DE102006005231A1 - Method for determination of distance of an object, involves stereoscopic analysis of two picture fields comprising digital camera pictures, which are recorded by stationary camera system - Google Patents

Abstract

The method involves stereoscopic analysis of two picture fields (R,L,R',L') comprising digital camera pictures, which are recorded by a stationary camera system (K). The object (3) with the camera system comprises two picture recording positions (1, 2) towards the different object. A distance (delta ) is recorded for both the picture fields which are gained by evaluation of light or contrast differences between the same neighboring picture pixels. The distance (A) is calculated from the distance of both picture recording positions and the parallaxes. The same cameras are used for the focal length as well as the number of pixels and size of image sensors. An independent claim is also included for an arrangement for the determination of the distance of an object.

Description

The The invention relates to a method and an arrangement for determination the removal of an object, preferably for the purpose of visibility determination. Distance and visibility are closely related in this respect, as the visibility after in use Procedure the knowledge of the length presupposes a measuring path used for visibility determination. The presented solution therefore concerns a new possibility the determination of the distance, which in combination with further process steps particular advantage for the visibility measurement can be used.

The possibility an accurate determination of the distance of objects and / or the current visibility is in many technical areas and areas of life, especially in transport, of very great importance. She plays to Example, an important role in the automotive sector, in the aviation and Rail traffic as well as in the inland and maritime navigation. The number, due incorrectly determined distances or incorrectly estimated visibility, arising accidents is significant and causes every year, besides anyway not acceptable personal injury, high economic costs. This is equally true for heavy accidents inland, air and maritime transport too.

In front In particular, the determination of distances in maritime transport are special To observe boundary conditions. Unlike, for example, in the car and rail transport lacks maritime transport at least in the immediate Of sea-going vessels often at prominent points, which for the Distance determination as well as visibility determination are used can. It should also be noted that large Ships have extremely long braking distances and, in view of possible evasive maneuvers, immense size Have turning radii.

The Visibility is generally based on contrast changes, respectively the reduction of the contrast of an object to his Environment determines which due to the between the one Observers and the object lying air layers caused Light scattering and absorption occurs. To be comparable to each other Visibility information is provided by the VDI Directive 3786 a standard visibility for a threshold contrast of ± 0.02. ie ± 2% established. In practice, the visibility is measured by transmission measurements, Scattered light measurement methods or with the help of contrast evaluations Determined objects known distance.

at The transmission measurements are the visual range by visual contrast estimates and by scattered light measurements over determined relatively long measuring distances. These measurements give the most accurate data, but are very vulnerable as integral methods in the Regard to the smallest mechanical disturbances, that is in particular position changes the transmitter and receiver used, which are, for example, optical or radio technical Sender and receiver can act. Transmission measurements also set very powerful transmitters and highly sensitive receivers ahead, which are correspondingly expensive. In the scattered light measurement methods have sender and receiver usually at a small distance, the results obtained on size Distances are extrapolated. This often leads to comparatively high Measurement errors, which for many applications, for example, the already mentioned maritime transport, unacceptable are.

A Contrast evaluation for objects with a constant vis-à-vis the observer and thus certain distance is, for example, in the meteorological Practice applied. However, it is obvious that this method to determine the visibility of moving vehicles basically can not be used.

As far as in the already mentioned transmission and scattered light measurements, the distance for this purpose used objects is not known, this is determined in practice, for example by means of radar or LIDAR measurements. However, these active methods of range determination require, as already mentioned, very high-performance, high-frequency or optical transmitters and correspondingly accurate and sensitive receivers. With respect to moving objects, such as road vehicles, they also have the disadvantage that their accuracy is significantly reduced by obstacles or in curves by roadsides. With regard to the Radarortung also a metallic and smooth as possible surface of a targeted for the purpose of determining distance object is required. All these are boundary conditions that are often not optimally fulfilled in land transport and are generally not given at all with respect to ocean shipping. As another possibility of distance and visibility determination, therefore, passive methods, that is, methods are used in which additional high-frequency or optical transmitter are not needed. In particular, video cameras and methods of digital image evaluation come increasingly used.

