JPH07253460A - Distance measuring instrument - Google Patents

Abstract

PURPOSE:To easily and inexpensively detect obstacles in a plurality of directions and measure the distances to the obstacles without using a plurality of light sources nor light receiving elements by providing a transmitting/receiving optical system, light receiving section, and splitting optical element. CONSTITUTION:A light source 23 emits pulse-like laser light in response to a light source driving pulse signal S1 from a pulse generator 1 and the laser light is made incident to a transmission prism 24 after the light is transformed into a parallel luminous flux through a transmission lens 6. The prism 24 splits the luminous flux into three parallel luminous fluxes 8, 9, and 10 which are transmitted in different directions. When the luminous fluxes 8, 9, and 10 outputted from the prism 24 are reflected by obstacles, the partial reflected light rays 11-13 of the luminous fluxes 8, 9, and 10 are made incident to a reception lens 15 and respectively condensed to light receiving elements 16-18. When the element 16 is selected, the output signal S3 of the element 16 is inputted to an amplifier 20 and the amplifier 20 outputs an output signal S4 to a time lag measuring circuit 21 after amplifying the signal S3. The light source driving signal S1, output signal S4 of the amplifier 20, and a clock pulse S5 are inputted to the circuit 21 and an arithmetic circuit calculates the distances to the obstacles from time lags.

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. More specifically, the present invention relates to a distance measuring device using a laser radar, which is mainly mounted on a vehicle or a mobile robot.

[0002]

2. Description of the Related Art In recent years, safety of automobiles has become a very important factor, and various safety-related technologies have been developed. Various distance measuring devices for vehicles have been proposed as one of the important technologies relating to the safety of such vehicles. A distance measuring device for a vehicle is mounted on the front part of an automobile and emits a light beam from a laser radar to the front,
It detects an obstacle such as a car traveling in front of the own vehicle, measures the distance to the obstacle, and informs the driver.

FIG. 6 shows a conventional vehicle distance measuring device disclosed in Japanese Patent Laid-Open No. 61-259185, in which a pulse signal S1 for driving a light source from a pulse generator 1 is used.
Are transmitted to the plurality of light sources 3, 4, 5 via the pulse amplifier 2. The laser light emitted from each of the light sources 3, 4 and 5 according to the light source drive pulse signal S1 is transmitted by the transmission lens 6
And transmitted through the protective glass 7 and transmitted as output luminous fluxes 8, 9, and 10. When the output luminous fluxes 8, 9, 10 are reflected by an obstacle such as an automobile located in front, a part of the reflected luminous fluxes 11, 12, 13 are condensed by the receiving lens 15 through the protective glass 14 and received respectively. It is incident on the elements 16, 17, and 18, where it is converted into an electrical signal.

The switch 19 receives light from the light receiving elements 16 and 1 in response to a control signal S2 from a microcomputer (not shown).
Any one of the electric signals output from 7 and 18 is selected, and the selected electric signal S3 is input to the amplifier 20. The amplifier output signal S4 amplified by the amplifier 20 is input to the time difference measuring circuit 21. The time difference measuring circuit 21 includes a light source drive signal S1 and a clock pulse S5 from the clock generator 22.
Is input, the presence or absence of an obstacle is detected, and the round trip time to the obstacle is measured from the difference between the light transmission timing and the light reception timing to obtain the distance to the obstacle. In this way, the plurality of light sources 3, 4, 5 and the plurality of light receiving elements 16, 1
By using 7, 18, it is possible to detect not only the front of the front of the vehicle but also the obstacles on the left and right of the front.

On the other hand, such a distance measuring device for a vehicle is required to be installed in a place where it is not affected by noise from the outside because the device is required to have high reliability.
Therefore, in order to avoid the influence of electrical noise generated from the ignition system in the engine room, the distance measuring device is separated from the optical system and the electrical system, and only this optical system is installed near the engine room. It has been practiced to install it in a passenger compartment with a small number of vehicles, and to connect between them with an optical fiber.

[0006]

However, in the above-mentioned conventional distance measuring device, since a plurality of expensive semiconductor lasers are used as the light source and the light-receiving elements are also used in the same number as the light source, the whole device is used. However, there is a problem that the price becomes extremely high.

