WO2001018589A1 - Systemes et procedes de vision tridimensionnelle - Google Patents

Systemes et procedes de vision tridimensionnelle Download PDF

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Publication number
WO2001018589A1
WO2001018589A1 PCT/IL2000/000534 IL0000534W WO0118589A1 WO 2001018589 A1 WO2001018589 A1 WO 2001018589A1 IL 0000534 W IL0000534 W IL 0000534W WO 0118589 A1 WO0118589 A1 WO 0118589A1
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WIPO (PCT)
Prior art keywords
viewer
display
light
image
picture elements
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PCT/IL2000/000534
Other languages
English (en)
Inventor
Paul Kleinberger
Ilan Kleinberger
Jack Y. Mantinband
Hillel Goldberg
Eli Kleinberger
Original Assignee
3Ality, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 3Ality, Inc. filed Critical 3Ality, Inc.
Priority to US10/070,355 priority Critical patent/US7190518B1/en
Priority to EP00956767A priority patent/EP1214620A1/fr
Priority to AU68628/00A priority patent/AU6862800A/en
Publication of WO2001018589A1 publication Critical patent/WO2001018589A1/fr

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    • H04N13/239—Image signal generators using stereoscopic image cameras using two 2D image sensors having a relative position equal to or related to the interocular distance
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/0093—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 with means for monitoring data relating to the user, e.g. head-tracking, eye-tracking
    • G—PHYSICS
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    • G02B30/22—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images by providing first and second parallax images to an observer's left and right eyes of the stereoscopic type
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Definitions

  • the present invention relates in general to systems for and methods of three-dimensional viewing, including three dimensional displays and projectors.
  • the present invention relates to three-dimensional displays and projectors which can be used by one or more viewers to obtain a perception of depth while viewing still or motion pictures.
  • the methods used involve a variety of schemes for transporting two different images to a viewer's left and right eyes.
  • the two different images are typically produced by two cameras placed side by side in a manner which in turn simulates the vision of two human eyes.
  • the mammalian vision system employs the differences between a given scene as perceived by the right eye and the same scene as perceived by the left eye, to extract information regarding the distance of objects within the scene relative to the viewer. Since objects close to the viewer appear displaced to the right in the view seen by the left eye, and the very same objects appear displaced to the left in the view seen by the right eye, while more distant objects show less such displacement and most distant objects show essentially no such displacement at all, it is possible to calculate the distance of objects within the scene as a function of the amount of lateral displacement observed, and this, apparently, is what the human visual system does in our normal binocular (i.e., three-dimensional) vision of the world.
  • the prior art of three-dimensional viewing may be broken into categories as follows.
  • the first category includes hand-held viewing apparatuses (known in the art as 'viewers') of various sorts, based on lenses, prisms, mirrors, or combinations thereof, which viewers are held close to the eyes and deliver an appropriate image to each of the eyes.
  • the second category includes methods aimed at viewing images without any optical apparatus held next to the eye (i.e., without eyeglasses and/or viewers), which methods are based on interposing a plurality of lenticular elements in the display.
  • the third category includes systems involving eyeglasses worn by the viewer, which eyeglasses filter light according to its polarization.
  • the fourth category includes systems involving eyeglasses worn by the viewer, which eyeglasses filter light according to wavelength (i.e., color).
  • the fifth category includes systems involving eyeglasses worn by the viewer and employing switching mechanisms capable of rapid on/off switching (i.e., shutter systems) of optical elements.
  • the sixth category includes side-by-side implementations such as random- dot stereograms.
  • the seventh category includes methods employing flat screens for viewing images without a need for optical apparatus to be held next to the eye (i.e., without eyeglasses and/or viewers) and not involving lenticular surfaces. These methods are based primarily on interposing physical impediments arranged in a flat screen placed between the viewer and the image to be viewed, which impediments hide part of an image from one eye while allowing it to be seen by the other eye.
  • Each of the above listed categories has its associated inherent disadvantages as follows.
