JPH10170636A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep scan cycle of each light beam constant, eliminate interference between light beams, detect moving objects more accurately than the prior, in an optical scanner which is used to detect a moving object such as an automobile running on a road. SOLUTION: By scanning each light beam which is generated km pulse emission from plural luminescent elements 8a, 8b by means of a rotational polygon mirror 12, a moving object is detected. Luminescent elements 8a, 8b emit pulses in timing different for elements 8a, 8b, and optical separators 22a, 22b separate areas Aa, Ab scanned by light beams such that these areas are not on a same plane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device used for detecting a moving object such as a car running on a road.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 11, for example, this type of optical scanning device is installed on an upper part of a gantry or the like installed on a road R in front of a tollgate.

[0003] In the optical scanning device 1 _0, by scanning the two light beams obtained by pulsed light emitting elements in a predetermined period such as a semiconductor laser or the like rotary polygon mirror, each of the light beams, road Scanning is performed sequentially in fan-shaped areas Aa and Ab on different planes in a state of crossing R at a substantially right angle.

[0004] Then, the light beams emitted in this fan-shaped area Aa, the Ab is reflected by moving objects C such as road or car on the road R, the reflected light is again received by the optical scanning device 1 ₀ You.

At this time, the time required for projecting and receiving the light beam and the amount of light differ depending on whether the moving object C exists on the road R or not. By measuring the time required for projecting and receiving light, and further measuring the amount of light, the presence / absence, shape, moving speed, and the like of the moving object C are detected.

In the prior art, the following two structures are provided as optical systems for scanning a plurality of light beams in different areas Aa and Ab, respectively.

A plurality of light emitting elements are provided, and a rotating polygon mirror is provided for each light emitting element individually, and a light beam from each light emitting element scans each area Aa, Ab with each rotating polygon mirror. What you did.

A light beam from a single light emitting element is reflected and scanned by a single rotating polygon mirror, and a beam splitter is arranged on the reflected scanning optical path. With this beam splitter, a rotating polygon mirror is used. The reflected light beam is split into two to scan different areas Aa and Ab.

[0009]

However, the conventional configuration described above has the following problems.

In the former configuration, it is necessary to provide a plurality of rotary polygon mirrors in accordance with each light emitting element, so that the apparatus becomes expensive and an error occurs in the rotation speed of the plurality of rotary polygon mirrors. Therefore, it is difficult to make the scanning cycle of the light beam by each rotating polygon mirror the same.

In the latter configuration, the light power is reduced because the light beam is split by the beam splitter,
As a result, inconveniences such as insufficient detection of reflected light from a road surface on the road R or a moving object C such as an automobile due to insufficient light reception occur.

Further, in either case, when each light beam obtained by pulsed light emission is received by a single light receiving element, mutual interference occurs if the phase of each light beam is the same. In addition, the two cannot be distinguished at the time of light reception.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. When a plurality of light beams are scanned in different areas, the scanning periods coincide with each other, and the mutual interference of the light beams is reduced. An object of the present invention is to make it possible to detect a moving object or the like with higher accuracy than before.

[0014]

The present invention employs the following structure to solve the above-mentioned problems.

That is, the optical scanning device according to the first aspect of the present invention has a configuration in which each light beam obtained by pulsating a plurality of light emitting elements is scanned by a single rotating polygon mirror. Meanwhile, each light emitting element emits pulsed light at a different timing for each element,
There is provided an optical separating means for separating the scanning regions by the respective light beams so as not to be included in the same plane.

[0016] The above-mentioned optical separating means is defined in claim 2.
4. A reflecting surface of a rotating polygon mirror according to claim 3, wherein the reflecting mirror is arranged on a scanning optical path on which a light beam from each light emitting element is reflected by the rotating polygon mirror. May be configured to be inclined by a predetermined angle with respect to the rotation axis, or as described in claim 5, the irradiation optical axis of the light beam from each light emitting element with respect to the rotation polygon mirror, And can be configured to be inclined at a predetermined angle. In the configuration of the third aspect, as in the fourth aspect, the inclination angle of the reflection surface of the rotary polygon mirror can be set to be different for each light emitting element.

