JPH05297112A - Distance measuring device - Google Patents

Abstract

PURPOSE:To provide a distance measuring device, which is free of malfunction even though it is subjected to electric noise, can perform precise distance measurement over a wide measuring range, and can yield accurate measuring results with high S/N CONSTITUTION:Optical cables 2, 6 are provided each consisting of a bundle of optical fibers, and light emission elements 3a-3n are connected through the cable 2 with a photo-transmission part 1, which releases the measuring light to the outside, while light reception elements 7a-7m are connected through the cable 6 with a photo-condensation part 5 which takes in the reflected light from an object, the distance wherefrom is to be measured. Thereby the emission elements 3a-3n and reception elements 7a-7m are isolated from the photo- transmission part 1 and photo-condensation part 5, respectively, in electric terms. The optical cable 2 for photo-transmission is of such a type that the cable as bundle is divided into a plurality of photo-transmission regions so as to enable emission of the measuring light in different directions, while the optical cable 6 for photo reception is of such a type that the cable as bundle is divided in a plurality of photo-reception regions so as to enable sensing the reflected beams of light from different sides individually.

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 which emits an intensity-modulated light beam and measures a distance from a target object from a modulated signal of reflected light from the target object, and more particularly, to a distance between a preceding vehicle and a vehicle. The present invention relates to a vehicle-mounted distance measuring device for measuring a distance.

[0002]

2. Description of the Related Art Conventionally, as shown in Japanese Patent Application Laid-Open No. 3-220482, a distance measuring device is composed of an optical signal emitting section such as a laser beam and a light receiving section for reflected light from an object. There is. As shown in FIG. 11, this is because the light emitting section 31 is composed of a light emitting element such as a laser diode and a drive circuit, and emits a light beam whose light intensity is modulated. Of the light receiving element, which receives light from the light emitting section 31 reflected by the object and converts it into an electric signal. In the signal processing circuit 33, the received light modulation signal and a signal for modulating the light emitting element. The distance information is obtained by taking the phase shift between and.

Further, as shown in Japanese Patent Laid-Open No. 3-285192, there is an example in which an electric circuit is connected to a light transmitting section and a light collecting section by an optical fiber, which is shown in FIG. The optical circuit, the light-sending lens 41, and the light-receiving lens 42 are coupled by one optical fiber 43, 44, respectively, so that the device can be mechanically scanned to widen the detection range. Is.

[0004]

When it is attempted to measure the inter-vehicle distance by mounting the distance measuring device as described above on a vehicle, the measurement light is transmitted to the target object and the reflected light from the target object is transmitted. In order to reliably collect the light, it is necessary to install it on the front surface of the vehicle, and the installation place becomes a limited position such as in the hood.

However, when the device is installed in such a position, there is a lot of electrical noise, and there is a high possibility that the electric circuit for signal processing will be exposed to this noise.
In some cases, the / N ratio deteriorates and accurate measurement cannot be performed. Furthermore, noise may cause a malfunction, and the signal processing itself of the device may not be performed correctly, in which case correct distance measurement cannot be performed.

Further, since the area of the photodetector such as a photodiode used as the photodetector is small, when the optical system of the focusing system has an aberration, the reflected light from the object does not converge on the detector, In some cases, sufficient light intensity cannot be obtained, and in such a case, the S / N ratio deteriorates and accurate measurement cannot be performed.

When the optical system and the electric system are not separated as in the example of Japanese Patent Laid-Open No. 3-220482, the size of the apparatus becomes large and the installation place is restricted, so that the optimum position should be set. May not be possible.

Further, as disclosed in Japanese Patent Application Laid-Open No. 3-285192, in the one using the optical fiber, since a single light source is used, the light irradiation range is narrow and a sufficient measurement range is provided. Since it cannot be obtained, a method of mechanically scanning the device is adopted, but when performing mechanical operation, there is a problem in scanning speed. Further, since a single light source and a single light receiver are used, no consideration has been given to the detection of the reference signal for distance measurement.

The present invention has been made in view of such a situation, and an object thereof is to enable accurate distance measurement in a wide measurement range without malfunction even when exposed to electrical noise. In addition, even if there is an aberration in the condensing optical system, S / N
An object of the present invention is to provide a distance measuring device having a high ratio and capable of accurate measurement.

