Method and device for displaying traffic information and for capturing traffic information and variable message signs displayed by a traffic sign

Abstract

Method (200) for displaying traffic information using a display area (116) of a variable message sign (100), wherein the method (200) comprises the following step: Selecting image information corresponding to the traffic information and selecting optical code information corresponding to the traffic information; Generating at least one display signal for controlling luminaires of the display area (116), wherein the luminaires can be controlled by the display signal in such a way that both an image (118) displaying the image information and an optical code (120) representing the optical code information are displayed; and Providing (204) the at least one display signal to an interface to the display area (104) of the variable message sign (100) in order to display the traffic information as the image (118) pulsed with a pulse frequency on the display area (104) of the variable message sign (100) for a viewer and to display the optical code (120) which includes an information content of the traffic information in coded form on the display area (104) for an image capture device (112).

Description

State of the art

[0001] The present invention relates to a method for displaying traffic information, to a corresponding device, to a method for detecting traffic information displayed by a traffic sign and to a corresponding device and to a variable message sign and to a computer program product.

[0002] Automated recognition of traffic signs and, for example, providing a warning of speeding can be a safety benefit for a vehicle driver.

[0003] DE 10 2010 062 633 A1 describes a method and a device for detecting traffic signs in the surroundings of a vehicle and comparing them with traffic sign information from a digital map.

[0004] DE 10 2005 012 984 A1 discloses a device for transmitting data in road traffic, which comprises a transmitting device with means for emitting light and a receiving device with means for detecting light. For example, traffic information beyond that visible on traffic signs can be transmitted via light-emitting diodes.

[0005] DE 10 2005 061 786 A1 discloses a method for transmitting information at a traffic light system. At least one signal lamp is controlled, and the signals of the signal lamp are modulated according to a first coding to transmit coded light signals independent of the displayed system status of the traffic light system. The signals according to the first coding each carry additional information modulated according to a second coding. Disclosure of the invention

[0006] Against this background, the present invention presents a method for displaying traffic information, a device for displaying traffic information, a method for detecting traffic information displayed by a traffic sign, a device for detecting traffic information displayed by a traffic sign, a variable message sign, and finally a corresponding computer program product according to the main claims. Advantageous embodiments emerge from the respective subclaims and the following description.

[0007] A variable message sign can be used to display traffic information, such as a traffic sign or information text. To ensure that the traffic information can be reliably recognized, for example, by a vehicle's image capture device, the traffic information can be presented in coded form in addition to a visual display that is recognizable to the viewer. In this coded form, the traffic information can be presented in such a way that it can be reliably captured by the image capture device. Code information from the optical code can, for example, be displayed separately from the visual display or superimposed on the visual display.

[0008] A method for displaying traffic information comprises the following step: Providing at least one display signal at an interface to a display surface of a variable message sign in order to display the traffic information as an image pulsed at a pulse frequency on the display surface of the variable message sign for a viewer and to display an optical code comprising an information content of the traffic information in coded form on the display surface for an image capture device.

[0009] Traffic information can be a traffic sign and, alternatively or additionally, information text, a pictogram, or similar. The traffic information can be displayed in multiple colors. In particular, the traffic information can be displayed in red and white on a black background. A variable message sign can be a display device for displaying the traffic sign. Different traffic signs can be displayed one after the other. The display surface of the variable message sign can have a plurality of light sources. The light sources can be controlled separately to display the traffic sign and the optical code. Depending on the design, the light sources can, for example, be switched on and off separately, their brightness can be changed, or their pulse frequency can be varied.A light source can represent a pixel of the image or the optical code, or it can represent a pixel of both the image and the optical code. The light sources can be designed as light-emitting diodes, for example. The light sources used to display the image can be operated in a pulsed manner according to the pulse frequency. A display signal can be designed to control one or more light sources. For this purpose, the display signal can comprise or transmit control information for controlling one or more light sources. An optical code can comprise at least one pixel. Using the optical code, a plurality of different pieces of traffic information can be displayed in coded form. Each piece of traffic information can be assigned its own code. By decoding a detected optical code, the traffic information represented by the optical code can be determined.Decoding can be carried out automatically by a suitable decoding device. The optical code can be displayed in such a way that it is not recognizable to the viewer or is inconspicuous in relation to the image. The image capture device can be part of a vehicle. The image capture device can be a camera, for example a video camera. The optical code can be detectable by the image capture device if it is completely imaged in at least one shot of an image sequence captured by the image capture device. For example, the optical code can be displayed over a period of time that is adapted to a frame rate of the image capture device, such that the image capture device can capture the optical code in at least one shot. Advantageously, the optical code can be displayed for a length of time that allows it to be imaged in multiple shots of the image sequence.

