WO2000036845A1

WO2000036845A1 - Apparatus and method for stereoscopic image control

Info

Publication number: WO2000036845A1
Application number: PCT/GB1999/004143
Authority: WO
Inventors: Graham Stewart Brandon Street
Original assignee: Street Graham S B
Priority date: 1998-12-15
Filing date: 1999-12-14
Publication date: 2000-06-22
Also published as: GB9827546D0

Abstract

A stereoscopic image acquisition and display system is provided. The system includes a mechanism for displaying imagery either three-dimensionally or two-dimensionally. The mode of operation of the display can be selected automatically or under control of the observer, so as to avoid presenting image pairs which are not conveniently fused into a three-dimensional image by the observer. In an autostereoscopic embodiment of the system the observer's location is tracked and viewing zones are positioned to remain colocated with the eyes of the observer. If the observer moves outside the tracking range of the system, the imagery defaults to a two-dimensional presentation. The system may also include means for sensing the distance from a stereo-camera, which provides the two perspectives required for three-dimensional viewing, to the object field. When the distance to this field is less than a preset minimum, the imagery defaults to a two-dimensional presentation, to avoid parallax beyond the comfortable level.

Description

APPARATUS AND METHOD FORSTEREOSCOPIC IMAGE CONTROL

This invention is concerned with the field of three-dimensional imaging and particularly with the effective control of image content for a system which can provide different viewpoints of a subject to respectively the left and right eyes of an observer.

BACKGROUND

Where such a system achieves this without special viewing aids, such as polarised glasses, or by requiring the viewer to be positioned at a specific location, it is common practice to employ observer tracking apparatus. Examples of the use of such apparatus are to be found in International Patent Application No. PCT/GB94/00405 (Street) and related application No. PCT/GB96/03014 (Street). Such systems may be described as autostereoscopic, presenting the observer with two views of a scene, without the need to wear special glasses and achieving this for a wide range of observer locations. For the proper functioning of the system, the tracking mechanism must change the system's optical parameters to create two different viewing zones, co-located with the user's left and right eyes respectively. If, for any reason, the tracking mechanism does not meet these requirements and the image content at one viewing zone differs from that at the other, as is the requirement for a three- dimensional image to be observed, then, the observed image could become confusing, allowing the possibility of pseudoscopic viewing or two images being seen by one eye, simultaneously.

SUMMARY OF THE INVENTION

It is an object of this invention to avoid the problem of image confusion and to provide the observer with meaningful imagery, at all times.

Thus, according to the invention, apparatus for the control of the image of an object field provided by a display system for viewing by an observer, comprises automated and/or observer controlled means either for selecting two different perspective views of said object field for substantially simultaneous viewing by each respective eye of the observer, to provide a three-dimensional image, or for selecting a single perspective view of said object field for two-dimensional viewing. In one embodiment of the invention the display system is autostereoscopic and provides a right eye viewing zone and a left eye viewing zone and comprises means for sensing the location of the observer; control means for co-locating each viewing zone with a respective eye of the observer; and means for providing selectively the same or a different perspective image for viewing at each respective viewing zone.

Preferably the location sensing means comprises first means for providing a signal indicative of said location when this is available; second means for providing a second signal indicating, in use, whether the observer's location has been sensed or is unavailable; and means for selecting image data from a single perspective view for presentation at all viewing zones when said location has not been sensed.

According to a further aspect of the invention a camera system for obtaining the perspective views of the object field comprises means for sensing the distance of the camera system from the object field; and means for detecting when said distance is less than a preset limit, whereby, in use, said single perspective view is selected for viewing two-dimensionally by the observer.

The distance sensing means may comprise an auto-focus facility within the camera system.

Alternatively the distance sensing means comprises a system for measuring the parallax between corresponding points within each of the perspective views provided by the camera system.

Advantageously, a visual indicator is provided to show whether the system is operating as a three-dimensional or two-dimensional display system

Alternatively an audible alarm may be provided to indicate that the system has ceased to operate as a three-dimensional display system.

DESCRIPTION OF PREFERRED EMBODIMENT

The invention will now be described with reference to Figure 1.

The image of an object 1 is captured from respectively right and left eye points of view by two video cameras 2 and 3. An autostereoscopic display 4, capable of providing an observer 5 with different images for respectively the right eye 6 and the left eye 7, is fed with one or both of the video signals from the cameras 2 and 3. The apparatus required to determine when to provide both video signals or a selected one of them is shown schematically as module 8. This part of the system controls switches 9 and 10 as follows.