[0017]

FIG. 1 is a perspective view showing details of a light projecting section and an optical scanning section in an optical scanning apparatus according to an embodiment of the present invention, and FIG. 2 is a front view of FIG.

The optical scanning device 1 is installed above a gantry (not shown) installed on a road R in front of a tollgate, for example, and emits two light beams. 2 and each light beam from the light projecting unit 2 is
And a light receiving unit (not shown) that receives reflected light of each light beam emitted while scanning with the optical scanning unit 4.

The light projecting section 2 includes a pair of light emitting elements 8a and 8b composed of a semiconductor laser, an LED, or the like, and a pair of light projecting lenses 10 for converting the light from each of the light emitting elements 8a and 8b into a parallel light beam.
a and 10b, and a common optical axis 20a of one light emitting element 8a and the light projecting lens 10a and a common optical axis 20b of the other light emitting element 8b and the light projecting lens 10b are arranged in parallel with each other. ing. And each light emitting element 8a,
8b is controlled by a later-described timing pulse generation circuit 30 so as to emit pulses at different timings for each of the elements 8a and 8b.

The light scanning section 4 is composed of a single rotating polygon mirror 1.
The rotating polygon mirror 12 has a large number (in this case, six) of reflecting surfaces 13 formed in parallel with the rotation axis o along the circumferential direction, and the rotation axis o is Both optical axes 20
They are arranged so as to be orthogonal to the plane including a and 20b.

Further, in this embodiment, the rotary polygon mirror 1
The reflecting mirrors 22a and 22b are respectively arranged on the scanning optical path of each light beam reflected by each of the two reflecting surfaces 13.

Then, each of the reflecting mirrors 22a and 22b is arranged as shown in FIG.
As in the case shown in FIG. 5, while the light beam scanned with the rotation of the rotary polygon mirror 12 is reflected toward the road R, the scanning areas Aa and Ab of the light beam cross the road R at substantially right angles. Moreover, the reflection angles are set such that the scanning areas Aa and Ab are separated from each other by a predetermined distance E without being included in the same plane in the traveling direction of the road R. Therefore,
Each of these reflecting mirrors 22a and 22b corresponds to an optical separating means in the claims.

FIG. 3 is a block diagram showing a part of a light emission / reception control circuit of the optical scanning device 1 of this embodiment.

Referring to FIG. 1, reference numeral 30 denotes a timing pulse generating circuit; 32a and 32b light-emitting modules for driving the light-emitting elements 8a and 8b; And 36 are visual field discriminating circuits for identifying the output from the light receiving module 34.

Next, the operation of the optical scanning device 1 having the above configuration will be described.

The rotating polygon mirror 12 is driven to rotate at a constant speed by a motor (not shown), while the light emitting elements 8a and 8b are rotated.
Are synchronized with the light emission timing pulse output from the timing pulse generation circuit 30 and
Pulse emission is performed by a and 32b. In this case, pulse emission is performed at a different timing for each of the elements 8a and 8b (here, a timing in which the phase is shifted by 90 ° for each of the elements 8a and 8b).

The light from each of the light emitting elements 8a and 8b is converted into a parallel light beam by the light projecting lenses 10a and 10b, which is reflected by the rotary polygon mirror 12, and
Each light beam is reflected by the reflecting mirrors 22a and 22b to form a road R.
Out of the road.

In this case, since the rotating polygon mirror 12 is constantly rotated at a constant speed by a motor (not shown),
As shown in FIG. 11, the light beams reflected by the rotary polygon mirror 12 and the reflecting mirrors 22a and 22b cross the road R at a substantially right angle in a state where the scanning periods T are the same and the scanning directions are opposite. It is scanned like a fan. At this time, the scanning areas Aa and Ab of the respective light beams are denoted by a symbol E in the traveling direction of the road R.
Are scanned with the same scanning width W in the direction crossing the road R at the positions forward and backward by the distance indicated by.

Then, the reflected light of the light beam from the road surface of the road R or the moving object C such as a car is received by a common light receiving element, and the detection output is amplified by the light receiving module 34 and taken out.