[0010] The at least one display signal can be configured to display the image simultaneously with the optical code. In this way, the traffic information can be captured simultaneously by the viewer and the image capture device.

[0011] The at least one display signal can be designed to display the optical code in a code area for displaying the code, which is arranged separately from an image area for displaying the image. In a code area, the code can be recognized particularly easily by the image capture device. Overlaying of information from the displayed image and information from the displayed code can be avoided. For example, the display surface can comprise a first display surface for displaying the image and a second display surface for displaying the optical code. The two display surfaces can be arranged spatially spaced from one another. Each of the display surfaces can have at least one light source that can be controlled by the at least one display signal.

[0012] The at least one display signal can be designed to display the optical code in the area of ​​the image. For example, individual pixels of the image or groups of pixels can have brightness times long enough for the image capture device to reliably capture the pixels in at least one image. The pixels can also light up in addition to or separately from the pixels of the image. The viewer will most likely not notice the pixels of the code because a large majority of the pixels of the image display traffic information as usual. The pixels or groups can have the brightness times in a predetermined chronological sequence. The chronological sequence can represent further coded information. Thus, a light source used to display the image can also be used to display the optical code.At least one light source for displaying the optical code can also be arranged within an array of light sources for displaying the image. This can save space.

[0013] The at least one display signal can be configured to display the optical code using a graphic pattern. A graphic pattern can consist of at least two pixels or groups of pixels arranged in a spatial relationship to one another. The pattern can be displayed at a delivery frequency that differs from the pulse frequency, or it can be displayed without pulses. The graphic pattern can, for example, represent a data word associated with the traffic information. For example, four pixels or groups can transmit sixteen data words. The pattern can also be superimposed on the traffic information image.

[0014] The method can comprise a step of selecting the pulse frequency as a function of the traffic information, wherein the at least one display signal is designed to represent the optical code using the pulse frequency. A first piece of traffic information, for example an overtaking ban, can be assigned a first pulse frequency. A second piece of traffic information, for example a speed limit, can be assigned a second pulse frequency. The second pulse frequency can be lower than the first pulse frequency, for example. A third piece of traffic information, for example a traffic jam warning, can be assigned a third pulse frequency. For example, the third pulse frequency can be higher than the first pulse frequency. The image capture device can determine the pulse frequency. The associated traffic information can be assigned to the determined pulse frequency and thus recognized.The pulse frequencies can be higher than the upper cutoff frequency of the human eye. Thus, the pulse frequencies may be imperceptible to the human eye.

[0015] The at least one display signal can be designed to display the optical code using a brightness ratio between a first region of the image and at least one second region of the image. The first region and the at least one second region can be displayed in a way that is detectable by the image capture device. For example, the first region and the second region can be controlled with a continuous signal without a pulse frequency. A brightness ratio can, for example, be a percentage ratio of a first brightness of the first region to a brightness of the second region. A specific piece of traffic information can be assigned to each brightness ratio. This means that a large variety of information can be transmitted using a small number of pixels or groups, since the number of brightness levels is only limited by the resolution of the image capture device.For example, the brighter area can always represent a value of 100 percent or one. The darker area can have a proportional brightness. The first area, the second area, and at least one other area can be arranged in a pattern. This allows a much higher information content to be transmitted than with just two brightness levels.

[0016] The at least one display signal can be configured to represent the optical code using pulse width modulation of the pulse frequency. For this purpose, for example, a bright period can be extended by a certain amount, with a subsequent bright period being shortened by the same amount. As a result, the average value of the emitted light quantity remains the same. The human eye cannot perceive any difference in brightness, while the image capture device can recognize the image during the extended bright period. Likewise, the code area can be controlled with its own code frequency, with a ratio of a bright period of the code area to a dark period of the code area transmitting the traffic information in coded form.

[0017] The method may include a step of displaying the traffic information as the image pulsed at the pulse frequency on the display surface of the variable message sign and displaying the optical code on the display surface. The optical code and the image may be displayed using the at least one display signal and at least one light source controlled by the at least one display signal.

[0018] For example, the at least one display signal can be configured to control a first light source of the display surface for displaying the image and a second light source of the display surface for displaying the optical code. Alternatively, the at least one display signal can be configured to control one and the same light source for displaying the image and for displaying the optical code.

[0019] A method for detecting traffic information displayed by a traffic sign comprises the following steps: Reading in information via an optical code, which comprises an information content of the traffic information in coded form and is displayed on a display surface of a variable message sign in the form of a traffic sign, via an interface to an image capture device; and Evaluating the information via the optical code to capture the traffic information.

