JPH10170637A - Optical scanning device - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To provide a light scanning device for detecting a moving object or the like by scanning each light beam obtained by pulsating a plurality of light emitting elements with a rotary polygon mirror, and operating and operating each light emitting element. The resolution of each of the scanning direction and the direction orthogonal thereto is increased without deteriorating the stability of. SOLUTION: Each light emitting element 8a, 8b is composed of each element 8a, 8b.
Each pulse is emitted at a timing different from each other, and optical adjusting means 22a and 22b are provided for adjusting the scanning areas of the light beams scanned by the rotary polygon mirror 12 so as to substantially overlap each other.

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 As a conventional optical scanning apparatus of this type, for example, there is one having a configuration shown in FIG.

[0003] The optical scanning device 1 ₀ is, for example bridged been gantry on the road R in front of the tollgate (not shown) are disposed to the upper portion such as a light projecting section 2 for emitting a light beam A light scanning unit 4 for scanning the light beam from the light projecting unit 2 in a fan shape across the road R, and a light receiving unit 6 for receiving reflected light of the light beam emitted while scanning with the light scanning unit 4 And

The light projecting unit 2 includes a single light emitting element 8 such as a semiconductor laser or an LED, and a single light emitting lens 10 for converting light from the light emitting element 8 into a parallel light beam. Also,
The optical scanning unit 4 includes a single rotating polygon mirror 12 and a motor 14 for rotating the same at a constant speed. Further, the light receiving unit 6 includes a light receiving lens 16 that collects light reflected from a moving object C such as a road R or an automobile, and a PD (light receiving device) that receives the light collected by the light receiving lens 16 and converts the light into an electric signal. And a light receiving element 18 such as a photodiode.

[0005] In the optical scanning device 1 ₀ of the above structure, the light-emitting element 8 of the light projecting section 2 is pulsed emission with a predetermined period. The reason why the light emitting element 8 emits a pulse light is to extend the life of the element 8 and to remove the influence of sunlight. The period of the pulse emission, of course, the optical scanning device 1 ₀
For example, it is set to 50 μsec so as to be longer than the time required for the light beam to make one round trip between the road and the road R.

Then, the light from the light emitting element 8 is converted into one parallel light beam by the light projecting lens 10,
This is reflected by the rotating polygon mirror 12 and emitted toward the road R. In this case, since the rotating polygon mirror 12 is always rotated at a constant speed by the motor 14, the rotating polygon mirror 12
Are sequentially scanned in a fan-like manner in one plane while crossing the road R at a substantially right angle.

[0007] Here, when on the road R no moving objects C such as an automobile, the light beam emitted from the optical scanning device 1 ₀ is as reflected in the road surface, the reflected light optical scanning device 1 The light enters the light receiving unit 6 of ₀ . Then, the reflected light is condensed by the light receiving lens 16, then received by the light receiving element 18, converted into an electric signal, and output.

On the other hand, if there moving object C is on the road R, the light beam emitted while being sequentially scanned from the light scanning apparatus 1 _0, because it is reflected by the vehicle C in the course to reach the road surface The time required to receive light by the light receiving element 18 is shorter than when the moving object C does not exist. Therefore, the presence or absence and the shape of the moving object C are detected by measuring the time required for light projection and reception by a signal processing circuit (not shown).

[0009]

By the way, as in the prior art, one light beam from the light emitting section 2 is rotated by the rotating polygon mirror 1.
2, the resolution in the length direction in which the moving object C moves and the resolution in the width direction orthogonal to the moving object C are ΔL and ΔW, respectively.
Has the following relationship:

ΔL = V · T (1) ΔW = Δt · W / T (2) (where V is the moving speed of the moving object C, T is the time required for one scanning of the light beam (scanning cycle), W: scanning range of the light beam, Δt: pulse emission period of the light beam)
Even when the shape of the moving object C is small and the moving speed is fast, it is preferable that both resolutions ΔL and ΔW are both high (fine) in order to accurately detect the shape and the like.

Here, when the scanning range W of the light beam is kept constant, to increase both resolutions ΔL and ΔW,
As can be seen from the relations of equations (1) and (2), the rotating polygon mirror 12
May be rotated at a high speed to shorten the scanning period T of the light beam, and the pulse emission period Δt of the light emitting element 8 may be shortened by the shortened scanning period T.

However, there is a limit to shortening the pulse light emission period Δt in particular, especially in the case where the light emitting element 8 is a semiconductor laser, in terms of securing operation stability and maintaining the life.

