JPH0829537A - Distance measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain a small-sized distance measuring apparatus which can detect the distance to an object positively with no error at low cost. CONSTITUTION:In an apparatus for detecting the distance to an object by receiving the light reflected on the object on the light receiving element 1 side through an optical means 3, the light receiving element 1 is covered partially with an extinction filter 2. Consequently, the small-sized inexpensive extinction filter 2 can lower the detection sensitivity of reflected light incoming from the right and left sides in front of a vehicle. Since only such vehicles as present in the vicinity of a host vehicle can be detected among forward vehicles running on the right and left sides thereof, erroneous detection of a vehicle approaching the host vehicle on an adjacent lane can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device for detecting a distance to an object by causing reflected light of light radiated toward the object to be received by a light receiving element side through an optical means. It is a thing.

[0002]

2. Description of the Related Art For example, a distance measurement in which a laser beam is irradiated toward an object, the reflected light is condensed by an optical means such as a convex lens or a concave mirror, and the distance is measured based on a time difference from light transmission to light reception. The device is known. For example, this distance measuring device is put to practical use as an inter-vehicle distance warning device that measures the distance to a preceding vehicle traveling ahead by being mounted on an automobile and issues an alarm when a danger of a rear-end collision occurs. There is.

FIG. 4 shows a state in which a vehicle traveling lane on a road is viewed from above. In the figure, C1 is an automobile equipped with a distance measuring device (not shown). Then, a preceding vehicle C2 is traveling at a distance R in front of the automobile C1. In this case, if the width of the traveling lane T is W, the horizontal detection angle α of the preceding vehicle C2 due to the irradiation light from the automobile C1 is α = 2 tan −1 (W / 2R).

Since the width W of the traveling lane T is generally constant (for example, 3.5 m), the preceding vehicle C2 cannot be sufficiently detected unless the detection angle α changes according to the distance R. At the same time, false detection will occur. That is,
If the detected angle α is constant and smaller than the required value, the preceding vehicle C2 traveling at a short distance cannot be detected at the end of the traveling lane T. Conversely, if the detected angle α is constant and larger than the required value. However, there is a problem in that a traveling vehicle in the adjacent oncoming lane is erroneously detected at a long distance.

In order to solve this problem, as shown in FIG. 5, a distance measuring device includes, for example, three light sources 101, 1
02, 103, and the light sources 101, 102, 103
The light is emitted in three directions via the lens 104. In this case, as shown in FIG. 6, by shortening the irradiation distance of the emitted light L2 on both sides with respect to the emitted light L1 at the center (for example, about 35 m), traveling of the adjacent opposite lane traveling a long distance is performed. It prevents you from accidentally detecting a car.

[0006]

However, since the above-mentioned conventional distance measuring device requires three light sources,
There is a problem that three light emitting elements are required and an electric circuit for driving the light emitting elements is complicated, resulting in an increase in size and cost of the device.

The present invention has been made to solve the above problems, and provides a small-sized and low-cost distance measuring device capable of surely detecting the distance to an object without erroneous detection. The purpose is to

[0008]

According to the invention of claim 1 of the present invention, the reflected light of the light radiated toward the object is received by the light receiving element side through the optical means to reach the object. In a distance measuring device for detecting a distance, a part of a light receiving element is covered with a neutral density filter.

According to a second aspect of the present invention, in the case of the first aspect of the invention, the neutral density filter has a light transmittance, a position of the neutral density section with respect to a light receiving element of the neutral density filter, and a neutral density section. Is provided with a changing means for changing the area.

[0010]

For example, when the distance measuring device is mounted on a vehicle, both sides of the opening of the light receiving element are covered with a neutral density filter to limit the reflected light entering the light receiving element from the left and right sides in front of the vehicle. To do so. As a result, the detection sensitivity of the reflected light coming from both the left and right sides of the front of the vehicle can be reduced, so that only the one near the vehicle among the preceding vehicles traveling on the left and right sides of the vehicle is detected and the distance is measured. This makes it possible to prevent a vehicle traveling in the opposite lane from being erroneously detected.

Further, by changing the light transmittance of the neutral density filter, the position of the neutral density section with respect to the light receiving element of the neutral density filter, and the area of the neutral density section by the changing means, for example, in the driving situation of the vehicle. Accordingly, it becomes possible to properly detect the preceding vehicle (measure the distance to the preceding vehicle).

