JPS6363077B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical radar device for detecting road surface conditions that uses light to detect whether or not there is an abnormality on the road surface in front of a vehicle.

Conventionally, while the vehicle is running, the driver visually checks the road surface condition ahead in the direction of travel, and this allows the driver to check the road surface condition with his or her own eyes.
The driver was aware of any abnormalities on the road surface, such as oil slicks and scattered foreign objects, in order to drive safely.

However, as mentioned above, in the past, the driver's eyesight was the only way to check the road surface condition, which caused the driver's illusions and oversights due to glare caused by sunlight or poor eyesight due to fatigue. In some cases, it may not be possible to accurately grasp the road surface condition.

This invention was made in view of the above-mentioned problems. A light projector emits a signal light onto the road a predetermined distance ahead of the vehicle, and a light receiver receives the reflected signal light reflected from the road surface. By detecting the detected reflected signal light and determining whether or not there is an abnormality on the road surface based on the strength of the detected reflected signal light,
It is an object of the present invention to provide an optical radar device for detecting road surface conditions that can detect whether or not there is an abnormality on the road surface in front of a vehicle in advance and reliably.

Embodiments of the optical radar device for detecting road surface conditions according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a diagram showing an embodiment of the present invention, and the optical radar device shown in the same figure emits signal light,
It is generally composed of a light emitting and receiving unit 1 that receives light, and a control circuit 10 that controls the light emitting and receiving of the light emitting and receiving unit 1 and detects road surface conditions.

The light emitting/receiving unit 1 is equipped with a light emitter 2 and a light receiver 6 inside, and as shown in FIG. 2, for example,
It is installed on the roof 30 of the vehicle (in addition, on the front grill, near the room mirror in the vehicle interior, on the instrument panel, etc.).

The light projector 2 includes a light emitting element 3 such as a semiconductor laser driven by a drive signal a output from a modulator 11 in the control circuit 10, and a signal light Lt such as a laser beam generated from the light emitting element 3. a condenser lens 4 that condenses the light into a beam having a radiation angle φt;
Driven in response to a deflection angle setting signal Vθ supplied from the deflection angle calculation circuit 15 in the control circuit 10;
An optical deflector 5 ( _e.g. , one utilizing an acousto-optic effect or an electro-optic effect, or It is generally composed of a mechanism that changes the mirror rotation angle in response to an electric signal.

The light receiver 6 includes a condenser lens 7 that condenses the reflected signal light Lr that the signal light Lt returns after being reflected on the road surface 20, and a condenser lens 7 that receives the condensed reflected signal light Lr and performs photoelectric conversion on the reflected signal light Lr. , a light-receiving element 8 that outputs the light-receiving signal b, and backlight noise (sunlight, artificial illumination light, etc.) that is interposed between the condensing lens 7 and the light-receiving element 8 and irradiated from the condensing lens 7. and an optical filter 9 that removes the reflected signal light Lr component and guides only the reflected signal light Lr component onto the light receiving element 8.

Then, the center of the condensing lens 7 and the light receiving element 8
The optical axis g connecting the centers of the light-receiving surfaces 8a is inclined by a predetermined angle of inclination θ ₂ with respect to the parallel line j with the road surface, thereby efficiently condensing the reflected signal light Lr. It is configured so that it can be done.

The control circuit 10 includes a modulator 11 that supplies a drive signal a to the light emitting element 3 and a light receiving element 8.
a narrowband amplifier 12 that amplifies the received light signal b output from the narrowband amplifier 12; a rectifier circuit 13 that rectifies the output c from the narrowband amplifier 12; reference voltage level (reflected signal light on normal road surface)
(corresponding to the strength of Lr), “H”,
Comparator 14 that outputs “L” binary signal e
Based on the voltage Va proportional to the vehicle speed supplied from the vehicle speed sensor 16, the signal light Lt is always at least within the safe braking distance corresponding to the current traveling speed.
It is comprised of a deflection angle calculation circuit 15 which calculates a deflection angle setting signal Vθ by a predetermined calculation and supplies it to the optical deflector 5 so that the front can be illuminated by Ra.

The deflection angle setting signal Vθ output from the deflection angle calculation circuit 15 is derived from the following relational expression.

First, between the angle of inclination θ ₁ (θ ₁ <<1) of the signal light Lt, the safe braking distance Ra, and the height h of the light emitting/receiving unit 1 from the road surface shown in FIG. 2, θ ₁ ≒ There is a relationship h/Ra...(1), and the safe braking distance Ra mentioned above is determined by the following formula for the traveling speed v of the vehicle. (The safe braking distance should be considered the distance from the front of the vehicle, but here we will consider the distance from the light emitter/receiver unit 1.) Ra=v ² /2α+vTd...(2) Note that α is the distance from the front of the vehicle. Deceleration when trying to stop by applying the brakes (0.5G, G is gravitational acceleration),
Td is the response delay time (approximately 2 seconds) from when the driver recognizes an abnormality to when the driver starts braking.