For example, by the EP 10 67 399 A2 describes a method for visibility determination, which also includes the determination of the definition by means of a binocular video transmitter. The distance determination is carried out according to the document by triangulation. Although triangulation is a classical technical method which is used in particular for land surveying, this method presupposes the determination of geometrical quantities in an observation triangle, in particular the determination of the angles of the triangle for which a theodolite or a device comparable thereto is required. In that regard, the arrangement-technical effort is comparatively high here. By the DE 100 34 461 A1 A method for determining the visibility is described in which the measurement of the change of contrast values of two measuring positions which are at different distances from an object used for the measurement is carried out. Also in this solution, the distance is determined by triangulation. In addition, it is from the DE 196 40 938 A1 It is known to use a stereoscopic camera system to improve the accuracy of traffic observations.

task The invention is a solution to provide distance measurement, which is equally good for the Use in stationary and mobile systems is suitable and in particular for the purpose the visibility determination a sufficiently accurate distance determination allows. For this purpose, a method and a method suitable for carrying out the method Specify arrangement, the basic inventive solution a to allow simple construction of the measuring arrangement.

The The object is achieved by a method having the features of the main claim solved. A problem solving and to carry of the method is appropriate by the 1st claim characterized. Advantageous training or further education The invention are given by the respective subclaims.

To the proposed method is the distance determination through the evaluation of stereoscopic, in each case of two partial images existing digital camera images, which of a stationary or on a mobile unit arranged camera system can be detected. According to the invention is a Object, which differs in brightness and / or contrast different from its surroundings, from two different in the direction of the object, taken a known distance from each other having image positions. In this case, two stereoscopic image pairs are detected, for which each determines the parallax of the two sub-images forming them becomes. To determine the parallaxes are for the fields by a Evaluation of brightness and / or Contrast differences between adjacent image pixels initially same Image sections determined. From the same image excerpts can be assumed if for larger areas of both Partial images in horizontal or preferably in horizontal and vertical direction a same sequence of brightness or Contrast transitions between the neighboring pixels is detected. After determining the to be evaluated the same image sections is determined how far these two image sections in the comparison of both partial images laterally offset or shifted from each other. By simple count the pixels or pixels of this offset and a multiplication the number of pixels determined with the known for the camera used Pixel size is finally the Parallax the respective stereoscopic image acquisition to calculate. In addition, then from the for the stereo recordings of both image acquisition positions calculated parallaxes and the known distance of the two image pickup positions to each other the distance of the object can be calculated.

For the practical Implementation of the procedure, the image-technical evaluation, including the count the number of pixels by which the respective two partial images of both stereoscopic Shots are laterally offset from each other, and the calculation Of course, the distance preferably computer technology, although basically also the possibility a manual count and calculation is given.

bestimmt werden. Dabei gilt, wie bereits betont, die Bedingung, dass weder p₁ = p₂ noch p₁ >> p₂ ist. Für einen Fehler in der Tiefenauflösung von vorzugsweise weniger als 10 % sollten dabei, unter anderem auch aufgrund der zuvor genannten Bedingung, die Basisbreite b des stereoskopischen Kamerasystems und der Abstand Δx der beiden Positionen der Bildaufnahmen so gewählt werden, dass b << a und Δx << a sowie Δx >> b gilt. Als Orientierung beziehungsweise ungefähre Größenordnungen können dabei eine Basisbreite b des stereoskopischen Kamerasystems zwischen 0,025 % und 0,25 % und ein Abstand Δx der beiden Bildaufnahmepositionen zwischen 0,1 % bis 3 % der gemäß dem jeweiligen Einsatzfall typischerweise zu bestimmenden Entfernungen angegeben werden. Jedoch handelt es sich hierbei, wie betont, um ungefähre Größenordnungen, welche die Erfindung insoweit nicht beschränken, zumal die jeweils tatsächlich sinnvollen Relationen einerseits von den räumlichen Verhältnissen am An- beziehungsweise Einbauort des Kamerasystems und den typischerweise zu bestimmenden Entfernungen beziehungsweise deren erforderlichenfalls zu bestimmenden Größenordnungen und andererseits von dem dabei jeweils zugelassenen Messfehler abhängen. Insbesondere im automotiven Bereich ist dabei ein An- beziehungsweise Einbauort für das Kamerasystem zu finden, der hinsichtlich der möglichen Basisbreite für das Kamerasystem im Einklang steht mit dem zu bestimmenden Entfernungsintervall und auch mit dem, in Ansehung der Geschwindigkeit des automotiven Systems und/oder dessen Bremsweg, für die Entfernungsbestimmung zulässigen Fehler. Den Forderungen nach einem kleinen Messfehler kann durch hinreichende Basisbreiten beziehungsweise Abstände zwischen den Messpositionen Rechnung getragen werden, wobei die Basisbreite im Hinblick auf die Sichtweitebestimmung aber vorzugsweise mehr als 6,5 cm beträgt, was dem typischen menschlichen Augenabstand entspricht. Andernfalls ist auch eine entsprechende Fehlerbetrachtung erforderlich, da wie vorstehend ausgeführt, die vorgenannten Werte auch von dem im jeweiligen Einsatzfall zulässigen Fehler abhängen.Under the condition that both parallaxes are unequal, that is, the parallax at the closer to the object image pickup position does not tend to parallax at the more distant image pickup position, but on the other hand both parallaxes are not extremely different from each other, the distance may be according to the invention after the relationship

