WO1997003378A1

WO1997003378A1 - System with movable lens for producing three-dimensional images

Info

Publication number: WO1997003378A1
Application number: PCT/CA1996/000452
Authority: WO
Inventors: Anthony B. Greening; Thomas N. Mitchell
Original assignee: International Telepresence Corporation
Priority date: 1995-07-07
Filing date: 1996-07-04
Publication date: 1997-01-30
Also published as: AU6185796A

Abstract

An imaging system for producing three-dimensional images provides right images and left images in a single image path. The images are viewed through a stereoscopic viewing system so that a viewer sees only the right images with the right eye and the left images with the left eye. No signal or light restrictions are needed in the image path for either the right image of the left image so there are no viewing restrictions. The system has a camera for viewing an object in the image path, a movable lens positioned in the image path to move so that a right image and a left image are seen by the camera. The lens is moved between the two image path positions and retained in each position for a sufficient time for the camera to view each image, and a stereoscopic viewing system operates with a synchronization system to synchronize the lens movement so that a viewer sees only the left image with the left eye and only the right image with the right eye.

Description

SYSTEM WITH MOVABLE LENS FOR PRODUCING THREE DIMENSIONAL IMAGES

Technical Field

The present invention relates to stereoscopic viewing of an image from a camera. More specifically, the present invention relates to a movable lens positioned in a single image path or light path and a high speed switching device for moving the lens thus providing right images and left images in the single path to provide stereoscopic viewing.

Background Art

Most imaging systems used today are two dimensional. A camera, for example, has a single image path or light path and produces a two dimensional image. The term "camera" used throughout this specification means any type of single objective lens imaging system including a single imaging sensor together with lens or focusing arrangement which can produce or reproduce a picture of an object. Examples of such imaging systems include but are not limited to video cameras and film cameras.

A single lens stereoscopic imaging system is described in our co-pending U.S. patent application Serial No. 08/227,556, the disclosure of which is incorporated herein by reference. In the co-pending application a left and right image perspective are obtained by moving an opaque leaf laterally at high speed in an image path. We have now found that whereas this system provides us with stereoscopic viewing, we can omit the opaque leaf and move a lens positioned in the image path from a right position to a left position to produce a right image and a left image in the single image path. These images may then be used for stereoscopic viewing.

The application of stereoscopic viewing or three dimensional imaging is particularly useful for endoscopic systems wherein the movable lens can be located between an endoscope and a fixed objective lens at the front of a video camera. When the lens moves between the two positions, two images are created at the sensitive surface of the video camera representing a left image and a right image. A long focus movable lens may be located at the front of an objective lens of a video camera. A stereoscopic optical system is incorporated with a high speed electromechanical switch moving the lens between the two positions. An example of an optical system is that disclosed by Carter in U.S. Patent 4,761,066 which utilizes a beam splitter. With regard to the viewers, an example of a liquid crystal stereoscopic viewer is disclosed by Roese in U.S. Patent 4,021,846. The concept of utilizing a passive eyewear for a stereoscopic viewer includes lenses with coloured filters therein. Such a system is disclosed in U.S. Patent 3,712,199 to Songer.

As disclosed in co-pending application Serial No. 08/227,556, the present invention provides stereoscopic viewing utilizing existing two dimensional imaging systems. The key difference in the present invention is that at least one lens is moved rather than an opaque leaf, thus there is no signal restriction or light restriction in the image path or light path.

Disclosure of Invention

The present invention provides an imaging system for producing three dimensional images comprising a camera for viewing an object in an image path, a movable lens positioned at a location in the image path between the object and the camera, the lens movable in the image path between a left position providing a left image in the image path and a right position providing a right image in the image path, the left image and the right image required for stereoscopic viewing, means for moving the movable lens between the left position and the right position and retain the movable lens in each position for a sufficient time for the camera to view the left image and the right image individually, stereoscopic viewing means to view the left image from the camera with one eye of a viewer and to view the right image from the camera with the other eye of the viewer, and synchronization means to synchronize the means for moving the movable lens and control the stereoscopic viewing means so that the viewer sees only the left image with one eye and only the right image with the other eye.

