DE4212066C2 - Method and device for determining the position of an optical line - Google Patents

Description

The invention relates to methods for determining the position different optical lines in one when setting and / or checking a headlamp with a video camera line by line image of one of the headlights illuminated area according to the preambles of the claims 1 to 3. Furthermore, the invention relates to devices for adjusting and / or checking a headlight under Determination of the position of an Isolux line, a line of focus the brightest spot of the headlight or a light-dark Headlight line according to the generic terms of the patent sayings 7 to 9.

The correct setting of a headlight is checked by optical Lines defined that illuminate on one of the headlights area can be found. With the low beam this is in Europe the so-called light-dark line, which is the case with Rechtsver turn from a horizontal and a right join the section that rises from left to right. For left-hand traffic like in Great Britain, the closes accordingly, the rising section increases to the left and also rises to the left. In the USA, on the other hand, is based on Low beam on so-called Isolux lines, i.e. on lines on which the area with the same light intensity from the headlight is illuminated. In the high beam is the so-called brightest spot, from an isolux line with little attenuation relative to the maximum light intensity of the headlight is limited, the basis of the standards. For precise adjustment or checking the headlights, the position of the optical Line that is of interest in the respective case is precisely determined and then be adjusted to a target position. This is with Isolux Lines impossible with the naked eye. But also with the light-dark The line and the brightest spot appear dull to the eye difficulties. This applies in particular when hiring Headlights in motor vehicle production. Here is the one too Eye strain due to the light intensity of the headlights  to consider. Accordingly, the location of the optical lines when adjusting and checking headlights finally recorded in terms of equipment, which also means automation of these operations is possible. Procedure for determining the position of optical lines can, however, be described above Area of application also used for other purposes become. So the location can be any, optically determine the defined line.

In a known method for determining the position of an optical Line when adjusting and checking a headlight the light of the headlight with a lens on a flat, Surface oriented perpendicular to the axis of the headlamp pictured. The area illuminated by the headlight is included a video camera recorded line by line that a video signal and outputs a pixel clock signal. The video signal is a sequence of line signals, each from a horizontal pulse be cited. A black is connected to the horizontal pulse shoulder to the zero value of the recorded brightness represents and which is followed by an active part of the image. The active one The proportion of the image is that of the video camera in one line recorded brightness again. The pixel clock signal is used for Assignment of the brightness to pixels within the line. The horizontal pulse, however, allows a column assignment. The Video signal is in addition to the division into line signals in two Fields divided, each by a vertical pulse and contain 312.5 line signals. In which known method, the video signal is in a matrix representation development of the recorded optical line contained Image transferred. This corresponds mathematically to the point by point Representation of a scalar field. The scalar field is last Lich the brightness on the illuminated by the headlight Area. For translating the video signal into the matrix display The video signal is digitized right at the start. All evaluation steps of the video signal take place with the known methods computer-aided digital. When determining  In the position of the light-dark line, the points are searched for where the magnitude of the gradient of the scalar field is its maximum having. To determine the position of an Isolux line, the first is Maximum of the scalar field determined and then after the points the attenuation corresponding to the Isolux line. At the determination of the position of the brightest spot also becomes Maximum of the scalar field determined and then the area sought within which the brightness is only a certain Attenuation value lags behind the peak value. Man is given an Isolux surface, the focus of which is the location of the brightest spot. The known method has the disadvantage that an enormous amount of computing work is required to carry it out is. Even with a relatively large amount of computing and Combining multiple matrix points is still a process Processing the video signal in real time hardly feasible. This is particularly difficult when adjusting a headlight, since the result of adjusting the headlight is not can be seen immediately. Known devices for performing the Procedures are therefore either inadequate or extremely expensive playful.

DE-OS 29 46 561 describes methods according to the generic terms of claims 1 to 3 and devices for performing this method according to the preambles of claims 8 to 10. Nominally, the document deals with the determination of the Location of the high beam maximum, d. H. the brightest spot, and the light-dark line generated by the headlight. Each will Line signal with an ascending sequence of fixed references compared values. This way the location is the brightest Stains or the light-dark line itself, however, cannot be determined. Rather, the fixed reference values correspond to certain Isolux Lines of the pig thrower. These Isolux lines are related to the maximum light intensity of the respective headlight in none Relationship. The result is from DE-OS 29 46 561 known methods and devices exclusively one line by line digitization of the recorded by the video camera  reached the picture, the fixed reference values being the digita Specify levels of

The digitization of lines with a video camera pictures taken is also from DE-OS 26 37 485 and US-PS 46 09 939 known. Here is the digitization of the picture provided in three or two fixed stages.