[0012]

Embodiments of the present invention will be described below with reference to the drawings. Example 1. FIG. 1 is a perspective view of a light receiving element of a distance measuring device according to an embodiment of the first aspect of the present invention, and FIG. 2 is an operation explanatory view of the light receiving element.

In the figure, 1 is a cover glass 1a on the front side.
Is attached, and a light-receiving opening 1c is formed in the center of the rear main body 1b of the cover glass 1a. A photoelectric element that converts light into an electric signal is arranged inside the main body 1b of the light receiving element 1. Reference numeral 2 denotes a pair of neutral density filters attached to the surface of the cover glass 1a of the light receiving element 1. The neutral density filter 2 is a commercially available plastic sheet filter used for photography and the like, and a pair of the cover glass 1 covers the left and right thirds of the opening 1c of the light receiving element 1.
It is attached to a. Reference numeral 3 is a convex lens as an optical means for making the reflected light coming from the outside converged and making it enter the opening 1c of the light receiving element 1. The convex lens 3 is arranged in front of the light receiving element 1 by a focal length f.

The distance measuring device includes a light transmitting unit (not shown) for irradiating an object with a predetermined laser beam,
A controller (not shown) that controls the light receiving unit (not shown) that receives the reflected light of the laser light from the object and the light sending unit, and that calculates the distance to the object by the time difference between the light sending and the light receiving. )) Etc. The light receiving unit is the above light receiving element 1,
It is composed of a neutral density filter 2, a convex lens 3 and the like.

Next, the operation of the neutral density filter 2 and the like will be described with reference to FIG. In the figure, R1 is the incident angle of the reflected light from the object centered on the convex lens 3 of the central reflected light entering the center of the opening 1c of the light receiving element 1 to which the neutral density filter 2 is not attached. The area is shown. The incident angle region R1 exists within a range of an angle (θ1) / 2 centered on the optical axis A. And the angle θ
1 is an opening 1 in a portion of the light receiving element 1 where the neutral density filter 2 is not provided
If the width of c is a, then θ1 = 2tan-1 (a / 2f).

Of the reflected light L from the object, R2 is centered on the convex lens 3 of the end reflected light incident on the left or right part of the aperture 1c of the light receiving element 1 to which the neutral density filter 2 is attached. The incident angle region is shown. In this case, the angle θ2 is represented by θ2 = tan-1 (1.5a / f).

Here, assuming that other factors do not change the detection distance S in front of the convex lens 3 formed by the light receiving element 1,
It is considered to be proportional to the fourth root of the transmittance Tr of the optical system.
Therefore, the detection distance S is represented by S = k (Tr) ^1/4 , where k is a proportional constant.

Therefore, by setting the transmittance of the neutral density filter 2 to a predetermined value, as shown in FIG. 3, the detection distance S2 for the end reflected light is sufficiently made to the detection distance S1 for the central reflected light. Can be set small. That is, the distance to the distant object can be detected by the central reflected light entering from the incident angle region R1 on the optical axis A side, and the center reflected light entering from the outer incident angle region R2 away from the optical axis A can be detected. It is possible to detect the distances to the objects near the left and right sides that are deviated from the reflected light.

Next, the operation when the distance measuring device is mounted on a vehicle will be described. First, in response to a command from a controller (not shown), detection light is emitted from a light source of a light transmitting unit (not shown) toward a preceding vehicle (object) in front of the vehicle. In this case, the spread angle θ3 of the light transmitted forward of the vehicle about the optical axis A of the detected light is the maximum angle θ2 of the end reflected light as shown by the broken line in FIG.
Bigger than.

When the preceding vehicle is traveling in the incident angle region R1 of the central reflected light, that is, the center of the traveling lane on the road, the reflected light of the detection light which hits the preceding vehicle is the central reflected light. The light enters the convex lens 3 side through the incident angle region R1 and is converged on a portion of the aperture 1c of the light receiving element 1 where the neutral density filter 2 is not provided. Therefore, even if the preceding vehicle is at a position apart from the vehicle equipped with the distance measuring device to some extent, the reflected light from the preceding vehicle is easily detected by the light receiving element 1.

