JPH06282793A - Lane deviation alarm device - Google Patents

Abstract

PURPOSE:To obtain a lane deviation alarm device which correct the end part deterioration characteristic of a wide-angle lens and accurately warns the deviation of a car from a vehicle lane by applying the specific correction to the output signal of an optical sensor that is distorted by the wide-angle lens of a vehicle lane detector means. CONSTITUTION:The road surface information including the vehicle lanes forms an image on a photoelectric element of a one-dimensional linear image optical sensor 6 through a wide-angle lens. Then the electric signals are transmitted from the sensor 6 in response to the image and then converted into the digital value through the A/D conversion. The digital value is read in a CPU 5. The signals read out of the sensor 6 are serial signals, and the initial coordinate of picture element coordinates of the sensor 6 are previously decided. Then the output image data on the sensor 6 are successively stored in a memory from the initial picture element coordinates. Then a characteristic function reverse to that of a cosine quadri-power rule as well as the numerical aperture dependent on the vignetting of the wide-angle lens as shown in a figure are prepared in a ROM table in the CPU 5. Then the correction value is retrieved for the sensor signals corresponding to the picture element coordinates of each sensor 6. Then this correction value is multiplied by the sensor output picture element data for correction of deterioration of the lens.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lane departure warning system, and more particularly to a system for warning the departure of a vehicle from the lane (white line) by monitoring the road condition in front of the vehicle with a line camera or the like.

[0002]

2. Description of the Related Art FIG. 4 schematically shows the structure of a lane departure warning device which has been conventionally known from JP-A-59-128693 or JP-A-3-273498. Then, outputs from the lane detecting means 1 such as a line camera, the vehicle speed sensor 2, the turn signal (winker) 3, the alarm device 4 such as a buzzer, the lane detecting means 1, the vehicle speed sensor 2 and the turn indicator 3. It is composed of a CPU 5 as a signal processing means for receiving a signal and operating the alarm device 4.

The lane detecting means 1 is a lens (not shown).
A one-dimensional linear image optical sensor 6 such as a CCD (charge-coupled device) which converts an optical signal output from the device into an electric signal and gives it to the CPU 5 is incorporated.

FIG. 5 shows the arrangement of the lane departure warning device shown in FIG. 4 when the components are actually attached to the vehicle 10. The line camera 1 as the lane detecting means.
(And the sensor 6) are installed on the front roof of the vehicle 10, the CPU (controller) 5 as a signal processing means is provided under the seat of the driver's seat, and the output signals from the vehicle speed sensor 2 and the direction indicator 3 are also provided. It is designed to be input at the same time.

The alarm device 4 includes an actuator drive circuit 41 driven by the CPU 5 and the drive circuit 4
And a steering actuator 42 driven by 1. The actuator 42 gives an alarm to the driver by vibrating the steering wheel 11 when an alarm is issued.

FIG. 6 shows a flow chart of a control program stored and executed in the CPU 5 in the embodiment shown in FIGS. 4 and 5, and the operation of the conventional example will be described below with reference to this flow chart. .

First, the CPU 5 initializes peripheral devices and the like (step S0), and reads the camera signal from the line camera 1, the vehicle speed signal from the vehicle speed sensor 2 and the winker signal from the turn indicator 3 (step S1). ).

Of the signals read as described above, the camera signal on a horizontal line CL passing through the center O, for example, as shown in FIG. 7 (this is because the line camera does not scan in the vertical direction and does not scan in the horizontal direction). This is because there is only scanning)
Is binarized by judging whether or not exceeds the threshold (S
2).

Then, the CPU 5 extracts the lane WL on the road surface (the lane width on the center line CL in this example) from the binarized camera signal as shown in FIG. 7, and calculates the coordinates thereof (at step S3). ), And further calculates the distance between the lane and the vehicle (at step S4).

In order to determine whether or not the vehicle deviates from the lane based on the positional relationship between the vehicle and the lane thus obtained, it is determined whether or not the lane-vehicle distance is less than or equal to a threshold Th. (S5) If it is equal to or more than the threshold value, the process returns to step S1, but if it is equal to or more than the threshold value Th, it is determined in the next step S8 whether or not the vehicle speed exceeds the set value.

The reason for this is that the vehicle speed signal from the vehicle speed sensor 2 distinguishes an ordinary road, which is erroneously detected or difficult to detect lanes, from an automobile exclusive road, which is easy to detect lanes, according to the traveling speed of the vehicle.

That is, on a general road, the speed limit is generally 60.
Km / h or less, 80 to 100 Km / on a motorway
By utilizing the fact that the vehicle speed is less than or equal to h, it is determined in this step S8 whether the vehicle speed is equal to or higher than the set value (approximately 60 km / h) or less. Since there is a possibility of detection, the process returns to step S1,
If the vehicle speed exceeds the set value, it is determined that the vehicle is traveling on a road exclusively for automobiles, and the ON / OFF of the turn signal from the direction indicator 3 is determined in the next step S7.

