DE102013003515A1 - Method for measuring speed of moving object, particularly vehicle by using laser device, involves deriving velocity of moving object from change of coordinates of pairs of measurement data by pulses that are generated by transmitting device - Google Patents

Abstract

The method involves emitting a pulsed measurement radiation (7) through a transmitting device (1). The measurement radiation is received at a to-be-measured object (5) through a receiving device (2). The received measurement radiation is supplied to an evaluation device (6) in the form of electrical signals. The coordinates of a data pair formed by a distance value and an angle value are determined. The velocity of the moving object is derived from the change of coordinates of two pairs of measurement data by two pulses that are generated by the transmitting device. An independent claim is included for a device for measuring speed of a moving object.

Description

The present invention relates to a method for speed measurement of vehicles by means of a laser device according to the features of claim 1 and a device for measuring speed according to the features of claim 6.

From the prior art is for example from the DE 10 2007 038 364 A1 A method for measuring the speed of vehicles by means of a laser scanner, in which the light generated by a laser is deflected via a rotating or oscillating mirror and thus continuously scans a measuring range. By means of this construction, measurement data can be obtained with a time delay, from which a speed of a vehicle can be derived. These devices have two disadvantages: First, moving elements are used in the system, which increase the mechanical complexity and also have a corresponding wear. On the other hand, the position change of a moving vehicle within a scan must be compensated because the measurement data are also obtained delayed within a scan.

It is therefore an object of the present invention to provide an improved method for measuring the speed of vehicles by means of a laser device that manages without moving parts. This object is achieved by a method according to claim 1 and a device according to claim 6. Advantageous developments are further defined by the dependent claims.

The invention therefore provides a method for measuring the speed of a vehicle by means of a laser device having the following features:
Emitting a pulsed measuring radiation by means of a transmitting device; Receiving the measuring radiation reflected at the object to be measured by means of a receiving device; Supplying the measuring radiation received by the receiving device to an evaluation device in the form of electrical signals; Determining coordinates of a measured data pair, formed by a distance value and an angle value, by the evaluation device, taking into account the speed of light and the time between the transmission and reception of the measuring radiation; Arranging a scattering device between the transmitting device and the object in order to expand the measuring radiation into at least one beam defining an illumination region; Arranging a collecting device between the object and the receiving device in order to focus the measuring radiation reflected on the object onto the receiving device; Deriving a speed of the moving object from a change in the coordinates of a first pair of measured data, which is generated by a first pulse of the transmitting device and a second pair of measured data corresponding thereto, which is generated by a second pulse of the transmitting device.

By the arrangement of a scattering device between the transmitting device and the moving object thus the measuring beam is expanded to at least one beam. Moving parts can thus be dispensed with altogether.

Preferably, the measuring beam is widened linearly in a horizontal plane.

The receiving device records distance values for several measuring points at the same time. In this case, the measuring radiation reflected on an object is focused by means of the collecting device onto a receiving device. The measuring range is thus initially limited in a first step by an optical opening angle of the collecting device.

Furthermore, it is advantageous to limit the measuring range in its depth. That is, the measurement data acquisition is not limited by the range of the transmitting device, but by distance limits that are trained the transmitting device specifically for the installation. For this purpose, a sequence of depth images of the measuring range is detected by the receiving unit and searched moving objects (vehicles) without limiting the measuring range before starting the actual measurement. From the thus determined distances of the vehicles from the receiving unit, the distance range can be determined in which vehicles are expected and the measuring range is limited to this distance range. In addition, hypotheses about the lanes of the observed lanes can be derived in a statistical procedure. By means of the hypotheses, the measuring range can be further limited to individual lanes in terms of a minimum and maximum limit distance. All distance values provided by the receiving unit are then considered only with regard to this determined range of interest of interest. The advantage here is the restriction to distances across the actual direction of travel, d. H. not the absolute distance to the vehicle is included in the statistics, but only the transverse distance to the vehicle. Incoming measurement data are then first checked as to whether they lie within or outside a range of interest of interest. Those that are outside are then not fed to the arithmetic unit.

