GB2360413A

GB2360413A - Wide angle parabolic imaging and image mapping apparatus

Info

Publication number: GB2360413A
Application number: GB0006396A
Authority: GB
Inventors: Lee Scott Friend
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-03-16
Filing date: 2000-03-16
Publication date: 2001-09-19
Also published as: GB0018017D0; GB0006396D0

Abstract

Imaging apparatus comprising two imaging units 12, 12' for producing images of respective scenes, each imaging unit comprising a convex, substantially parabolic first reflector 16 reflecting an image from a scene on to a second reflector 18, the second reflector being arranged to reflect the image to an image sensor 14. The apparatus further comprises combining the images received by the image sensors to form a single continuous image of the two scenes (see figure 3(A)). This maps images from the respective detectors 14, 14' to a display (e.g. A 16:9 rectangular display) in a split-screen format. The apparatus has particular application to security monitering of large scenes.

Description

2360413 IMAGING APPARATUS This invention relates to imaging apparatus, in

particular to apparatus for producing an image of a scene.

The present invention provides imaging apparatus comprising two imaging units for producing images of respective scenes, each imaging unit comprising a convex, substantially parabolic first reflector for reflecting an image from a scene on to a second reflector, the second reflector being arranged to reflect the reflected image incident thereon to an image sen-sor; and means for combining the images received by the image sensors to form a single continuous image of the two scenes. In a preferred embodiment, the two imaging units are arranged back-to-back, 15 the first reflectors of each unit sharing a common axis of symmetry, so that each unit produces an image of a respective part of a scene. Thus, the present invention provides relatively simple and cost-effective apparatus for producing an image of a scene. The apparatus is particularly 20 suitable for use in a surveillance system for monitoring a large zone from a single vantage point. For such use, it is preferred that each of the image sensors comprises a video camera. As a result, a large zone can be monitored on a single screen using only two cameras and associated reflectors. Conventional surveillance systems require many video cameras to 25 be distributed throughout the zone to be monitored. Alternatively, the apparatus can be used in other broadcast or transmission systems, such as television systems, for example, it may be mounted on a racing car to provide an all-round field of view during racing. The resultant 30 images may be transmitted on the Internet or wide, or local, area network, or via satellite, cable or terrestrial digital or analogue video systems.

As a further alternative, the apparatus can be used in a 360 by 36011 interactive film or video system.

Although particularly suitable for imaging using visible light, the apparatus may be adapted to image using infra red, ultraviolet or any other form of electromagnetic radiation.

Each unit preferably comprises a lens situated between the second reflector and the image sensor for focusing the reflected image reflected by the second reflector on to the image sensor.

In a preferred arrangement, in each unit, the image sensor is situated within the substantially parabolic profile of the first reflector, the first reflector having an aperture formed therein for allowing the reflected image reflected by the second reflector to pass therethrough to the image sensor. This can provide a relatively compact structure for each imaging unit. In addition, the parabolic reflector can provide a relatively secure housing for the image sensor. In each unit, the image sensor is preferably positioned along an axis of symmetry of the first reflector.

In a preferred embodiment, in each unit, the second reflector comprises a substantially planar reflector, for example, positioned substantially orthogonal to the axis of symmetry of the first reflector.

In a preferred arrangement, means are provided for moving the second reflector relative to the first reflector. This can be used to adjust the size of the scene imaged by the imaging unit. For example, by moving the second reflector closer to the first reflector, the size of the scene imaged by the imaging unit is reduced. It can also be used to adjust magnification, for example, to focus on a particular part of the scene, for example, to aid identification of a person appearing in the scene.

Thus, in a preferred embodiment imaging apparatus comprises a convex, substantially parabolic first reflector for reflecting an image from a scene on to a second reflector, the second reflector being arranged to reflect the reflected image incident thereon to an image sensor, and means for moving the second reflector relative to the first reflector.

Advantageously, the apparatus can include image processing apparatus for transforming the image signal from each image sensor into image signal data and for processing the data so as to provide a predetermined display. In an embodiment of the invention, the image signal is mapped from one coordinate system to another before display.