Further, in order to avoid the influence of electric noise, when the distance measuring device is divided into an electric system and an optical system by an optical fiber, the optical fiber is necessary for the total number of light sources and light receiving elements. , Which also contributed to the price increase.

Therefore, the present invention has been made in view of the above situation.
It is easy and inexpensive to detect obstacles in multiple directions and measure distances without using multiple light sources or multiple light-receiving elements, and at the same time, install the optical system and electrical system separately. An object of the present invention is to provide a distance measuring device capable of performing the above.

[0009]

According to a first aspect of the present invention, a light source, a transmission optical system that radiates a light beam from the light source toward an obstacle, and a light beam reflected by the obstacle are collected. A receiving optical system that emits light and a light receiving unit that receives the condensed light flux and generates a reception signal are provided, and the presence or absence of the obstacle is detected based on the reception signal, and the emission of the light flux causes In a distance measuring device that measures the time interval until the reception of reflected light to measure the distance to the obstacle, the light fluxes that are arranged in front of the transmission optical system and are transmitted through the transmission optical system are in different directions. It is characterized in that it is provided with a splitting optical element for splitting into a plurality of light fluxes directed toward.

In this structure, the following structure is preferable. That is, the distance measuring device is mounted on the front part of the vehicle,
It is preferable to further include an optical fiber arranged between the light source and the transmission optical system so as to guide the light flux from the light source to the transmission optical system. Further, the split optical element is a protective cover having a plurality of prism surfaces for splitting the light flux into the plurality of light fluxes, and the protective cover scatters contaminants that may scatter from the front of the vehicle and adhere to the transmission optical system. It is preferable to shut off. Further, it is preferable that the split optical element is composed of a plurality of reflecting mirrors having different reflection directions. Further, a composite optical element that is disposed in front of the receiving optical system and converts the plurality of reflected light beams traveling from the plurality of different directions toward the receiving optical system into substantially parallel light beams and makes them incident on the receiving optical system. It is preferable to further include

According to a sixth aspect of the present invention, a light source, a transmission optical system that radiates a light beam from the light source toward an obstacle, and a reception optical system that condenses the light beam reflected by the obstacle. A light receiving unit that receives the condensed light flux and generates a reception signal, detects the presence or absence of the obstacle based on the reception signal, and from the emission of the light flux to the reception of the reflected light flux. In a distance measuring device that measures a time interval to measure a distance to the obstacle, a plurality of the reflected light fluxes that are arranged in front of the receiving optical system and head toward the receiving optical system from a plurality of mutually different directions are provided. It is characterized by comprising a synthesizing optical element which converts the light into a substantially parallel light beam and makes it enter the receiving optical system.

In this structure, the following structure is preferable. That is, the distance measuring device is mounted on the front part of the vehicle,
It is preferable to further include an optical fiber arranged between the receiving optical system and the light receiving unit so as to guide the light flux from the receiving optical system to the light receiving unit. It is preferable that the synthetic optical element is a protective cover for the transmission optical system having a plurality of prism surfaces, and the protective cover blocks contaminants that may adhere to the transmission optical system. Further, it is preferable that the synthetic optical element is composed of a plurality of reflecting mirrors having different reflecting directions.

[0013]

In the invention described in claim 1, the luminous flux emitted from the light source is divided into different directions by the dividing optical element after passing through the transmitting optical system. The light beam reflected by the obstacle is condensed by the receiving optical system and enters the light receiving unit. Thus, even with a single light source, the light flux can be emitted in a plurality of directions, and a wide range of obstacles can be detected. In the invention described in claim 6, the luminous flux from the light source is radiated toward the obstacle by the transmission optical system. A light beam reflected from a certain obstacle enters the combining optical element from a certain direction, and a light beam reflected from another obstacle enters the combining optical element from another direction. These reflected light beams are converted into light beams that are substantially parallel to each other by the combining optical element and enter the receiving optical system. In this way, the reflected light beams from a plurality of directions are converted into parallel light beams by the combining optical element and enter the receiving optical system, so that the reflected light beams from a plurality of directions can be received by the single light receiving element. .