[0010]

In order to achieve the above object, the distance measuring apparatus of the present invention comprises an optical cable including an electric system and an optical system such as a drive circuit for receiving measurement light and a light receiving signal processing circuit. Only the optical system is placed in the light-transmitting part and the condensing part that are separated from each other and exposed to electrical noise, and the electrical system is connected to these using an optical cable and placed in the position where electrical noise is small. It was done. Further, as the optical cable, by using a bundle of a plurality of optical fibers, the light receiving area is increased, and the light receiving area is divided so that the reflected light rays from different directions are detected, and the light transmitting section is different. The measurement light beam is sent in the direction.

That is, the distance measuring apparatus of the present invention comprises a light emitting section which is composed of a light emitting element and a light emitting element driving circuit and which generates intensity modulated measuring light, and a light transmitting section which emits the measuring light to the outside and irradiates the object. A modulated signal of reflected light from the object, which includes a light-collecting section that receives reflected light from the object and a light-receiving section that includes a light-receiving element and a light-receiving element drive circuit to receive light from the light-collecting section. In the distance measuring device that measures the distance to the object from the phase shift between the modulation signal of the measurement light and the measurement signal, in order to isolate the light emitting unit from an electrical influence received from the outside, the light emitting unit and the light transmitting unit A plurality of optical fibers are bundled together by a light-transmitting optical cable, and a plurality of optical fibers are bundled between the light-collecting unit and the light-receiving unit in order to isolate the light-receiving unit from external electrical influences. Receiving It is characterized in that the coupling in use cable.

Another distance measuring apparatus according to the present invention comprises a light emitting section comprising a light emitting element and a light emitting element driving circuit for generating intensity-modulated measuring light, and a light transmitting section for emitting the measuring light to the outside and irradiating an object. And a light-receiving unit that receives reflected light from the object and a light-receiving unit that includes a light-receiving element and a light-receiving element drive circuit, and receives light from the light-collecting unit, and modulates reflected light from the object. In a distance measuring device for measuring a distance to an object from a phase shift between a signal and a modulation signal of the measuring light, the light emitting unit and the light transmitting unit are provided in order to isolate the light emitting unit from an electrical influence from the outside. Is connected with an optical fiber cable for light transmission in which a plurality of optical fibers are bundled, and the end surface of the optical fiber cable for light transmission is divided into at least two regions so that the measurement light can be irradiated in different directions. Establishment Moreover, in order to isolate the light receiving unit from an electrical influence from the outside, the light collecting unit and the light receiving unit are coupled by a light receiving optical cable in which a plurality of optical fibers are bundled, and the light is transmitted from the light transmitting unit. The end surface of the receiving optical cable on the side of the light converging portion is divided into at least two regions so that the reflected lights in different directions from the object caused by the measuring light can be detected separately. Is.

In these cases, part of the optical cable for transmitting light,
And, a part of the light receiving optical cable is used as a pair of light sending and light receiving for a reference signal detecting mechanism for distance measurement, or at least one of optical members forming a light sending unit and a light collecting unit. It can also be used for a mechanism for detecting fogging or dirt.

[0014]

In the present invention, by transmitting and receiving the light transmitting signal and the light receiving signal as light through the optical cable,
Even if the signal transmitted in the optical cable is exposed to a place where electrical noise is large, the signal transmitted in the optical cable does not interact with the electrical noise, so the transmitted and received signals are electrically It can be transmitted without being affected by noise, leads to an electrical signal processing system that considers shielding against electrical noise, and performs photoelectric conversion with a light receiving element there before processing electrical signals.
A signal with a good S / N ratio can be obtained, and accurate measurement can be performed.

Further, as the optical cable, a bundle of a plurality of optical fibers is used, and the spatial distribution of this optical fiber and the spatial arrangement of a plurality of light emitting elements and light receiving elements can be selected to solve various problems. have.

For example, even if the converged light flux has a spread due to the aberration of the condensing optical system, the incident end of the optical fiber is distributed in the expanded range and the light beam is emitted from the optical fiber at the end of the optical fiber. By converging the light on the photodetector, the detection signal can be efficiently received.

Further, by combining the divided optical fiber bundle of each area with a plurality of light emitting elements and light receiving elements, it is possible to send light in different directions and receive light from different directions, and obtain a wide measurement range. You can

Further, a part of the optical fibers may be arranged so that the signal due to the reflected light from the reference position at the time of distance measurement can be condensed, and other measured values can be corrected by this signal.