Further, when the preceding vehicle is traveling near the vehicle equipped with the distance measuring device at the incident angle region R2 of the end reflected light, that is, on the left end or the right end side of the traveling lane, The reflected light of the detection light that hits is incident on the convex lens 3 side through the incident angle region R2 of the end reflected light, and is converged on a portion of the aperture 1c of the light receiving element 1 where the neutral density filter 2 is present. That is, due to the action of the neutral density filter 2, the light receiving element 1 detects the reflected light from the preceding vehicle only when the preceding vehicle is running near the vehicle equipped with the distance measuring device, and the distance measuring device is operated. Even if the vehicle is traveling in the opposite lane which is separated from the equipped vehicle to some extent, the reflected light from the vehicle is not detected.

The light receiving element 1 sends a detection signal to the controller by detecting the reflected light from the preceding vehicle. Then, the controller 3 calculates the distance to the preceding vehicle based on the time difference from the light transmission to the light reception, displays it on a display or the like to inform the driver, and if the inter-vehicle distance is smaller than a predetermined value, displays it. An alarm is issued via the etc. to inform the driver of this.

As described above, in this distance measuring device, only the small and low-cost and easily available neutral density filter 2 is attached to the surface of the light receiving element 1, and a distant object in front of the vehicle can be detected without erroneous detection. The object and nearby objects can be detected without exception, and the distance to this object can be reliably calculated. Therefore, the size and cost of the device can be reduced as compared with the conventional distance measuring device provided with a plurality of light sources.

Embodiment 2 FIG. This embodiment relates to a distance measuring device according to an embodiment of the second aspect of the present invention.

In the distance measuring device of the first embodiment, the light receiving element 1
Although the neutral density filter 2 having a constant light transmittance is fixedly attached to the cover glass 1a of the above, in the distance measuring apparatus according to this embodiment, the neutral density filter 2 has a light transmittance and the neutral density filter 2 as well. And a changing means capable of changing the position of the dimming portion with respect to the light receiving element and the area of the dimming portion.

For example, the neutral density filter 2 is provided with a liquid crystal filter, which is composed of a number of segments and serves as a changing means, and is attached to the cover glass 1a of the light receiving element 1 so as to close the opening 1c. The light transmittance of each segment of the liquid crystal filter can be electrically changed.
Then, the light transmittance of each segment of the liquid crystal filter is controlled according to the driving condition of the vehicle, such as the traveling speed and the steering wheel operating angle, so that the preceding vehicle can be detected in an optimum state at all times. To do.

Thus, for example, when the vehicle travels on a curved road (curve), by using the neutral density filter 2 having a liquid crystal filter as a changing means, the detection sensitivity of the reflected light from the turning direction side is increased. (Increasing the light transmittance) and lowering the detection sensitivity of reflected light coming from the opposite direction (reducing the light transmittance) will ensure the detection of the preceding vehicle without erroneous detection. become.

[0028]

Since the present invention is constituted as described above, it has the following effects.

According to the first aspect of the present invention, the distance to the object is detected by causing the reflected light of the light emitted toward the object to be received by the light receiving element side through the optical means. In the distance measuring device, a part of the light receiving element is covered with a neutral density filter so as to reduce the reflected light from a predetermined direction, so that the distance to the object can be reliably detected without erroneous detection. Also, the device can be made small and low cost.

According to the invention of claim 2 of the present invention, in the case of the invention of claim 1, the attenuating filter has a light transmittance, and the position and the attenuating part of the attenuating part with respect to the light receiving element of the attenuating filter. Since the area of the light section is provided with the changing means that can be changed, the distance to the object can be detected in correspondence with various situations.

[Brief description of drawings]

FIG. 1 is a perspective view around a light receiving element of a distance measuring device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating the operation of a neutral density filter.

FIG. 3 is an explanatory view of the operation of the neutral density filter.

FIG. 4 is a view of the traveling lane of the vehicle as seen from above.

FIG. 5 is an operation explanatory view of a light transmitting unit of a conventional distance measuring device.

FIG. 6 is an operation explanatory view of a conventional distance measuring device.

[Explanation of symbols]

1 light receiving element, 2 neutral density filter, 3 convex lens (optical means).

Claims (2)

[Claims] 1. Reflected light of light radiated toward an object,
By receiving light on the light receiving element side through the optical means,
A distance measuring device for detecting a distance to the object, wherein a part of the light receiving element is covered with a neutral density filter. 2. The neutral density filter is provided with changing means for changing the light transmittance, the position of the neutral density section with respect to the light receiving element of the neutral density filter, and the area of the neutral density section. 1. The distance measuring device according to 1.