Optics: image projectors – Stereoscopic
Reexamination Certificate
2002-03-19
2003-04-22
Dowling, William (Department: 2851)
Optics: image projectors
Stereoscopic
C353S010000
Reexamination Certificate
active
06550918
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 resonant fiber-optic member to form an image, with a monocentric arrangement of optical components including a retro-reflective surface 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 three-dimensional (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 goggles, headgear, or special glasses, for example. 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 light emitting diodes (LEDs), imaged by a monocentric mirror, to form a collimated virtual image. 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 devices. 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.
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 and a retro-reflective surface. The apparatus disclosed in U.S. Pat. No. 5,671,992 does not provide a wide-field of view, however, which would be advantageous for immersive autostereoscopic display, as noted above.
Other uses of retro-reflective surfaces for autostereoscopic imaging are disclosed in U.S. Pat. Nos. 5,572,363 and 5,629,806 (both to Fergason). The Fergason patents disclose in-line and folded optical path arrangements using a retro-reflective surface and beamsplitter that cooperate to enlarge an image projected from a relatively small image source in order to provide, at a viewing pupil, a real image formed on the retro-reflective surface of the device. In the approach disclosed in the Fergason patents, the viewing pupil is a pseudo-image of the exit pupil of the projection lens. A large viewing pupil with wide field of view are preferred for ease of viewing; however, in order to form a large viewing pupil using conventional wide-field lenses, the apparatus disclosed in U.S. Pat. Nos. 5,572,363 or 5,629,806 requires a low-gain retro-reflective screen. But such low-gain retro-reflective screens have disadvantages including reduced brightness and, due to gain profile characteristics, increased crosstalk between left- and right-eye images. Constrained by the need to provide a large viewing pupil given a small projector lens exit pupil, then, devices using low-gain retro-reflective surfaces tend to compromise on image quality. As was a drawback of the apparatus using a retro-reflective surface disclosed in U.S. Pat. No. 5,671,992, the apparatus disclosed in U.S. Pat. Nos. 5,572,363 and 5,629,806 do not provide wide field of view.
Conventional solutions for stereoscopic imaging have addressed some of the challenges for inexpensively providing wide field of view with high brightness, 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 (Dentinger et al.) discloses a projection 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 specific 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 exit 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 creat
Agostinelli John A.
Cobb Joshua M.
Dowling William
Nelson Adrian Blish
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