JP2980503B2 - Light irradiation type distance measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light irradiation type distance measuring device which irradiates a target object with light from a luminous body, detects the return time of the reflected light, and measures the distance to the target object.

[0002]

2. Description of the Related Art Light irradiation type distance measuring devices have been used for non-contact or remote distance measurement in various fields.
For example, it is applied to an optical headway meter. The optical headway meter is mounted on a traveling vehicle body and includes a pair of light projecting means and light receiving means. Primary light including a central light beam and a peripheral light beam in a predetermined irradiation angle range is projected onto a target vehicle body in a predetermined distance region, and secondary light reflected from the target vehicle body is received to detect a return time of the secondary light beam, thereby detecting a headway. The distance is measured remotely and without contact.

[0003]

The problem of the conventional optical head-to-head meter will be briefly described with reference to FIG. In an optical head-to-head meter that measures an inter-vehicle distance with respect to a vehicle (a target vehicle body) traveling ahead along a predetermined lane 100, the primary light 101 is projected on a rear reflector of the target vehicle body and the reflected secondary light is reflected. The distance is determined by the return time of the light. Since the target vehicle body moves at any time in the lateral direction by the width of the lane 100, the lateral position of the reflector is not constant. Therefore, the light projecting means 103 mounted on the rear vehicle body 102 emits the primary light 101 diverging in the predetermined irradiation angle range 104 toward the target vehicle body in front, instead of the narrow beam shape. Accordingly, the primary light 101 includes a central light beam traveling along the center line 105 of the lane 100 and a peripheral light beam oblique to the center line 105. The detection area 106, which is included in the reachable distance of the central light beam and the peripheral light beam and can perform distance measurement, has a substantially fan shape as shown. The secondary light reflected from the object located outside the detection area 106 is weak and cannot be detected. As shown in the figure, when the irradiation angle range 104 is set relatively wide, the detection area 106 is enlarged accordingly, and a target vehicle body located in a relatively short distance area can be almost completely captured. However,
In the long-distance region, the detection area 106 extends beyond the target lane 100 to an adjacent lane. Accordingly, there is a problem that an object other than the target vehicle body is measured. Alternatively, when traveling on a one-lane road, if the detection area 106 is too wide, there is a risk of measuring an object other than the target vehicle body such as a road sign located at the shoulder of the road.

On the other hand, FIG. 5 shows a case where the irradiation angle range 104 is narrowed and set relatively narrow. In this case, the detection area 106 is located within the width of the lane 100 in a relatively long distance area, and there is no risk of measuring an object other than the target. However, since the detection area 106 is reduced in a relatively short distance area, there is a risk that the target vehicle body cannot be captured. As described above, the conventional optical head-to-head meter has a problem that it is not possible to capture the target vehicle body in both the long-distance region and the short-distance region in a necessary and sufficient manner.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned problems in the prior art, an object of the present invention is to provide a light irradiation type distance measuring apparatus capable of setting a detection area suitable for a target. The following measures were taken to achieve this purpose. That is, the light irradiation type distance measuring apparatus according to the present invention includes, as basic components, a pair of light projecting means and light receiving means mounted on the traveling vehicle body. Primary light including a central light beam and a peripheral light beam in a predetermined irradiation angle range is projected onto a target vehicle body in a predetermined distance region, and secondary light reflected from the target vehicle body is received to detect a return time of the secondary light beam, thereby detecting a headway. Measure the distance. Such a configuration is characterized in that there is provided a limiting unit that relatively suppresses the intensity of the peripheral light beam as compared with the central light beam. By suppressing the intensity of the peripheral light, against the target body by effectively keeping the central ray with respect to the target vehicle body with invalidating the target body the marginal rays in the far region
The effective irradiation angle range is narrowed. On the other hand, in the short distance region, the peripheral light beam is kept effective with respect to the target vehicle,
The effective irradiation angle range for the body is widened. The limiting means is provided with an attenuator which is interposed in the optical path of the primary light and relatively reduces the amount of transmission of the peripheral light beam.

