Classifications

• • G—PHYSICS
  • G08—SIGNALLING
  • G08G—TRAFFIC CONTROL SYSTEMS
  • G08G1/00—Traffic control systems for road vehicles
  • G08G1/01—Detecting movement of traffic to be counted or controlled
  • G08G1/04—Detecting movement of traffic to be counted or controlled using optical or ultrasonic detectors
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
  • G01S17/88—Lidar systems specially adapted for specific applications
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
  • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
  • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
  • G01S7/481—Constructional features, e.g. arrangements of optical elements
  • G01S7/4811—Constructional features, e.g. arrangements of optical elements common to transmitter and receiver

Definitions

• the present invention relates to a method for surveying traffic conditions, defined in the introdu ⁇ to- ry section of the first patent claim concerning method.
• the invention also relates to an apparatus for surveying traffic conditions, according to the first patent claim concerning apparatus.
• the object of the present invention is to introduce a new method and apparatus for surveying traffic conditions, whereby road traffic and for instan ⁇ ce road surface conditions can be surveyed better than before.
• the first method claim is referred to, and as for the characteristic novel featu ⁇ res of the apparatus of the invention, the first appara ⁇ tus claim is referred to.
• the method can be applied without breaking the road surface or the driveway at all.
• the apparatus is installed above the road surface, at a sufficient dis- tance from the road surface, and all observations are made by means of optical radiation. By employing this method and apparatus, the length and height and, if necessary, the speed of all vehicles moving on the road can be measured, as well as the condition of the road surface.
• a number of linear beams there is formed a number of linear beams, and these are arranged lengthwise side by side and transversally in a fan-shaped position, and they are directed, at certain intervals from each other, towards the road surface so that they cover an area of surveillance of a desired width on the road surface.
• the whole area of ⁇ ur- veillance is scanned successively in a serial fashion.
• the measuring of the radiation entering the detec ⁇ tor is carried out reliably, and the adjacent beams do not affect each other.
• the data processing is simplified, too.
• the condition of the road surface can be sur ⁇ veyed or evaluated.
• the road surface reflects radiation in a different way, and on the basis of this reflection, the state of the road surface can be evaluated, and if necessary, travellers can be for example warned of dangerous road conditions.
• the patent claim 9 introduces a preferred embodiment of the invention, which apparatus is provided with a separate source of radiation, by means of which, together with the detector, particularly the presence of fog in the vicinity of the road surface can be detec- ted.
• the patent claim 10 introduces an advantageous apparatus for realizing the method of claim 5.
• figure la is a schematical illustration of an apparatus according to the present invention
• figure lb is a top-view illustration of the road surface, seen from the point of view of the detector of the apparatus
• figure lc is an illustration of an enlarged detail of the apparatus
• figure 2 is an illustration of another preferred embodiment of the invention
• figure 3 illustrates the principles of the transmitter
• figure 4 is a block diagram of the construction of the apparatus.
• the apparatus of the invention comprises a transmitter unit l and a detector unit 2, which are located at a distance di from each other.
• the transmitter unit l is provided with a infrared or IR radiation source 3, advantageously an IR-LED or IR semiconductor laser, and a cylinder lense 4.
• IR radiation source 3 advantageously an IR-LED or IR semiconductor laser
• cylinder lense 4 By means of the cylinder lense 4, the radiation sent by the radiation source 3 is formed into a linear beam 5.
• the linear beam 5 is on one side a strongly oblate ellipse, as is apparent from figure lb.
• the linear beam 5 is directed towards the roadway, so that the longitudinal axis 5a of its cross-section is advantageously converged, at least roughly, to the lengthwise direction B-B of the road, and is positioned at a predetermined oblique angle ⁇ with respect to the perpendicular N of the roadway.
• the detector unit 2 comprises an objective 6 and a detector 7.
• the detector 7 is a CCD line detector, or a position-sensitive photodiode.
