GB2384379A

GB2384379A - Front of train imaging system including a digital camera with zoom

Info

Publication number: GB2384379A
Application number: GB0129277A
Authority: GB
Inventors: Derek Bond
Original assignee: INVIDEO Ltd
Current assignee: INVIDEO Ltd
Priority date: 2001-12-06
Filing date: 2001-12-06
Publication date: 2003-07-23
Also published as: GB0129277D0

Abstract

A front of train imaging system comprises a high resolution digital camera in which the zoom is achieved by enlarging a section of a digital image so as to view only a very small part of it. Cameras may be provided at the trackside to allow the train driver to view images from around corners (<B>see fig. 2</B>). A GPS receiver may also be provided to generate positional information from which a data processor may calculate the train speed. An image sensor is also provided for a digital camera, the sensor area being divided into regions, each of which is appropriate to the part of the view to be imaged (<B>see fig. 6</B>).

Description

Imaging System The present invention relates to an imaging system which allows images to be viewed in an improved way.

With conventional cameras, when it is desired to view an object a long way away, a zoom lens is used which, when adjusted, adjusts the focal length of the lens such that the image is magnified. However, one of the effects of this type of zoom imaging is that, not only is the image enlarged, but the object looks as if it is much closer to the camera than it really is. In addition, as the zoom gets larger, the image deteriorates significantly.

According to the present invention, improved imaging is achieved by an imaging system including a high resolution digital camera where the zoom is achieved by enlarging the digital image so as to view only a very small part of it, such as on a screen. Provided that the resolution of the camera is high enough, a much higher magnification of a view can be achieved than from a human eye. There are a number of particularly important applications of this invention. Firstly, as a front of train imaging system. The stopping distances of trains are very long because of their mass and the speed at which they often travel. The use of a high resolution digital camera in accordance with this invention can allow the track ahead to be viewed by the driver very much better than is previously known. Conventional cameras do not work in this environment because the magnification is achieved through adjusting the focal length such that a very small part of the image in the far distance is projected onto a sensor, and the resolution is poor. In addition, the image is distorted by the changing of focal length such that the distance between the train and any object in the far distance is significantly foreshortened, and this makes it very difficult for a train driver to switch between looking down the track, and looking at a display fed by the camera. By using a high resolution digital camera and achieving the zoom through displaying on a screen a small part of the image enlarged to fill the screen, very much greater resolution can be achieved, and the foreshortening effect is also very much reduced. This system will

allow the driver to see the track well ahead of his stopping distance so that he always has time to react to a problem ahead, whether that be a red signal, or an obstruction on the track. As a result, it offers significant improvement to the safety of railways.

Other features of the invention also give some significant advantages. For example, since a train travels along a track with regularly spaced sleepers, the passing of each sleeper through or out of the field of view of the camera can be seen, and the passing of sleepers can be used to calculate the speed at which the train is travelling. The speed can also be calculated if the train carries a GPS receiver, in which case the train can also be satellite tracked.

Another advantageous feature is the possibility to allow a train driver to see around comers. This can be achieved by having track side cameras located on the outside of comers and directed down the track beyond the bend. Once a train approaches a comer, the driver's screen will change from viewing the front of train camera image to the image viewed by the track side camera and transmitted using microwave signals to the train as it approaches the comer.

Another advantage of this train imaging system is that the image data can be recorded.

This would be particularly useful in establishing a black box to record any incident which takes place during a journey, and in the event of an accident, the image data would be valuable in identifying the cause of the accident.

A further possible feature of the imaging system is the use of an infrared illuminator at the front of the train for use at night, and when conditions are poor owing to rain or fog or the like. The digital camera will need to be sensitive to such infrared light, or a second camera will need to be installed for operation during poor visibility conditions. This will allow the train driver to be able to see much further ahead than he would otherwise be able to do, thereby reducing the danger of an accident or the missing of a signal, and also reducing delays as a result of the train travelling at lower speeds than it would otherwise have to travel at in poor visibility conditions.

It should also be appreciated that an imaging system according to this invention can be applied to other situations. For example, the image from the camera can be panned, tilted and zoomed without making any changes whatsoever to the camera itself. This is achieved by a camera positioned to view a wide area with the image being formed on a high resolution sensor. Rather than moving the position of the camera or moving the zoom lens of a camera, panning, tilting and zooming can be achieved by viewing on a screen only a part of the overall image. Thus, if one wants to see the wide area, the whole image on the sensor is displayed on the monitor, whereas if a particular object at the centre of the image is to be viewed, a zooming effect can be achieved by viewing only the part of the image on the sensor in which the particular object which the user is interested in, is located. If a very high resolution sensor is used, the zooming effect can be achieved without significant deterioration of the image. Also, because the focal length of the lens of the camera is not being changed, the image is not distorted by the zooming.