The present invention also provides a method of stereoscopic viewing an object comprising the steps of positioning a movable lens at a location in the image path between the object and a camera, moving the movable lens in the image path between a left position providing a left image in the image path and a right position providing a right image in the image path, the left image and the right image required for stereoscopic viewing, retaining the movable lens in the left position and the right position for a sufficient time for the camera to view the left image and the right image individually, and synchronizing alternately the left image and the right image on the camera with stereoscopic viewing means so that a viewer sees only the left image with one eye and only the right image with the other eye.

Brief Description of Drawings

In drawings which illustrate embodiments of the present invention, Figure 1 is a schematic diagram showing the components of the imaging system according to one embodiment of the present invention,

Figure 2 is a schematic side elevational view showing an endoscope with fixed lens and video camera as presently known for two dimensional prior art viewing,

Figures 3, 4 and 5 are schematic side elevational views showing an endoscope and video camera with a movable lens having different movements according to different embodiments of the present invention,

Figures 6 and 7 are side elevational views showing linear movement of a movable lens between a first position and a second position,

Figure 8 is a side elevational view showing a movable lens with a mechanism to rotate the lens about a lens axis,

Figure 9 is a top view of the movable lens of Figure 8 showing the lens in a first position and in a second position,

Figure 10 is a side elevational view showing a movable lens with a mechanism for moving the lens in an arc, Figure 11 is a top view of the movable lens of Figure 10, showing the lens in a first position and in a second position.

Best Mode for Carrying Out the Invention

The components to make up the imaging system of the present invention include a camera 10 which in the embodiment shown has an objective lens 12 positioned in front thereof . In some instances additional lenses are provided; in other instances the objective lens may be the movable lens. A movable lens 14 is positioned in an image path or light path 16 from an object and focuses the image onto the sensitive surface 18 of the video camera 10. A high speed switching device 20 (more of which will be described hereafter) is attached to the movable lens 14 and provides movement from a first position to a second position, thus providing a left image and right image at the sensitive surface 18 of the video camera 10. Both the left image and the right image are within the image path 16.

The camera 10 provides a signal through a video processor 22 to a video monitor 24. The video processor 22 also has therein a synchronizer which synchronizes the high speed switching device 20 with an electronic synchronizer 26 providing a signal to a stereoscopic viewing arrangement 28, in this case a pair of liquid crystal shuttered glasses. Thus, in operation the video processor 22 synchronizes the movement of the movable lens 14 with the stereoscopic viewing arrangement 28 so that the right eye sees only the right image and the left eye sees only the left image. The video processor 22 also corrects for offsets between the right and left image as well as aberrations caused by lens movements.

A standard endoscope arrangement 30 is shown in Figure 2 of the type known in the prior art and used for two dimensional viewing. A video camera 10 and objective lens 12 are positioned on a light path 16 through a fixed lens 31, the light path 16 extends down an endoscope 30 for viewing an object.

Figures 3, 4 and 5 show schematic movements of the movable lens 14. Unlike Figure 2 which has a fixed lens 31, the movable lens 14 in Figures 3, 4 and 5 moves between a left position and a right position. In Figure 3 the movable lens 14 has a linear movement, moving a predetermined distance which changes the position or state of the lens and thus provides left images and right images when the movable lens 14 is in the left position or the right position. Thus, the movable lens 14 creates two images, one of which is observed with the right eye, and the other with the left eye. These two images provide stereoscopic viewing. When the movable lens 14 has a linear movement then offset images occur which if not corrected make viewing difficult. However, the video processor 22 corrects the offset between the images by bringing them together thus a viewer sees the two images aligned one with the other.

Figure 4 illustrates the movable lens 14 rotating about a central axis through the center of the movable lens 14 and Figure 5 illustrates the movable lens 14 moving in an arc between a left position and a right position. It will be apparent that other arrangements of movement may be made for the movable lens 14, as long as the right position and the left position provide a right image and a left image on the image path or left path so the object is seen in parallax images thus providing a stereoscopic viewing through the stereoscopic viewing arrangement 28.

When the movable lens 14 rotates or tilts about a central axis (Figures 4) or rotates or tilts in an arc (Figure 5) then aberrations can occur between the left image and the right image due to the tilting or moving of the lens which may change the lens position in the image path. These aberrations are corrected electronically in the video processor 22 such that a viewer does not see deviations that may occur between the left and right image. Figures 6 and 7 illustrate a mechanism for moving the movable lens 14 between two fixed positions. Figure 6 shows the lens in what might be referred to as a right position when viewed from the right and Figure 7 shows the lens 14 in what might be referred to as a left position when viewed from the right. Two solenoids or electromagnets 32 each having dampers 34 are positioned one on each side of the movable lens 14 and the electronic synchronizer 20 activates the solenoids 32 so that the movable lens 14 moves linearly between the right position and the left position. The dampers 34 assist in stopping the movable lens 14 with substantially no vibration as it is important that the lens 14 remains stationary in each position for an exposure from a camera.

