0010]
The preceding vehicle detection unit 107 is connected to the photometry window setting unit 108. The preceding vehicle detection unit 107 irradiates a radar or the like toward the front of the own vehicle, detects the presence or absence of the preceding vehicle from the reflected wave reflected by the preceding vehicle, and further measures the distance to the preceding vehicle.
The photometric window setting unit 108 sets a photometric window on the road image captured by the camera 100 in order to calculate a lane mark and a density value of a road surface. When the preceding vehicle is detected by the preceding vehicle detection unit 107 when the photometric window is set, the preceding vehicle is set at a position to avoid the preceding vehicle so that the photometric window does not overlap the preceding vehicle according to the detection position of the preceding vehicle. Set by shifting.
[0011]
The density value calculating unit 109 calculates the density value between the lane mark and the road surface in the photometric window set by the photometric window setting unit 108. The exposure control unit 110 sets an exposure control value of a road image to be captured next time by the camera 100 based on the density value calculated by the density value calculation unit 109.
[0012]
Next, the flow of processing from setting of a photometric window to setting of an exposure control value will be described with reference to the flowchart of FIG.
In step 200, the photometric window setting unit 108 determines whether or not the preceding vehicle has been detected by the preceding vehicle detecting unit 107. If the preceding vehicle has not been detected, the process proceeds to step 207.
[0013]
On the other hand, if the preceding vehicle is detected, the photometric window setting unit 108 sets the photometric windows L1 to L6 and R1 to R6 on the road image captured by the camera 100 as shown in FIG. I do.
The photometric window is set at a position corresponding to the lane mark shape in the order of L1 to L6 from the lower left on the road image toward the center upward, and R1 to R6 from the lower right to the center upward on the road image. Further, the photometric windows L4 to L6 and R4 to R6 which may overlap with the preceding vehicle 120 detected by the preceding vehicle detection unit 107 are set so as to be shifted in the left-right direction so as not to overlap with the preceding vehicle 120.
The photometric window is set to be smaller as going upward from below on the road image.
[0014]
In step 202, the density value calculation unit 109 calculates the density values a and b of the lane marks of the photometric windows L1 to L3 and R1 to R3 that are not shifted.
An example of calculating the respective density values a and b will be described with reference to FIGS.
When the density value is calculated in the horizontal direction from the density calculation position K of the photometric window L2 shown in FIG. 4A, the density value at the horizontal position corresponding to the lane mark portion is obtained as shown in FIG. Can obtain a high graph. The high density value a can be obtained as the density value of the lane mark, and the low density value b can be obtained as the density value of the road surface. The calculation of the density values a and b is performed for all the photometric windows that are not shifted.
[0015]
Also, a lane mark density value a (n) and a road surface density value b (n) are calculated for each of the set n photometric windows, and a statistical process such as an average value, a median value, and a 3σ value is performed from the density value group. By calculating the lane mark density value a and the road surface density value b for the photometric window, it is possible to suppress density errors due to the effects of lane mark breaks, dirt, road surface repair patterns, and the like.
[0016]
In step 203, the density value ratio N between the density value a of the lane mark and the density value b of the road surface is determined for each of the photometric windows L1 to L3 and R1 to R3 that have not been shifted.
N = a / b (1)
Further, an average density value N ′ is obtained by averaging the density value ratios N calculated for each photometry window.
[0017]
In step 204, the density value b of the road surface in the shifted photometric windows L4 to L6 and R4 to R6 is calculated. Here, assuming that there is no lane mark in the shifted photometry window, a low density value is calculated as a road surface density value b.
In step 205, the density values A of the lane marks in the shifted photometric windows L4 to L6 and R4 to R6 are estimated and calculated.
[0018]
Here, the density value ratio N between the lane mark density value and the road surface density value is substantially the same in the captured road image. Therefore, using the average density value ratio N ′ calculated in step 203 and the road surface density value b of the shifted photometric window, the density value A of the lane mark can be estimated by the following equation.
A = b × N ′ (2)
By using the equation (2) in this way, the lane mark density value A in the shifted photometry window can be estimated.
[0019]
In step 206, the exposure control value of the road image to be captured next time is set from the lane mark or the density distribution state of the road surface calculated or estimated for each photometric window.
In the present embodiment, when the distribution range of the density value of the road image is a range that can be covered when one exposure control value is picked up, one exposure control value is set, and one exposure control value is used. Perform imaging twice.
Also, when the distribution of density values cannot be covered when the image is captured using one exposure control value, for example, when the brightness is significantly different from the image captured by the camera when entering a tunnel, An exposure control value for capturing an image on the bright side and an exposure control value for capturing an image on the dark side are set, two images are captured using the respective exposure control values, and the two captured images are used in a superimposed manner.
[0020]
On the other hand, in step 207, as shown in FIG. 5, the photometric windows L1 'to L6' and R1 'to R6' are set at positions corresponding to the lane marks on the road image.
In step 208, the lane mark density value a and the road surface density value b of each of the photometric windows L1 'to L6' and R1 'to R6' are calculated. Thereafter, the process proceeds to step 206.
[0021]
In this embodiment, steps 201 and 207 constitute a photometric window setting unit in the present invention, and steps 202 and 208 constitute a density value calculating unit in the present invention. Step 206 constitutes the exposure control value setting means of the present invention, and the preceding vehicle detecting section 107 constitutes the preceding vehicle detecting means of the present invention. Further, Steps 204 and 205 constitute the density value estimating means in the present invention.
[0022]
The present embodiment is configured as described above. If a preceding vehicle is present, a photometric window is set at a position not overlapping with the preceding vehicle on the road image in step 201, so that the density value in the photometric window is calculated. In this case, for example, when sunlight is reflected by the body of the preceding vehicle and the reflected light is imaged by a camera, or when the preceding vehicle turns on the brake lamp at night, the reflected light of the sunlight or the brake lamp is also used. Is prevented from being calculated.
[0023]
Also, the density value A of the lane mark in the shifted photometry window is set to the density value of the road surface density value b in the shifted photometry window and the density value of the lane mark density value a and the road surface density value b in the non-shifted photometry window. The estimation is performed using the average density value ratio N ′ of the ratio N.
As a result, even if the distant lane mark is hidden by the preceding vehicle, the density value of the lane mark can be estimated, so that the location where the preceding vehicle exists and where the brightness changes greatly near the entrance and exit of the tunnel Also, the density value of the lane mark and the road surface can be calculated and estimated, and the lane mark can be detected stably by controlling the exposure of the camera using the density value.
[0024]
In the present embodiment, as shown in FIGS. 3 and 5, the photometry windows are set at six locations on the left and right, but the invention is not limited to this, and at least two locations may be set. Although the size of the photometric window decreases from the bottom to the top of the image, the same size may be set.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of the present invention.
FIG. 2 is a flowchart showing a flow of exposure control value calculation.
FIG. 3 is a diagram showing a setting position of a photometric window when a preceding vehicle is present.
FIG. 4 is a diagram showing calculation of a density value in a photometry window.
FIG. 5 is a diagram showing a setting position of a photometric window when there is no preceding vehicle.
[Explanation of symbols]
REFERENCE SIGNS LIST 100 camera 101 edge extraction unit 102 lane mark detection window 103 lane mark position detection unit 104 lane detection unit 105 steering angle detection unit 106 steering control unit 107 preceding vehicle detection unit 108 photometric window setting unit 109 density value calculation unit 110 exposure control unit