Preferably, the image processing apparatus is adapted to map each image signal data into adjacent portions of a co-ordinate system so that the displayed images of the two scenes are continuous.

Thus, the present invention also provides imaging apparatus comprising:

two imaging units for imaging respective scenes to provide respective image signals; and image processing apparatus for transforming the image signals into image signal data and for mapping the image signal data into adjacent portions of a co-ordinate system so as to provide a continuous display of the two scenes.

The image signal data is preferably displayable in upper and lower portions respectively of a display. If so, the image processing apparatus may be adapted to map the image signal data such that the image signal data is displayable in upper and lower portions respectively of a 16:9 rectangular display.

The present invention further provides an imaging method using two imaging units for producing images of respective scenes, each imaging unit comprising a convex, substantially parabolic first reflector, a second reflector and an image sensor, said method comprising:

reflecting an image from a scene incident on said first reflector on to a second reflector; reflecting the reflected image incident on said second reflector to an image sensor; and combining the images received by the image sensors to form a single continuous image of the two scenes.

The present invention further provides an imaging method comprising the steps of:

imaging two respective scenes to provide respective image signals; transforming the image signals into image signal data., and mapping the image signal data into adjacent portions of a co-ordinate system so as to provide a continuous display of the two scenes.

The present invention further provides apparatus for providing all round viewing of a scene, the apparatus comprising:

a pair of parabolic co-axial reflectors which are oppositely convex; respective planar reflectors spaced from the parabolic reflectors; respective imaging sensors for receiving radiation reflected from the planar reflectors and for providing imaging signals; and processing means for processing the imaging signals and for deriving video signals for a display; the reflectors being arranged on optical paths such that reflected images from the parabolic reflectors are incident in the planar reflectors and are then reflected on to the imaging sensors, whereby the reflected images from the parabolic reflectors can be viewed on the same display.

In a preferred embodiment, the processing means comprises means for converting the video signals into digital signals, and the apparatus further includes means for transforming the digital signals so as to change the aspect for viewing the scene.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a schematic drawing of an embodiment of an imaging apparatus; Figure 2 is a representation of the image signal data received by each of the image sensors of the apparatus of Figure 1; Figure 3 illustrates the mapping of the image signal data shown in Figure 2 into a cartesian co-ordinate system; Figure 4 is a representation of the pano-spherical image produced by the mapping illustrated in Figure 3, and Figure 5 is a schematic drawing of another embodiment of an imaging apparatus.

With reference to Figure 1 a preferred embodiment of an imaging apparatus comprises two imaging units 12, 17. Each imaging unit 12 comprises an image sensor 14, such as a camera, a convex parabolic reflector 16 and a circular, substantially planar reflector 18. The apparatus is housed in a transparent housing 19, although use of such a transparent housing is optional.

The camera 14 and the planar reflector 18 are both positioned along the axis of symmetry 20 of the parabolic reflector 16, the surface of the planar reflector being substantially orthogonal to the axis of symmetry 20. As shown in Figure 1, the camera 14 is situated within the parabolic profile of the parabolic reflector 16, so as to provide a relatively compact structure for each imaging unit and so that the parabolic reflector 16 can provide a relatively secure -6 housing for the camera 14.

The convex parabolic reflector 16 is positioned to reflect an image of a scene on to the planar reflector 18. The planar reflector 18 in turn reflects the reflected image through an aperture 22 formed in the parabolic reflector 16 to the camera 14. A lens 24 is provided between the camera 14 and planar reflector 18, for example, in the aperture 22 formed in the parabolic reflector 16, to focus the reflected image reflected by the planar reflector 18 on to the camera 14. The tens may be provided with any suitable means for blocking light which has not been reflected by the planar reflector.