[0020] The image capture device can have a predetermined image frequency or sampling frequency. The sampling frequency can be similar to the pulse frequency of the variable message sign. Due to this similarity, the traffic information displayed as an image on the display surface can be only partially captured or not captured at all, since the time of image capture can be offset from the time of display on the display surface. The optical code, on the other hand, can be represented in such a way that it can be reliably captured completely in at least one image captured by the image capture device. The captured optical code can be evaluated, for example, using stored reference codes, each of which is assigned to a piece of traffic sign information.

[0021] The method may include a step of reading in information via an image. The image may visually display the or further traffic information on the or another traffic sign for a viewer. The image may be read in via the interface to the image capture device. The method may include a step of evaluating the information via the image in order to capture the or further traffic information. In this way, the image capture device can also be used to capture visually displayed traffic information that is not presented in parallel using an optical code.

[0022] Furthermore, a device for displaying traffic information is presented, the device having the following feature: a device for providing at least one display signal at an interface to a display surface of a variable message sign in order to display the traffic information as an image pulsed at a pulse frequency on the display surface of the variable message sign for a viewer and to display an optical code comprising an information content of the traffic information in coded form on the display surface for an image capture device.

[0023] A device for detecting traffic information displayed by a traffic sign may comprise the following features: a device for reading information via an optical code, which comprises an information content of the traffic information in coded form and is displayed on a display surface of a variable message sign in the form of a traffic sign, via an interface to an image capture device; and a device for evaluating the information about the optical code in order to capture the traffic information.

[0024] The described approach can be used in connection with a variable message number plate having a display surface and a device for displaying traffic information.

[0025] The problem underlying the invention can also be solved quickly and efficiently by means of these embodiments of the invention in the form of devices.

[0026] In this case, a device can be understood as an electrical device that processes sensor signals and outputs control and / or data signals depending on them. The device can have an interface, which can be implemented in hardware and / or software. In a hardware implementation, the interfaces can, for example, be part of a so-called system ASIC, which contains a wide variety of functions of the device. However, it is also possible for the interfaces to be separate integrated circuits or to consist at least partially of discrete components. In a software implementation, the interfaces can be software modules that are present, for example, on a microcontroller alongside other software modules.

[0027] Also advantageous is a computer program product with program code that can be stored on a machine-readable medium such as a semiconductor memory, a hard disk memory or an optical memory and is used to carry out the method according to one of the embodiments described above when the program product is executed on a computer or a device.

[0028] The invention is explained in more detail below with reference to the accompanying drawings. They show: Fig. 1 is a schematic representation of a vehicle and a variable message sign according to an embodiment of the present invention; Fig. 2 shows a flowchart of a method for displaying traffic information according to an embodiment of the present invention and a flowchart of a method for detecting the traffic information according to an embodiment of the present invention; Fig. 3 a camera image of a sign gantry with three variable message signs; Fig. 4 shows two variable message signs, each with an optical code as a pattern according to an embodiment of the present invention; Fig. 5 shows two variable message signs with traffic information encoded via different pulse frequencies according to an embodiment of the present invention; Fig. 6 shows two variable message signs, each with an optical code as a brightness ratio according to an embodiment of the present invention; and Fig. 7 shows a representation of two variable message signs, each with an optical code as a pulse sequence according to an embodiment of the present invention.

[0029] In the following description of preferred embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and having a similar effect, whereby a repeated description of these elements is omitted.

[0030] Fig. 1 shows a schematic representation of a variable message sign 100 with a device 102 for displaying traffic information 104 according to an exemplary embodiment of the present invention. Furthermore, a vehicle 106 with a device 108 for capturing the traffic information 104 according to an exemplary embodiment of the present invention is shown. The variable message sign 100 is mounted here, for example, on a sign gantry above a roadway on which the vehicle 106 is located. The variable message sign 100 is located within a detection range 110 of an image capture device 112 of the vehicle 106.

[0031] The display device 102 has a device 114 for providing at least one display signal and is connected to the variable message sign 100 via an interface and a signal line. The device 114 for providing is designed to provide the at least one display signal at the interface to a display surface 116 of the variable message sign 100 in order to display the traffic information 104 as an image 118 pulsed at a pulse frequency on the display surface 116 of the variable message sign 100 for a viewer and further to display an optical code 120 on the display surface 116 for the image capture device 112. The optical code 120 comprises an information content of the traffic information 104 in coded form. The image 118 and the optical code 120 can be displayed simultaneously or at different times, depending on the exemplary embodiment.The image 118 and the optical code 120 can also be emitted from spatially separated areas of the display surface 116 or from a shared area of ​​the display surface 116. To display the image 118 and to represent the optical code 120, the display surface 116 can have a plurality of light sources.