In these relational expressions, the output voltage Va proportional to the vehicle speed from the vehicle speed sensor 16 is substituted for the vehicle speed v in the above formula (2), and the deflection angle setting signal Vθ is substituted for the dip angle θ ₁ in the above formula (1). Accordingly, Vθ≒h/(Va ² /2α+VaTd) ...(3) is obtained.

Therefore, if the inclination angle θ ₁ of the signal light Lt is varied by the deflection angle setting signal Vθ determined based on the above formula (3), the safe braking distance Ra corresponding to the vehicle speed v can always be adjusted.
The road surface condition in front of the vehicle can be detected, and if an abnormality in the road surface is detected and the driver attempts to stop the vehicle, the vehicle can be safely stopped in front of the abnormal point.

In the light receiver 6, the light receiving surface 8a of the light receiving element 8 is installed at the focal point F of the condensing lens 7, and the aperture D of the light receiving surface 8a of the light receiving element 8 is
The light receiving visual angle φr of the light receiver 6 is determined by .

That is, if the focal length of the condensing lens 7 is f, then the following relationship holds: φr≈D/f (4).

And, actually, the above-mentioned light receiving visual angle φr (radian)
By setting the receiving viewing angle φr to a fairly wide angle such that the angle is 5 (deg), the above signal light Lt
Even if the angle of incidence of the reflected signal light Lr on the receiver ₆ changes due to the change in the inclination angle θ 1 of the reflected signal light Lr from the reflection center P on the road surface in front of the safe braking distance Ra shown in It can always receive light.

The operation of detecting road surface conditions in the optical radar device configured as described above will be described below.

First, the modulator 11 in the control circuit 10 outputs a drive signal a with a frequency f ₀ as shown in FIG.
When a sine wave signal (for example, 100 KHz) is output, the light emitting element 3 of the projector 2 emits signal light Lt modulated by the drive signal a as shown in FIG. 3B.

After this signal light Lt is focused by the condensing lens 4,
In the light deflector 5, the light is changed in the direction of the inclination angle _θ1 set based on the deflection angle setting signal Vθ, and is irradiated onto the road surface 20 ahead of the safe braking distance Ra corresponding to the vehicle speed.

Then, the reflected signal light Lr, in which a part of the signal light Lt is reflected by the road surface 20 and returns, is received by the light receiver 6, and a light reception signal b as shown in FIG. 3C is output from the light receiving element 8. be done.

After the received light signal b is amplified as a sine wave signal component by a narrowband amplifier 12 having a center frequency f ₀ as shown in FIG.
3 and the rectified voltage d as shown in Figure 3E.
becomes.

Then, the level of the rectified voltage d is compared with the reference voltage level s in the comparator 14, and if the condition of the road surface 20 is normal, the level of the rectified voltage d is equal to or higher than the reference voltage level s. Yes, output e of comparator 14
becomes "L" as shown in FIG. 3F.

Further, if there is an abnormality on the road surface 20 (a depression in the road surface, an oil film, etc.), the signal light Lt is diffusely reflected by the abnormal road surface, and the reflected signal light Lr is reflected back to the light receiver 6. The amount of light will be reduced,
Therefore, the level of the rectified voltage d becomes lower than the reference level s, and the output e of the comparator 14 becomes "H".
becomes.

Therefore, the output e of the comparator 14 is supplied to an alarm drive circuit (not shown), etc., and when the output e becomes "H", a predetermined alarm is activated to alert the driver to an abnormality on the road surface ahead. By alerting the driver of the presence of a road surface and alerting the driver, it is possible to reliably check the road surface condition.

Note that in the above embodiment, the inclination angle θ ₁ of the signal light Lt
The vehicle speed v is used as a parameter to set the angle of inclination θ ₁ in correspondence with the safe braking distance obtained by detecting rain, snow, etc. and adding this as a parameter. If configured to set , safety can be further improved.

Further, when there is an obstacle in front, the light amount of the reflected signal light Lr is large, so that
If the comparator 14 is configured to determine that there is an obstacle ahead when the level of the rectified voltage d exceeds the reference voltage level s, and to notify the driver of this, the road surface condition can be seen in more detail. can be detected.

As explained above, the optical radar device for road surface condition detection according to the present invention can detect whether or not there is an abnormality on the road surface in front of the vehicle in advance and reliably. This has the advantage that the driver no longer overlooks abnormalities on the road surface or has any illusions, and can drive more safely.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of an embodiment of the optical radar device for detecting road surface conditions according to the present invention, Fig. 2 is a side view showing an example in which the device is mounted on a vehicle, and Fig. 3 is a diagram showing the main components of the device. FIG. 3 is a diagram showing an output waveform. 2... Emitter, 6... Light receiver, 10... Control circuit, 14... Comparator, Lt... Signal light, Lr
...Reflected signal light.

Claims (1)

[Scope of Claims] 1. Vehicle speed detection means that outputs a vehicle speed signal; A floodlight that emits signal light onto a road surface a predetermined distance ahead according to the vehicle speed signal; A reflected signal from which the signal light is reflected from the road surface. An optical radar device for detecting road surface conditions, comprising: a light receiver that detects light; and road surface condition discrimination means that discriminates whether there is an abnormality on the road surface based on the reflected signal light detected by the light receiver. .