From DE-OS 34 39 540 a method is known in which the Maxima of the second derivatives of the individual line signals in one when adjusting and / or checking a headlight image taken line by line with a video camera one of the area illuminated by the headlight can be determined.

From EP-OS 0132 372 a method is known in which the Position of the brightest spot in the illumination image of any one Headlamp is determined based on an area comparison. Of the Alignment is between those delimited by an Isolux line Surface made in the lighting image and a reference surface. The area adjustment variable corresponds to that of the Isolux line appropriate reference value. This reference value is based on the current Adapted headlights. It has no relation to that Peak light intensity of the headlamp.

The invention has for its object the method according to the Preambles of claims 1 to 3 and the devices according to the preambles of claims 7 to 9 to further develop that the location of those of interest optical lines can be determined in real time and that for the Determination of the apparatus expenditure to be operated is as low as possible is.  

In the process, the task is characterized by the characteristics of Claims 1 to 3 solved.

In the new, analogous process is as Reference value the previous peak value is used. This happens under the assumption that the peak value at line-by-line determination from line to line (claim 3) or when determining frame by frame from frame to frame or field Field (claims 1 and 2) does not change significantly.

The peak value is in the process according to the patent claims 1 and 2 the peak value of the rectified line signals of the entire image or a field. When determining the position an Isolux line or the center of gravity of the brightest spot must be the maximum brightness on that of the headlight illuminated area can be determined. It is sufficient to do this Field of the video signal to be considered. To visit An Isolux line has to determine the point at which the Brightness in a row the corresponding percentage of the maximum brightness reached.

The rectified line signal is used in determining the Position of the light-dark line differentiated according to claim 3, where the peak is the peak derivative of the row signals. The peak derivative of the line signal marks the crossing point between the corresponding line and a light-dark line. The execution described here The form of the procedure is therefore based on the European standard Low beam tuned. It is understood that the crossing point, d. H. the position of the peak value in the row under consideration is determined by averaging.

To in the process according to claims 2 and 3 within the position of the peak value on a line, if this is the one sought Crossing point corresponds to the optical line  a special measure is required. It is not too sufficient to trust that with each line signal the previous peak is actually reached. Furthermore must be reckoned with several local maxima, which around the Scatter the actual location of the intersection. In which The new procedure therefore takes the location of the peak value from the Average of the first exceedance of the weakened previous peak value and the location of the following Falling below the weakened previous peak determined. To do this, the pixel clock signal is between the two Events switched to half the frequency.

The steps are determining, caching and Attenuation of the peak value and comparison of the line signal with the previous peak value completely analog feasible while the counter is digitally added up and a digital status of the meter is saved. This state of the Incidentally, the counter is the only information that comes from everyone Line of the camera needed to determine the position of the optical line and therefore with a subsequent, computer-aided evaluation step must be taken into account. So that reduces amount of data to be managed digitally already to one value per Row. In addition, the remaining digital data is required no time-consuming analysis. Rather, they are just too smooth and possibly compare with a target. On this is an orientation of the attitude and / or Control of a headlight-interested optical lines possible in real time with little expenditure on equipment.

The line signal can be displayed before the peak value is determined its black level clamped and rectified. On in this way the line signal is normalized and set to the active one Image portion reduced, which is advantageously also completely analog is feasible.  

The video camera is advantageously aligned so that it Records lines from top to bottom. So it is enough with that The method according to claim 1 usually consists of the first Reaching the weakened peak value to save because Adjustment of headlights according to the US standard only knowledge the location of the first Isolux line you are looking for from above is. With the new method, however, everyone can Crossing points of the Isolux line searched for with the respective one Line can be determined.

The video camera can be aligned so that the lines Cross the optical line you are looking for at right angles. On this way, maximum reliability in detection reached the crossing points. But also a parallel to that Rows of the video camera section of the optical Line is understandable insofar as it does not have any Has intersection points with the lines.

