Patent Application
20050243418
Not Applicable
Not Applicable
1. Field of Invention
This invention relates to stereoscopes, and more specifically to stereoscopes that include a twin-lens eyepiece connected to a holder for a stereogram. This invention applies to stereograms that are composed of two adjacent images, or fields, each corresponding to one eye. A stereogram is understood as a stereoscopic image generated by any method, and a stereograph more specifically as a photographic stereogram, these two words being used interchangeably herein.
2. Description of Prior Art
Our perception of depth in our surroundings comes from many visual cues, an important one being the parallax of the two similar but non-identical images seen by our two eyes. A stereograph presents two views of a scene that incorporate a shift in viewpoint parallel to the line joining the centers of the two images, not necessarily in a horizontal plane and not necessarily by the same distance as separates human eyes, such that when each view is exclusively presented to its corresponding eye, the two fields are fused into a realistic three-dimensional perception of the scene. If a stereograph is configured so that when held up for viewing, the left image squarely faces the left eye while the right image squarely faces the right eye, the 3-D picture can be free-viewed by a trained user maintaining a parallel gaze while accommodating his sight to the plane of the images. The illusion of depth afforded by a properly formatted stereogram can thus be appreciated with nothing more than a pair of naked eyes with adequate vision.
There are, however, serious limitations associated with this method of enjoying a stereo picture. First, many people find it difficult or impossible to maintain parallel lines of sight while focusing on a near object. Second, a stereo pair viewed in this manner appears as three distinct images, the three-dimensional one in the center being flanked on both sides by distracting flat counterparts. Third, since our eyes cannot be made to diverge to any significant extent, a stereo pair configured for such use is necessarily limited to a maximum field separation substantially equal to the interpupillary distance, approximately 6.5 cm (2.5 in). This also limits the width of the 3-D image to 6.5 cm which, at a comfortable minimum viewing distance of 25 cm (10 in), represents a horizontal angular field of view of only 15 degrees. Though practicable, free-viewing is therefore unsatisfying and fails to exploit the full potential of third dimensional representation possible with a pair of 2-D images.
According to historical references, stereoscopy predates photography: Wheatstone invented the stereoscope in 1838 using an arrangement of mirrors to view stereograms, just one year before photography was developed by Daguerre. The stereoscope without mirrors was proposed by Brewster, and Holmes improved on the concept by using lenses off-center to act as prisms. Many improvements have been made over the years to advance the art of 3-D representation from twin 2-D pictures.
A straightforward solution to the limitations cited above is accomplished with the lorgnette type of stereo viewer, as exemplified by U.S. Pat. No. 2,849,917 to Petri, 1953 May 29. A pair of convergent lenses is held in front of the eyes and the stereograph is placed a focal distance away. This brings the physical image closer while pushing its virtual counterpart out to infinity, thereby facilitating visual accommodation while also increasing the angular field of view. The nasal side of each lens is frosted to act as an optical septum, blocking out of each eyeview the distracting contralateral field. In addition, the lenses are configured in a base-out prism geometry, allowing the lines of sight to diverge, thereby enabling the use of larger images, and further amplifying the field of view. While simple and inexpensive, this handheld device suffers from a lack of steady support of the stereograph for alignment with the eyepiece, rendering its operation difficult for many users.
U.S. Pat. No. 4,730,898 to Curtin, 1988 Mar. 15, shows a viewer of the same type, but of a more complex construction, including appendages allowing it to be worn like a pair of eyeglasses. This apparatus uses lens fragments of a smaller size to limit the field of view and eliminate the need for a septum, but still does not adequately address the problem of securely squaring the viewer and the view. U.S. Pat. No. 4,172,633 to Hashimoto et al., 1979 Oct. 30, shows a viewer that can be thought of as a lorgnette-type stereoscope fitted with panels, including a septum, designed to keep it at a predetermined distance from a stereographic target, with the eyepiece held in a parallel configuration. This device is advantageous for viewing either 3-D images displayed in a book or stereoscopic pictures lying flat on a surface, with a simple provision for adjusting interocular distance, but is not adapted for holding a card in position.