• the visual field 20a of the objective is a conical area in front of the detector unit, which area falls within the scope of the detector either wholly or as a suitably limited section 20 in figure lb.
• the location of the image 5b, 5c of the beam 5 depends on the distance of the surface under surveillance, such as the vehicle A or the road surface T, from the objective 6.
• the vehicle A can be detected as a shift of the beam image on the surface of the detector.
• a suitable data processing unit 8 such as a microprocessor, the necessary computa- tions are carried out, the principles whereof are set forth in the following.
• the location of the center 5d of the beam 5 on the detector 7, as a function of the distance s bet ⁇ ween the surface Al of the vehicle A and the objective 6, is illustrated in figure la.
• the beam 5 and its optical axis la. are at an oblique angle ⁇ with respect to the perpendicular N of the roadway.
• the optical axis Io also is perpendicular to the roadway surface.
• the focal distance of the objective lense 6 is f.
• the center 5d of the beam 5 on the road surface T is located at a distance h from the normal N of the roadway, figured at the point of the transmitter unit.
• the center 5d' of the beam 5 on the surface Al of the vehicle A in turn is placed at the distance h a from the said normal N.
• the image of the beam center falling on the road surface, received on the detector, is lo ⁇ cated at the distance ha.' from the optical axis Io of the detector, and the image of the beam center falling on the surface Al of the vehicle A, received on the detector, is at the distance h a ' from the optical axis Io of the detector, as is apparent from figure lc.
• the transmitter unit 1 and the detector unit 2 are placed at the distance s x above the road surface T.
• the obtained location of the center 5d' falling on the surface Al of the vehicle A on the detector is:
• Formulas 1, 2 and 3 presuppose that Si » f and s a » f, i.e., when the focal distance f of the objective 6 is remarkably smaller than the distance s a of the vehicle A or the road surface T from the objective 6, the change of the location of the beam image on the detector only depends on the distance s a of the vehicle A from the objective 6.
• the location of the center 5d of the beam 5 on the detector 7 is comparable to the height Al of the vehicle A. It is clear that other heightwise changes in the road surface can also be detected. If for instance it is wintertime and the road surface is covered with snow, and the position of the beam on the detector has shif- ted for a relatively long time from the location corresponding to the road surface, it is obvious that a snowdrift has accumulated on the road.
• the state of the road surface can also be surveyed and observed by means of the apparatus desc ⁇ ribed above. The intensity of the radiation scattered or reflected from the road surface depends on the cha- racteristics of the road surface.
• the road surface condition for example to four classes: 1) the road surface is dry; 2) the road surface is wet; 3) the road surface is covered with ice or with black ice; and 4) the road surface is covered with snow. This is realized by comparing the intensity of the transmitted beam 5 and the intensity of the radiation scattered from the road surface, and the state of the road is evaluated on the basis of this.
• the linear beam is directed towards the road surface so that the longitudinal axis 5a of its cross-section is parallel to the lengthwise direction of the road, and generally to the direction of the vehicle transport. It is, however, possible to install the apparatus above the road, so that the longitudinal axis 5a is at an oblique angle with respect to the lengthwise direction of the road. This, however, somewhat decreases the sensitivity of the measurement.
• a preferred embodiment of the apparatus of the present invention is illustrated in figure 2.
• the transmitter unit 1 and the detector unit 2 of the apparatus, as well as the connected data processing unit 8, are attached to a suitable support 9 at a desired distance Sa. above the road surface T.
• the transmitter unit 1 and the detector unit 2 are located at the distance dt from each other, the said distance being advantageously 0,5-1,0 .
• the transmitter unit 1 and the detector unit 2 are installed to the support 9 so that their optical axes I and I ⁇ are at right angles to the road surface T.
• the principle of the transmitter unit 1 of the apparatus of figure 2 is illustrated as enlarged in figure 3.
• the transmitter unit l comprises a number of infrared transmitters 10, their number in this particular embodiment being 10.
• the infrared or IR transmitters 10 are formed of IR radiation sources 3, such as IR-LEDs, and of cylinder lenses 4, which are arranged in the housing 11 of the transmitter unit.