As described above, since there is a limit in shortening the pulse emission period Δt, in order to increase the resolution ΔW in the width direction in equation (2), the scanning period T of the light beam may be increased. Then, as can be seen from equation (1),
The resolution ΔL in the length direction is deteriorated. On the other hand, if the scanning period T of the light beam is shortened, the resolution ΔL in the length direction can be reduced.
Becomes higher, but conversely, the resolution ΔW in the width direction becomes worse.

That is, in the conventional device, since ΔL and ΔW have a trade-off relationship, both resolutions ΔL and ΔW cannot be made high (fine).

The present invention has been made in order to solve the above-mentioned problems, and it is possible to increase both the resolution in the length direction and the resolution in the width direction without shortening the pulse emission period of the light emitting element. The task is to be able to do it finely).

[0016]

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

That is, in the invention according to claim 1,
A configuration in which each light beam obtained by pulsing a plurality of light emitting elements is scanned by a single rotating polygon mirror,
In this case, each light emitting element is provided with optical adjustment means for adjusting the scanning area of each light beam so as to substantially overlap each other while emitting pulses at different timings for each element.

As the above-mentioned optical adjusting means, as described in claim 2, a reflecting mirror is arranged on a scanning optical path on which a light beam from each light emitting element is reflected by a rotating polygon mirror. The reflecting surface of the rotary polygon mirror may be configured to be inclined by a predetermined angle with respect to the rotation axis as described in claim 3, or the light beams from the respective light emitting elements may be combined and rotated as described in claim 4. The light-emitting element may be constituted by a beam splitter for irradiating the polygonal mirror, or each light-emitting element may be arranged in parallel with the rotary polygonal mirror, and the length of the rotary polygonal mirror in the direction of the rotation axis is the outermost end. And the light emitting element is formed to be longer than the distance between the optical axes of the two light emitting elements. Further, as described in claim 6, the reflecting surface of the rotating polygon mirror is arranged for each light emitting element in the direction of rotation. Along with each other by a predetermined angle. Benefit can be.

[0019]

FIG. 1 is a perspective view showing an optical scanning device according to an embodiment of the present invention installed on a road, and FIG.
3 is a perspective view showing details of a light projecting unit and an optical scanning unit of the optical scanning device, and FIG. 3 is a front view of FIG.

This optical scanning device 1 is installed on an upper part of a gantry (not shown) installed on a road R in front of a tollgate, for example, and emits two light beams. A light scanning unit 4 that scans each light beam from the light projecting unit 2 in a fan shape across the road R, and receives reflected light of each light beam emitted while scanning with the light scanning unit 4 And a light receiving unit 6 for performing the operation.

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 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. As shown in FIG. 1, each of the reflecting mirrors 22a and 22b reflects a light beam scanned by the rotation of the rotary polygon mirror 12 toward the road R, and forms two scanning areas formed by the reflecting light beam. The reflection angles are set such that Aa and Ab substantially overlap each other in the direction crossing the road R. Therefore, each of these reflecting mirrors 22a and 22b corresponds to an optical adjusting unit in the claims.

The light receiving section 6 is a light receiving lens 16 for collecting light reflected from the road surface of the road R or a moving object C such as a car, and the light received by the light receiving lens 16 is converted into an electric signal. And a light receiving element 18 such as a PD (photodiode).

FIG. 4 is a block diagram showing a part of the light emission / reception control circuit of the optical scanning device 1.

In the figure, reference numeral 30 denotes a timing pulse generating circuit; 32a and 32b are light projecting modules for driving the light emitting elements 8a and 8b; 34 is a light receiving module for amplifying and outputting the detection output of the light receiving element 18 described above. 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 rotary 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, as shown in FIG. 5, each of the elements 8a and 8b emits a pulse of light at a timing different from each other for each of the elements 8a and 8b (here, the phases of the elements 8a and 8b are shifted by 90 °). You.

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 always rotated at a constant speed by a motor (not shown),
As shown in FIG. 1, the light beams reflected by the rotary polygon mirror 12 and the reflecting mirrors 22a and 22b traverse the road R at a substantially right angle in a state where their scanning periods 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 have the same scanning width W in the direction crossing the road R, and are slightly overlapped with each other in the traveling direction of the road R by a distance indicated by a symbol B, but are substantially overlapped. State.