[0032] If traffic information is to be output via the variable message sign 100, the display device 102 can be configured to select, depending on the traffic information to be output, image information corresponding to the traffic information. Furthermore, the display device 102 can be configured to select, depending on the traffic information to be output, optical code information corresponding to the traffic information. The selection of the optical code information can be made depending on the display options of the display surface 116 of the variable message sign 100.Furthermore, the display device 102 can be designed to generate at least one display signal for controlling illuminants of the display surface 116, by means of which the illuminants can be controlled such that both an image 118 displaying the image information and an optical code 120 representing the optical code information are displayed. Separate display signals can be generated for generating the image 118 and the optical code 120. This can be the case, for example, if the image 118 and the optical code 120 are generated via separate illuminants. Alternatively, one or more display signals can be generated by means of which both the image 118 and the optical code 120 can be generated. This can be the case if the optical code information is integrated into the display of the image 118, for example, by modulation.

[0033] The capturing device 108 is connected to the image capture device 112 via an interface. The capturing device 108 has a reading device 122 and an evaluation device 124. The reading device 122 is designed to read in information via the optical code 120, which comprises an information content of the traffic information 104 in coded form, via the interface to an image capture device. The optical code 120 is displayed on the display surface 116 of the variable message sign 100 in the form of a traffic sign 118. The evaluation device 124 is designed to decode the information via the optical code 120 in order to capture the traffic information 104.

[0034] A video-based approach exists to recognize traffic sign information. A video-based driver assistance system detects the variable message sign 100 and "reads" the information. This approach is often supported by map data and GPS to further improve system performance. However, map-based support has limitations, especially with variable message signs 100, because their content is variable and therefore cannot be recorded on the map.

[0035] Another approach is a car-to-infrastructure approach using intelligent traffic signs. Wireless communication between traffic signs and vehicles 106 can be achieved via an ad hoc or stationary network. A position-based routing procedure with GPS-based vehicle position determination is necessary to ensure that only traffic signs relevant to the respective lane are transmitted to the driver. A significant investment is required to fully equip the infrastructure elements with appropriate transmission devices.

[0036] Variable message signs (VMS) 100 are a special type of standard traffic sign. They are increasingly being used in Germany and Europe because they enable a dynamic response to varying traffic densities. This can help avoid traffic jams and warn of other incidents.

[0037] Fig. 2 shows a flowchart of a method 200 for displaying traffic information according to an embodiment of the present invention. Furthermore, Fig. 2 is a flowchart of a method 202 for detecting traffic information according to an embodiment of the present invention.

[0038] The method 200 for displaying traffic information comprises a providing step 204 and a displaying step 206. In providing step 204, at least one display signal is provided at an interface to a display surface of a variable message sign. The display signal is designed to display the traffic information as an image pulsed at a pulse frequency and an optical code on the display surface of the variable message sign for a viewer. The optical code comprises an information content of the traffic information in coded form. In displaying step 206, the traffic information and the optical code are displayed on the display surface using the at least one display signal. The traffic information is displayed on the display surface as an image pulsed at a pulse frequency. The optical code is displayed on the display surface for an image capture device.

[0039] The acquisition method 202 comprises an acquisition step 208, a reading step 210, and an evaluation step 212. In acquisition step 208, at least the optical code, which comprises an information content of the traffic information in coded form and is displayed on a display surface of a variable message sign in the form of a traffic sign, is acquired using an image acquisition device and provided as information. In reading step 210, the information via the optical code is read in via an interface to the image acquisition device. In evaluation step 212, the information via the optical code is evaluated or decoded in order to acquire the traffic information.

[0040] Fig. 3 shows a camera image 300 of a sign gantry 302 with three variable message signs 100. Traffic information 104 is displayed on the variable message signs 100. The traffic information is provided as an image with a predetermined pulse frequency. In this example, the variable message signs 100 indicate a speed limit of 100 kilometers per hour. In the camera image 300, the traffic information 104 is not fully displayed for any of the three variable message signs 100, since the camera's detection frequency is similar to the pulse frequency.

[0041] New variable message signs (VMS) are often LED-based and use pulse-width modulation (PWM) to adjust the brightness of the signs to the ambient brightness. The frequencies used vary widely; currently, frequencies between 100 Hz and 600 Hz are known. The pulse width of the PWM (duty cycle) depends on the ambient brightness and is often significantly less than 10%.