The picture can also be taken with a second video camera whose lines are orthogonal to the lines of the first Video camera are aligned. With two video cameras, their Rows are arranged orthogonally to one another is certain represents that the optical line regardless of its course the Lines of at least one video camera crosses at an angle <45 °. So it is possible to determine the location of each optical line that occurs to determine reliably.

In the devices, the object of the invention is achieved solved the features of claims 7 to 9. The electro African components of these devices are the simplest type and to provide at extremely low cost.

For determining the position of a light-dark line according to claim 1 is in the analog branch of the upstream of the computer  Electronics additionally provide a differentiator. This can be designed in the simplest way as an RC element.

The switch for the pixel clock signal at half frequency is always necessary when the location of the peak value in the line under consideration. This also applies to the Determination of the position of the brightest spot, for which none Differentiator is used.

The attenuator is advantageous as a digital one Input value depending on a reference voltage in a converting analog output value from digital / analog converter forms, the previous peak value being the reference voltage and the analog output value is the attenuated peak. The degree of weakening can thus be determined via the digital input value of the attenuator can be specified with the digital computer.

The analog components allow that for the last digital Evaluation step a relatively slower and therefore also inexpensive computer is used without the Real-time claim is violated.

A first input of the comparator on the one hand and the tip value detector, the buffer, the attenuator and a second input of the comparator, on the other hand, can be an analog Circuit for black level clamping and an analogue equal be upstream. These components are also inexpensive to provide and for the evaluation of the video signals in real time.

The invention is based on three execution examples explained and described in more detail. It shows:

Fig. 1 shows an arrangement for adjusting a headlamp

Fig. 2 different U (t) diagrams for the construction of a video signal,

Fig. 3 shows the schematic structure of an apparatus for performing a first embodiment of the method,

Fig. 4 shows the relative position of the different pulses in the embodiment of the method according to Fig. 3,

Fig. 5, the basic principle to the embodiment of the method according to Fig. 3,

Fig. 6 shows the schematic structure of an apparatus for carrying out a second embodiment of the method,

Fig. 7 shows the basic principle of the embodiment of the method of Fig. 6,

Fig. 8 shows the schematic structure of an apparatus for carrying out a third embodiment of the method,

Fig. 9, the relative position of various pulses in the embodiment of the method according to FIG. 8,

Fig. 10 shows the basic principle of the embodiment of the method according to Fig. 8.

In Fig. 1, an arrangement is shown, a headlight 32 is determined based on the position of an optical characteristic line 33 on an illuminated by the headlight 32 in the surface 34 normally alignment. The optical line 33 can be used to adjust and / or control the alignment of the headlight 32 . To reduce the space required, a converging lens 35 is arranged in front of the headlight 32 . The converging lens 35 also leads to an extensive invariance of the position of the optical line 33 with respect to parallel displacements of the headlamp 32 relative to the optical axis of the converging lens 35 . To determine the position of the optical line 33 , the surface 34 illuminated by the headlight 32 is recorded with a video camera 11 . The video camera 11 outputs a video signal 1 and a pixel clock signal 12 . To carry out the new method, the video camera 11 is oriented upright, contrary to the usual arrangement, so that its lines 36 projected onto the surface 34 cross the optical line 33 .

In Fig. 2, the structure or more precisely the subdivision of the video signal 1 output by the video camera 11 represents Darge. Fig. 2a shows that the video signal 1 is divided into fields 2 , 3 . Each field is led by a vertical pulse 4 and has a duration of 20 ms. Each field 2 , 3 contains 312.5 line signals 5 , the structure of which is shown in FIG. 2b. An entire image 6 is composed of two fields 2 and 3 and a total of 625 line signals. Here, the first field comprises the first, third, fifth, etc. line of the video camera, while the remaining lines are assigned to the second field 3 . Each field 2 , 3 thus contains information from the entire area of the image 6 . Each line signal 5 is led by a horizontal pulse 7 and has a duration of 64 microseconds. The superposition of the line signals 5 with the fields 2 , 3 is shown for the field 2 in FIG. 2c. However, only the first of the 312 horizontal pulses 7 are shown here. The actual shape of a line signal 5 is shown in FIG. 2d. The horizontal pulse 7 is followed by the black shoulder 8 , which represents the zero value of the brightnesses recorded by the video camera, the so-called black value. An active image portion 9 of the line signal 5 carries the actual error information about the brightnesses read in by the video camera in the corresponding line. Here, the amplitude of the line signal 5 at a specific point in time is a measure of the brightness of the image recorded by the video camera at a specific location.