That is, even if the vehicle is approaching the lane WL, it is not necessary to issue an alarm when the lane is changed. Therefore, it is determined in step S7 whether or not the winker signal is generated. When it is given from the direction indicator 3, the process returns to step S1, but when the winker signal is not generated, the warning device 4 is driven to give the lane departure warning (at step S8).

[0014]

In the lane departure warning device as described above, in order to detect a wide range with one one-dimensional linear image optical sensor 6 incorporated in the line camera 1, the line camera 1 has a wide angle. You need to use a lens. Here, when a wide-angle lens is used, there is a phenomenon that incident light from the lens peripheral portion is reduced as described below.

Now, letting ω be the inclination angle of the incident light beam bundle from the center optical axis of the lens (the inclination angle of the principal ray), the brightness E (ω) of the incident light beam image with the inclination angle ω is the inclination angle ω = 0 (the center light When expressed using the brightness E on the (axis), E (ω) = Ecos ⁴ ω (Equation (1)) This is called the cosine fourth law.

As the tilt angle ω increases, the projected area of the lens surface also decreases, making it difficult for the light beam to enter. Therefore, the phenomenon called vignetting also reduces the aperture efficiency η.

Therefore, the image at the end of the wide-angle lens becomes darker than that when incident from the front of the lens, and finally the above-mentioned brightness E
(Ω) is expressed as the following equation. E (ω) = E η · cos ⁴ ω Equation (2)

8 (1) to 8 (3) show the above with respect to the inclination angle ω.
Aperture efficiency η and cos in equation (1) ^Fourin ω and equation (2)
Η ・ cos^FourThe outline of ω is shown.

As described above, when the wide-angle lens is used in the line camera 1 of the lane departure warning system, the sensitivity at both ends of the sensor pixel (field of view) is lowered as shown in FIG. The ability to detect lanes is reduced.
(Note that the focus of the lens is in front of the sensor 6, so the sensor field of view substantially corresponds to ω, and the sensitivity is η in the above equation (2).
・ Corresponds to cos ⁴ ω. )

For this reason, as shown in the sensor output waveform of FIG. 2 (1), the lane detection power is low in the part, the lane cannot be accurately detected, and noise is easily erroneously detected as the lane in the part. was there.

Conventionally, there is a method of mounting a gradation filter having a transmittance having a characteristic opposite to this lens characteristic, but it is not suitable as a lane detecting means because the sensitivity as a whole is lowered.

Therefore, in order to solve the above problems, the present invention realizes a device capable of accurately warning the deviation from the lane of a vehicle by correcting the end deterioration characteristic of the wide-angle lens constituting the lane detection means. With the goal.

[0023]

A lane departure warning system according to the present invention is a signal of an image signal obtained from a lane detecting means for photographing the front of a vehicle, which comprises a wide-angle lens and a one-dimensional linear image optical sensor. The lane on the road surface is extracted by binarizing the processing means, and when the vehicle-to-vehicle distance between the lane and the vehicle becomes a certain value or less When the vehicle speed is the set value or more and the direction instruction operation is not performed Assuming a lane departure warning device for energizing the warning device, the signal processing means outputs an inverse characteristic function of the aperture efficiency due to vignetting of the wide-angle lens and the lens characteristic of the cosine fourth law to the output signal of the optical sensor. It is characterized in that a value corrected by being multiplied by is used as an output image signal of the lane detecting means.

[0024]

In the present invention, the output signal of the optical sensor distorted by the wide-angle lens in the lane detecting means is, as shown in FIG. 1, the aperture efficiency due to vignetting of the wide-angle lens and the characteristic of the cosine fourth law (see FIG. 9). A characteristic function opposite to that is prepared in advance, and the inverse characteristic function is multiplied by the image signal obtained from the optical sensor to perform correction.

The image signal thus corrected is shown in FIG.
The waveform becomes as shown in (2), and the signal processing means extracts the lane on the road surface by binarizing this image signal.

When the vehicle-to-vehicle distance between the lane and the vehicle is below a certain position, and the vehicle speed is equal to or higher than the set value and the direction indicating operation is not performed, it is assumed that the alarm activation condition is satisfied, as in the conventional example. The alarm device is driven to generate an alarm.

If a value of 1 or more is set as the above correction value, it is possible to avoid lowering the overall sensitivity as compared with the correction by the gradation filter.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment of the lane departure warning system according to the present invention, the same structure as the conventional example shown in FIG. 4 can be used, and therefore its explanation is omitted here.