The planar reflector 18 is mounted to the lens 24 of the camera by a shaft 26 extending along the axis of symmetry 20. A motorised gear system, such as a rack and pinion arrangement (not shown), may be provided to move the shaft 26 along the axis 20 in order to vary the optical distance between the parabolic reflector 16 and the planar reflector 18. For example, decreasing the distance between the two reflectors will have the effect of reducing the size of the image reflected by the planar reflector 18, and concomitantly reducing the size of the scene imaged by the imaging unit, thus enabling a user of the apparatus to 1ocus in" on a particular feature of the imaged scene.

In the apparatus shown in Figure 1, the two units 12 are arranged back-to back, with the two parabolic reflectors 16, 16' sharing a common axis of symmetry 20. The parabolic reflectors 16, 16' may be joined, as indicated at 28, to provide a seal to prevent ingress of water or debris, and to prevent any other form of access, into the housing 30 thus defined between the parabolic reflectors 16, 1C.

The cameras 14, 14' have outputs connected to image processing apparatus (not shown), such as a suitable programmed computer, for processing the image signals output from the cameras for display on a display device.

The image processing apparatus transforms each of the signals into image signal data. Figure 2 illustrates an example of the respective image signal data 40, 40' produced from the image signals output from the cameras 14, 14' respectively when the apparatus is utilised as part of a surveillance system.

Each camera 14, 14' produces a substantially circular image 40, 40' of a scene. As shown in Figure 2, a portion 42, 42' of each of the circular images 40, 40' is masked by the planar reflector 18, 18', the size of these "blind spots" 42, 42'depending on the size of the planar reflectors 18, 18' and the distance between each planar reflector 18, 18' and the associated parabolic reflector 16, 1C.

As will be readily appreciated, it is difficult for a viewer of a display device displaying the circular images 40, 40'to identify easily particular features of the scene. Therefore, the image processing apparatus performs a mapping operation on each image signal data for transformation of the data into a cartesian co-ordinate system for output to the display device. This mapping operation is illustrated in Figure 3.

With reference to Figure 3a, in the mapping operation, each of the circular images is notionally divided into an array of pixels (the grid overlaying each of the circular images 40, 40' should be ignored for the present purposes) in a polar co-ordinate system. Each of these pixels is then mapped, using look-up tables stored in the image processing apparatus which also compensate for distortion resulting from the mapping, into a cartesian co-ordinate system for display in a rectangular display 44. This mapping technique is particularly suitable for mapping of the circular images 40, 40' into adjacent portions, such as respective upper and lower portions, of a 16:9 rectangular video display. Figure 3b illustrates three-dimensionally the result of the mapping operation, in which two substantially hemispherical, or "omni-spherical", images 50, 50, are transformed into a continuous "pano-spherical" image 60.

Figure 4 illustrates the resultant transformation of the displayed circular images 40, 40', providing a continuous two-dimensional image of the two, scenes imaged by the imaging units. As will be appreciated, the resultant rectangular image 70 enables the user of the apparatus to more readily identify particular features of the scene. The user can, at will using the image processing apparatus, magnify selected features of the displayed scene and pan the scene in any desired manner. The image 70 may be transmitted as a flat panoramic image and interpreted by a client, or remote computer software or driver, as a navigable scene which may be cropped, enlarged or rotated in real time in response to control inputs from a remote user.

As the user zooms in on smaller portions of the scene, the granularity of the viewed image will increase. Thus, the apparatus may be programmed to control movement of the planar reflectors relative to the parabolic reflectors with the magnification of the image by the user to compensate for this loss of resolution.

It will be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

For example, as shown in Figure 5 the planar reflectors 18, 18' may be attached to the inner surface of the transparent housing 19, thereby avoiding attachment of the planar reflectors to the parabolic reflectors via shafts 26.

Each feature disclosed in the description, and (where appropriate) the claims and drawings may be provided independently or in any appropriate combination.

Claims

1. Imaging apparatus comprising two imaging units for producing images of respective scenes, each imaging unit comprising a convex, substantially parabolic first reflector for reflecting an image from a scene on to a second reflector, the second reflector being arranged to reflect the reflected image incident thereon to an image sensor; and means for combining the images received by the image sensors to form a single continuous image of the two scenes.