Therefore, each light beam has the same pulse emission period Δt and the time (scan period) T required to scan one scanning area Aa, Ab, even if it is the same as the conventional light beam. Since the phases of the pulsed light emission of the beams are shifted, even when the reflected light from the road surface of the road R or the moving object C such as an automobile is received by the single light receiving unit 6, the mutual interference of the reflected light beams is not affected. Can be prevented.

[0032] Moreover, the interval of the irradiation pulses of the light beam when viewed from the light receiving unit 6, the light-emitting elements 8a of the light projecting section 2 _1, 8
This is の of the pulse emission period Δt of b. That is, each light emitting element 8a of the light projecting section 2 _1, without especially shortening the pulse emission period Δt of 8b, resolution ΔW in the width direction is substantially twice that of the conventional.

Therefore, as can be seen from the above-mentioned relations (1) and (2), the rotation speed of the rotary polygon mirror 12 is set high within a range in which the resolution ΔW in the width direction with respect to the moving object C can be sufficiently ensured. If the scanning period T of the light beam is shortened, the resolution ΔL in the length direction can be simultaneously increased.

Therefore, even for a motorcycle having a small shape and a high moving speed, the shape and the like can be accurately detected.

When the reflected light of the light beam from the road surface of the road R or a moving object C such as a car is received by the light receiving element 18 and the detection output is amplified by the light receiving module 34 and taken out, The field-of-view discriminating circuit 36 identifies which of the two scanning areas Aa and Ab is the light beam in synchronization with the light emission timing pulse from the timing pulse generating circuit 30, and corresponds to each of the scanning areas Aa and 8b. Each of the detected signals is output.

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

(1) In the embodiment shown in FIGS. 6 and 7, 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 two light beams scanned while being reflected by the rotating polygon mirror 12 cross the road R as shown in FIG. The directions are set so as to substantially overlap each other.

In the embodiment shown in FIGS. 6 and 7, the structure of the optical system is simplified by the elimination of the reflecting mirrors 20a and 20b, but the precision of forming 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 FIG. 8, instead of providing the reflecting mirrors 22a and 22b as shown in FIG. 2, the common optical axis 2 of one light emitting element 8a and the light projecting lens 10a is used.
0a and a common optical axis 20b of the other light emitting element 8b and the light projecting lens 10b are arranged so as to be orthogonal to each other. Further, at the intersection of the two optical axes 20a and 20b, a beam splitter 24 is provided. 45 for each of 20a and 20b
° It is arranged in an inclined state. Moreover, the rotary polygon mirror 12 is arranged so that the rotation axis o of the rotary polygon mirror 12 is parallel to a plane including both the optical axes 20a and 20b of the light projecting unit 2.

In the optical scanning device having this configuration, each light emitting element 8
The two light beams, which are pulsed from a and 8b and become collimated by the light projecting lenses 10a and 10b, are
4 through the same one optical axis 26 and the rotating polygon mirror 1
2 is irradiated.

In this case, although the amount of light reflected and transmitted by the beam splitter 24 is slightly smaller than the amount of light emitted from each of the light emitting elements 8a and 8b, the scanning direction of each light beam is the same. At the same time, the scanning areas Aa and Ab of the respective light beams can be completely overlapped without shifting back and forth along the traveling direction of the road R.
For this reason, signal processing after light reception becomes easy, for example, the visual field discrimination circuit 36 as shown in FIG. 4 can be omitted.

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

(3) In the embodiment shown in FIG. 9, instead of providing the beam splitter 24 as shown in FIG. 8, a common optical axis 2 of one light emitting element 8a and the light projecting lens 10a is used.
0a and a common optical axis 20b of the other light emitting element 8b and the light projecting lens 10b are arranged in parallel to each other, and the rotating polygon mirror 12 can reflect both light beams passing through the respective optical axes 20a and 20b. The length q in the direction along the axis of rotation o
Is formed to be larger than the distance p between the two optical axes 20a and 20b.

In the embodiment shown in FIG. 9, although the length q along the rotation axis o of the rotary polygon mirror 12 is longer than the other embodiments, the scanning direction of the light beam in each of the scanning areas Aa and Ab is different. Are the same, and the adjustment of the optical system is easy due to the simple structure.

Other configurations and operations are the same as those of the embodiment shown in FIG. 8, and therefore detailed description is omitted.