be determined. Here, as already emphasized, the condition holds that neither p ₁ = p ₂ nor p ₁ >> p ₂ . For an error in the depth resolution of preferably less than 10% should, among other things due to the above-mentioned condition, the base width b of the stereoscopic camera system, and the distance Δx of the two positions of the image shots are set to be b << a and Δx << a and Δx >> b. As orientation or approximate orders of magnitude, a base width b of the stereoscopic camera system between 0.025% and 0.25% and a distance Δx of the two image pickup positions between 0.1% and 3% of the distances typically to be determined according to the respective application can be specified. However, this is, as emphasized, to approximate orders of magnitude, which does not limit the invention insofar as the actually meaningful relations on the one hand by the spatial conditions at the installation or installation of the camera system and the distances typically to be determined or their order of magnitude to be determined if necessary and on the other hand depend on the respectively admitted measurement error. In particular, in the automotive sector is to find a place or installation for the camera system, which is in terms of the possible base width for the camera system in accordance with the distance interval to be determined and also with respect to the speed of the automotive system and / or its braking distance , errors permissible for the distance determination. The requirements for a small measurement error can be taken into account by adequate base widths or distances between the measurement positions, but the base width with regard to the visibility determination is preferably more than 6.5 cm, which corresponds to the typical human eye distance. Otherwise, a corresponding error consideration is required because, as stated above, the above-mentioned values also depend on the error permissible in the respective application.

Based on the inventively determined distance can then, based on known approaches, as well as from the DE 100 34 461 A2 known method, the visibility are determined by the already evaluated brightness and / or contrast information is used to determine the extent to which change the absolute values of brightness or contrast between the images taken at both image positions. In the case of a contrast attenuation at the image acquisition position farther away from the object by the distance Δx, a corresponding range of vision reduced relative to the previously determined distance results, which can also be normalized on the basis of the relationship defined by the VDI Guideline 3786 for specifying a standard visual range. Optionally, however, it is also advantageous to redetermine the distance in the same way at two other image positions and to perform the contrast or brightness assessment with respect to the two different distances. In general, it is advantageous to repeatedly determine and average for improved accuracy, range and / or visibility in short time intervals.

Especially when using the method for use in ships or Vehicles become the determined distance and / or the visibility for the driver output on a display. According to practice-relevant further education of the method Furthermore the captured by the camera system images the driver a separate screen immediately made available become.

at an arrangement for determining the distance of an object or to carry out of the method described above is the camera system according to a basic Embodiment of two, in the direction of the object with a known Distance Δx spaced stereo imaging systems, each with at least a camera. The for capturing the partial images for the stereoscopic images serving optical components of these stereo imaging systems a base width equal to each other. Both stereo imaging systems are equipped with a software and hardware-based control and evaluation unit which is used to calculate the between the fields of the Stereoscopic images taken by both stereo imaging systems existing parallaxes and to calculate the distance of the object from these parallaxes, the known base width and the known Distance of the stereo imaging systems is formed. The means of stereo image systems digital image recordings are made by this control and evaluation unit fed. Dependent on In addition, both stereo image systems are used by the respective application of the camera system synchronized with each other. While this is for example at a bigger ship with two up to several 100 m far apart image pickup positions not because of the slow movement speed of the ship is required, must be fast moving vehicles for synchronization the cameras of the camera system are taken care of.

Another fundamental form of training, designed exclusively for arrangement on mobile units, is given by the fact that the camera system has only one stereo image system with at least one camera and by a control and evaluation unit assigned to it within a short time interval Δt in which the vehicle moves Position by a, calculated on the basis of its speed distance .DELTA.x compared to the object used for the distance determination changed, is controlled for repeated image acquisition.

For both previously shown forms of training is a possibility of variation given by the fact that in the or the stereo image system a camera replaced by a deflection mirror and a beam splitter and the surrounding image of the deflection mirror in the remaining a camera is mirrored. Depending on the training form will be there captured in a very short time two fields or both fields temporally parallel to the appropriately designed optical sensor supplied to the camera.

in the With regard to use at night, all the above forms of training be extended by an infrared unit, so that the distance determination or visibility determination based on infrared images he follows.