The secure, square holding problem is addressed explicitly by the class of stereoscopes that include both a 3-D eyepiece and a mounting system for the stereograph, some early examples of which include the view box shown in U.S. Pat. No. 61,359 to Rawson, 1867 Jan. 22, the stereoscopic book of U.S. Pat. No. 174,893 to Bierstadt, 1876 Mar. 21, and the parlor-style stereoscope of U.S. Pat. No. 262,846 to Stevens, 1882 Aug. 15. Stereoscope design shows a height of sophistication and complexity with the slide viewing apparatus of U.S. Pat. No. 2,484,591 to Rochwite, 1945 May 8, which incorporates a light source and provides mechanisms for adjustment of focus and interocular distance, in a closed, injection-molded body. On the other hand, the relatively simple, binoculars-like slide viewer of U.S. Pat. No. 2,511,334 to Gruber, 1947 Apr. 28, includes a mechanism for manually cycling through seven pairs of slides mounted on a disc, with the title of the current view showing through a window. This design, marketed as the ViewMaster®, has encountered great commercial success and is currently the only stereoscope that is widely available to the general public. However, this device is presented and regarded as a child's toy, and there is no accessible way for a user to make her own stereo slides to view with it. Moreover, the available images cannot be enjoyed independently of the viewer. A recent update of the ViewMaster®, shown in U.S. Pat. No. 6,031,662 to Miller et al., 2000 Feb. 29, suffers from the same limitations but can serve as binoculars.
Other designs can be found in the prior art. Some improvements emphasize the incorporation of a large amount of content in the fashion of a book, such as U.S. Pat. No. 2,616,333 to Tinker, 1952 Nov. 4; U.S. Pat. No. 5,204,776 to Seamans and Harvey, 1993 Apr. 20; and U.S. Pat. No. 6,456,433 to Jones, 2002 Sep. 24. These specialized devices have relatively complex designs and require multiple steps in their manufacture. The Jones patent shows provisions for synchronized adjustment of interocular distance.
Others improvements stress portability in a collapsible arrangement, such as U.S. Pat. No. 2,724,991 to Levine, 1955 Nov. 29; U.S. Pat. No. 5,002,363 to Tanaka, 1991 Mar. 26; U.S. Pat. No. 5,136,423 to Curtin, 1992 Aug. 4; and U.S. Pat. No. 5,940,210 to Kassawat, 1999 Aug. 17. These viewers range from the simplest, such as Tanaka's, to the most complicated, such as Kassawat's, but all are compact, efficient and inexpensive. However, they lack adjustment capability and their general appearance matches their low cost. Kassawat's and some of Curtin's embodiments follow the ViewMaster® design philosophy, relying on an assemblage of walls, windows and septa to corral the user's sight from each eye onto the desired area of space. While this technique incrementally facilitates stereo viewing, it interferes with the visibility of the picture with respect to a bystanding observer, and detracts from the display value of the stereoscope.
The prismatic Holmes stereoscope continues to be improved upon and updated, as exemplified by U.S. Pat. No. 4,789,220 to Kinnard, 1987 Apr. 24; and U.S. Pat. No. 5,058,990 to Bush, 1991 Oct. 22. The Kinnard invention is foldable and adjustable in many dimensions, but, like the ViewMaster®, uses a proprietary format for the stereogram. Its complex mechanical versatility encompasses reconfiguration as a dual-power magnifier. The Bush invention is assembled from substantially flat, easily fabricated interlocking pieces, and can be readily separated into its components for compact transport. However, adjustability is absent and the instrument has to be partially disassembled in order to change the view. A limitation common to septated stereoscopes is the difficulty in evenly lighting the stereograph.
Stereophotography was widely practiced and appreciated in the late nineteenth and the early twentieth centuries, and along with stereographs, stereoscopes enjoyed wide distribution and use. Nowadays, the field of stereoscopy is dormant and the art is practiced mostly by a small niche of aficionados catered to by a handful of specialized websites. Aside from the ViewMaster®, no other stereoscope is readily available to the public. As consumer interest surges for digital cameras, and the means for generating and printing high-resolution color images become more available and affordable at the personal computing level, photography in general is thriving while stereography is withering. There exists no accessible way for the average person to engage in creating, viewing and exhibiting quality stereographs of friends and family. Even though the science is well-known, the art has not kept up with advancing technology and evolving tastes. The stereoscope is now perceived as either a child's toy or a relic from the past, its vast potential for amusing, teaching and inspiring ignored. The adjustable stereoscopic display system of this invention is intended to help advance the art.
