GB2368117A

GB2368117A - Optical viewing arrangement

Info

Publication number: GB2368117A
Application number: GB0010885A
Authority: GB
Inventors: Tony Pollard
Original assignee: NEUTRAL Ltd
Current assignee: NEUTRAL Ltd
Priority date: 2000-05-08
Filing date: 2000-05-08
Publication date: 2002-04-24
Also published as: GB0010885D0

Abstract

An optical viewing arrangement provides three-dimensional viewing of an object 1, which may be surrounded by a screen or backcloth in a contrasting colour. The optical viewing arrangement comprises means for obtaining a plurality of images of the object 1, each image being a projection of the object 1 in a different angular direction. Each image consists of a two-dimensional array of pixels, and means for correlating the pixels in different images of corresponding points in the object 1 to derive a matrix of voxels each having a defined position in three dimensions. The optical arrangement may comprise a single camera 11 and means for obtaining a plurality of images comprising an array of reflecting surfaces 10 arranged petal-like around the object 1.

Description

OPTICAL VIEWING ARRANGEMENT

This invention relates to optical viewing arrangements and is concerned with capturing data from an object to enable three-dimensional (3D) images to be provided.

Existing systems for capturing 3D images are labour intensive, expensive or inaccurate. It is an object of the invention to provide an arrangement which is simple and accurate.

According to the invention an optical viewing arrangement for providing three-dimensional viewing of an object comprises means for obtaining a plurality of images of the object, each image being a projection of the object in a different angular direction and each image consisting of a two-dimensional array of pixels and means for correlating pixels in different images of corresponding points in the object to derive a matrix of voxels each having a defined position in three dimensions.

The said means for correlating pixels may comprise means, for each pixel of a 2D image having known X and Y rectangular coordinates, for determining a possible range of values of the Z coordinate for that pixel and reducing the length of such range of values by iterative calculation.

To assist in determining such possible range of values the object may be surrounded by a screen or backcloth in contrasting colour to the colours of the object.

The images required may be obtained by an array of cameras positioned around the object. However instead of such an array of cameras a single camera may be provided in which case the means for obtaining a plurality of images may comprise an array of reflecting surfaces (e. g. arranged in petal-like configuration) around a central location for receiving an object to be viewed, said surfaces being inclined so that they reflect light in the same direction from an object at the said location, and means for positioning a camera to receive such reflected light from all the reflecting surfaces simultaneously.

Preferably at least some of the reflecting surfaces are dimensioned and angled to provide multiple angled horizontal and vertical views of any one part of the object.

Advantageously all the reflecting surfaces are inclined equi-angularly.

The object may be stationary or moving. The camera may be of any type, for example a film or digital camera and depending on whether the object is still or moving the camera may be adapted to take either still or moving images.

The image captured by the camera is processed to remove any distortions introduced by the reflecting surfaces and then multiple camera images are created to correspond to the images that would have been created had multiple cameras been used. Since the angles

and positions of the reflecting surfaces relative to the camera are known, the creation of multiple images is similar to known techniques of 3D image transformation. In order that the invention may be more fully understood reference will now be made to the accompanying drawings in which: Figure 1 is a diagrammatic sketch of voxel ranging embodying the invention, Figure 2 is a diagrammatic plan view of a mirror arrangement that may be used in carrying out the invention, and Figure 3 is a side view of the mirror arrangement the plan view of which is shown in Fig. 2.

Referring now to Fig. 1 there is shown therein an object 1. It is desired to create a 3D image of object 1. To this end a plurality of cameras are positioned round the object each of which is arranged to take an image of the object from a different angle. As shown in Fig, 1 two such cameras 2 and 3 are provided and the two cameras 2 and 3 are at right angles to each other. In practice many more such cameras may be provided, in which case the angles between adjacent cameras YAII be less than a right angle. Object 1 is surrounded by a screen or backcloth which is of a single colour which is not present on the surface of object 1.

Considering Fig. 1 in more detail, the image in each camera comprises a 2D array of pixels. Each pixel from each image can be treated as a ray projected into'the scene.

Two such rays 4 and 5 from pixels in camera 2 are indicated. Rays 4 apd 5"see"only the background colour. Intersecting rays 4 and 5 is a ray 6 from camera 3. The pixel relating to ray 6 will have the colour of the object at point C at the intersection of ray 6 and object 1.

Each pixel in an image has a known X and Y coordinate. However the position of the pixel in depth, or its Z coordinate, is not known. Also each pixel of the object in each image represents a voxel on the surface of the object which is located in space by the three rectangular coordinates X, Y and Z. To establish the Z value of a pixel image a inulti-pass process of pattern recognition is used to correlate pixels representing the same features in different images and using the known X or Y value in one image to establish the Z value in another image.