Next a display for displaying the determined distance and / or visibility and an optional screen for immediate use Playback captured images can be at one for use in vehicles trained arrangement coupling the arrangement, in particular the one belonging to her Control and evaluation unit, with a in the handling of the Vehicle automatically intervening security system provided be to automatically match the driving behavior of the vehicle adapt.

at a practical training form, which for use in a road motor vehicle trained is, is the basic width of the camera system (K) to the space adjusted at the installation location is but at least 6.5 cm. For example, it allows a base width of 10 cm, in terms of usual vehicle speeds as well as resulting braking distances and due to that in the road traffic required Distance and / or visibility statements a sufficient accuracy. It also advantageously allows the camera system in the case to arrange a motor vehicle headlight.

at another, for Training provided is the arrangement at the or arranged in the engine of a locomotive, wherein the base width of the camera system (K) is preferably 30 cm, but possibly also the entire width of the locomotive can take.

The Invention will be explained in more detail below with reference to embodiments, wherein the associated Drawings also relate to representations, which for the derivation the underlying mathematical considerations of the invention serve. In the drawings show:

1 : The schematic representation of an observation situation in the stereoscopic detection of two points removed from an observer, preferably an object

2 : A diagram illustrating the dependency of the relative error of the depth resolution on the logarithm of the object distance

3 : The observation situation according to 1 in a representation for explaining the stereoscopic parallax

4 : An observation situation similar to those after 1 and 3 , with an observation of the object from two observation positions at different distances from it

5 : A diagram showing the dependence of the logarithm of the object distance on the ratio of the stereoscopic parallaxes in an observation situation according to 4

6 : An embodiment of the inventive arrangement with a camera system on a ship

7 : An embodiment of the arrangement according to the invention with a camera system on the engine of a locomotive

8th : The embodiment according to 7 with a simpler designed camera system

9a : The distance determination of a cloud, which is approximately above the camera system is

9b : Determining the distance of the cloud according to 9a , where the cloud is not directly above the camera system

10 : The schematic representation of the evaluation of the images captured by the camera system.

The 1 to 5 should serve to derive the mathematical considerations underlying the invention. The 1 shows an observation situation in the stereoscopic observation of two points A and B, which are preferably on an object 3 are located. Opposite the observation position 1 owns the object 3 the distance a. To explain the geometric relationships, it is assumed that the distance a is substantially greater than the so-called base width, the distance b between the eyes of an observer or the sensors of a camera system K (a >> b). Then it follows that the angle α is for small angles, that is, large distances a of the object 3 to the observation position or image recording position 1 , and the distance a and the base width b are as follows: a ≌ b / α. (E1)

By forming the differential, respectively deriving the aforementioned equation according to a, one obtains the blur for the distance to be determined according to the following relationship: da = -bdα / α 2 = -A 2 d.alpha / b. (E2)

It follows from the above relation E2 that the blur or depth resolution da is proportional to the square of the distance (a ² ) and inversely proportional to the base width (b). In addition, it can be seen that the relative error da / a increases linearly with the distance a. Here, the negative sign has no significance for the absolute size of the depth resolution or blur. The results obtained according to these mathematical relationships are shown in the diagram of FIG 2 in which the relative error da / a is plotted in percent over the logarithm of the distance a. It was assumed that dα ≌ 1/2 ', which gives a small but acceptable error in the context of the following 1 resulting in the 2 shown curves is entered. From the diagram it can be seen that for a depth error of 10% to 20%, a good stereoscopic distinctness or width estimation is possible for an eye observation with a base width of approximately 0.065 m (eye relief) up to a distance a of approximately 100 m. With the same relative error, width estimates of up to 1.5 km and a base distance of 10 m to a distance of 13.4 km are possible for a base width of 1 m. Metrologically, this means that by means of stereoscopic images using a camera system K with a base width of 10 m, a good depth resolution up to about 15 km is given. If one works in extreme cases, especially in stationary systems, with a base width of 100 m, depth resolutions of more than 25 km are possible for a depth error of 10% to 20%, as long as this is not fundamentally opposed by bad weather conditions.

The 3 shows the observation situation according to the 1 in a slightly modified representation. This representation takes into account that in a stereoscopic viewing or image acquisition by the different visual or image axes of a viewer or camera system K, a parallax p occurs, as a result of which the image sections on the retina of an observer or the image plane of a camera system K are shifted laterally relative to one another. The geometric conditions given here are determined by the 3 shown. Based on the figure, the parallax is determined according to the relationship p = A L A R - B L B R , (E3)

This parallax p, namely the difference of the distances of the pixels between the right and the left field of a stereoscopic image can be very well determined in digital cameras, in particular computer technology by counting the pixels. In the boundary conditions that the distance a of the object 3 is large compared to the depth extent .DELTA.a and the focal length of a stereo camera used for observation about the distance of the objective lens to the image receiving sensor, can be from the above equation, the relationship Δa ≈ (pa 2 ) / (bf) (E4) derived.