Under normal operating conditions, an observer tracking camera 1 1, provides the display system 4 with the information required to generate two distinct viewing zones 12 and 13 at the observer's location. Typically the position of these zones remain locked to the observer's location providing the latter remains within certain boundaries, shown as lines 14 and 15. The observer's right eye 6 observes an image corresponding to the video signal supplied via switch 9 by camera 2 and the observer's left eye 7 receives an image corresponding to the video signal supplied via switch 10 by camera 3. If the observer moves to a location at which the tracking camera 1 1 cannot provide the control signals for the display 4 to correctly position the viewing zones 6 and 7, for example outside the space bounded by lines 14 and 15, then a signal is sent to switch control module 8, indicating that tracking has ceased and including information concerning the last known location of the observer. When the observer moves to the right side of the tracking volume, switch 10 is changed to position 16, shown in broken line form in Figure 1, so as to provide the right eye image to both eyes of the observer. Conversely, if the observer leaves the tracking space at the left hand side, bounded by line 15, switch 9 is operated to provide both eyes with the left eye image.

The above procedure ensures that, when the observer is tracked, so that correct imagery can be displayed for autostereoscopic viewing, the display system provides both a left and right eye image for viewing within each respective viewing zone. However, when this is not the case, the observer is provided with a conventional 2D (flat) image, either from a right eye perspective or a left eye perspective, thus avoiding any false perspective or confusion and discomfort of the observer.

The apparatus of Figure 1 is shown as one half of a glasses-free teleconferencing system, in which object 1 is one of the participants and the observer 5 is the other. There are a number of different applications in which a 3D image can be relayed to an observer. For example, a stereoscopic endoscope may replace the pair of cameras 2 and 3, and provide a surgeon with a 3D image of the operative field. Under certain circumstances, it is not only the failure to track the observer which can make a 2D image more suitable for viewing than the 3D image. For example, if the camera pair is brought too close to the object field, the corresponding stereo-image pair generated can become quite difficult to fuse into a single three-dimensional image. Given sufficient depth of field, however, each of the two images can provide a useful magnified 2D close-up of the subject matter of interest. In such circumstances, a manual override, in the form of a separate input (not shown) to switch control module 8, is conveniently provided through a user activated switch, operated either manually or by voice control. It will also be apparent that a proximity detection mechanism, within the camera system, can have a preset limit on distance to the subject matter, so that, when this is approached too closely, a signal is generated to switch to 2D presentation of the image. Such proximity detection can be provided, for example, by an auto-focus mechanism or by measuring the parallax between corresponding image points within the left and right image fields provided by the camera system. It will be apparent that, although the embodiment of Figure 1 illustrates an autostereoscopic 3D display, the circumstances in which the imagery is best viewed in a 2D form, because of the camera's proximity to the subject matter, will apply to both an autostereoscopic system and a stereoscopic system which requires the observer to wear special glasses (polarised or of the LCD shutter type)

Where the switching to a 2D image presentation is forced by an automated system, such as a failure to track the observer or passing of a preset proximity limit, it is found to be useful for a visual or audible warning (not shown) to be provided by the switch control module, thereby alerting the observer to take the required action, if any.

Claims

1. Apparatus for the control of the image of an object field provided by a display system for viewing by an observer, which comprises automated and/or observer controlled means either for selecting two different perspective views of said object field for substantially simultaneous viewing by each respective eye of the observer, to provide a three-dimensional image, or for selecting a single perspective view of said object field for two-dimensional viewing.

2. Apparatus as claimed in Claim 1 which is autostereoscopic and has a right eye viewing zone and a left eye viewing zone comprising means for sensing the location of the observer; control means for co-locating each viewing zone with a respective eye of the observer; and means for providing selectively the same or a different perspective image for viewing at each respective viewing zone.

3. Apparatus as claimed in Claim 2 in which the location sensing means comprises first means for providing a signal indicative of said location when this is available; second means for providing a second signal indicating, in use, whether the observer's location has been sensed or is unavailable; and means for selecting image data from a single perspective view for presentation at all viewing zones when said location has not been sensed.

4. Apparatus as claimed in Claim 1 including a camera system for obtaining the perspective views of the object field which comprises means for sensing the distance of the camera system from the object field; and means for detecting when said distance is less than a preset limit, whereby, in use, said single perspective view is selected for viewing two-dimensionally by the observer.

5. Apparatus as claimed in Claim 4, in which the distance sensing means comprises an auto-focus facility within the camera system.

6. Apparatus as claimed in Claim 4, in which the distance sensing means comprises a system for measuring the parallax between corresponding points within each of the perspective views provided by the camera system. Apparatus as claimed in Claim 3 or Claim 4 which includes a visual indicator to show whether the system is operating as a three-dimensional or two-dimensional display system

Apparatus as claimed in Claim 3 or Claim 4 which includes an audible alarm to indicate that the system has ceased to operate as a three-dimensional display system.

A method for controlling the image content of an object field provided by a display system for viewing by an observer, which comprises automatically and/or manually either selecting two different perspective views of said object field for substantially simultaneous viewing by each respective eye of the observer, to provide a three-dimensional image, or selecting a single perspective view of said object field for two-dimensional viewing.