GB2365143A

GB2365143A - Omindirectional imaging apparatus with two imaging systems

Info

Publication number: GB2365143A
Application number: GB0104695A
Authority: GB
Inventors: Lee Scott Friend
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-07-21
Filing date: 2001-02-26
Publication date: 2002-02-13
Also published as: GB0104695D0

Abstract

Omnidirectional stereoscopic apparatus with two imaging systems displaced on the same optical axis, one of which systems may be larger than the other by a factor depending on a predetermined interocular distance. The imaging system can employ two convex reflectors 5a, 5b and lens systems 6a, 6b for projecting an image onto two CCDs (charged coupled devices) 7a, 7b. The lenses maybe fisheye lenses and reflecting mirror faces 1d, 2d can be included. Also disclosed is omnidirectional imaging apparatus having a reflecting surface, which can be in the form of a beam splitter, for reflecting an omnidirectional image of a scene in order to derive two views of the reflecting surface.

Description

<Desc/Clms Page number 1> Stereoscopic Omni Directional Imaging Devices The invention relates to oninidirectional stereo photography apparatus for stills, video or film applications.

In stereoscopy a scene needs to be recorded twice, so that one recording has a horizontal or lateral offset. This addresses our ability to use two eyes to view a scene known as binocular vision, and gives the sense of three-dimensional relief The distance known as parallax betweenthe two viewpoints gives differences in sighting foreground objects, relative to distant objects. The distance between two recordings, or lateral displacement, is generally about the average separation between two eyes, i.e. approx. 65mm and this is known as interocular distance.

In the prior art much work has been carried out to find an optimum oninidirectional viewing system. For example, Nayer in US 6118474 teaches a system involving a camera on to a parabolic or truncated Parabolic reflector, using either standard or telecentric lens groupings to record the reflected scene along the image axis, but he makes no provision for recording stereo images by utilising reflectors of varying size. In Rosendahl, US 4012126, we see the use of hyperboloidal primary reflectors with secondary concave reflectors in confocal relation to achieve a more compact arrangement, but no provision for stereo imaging by using reflectors of different sizes. In Nalwa US 6115,176, we see a pyramidal reflector system utilising four six or eight side pyramidal reflectors. We further see no provision for recording stereo images by using a secondary reflector set.

ZD My GB Patent Application Nos 00 18017.4 filed 21 July 2000 and 00 19850.7 filed I I August 2000 disclose omnidirectional stereoscopic viewing arrangements. My GB Patent application No. 0023786.7 discloses arrangements for onmidirectional viewing which include imaging systems displaced on the same optical axis.

In oninidirectional imaging, the problem of image separation is amplified by the all round view of the sensors negating the use of cameras in a side by side configurations. The

problem can further exacerbated by a 360 degree view results in image separation reversals. The present invention seeks to address problems of the former type - that of image gathering without the second image sensor being visible to the first. The problems of reversal can be dealt with by image processing. For authentic three-dimensional viewing we need to see round the side of an object recorded by the first sensor, and there can be no real substitute for the gathering of this information.

According to one aspect of the present invention, omnidirectional stereoscopic imaging apparatus comprises two imaging systems displaced on the same optical axis, one of which systems is larger than the other by a factor depending on a predetermined interocular distance. Preferably, the imaging systems employ two convex reflectors, one ofwhich is larger than the other by a size factor. determined by the amount of interocular distance required. The main aim is to displace one recording from the next, consistently in a 360-degree axis, and ideally in a 360-degree vertical axis. Interocular distances greater or less than standard 65mm. separation can still achieve credible results for the purposes of hypersteroscopy- as in say in arial photography. In this instance the whole subject is too distant to give useful visible difference in a pair of stereo images with the standard 65mm. separation, and an abnormal separation or greater distance is usually achieved by allowing time for the aircraft to travel an appropriate extra distance. In a fixed image capture situation the distance in the separation is increased during image capture In macro or close up imaging, objects will be too displaced with standard separation, consequently the dimensional relief should be reduced by reducing the separation during the image capture this technique is referred as hypo stereoscopy.

Instead of using Z:) convex reflectors, two fisheye lenses can be spaced apart on the same axis, one lens system being larger than the other by the factor of the interocular distance. Z) According to another aspect of the present invention, omnidirectional imaging apparatus comprises two imaging systems displaced on the same optical axis by the interocular distance.

In the latter aspect, it is not necessary for the size of the two imaging systems to differ, since they are separated by the interocular distance.

According to a further aspect of the present invention, oninidirectional imaging apparatus comprises means having a surface for reflecting an omru* directional image of a scene, means C) for deriving two views of the reflecting surface, which views are separated by the interocular distance.