Likewise, if the object being viewed now moves away from the centre of the image formed on the sensor, the object can be followed left, right, up or down merely by changing the part of the overall image which is being viewed. What is more, the zooming, panning and tilting can be achieved solely in software which is used to select the appropriate part of the image, and no changes have to be made to the camera at all.

According to a further aspect of the invention, an image sensor is divided into regions, each of which is arranged to be appropriate for the different functions to be viewed. For example, the very central part of the area may be very high resolution, whereas peripheral regions may be of lesser resolution. In the case of an image sensor for a front of train imaging system, the area of most importance is at the very centre, and the areas of less importance are above and below that field, and they can be regions of low resolution. Since the parts of the image area to the sides of the high resolution area will have scenery passing very quickly, those areas might be arranged to image those features of the scenery at high speed, but a lower resolution.

As a train advances, all objects will first appear near the very centre of the image, and as the train approaches and passes those objects they will move on the image generally radially outwardly. Therefore, it may be appropriate to have a ring of high resolution sensors around the central area so that all objects are eventually imaged in that ring.

The image data from that ring might be recorded in the black box in order to reduce the amount of data being recorded. There may be advantages in arranging the ring to effectively represent a position in the far distance at which the train could stop in an emergency. That way, any objects outside the ring will be objects which, if in the part of the train, would be hit by the train if braking has not already commenced. This ring might be a useful visual tool for the driver.

The present invention will now be described by way of example only, and with reference to the drawings in which; Figure 1 is a schematic side view of a train cab; Figure 2 is a plan view showing how the imaging system allows a driver to be able to see round a corner ; Figure 3 is an image looking down a railway line; Figure 4 is an image looking down a railway line in which the camera is arranged to view the far distance using a zoom lens; Figure 5 is a view from a camera according to the present invention using high resolution imaging instead of a zoom lens; and Figure 6 shows an image sensor.

Figure 1 shows the cab 1 of a train which is travelling to the left on tracks 2. Within the cab 1 a driver 3 controls the train looking forwards through a windscreen. Just above the driver, a high resolution digital camera 4 is located which is directed to"look" down the track, and an image from that camera 4 is put on to a display 5 which could be. a CRT display, or a suitable lightweight flat screen, such as a liquid crystal or plasma screen. The display 5 is located immediately above the driver's line of sight through the windscreen. This allows him to watch both the view ahead through the windscreen

and the far distance through the display 5. The display 5 could alternatively be a"head up"display where the image from the camera is projected onto the windscreen itself.

On the outside of the train, just above the driver, an aerial is located for receiving microwave signals. This will be explained in more detail later in the specification.

Since this invention requires considerable amounts of processing of images, a computer processor 7 is located within the cab.

As the train is travelling to the left, the driver 3 can see a certain distance ahead of the train, but the faster the train travels, the longer its stopping distance, and the train does not need to be travelling all that fast before the stopping distance is as great as the driver's maximum viewing distance. For the majority of time, because a railway network is a very limited and restricted environment with no obstructions, and only signals to control the passage of trains, there is normally no problem. However, as soon as there is an uncontrolled aspect to the environment, if the stopping distance extends beyond where the driver can see, the train will inevitably strike an object which is on the track. So, for example, if people or animals manage to get onto a railway line, or a tree falls across a railway line, if a train is travelling such that the stopping distance is greater than the distance at which the driver can see the object, the train will strike that object. This invention assists a driver in seeing very much further ahead than he can with his own eyes, thereby improving safety. The use of the high resolution digital camera gives a much higher forward magnification than the view from a human eye. By using a digital camera with very high resolution, the camera can be used to zoom to very high magnification without deterioration of the resolution of the image, thereby allowing small objects to be seen at very large distances. In addition, because the zoom is achieved electronically, and not by the use of a zoom lens which will change the focal length of the lens, distortion is very much reduced which, with a professional zoom lens significantly foreshortens the apparent distance between the viewer and the object. This effect is very much reduced in the present invention making it easier for the driver to view both the way ahead through the windscreen, and the far distance using the imaging system. This is done by taking the image that is collected on the

image sensor and magnifying the image by taking only a small area in the centre of the sensor and displaying that on the screen, enlarged to fill the screen. This is carried out electronically by the processor 7 within the cab.