The collecting means may be a collecting optical system such as a simple lens or a multi-lens system, e.g. B. be a lens whose focal length determines the magnification of the measuring range to the receiving device. Therefore, it can be provided that, matching the measuring range, the focal length of the collecting device is matched to the receiving device by application of the set of radiation. For example, a line sensor or, in a preferred embodiment, a matrix sensor may be provided as receiving device. The receiving device detects a single distance value in each measuring point of the line or matrix sensor. In this case, the angle value from which the part of the beam has hit the collecting device results from the position of the measuring point on the receiving device. In order to be able to combine the measuring points, which are detected at one time, into one depth image, it is possible with preference to use a receiving device with an electronic shutter, which makes it possible to read only the measuring points which were detected at the same time. Ideally, the shutter is only opened when laser pulses are expected from a desired distance range (this method is also referred to as range gating).

The advantage of this embodiment is that all measuring points of the receiving unit detect the distance values of the measuring range in a depth image at one and the same time. The depth image describes a measuring cycle for the speed measurement according to the invention. This eliminates the need to compensate for the acquisition of time-delayed measurement data, since the position change of moving objects compared to the speed of light are negligible and the objects appear quasi-static.

As a receiving device, depth-measuring semiconductor sensors such as, for example, depth-measuring CCD (charge-coupled device) or depth-measuring CMOS (complementary metal oxide semiconductor) sensors can be used. The receiving device converts the measuring radiation into electrical signals and transmits them to an evaluation device.

All measurement points that represent measurement data pairs in the form of a distance value and a position that are acquired at the same time represent a so-called depth image. Since moving objects do not represent a point radiator but in practice have a spatial extent, it is preferable in the depth images searched for such groups of pairs of measured data, which form a perpendicular pair of paths, that is to say describe a right angle. These right angles are searched in the following depth images. In order to prevent the data volume from growing too much when comparing several depth images, the pairs of measured data describing a right angle can be replaced by model data which, for B. include the coordinates of a vertex. The model data summarized in this way are stored in a buffer and compared with the associated model data in the following depth images. From the change of location of the coordinates, such. As the corresponding vertices of the model data, the speed of the object to be measured is determined.

The device used for measuring the speed of a moving object, which operates on the principle of the time of flight principle, has the following features:
a transmitting device which operates according to the time of flight principle, for emitting a pulsed measuring radiation; a receiving device for receiving the measuring radiation reflected at the object to be measured; an evaluation device, wherein the receiving device, the receiving measurement radiation in the form of electrical signals of the evaluation supplies, taking into account the speed of light from the time between transmission and reception of the measuring radiation, a pair of measured data, formed by a distance value and an angle, determined between the laser device and the object is arranged a scattering device which expands the measurement radiation into at least one beam defining an illumination region; and a collecting device is arranged between the object and the receiving device, which focuses the measuring radiation reflected on the object onto the receiving device.

Alternatively, instead of a pulsed measuring radiation, an amplitude-modulated continuous wave measuring radiation can also be used in order to determine the distance measurement according to the time of flight principle instead of the duration of pulses via the phase shift during the light transit time.

Furthermore, a receiving device is provided, in particular a TOF-CCD (time-of-flight CCD sensor), for receiving the measuring radiation reflected at the object to be measured. Furthermore, a collecting device is provided which is arranged between the object and the receiving device and defines a measuring range by its optical opening angle, which is preferably smaller than or equal to the scattering angle of the illumination region, for example of 45 °. The measuring radiation reflected on an object within the measuring range is focused onto the receiving device by means of the collecting device, wherein the receiving device receives the received signal Measuring radiation in the form of electrical signals to an evaluation supplies, which determines a distance value taking into account the speed of light from the time between transmission and reception of the measuring radiation. Because the distance value is received at a specific position of the receiving device, at each position of the receiving device, which corresponds to a predefined angle value, a measured data pair is present at the distance value measured at this position.

The receiving device is preferably adapted to the shape and size of the illumination area. With a linear illumination with a scattering angle of up to 180 °, a cost-effective line sensor offers itself. In the case of illumination with a scattering angle of 180 ° to 360 °, a matrix sensor is available on which, for example, in the case of a 360 ° linear illumination by a collecting device, an annular line is preferably displayed on the receiving device. A matrix sensor is also suitable for a measuring range with several line-shaped illuminations.

Basically, for the number of measuring points of the receiving device to take into account, which resolution per degree of the measuring range is wanted. At 45 ° measurement range and 0.1 ° resolution, a sensor with at least 450 measurement points per receive line is required. In this case, the receiving device, in particular a sensor, together with its collecting device, must be focused on the line emitted into the illumination area.