• the IR transmitters 10 are placed in the housing 11 of the transmitter unit so that they are located on a circle orbit 11a at a given distance from each other.
• the IR transmitters 10 are also arranged so that the optical axes Ilo , In , ... , Ia.» of their beams 50, 51, 52, ..., 59 intersect the circle orbit 11a at the center O, symmetrically with respect to the center axis, i.e. the optical axis Ii of the transmitter unit 1.
• the beam 50, 51, 52, ..., 59 received from each IR transmitter 10 is linear.
• the spread angle ⁇ of the beam is advantageously of the size 2-4" with respect to the transversal direction of the cylinder lense 4.
• the spread angle corresponds to the spread angle of the IR radiation source, or is somewhat limited therefrom. It can be within the range of 10-25°.
• the housing 11 of the transmitter unit is placed within a protecting shield 12.
• the front plate 12a of the protecting shield 12 is adjusted to such a distance from the IR transmitters 10 that the optical axes of the beams intersect each other, i.e. in the vicinity of the center 0 of the circle orbit 11a.
• a slot or an aperture 13 In the front plate 12a, at the said center O, there is arranged a slot or an aperture 13, wherethrough the beams proceed out of the transmitter unit 1.
• the aperture 13 can be provided with a filter or a protecting glass, whereby a certain radiation frequency range is excluded outside the beams, or in general the intrusion of for instance dust to inside the protecting shield is prevented.
• the beams 50, 51, 52, ..., 59 are directed, in a fan-shaped formation, towards the road surface T, as is illustrated in figure 2. Thus they cover a desired area D of surveillance in the transversal direction of the road.
• the beams 50, 51, 52, ..., 59 meet the road surface at given distances from each other, these distances being within the range of 1-2 m, and symmetrically on both sides of the optical axis la. of the transmitter unit 1.
• the detector unit 2 is formed of a CCD line camera comprising an objective 6 and a CCD line detec ⁇ tor 7. Instead of the said detector, there can be used some other suitable monodimensional detector which is sensitive to the employed radiation.
• the detector unit 2 also includes a data processing unit 8, such as a microprocessor.
• a filter 14 In connection with the objective 6 of the detector unit 2, there is advantageously also provided a filter 14, whereby the amount of diffused light entering the detector is diminished, and in this case visible light is prevented from entering the detector.
• the visual field 20 of the detector 2 is adjusted so that it covers the area D of surveillance.
• the linearly successive detector elements 7a of the detec ⁇ tor 7 are read, and the intensity and distribution of the received radiation in the lengthwise direction of the linear detector is registered.
• the measuring information is recorded in the memory 16 of the data processing unit 8 (cf. figure 5) .
• the operation of the transmitter unit 1 is also controlled by means of the data processing unit 8.
• Each IR transmitter 10 of the transmitter unit 1 is connected to the switching unit 15.
• the switching unit 15 comprises a number of switches, advantageously electronic switches, by intermediation of which each IR-LED is connectable to the power source U.
• the data processing unit 8 is connected to the switching unit 15 so that by means thereof, any one of the IR-LEDs 3 can be chosen to operate by manipulating the correspond- ing switch in the switching unit 15.
• the apparatus of the invention is operated as follows.
• the IR transmitters 10 of the transmitter unit 1 are made to operate one at a time.
• one of the beams 50, 51, 52, ..., 59 at a time is directed from the transmitter unit 1 towards the road surface T.
• the location of the beam 50 which is nor ⁇ mally hi on the road surface, has shifted towards the optical axis Ix of the transmitter unit 1, and is lo ⁇ cated at the distance h aa . or h aa therefrom.
• the area D of surveillance is covered one beam 50, 51, 52, ..., 59 at a time, and the location of the beam on the road, or on the surface of the vehicle moving in the area of surveillance, is defined by means of the detector unit 2 and recorded in the memory 16 of the data processing unit 8.
• the locations of all beams in the area D of surveillance are defined and recorded in the memory 16, they are compared to the locations of the beams on the surface of the road T as previously recorded in the memory. Any deviations from the previous locations on the road surface, i.e. h - h a ⁇ or hi - h aa respectively, mean that a vehicle or the like appears at the location of the said beam.