(4) The rotary polygon mirror 12 in the embodiment shown in FIG. 10 is composed of two blocks 12a and 12b integrated with each other and having a common rotation axis o. Reflecting surface 13a along the direction,
A reflection surface 13b is formed, and the reflection surfaces 13a and 13b are formed so as to be shifted from each other by a predetermined angle in the circumferential direction.

Also in the embodiment shown in FIG. 10, the light emitting elements 8a and 8b have timings such that the phases of the light beams are different from each other in order to prevent interference of the light beams when the light is received by the light receiving section 6. Pulse emission is performed. In the case of this embodiment, the shape of the rotary polygon mirror 12 is complicated as a whole, but each light beam is scanned by a plurality of scanning areas A close to each other.
Since a and Ab are scanned in the same range W, a small moving object C can be reliably detected at a high speed without missing.

Other configurations and operations are the same as those of the embodiment shown in FIG. 9, 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. This makes it possible to further improve the resolution ΔW in the width direction.

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.

[0052]

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

(1) According to the first aspect of the present invention, it is possible to increase both the resolution in the scanning direction and the resolution in the direction perpendicular to the scanning direction without shortening the pulse emission cycle of each of the plurality of light emitting elements. Can be.

Therefore, it is possible to accurately detect the shape and the like of a moving object having a small shape and a high moving speed without deteriorating the life and stability of operation of each light emitting element.

(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 structure of the third aspect, in addition to the effect of the first aspect, the shape of the rotary polygon mirror can be made thinner and the structure of the optical scanning section can be simplified.

(4) In the configuration of the fourth aspect, in addition to the effect of the first aspect, the scanning direction and the scanning position of each light beam can be matched, and signal processing after light reception becomes easy. .

(5) In the structure of the fifth aspect, in addition to the effect of the first aspect, the scanning directions of the respective light beams can be made to coincide with each other, and since the structure is simple, adjustment of the optical system and the like are performed. Becomes easier.

(6) In the configuration of the sixth aspect, in addition to the effect of the first aspect, since the scanning directions of the respective light beams can be matched, signal processing after light reception is facilitated.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state in which an optical scanning device according to an embodiment of the present invention is installed on a road.

FIG. 2 is a perspective view illustrating details of a light projecting unit and an optical scanning unit of the optical scanning device of FIG. 1;

FIG. 3 is a front view of FIG. 2;

FIG. 4 is a block diagram illustrating a control circuit portion of the optical scanning device of FIG. 1;

FIG. 5 is a timing chart showing the timing of pulse light emission of each light emitting element constituting the optical scanning device of FIG. 1;

FIG. 6 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. 7 is a front view of FIG. 5;

FIG. 8 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. 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 perspective view illustrating details of a light projecting unit and an optical scanning unit of an optical scanning device according to another embodiment.

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 emitting part, 4 ... Optical scanning part, 6 ... Light receiving part, 8a, 8b ... Light emitting element, 10a, 10b ... Light emitting lens,
12: rotating polygon mirror, 13: reflection surface, 22a, 22b: reflection mirror (optical adjustment means).

Claims (6)

[Claims] 1. A method in which each light beam obtained by pulsating a plurality of light emitting elements is scanned by a single rotating polygon mirror, wherein each of the light emitting elements has a different timing for each element. An optical scanning device, comprising: an optical adjustment unit that adjusts a scanning area of each light beam so as to substantially overlap with each other while emitting a pulse. 2. The optical scanning device according to claim 1, wherein the optical adjustment 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 a rotating polygon mirror. An optical scanning device. 3. The optical scanning device according to claim 1, wherein the optical adjustment means is configured such that a reflection surface of the rotary polygon mirror is inclined by a predetermined angle with respect to a rotation axis. apparatus. 4. The optical scanning device according to claim 1, wherein the optical adjustment means comprises a beam splitter for multiplexing light beams from the respective light emitting elements and irradiating the multiplexed light beams to a rotating polygon mirror. apparatus. 5. The optical scanning device according to claim 1, wherein the optical adjustment unit arranges each light emitting element in parallel with the rotary polygon mirror, and the length of the rotary polygon mirror in the rotation axis direction is the outermost. An optical scanning device, wherein the optical scanning device is formed to be longer than a distance between optical axes of both light emitting elements located at ends. 6. The optical scanning device according to claim 1, wherein the optical adjustment unit is configured such that the reflecting surfaces of the rotary polygon mirror are shifted from each other by a predetermined angle along the rotation direction for each light emitting element. An optical scanning device, comprising: