Optics: image projectors – Stereoscopic
Reexamination Certificate
2001-11-13
2003-01-28
Dowling, William (Department: 2851)
Optics: image projectors
Stereoscopic
C359S472000
Reexamination Certificate
active
06511182
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to autostereoscopic display systems for viewing electronically generated images and more particularly relates to an apparatus and method for generating left- and right-eye images using a scanned linear image source with a monocentric arrangement of optical components to provide a very wide field of view and large exit pupils.
BACKGROUND OF THE INVENTION
The potential value of autostereoscopic display systems is widely appreciated particularly in entertainment and simulation fields. Autostereoscopic display systems include “immersion” systems, intended to provide a realistic viewing experience for an observer by visually surrounding the observer with a 3-D image having a very wide field of view. As differentiated from the larger group of stereoscopic displays that include it, the autostereoscopic display is characterized by the absence of any requirement for a wearable item of any type, such as, for example, goggles, headgear, or special glasses. That is, an autostereoscopic display attempts to provide “natural” viewing conditions for an observer.
In an article in
SID
99
Digest
, “Autostereoscopic Properties of Spherical Panoramic Virtual Displays,” G. J. Kintz discloses one approach to providing autostereoscopic display with a wide field of view. Using the Kintz approach, no glasses or headgear are required. However, the observer's head must be positioned within a rapidly rotating spherical shell having arrays of LED emitters, imaged by a monocentric mirror, to form a collimated virtual image. Monocentric optical systems are characterized in that all optical surfaces share a common axis of symmetry. It is a generalization of the concentric system in which all optical surfaces share a common center of curvature at a single point. While the Kintz design provides one solution for a truly autostereoscopic system having a wide field of view, this design has considerable drawbacks. Among the disadvantages of the Kintz design is the requirement that the observer's head be in close proximity to a rapidly spinning surface. Such an approach requires measures to minimize the likelihood of accident and injury from contact with components on the spinning surface. Even with protective shielding, proximity to a rapidly moving surface could, at the least, cause the observer some apprehension. In addition, use of such a system imposes considerable constraints on head movement.
One class of autostereoscopic systems that operates by imaging the exit pupils of a pair of projectors onto the eyes of an observer is as outlined in an article by S. A. Benton, T. E. Slowe, A. B. Kropp, and S. L. Smith (“Micropolarizer-based multiple-viewer autostereoscopic display,” in
Stereoscopic Displays and Virtual Reality Systems
VI, SPIE, January, 1999). Pupil imaging, as outlined by Benton in the above-mentioned article, can be implemented using large lenses or mirrors. An observer whose eyes are coincident with the imaged pupils can view a stereoscopic scene without crosstalk, without wearing eyewear of any kind.
It can be readily appreciated that the value and realistic quality of the viewing experience provided by an autostereoscopic display system using pupil imaging is enhanced by presenting the 3-D image with a wide field of view and large exit pupil. Such a system is most effective for immersive viewing functions if it allows an observer to be comfortably seated, without constraining head movement to within a tight tolerance and without requiring the observer to wear goggles or other device. For fully satisfactory 3-D viewing, such a system should provide separate, high-resolution images to right and left eyes. It can also be readily appreciated that such a system is most favorably designed for compactness, to create an illusion of depth and width of field, while occupying as little actual floor space and volume as is possible. For the most realistic viewing experience, the observer should be presented with a virtual image, disposed to appear a large distance away.
It is also known that conflict between depth cues associated with vergence and accommodation can adversely impact the viewing experience. Vergence refers to the degree at which the observer's eyes must be crossed in order to fuse the separate images of an object within the field of view. Vergence decreases, then vanishes as viewed objects become more distant. Accommodation refers to the requirement that the eye lens of the observer change shape to maintain retinal focus for the object of interest. It is known that there can be a temporary degradation of the observer's depth perception when the observer is exposed for a period of time to mismatched depth cues for vergence and accommodation. It is also known that this negative effect on depth perception can be mitigated when the accommodation cues correspond to distant image position.
An example of a conventional autostereoscopic display unit is disclosed in U.S. Pat. No. 5,671,992 (Richards), at which a seated observer experiences apparent 3-D visual effects created using images generated from separate projectors, one for each eye, and directed to the observer using an imaging system comprising a number of mirrors.
Conventional solutions for stereoscopic imaging have addressed some of the challenges noted above, but there is room for improvement. For example, some early stereoscopic systems employed special headwear, goggles, or eyeglasses to provide the 3-D viewing experience. As just one example of such a system, U.S. Pat. No. 6,034,717 (Dentingeret al.) discloses aprojection display system requiring an observer to wear a set of passive polarizing glasses in order to selectively direct the appropriate image to each eye for creating a 3-D effect.
Certainly, there are some situations for which headgear of some kind can be considered appropriate for stereoscopic viewing, such as with simulation applications. For such an application, U.S. Pat. No. 5,572,229 (Fisher) discloses a projection display headgear that provides stereoscopic viewing with a wide field of view. However, where possible, there are advantages to providing autostereoscopic viewing, in which an observer is not required to wear any type of device, as was disclosed in the device of U.S. Pat. No. 5,671,992. It would also be advantageous to allow some degree of freedom for head movement. In contrast, U.S. Pat. No. 5,908,300 (Walker et al.) discloses a hang-gliding simulation system in which an observer's head is maintained in a fixed position. While such a solution may be tolerable in the limited simulation environment disclosed in the Walker et al. patent, and may simplify the overall optical design of an apparatus, constraint of head movement would be a disadvantage in an immersion system. Notably, the system disclosed in the Walker et al. patent employs a narrow viewing aperture, effectively limiting the field of view. Complex, conventional projection lenses, disposed in an off-axis orientation, are employed in the device disclosed in U.S. Pat. No. 5,908,300, with scaling used to obtain the desired output pupil size.
A number of systems have been developed to provide stereoscopic effects by presenting to the observer the combined image, through a beamsplitter, of two screens at two different distances from the observer, thereby creating the illusion of stereoscopic imaging, as is disclosed in U.S. Pat. No. 5,255,028 (Biles). However, this type of system is limited to small viewing angles and is, therefore, not suitable for providing an immersive viewing experience. In addition, images displayed using such a system are real images, presented at close proximity to the observer, and thus likely to introduce the vergence/accommodation problems noted above.
It is generally recognized that, in order to minimize vergence/accommodation effects, a 3-D viewing system should display its pair of stereoscopic images, whether real or virtual, at a relatively large distance from the observer. For real images, this means that a large display screen must be emplo
Agostinelli John A.
Kessler David
Blish Nelson Adrian
Dowling William
Eastman Kodak Company
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