  • viewing apparatuses of the kind which require lenses, prisms, or mirrors held in proximity with the viewer's eyes are generally less convenient than alternatives which do not require special eyeware and do not require the viewer using them to hold the apparatus or to approach his eyes to special eyepieces.
  • the invention here disclosed involves no necessary use of lenses, prisms, or mirrors, and does nor require the viewer to look through a viewing apparatus placed or held near the eyes, it is basically dissimilar and advantageous over apparatuses thus categorized.
  • lenticular systems will always present images having a lower resolution than the resolution of which the display device to which the lenticular array is attached to is inherently capable.
  • eyeglasses With respect to the third through fifth categories, they all require the use of eyeglasses or an equivalent by the viewer.
  • the term 'eyeglasses' is referred to herein in a general sense of an optical apparatus having left and right eyepieces held close to the eyes of the viewer in such a way that substantially all the light entering the left eye is subject to an influence imposed by the left eyepiece, and all the light entering the right eye is subject to an influence imposed by the right eyepiece.
  • three-dimensional systems thus categorized all require the use of eyeglasses, which select, whether by color (wavelength), timing (shutter), or polarization, the images reaching each of the eyes.
  • These categories include apparatuses having a form of conventional eyeglasses (e.g., ones used for reading), but also include devices such as, but not limited to, pilot helmets having head-up displays (HUD), virtual-reality headgears and similar designs.
  • HUD head-up displays
  • systems falling into these categories share a common disadvantage; they all require an inherent use of special eyeglasses or headgear.
  • the necessity for optical apparatus held near the eyes subtracts from the pleasure, comfort and naturalness of the experience of viewing the display, and may, depending on the system used, add significantly to the expense.
  • polarizing eyeglasses deal with arrangements in which a display system polarizes light derived from the left image in a given particular orientation and polarizes light derived from the right image in another particular orientation. Accordingly, the viewer wears a set of polarizing filters one for each eye. The filter of the left eye passes light polarized in the particular orientation in which the left image was polarized, whereas the filter of the right eye passes only light polarized in the particular other orientation in which the right image was polarized. Consequently each eye sees only the image appropriate to it and does not see the image which is inappropriate to it; thus a three-dimensional image is viewed by the viewer.
  • U.S. Pat. No. 4,719,507 to Bos discloses a system employing polarizing eyeglasses to distinguish between the left and right images, and also uses switchable rotating means to determine, in a temporal sequence, which image receives which polarization. These and similar systems have the disadvantage of requiring use of polarizing eyeglasses. Certain further disadvantages characterize systems which use polarizing glasses yet do not use switching means (c.f, fifth category).
  • U.S. Pat. No. 5,050,961 to Venolia provides an example, and is representative of various others.
  • the display area is divided into subregions with left image and right image segments.
  • small polarizing subunits process the light emanating from each subregion of the display, and the division of the image into left and right image areas coincides with the orientation of the polarizing means employed in a first layer, such that all the light emanating from the right image is polarized in a first orientation, while light emanating from the left image is polarized in a second orientation perpendicular to the first orientation.
  • the user wears polarizing eyeglasses, so that each eye sees the appropriate image segments and only those.
  • An inherent disadvantage associated with such schemes is that part of the display surface is blocked from the view of each eye.
  • 3D-movie the traditional three- dimensional movie
  • a projection system projects full images of the right and left images simultaneously onto a common display (typically a reflective movie screen).
  • a common display typically a reflective movie screen.
  • 3D-movies are presently displayed in for example Disneyland.
  • This projection system has the advantage that each eye sees a continuous and uninterrupted image.
  • this projection system has the disadvantages of (i) requiring the viewer to wear eyeglasses, and (ii) requiring special projection devices which involve two projectors (or a specially designed single projector having the effect of two projectors) simultaneously projecting related pairs of images onto the screen.
  • this method calls for special projection equipment and, since it requires two separate light sources, it is not adaptable to standard computer displays nor to television displays.