2. Apparatus according to Claim 1, wherein each unit comprises a lens situated between the second reflector and the image sensor for focusing the reflected image reflected by the second reflector on to the image sensor.

3. Apparatus according to Claim 1 or Claim 2, wherein, in each unit, the image sensor is situated within the substantially parabolic profile of the first reflector, the first reflector having an aperture formed therein for allowing the reflected image reflected by the second reflector to pass therethrough to the image sensor.

4. Apparatus according to any preceding claim, wherein, in each unit, the image sensor is positioned along an axis of symmetry of the first reflector.

5. Apparatus according to any preceding claim, wherein, in each unit, the second reflector comprises a substantially planar reflector.

6. Apparatus according to Claim 5, wherein, in each unit, the second reflector is positioned substantially orthogonal to the axis of symmetry of the first reflector.

7. Apparatus according to any preceding claim, wherein means are provided for moving the second reflector relative to the first reflector.

8. Apparatus according to any preceding claim, wherein the two imaging units are arranged back-to-back, the first reflectors of each unit sharing a common axis of symmetry.

9. Apparatus according to Claim 8, comprising image processing apparatus for transforming the image signal from each image sensor into image signal data and for processing the data so as to provide a predetermined display.

10. Apparatus according to Claim 9, wherein the image signal is mapped from one co-ordinate system to another before display.

11. Apparatus according to Claim 10, wherein the image processing apparatus is adapted to map each image signal data into adjacent portions of a co-ordinate system so that the displayed images of the two scenes are continuous.

12. Imaging apparatus comprising:

13. Apparatus according to Claim 11 or Claim 12,wherein the image signal data is displayable in upper and lower portions respectively of a display.

14. Apparatus according to Claim 13, wherein the image processing apparatus is adapted to map the image signal data such that the image signal data is displayable in upper and lower portions respectively of a 16:9 rectangular display.

15. A surveillance system comprising imaging apparatus according to any preceding claim.

16. An imaging method using two imaging units for producing images of respective scenes, each imaging unit comprising a convex, substantially parabolic first reflector, a second reflector and an image sensor, said method comprising:

17. A method according to Claim 16, wherein the reflected image reflected by the second reflector is focused on to the image sensor.

18. A method according to Claim 16 or Claim 17, wherein, in each unit, the image sensor is situated within the substantially parabolic profile of the first reflector, the first reflector having an aperture formed therein for allowing the reflected image reflected by the second reflector to pass therethrough to the image sensor.

19. A method according to any of Claims 16 to 18, wherein the magnification of an imaged scene is adjusted by moving a second reflector relative to the first reflector.

20. A method according to Claim 19, wherein the magnification is adjusted by moving the second reflector along the axis of symmetry of the first reflector.

21. A method according to any of Claims 16 to 20, wherein the two imaging units are arranged back-to-back, the first reflectors of each unit sharing a common axis of symmetry.

22. A method according to any of Claims 16 to 21, wherein the image signal from each image sensor is transformed into image signal data which is processed so as to provide a predetermined display.

23. A method according to Claim 22, wherein the image signal is mapped from one co-ordinate system to another before display.

24. A method according to Claim 22 or Claim 23, wherein each image signal data is mapped into adjacent portions of a co-ordinate system so that the displayed images of the two scenes are continuous.

25. An imaging method comprising the steps of:

imaging two respective scenes to provide respective image signals; transforming the image signals into image signal data; and mapping the image signal data into adjacent portions of a co-ordinate system so as to provide a continuous display of the two scenes.

26. A method according to Claim 24 or Claim 25, wherein the image signal data is displayed in upper and lower portions respectively of a display.

27. A method according to Claim 26, wherein the image signal data is displayed in upper and lower portions respectively of a 16:9 rectangular display.

28. Apparatus for providing all round viewing of a scene, the apparatus comprising:

29. Apparatus according to Claim 28, wherein the processing means comprises means for converting the video signals into digital signals, and further including means for transforming the digital signals so as to change the aspect for viewing the scene.

30. Apparatus, an imaging method or a surveillance system substantially as herein described.