The device 10 partially shown in FIG. 3 for setting and / or checking a headlamp has the video camera 11 , which records the surface 34 illuminated by the headlamp according to FIG. 1 line by line. The video camera 11 outputs the video signal 1 and the pixel clock signal 12 . The pixel clock signal 12 is summed up by a counter 13 . The counter 13 is zeroed and started depending on the video signal 1 . The video signal 1 is simultaneously applied to a circuit 14 for black level clamping. The circuit 14 sets the black shoulder 8 of the line signals 5 to zero. The video signal 1 then passes through a rectifier 15 . The rectifier 15 reduces the video signal 1 due to the black level clamping to the active image portion 9 of the respective line signal 5 . Following the rectifier 15 , the video signal 1 is given on the one hand on a first input of a comparator 16 and on the other hand on a peak value detector 17 for. At the output of the peak value detector 17 , a buffer 18 is arranged, which holds the previous peak value. The previous peak value is attenuated by an attenuator 19 by a predetermined percentage. The attenuated, previous peak value is given as a reference value to a second input of the comparator 16 . The video signal 1 in turn serves to control the peak value detector 17 and the buffer store 18 . The output signal of the comparator 16 , however, triggers the storage of the status of the counter 13 in a memory 20 . The circuit 14 , the rectifier 15 , the comparator 16 , the peak value detector 17 , the buffer memory 18 , the attenuator 19 , the counter 13 and the memory 20 form an electronic circuit which is connected upstream of a computer 20 reading the memory 20 within an evaluation unit for the video signal 1 is. In electronics, all components except for the comparator 16 , the counter 13 and the memory 20 are designed analogously. This enables problem-free operation of the evaluation unit in real time and its cost-effective provision.

The details of the processing of the video signal 1 in the evaluation unit will now be explained in more detail with reference to FIGS. 4 and 5. FIG. 4 shows how the peak value detector 17 and the buffer store 18 according to FIG. 3 are controlled with the video signal 1 . The representation of the composite video signal 1 in FIG. 4a corresponds to that in FIG. 2c. The vertical pulse 4 shown separately in FIG. 4b at the beginning of the field 2 is used to trigger the subsequent pulses 21 , 22 . The first subsequent pulse 21 shown in FIG. 4c allows the intermediate memory 18 to take over the peak value from the peak value detector 17 . This peak value corresponds to the field preceding field 2 . The subsequent pulse 22 shown in FIG. 4d then resets the peak value detector 17 so that it can determine the peak value of the field 2 . In this way, the peak value of the previous field, which corresponds to the maximum brightness recorded by the video camera 11 , is always present in the buffer memory 18 . The current amplitude of the respective line signal 5 is hereby compared. This is shown in detail in FIG. 5. Fig. 5a shows the line signal 5 as emitted by the camera 11. Fig. 5b are in contrast, the rectified and reduced to its active picture portion signal line 5 again. The amplitude of the rectified line signal is now compared in comparator 16 with the reference value, the attenuated, previous peak value. It is assumed that the peak value of the previous field corresponds to the peak value of the current field. If the amplitude of the line signal 5 is compared with the previous peak value which has been weakened by 25%, this corresponds to the search for a 75% isolux line or its crossing point with the line of the video camera 11 currently being evaluated. The peak value of the previous field which has weakened to 75% is given as threshold 23 in FIG. 5b. When the threshold 23 is exceeded by the line signal 5 , the output signal 24 of the comparator 16 shown in FIG. 5c is raised. The rising edge 27 triggers a storage of the status of the counter 13 by the memory 20 . The counter 13 sums the pixel clock signal 12 shown in FIG. 5d. The counter 13 was zeroed and started by the horizontal pulse 7 at the beginning of the line signal 5 . Thus, the status of the counter 13 stored in the memory 20 is a measure of the position of the isolux line sought in the corresponding line of the video camera. The line of the video camera crosses the Isolux line a second time when the line signal 5 falls below the threshold 23 . With the falling edge 28 of the output signal 24 , a second state of the counter 13 could be stored in the memory 20 in order to also record the second crossing point of the Isolux line and the line of the video camera. As a rule, however, the determination of the first crossing point is sufficient for the adjustment and / or control of the headlamp.