In a further alternative embodiment, the laser device designed as a transmitting device comprises a transmitting device which emits the measuring radiation in different planes whose illumination areas can intersect or are aligned parallel or divergent.

In a further alternative embodiment, the laser device designed as a transmitting device comprises at least a first laser diode and a second laser diode in order to emit the measuring radiation in different planes whose illumination areas can intersect or aligned parallel or divergent.

In a particularly preferred embodiment, not shown, a receiving device is used, in which the evaluation unit is integrated on the receiving device, so that the evaluation device outputs a distance value directly for each measuring point. For this purpose, a synchronization with the transmitting device is necessary.

Further important features of the present invention will become apparent from the following detailed description in conjunction with the claims and figures. Hereinafter, a preferred embodiment of a method according to the invention will be described and explained in more detail by means of the figures.

1a a first embodiment of an apparatus for performing a method according to the invention for measuring the speed of vehicles;

1b a detailed view of a receiving device according to the invention;

2 the first embodiment in a plan view;

3 A second embodiment of an apparatus for performing a method according to the invention for measuring the speed of vehicles;

1a shows a first embodiment of an apparatus for performing a method according to the invention for measuring the speed of vehicles. Such a device has a laser device designed as a transmitting device 1 on. The laser device 1 sends a pulsed measuring radiation in a predeterminable direction. Downstream of the transmitting device is a scattering device 3 , which has the task, the measuring radiation 7 in at least one, an area of illumination 8a defining, expanding beam. This expanded beam is at an object to be measured 5 reflected and by means of a collection device 4 focused on a trained as a receiving unit CCD sensor. The sensor converts the radiation into electrical signals and leads them to an evaluation device 6 to.

For ease of understanding the invention, a method according to the invention is intended to provide a speed of a moving object 5 derive from an alteration of the object coordinates, which are derived from a first depth image, by a first pulse of a transmitting device 1 is generated and the corresponding coordinates of a second depth image by a second pulse of the transmitting device 1 to be generated.

In this case, a depth image is comparable to a single scan of a laser scanner, which detects a measuring range with a moving mirror. At the same time the measuring range becomes 8b with the objects in it 5 via a plurality of measuring points, consisting of a pair of measured data, each with a distance value and an angle value, detected at the same time. Thus, each depth image represents A snapshot with all measuring points and their measured data pairs of the measuring range. A schematic representation of the measuring range 8b or the illumination area 8a is in a plan view of the first embodiment in 2 shown. It can also be seen from this figure that the measuring range 8b on the one hand by the optical opening angle of the collector 4 and is subsequently limited in its depth in that the measurement data acquisition takes place within distance limits which are learned by the transmitter specifically for the installation site. According to 2 is such a distance limit by a double line 12 marked. In 1b is still schematically a receiving unit 2 with several addressable points, so-called measuring points M1 to M7 shown schematically. As already explained above, an angle value from which the part of the beam is hit on the collecting device results from the position of the measuring point on the receiving device.

In the measuring range 8b Basically, there are both static objects, which are typically buildings bordering the street side, trees or parked vehicles that together form a static background, as well as dynamic moving objects 5 , in particular moving vehicles. Likewise, it is also possible that there is no pair of measured data for individual measuring points. These measurement points are marked internally as "infinite" remotely by assigning the maximum measurable distance to the respective angle values.

In accordance with the purpose of the method of detecting the speed of vehicles, only the measured data pairs which are a dynamic moving object are of importance for the measurement data processing 5 can be assigned. For this purpose, a selection of the measured data pairs of the dynamic moving objects 5 from the total amount of all measured data pairs useful, but not mandatory.

To measure data pairs of moving objects 5 , In particular of vehicles to detect, is searched in each depth image for pairs of measured data, which together describe a pair of routes in which the routes 9 and 10 a right angle 11 include each other (hereinafter also called right angle). Such a route pair is a suitable model for describing vehicles, regardless of the type of vehicle, by the pairs of measured data recorded in the measuring area (see 2 ).

The vehicle 5 reflects the measuring radiation 7 over the entire passage through the measuring area with its vehicle side facing the laser device. The pairs of measured data obtained from these measuring points form an approximately rectilinear course through which a first estimation line is laid using mathematical approximation methods. By the measurement data of the first and last measurement point of the vehicle side, the first estimation line is limited to a first distance of certain length.