[0014]

FIG. 1 shows a distance measuring device for an automobile, which is an embodiment of the present invention. A pulse generator 1 supplies a pulse signal S1 for driving a light source through a pulse amplifier 2 to a light source 23 and It is sent to the time difference measuring circuit 21. This light source 23
Emits pulsed laser light according to the light source driving pulse signal S1. The light source 23 is arranged at the focal position of the transmission lens 6, and the transmission lens 6 converts the laser light from the light source 23 into a parallel light flux.

In front of the transmitting lens 6, there is arranged a transmitting prism 24 which constitutes a splitting optical element, and the transmitting prism 24 transforms the parallel luminous flux from the transmitting lens 6 into luminous fluxes 8, 9 and 10 in three different directions. To divide. Transmission prism 24
More specifically, the front surface 24a facing the transmission lens 6 is a single plane, and the back surface 24b is three flat surfaces 24.
It is formed of c, 24d, and 24e. This plane 24
d is parallel to the surface 24a, so that the light beam 9 passing through the plane 24d goes straight in parallel to the optical axis of the transmitting lens 6.
The remaining planes 24c and 24e are inclined with respect to the plane 24d, and this inclination refracts the light beams 8 and 10 away from the optical axis of the transmission lens 6. In addition,
The transmission prism 24 has a function as a protective cover for the transmission lens 6 in addition to the above-described light beam splitting function, and blocks contaminants scattered from the front of the vehicle toward the transmission lens 6.

Behind the protective glass 14 is a receiving lens 15
The receiving lens 15 receives the reflected light fluxes 11, 12, and 13 reflected from the obstacle by the light receiving elements 16, 17, and 1.
Focus on 8. The light receiving elements 16, 17, and 18 are reflected light beams 1
1, 12, 13 are photoelectrically converted to output a signal S3. The number of these light receiving elements 16, 17, 18 is the same as that of the transmission prism 24.
The number of divided light fluxes, that is, three in this embodiment.
The switch 19 is a switch that selects one of the light receiving elements 16, 17, and 18 by a control signal S2 from a microcomputer (not shown).

The amplifier 20 receives the signal S3 and outputs the amplifier output signal S4, and the oscillator 22 outputs the clock pulse S5.
Is output. The time difference measuring circuit 21 receives the light source drive signal S1, the amplifier output signal S4 and the clock pulse S5, and measures the time difference between the light source drive signal S1 and the amplifier output signal S4.

Next, the operation will be described. In response to the light source driving pulse signal S1 from the pulse generator 1, the light source 23
Emits pulsed laser light, which is converted into a parallel light flux by the transmission lens 6 and enters the transmission prism 24. The transmission prism 24 divides this parallel light flux into three parallel light fluxes 8, 9 and 10 having mutually different transmission directions. When these output lights 8, 9 and 10 are reflected by an obstacle, some of the reflected lights 11, 12 and 13 are reflected by the protective glass 1.
The light is incident on the receiving lens 15 through the light receiving element 16, 1
It is focused on 7 and 18, respectively.

The switch 19 receives light from the light receiving elements 16 and 1 in response to a control signal S2 from a microcomputer (not shown).
Select either 7 or 18. When the light receiving element 16 is selected, the signal S3 output from the light receiving element 16 is input to the amplifier 20, and the amplifier output signal S4 is output from the amplifier 20. When any of the other light receiving elements 17 and 18 is selected, the signal S3 output from the light receiving elements 17 and 18 is input to the amplifier 20. The amplifier 20 amplifies the signal S3 and outputs the amplifier output signal S4 to the time difference measuring circuit 21. The light source drive signal S1, the amplifier output signal S4, and the clock pulse S5 are input to the time difference measurement circuit 21, and the number of pulses between the rising edges of the light source drive signal S1 and the amplifier output signal S4 is counted to input between both signals. The time difference is obtained, and the distance measuring value is calculated from the time difference by the arithmetic circuit. The obtained distance measurement value is displayed on the display unit (not shown) for each reception direction switched by the switch 19.
When no obstacle is detected, it is displayed that no obstacle is detected.