The means for deriving two views of the reflecting surface can be a beam splitter, or a means of providing a binocular view, for example, where reflecting surfaces or prisms direct light on the respective right and left hand paths to lenses which focus the respective right and left images on a sensing surface.

Further reference on stereo photography can be obtained fromAdvanced Photography by M.J. Langford ISBN 0 240 51029 1 Apart from uses in film and entertainment purposes, the gathering of stereo or 3 dimensional information has applications usefiil in security and defence, e.g. for range finding and targeting.

Preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure I shows an embodiment with small and large convex reflectors separated on the same optic axis; Figure 2 shows a generally similar embodiment, which is used for 360 x 360 viewing I= CD Figs. 3, 4 and 5 show modifications of the arrangement shown in Fig. 2)- Fig. 6 shows an arrangement based on using flat reflecting surfaces in pyramidal or polygonal ZD convex reflectors,

Fig. 7 shows a 360 x 360 version of Fig. 6, Fig. 8 shows an alternative embodiment with convex reflectors of the same size spaced apart by the interocular distance.

Figs. 9 and 10 show binocular arrangements for viewing a reflecting surface, useful for 3 60 x 180 and 360 x 360 viewing, Figs. I I and 12 show similar viewing arrangements but using fisheye lenses of different sizes spaced apart on the optic axis.

In some of the embodiments to be described, two differently sized mirrors are located on the same optical axis with a size difference equal to the interocular distance of 65 nun. This figure may vary for the purpose of hypersteroscopy / hypostereoscopy for subject of varying distance. There would be a 65mm difference in size of the two mirrors in the apparatus from the central axis to the edges. The recorded scene strikes the larger mirror from a wider or horizontally displaced viewpoint allowing image ar-tefacts unseen by the smaller mirror with its narrower viewing arc to be recorded. The recorded signals of the different cameras are recorded and displayed at the same size and resolution, however there is clear visible differences in the scene giving the output genuine three dimensional relief .

The use of a secondary reflector in each hemisphere reduces the vertical shift by bringing the two interocular ( right & left )Mirror sets closer together.

Parabolic, truncated parabolic or hyperboliodal reflectors of differing sizes can be used to achieve interocular distance in either 3 60 degrees vertically and up to 210 degrees vertically. With the use of standard lens groupings or by the use of telecentric lens groupings. Other Z:1 embodiments include the use of four six or eight sided pyramidal shaped reflectors.

Other methods of stereoscopic omnidirectional imaging use horizontally arranged systems, where interocular distance can be created in a 360x360 back to back embodiment by spacing the reflector sets at interocular distance, rather than using mirrors of differing size.

Other embodiments imacye stereo scenes on 360 degrees on the horizontal by 360 degrees on the vertical axis utilising parabolic, truncated parabolic or hyperboliodal reflectors with use of standard lens groupings or telecentnic lens groupings. The panosphereical output is intended by the use of computer image process involving spatial transformations and co ordinate image mapping providing the viewer with a flat plane out put for navigable display. Referencc- can be made to my co pending applications. Further reference can be made to Digital Image warping by George Wolberg ISBN 0-8 186-8944-7, Space Image Processing by Julio Sanchez, ISBN 0-849'-)'-3113-7.

For stills image processing, on the parabolic type reflectors, the 2 images can be processed individually using Adobe Photoshop, utilising the Polar co ordinate filter, checking polar to rectangle option. The images can be translated individually to a plane viewable image, for further use in either anyglyphical or polarising display means Turning now to the drawings, Figure I shows an embodiment where the difference in mirror size is achieved with parabolic type reflectors I a, lb, capable ofrecording an image hemisphere of 3 60 to approx. 2 10 degrees. The drawing shows a primary mirror (I a, I b) and secondary mirror (2a,2b) for each image ( left & right). The secondary mirrors may be of plane or concaveform. The top camera (including, for example, a lens focusing light onto a-CCD) 3a, and reflectors may be raised to allow sight over the bottom reflectors. The mirror 2b and its backing shield the upper mirror assembly I a,2a.

In Figure 2 similar reference numerals identify similar parts and these are the same above and below the horizontal plane which divides the back to back convex reflectors I b. The back to back configuration records stereo images over the full Vertical axis as well as the horizontal with plane secondary mirrors same for figure 3, except we replace the secondary reflectors with a concave secondary reflectors. gathering devices Figure 3 shows a combination utilising a camera 3 c, directly onto the top reflector I a, negating the use of a secondary reflector for the smaller mirror.