It is also possible for the computer to carry pre-stored data concerning the route travelled by the train, and to compare the view collected from the camera with pre-stored data. This allows the view to be adjusted dynamically to take into account important information such as the speed of the train and its location. If the camera detects an unexpected object ahead, then the driver will be able to see that on the display 5, and the processor 7 will also be able to identify it and warn the driver of it audibly so that the driver is able to take the appropriate action.

Referring to Figure 2, another aspect is shown in which the driver is able to see around comers. This is achieved by having track side cameras 8 located on the outside of bends and positioned such that they can see down the track beyond the comer. As a train approaches, as in Figure 2, the camera 8 is switched on, and the image from the camera is transmitted as a microwave signal towards the train which receives the signal via the aerial 6, and the processor 7 will allow the display 5 to switch automatically to viewing the image from the track side camera 8 once it falls within range. Thus, the driver is able to see well beyond the comer. Track side cameras can also be added where there are workings on or around the track in particular locations or temporary hazards.

The imaging system requires special video camera technology together with state of the art data compression methods, so that images are presented to the driver in"real time", and without delay.

The train speed and location may be received via satellite tracking systems such as a GPS receiver within the cab. Alternatively, the position of the train and its speed can be computed from the images themselves, by comparing the images from the camera with pre-stored data. The speed can be calculated, for example, by analysing the frequency at which railway sleepers pass beneath the train.

The on board processor 7 contains data storage and image processing technology so that hazardous objects are detected well before a driver needs to break. Image data can be captured on a data carrier which is compact, and this arrangement is very suitable for the black box recording of events and control data.

Referring now to Figure 3, this image shows what a driver is able to see from his windscreen. If a camera is used which uses a zoom lens to look into the distance, an image such as in Figure 4 is obtained where very little can be seen, although there is an obstruction present if the resolution were high enough. In Figure 5, an image is shown which is collected by the present invention, and corresponds to what would be shown in Figure 4 were the resolution higher. As can be seen, it is clear that a very long way ahead, a person is on the line, and the driver is able to see that a very long way before he would be able to see it from the windscreen, and he is able to take immediate action to slow the train so as to avoid a collision.

Figure 6 shows how the area to the image is divided into regions of interest, each of which can be optimised for their different functions. This can be achieved by taking a single image sensor, and the electronic processing will process different parts of the image on the sensor with different resolutions. In this case, the very central part of the area has a very high resolution so that images in the very far field are of suitably high resolution, whereas in more outer areas, the images will be of a lower resolution. In this case, the whole sensor area is covered by a sensor with a resolution of 1K by 1K pixels, with the most central region comprising, say 5% of the area, with a resolution of ten times the sensor of 1 K by 500 sensors. The middle region covering 25% of the area has a resolution of 1K by 1K pixels with a 4 to 1 aspect ratio. The bottom central region has a horizontal linear array of sensors to sense forward movement. The sides have vertical array of sensors to measure both velocity and relative position. A ring of sensors of high resolution can be used since all objects approached by the train will pass through the ring as they move radially outwards.

Other arrangements of sensors can be used here, for example, having an array of different sensors each of which has the image focused onto it by a separate lens.

Different parts of each image can then be mixed together, with different sensors having different image resolutions. There are, therefore, a number of different ways of achieving this mix of image resolution areas.

Claims

Claims 1. An imaging system comprising a high resolution digital camera in which the zoom is achieved by enlarging the digital image so as to view only a very small part of it.
2. An imaging system according to claim 1, further comprising a screen arranged for displaying the small part of the digital image.
3. A front-of-train imaging system comprising a high resolution digital camera in which the zoom is achieved by enlarging the digital image so as to view only a very small part of it.
4. An imaging system according to claim 3, further comprising a screen arranged for displaying the small part of the digital image.
5. An imaging system according to claim 3 or 4, including a data processor which monitors the passing of each railway sleeper through or out of the field of view of the camera and calculates the speed at which the train is travelling from the rate at which they pass.
6. An imaging system according to any one of claims 3 to 5, further including a GPS receiver which generates positional information, and a data processor which calculates the speed at which the train is travelling from the positional information.
7. An imaging system according any one of claims 3 to 6, further comprising track-side cameras located on the outside of comers and directed down the track beyond bend in the track.
8. An imaging system according to claim 7, further comprising a track-side transmitter associated with the track-side camera, the transmitter being located such as to transmit images from the track-side camera to the train.