Fig. 6 shows the device 10 in a second embodiment, the representation corresponding to FIG. 3. In addition, a switch 25 and a divider by two 26 are provided. The changeover switch 25 is connected upstream of the counter 13, and outputs the pixel clock signal 12 with either their simple frequency or with a halved by the divider by two 26 frequency to the counter. 13 The switch 25 is controlled by the video signal 1 on the one hand and the output signal 24 of the comparator 26 on the other.

The mode of operation of the device 10 according to FIG. 6 results from FIG. 7. It should be taken into account here that the peak value detector 17 and the buffer memory 18 are controlled by the video signal 1 analogously to the embodiment according to FIG. 3. Accordingly, the rectified line signal 5 according to FIG. 7b is compared in the comparator 16 with the threshold 23 . Here, the rising edge 27 of the output signal 24 now triggers not the storage of the state of the memory 13 , but the switch 25 , which then gives the pixel clock signal 12 , which is halved in frequency by the divider-by-two 26, to the counter 13 . Only the falling edge 28 allows the memory 20 to read the status of the memory 13 . In this way, the state of the counter 13 stored in the memory 20 corresponds to the central position of the entry point and the exit point of the corresponding line of the video camera in the brightest spot on the surface 34 illuminated by the headlight 32 . This corresponds with sufficient accuracy to the position of the brightest spot in this line. The pixel clock signal 12 is advantageously reset to the simple frequency simultaneously with the zeroing and starting of the counter 13 by the horizontal pulse 7 .

The embodiment of the device 10 shown in FIG. 8 also has, in addition to the embodiment according to FIG. 6, a differentiator 29 which is connected downstream of the rectifier 15 and is connected upstream of the peak value detector 17 or the comparator 16 . In addition, the peak value detector 17 and the buffer store 18 are controlled by the video signal 1 in a modified form. This is shown in Fig. 9. Instead of the subsequent pulse 21 triggered by the vertical pulse 4 , the buffer memory 18 is prompted by each horizontal pulse 7 to take over the peak value from the determiner 17 . The determiner 17 is then reset by a subsequent pulse 30 triggered by the horizontal pulse 7 . In this way, the buffer 18 always contains the peak value of the derivative of the line signal preceding the current line signal 5 .

FIG. 10 shows the influence of the differentiating element 29 on the mode of operation of the device 10 according to FIG. 8. The derivative 31 of the line signal 5 is shown in FIG. 10b. The position of the peak value of the derivative 31 is obtained analogously to the location of the brightest spot according to FIG. 7 by averaging. The peak value of the derivative is characteristic of the light-dark line, which is the basis of the European standard for the adjustment of the low beam of the headlamp.

The particular advantage in carrying out the new method, in particular with the aid of the new device, is the possibility of processing the video signal 1 in real time. For example, this opens up new perspectives in the automation of headlight adjustment. It is also advantageous that the simplest analog components are used in the new device. For example, a simple diode is suitable as a rectifier 15 , a common voltage divider composed of two resistors as an attenuator 19 and a conventional RC element as a differentiator 29 .

Reference list

1

- video signal

2nd

- field

3rd

- field

4th

- vertical pulse

5

- line signal

6

- Image

7

- horizontal pulse

8th

- Black shoulder

9

- active part of the image

10th

- Contraption

11

- video camera

12th

- Pixel clock signal

13

- Counter

14

- circuit

15

- rectifier

16

- comparator

17th

- investigators

18th

- cache

19th

- reducer

20th

- Storage

21

- Follow impulse

22

- Follow impulse

23

- threshold

24th

- output signal

25th

- switch

26

- Divide by two

27

- rising edge

28

- falling edge

29

- differentiator

30th

- Follow impulse

31

- derivative

32

- headlights

33

- optical line

34

- Surface

35

- converging lens

36

- Row

Claims (12)