In the present embodiment, the transmission prism 24 splits the light beam incident on itself into three light beams, but the number of divisions can be arbitrarily selected. Also, the individual surfaces 24c, 24
A direction in which the apex angles of d and 14e, the boundary between them, and the position of the light source are appropriately set, a detection angle range is set that suits the purpose of use of the distance measuring device, the state of use, etc. In addition, the intensity of light can be appropriately distributed to each light flux by, for example, setting the area of the split surface to be relatively small to reduce the amount of light to be distributed. In the present embodiment, the plurality of prisms forming the transmission prism 24 have parallel ridges at the respective apex angles, and a plurality of output lights are transmitted on one plane, but the ridges at the respective apex angles are parallel. When eliminated, multiple output lights can be transmitted rather than in one plane.

Next, a second embodiment of the present invention will be described with reference to FIG.
Will be described. In the second embodiment, the receiving lens 15
Except that the receiving prism 34 is used as a protective cover for the vehicle and a single light receiving element 35 is used accordingly.
It is the same as the distance measuring device shown in FIG.

Receiving prism 34 constituting a synthetic optical element
Is arranged in front of the receiving lens 15, and the receiving prism 34 has the same shape as the transmitting prism 24 of the first embodiment. That is, the first face of the receiving prism 34 facing the obstacle
The surface 34a is formed by three planes of the surface 34c, the surface 34d, and the surface 34e, and the second surface 34b is formed by one plane. The inclination angles formed by the first surface 34a and the surfaces 34c, 34d, and 34e, that is, the apex angles of the prisms are different from each other, and the receiving prism 34 is composed of three prisms having different apex angles. It was done. The number of the plurality of surfaces 34c, 34d, and 34e of the receiving prism 34 is 3, which corresponds to the number of light sources 3, 4, and 5 forming the semiconductor laser array. The receiving prism 34 having such a shape reflects the reflected light beams 31 from the obstacles which are incident at different angles.
32 and 33 are converted into a light beam parallel to the optical axis of the receiving lens 15.

Next, the operation will be described. The pulse train output from the pulse generator 1 serves as a lighting trigger, and the light source drive signal S1 is output to the switch 19 and the time difference measuring circuit 21. When the switch 19 selects the light source 3 by the control signal S2 from the microcomputer (not shown), the laser light is emitted from the light source 3 and the output light 8 is transmitted from the transmission lens 6 through the protective glass 7. There is an obstacle in the transmission direction of the output light 8, and when it is reflected, part of it is incident on the reception prism 34 as reflected light 31. The reflected light 31 has a surface 34
The light is deflected according to the apex angle formed by c and the surface 34b, enters the receiving lens 15, and is condensed on the light receiving element 35. A signal S3 is output from the light receiving element 35, the presence or absence of an obstacle in the receiving direction is detected based on the signal S3, and the distance is measured.

Similarly, when the other light sources 4 and 5 are selected by the switch 19, the output lights 9 and 10 are respectively transmitted, and the reflected lights 32 and 33 are respectively received from the corresponding receiving directions to determine whether or not there is an obstacle. Is detected and the distance is measured. In this way, the presence or absence of an obstacle is detected for each transmission direction of each light source 3, 4, 5, and the distance to the obstacle is measured,
It is displayed on the display unit (not shown).

In the transmitting prism 24 and the receiving prism 34 of the above-mentioned first and second embodiments, the surfaces on the transmitting lens 6 and the receiving lens 15 sides are a single plane, and the surfaces on the opposite side are inclined surfaces, that is, prisms. Although the surface was formed, it can be reversed. That is, it is possible to form a plurality of inclined surfaces on the surfaces of the transmitting lens and the receiving lens so that the surface on the obstacle side is a single plane. Furthermore, a plurality of inclined surfaces can be formed on both surfaces. Since the transmission prism 24 and the reception prism 34 also have a function as protective covers for the transmission lens 6 and the reception lens 15, respectively, as described above, foreign matter such as sand and oil adheres to the transmission prism 24 and the reception prism 34. Considering the cleaning of the transmitting prism 24 and the receiving prism 34 at the time of cleaning, if the obstacle side is a single plane, the cleaning becomes easy.