In this case, since the phase of the pulse light emission of each light beam is shifted, the field-of-view discrimination circuit 36 synchronizes with the light emission timing pulse from the timing pulse generation circuit 30 so that the two scanning areas Aa and Ab are not scanned. Each of the scanning areas A is identified by detecting which one of the light beams is the detection output.
The detection signals corresponding to a and 8b are separated and output. For this reason, even when the reflected light from the road surface of the road R or the moving object C such as a car is received by a single light receiving unit, mutual interference of the reflected light beams can be prevented.

Each detection output identified and taken out by the visual field discriminating circuit 36 is input to a control circuit such as a microcomputer (not shown). For example, the speed and the speed of the moving object C are determined based on a flowchart shown in FIG. The dimensions are calculated.

That is, when the moving object C is a vehicle,
First, based on the light beam scanned one scanning region Aa, determine its time ta ₁ detects the start of the vehicle (step). Next, based on the light beam that scans the other scanning area Ab, the head of the vehicle is similarly detected and the time tb is detected.
Find ₁ (step). Subsequently, based on the light beam scanned one scanning region Aa, determine its time ta ₂ detects the trailing vehicle (step). Next, based on the light beam that scans the other scanning area Ab, the end of the vehicle is also detected and the time tb ₂ is obtained (step
). Then, the vehicle speed v and the vehicle length l are obtained from these times ta ₁ , tb ₁ , ta ₂ , tb ₂ and the distance E between the scanning areas Aa, Ab (step,).

(Other Embodiments) The following various modifications can be made to the above embodiment.

(1) In the embodiment shown in FIGS. 5 and 6, instead of providing the reflecting mirrors 22a and 22b as shown in FIG. 2, the reflecting surface 13 of the rotating polygon mirror 12 is moved with respect to the rotation axis o. At a predetermined angle θ. In this case, the inclination angle θ of the reflecting surface 13 is such that the scanning areas Aa and Ab of the light beam cross the road R at substantially right angles, respectively, as shown in FIG. 11, and the scanning areas Aa and Ab
Are set not to be included in the same plane in the traveling direction of the road R and to be separated by a predetermined distance E.

In the embodiment shown in FIGS. 5 and 6, the structure of the optical system is simplified by the elimination of the reflecting mirrors 20a and 20b, but the processing accuracy of the reflecting surface 13 of the rotary polygon mirror 12 is required.

The other configurations and operations are the same as those of the embodiment shown in FIGS. 1 to 4, and a detailed description thereof will be omitted.

(2) In the embodiment shown in FIGS. 7 and 8, instead of providing the reflecting mirrors 22a and 22b as shown in FIG.
The reflecting surfaces 13a and 13b are formed so as to be orthogonal to the two optical axes 20a and 20b, and have different directions with respect to the rotation axis o, respectively, corresponding to the light emitting elements 8a and 8b. That is, one reflecting surface 13a is tilted counterclockwise by a predetermined angle θa, and the other reflecting surface 13b is tilted clockwise by a predetermined angle θb. In this embodiment, the magnitudes of the angles θa and θb are the same, but may be different.

In the embodiment shown in FIGS. 7 and 8, the distance E between the scanning areas Aa and Ab is arbitrarily changed by setting the inclination angles θa and θb of the reflecting surfaces 13a and 13b, respectively. And each scanning area Aa, Ab
Since the scanning directions of the light beams are the same, the signal processing after light reception becomes easy. Further, the reflecting mirrors 20a,
The structure of the optical system is simplified by the omission of 20b.

The other configurations and operations are the same as those of the embodiment shown in FIGS. 1 to 4, and a detailed description thereof will be omitted.

(3) In the embodiment shown in FIGS. 9 and 10, instead of providing the reflecting mirrors 22a and 22b as shown in FIG. 2, the optical axis 2 of the light beam from each of the light emitting elements 8a and 8b is used.
The reference numerals 0a and 20b are arranged to be inclined by predetermined angles θa and θb with respect to the rotation axis o of the rotary polygon mirror 12, respectively.

Also in the embodiment shown in FIGS. 9 and 10, the structure is simplified because the reflecting mirrors 20a and 20b can be omitted, but the arrangement of the light emitting elements 8a and 8b and the optical system of the retroreflective plate 12 is adjusted. Precision is required.