In addition to these measuring points, which supplies the vehicle side in each case in a depth image, incoming traffic through the passage additionally pairs of measured data only from the front of the vehicle and depending on the size or opening angle of the measuring range then generated by the rear of the vehicle. In the case of outgoing traffic, pairs of measured data are also generated from the rear of the vehicle via the passage and, depending on the size or opening angle of the measuring range, at the beginning of the vehicle front. These measured data pairs also form approximately a straight-line course, which is approximated by a second estimation straight line. By the measured data pairs of the first and last measuring point of the vehicle front or the vehicle rear, the second estimation line is limited to a second distance of certain length.

The number of measured data pairs obtained from the front of the vehicle or the rear of the vehicle essentially depends on the reflection properties of the surface and the distance of the vehicle 5 to the laser device 1 from the illumination area 8a , the front and rear of the beam and the angle of incidence of the laser beam on the rear or the front. The probability that a measured value is obtained is the higher the closer the vehicle is to the laser device and the steeper the partial beam strikes its surface. This means that the front and rear surfaces, far away from the laser device (outside the measuring range) and near the 0 ° [deg.] Range (flat angle of incidence and small angular range) only provide few to no pairs of measured data.

That is to say, a vehicle traveling through the measuring range delivers pairs of measured data, which, comparable to a flip book, move from one side to the other over the individual depth images.

The measured data pairs supplied with each depth image, consisting of distance and angle values, are converted into Cartesian coordinates that relate to a coordinate system determined by the laser device. It makes sense to make the center of the receiving device 2 the origin of the coordinates, the Y-axis being described by the axis perpendicular to the receiving device. Advantageously, the laser device is aligned with the roadway so that the central axis aligned perpendicular to the direction of travel is, whereby the X-axis and the direction of travel coincide. To disturbing z. B. by shading the transmitting device 1 To keep as small as possible, it is advantageous if the coordinate origin of the transmitting device 1 as close to the coordinate origin of the receiving device 2 lies, in particular these fall into a common point, as z. B. in a coaxial arrangement of transmitting device 1 and receiving device 2 the case is.

With well-known algorithms, it is then possible to determine all measuring points lying at a right angle from each depth image while specifying a specific tolerance width (quality). As already explained, the right angle in the sense of this description should be understood as meaning two paths that meet perpendicular to one another. The goodness is z. B. derived from the transverse distance of the measured values to the estimation line and their distance from each other.

Measurement data pairs which can not be assigned to such a right angle are no longer needed, so that a data reduction can take place around these measurement data.

The pairs of measured data forming such a right angle can be replaced by a model description which determines the right angle with its leg lengths (length of the two distances) and its position in the measuring range. The model data for this model description can be z. Example, the coordinates of the vertex and the coordinates of the free end points of the two routes or the coordinates of the vertex, the lengths of the two routes and the angle includes one of the two routes with the central axis. In any case, the model data includes the coordinates of the vertex. The dataset for the model description is only a fraction of the dataset of the real metrics associated with the right angle.

The model data of the right angles found in each depth image are entered in a buffer. In order to determine the speed for a suitable vehicle, the model data of the individual depth images, which each belong to the same right angle, are combined into a group and a trajectory is determined from the change in the location of the vertices. Belonging to a group, all the right angles can be counted, whose vertices jointly describe a uniform movement.

All model data that can not be assigned to a group is mainly understood as being formed by the static background and can be deleted.

From the change in the location of the vertex, more precisely, its average location change and the frame rate, the speed of the vehicle in question can be calculated, which is described by the model data of this group. Likewise, from the average deviation from the average location change, a quality measure for the speed determination can be derived.

At this point there is a velocity and a trajectory for a right angle. The location of the trajectory can be used to determine the position of the various lanes of a multi-lane road on which the vehicle moves through the measuring range.

In order to use a method according to the invention for the statistical recording of the traffic flow and the traffic density, a speed and a lane, assigned to a time point, can be stored with this available data.

In order to punish speed violations, when a photo point or a virtual detection line is reached, the calculated speed is compared with a preset maximum speed and, in the event of exceeding the preset maximum speed, a photographic recording is triggered in which all legally relevant data is displayed after the successful measurement has been completed.

Since all measured data pairs are determined at the same time, a vehicle is recorded quasi-statically and from the measured data pairs of each depth image, the vehicle length can be derived, with which among other things a classification of the vehicles can be done.