Accordingly, several objects and advantages of the present invention are to provide:
(a) a self-standing display system for stereoscopic visual content that securely holds, supports, protects, and exhibits the content material, and is adapted for stable upright setting on a horizontal surface, or optional mounting on a vertical or slanted surface;
(b) an aesthetically pleasing stereoscopic display that has a clean, uncluttered, stylish and modern appearance, is suitable for use as a decorative object, and has wide appeal for people of various ages and interests in a home or place of business;
(c) an easy to use stereoscopic apparatus that has a simple design with an intuitive operation of the various adjustment mechanisms, and requires a minimum amount of effort, skill or care on the part of the user;
(d) a practical stereoscope that fits a large proportion of the people who have adequate binocular eyesight, providing adjustable interocular distance, focus, and diopter compensation, as well as compensation for vertical misalignment of stereofields;
(e) a customizable 3D optical viewer with easily removed and interchangeable lenses, allowing for individualization to a user's vision requirements;
(f) a versatile stereoscopic display system that is optimized to accept various formats of stereograms, in print, transparency, slide, LCD or other thin media form, either permanently mounted or configured as loose stereo pairs or montages;
(g) an accessible stereoscopy method whereby an average person can make, view and show her own stereographic creations without requiring specialized stereo cameras or image processing equipment;
(h) an adaptable display system capable of securely holding two pictures facing opposite directions, as well as receiving a temporary stereo image for transient viewing;
(i) an economical and environmentally friendly stereoscopic display that maximally uses ambient light and requires no special source of light or energy to operate;
(j) a lightweight yet robust three-dimensional viewing apparatus that is readily handled by adults and children alike, being economical of material while not easily rendered inoperable;
(k) an easy to manufacture 3-D optical device of simple construction with a minimum number of parts;
(l) a simple and inexpensive stereoscopic display system suitable for adoption by a wide segment of the general public, marketable as a natural extension of existing photographic product lines in retail stores, and applicable for entertainment as well as education.
Further objects and advantages of the present invention will become apparent from a consideration of the ensuing description and drawings.
In accordance with the present invention, an exemplary preferred embodiment stereoscopic display system is made from three parts: an elongated rectangular sheet of thin, transparent plastic and two convergent lenses. The transparent sheet, which constitutes the body of the stereoscope, is formed through four parallel folds into three rectangular sections: a single-layer base in the middle, a double-layer picture holder on one end, and a double-layer lens holder on the other end. The end sections are each connected to the base through a 90 degree fold and are of equal size, perpendicular to the base, and parallel to and directly facing each other, separated by a distance equal to the focal length of the lenses.
The picture holder section has two layers, or walls, of the transparent material, connected through a 180 degree fold, and accepts two pictures inserted between these walls: a stereograph facing the lenses through the internal wall, and another image facing the other direction through the external wall, both of which being removable by slight separation of the two walls. A single stereo transparency or slide can also be installed in the picture holder, to be viewed against an external light source. A cylindrical fold at the free edge of the picture holder provides a channel to temporarily retain a picture for transient viewing. A stereogram mounted in this channel is not limited by the size and format of the picture holder. Alternately, a pair of sidewings on the internal wall serves the same purpose, albeit with width limitation.
The lens holder section also has two walls connected through a 180-degree fold, and accepts the two lenses. Each lens has a peripheral flange that is held between the walls, and an optically active body that is received in matching cutouts in those walls. The lenses are symmetrically disposed about the longitudinal axis of the body, spaced 6.35 cm (2.5 in) apart, and can be inserted and removed by slightly separating the two walls. The user can opt to install corrective lenses provided as an accessory. A removable septum facilitates stereo viewing by untrained eyes.
A median slot runs from the distal edge of the lens holder section down through this entire section and onto the adjacent part of the base, up to the center of the base. The lens holder and half of the base are thus divided into two symmetrical lens support arms. The median slot is so shaped as to accommodate the user's nose when the lenses are placed against the eyes, and also to provide clearance for the resilient approximation of the lens support arms. Adjustments for variations in focus, diopter, and interpupillary or stereofield separation, as well as vertical field alignment, are done by flexing the lens support arms together or separately in longitudinal and transverse directions.