Other configurations and operations are the same as those of the embodiment shown in FIGS. 1 to 4, and therefore detailed description is omitted.

In each of the above embodiments,
The light projecting section 2 is composed of a pair of light emitting elements 8a and 8b and light projecting lenses 10a and 10b, respectively, but may be configured to have three or more light emitting elements and a light projecting lens. By doing so, it is possible to further improve the resolution in the traveling direction of the road R.

Further, in each of the above embodiments, the case where the optical scanning device 1 is installed above the road R has been described, but it is also possible to install the optical scanning device 1 on the road side. By arranging at this position, the cross-sectional shape of the moving object C viewed from the side surface can be measured, so that when the moving object C is like a vehicle, the number of axes and the like can be detected.

[0045]

According to the present invention, the following effects can be obtained.

(1) According to the first aspect of the present invention, when a plurality of light beams are scanned in different regions, the respective scanning periods coincide with each other, and the mutual interference of the light beams is eliminated. In addition, a moving object or the like can be detected with higher accuracy.

(2) In the structure of the second aspect, in addition to the effect of the first aspect, the shape of the rotary polygon mirror can be made thinner and the size can be reduced.

(3) In the configuration according to the third aspect, in addition to the effect according to the first aspect, the shape of the rotary polygon mirror can be reduced and the structure of the optical scanning unit can be simplified.

(4) In the structure of the fourth aspect, in addition to the effect of the first aspect, the scanning directions of the respective light beams can be made coincident, and signal processing after light reception is facilitated.

(5) In the structure of the fifth aspect, in addition to the effect of the first aspect, the structure of the optical system is simplified.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating details of a light projecting unit and an optical scanning unit of an optical scanning device according to an embodiment of the present invention.

FIG. 2 is a front view of FIG.

FIG. 3 is a block diagram showing a control circuit portion of the optical scanning device of FIG.

FIG. 4 is a flowchart for measuring a vehicle speed and a vehicle length by signal processing of the optical scanning device of FIG. 1;

FIG. 5 is a perspective view illustrating details of a light projecting unit and an optical scanning unit of an optical scanning device according to another embodiment.

FIG. 6 is a front view of FIG. 5;

FIG. 7 is a perspective view illustrating details of a light projecting unit and an optical scanning unit of an optical scanning device according to another embodiment.

FIG. 8 is a front view of FIG. 7;

FIG. 9 is a perspective view illustrating details of a light projection unit and an optical scanning unit of an optical scanning device according to another embodiment.

FIG. 10 is a front view of FIG. 9;

FIG. 11 is a perspective view showing a state where a conventional optical scanning device is installed on a road.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical scanning device, 2 ... Light projection part, 4 ... Optical scanning part, 8a, 8b
.., Light emitting elements, 10a, 10b light projecting lens, 12 rotating polygon mirror, 13, 13a, 13b reflecting surface, 22a, 22b reflecting mirror (optical separation means).

Claims (5)

[Claims] 1. A method in which each light beam obtained by emitting light from a plurality of light emitting elements is scanned by a single rotating polygon mirror, wherein each light emitting element is pulsed at a different timing for each element. An optical scanning device comprising: an optical separating unit that emits light and separates a scanning region by each light beam so as not to be included in the same plane. 2. The optical scanning device according to claim 1, wherein the optical separating unit is configured by arranging a reflecting mirror on a scanning optical path on which a light beam from each light emitting element is reflected by the rotary polygon mirror. An optical scanning device, comprising: 3. An optical scanning device according to claim 1, wherein said optical separating means is configured by inclining a reflecting surface of a rotary polygon mirror by a predetermined angle with respect to a rotation axis. Scanning device. 4. The optical scanning device according to claim 3, wherein the inclination angle of the reflecting surface of the rotary polygon mirror is set to be different for each light emitting element. . 5. The optical scanning device according to claim 1, wherein the optical separation unit sets an irradiation optical axis of a light beam from each light emitting element to the rotary polygon mirror with respect to a rotation axis of the rotary polygon mirror. An optical scanning device, wherein the optical scanning device is configured to be inclined at an angle.