This may be of interest to z. B. to compare the speeds of different vehicle classes such as cars and trucks with different speeds, or to recognize two-wheeled vehicles to capture this in addition to the front photo with a rear-view or trigger a Heckfoto instead of a front photo.

3 shows a second embodiment of an apparatus for performing a method according to the invention for speed measurement of vehicles in a side view. In contrast to the embodiment according to 1 has the transmitting device three as light emitting diodes 1a . 1b and 1c trained subunits. The light emitting diodes each send out a horizontal line with an opening angle of 45 °. The measuring radiation reflected on an object within the illumination area 7 is using the collecting device 4 on a matrix sensor 2 focused as a receiving device. The matrix sensor must be dimensioned so that all illumination areas are completely imaged. With such a device, in particular the illumination range can be significantly increased.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102007038364 A1 [0002]

Claims (10)

Method for measuring the speed of a moving object ( 5 ) having the following features: a) emitting a pulsed measuring radiation ( 7 ) by means of a transmitting device ( 1 ); b) receiving the object to be measured ( 5 ) reflected measuring radiation ( 7 ) by means of a receiving device ( 2 ); c) supplying the by the receiving device ( 2 ) received measuring radiation to an evaluation device ( 6 ) in the form of electrical signals; d) determining coordinates of a measured data pair, formed by a distance value and an angle value, by the evaluation device ( 6 taking into account the speed of light and the time between emission and reception of the measuring radiation; e) arranging a scattering device ( 3 ) between the transmitting device ( 1 ) and the object ( 5 ) to transmit the measuring radiation into at least one, an illumination area ( 8a ) expanding beam; f) arranging a collecting device ( 4 ) between the object and the receiving device ( 2 ) to focus the measuring radiation reflected on the object on the receiving device; g) deriving a speed of the moving object from a change in the coordinates of a first measured data pair, which is generated by a first pulse of the transmitting device and a corresponding thereto second measured data pair, which is generated by a second pulse of the transmitting device. A method according to claim 1, characterized in that in the pairs of measured data, which are obtained by a pulse of the transmitting device, is searched for those having a perpendicular pair of paths ( 9 . 10 ), that is a right angle ( 11 ) describe that these measurement data pairs are replaced by model data, which also include the coordinates of a vertex, and stored in a buffer, that the model data of the individual pulses, each replacing the same right angle to a group and the change of location of the coordinates the vertices of the model data of a group the speed of the object to be measured is determined. A method according to claim 1 or 2, characterized in that in step f) of the measuring beam is linearly expanded in a horizontal plane. Method according to one of the preceding claims, characterized in that the measuring radiation in a plurality of addressable points, so-called measuring points (M1, M2, ...), line or matrix impinges on the receiving device and the angle value derived from a position of the measuring point on the receiving device becomes. Method according to one of the preceding claims, characterized in that the receiving device comprises an electronic shutter which is designed to read out the measuring points (M1, M2, ...) which are detected at the same time. Device for measuring the speed of a moving object ( 5 ) having the following features: a transmitting device ( 1 ), which operates according to the time of flight principle, for emitting a pulsed measuring radiation ( 7 ); a receiving device ( 2 ) for receiving the object to be measured ( 5 ) reflected measuring radiation ( 7 ); an evaluation device ( 6 ), wherein the receiving device receives the received measuring radiation in the form of electrical signals of the evaluation device ( 6 ), taking into account the speed of light from the time between transmission and reception of the measuring radiation ( 7 ) a measured data pair, formed by a distance value and an angle value, determined, characterized in that between the laser device ( 1 ) and the object ( 5 ) a spreading device ( 3 ) is arranged, the measuring radiation in at least one, an illumination area ( 8a ) sub-beam, divides and between the object and the receiving device ( 2 ) a collecting device ( 4 ), which focuses the measuring radiation reflected on the object onto the receiving device. Device according to claim 6, characterized in that the transmitting device ( 1 ) is designed as a laser device, in particular as a laser diode. Device according to one of claims 6 or 7, characterized in that the laser device ( 1 ) comprises at least a first laser diode and a second laser diode. Device according to claim 8, characterized in that the first ( 1a ) and the at least second laser diode ( 1b ) are arranged in different planes, in particular one above the other. Device according to one of claims 6 to 9, characterized in that the scattering device ( 3 ) is formed such that the illumination area ( 8a ) has an angle of at least 5 ° and a maximum of 75 °.

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