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(11) | EP 2 017 806 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | A traffic light |
| (57) A traffic light comprising at least one light source (5,6,7) lodged inside a housing,
to each of said light sources there being connected a dedicated power supply line
(9,10,11) for supplying power supply pulses for selectively supplying electrical power
to the connected light source, said traffic light further comprising video processing
means (12) provided for recording and processing video images of traffic circulating
at least in front of said traffic light, said video processing means being also lodged
inside said housing, at least one of said power supply lines being connected to said
video processing means for powering the latter, said video processing means comprising
a sequencer (14) provided for processing said video images according to a predetermined
sequence in order to generate traffic data, said sequencer being provided for being
triggered under control of said power supply pulses.
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[0001] The present invention relates to a traffic light comprising at least one light source lodged inside a housing, to each of said light sources there being connected a dedicated power supply line for supplying power supply pulses for selectively supplying electrical power to the connected light source, said traffic light further comprising video processing means, provided for recording and processing video images of traffic circulating at least in front of said traffic light, said video processing means being also lodged inside said housing.
[0002] Such a traffic light is known from EPA 0992964. In the known device, the video processing means comprises a camera, which is lodged inside the housing where also a red and a green light source are lodged. The fact that the camera is lodged inside the housing has the advantage that it is not necessary to foresee a particular housing for the camera. The camera records and processes video images of the traffic circulating towards the traffic light. Those video images are then used to determine the time cycle periods of the traffic light.
[0003] A drawback of the known traffic light is that powering and controlling of the light sources and the video processing means are not really integrated and require separate installation.
[0004] It is an object of the invention to realise a traffic light with an improved integration of the powering and controlling of both the light sources and the video processing means.
[0005] For this purpose, a traffic light according to the present invention is characterised in that at least one of said power supply lines is connected to said video processing means for powering the latter, said video processing means comprising a sequencer provided for processing said video images according to a predetermined sequence in order to generate traffic data, said sequencer being provided for being triggered under control of said power supply pulses. Due to the fact that the video processing means are powered by the power present on the power supply line, there is no need to have a separate power line for the video processing means. Moreover, as the sequencer is triggered by the power supply pulse, there is no need to generate a separate trigger pulse for controlling the video processing means. The use of the power supply pulse as a trigger pulse also enables the sequencer to know exactly at what stage in the traffic light cycles the traffic light is and to process the video data in function thereof.
[0006] A first preferred embodiment of a traffic light according to the present invention is characterised in that said video processing means comprises a power back-up power source, having an input for receiving said power supply pulses, said back-up power source being provided for being charged upon receipt of said power pulse and for supplying electrical power to said video processing means. The use of a power back-up power source enables to power the video processing means during the whole cycle, despite the fact that the power supply pulses only supply power during a fraction of the cycles.
[0007] A second preferred embodiment of a traffic light according to the present invention is characterised in that said video processing means are connected via said power supply line to a traffic control unit, provided for generating traffic control instructions on the basis of said traffic data. In such a manner, the processed video images are transported via the supply lines and no particular transmission lines are required for transporting the processed video images.
[0008] The invention will now be described in more details with reference to the annexed drawings. In the drawings :
figure 1 shows a traffic light according to the present invention and placed at a cross road; and
figure 2 shows schematically the electronic circuitry of the traffic light according to the present invention.
[0010] A traffic light 1, as shown in figure 1, is generally placed at a cross road of roads 2 and 4. The traffic light usually has a red 5, green 6 and orange 7 light source. Preferably, the light sources are formed by LED's. The latter have the advantage that they take less place and that they consume less electrical power. Sometimes supplementary light sources are added, for example for controlling the traffic which turns to the left. It should be noted that the present invention is not limited to traffic lights having a red, a green and an orange light source but also applies to other types of traffic lights, such as for example traffic lights having only one orange flashing light signal. The traffic light is generally used for controlling a vehicle traffic but can also be used for controlling a pedestrian traffic.
[0011] Video processing means 8 are lodged inside the housing of the traffic light, thereby avoiding having a particular housing for the camera. The video processing means comprises preferably a camera and are used in order to pilot the cycle for the different light sources to be switched on. The camera records the vehicle 3 and/or pedestrian flux of the traffic circulating at least in front of the traffic light. In such a manner, the density of the recorded flux can be taken into account for determining the time period of each light source within the cycles. For this purpose, the camera records images which are then processed by the video processing means in order to generate traffic data. Based on the processed traffic data, the time period is determined in order to obtain an efficient traffic management.