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9. An imaging system according to claim 8, wherein the track-side transmitter is a microwave transmitter.
10. An imaging system according to any one of claims 7 to 9, wherein, as the train approaches a corner, the screen will change from displaying the front-of-train digital camera image to the image from the track side camera.
11. An imaging system according to any one of claims 3 to 10, further comprising an image data recorder.
12. An imaging system according to any one of claims further comprising an infrared illuminator at the front of the train.
13. An imaging system according to claim 12, wherein the digital camera is sensitive to infrared light.
14. An imaging system according to claim 12, further comprising an infrared camera for operation during poor visibility conditions.
15. An imaging system according to any one of the preceding claims, wherein the image from the camera can be panned, tilted or zoomed without changing the focal length of the camera.
16. An imaging system according to claim 15, wherein the high resolution digital camera is arranged to view a wide area with the image displayed on the screen being a part of the wide area viewed by the camera.
17. An imaging system according to claim 15 or 16, wherein the wide area viewed by the camera forms a wide area image on a high resolution image sensor.

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18. An imaging system according to any one of claims 3 to 17, further comprising a computer to carry pre-stored data concerning the route travelled by the train, and to compare the view collected from the camera with pre-stored data.
19. An imaging system according to claim 18, wherein, if the camera detects an unexpected object ahead, then the processor will identify it and warn the driver of it.
20. An imaging system according to claim 18 or 19, wherein the position of the train and its speed can be computed from the images, by comparing the images from the camera with the pre-stored data.
21. An imaging system according to any one of claims 3 to 20, wherein the digital camera includes a high resolution image sensor.
22. An imaging system according to claim 21, wherein the image sensor has a surface area with a resolution of 1K by 1K pixels.
23. An imaging system according to claim 22, wherein the most central region comprises about 5% of the area of the image sensor, but has a resolution of ten times the sensor of lK by 500 sensors.
24. An imaging system according to claim 23, wherein a middle region covering about 25% of the of the area of the image sensor has a resolution of 1K by 1K pixels with a 4 to 1 aspect ratio.
25. An imaging system according to any one of the preceding claims, including an array of different sensors each of which has the image focused onto it by a separate lens.
26. An imaging system according to claim 25, wherein different parts of each image can be mixed together, with different sensors having different image resolutions.

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27. An image sensor for a digital camera, the sensor having a sensor area divided into regions, each of which is arranged to be appropriate for the different functions to be viewed.
28. An image sensor according to claim 27, wherein the central part of the sensor area has a very high resolution.
29. An image sensor according to claim 28, wherein the peripheral parts of the sensor have a lesser resolution to the central part.
30. An image sensor according to any one of claims 27 to 29, in which the sensor is part of a front-of-train imaging system, wherein the part of the image falling on the sensor which is of most importance is at the centre corresponding to the track ahead of the train, and the part of the sensor on which this part of the image falls is arranged to have a very high resolution.
31. An image sensor according to claim 30, wherein the parts of the image which is of less importance are above and below the important part, and corresponds to a part of the sensor which is arranged to have a relatively low resolution.
32. An image sensor according to claim 30 or claim 31, wherein the area of the sensor corresponding to those parts of the image area to the sides of the high resolution area are arranged to image those areas at high speed, but at lower resolution.
33. An image sensor according to any one of claims 27 to 29, arranged to produce a high resolution image in the far field, and a high speed image in the near field.
34. An image sensor according to any one of claims 30 to 32, wherein the sensor includes a ring of high resolution sensors around the central area so that, as the train advances, all objects eventually pass through and are imaged in that ring.

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35. An image sensor according to claim 34, wherein the ring is positioned to represent a position in the far distance at which the train could stop in an emergency.
36. An image sensor according to any one of claims 27 to 35, wherein the sensor area has a resolution of I K by 1K pixels.
37. An image sensor according to claim 36, wherein the most central region comprises about 5% of the area of the image sensor, but has a resolution of ten times the sensor of 1 K by 500 sensors.
38. An image sensor according to claim 37, wherein a middle region covering about 25% of the of the area of the image sensor has a resolution of 1 K by 1 K pixels with a 4 to 1 aspect ratio.
39. A front-of-train imaging system constructed and arranged substantially as herein described with reference to Figures 1 to 6.
40. An image sensor constructed and arranged substantially as herein described with reference to Figure 6.