Rays 4 and 5 represent the extremities of object 1. The X and Y coordinates of voxel C are known from the image in camera 3. Its Z coordinate must lie between points A and B since these points have the background colour and are therefore outside object 1. This puts a limit on the possible range of Z values for point C. By analysing neighbouring rays with the help of pattern recognition techniques the range for each voxel is gradually reduced until the Z value for point C is finally identified.

To clarify the edges of object 1 the images are sub-pixel sampled at its edges to remove any hints of background colour by comparing the edge pixels with neighbouring pixels. Pixels that are mostly object colour are adjusted to remove any hint of background colour. Pixels that are mostly background colour are adjusted to pure background colour.

While a plurality of cameras can each be used to take separate images it is possible, if object 1 is stationary, to use a single camera which is moved around the object from position to position.

Alternatively the arrangement shown in Figs. 2 and 3 can be used. As shown in those Figures, an object 1 is surrounded by an array of mirrors 10-preferably arranged in a petal-like configuration with mirrors 10 inclined so that they reflect light from object 1 in the same direction out of the plane of Fig 2 and vertically in Fig 3. A single camera (see Fig 3) is positioned to receive light from all the mirrors 10. The image captured by camera 11 is then processed to remove distortions introduced by the mirrors and to create multiple images just as if the object had been photographed from an array of cameras positioned in place of the array of mirrors. This process may also if desired clip parts of the images that are known to be reflections from other mirrors.

Other modifications and embodiments of the invention, which will be readily apparent to those skilled in this art, are to be deemed within the ambit and scope of the invention, and the particular embodiment (s) hereinbefore described may be varied in construction

and detail, e. g. interchanging (where appropriate or desired) different features of each, without departing from the scope of the patent monopoly hereby sought.

Claims

1. An optical viewing arrangement for providing three-dimensional viewing of an object, wherein said optical viewing arrangement comprises means for obtaining a plurality of images of the object, each image being a projection of the object in a different angular direction and each image consisting of a two-dimensional array of pixels, and means for correlating pixels in different images of corresponding points in the object to derive a matrix of voxels each having a defined position in three dimensions.

2. An optical viewing arrangement according to Claim 1, wherein said means for correlating pixels comprises means, for each pixel of a 2D image having known X and Y rectangular coordinates, for determining a possible range of values of the Z coordinate for that pixel and reducing the length of such range of values by iterative calculation.

3. An optical viewing arrangement according to Claim 1 or Claim 2, wherein the object is surrounded by a screen or backcloth in contrasting colour to the colours of the object.

4. An optical arrangement according to any preceding Claim and comprising an array of cameras positioned around the object to provide said plurality of images.

5. An optical arrangement according to any one of Claims 1 to 3 and comprising a single camera and said means for obtaining a plurality of images comprises an array of reflecting surfaces (e. g. arranged in petal-like configuration) around a central location for receiving an object to be viewed, said surfaces being inclined so that they reflect light in the same direction from an object at the said location, and means for positioning said camera to receive such reflected light from all the reflecting surfaces simultaneously.

6. An optical arrangement according to Claim 5 wherein said array of reflecting surfaces are arranged in petal-like configuration around said central location.

7. An optical arrangement according to Claim 5 or Claim 6, wherein at least some of the reflecting surfaces are dimensioned and angled to provide multiple angled horizontal and vertical views of any one part of the object.

8. An optical arrangement according to any one of Claims 5 to 7, wherein all said reflecting surfaces are inclined equi-angularly.

9. An optical arrangement according to any one of Claims 1 to 8, wherein said object is stationary and the (or each) camera is adapted to take still images.

10. An optical arrangement according to any one of Claims 1 to 8, wherein said object is moving and the (or each) camera is adapted to take moving images.

11. An optical arrangement according to any one of Claims 1 to 10, wherein the (or each) camera is a film camera.

12. An optical arrangement according to any one of Claims 1 to 10, wherein the (or each) camera is an electronic digital camera.

13. An optical arrangement according to Claim 5 or any one of Claims 6 to 10 when dependant from Claim 5, wherein the image captured by the single camera is processed to remove any distortions introduced by the reflecting surfaces, and multiple camera images are then created to correspond to the images that would have been created had multiple cameras been used.

14. An optical viewing arrangement for providing three-dimensional viewing of an object, said optical viewing arrangement being substratially as herein described with reference to and/or as illustrated in Fig 1 or Figs 2 and 3 of the accompanying drawings.