[0006]

According to the present invention, the intensity of the peripheral light beam is relatively suppressed as compared with the central light beam. Therefore, the reach of the peripheral luminous flux is shorter than that of the central luminous flux. In a relatively long distance area, only the central luminous flux is effective, and the detection area can be reduced. In other words, the effective irradiation angle range is narrowed in the long-distance region, and objects other than the target vehicle body can be excluded from the detection area. On the other hand, in the relatively short distance region, the peripheral light flux in addition to the central light flux has a certain intensity, so that the detection area is not reduced, and the effective irradiation angle range is kept wide.
Therefore, it is possible to sufficiently capture the target vehicle body, and there is no possibility of falling into an undetectable state. In this way, by selectively suppressing the intensity of the peripheral light beam, it is possible to set a necessary and sufficient detection area in both the far and near distance regions.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a light irradiation type distance measuring apparatus according to the present invention.
It is a block diagram which shows the basic structure of the optical head-to-head meter which is a specific example of an apparatus . As shown in the figure, the optical head-to-head meter 1 is housed in a casing, and a traveling vehicle body (not shown)
Mounted on The inter-vehicle meter 1 comprises a light projecting means 2 and a light receiving means 3
It has. The light projecting means 2 projects the primary light 6 including the central light beam 4 and the peripheral light beam 5 in a predetermined irradiation angle range to a target vehicle (not shown) in a predetermined distance region. In this example, the light projecting means 2 is composed of a combination of a semiconductor laser 7 serving as a light source and a light projecting lens 8. The primary light 6 emitted from the semiconductor laser 7 is adjusted to a predetermined irradiation angle range by the light projecting lens 8,
The light is emitted forward through the emission window 9. The semiconductor laser 7 is driven by a drive circuit 10 and emits a pulse-modulated primary light 6 in response to a reference signal supplied from an oscillation circuit 11. On the other hand, the light receiving means 3 receives the secondary light 12 reflected from a target vehicle body (not shown). In this example, the light receiving means 3 is composed of a combination of a condenser lens 13 and a photodiode 14, and the secondary light 1 that has entered through the entrance window 15.
2 is focused by the condenser lens 13 and collected on the light receiving surface of the photodiode 14. The photodiode 14 outputs a pulse-like electric signal according to a change in the amount of received light. A phase comparison circuit 16 is connected to the photodiode 14. The phase comparison between the electric signal and a reference signal supplied from the oscillation circuit 11 is performed to detect a delay time. This delay time corresponds to the return time of the secondary light 12, and the return time increases as the distance to the target vehicle increases. The arithmetic circuit 17 calculates the inter-vehicle distance based on the detected return time and outputs the calculated distance to an external monitor or the like.

As a characteristic feature of the present invention, the light projecting means 2 includes a restricting means, and relatively suppresses the intensity of the peripheral light beam 5 as compared with the central light beam 4. In the present embodiment, this limiting means is constituted by an attenuator 18 and intervenes in the optical path through which the primary light 6 passes to relatively reduce the transmission amount of the peripheral light beam 5.
In this example, the attenuator 18 is attached to the emission window 9.
However, the position of the attenuator 18 is not limited to this, and may generally be interposed in the optical path through which the primary light 6 passes. The attenuator 18 relatively suppresses the intensity of the peripheral light beam 5 as compared with the central light beam 4, thereby disabling the peripheral light beam 5 in a long-distance region and keeping the central light beam 4 effective, thereby enabling the effective irradiation angle range. FA is narrowed. On the other hand, in the short-distance region, the peripheral light beam 5 is effectively held, and the effective irradiation angle range CA is widened.

Next, the operation of the optical head-to-head meter 1 shown in FIG. 1 will be described in detail with reference to FIG. As shown
An optical headway meter is mounted on a vehicle body 22 traveling along a predetermined lane 21, and the primary light 6 is emitted forward by a built-in light projecting means 2. Lighting means 2 as described above
Has a built-in attenuator for selectively attenuating only the peripheral light flux of the primary light 6. Relatively short distance region CR (for example, 3
(Within 0 to 40 m), the predetermined intensity is maintained even if the peripheral light beam is attenuated to some extent, and the level of the secondary light reflected and returned from the target vehicle body is maintained at a level that can be detected by the light receiving means. Therefore, the effective irradiation angle range CA is kept wide. On the other hand, a relatively long distance region FR (for example, 100
m), the intensity of the secondary light that is reflected back is weakened, so that the attenuated peripheral light beam component is so weak that it cannot be detected by the light receiving means. On the other hand, since the central light beam is not attenuated, it is reflected backward at a sufficiently detectable level. Therefore, in the long-distance region FR, the effective irradiation angle range FA is narrowed by only the central beam. As a result, the traveling vehicle body 22
As shown by a solid line, the detection area 23 of the optical head-to-head meter mounted on the vehicle is angularly wide in the short distance region CR and narrow in the long distance region FR. In this manner, it is possible to selectively capture only the target vehicle body traveling ahead in the both distance range under the necessary and sufficient conditions. On the other hand, when the peripheral light beam is not attenuated, the detection area 24 expands in the long-distance region FR as shown by the dotted line, and extends to the adjacent lane.