Further, a third embodiment will be described with reference to FIG. In the third embodiment, the transmitting lens 6 and the receiving lens 15 are respectively provided with a transmitting prism 24 and a receiving prism 3.
4 is an example in which 4 is arranged. Therefore, in this example, the light source 23
The light receiving element 35 and the light receiving element 35 can be single.

Further, a fourth embodiment will be described with reference to FIG. The light emitting surface of the light source 23 has an end face 3 of the optical fiber 37.
7a are arranged to face each other, and the other end face 3 of the optical fiber 37
The position of 7b is arranged at the focus position of the transmission lens 6. The laser light emitted from the light source 23 is supplied to the optical fiber 37.
Is incident on the end face 37a of the optical fiber 37, and the other end face 37 of the optical fiber 37
Emit from b. The laser light emitted from the end face 37b passes through the transmission lens 6 and the output light 8 from the transmission prism 24,
Emit as 9 and 10. The output light 8, 9, 10 receives the light 11, 12, 13 reflected from the obstacle, detects the obstacle, and obtains the distance to the obstacle.

According to this embodiment, one optical fiber 37
Using only the above, for example, an electric system (not shown) including the light source 23 and various circuits can be installed in the vehicle compartment, and the transmission lens 6 and the transmission prism 24 can be mounted near the engine room. Although the optical fiber is provided only on the transmitting optical system side in the embodiment of FIG. 4, when the optical fiber can be arranged on the receiving optical system side with a similar configuration, the light from the receiving optical system is received by the light receiving element and the light receiving lens. An optical fiber can be placed between them to increase the distance between them.

Further, a fifth embodiment will be described with reference to FIG. A transmission mirror 41 is arranged in front of the transmission lens 6, and the transmission mirror 41 is formed by three mirror surfaces 41a, 41b, 41c inclined with respect to each other, and the mirror surfaces 41a, 41b, 41c are mutually arranged at a predetermined angle. Crosses each other and reflects incident light in different directions. A reception mirror 42 is arranged in front of the reception lens 15, and the reception mirror 42 is a plane mirror having a single sheet structure.

Next, the operation will be described. The laser light emitted from the light source 23 is converged by the transmission lens 6 and is incident on the transmission mirror 41 as a parallel light beam.
From the surfaces 41a, 41b, 41c of the light beams, the light beams 8 are emitted as output light beams 8, 9, 10 of three light beams having different transmission directions.
The output lights 8, 9, 10 are projected on an obstacle, and the reflected lights 11, 12, 13 reflected by the obstacles enter the receiving mirror 42 from different receiving directions, and are reflected by the receiving mirror 42 in different directions. The light is collected on the light receiving elements 16, 17, and 18 via the receiving lens 15, respectively.

Incidentally, the receiving mirror 42 of the fifth embodiment.
Can also be configured to have a plurality of mirror surfaces like the transmission mirror 41, and thus a single light receiving element can be provided as in the third embodiment.

In each embodiment, the surface forming the prism or mirror is not limited to a flat surface, but may be a curved surface having a converging or diverging function. In this case, the transmission optical system and the splitting optical element can be combined into one element, or the reception optical system and the combining optical element can be combined into one element. is there.

Further, although the above-described embodiment is a distance measuring device for mounting on an automobile, the present invention is not limited to this, and can be mounted on a railway vehicle, a transfer robot or the like.

[0034]

According to the invention described in claim 1 of the present invention, the luminous fluxes arranged in front of the transmitting optical system and passing through the transmitting optical system are divided into plural luminous fluxes heading in different directions. Since it has a dividing optical element for dividing, it is possible to detect obstacles existing in a plurality of directions and measure distances without using a plurality of light sources, which greatly simplifies the configuration of the device and reduces cost. It can be reduced.
According to the invention described in claim 6 of the present invention, the plurality of reflected light beams which are arranged in front of the reception optical system and which are directed to the reception optical system from a plurality of different directions are converted into substantially parallel light beams. Since it has a composite optical element which is made incident on the receiving optical system, it is possible to detect an obstacle existing in a plurality of directions and measure a distance without using a plurality of light receiving elements. Very easy,
The cost can be reduced. Therefore, if both are combined and the split optical elements are provided in both the transmission optical system and the reception optical system, the configuration can be further simplified and the cost can be reduced. At the same time, since light transmission between the light source and the transmission optical system or between the reception optical system and the light receiving element is possible with a small number of optical fibers, the light source and the transmission optical system or the reception optical system and the light receiving element It is possible to easily prevent the performance from being deteriorated by noise by setting a long distance between the two.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of another embodiment of the present invention.