Claims (3)

A camera for imaging the road in the traveling direction of the vehicle,
A photometric window setting means for setting a photometric window at a position corresponding to a lane mark of a road in a road image captured by the camera;
Density value calculation means for calculating a density value in the photometric window,
Exposure control value setting means for setting an exposure control value of the camera from the calculated density value in the photometric window,
Preceding vehicle detection means for detecting a preceding vehicle,
The photometric window setting means, when the preceding vehicle is detected by the preceding vehicle detecting means, does not overlap the photometric window overlapping the preceding vehicle from the position corresponding to the lane mark of the road with the preceding vehicle. An exposure control device for a vehicle-mounted camera, wherein the exposure control device is set to be shifted to a position. Having a density value estimating means for estimating the density value in the photometric window set shifted by the photometric window setting means,
The density value estimating means estimates the density value of the lane mark of the road from the shifted photometry window,
The exposure control value setting unit sets an exposure control value of the camera based on a density value calculated by the density value calculation unit and a density value estimated by the density value estimation unit. Item 2. An exposure control device for a vehicle-mounted camera according to Item 1. The density value calculation means calculates the density value of the lane mark portion and the road surface portion in the photometry window that has not been shifted,
The density value estimating means calculates a density value of the road surface portion in the shifted photometric window, and calculates the density value of the calculated road surface portion and a lane in the non-shifted photometric window calculated by the density value calculating device. 3. The exposure control device for a vehicle-mounted camera according to claim 2, wherein a density value of a lane mark portion in the shifted photometric window is estimated using a ratio of a density value of a mark portion and a density value of a road surface portion.

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