Further, since the light transmitting portion and the light condensing portion attached to the tip of the optical cable are composed only of the optical system, the sensor head portion can be made compact.
It is possible to avoid the positional restrictions when the vehicle is mounted.

[0020]

Embodiments of the distance measuring device of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of an entire system of a distance measuring device according to an embodiment of the present invention. In the figure, 1 is a light transmitting unit, 2 is an optical cable for transmitting an optical signal for transmitting light, 3a to 3n are laser diodes which are light emitting elements, 4
Is a light emitting signal processing circuit, 5 is a light collecting unit, 6 is an optical cable for transmitting a light receiving signal, 7a to 7m are photodiodes which are light receiving elements, 8 is a light receiving signal processing circuit, and 9 is a light transmitting modulation signal and a light receiving signal. It is a signal processing circuit for calculating the distance from the correlation with the modulation signal.

The operation will be described. The photodiode 3a
The light intensity-modulated light is sequentially emitted from 3n, and the emitted light is transmitted through the optical cable 2 for light transmission to the light transmission unit 1
It is emitted from the optical system for transmitting light.

The light emitted from the light transmitting section 1 is reflected from the object, enters the condensing optical system of the condensing section 5, and is guided by the lens in the condensing optical system to the end surface of the optical cable 6 for transmitting the received light signal. It converges, is transmitted through this cable 6, and is guided to the photodiodes 7a to 7m of the received light signal processing system. The signal processing circuit 9 detects a phase shift between the electric signal photoelectrically converted by the photodiodes 7a to 7m and the modulation signal for driving the light emitting elements 3a to 3n, converts the phase shift into distance data, and outputs the distance data. Is measured.

FIG. 2 shows an example of the configuration of the optical system of the light transmitting section and the condensing section. In the light transmitting section, the respective optical fiber tip portions of the optical cable 2 for guiding the light rays from the light emitting elements 3a to 3n are directed near the focal position of the light transmitting lens 10 in respective directions capable of performing distance measurement in different areas. Deploy. In the condensing unit, each optical fiber tip of the optical cable 6 is located in the vicinity of the focal position of the condensing lens 11, and the reflected light collected by the condensing lens 11 from each direction to be detected is the optical cable 6. The signal light is made incident on different positions on the optical fiber, and each signal light is guided to the photodetection elements 7a to 7m and converted into an electric signal.

Here, each optical fiber terminal and the light emitting element,
A light-collecting optical system is arranged between the light-receiving element and the light-transmitting system so that the light beam from the light-emitting element is efficiently collected on the optical fiber, and the light-receiving system collects light. It is also possible to allow the light to efficiently enter the light receiving element.

FIG. 3 shows a specific example of transmission of a light-transmitting light beam from the light-emitting element of the light-sending system to the light-sending section. When the light rays are incident on the optical fiber 2 from the laser diodes 3a to 3c, the optical systems 12a to 12c for condensing are arranged between the laser diodes 3a to 3c and the optical fiber bundles, and are emitted from the laser diodes 3a to 3c. The light rays are focused on the end face of each optical fiber bundle. A laser diode array may be used as the light sources 3a to 3c, and the measurement region may be scanned by sequentially emitting light.

As the condensing optical system for condensing the emitted light beam on the end face of the optical fiber, in addition to the lenses 12a to 12c shown in FIG. 3, a condensing optical system such as a microlens array is used. Is also possible. It is also possible to directly form the light-collecting element by processing the shape of the end of the optical fiber.

Also at the exit end of the optical fiber, the optical system 13 is arranged so that the light rays emitted from the light-transmitting lens 10 are directed in the respective directions to be measured and are also parallel rays.

FIG. 4 shows a concrete example of the transmission of the detected light beam from the light collecting portion of the light receiving system to the light receiving element. At the incident end of the optical fiber 6, the end face of the optical fiber bundle is arranged on the focal plane of the condensing lens 11 so as to correspond to each direction of condensing. At this time, an optical path conversion element such as a prism 14 is used so that the incident light beam is perpendicular to the end face of the optical fiber, or the end face of the optical fiber is tilted so as to be perpendicular to the incident light beam, and the condensed light beam is efficiently fed into the optical fiber. It arranges so that it may be guided in 6. At the emission end, the light beam emitted from the optical fiber 6 is detected by the detectors 7a to 7a.
The condensing optical system 15 is arranged so as to converge on 7c.