  • optical filters result in a right image made up of and substantially limited to particular wavelengths passed by a filter covering the right eye, and in a left image made up of and substantially limited to particular different wavelengths passed by the filter covering the left eye.
  • these systems prevent the use of natural color images.
  • shutter systems are mechanisms consisting of elements capable of either blocking light or passing light, or of elements capable of rotating the orientation of polarized light (collectively referred to herein as switchable means). In both cases the mechanisms are capable of being switched on/off rapidly.
  • the switching of the mechanisms is coordinated with changes in the images being displayed, usually in such manner that the left image is displayed when the left eye's vision of the screen is enabled and the right eye's vision is blocked, and at a later time the right image is displayed when the right eye's vision is enabled and the left eye is blocked, wherein switching is intentionally rapid enough so that the persistence of human vision leaves the viewer with an impression of a continuous image. It should be noted that if switching had been slower, an impression of flickering would have resulted.
  • U.S. Pat. Nos. 5,002,387 to Baljet; 5,083,851 to MacDonald; and 5,245,319 to Kilian provide examples of systems characterized by alternating eye 3D-glasses, alternating between left and right lens transmissiveness and synchronizing the left lens transmissiveness to left images and right lens transmissiveness to right images. Yet, these methods involve eyeglasses obligatorily worn by the viewer. This inherent obligation however is a primary disadvantage. Additional disadvantages of these systems include the complexity and thus expense of the shutter eyeglasses which must be connected to the display apparatus and simultaneously controlled, or alternatively (e.g. MacDonald) the increased complexity and expense of the display hardware itself. To avoid the use of complex eyeglasses U.S.
  • Pat. No. 4,719,507 to Bos discloses an arrangement which allows use of passive polarizing filters in the eyeglasses, putting the more complex and high-voltage apparatus into the display device.
  • U.S. Pat. No. 4,792,850 to Liptoh discloses a similar arrangement using circular light polarization. Nevertheless, these solutions have the disadvantage of making the entire screen appear and disappear to each eye during each cycle, which tends to increase the impression of flickering of the screen.
  • the principle disadvantage of the systems described by Bos and Liptoh is their dependence on eyeglasses worn by the viewer.
  • side-by-side implementations such as for example random dot stereograms are essentially methods for utilizing parallax information, are difficult to see for many viewers, convey only simplified images, and cannot convey color.
  • a simple colorless image is combined with a complex background pattern, the background pattern substantially repeating itself at an interval less than the interpupillary distance of human observers, and the pattern being modified by the simplified image in such a way that elements of the simple image intended to be seen as being closer to the viewer cause corresponding areas of the repeating pattern of the complex background to be displaced towards each other.
  • the background pattern would in large part repeat itself every inch, then an area representing a close object repeats itself at a distance of 19/20 inch, and an area intended to appear further away repeats itself at a distance of 21/20 inch.
  • the viewer often with some difficulty, views the stereogram by directing his right eye to some given area of the repeating pattern, and his left eye to an adjacent area of the repeating pattern, to the left of the point seen by the right eye. Since the patterns substantially repeat themselves, the viewer is (usually) able to coalesce the images.
  • the left eye is provided with a left image which is different (since it originates e.g. an inch away on the stereogram) from the right image.
  • the eyes then have the ability to extract the information based on the consistent differences between the two images, and understand it in terms of the simplified scene which is in fact included in the stereogram only as modifications in the position of elements of the background pattern.
  • Normal images have also been included in published stereograms, for example in the "Magic Eye” series of books published by Michael Joseph Ltd., London.
  • sets of normal full-color images with differing parallax information are included in the published image in such a way that they can be viewed by the viewer's directing his eyes in the same manner as he directs them for viewing a stereogram, namely by directing his right eye to a given image, and directing his left eye to a similar neighboring image which is physically next to the first, and differs from it in that it contains a different parallax view of the same scene.