Alternately, elongated lens apertures in the walls allow the lenses to slide closer together or farther apart for durable setting of the lens separation, i.e. interocular distance, to match the user's interpupillary distance and the stereogram's field separation. Lateral flexing of the lens support arms is then needed only as a fine-tuning process. Optionally, each lens is provided with a pivot pin and an adjustment tab that protrude respectively from the bottom and top parts of the flange and are received in matching wall cutouts, allowing the user to set the lens separation without touching the lenses.
In an alternate embodiment, in which durable setting of interocular distance is provided for as above, the complete slotting of the lens holder section into two separate arms is omitted. The nose slot then has to extend only as far as needed to accommodate the nose, leaving the nasal bridge intact and encroaching less deeply into the base, resulting in a sturdier structure but allowing instant resilient adjustment for focus only.
Drawing Figures
In the drawings, closely related figures have the same number but different alphabetic suffixes.
In the reference numerals, suffixes A and B on a numeral respectively designate homologous left and right parts, which may also be referred to collectively by the same numeral without suffixes.
The lens and lens aperture configurations depicted in
Another embodiment of stereoscope 10, not pictured, is formed from a single piece of plastic with the lenses molded in place, obviating the need for a lens holder flap. This unitary construction cleans the style and simplifies the fabrication of the device at the expense of lens interchangeability.
Operation
The user inserts a stereograph between picture holder panel 28 and flap 24, and views it stereoscopically through lenses 14. The sheet material is flexible and adjustment of the focus may be made by bending lens holder 20 closer to or farther away from picture holder 18. Diopter correction can be made by differentially bending lens holders 20A and 20B. Interocular adjustment can be done by bending these holders in the transverse plane. Adjustment for vertical field alignment is done by flexing holders upward and downward. These maneuvers come naturally and intuitively as the user holds the flexible device in his hands and attempts to see a comfortable 3D image, and even when no correction is finally need, the variation of lens position in a searching manner helps the eyes settle into the proper viewing posture. The optional septum 72 may be installed to help an uninitiated user channel his gaze in the correct direction.
Lenses can easily pop out for cleaning or for replacement with others that suit the vision correction needs of the user. The use of resilient, transparent sheet plastic gives the design a clean and simple appearance, allowing maximum ambient light to fall on the picture while keeping cost to a minimum. The stereoscopic display has a decorative character making it suitable for use as a prominent decoration on a desk, mantle or coffee table.
The stereographic image for use with this device can come either in the form of a pre-aligned and mounted set, or as a loose pair of pictures that are matched in the proper stereoscopic relationship, each image being installed on its respective side of the picture holder. The construction of the picture holder enables the user to insert two separate views on the left and right side, such as taken by two separate cameras disposed in the proper relationship for stereophotography, obviating the need to employ specially constructed stereo cameras or specially prepared stereo views. For still scenes, one camera can be used to generate both views, one taken in a displaced position from the other. For moving subjects, two cameras are used, with simultaneous activation of the shutters from two different positions. The resulting prints are then trimmed to the proper size for sliding into the picture holder.
Another picture, preferably monoscopic, may be inserted facing the other side of the picture holder, so that when the display is placed on a desk, people seated on both sides may enjoy the sight of a picture. For transient viewing of a series of stereographs, these can be rested against the wall of the picture holder facing the lenses, loosely retained by the sidewings or edge channel. If the picture holder flap is fabricated in the form of two halves attached to the lateral sides of the picture holder panel and pressing against its backside, a roll of cartoon stereograms arranged on top of one another can be readily fed through vertically for rapid sequential viewing.
Thus, the reader will see that the present invention provides a simple, versatile, practical, and adjustable stereoscopic display that is inexpensive to manufacture and can be used by people of various ages and with differing interests. While the above description contains many specificities, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of preferred embodiments thereof. Many other variations are possible. For example, the lens holder flaps may fold in from the sides instead of the top, or the lens holder may be connected to the picture holder by sidearms instead of a base. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.