A light beam received through the optical fiber 6 is converged by a cone type optical fiber 16 as shown in FIG. 5, and this light is converged by a condensing optical system 17 on one light receiving element 18 and photoelectrically converted. , Can also be processed.
However, with this method, the direction of the detected light beam cannot be specified on the light receiving side, but this can be specified by the timing of the modulation of the transmitted light beam, so there is no particular problem.

Further, a point at which the distance from the device is known is selected as an appropriate point which is an intersection of the light-transmitting direction and the light-collecting direction, and is used as a reference for distance measurement. For example, reference numeral 19 in FIG.
It is also possible to dispose a reflection plate as shown in, measure the distance by the reflected light from the reflection plate 19, and correct other measured values based on the distance. Further, as a method for obtaining such a reference signal, as shown in FIG.
There is also a method in which the reflected light from the back surface of 0 is received by the light receiving optical fiber 22 arranged in pair with the light transmitting optical fiber 21. Further, as shown in FIG. 7, it is also possible to guide the light directly to the light receiving optical fiber through the optical fiber 23 and use the measured value in that case as the reference value.

FIG. 8 is a diagram showing a lens dirt detection mechanism. A dirt and fog detecting mechanism, which is a pair of a light sending optical fiber 25 and a light receiving optical fiber 26 for detecting dirt on the lens 24, is combined with the light sending section and the light collecting section. With this mechanism, the light intensity transmitted through the lens 24 is constantly measured, and when this light intensity falls below a certain value, a warning is given that the distance cannot be measured because the lens 24 is dirty or cloudy. Can be

As a lens stain detecting mechanism, there is also a method of detecting the reflected light of the lens 24, as shown in FIG. This is performed by detecting the change because the reflection characteristics change and the intensity of the reflected light changes due to clouding, dirt, etc. on the lens surface.

FIG. 10 shows an example in which the light-transmitting section and the light-collecting section are combined into one to reduce the size of the light-transmitting and light-collecting section. In this case, one lens 27 is used as a condenser lens for both transmission and reception. Light emitting elements 3a to 3c, light receiving elements 7a to 7
The optical fibers guided to c are paired, and the pairs 28a to 28c are arranged in different directions. In this example, not only downsizing but also the following advantages occur. That is, when the positions of the light transmitting unit and the light collecting unit are apart, the position where the signal can be received is limited to the vicinity of the intersection of the light emitting direction and the light collecting direction, and the light transmitting unit and the light collecting unit are separated from each other. As the position is increased, the position where the signal can be detected is limited. Therefore, if the light-transmitting unit and the light-collecting unit are coincident with each other, ideally, a signal can be condensed at an arbitrary position in the light-transmitting direction, and continuous distance information in that direction can be obtained. it can.

With the structure as in each of the above embodiments, light transmission,
Only the condensing head section is arranged at a position where the positional relationship of light transmission and condensing in the hood of the vehicle is appropriate, and the light emitting element, the light receiving element, and the electric circuit section such as the driving circuit are arranged in the sensor head. By connecting the cable to the optical fiber cable and arranging it in a position where electrical noise is sufficiently shielded and electrical noise is small, it is resistant to electrical noise, has a high S / N ratio, and provides accurate distance measurement. It becomes possible in a wide measurement range.

Although the distance measuring device of the present invention has been described above based on the embodiments, the present invention is not limited to these embodiments and various modifications can be made.

[0036]

As described in detail above, the distance measuring device of the present invention is provided with a light emitting element, a light receiving element, an actual light transmitting section, and a light condensing section when transmitting and condensing a light beam for distance detection. By connecting an optical cable between the cable and, and arranging the electric circuit part in a position where noise is small, the influence of electrical noise is reduced and accurate distance measurement is possible, as well as distance measurement in a wide measurement range. to enable.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an entire system of a distance measuring device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a configuration of an optical system of a light transmitting section and a condensing section.

FIG. 3 is a diagram showing a specific example of transmission of a transmitted light beam of a light transmission system.

FIG. 4 is a diagram showing a specific example of transmission of detected light rays in a light receiving system.