1. A method for determining the position of an optical line in an image taken line-by-line during the adjustment and / or control of a headlight with a video camera of an area illuminated by the headlight, the video camera emitting a video signal and a pixel clock signal being oriented so that its lines cross the optical line, with each line signal of the video signal being evaluated individually, with a horizontal pulse at the beginning of the line signal zeroing and starting a counter summing up the pixel clock signal, the line signal being compared with a reference value and the state of the counter at the time when the line signal exceeds the reference value, and / or is stored at the time when the line signal falls below the reference value, so that a digital representation of the position of the optical line in the image is determined from the video signal, the optical line being an isolux -Line of the Scheinw erfers corresponds, characterized in that the peak value of all line signals ( 5 ) belonging to the respective image ( 6 ) or field ( 2 , 3 ) is determined and buffered, and that the respective reference value ( 23 ) is the peak value weakened by a predetermined fixed percentage of all line signals ( 5 ) belonging to the previous image ( 6 ) or field ( 2 , 3 ). 2. A method for determining the position of an optical line in an image taken line by line during the adjustment and / or control of a headlight with a video camera of an area illuminated by the headlight, the video camera emitting a video signal and a pixel clock signal being oriented so that its lines cross the optical line, each line signal of the video signal being evaluated individually, a horizontal pulse at the beginning of the line signal zeroing and starting a counter which adds up the pixel clock signal, the line signal being compared with a reference value and the status of the counter being stored at the time, in which the line signal falls below the reference value, so that a digital representation of the position of the optical line in the image is determined from the video signal, characterized in that the peak value of all belonging to the respective image (6) or field ( 2 , 3 ) Determine line signals ( 5 ) It is stored and temporarily stored that the respective reference value ( 23 ) is the peak value of all line signals ( 5 ) belonging to the previous picture ( 6 ) or field ( 2 , 3 ), which has been weakened by a predetermined, fixed percentage, that the pixel clock signal ( 12 ) is switched to half frequency when the respective line signal exceeds the reference value ( 23 ), that the status of the counter ( 13 ) is stored when the respective line signal then falls below the reference value ( 23 ), and that the pixel clock signal ( 12 ) at the latest the next horizontal pulse ( 7 ) is switched back to full frequency so that the optical line corresponds to a center of gravity line of the brightest spot of the headlight ( 32 ). 3. A method for determining the position of an optical line in an image taken line by line during the adjustment and / or control of a headlight with a video camera of an area illuminated by the headlight, the video camera emitting a video signal and a pixel clock signal being oriented so that its lines cross the optical line, each line signal of the video signal being evaluated individually, a horizontal pulse at the beginning of the line signal zeroing and starting a counter which adds up the pixel clock signal, the line signal being compared with a reference value and the status of the counter being stored at the time, in which the line signal exceeds the reference value, so that a digital representation of the position of the optical line in the image is determined from the video signal, characterized in that the peak value of the derivative ( 31 ) of the respective line signal ( 5 ) is determined and buffered, that the respective reference value ( 23 ) is the peak value of the derivative ( 31 ) of the preceding line signal ( 5 ) which has been weakened by a predetermined fixed percentage, that the pixel clock signal ( 12 ) is switched to half the frequency when the respective line signal ( 5 ) with its derivative ( 31 ) exceeds the reference value ( 23 ), that the status of the counter ( 13 ) is stored when the respective line signal ( 5 ) with its derivative ( 31 ) then falls below the reference value ( 23 ), and that the pixel clock signal ( 12 ) is switched back to full frequency at the latest with the next horizontal pulse, so that the optical line corresponds to the light-dark line of the headlight ( 32 ). 4. The method according to any one of claims 1 to 3, characterized in that the line signal ( 5 ) is clamped to its black level and rectified before the determination of the peak value. 5. The method according to any one of claims 1 to 4, characterized in that the video camera ( 11 ) is aligned so that the lines ( 36 ) cross the sought optical line ( 33 ) as right as possible. 