[0012] Figure 2 shows schematically the electronic circuitry of the traffic light according to the present invention. Each of the light sources 5, 6, 7 have a dedicated power supply line, respectively 9, 10 and 11. The power supply line supplies to its assigned light source power supply pulses for selectively supplying electrical power to the connected light source. So, for example when within the cycle of the traffic light, the green light source has to be activated, power will be present on the power supply line 10. This power is available as a power supply pulse having the period during which the considered light source has to be activated. In the remaining time of the cycle where the considered light source has not to be activated, no power is present on the power supply line of the considered light source.
[0013] At least one of the power supply lines is connected to the video processing means 12. In the example of figure 2, power supply line 9, supplying the red light source is connected to a power and control input of the video processing means 12. It could of course also be possible to have two or all power supply lines connected to the video processing means. If only one power supply line is connected to the video processing means, care has to be taken that the video processing means are powered during the whole time period of the traffic light cycles, since the video processing means are only powered by the power supply pulses and there is no separate power supply for the video processing means. This has the advantage that there is no need to have an additional power supply line for the video processing means.
[0014] If only one power supply line is connected to the video processing means, the latter comprises a power back-up source 13 having an input for receiving the power supply pulses. The power back-up source is for example formed by a capacitor or a battery. The power back-up source is provided for being charged upon receipt of the power pulses and for supplying electrical power to the video processing means. So, when in the example shown in figure 2, the red light source is activated, power is supplied to the power back-up source 13 which is thereby charged. The power back-up source is dimensioned in such a manner that sufficient electrical power can be charged to have the video processing means operated until the subsequent power pulse for the subsequent cycle is received. Moreover, sufficient electrical power has to be supplied to charge the back-up power source. When LED's are used, their lower voltage is advantageously as they operate at a lower voltage than usual lamps and so nearly no voltage transformation is required for feeding the video processing means.
[0015] The receipt of the power supply pulse by the video processing means also acts as a trigger for the latter. The video processing means comprises a sequencer 14, for example formed by a micro processor, provided for processing the video images according to a predetermined sequence. In the example shown in figure 2, the power supply pulse is the one of the red light source. So, upon receipt of this power supply pulse, the sequencer 14 knows that the right light cycle part is activated and it can start the processing dealing with this part of the traffic light cycle. When the power supply pulse goes down, the sequencer is informed that the red light cycle is over and can thus consequently start with the processing of video images for the other part of the traffic light cycle.
[0016] The video processing means preferably also comprises a SDRAM 15 and a flash 16 memory connected to the sequencer. The latter is also connected to the camera 8 in order to receive the video data recorded by the camera and send control pulses to the camera.
[0017] The back-up power source 13 is part of a power supply unit which is also provided for data transmission. The latter unit is connected via a data over power line 12 to the sequencer 14. In such a manner, the video data processed by the video processing means is transferred over the power supply line 9 to a controller unit 17, which is preferably remote from the traffic light. By use of the power supply line for also the data transmission of the video data processed by the video processing means, no separate connection line is required for the data transport. The controller unit is provided for generating traffic control instructions on the basis of the processed video images and send the latter to the traffic light for adapting the cycle period in function of the traffic data collected from the processed video images.
1. A traffic light comprising at least one light source lodged inside a housing, to each
of said light sources there being connected a dedicated power supply line for supplying
power supply pulses for selectively supplying electrical power to the connected light
source, said traffic light further comprising video processing means provided for
recording and processing video images of traffic circulating at least in front of
said traffic light, said video processing means being also lodged inside said housing,
characterised in that at least one of said power supply lines is connected to said video processing means
for powering the latter, said video processing means comprising a sequencer provided
for processing said video images according to a predetermined sequence in order to
generate traffic data, said sequencer being provided for being triggered under control
of said power supply pulses.
2. A traffic light as claimed in claim 1, characterised in that said video processing means comprises a power back-up power source having an input
for receiving said power supply pulses, said back-up power source being provided for
being charged upon receipt of said power pulse and for supplying electrical power
to said video processing means.
3. A traffic light as claimed in claim 1 or 2, characterised in that said video processing means are connected via said power supply line to a traffic
control unit provided for generating traffic control instruction on the basis of said
traffic data.
4. A traffic light as claimed in any one of the claims 1 to 3, characterised in that said light sources are formed by LEDs.