[0042] Due to the pulsing, the variable message signs 100 are as in Fig. 3 shown for camera systems that only evaluate the image displayed to the driver of a vehicle, often not or only partially recognizable.

[0043] It is currently not possible to do without pulsing, as the LEDs used cannot be sufficiently controlled by varying the current alone.

[0044] Increasing the pulse frequency is also not possible, as this would lead to EMC (electromagnetic compatibility) problems due to the very large panels 104.

[0045] The higher the sensitivity of a camera used for video-based driver assistance systems, the shorter the camera's exposure time, which results in a higher probability of not being able to recognize the character 100 in a camera recording or of only being able to recognize it incompletely.

[0046] The additional representation of traffic information in the form of an optical code enables robust recognition of variable message signs 100 using video-based approaches, as well as robust recognition of normal traffic signs, which can also be recognized by a video-based driver assistance system without an optical code.

[0047] There are several ways to achieve camera readability of pulsed variable message signs 100 without changing the pulse frequency of the entire sign 100 in such a way that EMC problems occur.

[0048] Fig. 4 shows a representation of two variable message signs 100, each with an optical code 120 as a pattern according to an exemplary embodiment of the present invention. The variable message signs 100 each have a rectangular, black display surface 116 and a border 400 in a contrasting color. The border can, for example, be white and retroreflective. In the example shown, the variable message signs 100 are arranged directly next to one another, and the display surfaces 116 are the same size.

[0049] The display areas 116 are divided into an image area 402 and a code area 404. The image area 402 is significantly larger than the code area 404, which is arranged at a lower edge of the display area 116. The image area 402 corresponds to the display area of ​​the variable message signs in Fig. 3.

[0050] In the image areas 402, different images 118 are visible on both variable message signs 100. In the example shown, the first of the variable message signs 100 displays a speed limit of 40 kilometers per hour as traffic information, i.e., a red circular ring on a black background and a white number "40" arranged centrally within the circular ring on the black background. The second of the variable message signs 100 displays a warning of oncoming traffic as traffic information, i.e., a red triangular line on a black background and two opposite, vertical, white arrow symbols arranged centrally within the triangular line on the black background. One tip of the triangular line points upwards. The images 118 are formed by luminous dots arranged in groups on the display surfaces 116. The images 118 are displayed as in Fig. 3 are formed by light-emitting diodes that are controlled by pulses with a pulse frequency. The amount of light emitted is determined by the illumination duration of the pulses. This makes capturing the image 118 by an image capture device difficult. Additional groups of light points are deactivated and are designed to display additional images on the display surfaces 116. Light sources of the display surfaces 116 can each be controlled by suitable display signals to display the images 118.

[0051] In the code areas 404, different optical codes 120 are visible on both variable message signs 100. In the example shown, the first of the variable message signs 100 shows, as an optical code, three light points arranged in a row, with a greater distance between the first and second light points than between the second and third light points. According to this exemplary embodiment, such a pattern of light points represents, as traffic information, a speed limit of 40 kilometers per hour. In the example shown, the second of the variable message signs 100 shows, as an optical code, two light points arranged in a row, with a very large distance between the first and second light points. According to this exemplary embodiment, such a pattern of light points represents, as traffic information, a warning of oncoming traffic.Light sources of the display surfaces 116 can each be controlled by suitable display signals in order to display the optical codes 120.

[0052] The optical code 120 is imaged by a group of light points in the code area 404. In this exemplary embodiment, at least four points are arranged next to one another in a row. A light point in the code area 404 can be larger than a light point in the image area 402. Each light point in the code area 404 can represent a data bit of the optical code 120 for displaying the traffic information displayed as image 118 in the image area 402. According to this exemplary embodiment, the optical code 120 can be binary and have a word length of at least four bits.

[0053] The state of a light point in code area 404, i.e., whether the light point is illuminated or not, can represent a signal state of the respective bit represented by the light point. The four points can form sixteen different data words as an optical code 120, which can be assigned to sixteen different traffic information items.

[0054] The dots of the optical code 120 can be controlled differently than the image 118. The dots can be controlled with a code frequency that is significantly higher than the pulse frequency of the image 118. As a result, with a very high probability, at least one pulse of the code frequency falls at a time that the image capture device can capture during a capture time. This allows the optical code 120 to be reliably captured by the image capture device. Likewise, the dots of the optical code 120 can be controlled without pulses. For example, light-emitting diodes or incandescent lamps can be used in continuous operation. The dots of the optical code 120 can be operated at reduced power because the image capture device generally has a high sensitivity. Furthermore, the dots can be designed as contrasting colored and / or retroreflective surfaces that are visible or invisible depending on the signal state.Then the ambient light and / or headlights can illuminate the points sufficiently.