The 4 represents the relationships when the object 3 from two different observation or imaging positions 1 . 2 is detected, which in the direction of the object 3 have a distance Δx, wherein this distance .DELTA.x small compared to the actual distance a of the object 3 is. When changing the image pickup position sets the image pickup position 2 a parallel shift of the image pickup position 1 by Δx. If the observation takes place with one and the same stereo image system consisting of two cameras from the two different positions or with two completely identical stereo image systems spaced apart by Δx from each other, the distance is at the image recording position 2 a '= a + Δx. As a result, one can look for both image pickup positions 1 . 2 equating and obtaining equations resulting from the aforementioned relationship E4: p 1 a 2 = p 2 (a + Δx) 2 , (E5)

Therein p ₁ and p _{2 are} the stereoscopic parallaxes at the two observation or image acquisition positions 1 . 2 , This equation can now be solved after the distance a and gets:

The equation E6 forms the basis for the method according to the invention, according to which an object is detected stereoscopically from two positions slightly apart in the direction of the object, the parallax between the respective two partial images of both stereoscopic images is determined by counting the pixels and multiplying this pixel number by the pixel size finally, from this the distance of the object can be derived. However, certain boundary conditions must be observed. If, in fact, both parallaxes approach very strongly in terms of their value, ie, p ₁ tends towards p ₂ , the distance to be calculated using the equation approaches infinity, that is, no depth resolution is given and reliable distance determination is no longer possible. Since, as is known, the parallax strongly increases with increasing proximity of a stereoscopically observed or recorded object, a reliable distance determination is no longer possible even for cases in which p ₁ is much larger than p ₂ (p ₁ >> p ₂ ). The object is then too close to the camera system K, in which case other boundary conditions mentioned in the above explanations, for example, that the distance very large compared to the distance .DELTA.x of the measuring positions and also very large compared to the base width, ie the distance b between two cameras of a stereo imaging system should be injured. On the other hand, a very good depth resolution is obtained, provided that the values of both parallaxes on the one hand are not nearly equal, but on the other hand are not too different, that is, the condition p >> p _{2 is} satisfied. The permissible size of the difference between the two parallaxes p ₁ and p ₂ is determined essentially by the relative error permitted for the measurement.

The 5 shows a diagram illustrating the dependence of the logarithm of the distance a of the object to the ratio of the stereoscopic parallax. The resulting curves are for the case of a constant object depth Δa and for different distances between the image pickup positions 1 . 2 , that is Δx as a parameter. It can be seen that with increasing distance Δx of the image pickup positions 1 . 2 with otherwise constant focal length f and base width b of the cameras and a constant Δa a very good depth resolution for ratios of p ₁ / p ₂ of 1.01 to 3 is achieved. In the error estimation of the distance a determined in this way and any visibility determined therefrom, the results of the 4 and 5 or the equations explained as well as the pixel number and size of the digital cameras are taken into account. In this way one obtains from the digital images, based on the same image excerpts, the distance a of objects, such as in the application of ocean shipping, the distance of another ship or mist walls with respect to the water surface. The use of identical image sections with respect to the parallax-loaded partial images of the stereoscopic image recordings can be ensured by the evaluation of image regions with defined brightness or contrast transitions. That is, equal gradients of brightness or contrast between adjacent pixels mean equal image positions. On the other hand, the fact that arises between the image recordings of the first image pickup position 1 and the second image pickup position 2 set different contrast or brightness ratios, use to determine therefrom in known, determined in accordance with the invention distance a the visibility.

For the realization of the distance Δx between the image pickup positions 1 . 2 Two basic approaches are possible. It is possible, the recordings with a stereo camera rel a stereo image system first at an image pickup position 1 to make the stereo camera in a short period of time .DELTA.t to the other image pickup position 2 to move and the object 3 to capture again or to use a camera system K with two stereo cameras or stereo imaging systems, which are offset by the distance .DELTA.x offset from each other, but have the same base width b. From this fact and the different practical application cases, the following explanatory embodiments arise.