  • 5,264,964 to Faris discloses a method for creating a parallax barrier by placing pairs of small polarizing regions one immediately above the other and of opposite polarization orientation, thus creating opaque regions, and also describes an embodiment in which simple opaque regions are used in place of the pairs of polarizing regions.
  • a barrier is created with transparent regions alternating with opaque regions, with size and spacing adjusted such that the left and right eyes looking through the transparent regions of the barrier each sees a different pixel on the display layer, thus creating the possibility for supplying each eye with elements of the left and right image which are appropriate to it.
  • Faris' invention is limited to a fixed position of the viewer with respect to the display during the whole time of viewing.
  • W097/26577 which are inco ⁇ orated herein by reference, teach a variety of systems and methods for three dimensional viewing, including displays and projectors. As is further explained hereinbelow, some of the systems and methods described in U.S. Pat. No. 5,822,117 and PCT Publication W097/26577 suffer one or more limitations. It is one object of the present invention to provide solutions to these limitations. It is, however, another object of the present invention to provide yet novel systems and method to three dimensional viewing.
  • frame refers to a display or projection or a part of a display or projection to be three-dimensionally viewed.
  • left image refers to the image to be seen by the left eye of the viewer. In embodiments of the present invention used for producing the illusion of depth, this would correspond to the image seen by the left eye, captured for example by a camera playing the role of the left eye and placed near (typically to the left of) a second camera playing the role of the right eye, or to an image created by drawing, computer graphics, or other non- photographic means, which image contains parallax information appropriate to the left-hand position of a pair of images which, when viewed together and combined by the human perceptual system into a single image, give the illusion of depth. Note that this description is given for clarity only, and is not intended to limit the scope of the invention to the display of left and right images of any particular origin.
  • the left image may be a still image, or one of a sequence of images displayed one after another to constitute a motion picture.
  • the phrase "right image” refers to the image intended to be seen by the right eye.
  • the right image may be a still image, or one of a sequence of images displayed one after another to constitute a motion picture.
  • a "left image” and a “right image” refer to the pair of images which together constitute a stereoscopic display pair, the former presenting a scene as it would appear to the left eye of an observer, the latter to the scene as it would appear to the right eye of an observer.
  • Stereoscopic and autostereoscopic display systems generally seek to present a left image to a viewer's left eye and a right image to a viewer's right eye, and to prevent light from the left image from reaching the right eye and light from the right image from reaching the left eye.
  • 3D-image refers to a three-dimensional image as viewed by a viewer according to any of the embodiments of the present invention.
  • the term "display” refers to a medium by which an image as defined hereinabove is initially presented. Suitable displays include but are not limited to display screens such as light reflecting means, a translucent screen, or light-emitting means, such as a CRT screen or an LCD screen.
  • display screens such as light reflecting means, a translucent screen, or light-emitting means, such as a CRT screen or an LCD screen.
  • the nature of the "display” as used herein is not limited to these examples, nor is the invention described herein limited to the use of any particular technology of display.
  • the meaning of "display” is not limited to means traditionally used for displaying three-dimensional images and motion pictures.
  • outdoor advertising displays and pictures such as those printed on cards or in books or magazines, are all additional examples of "display” relevant to certain embodiments of the invention described hereinbelow.
  • projection refers to an image as defined hereinabove that is initially projected so as to form a display.
  • polarizing means includes any linear polarizing means which block light whose angle of vibration is in one direction (i.e., orientation) while passing light whose angle of vibration is in another direction.
  • the term also includes means which convert linearly polarized light into circularly polarized light, means which convert circularly polarized light into linearly polarized light, and means which pass light which is circularly polarized in one sense but do not pass light which is circularly polarized in the other sense.
  • Light rotating means also known in the art as “light retarding means” and as “phase retarding means” refers, in particular, to means which change by some degrees, in most cases 90 degrees, the orientation of linearly polarized light, or which change the sense of circularly polarized light, converting right-handed polarized light into left-handed polarized light or left- handed polarized light into right-handed polarized light.