[0055] The optical code 120 can have a reference marking. Using the reference marking, for example, a single visible point of the optical code 120 can be reliably identified and the traffic information read out. For example, a starting point can be permanently visible at the beginning of the group. Alternatively or additionally, an end point can be permanently visible at the end of the group. The reference marking can also be implemented via a frame around the code area 404, which has a predetermined relative position to the group. In this exemplary embodiment, the frame 400 of the variable license plate 100 can be designed as a reference marking. The optical code 120 can be displayed at a fixed position relative to the frame 400 on the display surface 116 of the variable message sign 100.

[0056] The code area 404 can be arranged spatially separate from the image area 402. For example, the code area 404 can have a separate housing and be mounted remotely from a housing of the image area 402. Then, the optical code 120 can be easily captured by the image capture device, since the separate housing can be used as a reference mark for the optical code 120.

[0057] Small areas within the display area 116, the so-called variable message sign panel 100, are not pulsed or are pulsed at a high frequency. The pictogram 118 to be recognized (e.g., speed limit 80, no overtaking, cancellation of speed limit) is encoded similarly to a barcode or QR code 120. Since these are only very small areas with very few LEDs, this change is not relevant to the EMC issue and can be implemented as is. The camera records the corresponding sign 120 and decodes the visible barcode 120, even if the variable message sign 118 itself is not visible in the camera image. Fig. 4 shows an exemplary coding 120 of two different characters.

[0058] Fig. Figure 5 shows a representation of two variable message signs 100 with traffic information 104 encoded using different pulse frequencies according to an embodiment of the present invention. The variable message signs 100 correspond to the variable message signs in Fig. 4. In contrast to Fig. 4, the variable message signs are arranged one above the other. Furthermore, the image area is also the code area, since here the optical code is provided via different pulse frequencies of the images. In addition to the first variable message sign 100, a first temporal profile 500 of the first pulse frequency 502 of the first image (pulsing of the variable message sign) and a detection frequency 504 of an image detection device (clock rate of the image recording) are shown. In addition to the second variable message sign 100, a second temporal profile 506 of the second pulse frequency 508 of the second image and the detection frequency 504 of the image detection device are shown. The pulse frequencies 502, 508 each have a regular temporal sequence of pulses and pauses. The detection frequency 504 has a regular sequence of detection times and detection pauses. The detection frequency 504 is the same in the first profile 500 and the second profile 506.The first pulse frequency 502 is higher than the second pulse frequency 508, whereby the pulses at the first pulse frequency 502 are of the same length as the pulses of the second pulse frequency 508. The higher first pulse frequency 502 results in shorter pauses. As a result, the first image is emitted with a slightly greater brightness than the second image. This is barely perceptible to a viewer, since the images are emitted with a strong directional characteristic and the perceptible brightness of the images depends essentially on the viewing angle. In order to emit both images with the same brightness, the pulses of the first pulse frequency can be shortened by a factor, whereby the factor can be proportional to a difference between the first pulse frequency 502 and the second pulse frequency 508. The second pulse frequency 508 is higher than the detection frequency 504.The differences in frequencies 502, 504, and 508 result in first beats 510 between the first pulse frequency 502 and the acquisition frequency 504, as well as second beats 512 between the second pulse frequency 508 and the acquisition frequency 504. Beats 510, 512 characterize a temporal overlap of pulses and acquisition times. During beats 510, 512, the image is acquired by the image acquisition device. In the case shown here, the images are each visible in two images of the image acquisition devices. Depending on the frequency ratios between the acquisition frequency 504 and the pulse frequencies 502, 508, the images may also be visible in only one image of the image acquisition device. A first time interval between the first beats 510 is smaller than a second time interval between the second beats 512. The intervals are measurable and directly proportional to the pulse frequencies 502, 508.Therefore, the underlying pulse frequency 502, 508 can be deduced from the distances. The traffic information in the images can be clearly assigned based on the pulse frequencies 502, 508.

[0059] The pulse frequency 502, 508 of the variable message sign 100 can be used as coding for the content of the variable message sign 100. Since the clock rate of the camera image recording 504 is known, the pulse frequency 502, 508 of the variable message sign 100 can be determined relatively precisely by temporal analysis and thus the content of the variable message sign 100 can be decoded. In other words, Fig. 5 shows an example of encoding two different characters using different clock rates 502, 508 of the characters themselves. Arrows 510, 512 indicate the times at which at least parts of the character are visible in the image. The pulse frequency of the character, and thus the character content, can be decoded using the time difference (a number of frames between one appearance of the character in the image and a subsequent appearance of the character in the image).