The 6 shows the use of the inventive arrangement using the method according to the invention using the example of a seagoing vessel. Due to the structural conditions and the size of the ships will work here with a camera system K, which as shown in the figure consists of 4 cameras K ₁ , K ₂ , K ₃ , K ₄ , in each case the camera K ₁ , K ₂ and the camera K ₃ , K _{4 form} a stereoscopic camera part system. As an example, let's talk about a ship 6 assumed, in which the usable for the base width b distance between port and starboard about 30 m and the length of the bow 7 to the rear 8th such is that a Δx of about 300 m can be realized. If a depth error of 10% to 20% is now allowed for the distance determination, then with an arrangement according to the illustrated embodiment, using digital cameras K ₁ , K ₂ , K ₃ , K ₄ with 5 megapixels and a pixel dimension of approximately 2.5 μm with a parallax difference of about 0.5 pixels, distances of 5 to 10 km with a very good depth resolution. For computer technology processing and direct signaling of the result on a terminal would be for the captain of the ship 6 good alternatives to surfacing obstacles. Any obstacles could possibly be detected automatically with appropriate design of the arrangement, calculated their distance by the method according to the invention and these are signaled to the master directly on the display. However, it is also conceivable to repeatedly determine the range of vision by means of any objects with a sufficient distance, by determining the distance to these objects and deriving the range of vision according to the illustrated principles. If the master is constantly informed of the prevailing visibility, he may then, in the event of an emerging obstacle, make use of his technical experience of estimating, for example, the size of an oncoming ship, the distance of the object 3 assess well and, as a result of this assessment, take the necessary measures.

The 7 relates to an embodiment for the preferred use in a land vehicle, such as the power car 9 a locomotive or a car 9 So a vehicle with over the ocean vessel 6 of the above-described embodiment considerably smaller dimensions, which also generally moves much faster than a high-sea ship in general 6 , In this embodiment, the camera system K consists of two cameras K ₁ , K ₂ for the stereoscopic detection of an object, not shown here 3 to which the distance a is to be determined. The basic idea of the invention, according to which the object 3 from two in the direction of the object 3 different image pickup positions 1 . 2 is to be captured, this form of training takes into account that the camera system K the object 3 during the movement of the vehicle 9 detected twice at a short time interval of Δt. This is equivalent to detection by means of two stereo image systems arranged at a distance Δx, since the vehicle 9 and with it the camera system K changes its position within the time interval Δt by a distance Δx. If one goes by the conditions of a road vehicle 9 out, which moves at a speed of 150 km / h, can be achieved by means of a camera system K with a relatively small base width of 10 cm good depth resolutions up to a distance of about 500 m. This in turn is sufficient to reliably determine the visibility up to a distance of 300 m. Considering that a 150 km / h moving vehicle has a braking distance of about 150 m, this boundary conditions are given, which make it possible to warn the driver on the basis of a corresponding distance or visibility determination in time for hazards or the arrangement with a automatically engaging in the driving of the vehicle system to intervene and so far automatically respond to dangerous situations. In this case, the said base width b of about 10 cm for a corresponding camera system K in a motor vehicle 9 to realize without further ado. Similar conditions arise for a locomotive 9 whose braking distance is significantly greater than that of a motor vehicle. Assuming here a speed of 160 km / h and a braking distance of about 500 m, a camera distance or a base width b of 30 cm would be sufficient, on the basis of taking place according to the method according to the invention distance or visibility determination in time for any dangerous situations to be able to react.

An embodiment which is somewhat modified compared to the previously explained embodiment is characterized by FIG 8th given. The illustrated construction comes with a camera K ₁ , wherein for the realization of stereoscopic images instead of the second camera K _2, a deflection mirror 4 is provided, which is the image of its surroundings via a beam splitter 5 also the camera K ₁ feeds. A quasi stereoscopic Ab Education of the environment is achieved here by the fact that the camera K ₁ triggers either twice in a very short distance and on the one hand the imaged by the direct incident light environment and on the other hand via the deflection mirror 5 supplied image detected by means of its optical sensor. If the deflection mirror 5 and the beam splitter 6 allow the image of a field or field R on the optical sensor of the camera and it allows the memory card, but it is also possible to record two fields L, R simultaneously.

In a final embodiment, the distance determination for an object is to be explained, whose connecting line to the observer or camera system deviates from the horizontal. This is through the 9a and 9b exemplified for a cloud. According to the 9a can, for example, in the event that the cloud is approximately over the observer or over the camera system K at the location with the distance a from the object 3 which effectively removes l for a and Δx according to the equation l ≌ a + Δx cos φ (E7) be estimated. In all other cases, the determination of the effectively effective distance I is more difficult, but always remains a purely geometrically solvable problem. Always here is an angle measurement to determine the values of the angles φ and ϧ according to 9a necessary.