• the height of the vehicle at this particular beam can be defined. Because the direction and location of each beam with respect to the optical axis I ⁇ of the detector unit 2 is known, the width and location of the vehicle on the roadway can be defined, when the changes in the posi ⁇ tions of the beams, with respect to the positions cor ⁇ responding to the road surface, are known on the detec- tor 7.
• the condition of the road surface is surveyed, by means of the above described apparatus, in the following manner.
• the intensities of the beams transmitted in successive pulses by the IR transmitters 10 of the transmitter unit 1 are adjusted on the basis of the reflectory capacities of the road surface T, so that the signal of scattered radiation obtained in the detector unit is maintained sufficiently strong in order to be clearly perceived.
• the data processing unit 8 it is possible for example to adjust the power fed to the IR transmitters 10 via the switching unit 15 by using a separate adjusting unit 17. These preset adjustments are recorded for example in the memory 16 of the data processing unit 8.
• the beams 50, 51, 52, ..., 59 directed from the transmitter unit 1 towards the road surface T meet the road surface at .
• At least two apparatuses of the present invention can be arranged in connection with a road, parallel to the road and at desired distances from each other.
• the data processing units 8 of these devices can be connected to each other. By employing two separate devices, the velocity and direction of the vehicles is found out. By means of the data processing units 8, it is possible to examine whether a vehicle appears near either one of the devices. When a vehicle is detected at one of the apparatuses, the data pro ⁇ ess- ing unit 8 measures the time that passes between this moment and the moment when the second apparatus detects the same vehicle. The direction of the vehicle is inferred according to which apparatus first detects it. This kind of apparatus can be used for surveillance and computation of traffic in both directions, as well as for speed control.
• the transmitter unit 1 of the apparatus can be provided with an extra IR transmitter 10a, comprising an IR radiation source 3a, advantageously an IR-LED or an IR semiconductor laser, and a lense 4a, advantageous ⁇ ly a cylinder lense as is apparent from figure 3.
• the optical axis lax of this IR radiation source 3a advan ⁇ tageously forms an angle ⁇ of about 30° or larger with the optical axis I of the detector unit 2 (cf. figure 2) .
• the beam 60 of the radiation source 3a traverses the visual field 20 of the detector unit 2, and in case of fog the radiation beam 60 scatters radia ⁇ tion which is detected by the detector unit 2.
• the IR radiation source 3a is employed in the same fashion as the other radiation sources 3 of the transmitter unit 1 7 and in structure it can be completely similar to them.
• the rest of the IR transmitters 10 of the transmitter unit 1 can also be employed, as well as the beams 50, 51, 52, ..., 59 formed by them.
• the distribution of the radiation scattered from the beam 50 can be examined at the successive elements 7a of the detector 7 of the detector unit 2 (cf. figure 4) . Outside this radiation intensity distribution, obtained from different detec ⁇ tor elements, there can be excluded the known scattering location on the road surface, and the areas immediately above the road surface. If the intensity of the radia ⁇ tion scattered from other areas surpasses a given limit, the obvious conclusion is that there is fog on the road.
• one or several infrared radiation sources be employed in the apparatus of the present invention.
• the radiation frequency range can be generally within the wavelength range of optical radiation, i.e. within the wavelength range of visible light, as well as within the wavelength range of infrared radiation.
• the use of infrared radiation is, however, advantageous, because in the daytime the brightness of the surroundings interferes with the measurements.

Landscapes

• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• General Physics & Mathematics (AREA)
• Computer Networks & Wireless Communication (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Electromagnetism (AREA)
• Optical Radar Systems And Details Thereof (AREA)
• Length Measuring Devices By Optical Means (AREA)
• Traffic Control Systems (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8527822

Family Applications (1)

Country Status (2)

Cited By (6)

Citations (4)

• 1989
  • 1989-02-02 FI FI890504A patent/FI83822C/fi not_active IP Right Cessation
• 1990
  • 1990-01-29 WO PCT/FI1990/000030 patent/WO1990009014A1/en unknown

Patent Citations (4)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events