[0060] Fig. Figure 6 shows a representation of two variable message signs 100, each with an optical code 120 as a brightness ratio according to an embodiment of the present invention. The variable message signs 100 correspond to the variable message signs in Fig. 4. As in Fig. 4, the code area has 404 luminous dots that provide the optical code 120. The dots can be arranged as shown in Fig. 4 can be reliably captured by an image capture device. The points are as shown in Fig. 4 is arranged at a predetermined position relative to the frame 400. In contrast to Fig. 4, only two points are arranged in the code area 404. The first of the points illuminates with a reference brightness. The first point thus serves as a reference mark or reference point. The reference brightness provides a comparison value for the brightness of the second of the points. The reference brightness represents a predetermined percentage value. In the example shown, the percentage value is 100%. However, the reference value can also be 50%, for example. With a reference value of 100%, the reference point is clearly defined. Here, the second point illuminates with a brightness that is less than or equal to the reference brightness. The brightness of the second point therefore has a percentage ratio to the reference brightness. The ratio represents the optical code 120. The image capture device captures the ratio.Traffic information can therefore be obtained from this ratio, since the number of possible ratios is only limited by the resolution of brightness levels when targeting the points and / or the resolution of the image capture device. In the illustrated embodiment, the second point illuminates the speed limit of 40 kilometers per hour with the same intensity as the reference point. When warning of oncoming traffic, the second point illuminates with approximately five percent of the brightness of the reference point. The traffic information is therefore encoded via the brightness ratio. A third point with variable brightness can transmit a greater variety of information than two points. This requires a fixed relative position of the third point to the reference point and the second point.For example, a connecting line between the third point and the reference point can be at a right angle to a line between the reference point and the second point. This allows a clear distinction to be made between the reference point, the second point, and the third point, regardless of the angular position of the three points in the captured image.

[0061] In other words, Fig. Figure 6 shows an example of coding two different characters using different brightness levels. One LED is operated at maximum brightness. Another LED is connected next to it, whose brightness can vary between 0% and 100%. The character content is coded using the brightness of the second LED (e.g., 100% = speed limit 100, 90% = no overtaking, etc.).

[0062] Fig. Figure 7 shows two variable message signs 100, each with an optical code as a pulse sequence according to an embodiment of the present invention. The variable message signs 100 correspond to the variable message signs in the Fig. 4 and Fig. 6. As in the Fig. 4 and Fig. 6, the code area has 404 luminous dots that provide the optical code 120. The dots are as in Fig. 4 at a predetermined position relative to the frame 400. The points can be arranged as shown in the Fig. 4 and Fig. 6 can be reliably captured by an image capture device. In contrast to the Fig. 4 and Fig. 6, only one point is arranged in the code area 404. The point is controlled with a pulse sequence. The point of the first variable message sign 100 is controlled with a first pulse sequence 700 for the speed limit. The point of the second variable message sign 100 is controlled with a second pulse sequence 702 for the warning of oncoming traffic. The pulse sequences 700, 702 have successive pulse durations, each consisting of a light period and a dark period. The pulse sequences 700, 702 have a frequency that is at least one order of magnitude lower than the detection frequency of the image capture device. The frequency of the pulse sequences 700, 702 is the same. This allows a pulse duration to be sampled with at least ten detection times. By sampling, a duration of the light periods and / or a duration of the dark periods can be recorded. The duration encodes the traffic information.The lower the frequency, the more accurately the pulse sequence can be sampled. For example, with ten detection points in time, ten different items of traffic information can be distinguished. With 30 detection points in time, 30 items of traffic information can already be distinguished. To achieve greater reliability in the differentiation, the frequency can, for example, be selected so low that a difference between a first duration and a second duration can be resolved using multiple detection points in time. In the example shown here, the first pulse sequence 700 has a light period of one third of the pulse duration and a dark period of two thirds of the pulse duration. The second pulse sequence 702 has a light period of two thirds of the pulse duration and a dark period of one third of the pulse duration. The pulse sequences 700, 702 can thus be clearly distinguished.Pulse sequences 700, 702 can also provide the optical code 120 as a sequence of consecutive light periods and / or dark periods of varying lengths. Then, a light period and / or a dark period can serve as a reference pulse with a predefined duration to mark the beginning and / or end of the sequence.