Figures 4 & 5 replace secondary reflectors with cameras 3 d, which are directed at the primary

reflectors 2a, in each image hemisphere. giving 360x360 stereo view. In Figure 5 we see a 360 up to 2 10 degree single hemisphere embodiment. This embodiment increases the vertical shift. Figure 6 shows a pyramidal mirror assembly, with a means of gathering image information form each mirror face I d, 2d. These faces or facets are part of a pyramidal or polygonal structure, only six such faces being present in Fig. 6 to simplify the drawing. These facets reflect light upwardly (or downwardly) into respective reflecting systems 5a,5b, which turn the light through two right angles before directing it through lens system 6a, 6b, onto a part of the surface of CCD 7a, 7b. Three of such ray paths can be seen in the cross section which correspond with three of the six sides or facets of this structure. The apparatus is shown with a mirror assembly transmitting each scene into the centre ofthe apparatus. Other embodiments may use prisms or fibre optical means, on either a four six or eight side mirror. Figure 7 shows a back to back embodiment to allow for greater fields of view.

Figure 8 shows an embodiment which, if used horizontally, the interocular distance can be created in a 360x360 back to back embodiment by spacing the reflector sets at interocular distance, rather than usin- mirrors of differing size. In this embodiment, parabolic convex reflectors I a, 2a, reflect light onto respective planar mirrors 2a,2b, which in turn reflect light onto cameras 3 a, 3b.

Figures 9 and 10 are respective 360 x 180 and 360 x 360 arrangements in which a beam splitter or binocular means 8a,8b, views a omnidirectional image in the reflecting surface of a convex reflector 2a,2b. The separation between the ray paths is the interocular distance. The beam splitter or binocular arrangement can be fitted with means for adjusting the spacing between the ray paths, so as to provide an interocular distance suitable for viewing the particular panoramic scene. For example, the scene may be near or far and the distance can be adjusted accordingly. A device fitted with a dual camera assembly can include a worm drive or adjustable screw to allow for Hypersteroscopy, / hyposteroscopy to adjust the distance between the 2 lenses for any extremes in the distances of the objects viewed. The normal position would use the standard interocular separation of 65 mm. To provide for 360 degree imaging on each Honizontal axis the beam splitter described in fig 7 could be utilised in each of the four lenses. The left and right images can be received on a CCD as in the

previous embodiments.

In Figs. I I and 12, differently sized fisheye lens systems I Oa, I Ob, are separated by the interocular distance on the same optical axis, and one lens is larger than the other by a factor related to the interocular distance. In this embodiment, the lens systems focus their respective omnidirectional images on respective imaging devices, such as CCI)s 11 a, 1 lb.

Drawings are not to scale and specific lens groupings and mountings are not detailed. Further references can be obtained from publications such as Modern Optical Engineering by Warren Smith ISBNO 07 136360 2. Once specific conjugate distances are established software programs such as Code V from Optical Research Associates or Zemax, fi-om Focus Software Inc, can be utillsed to prepare specific or individual prescriptions.

The apparatus may use transparencies to protect the lenses and reflectors or may use a solid optic between primary and secondary Mirrors. The shape of such coverings should prescribe symmetry that minimises coma or stigmatism.

In the stereo display, when viewed with anyglypical glass (a red filter over the right eye and a green filter over the right) if the output signal is displayed separately with each side toned for red and green a perception of depth is given to viewer. Another known art is the use of polarising; glasses for the viewer and polarising filters for the dual projectors. Stereo computer displays by such manufacturers as Philips or Sharp another possible alternative. Whilst both these methods are in the background art, the difference between them and in this invention is the camera designs. The invention can be embodied to allow up to 360x360 degree image capture in real time or live relay or transmission of video or film images suitable for multicast applications, or for range finding and targeting allowing the stereo image scene can be viewed, with minimal optical aberrations or distortions predominant in other systems, in the central annular viewing area.

Claims

CLAIMS 1. Omnidirectional stereoscopic imaging apparatus comprising two imaging systems displaced on the same optical axis, one of which systems is larger than the other by a factor depending on a predetermined interocular distance.
2. Apparatus according to claim 1, wherein the imaging systems employ two convex reflectors, one of which is larger than the other by a size factor determined by the amount of interocular distance required,
3. Apparatus according to claim 1, wherein the imaging systems employ two fisheye lens systems, one of which is larger than the other by a size factor determined by the amount of interocular distance required.
4. Omnidirectional imaging apparatus comprising two imaging systems displaced on the same optical axis by the interocular distance.
5. Apparatus according to claim 4, wherein the imaging systems are of substantially the same size.
6. Omnidirectional imaging apparatus comprising means having a surface for reflecting an ZD onmidirectional image of a scene, means for deriving two views of the reflecting surface, which views are separated by the interocular distance.
7. Apparatus according to claim 6, wherein the means for deriving two views of the reflecting surface can be a beam splitter, or a means of providing a binocular view.
8. Apparatus according to any preceding claim including means for adjusting the relative distance between reflecting, surfaces and/or lens systems to adjust the interocular distance.