6. The method according to any one of claims 1 to 4, characterized in that the image is additionally recorded with a second video camera, the lines of which are aligned orthogonally to the lines of the first video camera ( 11 ). 7. A device for setting and / or checking a headlamp by determining the position of an Isolux line according to claim 1, with a line ( 33 ) illuminated by the headlamp ( 32 ) receiving line by line, a video signal ( 1 ) and a pixel clock signal ( 12 ) donating video camera (11) and a one pixel clock signal (12) summing counter (13), a comparator (16) and a digital memory (20) for the reading of the counter (13) having evaluation unit for the line signals (5) of the video signal ( 1 ), wherein the comparator ( 16 ) triggers the storage of the status of the counter ( 13 ), characterized in that the evaluation unit furthermore has an analog peak value detector ( 17 ) for the peak value of all of the respective image ( 6 ) or field ( 2 , 3 ) associated line signals ( 5 ) and an analog buffer ( 18 ) and an analog attenuator ( 19 ) for the peak value of all to the previous image ( 6 ) or field ( 2 , 3 ) belonging line signals ( 5 ), the comparator ( 16 ) for the comparison of the respective line signal ( 5 ) with the attenuated by a predetermined, fixed percentage and temporarily stored peak value of all of the previous one Picture ( 6 ) or field ( 2 , 3 ) belonging line signals ( 5 ) is provided. 8. Device for setting and / or checking a headlight by determining the position of a center of gravity line of the brightest spot of the headlight ( 32 ) according to claim 2, with a line ( 33 ) illuminated by the headlight ( 32 ) receiving line by line, a video signal ( 1 ) and a pixel clock signal (12) dissipating video camera (11) and a one pixel clock signal (12) summing counter (13), a Kompara tor (16) and a digital memory (20) for the reading of the counter (13) having evaluation unit for the line signals ( 5 ) of the video signal ( 1 ), wherein the comparator ( 16 ) triggers the storage of the state of the counter ( 13 ), characterized in that the evaluation unit also has an analog peak value detector ( 17 ) for the peak value of all the respective image ( 6 ) or field ( 2 , 3 ) belonging line signals ( 5 ), an analog buffer ( 18 ), and an analog attenuator ( 19 ) for r has the peak value of all line signals ( 5 ) belonging to the previous image ( 6 ) or field ( 2 , 3 ) and a switch ( 25 ) for the pixel clock signal ( 12 ) at half frequency, the comparator ( 16 ) for the comparison of the respective line signal ( 5 ) with the peak value of all line signals ( 5 ) belonging to the previous picture ( 6 ) or field ( 2 , 3 ) which is weakened by a predetermined, fixed percentage and temporarily stored and before the status of the counter ( 13 ) operated the switch ( 25 ) for the pixel clock signal ( 13 ) at half the frequency. 9. A device for adjusting and / or checking a headlight by determining the position of a light-dark line of the headlight ( 32 ) according to claim 3, with a line ( 33 ) illuminated by the headlight ( 32 ) line by line, a video signal ( 1 ) and a pixel clock signal ( 12 ) emitting video camera ( 11 ) and a counter ( 13 ) summing up the pixel clock signal ( 12 ), a comparator ( 16 ) and a digital memory ( 20 ) for the status of the counter ( 13 ) Evaluation unit for the line signals ( 5 ) of the video signal ( 1 ), the comparator ( 16 ) triggering the storage of the status of the counter ( 13 ), characterized in that the evaluation unit also has an analog differentiator ( 29 ) and an analog peak value detector ( 17 ) for the peak value of the differentiated line signal ( 31 ), an analog buffer ( 18 ) and an analog attenuator ( 19 ) for the peak value of the the previous differentiated line signal ( 31 ) and a switch ( 25 ) for the pixel clock signal ( 12 ) at half the frequency, the comparator ( 16 ) for comparing the respective line signal ( 5 ) with the attenuated and temporarily stored peak value of the previous differentiated line signal ( 31 ) is provided and, before storing the status of the counter ( 13 ), the switch ( 25 ) for the pixel clock signal ( 12 ) is operated at half the frequency. 10. The device according to claim 7 or 8, characterized in that in the evaluation unit an analog circuit ( 14 ) for black level clamping and an analog rectifier ( 15 ) for the line signals ( 5 ) of the video signal ( 1 ) a first input of the comparator ( 16 ) on the one hand and the peak value detector ( 17 ), the buffer ( 18 ), the attenuator ( 19 ) and a second input of the comparator ( 16 ) on the other hand. 11. The device according to claim 9, characterized in that in the evaluation unit an analog circuit ( 14 ) for black level clamping and an analog rectifier ( 15 ) for the line signals ( 5 ) are connected upstream of the differentiator ( 29 ). 12. The apparatus of claim 9 or 11, characterized in that the analog differentiator ( 29 ) is an RC element.