Figures 8 and 9 illustrate a movable lens 14 with a mechanism for rotational movement between a right position and a left position. The movable lens 14 is mounted at its center on an axial pin or shaft 36 between bearings 38. An arm 40 attached to the pin or shaft 36 extends to an iron armature 42 which is moved by the two electromagnets 32 in the same manner as explained for the lateral movement of the movable lens 14 as shown in Figures 6 and 7.

Figures 10 and 11 show a movable lens 14 with a mechanism for moving in an arc between a right position and a left position. The movable lens 14 is supported on an arm 44 with a right angle bend 46 therein. The arm 44 has a pivot pin 48 supported by bearings 50 so that movement of the iron armature 42 between the two electromagnets 32 moves the movable lens 14 in an arc representing the distance between the movable lens 14 and the pivot pin 48.

The left image and the right image are seen by alternating frames of the camera 10. The movable lens 14 remains motionless for the period when the exposure of the camera occurs. In the video embodiment the exposure time is 16.7 milliseconds or 33.3 milliseconds at the frame rate. The ratio of 0.5 milliseconds to 16.7 milliseconds defines a 3% duty cycle or at the frame rate of 1.5 duty cycle. It is essential that all switching occurs in this short period and the movable lens remains stationary for the balance. In the video embodiment the time between adjacent frames is approximately 0.5 milliseconds whereas in the motion picture the exposure time as stated is 16.7 milliseconds or 33.3 milliseconds at the frame rate. The time that the movable lens can be held in each of the positions is dependent upon the imaging system whether it be a film camera or a video camera.

For the embodiment shown in Figure 1, the focal distance of the movable lens 14 is bigger than the focal distance of the objective lens 12. In the case of an endoscope, the movable lens 14 is located at the exit pupil . The movable lens is designed to create good quality images in both extreme positions regarding optical axis and the video processor 22 aligns the images and corrects for aberrations caused by the lens movement.

The dimensions of the movable lens are chosen so that the two positions permit the right image and the left image to pass therethrough without reduction in intensity of illumination near the edges of the lens.

The movable lens may be fixed or variable focal length, i.e., zoom.

Whereas the imaging system has been illustrated with an endoscope, it may also be associated with a microscope or a telescope, and functions in the same way with a camera to provide left and right images synchronized to the left and right eye of a viewer.

Whereas good liquid crystal shuttered glasses are described as being a suitable stereoscopic viewing arrangement, there are other mechanisms available to differentiate at a viewer's eye between the left image and the right image and the present invention is not limited to any one of different types of stereoscopic viewing devices. Various changes may be made to the embodiments shown herein without departing from the scope of the present invention which is limited only by the following claims.

Claims

The embodiments of the present invention in which an exclusive property or privilege is claimed are defined as follows :

1. An imaging system for producing three dimensional images comprising:

a camera for viewing an object in an image path;

a movable lens positioned at a location in the image path between the object and the camera, the lens movable in the image path between a left position providing a left image in the image path and a right position providing a right image in the image path, the left image and the right image required for stereoscopic viewing;

means for moving the movable lens between the left position and the right position and retain the movable lens in each position for a sufficient time for the camera to view the left image and the right image individually;

stereoscopic viewing means to view the left image from the camera with one eye of a viewer and to view the right image from the camera with the other eye of the viewer, and

synchronization means to synchronize the means for moving the movable lens and control the stereoscopic viewing means so that the viewer sees only the left image with one eye and only the right image with the other eye.

2. The imaging system according to claim 1 wherein the movable lens is moved linearly from the left position to the right position.

3. The imaging system according to claim 1 wherein the movable lens is moved by rotating about an axis through the lens from the left position to the right position.

4. The imaging system according to claim 1 wherein the movable lens is moved through an arc between the left position and the right position.

5. The imaging system according to claim 1 wherein the camera is a video camera and the movable lens is located between an endoscope and an objective lens forming part of the camera.