[0063] In Fig. Figure 7 shows a temporal coding. A pulse-pause ratio of 700, 702 and a frequency of flashing LEDs encode the character content. In other words, Fig. 7 an exemplary coding 120 of two different characters via a temporal pulsing.

[0064] In other words, the Fig.Four to seven camera-readable variable message signs (VMS) of the type 100. The approach presented here combines the video-based reading of traffic signs with the car-to-infrastructure communication approach. "Normal" traffic signs can still be recognized by video-based systems using classification approaches. In addition, the recognition of variable message signs of the type 100 is possible.

[0065] The variable message signs 100 according to the approach presented here are equipped with non-pulsed or differently pulsed elements that can be detected and interpreted by the camera. Any combination of the presented options can be implemented.

[0066] This allows pulsed variable message signs (100) to be recognized using the same (camera) hardware that is used to recognize "normal" traffic signs. No additional (radio) reception devices (WLAN, UMTS, GSM) are required in the vehicle. This circumvents network effects. The camera hardware in the vehicle is already present for recognizing "normal" traffic signs. If the variable message signs (100) are converted, the benefit for individual road users increases, as more and more variable message signs (100) become camera-readable.

[0067] The exemplary embodiments described and shown in the figures are selected only as examples. Different exemplary embodiments can be combined with one another in their entirety or with regard to individual features. An exemplary embodiment can also be supplemented by features of another exemplary embodiment. Furthermore, method steps according to the invention can be repeated and performed in a different order than the one described.

Claims

[1] Method (200) for displaying traffic information using a display surface (116) of a variable message sign (100), the method (200) comprising the following step: Selecting image information corresponding to the traffic information and selecting optical code information corresponding to the traffic information; Generating at least one display signal for controlling illuminants of the display surface (116), wherein the illuminants can be controlled by the display signal in such a way that both an image (118) displaying the image information and an optical code (120) representing the optical code information are displayed; and Providing (204) the at least one display signal to an interface to the display surface (104) of the variable message sign (100) in order to display the traffic information as the image (118) pulsed at a pulse frequency on the display surface (104) of the variable message sign (100) for a viewer and to display the optical code (120), which comprises an information content of the traffic information in coded form, on the display surface (104) for an image capture device (112). [2] Method (200) according to claim 1, wherein the at least one display signal is designed to display the optical code (120) in a code area (404) for displaying the code (120) arranged separately from an image area (402) for displaying the image (118). [3] Method (200) according to one of the preceding claims, wherein the at least one display signal is designed to display the optical code (120) in the region of the image (118). [4] Method (200) according to one of the preceding claims, wherein the at least one display signal is configured to display the optical code (120) using a graphic pattern. [5] Method (200) according to one of the preceding claims, comprising a step of selecting the pulse frequency in dependence on the traffic information, wherein the at least one display signal is designed to display the optical code (120) using the pulse frequency. [6] Method (200) according to one of the preceding claims, wherein the at least one display signal is configured to display the optical code (120) using a brightness ratio between a first region of the image and at least a second region of the image. [7] Method (200) according to one of the preceding claims, wherein the at least one display signal is designed to display the optical code (120) using pulse width modulation of the pulse frequency. [8] Method (200) according to one of the preceding claims, comprising a step (206) of displaying the traffic information as the image (118) pulsed at the pulse frequency on the display surface (104) of the variable message sign (100) and displaying the optical code (120) on the display surface (104) using the at least one display signal. [9] Method (200) according to one of the preceding claims, wherein the at least one display signal is designed to control a first light source of the display surface (104) for displaying the image (118) and a second light source of the display surface (104) for displaying the optical code (120). [10] Device (102) for displaying traffic information using a display surface (116) of a variable message sign (100), wherein the device (102) is designed to select image information corresponding to the traffic information and optical code information corresponding to the traffic information, and is designed to generate at least one display signal for controlling illuminating means of the display surface (116), wherein the illuminating means can be controlled by the display signal such that both an image (118) displaying the image information and an optical code (120) representing the optical code information are displayed, and wherein the device (102) has a device (114) for providing the at least one display signal at an interface to the display surface (104) of the variable message sign (100),to display the traffic information as the image (118) pulsed at a pulse frequency on the display surface (104) of the variable message sign (100) for a viewer and to display the optical code (120), which comprises an information content of the traffic information in coded form, on the display surface (104) for an image capture device (112). [11] Variable message sign (100) with a display surface (104) and a device (102) according to claim 10 for displaying traffic information. [12] Computer program product with program code for carrying out a method according to one of claims 1 to 9 when the program product is executed on a device.

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