FIG. 5 is a partial configuration diagram of an example in which received light is converged by a cone-shaped optical fiber.

FIG. 6 is a partial configuration diagram of an example in which reflected light from a lens is used as a reference signal.

FIG. 7 is a partial configuration diagram of an example in which an optical fiber is directly guided to a light receiving system and used as a reference signal.

FIG. 8 is a partial configuration diagram showing a configuration of an example of a lens dirt detection mechanism.

FIG. 9 is a partial configuration diagram showing the configuration of an example of another lens stain detection mechanism.

FIG. 10 is a partial configuration diagram of an example in which one lens serves both as a light transmitting unit and a light collecting unit.

FIG. 11 is a diagram showing a general configuration of a conventional distance measuring device.

FIG. 12 is a diagram showing a configuration of a distance measuring device using a conventional optical fiber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light transmission part 2 ... Optical signal transmission optical cable 3a-3n ... Light emitting element (laser diode) 4 ... Emission signal processing circuit 5 ... Condensing part 6 ... Receiving signal transmission optical cable 7a-7m ... Light receiving element ( Photodiode 8 ... Receiving signal processing circuit 9 ... Signal processing circuit 10 ... Light transmitting lens 11 ... Condensing lens 12a-12c ... Condensing optical system 13 ... Optical system 14 ... Optical path changing element (prism) 15 ... Collection Optical optical system 16 ... Cone type optical fiber 17 ... Condensing optical system 18 ... Light receiving element 19 ... Reflector 20 ... Lens 21 ... Optical fiber for sending light 22 ... Optical fiber for receiving light 23 ... Optical fiber 24 ... Lens 25 ... Optical fiber for sending light 26 ... Optical fiber for light reception 27 ... Lens 28a to 28c ... Optical fiber pair

Claims (4)

[Claims] 1. A light emitting section which is composed of a light emitting element and a light emitting element drive circuit and generates intensity-modulated measuring light, a light transmitting section which emits the measuring light to the outside and irradiates the object, and reflected light from the object. A condensing part to be taken in and a light receiving part which is composed of a light receiving element and a light receiving element driving circuit and receives light from the condensing part, and a modulated signal of reflected light from the object and a modulated signal of the measuring light. In the distance measuring device for measuring the distance to the object from the phase shift of, a plurality of optical fibers are bundled between the light emitting unit and the light transmitting unit in order to isolate the light emitting unit from the electrical influence from the outside. In addition to coupling with a light-transmitting optical cable, in order to isolate the light-receiving unit from an electrical influence from the outside, it is possible to couple the light-collecting unit and the light-receiving unit with a light-receiving cable in which a plurality of optical fibers are bundled. Features and Distance measuring device. 2. A light emitting section comprising a light emitting element and a light emitting element drive circuit for generating intensity-modulated measuring light, a light transmitting section for emitting the measuring light to the outside and irradiating the object with reflected light from the object. A condensing part to be taken in and a light receiving part which is composed of a light receiving element and a light receiving element driving circuit and receives light from the condensing part, and a modulated signal of reflected light from the object and a modulated signal of the measuring light. In the distance measuring device for measuring the distance to the object from the phase shift of, a plurality of optical fibers are bundled between the light emitting unit and the light transmitting unit in order to isolate the light emitting unit from the electrical influence from the outside. The light-transmitting optical cable is coupled, and the light-transmitting-unit-side end surface of the light-transmitting optical cable is divided into at least two regions so that the measurement light can be emitted in different directions, and the light-receiving unit is external. Receive more In order to isolate from the electrical influence, the light collecting unit and the light receiving unit are coupled by a light receiving optical cable in which a plurality of optical fibers are bundled, and from the object generated by the measurement light emitted from the light transmitting unit. The distance measuring device is characterized in that the end surface of the receiving optical cable on the side of the light collecting portion is divided into at least two regions so that the reflected lights having different directions can be detected separately. 3. A part of the light transmitting optical cable and a part of the light receiving optical cable are used as a pair of light sending and light receiving for a reference signal detecting mechanism for distance measurement. The distance measuring device according to claim 1 or 2. 4. A detection mechanism for at least one cloud or stain of an optical member constituting a light-transmitting section and a light-collecting section by using a part of the light-transmitting optical cable and a part of the light-receiving optical cable. The distance measuring device according to claim 1 or 2, wherein the distance measuring device is used.