Opposite Radar and LIDAR methods but you can see exactly the photos, which Cloud actually was measured. A prior selection of the cloud may be made by the meteorologist done by screen. At strongly decreasing angles φ the Measurement is getting easier and closer the horizontal conditions more and more. Because the clouds are very move quickly and also change, is the synchronization of the cameras absolutely necessary. The fast change the cloud structure allows accurate measurements, taking the picture of a camera on a screen can be tracked, which allows a selection of the cloud and so advantages over other methods, such as LIDAR. The observing Meteorologist could so monitor on a screen the selection for the orientation of the cameras and trigger the recording. Also a continuous measurement and electronic records of Results do not pose any difficulties. Furthermore, also the Covering degree can be determined exactly. This procedure offers the Possibility, fast and accurate also the heights the clouds in different layers, which are also different Can move directions, to determine. Such a facility should include the determination of Visibility at meteorological stations much easier and compared to the contrast estimate a much higher one Have accuracy.

The 10 schematically shows the process in the evaluation of serving for distance measurement stereoscopic images. When using 4 cameras K ₁ , K ₂ K ₃ , K ₄ , the evaluation of all cameras K ₁ , K ₂ , K ₃ , K ₄ for determining the stereoscopic parallax p ₁ , p ₂ for the first and second image pickup position takes place simultaneously 1 . 2 when capturing the object 3 in a control and evaluation unit 10 , In the corresponding evaluation units 11 . 11 ' At the same time, the contrasts are evaluated. The different, for both image acquisition positions 1 . 2 resulting contrasts are in a comparison unit 12 compared to each other. The determined data and intermediate results are stored in the memory unit 13 filed and by the control unit 14 on a display 15 visualized for the driver. Optionally, one or the images of the cameras K ₁ , K ₂ K ₃ , K ₄ evaluated to determine the distance can be displayed in parallel by the driver on a separate screen 16 be followed. The control unit 14 provides a synchronization of the cameras K ₁ , K ₂ , K ₃ , K ₄ and a repeated measurement to each of the respective current situations statements on the removal of an object 3 or to be able to see.

list of used reference numerals

1, 2

Image capture position

3

object

4

deflecting

5

beamsplitter

6

ship With

7

bow

8th

Rear

9

vehicle (Car or locomotive locomotive)

10

Tax- and evaluation with

11 11 '

evaluation

12

processing unit

13

Storage

14

control unit

15

display

16

screen

a

distance

b

base width

B1, B2, B3, B4

images

K

Camera system with K ₁ to K ₄

l

effectively effective removal

p ₁ , p ₂

parallax

R L, R ', L'

fields (Panel systems)

.delta.t

time interval

v

speed

Ax

distance between image pickup positions

α, φ, ϧ

angle

Claims (17)

Method for determining the distance (a) of an object that differs from its surroundings due to differences in brightness and / or contrast ( 3 ), preferably in connection with a visibility determination, in which the distance determination is carried out by the evaluation of stereoscopic digital camera images consisting respectively of two partial images (R, L, R ', L'), which are provided by a camera system arranged stationarily or on a mobile unit ( K) are detected with cameras (K ₁ -K ₄ ), characterized in that the object ( 3 ) by means of the camera system (K) of two image acquisition positions which are different in the direction of the object and have a distance (Δx) from each other ( 1 . 2 ), for each of which two partial images (R, L, R ', L') of the recorded stereo images by evaluating brightness and / or contrast differences between adjacent image pixels are the same, the object ( 3 ) determined by counting the number of image pixels by which these image sections are shifted laterally from each other, and multiplying the determined pixel number with the known pixel size determines the existing between the image sections parallax (p ₁ , p ₂ ) and from the distance ( Δx) of both image pickup positions ( 1 . 2 ) and the parallaxes (p ₁ , p ₂ ), the distance (a) is calculated, wherein in particular with regard to the focal length (f) and the pixel number and size image sensors same cameras (K ₁ -K ₄ ) are used. Method according to claim 1, characterized in that that the visual evaluation, including the counting of the Pixel number, by which the respective two fields (R, L, R ', L') of the two stereoscopic Shots are shifted laterally against each other, and the calculation the distance (a), computer technology takes place. Method according to claim 1 or 2, characterized in that the distance is determined by the relationship