  • the concept 'active or inactive in light rotation' is used herein in this document and especially in the claims section below it also refers to a situation where in the inactive state the light is rotated m degrees and in the active state it is rotated m + 90 degrees.
  • switchable light rotating means refers to light rotating means whose light rotating effect can be turned on/off under electronic control, as under the Kerr effect.
  • light rotating means is defined 'on' when it rotates light and 'off when it does not rotate light.
  • 'on' and 'off as used herein refers to the presence or absence of the optical phenomenon of light rotating effect, not to the presence or absence of an electrical field which controls the effect.
  • the phrases 'active/inactive in light rotation' are used herein in this document and especially in the claims section below it also refers to a situation where in the inactive state the light is rotated m degrees and in the active state it is rotated m + 90 degrees.
  • the present invention is couched in terms of linear light polarization.
  • the layer may in fact include a linear polarizing layer coupled with a suitably aligned quarter-wave light retarding means, converting the linear polarized light into circular polarized light.
  • Reference to light linearly polarized in a particular orientation can then be taken to refer to light circularly polarized in a particular sense (i.e., left-handedness or right-handedness).
  • the filter may in fact further include a suitably aligned quarter-wave light retarding means which converts circularly polarized light into linearly polarized light.
  • the linear light polarizing filter might be replaced by circular polarizing means which pass light with circular polarization in one particular sense (i.e., left-handedness or right-handedness) while absorbing, diffusing or reflecting light circularly polarized in the other sense.
  • on/off switchable light rotating means are employed for rotating the orientation of linearly polarized light
  • reference to those means also refers to on/off switchable light rotating means for changing the sense of circularly polarized light.
  • on/off switchable light rotating means for changing the sense of circularly polarized light.
  • shutter means refers to any means by which particular portions of a screen or layer of material can be made to be substantially transparent, and at other times can be made to be substantially opaque, under the control of switchable means. This might, for example, be accomplished by a unit of switchable light rotating means (as defined above) sandwiched between two- layers of linear polarizing means, both layers oriented in a given same direction. Such an arrangement is opaque or transparent depending on whether the light rotating means is on or off. This example, however, is given for the sake of clarity, yet the nature of the "shutter means” as used herein is not limited to this example nor to any particular technology of shutter means. Thus a solid material having transparent holes which is translated relative to the image as defined hereinabove can also be used as suitable shutter means in some of the embodiments of the present invention.
  • eyeglasses refers to any arrangement which provides for optical means which are physically close to the viewer's eyes, and particularly those which are such that most or all of the light emanating or reflected from the display and directed towards the left eye, enters optical means located in front of the left eye, before reaching it, whereas most or all of the light emanating or reflected from the display and directed towards the right eye enters optical means located in front of the right eye before reaching it.
  • eyeglasses as used herein includes the polarizing glasses and color-filter glasses traditionally employed in the field of stereoscopy, yet the term also includes headsets, arrangements which place mirrors or lenses or prisms in close proximity with the eyes, and so forth.
  • the term “viewer” refers to an individual facing and viewing the display.
  • the phrase “appropriate image” refers to the following: for the viewer's left eye the “appropriate image” is the left image as defined above, whereas the “appropriate image” for the viewer's right eye is the right image as defined above.
  • “Inappropriate images” are the right image with respect to the left eye and the left image with respect to the right eye.
  • “Appropriate eye” and “inappropriate eye” are terms derived from the above definitions.
  • viewing stereoscopically means, in particular, the viewing of pairs of left and right images containing appropriate parallax information, such that when the viewer views the images simultaneously or nearly simultaneously, and in the process of his viewing coalesces the two images into a single image gestalt in the manner well known in the art of stereoscopy, the result is a single perceived image giving the illusion of depth, as defined hereinabove a 3D-image.
  • viewing stereoscopically as used herein is not limited to pairs of images containing such parallax information, it is intended to apply to any pair of images which can be so coalesced and give the viewer the impression of a single image containing information from two sources.
