Optics: image projectors – Stereoscopic – Polarizer
Reexamination Certificate
1999-04-06
2001-04-24
Dowling, William (Department: 2851)
Optics: image projectors
Stereoscopic
Polarizer
C359S464000
Reexamination Certificate
active
06220709
ABSTRACT:
The invention has to do with a system for projecting pictorial representations, in particular 3D images, onto a viewing device in accordance with the general description given in claim
1
.
Three-dimensional objects are frequently represented on a viewing device as two-dimensional images, for which the viewing angle and position of the viewer relative to the stationary projection screen determine the aspect of the object presented by the image at a particular time. This requires that the location of the viewer relative to the screen be ascertained in spatial coordinates by appropriate sensors, and that the representation on the screen be suitably calculated and adjusted by an appropriate tracking system. When such a procedure is employed, and when a single projection screen is used, only one viewer at a time can see a representation of the object on the screen corresponding to that viewer's position; other viewers see a distorted image.
With a different procedure for viewing an object that is virtually stationary in space, one projection screen is assigned to a particular viewer, and remains so assigned for the duration of the viewing. The position of the viewer at any given time is registered by the tracking system, and anytime the viewer's position changes, the representation of the object is calculated and displayed afresh in real time as a function of the location and the viewing angle of the viewer. Such a system generally employs a helmet having viewing devices which are placed in direct relationship with the viewer's eyes, e.g., a LCD screen. However, such helmets are unwieldy and moreover can be used only by a single viewer. Furthermore, the viewer's natural environment cannot easily be included in the representation provided by such a helmet. When this kind of procedure is employed, though, the tracking system can also analyze the screen's position and the direction in which the screen is presenting the image, making a helmet unnecessary. There is still only a single representation on the screen, however.
A true stereoscopic projection makes possible more detailed views of spatial relationships. For example, forms and shaped parts, or working parts, can be represented in detail with lights and shadows. When it is a matter of a real-time representation that is derived from a computer, the visual appearance of the object can be directly modified.
To achieve a true stereoscopic representation of an image by projection onto a canvas projection screen or by display on a video projection screen, in the main two procedures are used that require employment of spectacles whose lenses function as image separators and which make it possible to make different image data available to the right eye and to the left eye.
In the case of the passive procedure, the lenses of the spectacles are polarized differently; for example, at an angle of 90° to each other or circularly in opposite directions. The image shown on the canvas projection screen must be polarized in a corresponding fashion. This can be achieved, for example, by using projectors having polarization orientations that are different for the right and the left representation of the object.
For the active procedure, no polarization filters are required. Instead, the separation of the images is effected by means of sequential representation of the image data assigned to the left and the right eye. Through a synchronous tracking system, LC spectacles (shutter-lens spectacles) are switched over in the same rhythm so that the viewer can perceive with each eye only the image information assigned to that eye. The clock-pulse frequency of the switching determines the degree to which the viewer sees a flickering.
With regard to both the passive and the active forms of this technique, one or several persons can apprehend at the same time only the same information. If, for example, stereoscopic representations of work routines and operations are wanted, in order to convey to the viewer a stereoscopic image of a certain phase space coordinated with the viewer's physical location, and if it is also desired that the phase space coordinated with a second person's position be shown to this second person, and if the two images of the phase space are different, then it is undesirable that the same 3D image be shown to both viewers.
A representation of an object corresponding to its natural appearance, and one that allows several viewers to perceive different aspects of the object, can be achieved at the present time only with a holographic representation. A real-time representation of objects of considerable size, e.g., of an automobile, that permits modification of the object, is not yet possible, however, and does not appear to be even conceivable in the foreseeable future.
A system for displaying two different images in the form of 2D representations on a single viewing device is known from U.S. Pat. No. 4,879,603. The displays for separate viewers are separated from one another by image-separating devices consisting of circular polarizers. The resulting image is not a stereoscopic one.
EP-A-O 656 555 presents a projection system for 3D representations that enables a viewer to see a 3D image. In this system, two projection screens are used which effect a right/left separation by means of a system of mirrors. These two 3D images are separated in a manner taking into account the viewer's position. This is done by using extraordinarily complicated lighting devices or lenticular assemblies. Each stereoscopic image is coordinated with just one single position (which can be changed only slightly), which can be occupied by only a single viewer at a time.
The invention is intended to provide a system for projecting non-holographic 3D representations, in particular stereoscopic images, onto a viewing device, with the aid of which system the simultaneous representation of different image contents, approximating a holographic representation, for several viewers is possible,
This purpose is fulfilled by the invention described in claim
1
. Modified forms of the invention offering advantages are described in sub-claims.
The invention consists of a system for projecting non-holographic 3D images onto a viewing device. In this system, the images assigned to the viewer's eyes are brought into relationship with the viewer's position at a particular time by sensors which are assigned to the viewer, and which ascertain the viewer's position at a given time, and by the display on the viewing device of an object whose virtual spatial positioning corresponds to the viewer's standpoint. For the purpose of simultaneous perception of different 3D images on the same viewing device by several viewers, several different images that are coordinated with the various locations of the viewers are displayed simultaneously. Image-separating devices are assigned to the several viewers, by means of which each viewer has access only to the images that are coordinated with that particular viewer's position. For stereoscopic viewing of the object, two 3D images, which are separated by image separators and assigned to a viewer's right and left eyes, are provided to each viewer.
With the aid of the system in question, it is possible for a number of viewers to view an object on the viewing device from different positions simultaneously, with the viewing angle of each person corresponding to the actual viewing angle of the virtually stationary object. It is therefore possible for one person to view a certain aspect of the object, while at the same time another person is seeing a different detail of the object.
The images assigned to the several viewers can be displayed sequentially in time. The image-separating devices are in that case shutter-lens spectacles that are synchronized with the images; the shutter lenses of a particular viewer allow passage of the projected light only when the image assigned to that particular viewer is displayed.
In an alternate embodiment of the invention, the images assigned to t
Dowling William
Feix Thomas C.
Helmut Tan
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