FIG. 3 is a block configuration diagram of a third embodiment of the present invention.

FIG. 4 is a block configuration diagram of a fourth embodiment of the present invention.

FIG. 5 is a block configuration diagram of a fifth embodiment of the present invention.

FIG. 6 is a block diagram of a conventional example.

[Explanation of Codes] 1 ... Pulse generator 2 ... Pulse amplifier 3, 4, 5, 23 ... Light source 6 ... Transmitting lens 7, 14 ... Protective glass 8, 9, 10 ... Output light 11, 12, 13, 31, 32, 33 ... Reflected light 15 ... Receiving lens 16, 17, 18, 35 ... Light receiving element 20 ...・ Amplifier 21 ・ ・ ・ ・ Time difference measuring circuit 22 ・ ・ ・ ・ ・ ・ Clock generator 4 24 ・ ・ ・ ・ Transmission prism 34 ・ ・ ・ ・ Reception prism 37 ・ ・ ・ ・ ・ ・ Optical fiber 41 ・ ・ ・ ・ ・ ・ Transmission mirror

Claims (9)

[Claims] 1. A light source, a transmission optical system that radiates a light beam from the light source toward an obstacle, a reception optical system that collects the light beam reflected by the obstacle, and the collected light beam. A light-receiving unit that receives light and generates a received signal, detects the presence or absence of the obstacle based on the received signal, and measures the time interval from the emission of the light flux to the reception of the reflected light to cause the obstacle. A distance measuring device for measuring a distance to an object, comprising a splitting optical element which is arranged in front of the transmission optical system and splits the light flux passing through the transmission optical system into a plurality of light fluxes traveling in mutually different directions. A distance measuring device characterized by the above. 2. The distance measuring device is mounted on a front portion of a vehicle, and further comprises an optical fiber arranged between the light source and the transmission optical system so as to guide a light beam from the light source to the transmission optical system. The distance measuring device according to claim 1, further comprising: 3. The split optical element is a protective cover having a plurality of prism surfaces for splitting the light flux into the plurality of light fluxes, and the protection cover can be scattered from the front of the vehicle and attached to the transmission optical system. The distance measuring device according to claim 1 or 2, which blocks contaminants. 4. The distance measuring device according to claim 1, wherein the split optical element is composed of a plurality of reflecting mirrors having different reflection directions. 5. A plurality of reflected light beams, which are arranged in front of the receiving optical system and travel from a plurality of different directions toward the receiving optical system, are converted into substantially parallel light beams and are incident on the receiving optical system. The distance measuring device according to claim 1, further comprising a combining optical element. 6. A light source, a transmission optical system that radiates a light beam from the light source toward an obstacle, a reception optical system that collects the light beam reflected by the obstacle, and the collected light beam. A light receiving unit that receives light and generates a received signal, detects the presence or absence of the obstacle based on the received signal, and measures the time interval from the emission of the light beam to the reception of the reflected light beam to prevent the obstacle. In a distance measuring device that measures the distance to an object, the plurality of reflected light beams that are arranged in front of the reception optical system and that travel toward the reception optical system from a plurality of different directions are converted into substantially parallel light beams. A distance measuring device comprising a combining optical element which is incident on the receiving optical system. 7. An optical fiber mounted on the front of a vehicle, wherein the distance measuring device is arranged between the receiving optical system and the light receiving unit so as to guide a light beam from the receiving optical system to the light receiving unit. The distance measuring device according to claim 6, further comprising: 8. The synthetic optical element is a protective cover for the receiving optical system having a plurality of prism surfaces, and the protective cover blocks contaminants that may adhere to the transmitting optical system. Item 6. The distance measuring device according to item 6. 9. The distance measuring device according to claim 6, wherein the synthetic optical element is composed of a plurality of reflecting mirrors having different reflecting directions.