Finally, with reference to FIG. 3, several specific examples of the attenuator will be described. (A) shows an ND filter 3 as an attenuator.
In this example, a film-like material is adhered to the inner surface of the emission window 9. Instead of the film-like ND filter 31, a light-shielding material may be deposited or applied on the surface of the emission window 9 with a predetermined pattern to directly form the ND filter. The amount of attenuation of the peripheral light beam can be adjusted by the density of the light shielding area 32 on both sides, and the mask range of the peripheral light beam can also be adjusted by the width of the light shielding area 32. Thus, ND
By appropriately adjusting the density and the width of the light shielding region 32 included in the filter 31, the shape of the detection area can be freely set.

FIG. 3B shows an example of the ND filter 31 directly adhered or formed on the inner surface of the emission window 9. The difference from the ND filter shown in (A) is that the central transparent region 33 of the ND filter 31 is left in a circular shape. Therefore, in this example, it is possible to attenuate the peripheral light flux included in the primary light not only in the horizontal direction but also in the vertical direction, and the shape of the detection area can be three-dimensionally adjusted.

In the example shown in FIG. 2C, two plate-shaped ND filters 31 are used, and are fixed to both sides of a frame member 34 supporting the light projecting lens 8 using screws 35, respectively.

In the embodiment described above, the present invention is applied to an optical headway meter. However, the applicable range of the present invention is not limited to the optical head-to-head meter,
The present invention is widely and generally applicable to a light irradiation type distance measuring device. That is, the light irradiation type distance measuring apparatus according to the present invention irradiates a target with light from a light emitter, detects the return time of the reflected light, and measures the distance to the target. It is characterized in that a means for restricting a peripheral light beam is attached in front of the light emitter. This means can be constituted by, for example, an attenuator whose light transmittance is reduced only for the peripheral light beam.

[0014]

As described above, according to the present invention, the effective illuminating angle range can be narrowed in a long-distance region and the short-distance range can be achieved by relatively suppressing the intensity of the peripheral luminous flux as compared with the central luminous flux. The effective irradiation angle range is widened in the region to optimize the detection area. For this reason, an effect is obtained that the distance measurement of the target can be executed without error in the distance range.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of an optical headway meter according to the present invention.

FIG. 2 is a schematic diagram for explaining the operation of the optical headway meter shown in FIG.

FIG. 3 is a plan view showing a specific example of an attenuator incorporated in the optical headway meter shown in FIG.

FIG. 4 is a schematic diagram for explaining a problem of a conventional optical head-to-head meter.

FIG. 5 is a schematic view for explaining a problem of the conventional optical head-to-head meter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical inter-vehicle meter 2 Light emitting means 3 Light receiving means 4 Central light flux 5 Peripheral light flux 6 Primary light 7 Semiconductor laser 8 Light emitting lens 9 Outgoing window 10 Drive circuit 11 Oscillation circuit 12 Secondary light 13 Condensing lens 14 Photodiode 15 Incident Window 16 phase comparison circuit 17 operation circuit 18 attenuator 21 lane 22 running vehicle body 23 detection area 31 ND filter

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hideki Kajioka 1-2-2, Goshodori, Hyogo-ku, Kobe-shi, Hyogo Prefecture Inside Fujitsu Ten Co., Ltd. (56) References JP-A-55-78267 (JP, A) Kaihei 4-87487 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01S 7/48-7/51 G01S 17/00-17/95

Claims (2)

(57) [Claims] A pair of light emitting means mounted on a traveling vehicle body and
And a light receiving means.
And primary light including ambient light flux within a predetermined distance range
Secondary light that is projected onto the vehicle body and reflected from the target vehicle body
Receives light and detects the return time to measure the distance between vehicles
In the light irradiation type distance measuring device, the intensity of the peripheral light beam is relatively suppressed as compared with the central light beam.
Limiting means for disabling the peripheral luminous flux with respect to the target vehicle body in a long-distance region
Also, keep the central luminous flux effective against the target
The effective irradiation angle range for the target vehicle body has been narrowed to a short range.
To effectively hold the peripheral luminous flux with respect to the target vehicle body and
The feature is to widen the effective irradiation angle range for the body
Light irradiation type distance measuring device. 2. The optical system according to claim 1 , wherein said restricting means is provided in an optical path through which said primary light passes.
Attenuator that intervenes and reduces the amount of transmitted light
2. A light irradiation type distance measuring apparatus according to claim 1, wherein the distance measuring apparatus comprises:
Place.