  • color filters refers to elements which are transparent to light within a certain range or ranges of wavelengths, but block light within other range(s) of wavelengths, whether by absorbing the light of the blocked range(s) of wavelengths, or by reflecting it, or in some other manner.
  • parallax-barrier generally refers to the well- known system for autostereoscopy by which an optical barrier including transparent and opaque vertical strips is interposed at a particular distance from a display, and the display presents side-by-side pixels from alternating sources, pixels from a left image alternating with pixels from a right image.
  • optical construction refers to an optical element which, is designed by itself and/or in combination of other optical elements to redirect some of the light of a display or filter/block some of the light of a display, so as to result in stereoscopic or autostereoscopic viewing. Examples include, but are not limited to, a composite color filter, a parallax barrier, a composite light retarding means or a lenticular array.
  • two polarizers based system or “two polarizers system” refers to systems similar to those described in Figures 6-12 of U.S. Patent No. 5,822,117
  • the phrase "movement-permissive system” refers to a system described in Figures 32-33 of both U.S. Patent No. 5,822,117 and PCT Publication W097/26577, and in figure 33a of PCT Publication W097/26577.
  • This system allows for a certain amount of movement of the viewer's head and eyes, without said movement causing degradation of the autostereoscopic effect nor of the quality of the display as it appears to the viewer.
  • the movement- permissive system can be used in the two polarizing layers based systems described in Figures 6-12 of U.S. Patent No. 5,822,117, in a classical parallax- barrier system as defined above, and in various other contexts.
  • movement-permissive system is that systems in which it is incorporated are relatively indifferent to minor variations in the exact placement of, and optical qualities of the edges of, the various optical elements of which the systems are composed.
  • a parallax-barrier system including the movement-permissive system would be somewhat insensitive to minor errors of placement of the lines of division between the transparent and the opaque segments of the parallax barrier.
  • birefringent layer with individually switchable elements refers to a layer with a plurality of individually controllable elements of "switchable light rotating means", (as that term is defined hereinabove). In other words, it refers to any arrangement, such as that described in Figure 19 of U.S. Patent No. 5,822,117, in which a device such as a liquid crystal with individually addressable areas is used in connection with a control system in such a way that at any given time, any particular configuration of all, some, or none of the individually switchable elements will turn the polarization orientation of light passing through them.
  • birefringent layer with individually switchable elements sandwiched between two flat polarizing layers constitutes a popular form of notebook computer screen.
  • the birefringent layers with individually switchable elements referred to in the following descriptions are drawn as if the individually addressable elements are parallel vertical strips, and this is indeed a convenient configuration for most of the embodiments described herein, but it should be understood that this definition, and the embodiments inco ⁇ orating birefringent layers with individually switchable elements as described in the following, are not limited to that particular configuration. Standard LCDs with two-dimensional arrays of addressable elements could be used, as well as other configurations.
  • a "head-tracking system” refers to systems which adapt an autostereoscopic display to the positions of eyes of a viewer, so as to enable the viewer to view a stereoscopic image. Such a system typically includes a head-tracking sensor as is defined below and a control element.
  • a “mechanical head-tracking system” refers to head-tracking systems which accomplish the adaptation to the positions of the eyes of the viewer by mechanically moving the apparatus, or parts thereof.
  • a “electronic head-tracking system” refers to head-tracking systems which accomplish the adaptation to the positions of the eyes of the viewer using without physically moving parts of the apparatus, and without moving the apparatus as a whole.
  • head-tracking sensor refers to a device capable of detecting and reporting information about the position of a viewer's eyes with respect to a display and an autostereoscopic apparatus.
  • a head-tracking sensor is preferably a detector of the position of the eyes of the viewer(s), but it may also be a detector of the position of the head of the viewer, or a detector of the position of an object worn on the head of the viewer, from which an estimate of the position of the eyes may be derived.
  • detectors are available from various commercial sources. It may also be any other device capable of supplying information relevant to the viewers' eye positions.