6. The imaging system according to claim 5 wherein the movable lens is a long focus lens.

7. The imaging system according to claim 1 wherein the means for moving the movable lens is an electromechanical system.

8. The imaging system according to claim 1 including an objective lens positioned between the camera and the movable lens, and wherein the focal distance of the movable lens is greater than the focal distance of the objective lens.

9. The imaging system according to claim 1 wherein the means for moving the movable lens comprises two opposing electromagnets with dampers therebetween.

10. The imaging system according to claim 3 wherein the means for moving the movable lens comprises two opposing electromagnets with damper therebetween on both sides of an iron armature movable between the electromagnets, the iron armature being connected by an arm to an axis pin with bearing means thereon through the center of the lens, the electromagnets moving the armature from side to side such that the lens rotates between the left position and the right position.

11. The imaging system according to claim 4 wherein the means for moving the movable lens comprises two opposing electromagnets with dampers therebetween, the electromagnets positioned on both sides of an iron armature movable between the electromagnets, the iron armature being connected by an arm to the movable lens, the arm having a pivot position between the armature and the movable lens, the electromagnets moving the armature from side to side such that the movable lens moves in an arc between the left position and the right position.

12. The imaging system according to claim 1 wherein the means for moving the movable lens between the left position and the right position completes the movement within 0.5 milliseconds and wherein the movable lens is retained stationary in each position for a time representing exposure of a frame for the camera.

13. The imaging system according to claim 1 wherein the camera is a video camera and wherein the synchronization means synchronizes the means for moving the movable lens with a vertical retrace in the video camera representing a frame change.

14. The imaging system according to claim 1 wherein the camera is a film camera and wherein the synchronization means synchronizes the means for moving the movable lens with a gate advance for a film in the film camera representing a frame change.

15. The imaging system according to claim 1 wherein a two dimensional lens system is positioned in the image path between the movable lens and the object, the two dimensional lens system selected from the group consisting of an endoscope, a microscope and a telescope.

16. The imaging system according to claim 1 wherein the movable lens is associated with a variable focal length lens system.

17. The imaging system according to claim 1 wherein the movable lens is associated with a fixed focal length lens system.

18. A method of stereoscopic viewing an object comprising the steps of:

positioning a movable lens at a location in an image path between the object and a camera;

moving the movable lens in the image path between a left position providing a left image in the image path and a right position providing a right image in the image path, the left image and the right image required for stereoscopic viewing;

retaining the movable lens in the left position and the right position for a sufficient time for the camera to view the left image and the right image individually, and

synchronizing alternately the left image and the right image on the camera with stereoscopic viewing means so that a viewer sees only the left image with one eye and only the right image with the other eye.

19. The method of stereoscopic viewing according to claim 18 wherein the movable lens is moved linearly between the left position and the right position.

20. The method of stereoscopic viewing according to claim 18 wherein the movable lens is rotated about an axis between the left position and the right position.

21. The method of stereoscopic viewing according to claim 18 wherein the movable lens is moved through an arc between the left position and the right position.

22. The method of stereoscopic viewing according to claim 18 wherein the camera is a video camera and wherein movement of the movable lens is synchronized with a vertical retrace representing a frame change in the video camera.

23. The method of stereoscopic viewing according to claim 18 wherein the camera is a film camera and wherein movement of the movable lens is synchronized with a gate advance for a film in the film camera representing a frame change.

24. The method of stereoscopic viewing according to claim 18 wherein the movable lens is moved in the image path from being stationary in either the left position or the right position to being stationary in the other position within 0.5 milliseconds.

25. The method of stereoscopic viewing according to claim 18 wherein the stereoscopic viewing means comprises active eyewear with a left viewing eyepiece and a right viewing eyepiece that become opaque and wherein the eyewear is synchronized with the movement of the movable lens so that one eye sees the left image and the other eye sees the right image.

26. The method of stereoscopic viewing according to claim 18 wherein a two dimensional lens system is positioned in the image path between the movable lens and the object.

27. The method of stereoscopic viewing according to claim 26 wherein the two dimensional lens system is selected from the group consisting of an endoscope, a microscope and a telescope.

28. The method of stereoscopic viewing according to claim 19 wherein the movable lens is associated with a variable focal length lens system.

29. The method of stereoscopic viewing according to claim 19 wherein the movable lens is associated with a fixed focal length system.