is determined, wherein the camera system (K) is selected so that the base width (b), namely the distance of the optical components for detecting the sub-images (R, L, R ', L') for the stereoscopic recordings constant and as well Distance (Δx) of the image pickup positions ( 1 . 2 ) is many times smaller than the distance (a) of the object to be determined ( 3 ), such that a >> b and a >> Δx as well as Δx >> b, and wherein the distance (Δx) between the two image pickup positions ( 1 . 2 ) is chosen so that, taking into account for the particular application of typical distances (a), neither p ₁ = p ₂ nor p ₁ >> p ₂ applies. Method according to one of claims 1 to 3, characterized in that starting from the, with respect to the image pickup positions ( 1 . 2 ) determined distance (a), based on an increasing distance from the object (a) 3 ), the visibility is determined, where appropriate, to obtain sufficient brightness and / or contrast differences, the distance in the same way at two other, from the image pickup positions ( 1 . 2 ) is determined again at different image positions. Method according to one of claims 1 to 4, characterized that the distance and / or the visibility in short time intervals repeatedly determined and averaged to improve accuracy. Arrangement for determining the distance (a) of an object which is distinguished from its environment by differences in brightness and / or contrast ( 3 ), preferably for determining the range of vision, with a stationary or mobile unit mounted camera system (K) for detecting stereoscopic image recordings, characterized in that the camera system (K) of two, in the direction of the object ( 3 ) with a known distance (.DELTA.x) spaced apart stereo image system with at least one camera (K ₁ , K ₂ , K ₃ , K ₄ ), the optical components for detecting the partial images (R, L, R ', L') for the stereoscopic images have the same base width (b) and their digital image recordings of a software and hardware-based control and evaluation unit ( 10 ) for calculating the parallaxes existing between the partial images (R, L, R ', L') of the stereoscopic images taken by the two stereo image systems and the distance (a) derivable therefrom and from the distance (Δx). Arrangement according to claim 6, characterized in that the cameras (K ₁ , K ₂ ) of the stereo image system for recording the stereoscopic image at the image pickup position ( 1 ) with the cameras (K ₃ , K ₄ ) of the stereo image system for capturing the stereoscopic image at the image pickup position ( 2 ) by the control and evaluation unit ( 10 ) so that the recording of the stereoscopic images at both image pickup positions ( 1 . 2 ) takes place at the same time. Arrangement for determining the distance (a) of an object which is distinguished from its environment by differences in brightness and / or contrast ( 3 ), preferably for determining the visibility, with a on a mobile unit, preferably a vehicle, arranged camera system (K) for detecting stereoscopic image recordings, characterized in that as a stereo image system with at least one camera (K ₁ ) formed camera system (K) controlled from a control and evaluation unit ( 10 ) within a time interval (Δt), in which the mobile unit traveled a distance (Δx) due to its movement speed, triggered twice, and the two stereo recordings of the control unit consisting of the sub-pictures (R, L, R ', L') and evaluation unit ( 10 ) for calculating the parallaxes existing between the sub-images (R, L, R ', L') and the distance (a) derivable therefrom and the distance (Δx). Arrangement according to one of claims 6 to 8, characterized in that the one or more stereo image systems only one camera (K ₁ , K ₃ ), while the respective other camera for receiving the second partial image (R, R ') by a deflection mirror ( 4 ) and a beam splitter ( 5 ), over which additionally the second partial image (R, R ') is mirrored into the camera (K ₁ , K ₃ ), the two partial images (R, L, R', L ') generating the respective stereo image, depending after equipment of the camera (K ₁ , K ₃ ) are evaluated by the image sensor at the same time or slightly offset in time. Arrangement according to one of claims 6 to 9, characterized that this is extended by an infrared unit, so that the Distance determination at night based on this unit detected infrared recordings takes place. Arrangement according to one of claims 6, 7 or 9, characterized in that it is on board a ship ( 6 ) is arranged, wherein at its bow ( 7 ) and stern ( 8th ) or on the bridge on one side, namely starboard or port side, cameras (K ₁ , K ₂ ) are arranged from each other with (Δx) spaced stereo imaging systems and wherein on the other side, namely, port or starboard side, Camera (K ₂ , K ₄ ) of the aforementioned stereo image systems or one respective camera (K ₂ , K ₄ ) replacing the deflection mirror, which is in each case combined with a beam splitter in front of the arranged on the other side camera (K ₁ , K ₂ ). Arrangement according to one of claims 8 to 10, characterized in that this on or in a motor vehicle ( 9 ), wherein the base width (b) of the camera system (K) is adapted to the space conditions of the installation or installation location, but is at least 6.5 cm. Arrangement according to claim 12, characterized that the camera system is part of a motor vehicle headlight is. Arrangement according to one of claims 8 to 10, characterized in that this at or in the power car ( 9 ) locomotive is arranged, wherein the base width (b) of the camera system (K) at least 30 cm. Arrangement according to one of Claims 6 to 14, characterized that this is a display for displaying the determined distance and / or Visibility includes. Arrangement according to one of Claims 6 to 15, characterized that this one extra Screen for immediate reproduction by means of the camera system (K) each captured images. Arrangement according to one of claims 6 to 16 for use in a land, water or air vehicle, characterized that with a for the automatic influencing of the vehicle behavior coupled security system, which is for removal or visibility gained values and in influencing of vehicle behavior.