  • a device in the style of a television 'remote control' unit, through which a user might supply information about his head position by pressing buttons on a handheld control device, would be included in the definition of a head-tracking sensor as that term is used herein.
  • sweet spot refers to that position or positions from which a viewer can see the stereoscopic image displayed by an autostereoscopic display.
  • the sweet spot In a classical parallax-barrier system the sweet spot is intrinsically rather small. When that system is enhanced using a movement- permissive system, the sweet spot is enlarged.
  • display pixels refers to the physical pixel elements of display devices such as LCD display devices.
  • image picture elements refers to picture elements of the left and right images, each of which may be displayed by zero, one, or several display pixels on a display device, or by a part of a pixel (for example a single color sub-pixel which is one of the elements (such as red) from an RGB triplet), or may be displayed, or not displayed, in some area of a display device which is not itself intrinsically divided into physical pixels.
  • the present invention relates in general to systems for and methods of three-dimensional viewing of displays and projections of still or motion pictures.
  • Most of the embodiments here presented relate to autostereoscopic systems, in which a viewer sees a stereoscopic image without need of special eyeglasses or other headgear.
  • a classic "parallax barrier" is combined with time multiplexing of the barrier and with moving the barrier rapidly from one position to another in front of a display, the position of the images displayed on the display being altered in coordination with changes in the barrier.
  • the result of this combination is to allow for full-resolution displays, while using large barrier elements, providing lower requirements for precision in a head-tracking system, and greater ease of construction.
  • a modification in the use of parallax barrier and other "sweet spot" technologies is presented, in which adaptation of the display apparatus to the changing position of a viewer is accomplished not by modifying the position of a barrier layer, but by modifying the size and position of elements of a displayed image.
  • Modification of both the size and position of elements of a barrier layer and the size and position of elements of the displayed images is shown to allow a barrier system to adapt to changes in the distance of a viewer from an autostereoscopic display, as well as to changes in the viewer's lateral position with respect to the display.
  • PCT Publication W097/26577 also presents methods for producing "movement-permissiveness" in an autostereoscopic display, that is, for allowing viewers to move somewhat with respect to the display without degrading the display's autostereoscopic qualities.
  • methods are presented for enhancing the "movement-permissiveness" of autostereoscopic systems based on a pair of polarizing arrays such as those taught in PCT Publication W097/26577.
  • the enhancement allows for movement-permissiveness in systems used for distance head-tracking as well as lateral head-tracking. Improvements are presented in systems utilizing a pair of polarizing layers, so as to produce an autostereoscopic display without time multiplexing, and consequently without flickering. Examples are presented in which this is accomplished using two displays and a beam splitter such as a half-silvered mirror, and using a pair of projectors in a back projection system.
  • Improvements are presented in systems for discerning the position of the eyes of a viewer with respect to a display, and in systems for helping a viewer of an autostereoscopic display without head-tracking to place himself successfully in the appropriate position for viewing the display.
  • An additional method for producing a full-resolution autostereoscopic display is presented, which method avoids the disadvantages both of spatial multiplexing and of time multiplexing, and presents full resolution left and right images across the entire breadth of a display at all times, rather than in alternation, as in some other systems.
  • This system has the additional advantage that it can be produced both as a flat display and as a projection system, and can be easily adapted to autostereoscopic viewing by an individual, or for use with eyeglasses for viewing by multiple viewers.
  • Several approaches to constructing this apparatus are presented.
  • a method based on color filtration is presented, which method has the advantage of producing a highly movement-permissive display with little loss of light, when compared to a parallax barrier based system.
  • the color filtration method can be adapted to flat displays, CRT displays, and to both front and back projection systems, including a projection system in which an autostereoscopic display is projected using a single projector.
  • This system can also be adapted to printing on paper and similar materials, and to back-lit static display applications such as advertising signs and stereoscopic works of art.
