Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Reexamination Certificate
2000-06-15
2003-07-15
Mack, Ricky (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
C359S626000
Reexamination Certificate
active
06594083
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to imaging and, more particularly, to lenticular imaging systems. A particularly important aspect of the invention relates to optical reimaging of lenticular cards to produce real floating lenticular images without loss of desirable lenticular properties, such as the ability to produce the appearance of multi-frame action or three-dimensional images throughout complete image frames without multi-frame confusion.
Three-dimensional and/or floating image visual effects may be created by known holographic techniques, floating image projectors, handheld stereoscopic slide viewers, slide or movie projectors, and lenticular cards (transmissive or reflective types) for motion and/or three-dimensional (3D) simulation. Lenticular cards in the prior art are designed for unaided viewing and are typically located at arm's length or beyond, at normal viewing distances from the eye. Such prior art lenticulars provide unsatisfactory images when they are projected or otherwise optically reimaged. In particular, ordinary lenticular objects reimaged by ordinary optical systems are severely limited in full-frame image capability, especially in the compact and optically powerful configuration necessary for hand-held floating image projectors.
A need exists for lenticular imaging systems and methods for producing lenticular cards and other products which provide improved images when optically reimaged.
Prior art lenticular cards and transparencies are designed for direct viewing. In the most common fabrication process, multiple image frames are selected and collated in the desired viewing order, then lines of data from each in turn are printed in successive strips oriented parallel to the lenticular cylindrical axis. Data strips from (for example) the bottom of each frame are printed behind the bottom cylindrical lenslet, or “lenticule”, of the lenticular lens, and this process is iterated for all successive frame sections and lenticules until the appropriate data from all frame regions is printed behind the array of lenticules. This process is known as “interlacing”. Each lenticule is associated with the same number of data strips as the number of frames, and each lenslet projects images of each of its associated strips at different angles, as shown in
FIGS. 1-2
. Equivalent direct imaging fabrication processes are also possible.
The picture elements or “pixels” that make up each image frame consist of the variegated data (e.g., density, color, etc.) printed within each strip parallel to the lenticular cylindrical axis, combined with the independently variegated data printed perpendicular to that axis in the other corresponding strips associated with successive lenticules. With i data strips per lenticule corresponding to i image frames, and with y lenticules covering each data frame and x independent pixels in each data strip, the product xy represents the total number of pixels in each frame, and the product ixy is the total number of pixels printed in the entire ensemble of i frames.
Interlacing of the i data strips behind each lenticule follows essentially identical local mapping patterns throughout the lenticular. This results in iy image beams at i different angles for each orthogonal x-location.
FIGS. 1 and 2
clarify this prior art.
Referring to the example of
FIG. 1
, the eye observes the top, center, and bottom of one section of an action-type lenticular in viewing a single frame, utilizing light that exits individual lenslets at different angles, depending on each pixel's location within the frame. Such prior art lenticulars have their data strips interlaced such that an image beam from the strip corresponding to the top of the desired image frame is optically projected (typically but not necessarily at infinite conjugates) by the uppermost lenticule at an angle &agr; to the optical axis (&agr; in
FIG. 1
) that corresponds to the angle required for the observer's eye to see the top of the desired frame. Similarly, data strips for the center, bottom, and all other regions of that frame are printed at the proper locations behind their associated lenticules such that their image beams are projected at the other angles appropriate for the observer's eye to view those frame regions. As a result, all such image beams for a single frame are projected by the lenticular lens (the ensemble of all parallel lenticules) so that they intersect at the nominal eye location, as shown in FIG.
1
. The observer therefore sees only the data from the data strips corresponding to the desired frame; the other data strip images are projected either above or below the eye in this example.
FIG. 2
illustrates a view of one individual lenslet, showing an example of how information corresponding to various frames is printed at each pixel location. Frame
1
data, for example, can be printed at a height h above the local lenticule axis, which relates to the focusing distance f (typically near or equal to the lenticule's focal length), such that h=f tan &agr;. This example could therefore correspond to the topmost lenticule in
FIG. 1
, projecting the topmost frame data toward the observer at angle &agr;.
Moving the eye or moving/tilting the lenticular then allows successive frame data strip contributions from the various angles to be seen at each frame location. Thus, printing the appropriate multi-frame information within each pixel of the card or transparency produces the desired illusion (e.g., of motion, stereoscopic pairing, other action such as “morphing”, or other desired effect) as the observer's viewpoint changes. Note that while the examples of
FIGS. 1 and 2
have been discussed in terms of “action-type” lenticulars with nominally horizontal lenticule axes, the principles are equally valid for “3D” type lenticulars, in which the lenticule axes are nominally vertical, and in which selectively paired stereoscopic images are presented to the observer's left and right eyes. (“Top/bottom” references would then be changed to “left/right”.)
Prior art lenticulars are optimized for unaided viewing. Thus, subsequent optical reimaging of such lenticulars necessarily alters the angular distribution of rays reaching the eye, with the effect of making truncated portions of several image frames visible simultaneously, thereby resulting in unintended confusion between frames. This typically truncates the effective angular size of a full frame as observed, since only part of each frame can be acceptably reimaged at any given combination of object orientation angle and eye position. Such alteration of angular distribution due to reimaging is qualitatively suggested in
FIGS. 3-4
, which use a simple lens to represent the possibly reflective and/or complex reimaging optics.
With no lens in
FIG. 3
, an eye at normal viewing distance from the lenticular object could directly view the top, center, and bottom of the frame in the manner of FIG.
1
. (Without loss of generality, this eye location may conveniently be taken as that of the central lens in
FIG. 3.
) However, with the lens in place in
FIG. 3
, the eye must be located beyond the image (and also below the axis, as illustrated) in order to see the inverted end of the frame image. This is because reimaging by the lens causes the object beam, which is initially directed toward the optical axis, to be converted to the image beam, which is directed away from the axis. Note that the eye location shown is outside the viewing angle for rays from the opposite end of the frame, and that in fact, any eye location beyond the image necessarily precludes the observer from viewing the entire image simultaneously, because of similar viewing angle limitations. These are fundamental limitations on viewable frame size in directly viewed real images that can only be overcome when the lens is larger than the image, for example, as in FIG.
4
.
As illustrated in
FIG. 4
, the eye can view the entire image from any of the eye locations shown (and from anywhere between them), because al
Amster Rothstein & Ebenstein
Mack Ricky
Vizta 3D, Inc.
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