FIG. 3 is a flow chart showing the control algorithm of the present invention for the CPU 5 as the signal processing means shown in FIG. 4, and the operation of the embodiment of the present invention will be described below with reference to this flow chart and FIG. To do.

First, after initializing the states of the CPU 5 itself and the respective sensors / switches (step S0), the road surface information including the lanes is read by a photoelectric sensor in the one-dimensional linear image optical sensor 6 through a wide-angle lens (not shown). Form an image on the element,
An electric signal corresponding to the image is output from the sensor and is first A / D-converted in the CPU 5 to be converted into a digital value and read (step S1).

The signal read from the sensor 6 is a serial signal, and the sensor output image data is stored in a memory (not shown) in order from the initial coordinates by predetermining the initial coordinates of the one-dimensional sensor pixel coordinates. (Step S10).

Next, a characteristic function opposite to the characteristic of the aperture efficiency due to vignetting of the wide-angle lens as shown in FIG. 1 and the characteristic of the fourth power law of cosine (see FIG. 9) is also prepared in the CPU 5 by a ROM table or the like. Then, the correction value of the sensor signal corresponding to each sensor pixel coordinate is searched (step 11).

Here, not the correction value search by the table, but the inclination angle ω to η of the incident light flux corresponding to each sensor pixel.
(Ω) and cos ⁴ ω may be obtained and sequentially calculated.

Further, the sensor output image data for all the sensor pixels stored in step 10 is multiplied by the correction value retrieved in step S11, and the result is stored in the memory (step S12).

After this, steps S2 to S8 are executed in the same manner as the steps shown in FIG.

By setting the above-mentioned characteristic correction value to a value larger than 1, it is possible to avoid a decrease in the overall sensitivity as compared with the correction by the gradation filter.

[0037]

As described above, according to the lane departure warning apparatus of the present invention, the aperture efficiency due to vignetting of the wide-angle lens constituting the lane detection means and the inverse characteristic function of the lens characteristic of the cosine fourth law are calculated. Since the output signal of the one-dimensional linear image optical sensor is multiplied and corrected to be used as the output image signal of the lane detection means, it is possible to prevent a decrease in lane detection power due to the wide-angle lens characteristic, and to reliably detect the lane. It will be possible.

Further, since the correction value can be arbitrarily set, it is possible to promptly respond when the lens characteristic is changed.

Further, by setting the characteristic correction value to a value larger than 1, it is possible to avoid a decrease in the overall sensitivity as compared with the correction by the gradation filter.

[Brief description of drawings]

FIG. 1 is a graph showing a characteristic function for correcting a wide-angle lens characteristic in a lane departure warning system according to the present invention.

FIG. 2 is a waveform diagram for explaining the difference between the lane departure warning device according to the present invention and the conventional example.

FIG. 3 is a flowchart showing a control algorithm by the CPU of the lane departure warning system according to the present invention.

FIG. 4 is a block diagram showing in principle the configuration of a lane departure warning device of the present invention and a conventional example.

FIG. 5 is a diagram showing an arrangement in which the respective constituent portions of the lane departure warning device of the present invention and the conventional example are actually mounted in a vehicle.

FIG. 6 is a flowchart of a control program stored and executed in a signal processing means (CPU) in a conventional example.

FIG. 7 is a diagram showing a screen including lanes on a road surface detected by lane detection means.

FIG. 8 is a graph showing the aperture efficiency due to vignetting and the lens characteristics of the cosine fourth law in a wide-angle lens.

FIG. 9 is a graph showing the sensitivity of each pixel of the optical sensor that receives a light output signal from the wide-angle lens.

[Explanation of symbols]

 1 Lane detection means (line camera) 2 Vehicle speed sensor 3 Direction indicator 4 Warning device 5 Signal processing means (CPU) In the drawings, the same reference numerals indicate the same or corresponding parts.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location G08B 21/00 U 9177-5G G08G 1/00 J 7214-3H 1/16 C 7214-3H H04N 7 / 18 J

Claims (2)

[Claims] 1. A lane on a road surface is obtained by binarizing an image signal obtained from a lane detection means for photographing the front of the vehicle, which is composed of a wide-angle lens and a one-dimensional linear image optical sensor, by a signal processing means. A lane departure warning device that extracts and activates an alarm device when the vehicle-to-vehicle distance between the lane and the vehicle becomes a predetermined value or less and the vehicle speed is equal to or more than a set value and no direction indicating operation is performed. The processing means multiplies the output signal of the optical sensor by the inverse efficiency function of the aperture efficiency due to vignetting of the wide-angle lens and the lens characteristic of the cosine fourth law, and outputs the corrected value. A lane departure warning device characterized by being used as a signal. 2. The lane departure warning device according to claim 1, wherein a value of 1 or more is set as the correction value.