  • the required modifications can be accomplished by modifying the position of elements of the images on a display (this method may be applied to a variety of systems, including barrier displays, the color filtration displays, and lenticular displays.) These modifications may also accomplished by changing a barrier or filter layer, either mechanically, by shifting a barrier physically between only two alternative positions, or electronically, by manipulating the polarization of the light from a display and utilizing barrier layers or filter layers which behave differently when exposed to light of different polarization orientations.
  • the methods of shifting a barrier physically between two alternative positions, and of manipulating the polarization of the light from a display and utilizing barrier layers or filter layers which behave differently when exposed to light of different polarization orientations are also used to produce full-resolution displays in a color filtration system.
  • Additional techniques are presented for adapting a display to the changing position of a viewer by moving an image with respect to a barrier or filter, this time by moving elements of the image on a sub-pixel basis.
  • One method uses four sub-pixels rather than the traditional three sub-pixels to present an image element from a left or right image.
  • Another method uses a CRT with continuous phosphor strips of a particular color, where those strips are arrayed horizontally rather than in the classical vertical orientation.
  • Another set of methods uses displays capable of presenting any color on any part of the display surface, yet causes them to separate the colors on the display surface, thus enabling the use of the color filtration system.
  • Combinations of the methods presented for making simplified head- tracking systems and of the methods presented for making full-resolution displays are shown to be capable of producing systems which present full-resolution autostereoscopic displays with simplified head-tracking capabilities.
  • a mechanical version of such a system is first presented, followed by a similar system with the added advantage of having no moving parts.
  • a system for generating, from standard input such as a pair of television signals, a display combining a left and a right input image into an image format appropriate for use with the color filtration system is presented.
  • FIGs. la-b are top views of a system for autostereoscopic viewing in accordance with one embodiment of the present invention which allows for greater head movement combined with higher resolution;
  • FIGs. 2a-b are top views of a system for autostereoscopic viewing in accordance with another embodiment of the present invention which allows for greater head movement and higher resolution;
  • FIG. 3 is a top view of one embodiment of the present invention of using a system for an autostereoscopic display adaptable to changing positions of a viewer, by adjusting the position of the image on the display, and inco ⁇ orating a feed-back device for monitoring positions of imagery data displayed on a display and feeding that information to a control element which controls the display and/or a parallax barrier;
  • FIGs. 4a-b and 5a-b are top views of two embodiments of the present invention providing for adaptation of the display to varying distances of the viewer;
  • FIG. 6 is a top view of one embodiment of the present invention for providing a dynamic movement-permissive system
  • FIG. 7 is a top view of one embodiment of the present invention for providing an autostereoscopic system which does not use time multiplexing, hence does not flicker, yet also presents both eye's images at full resolution;
  • FIG. 8 is a top view of an embodiment of the present invention employing a beam splitter and a pair of displays for generating a full-resolution, non- flickering, autostereoscopic display;
  • FIG. 9 is a top view of an autostereoscopic apparatus using one or two projectors in back projection generating a full-resolution, non-flickering autostereoscopic display
  • FIG. 10 is a top view of a system capable of finding the position of a viewer's eyes using light reflected from the eye surface or retina usable with any system for autostereoscopic viewing and other systems;
  • FIG. 1 1 is a top view showing several embodiments of a system according to the present invention which employs a dedicated color filter for effecting autostereoscopic viewing;
  • FIG. 12 is a top view of a system according to the present invention which helps viewers to find a "sweet spot" for autostereoscopic viewing;
  • FIG. 13 is a perspective view of a system according to the present invention for reducing flicker by combining stereo modulator systems with spatial multiplexing, using polarizing eyeglasses;
  • FIGs. 14 and 15 are perspective views of systems according to the present invention employing a liquid crystal array for full-resolution no-flicker stereoscopic viewing;
  • FIG. 16 is a top view of optional systems according to the present invention employing a liquid crystal array for stereoscopic viewing, autostereoscopic viewing and/or normal (non-stereoscopic) viewing;
  • FIG. 17 is a perspective view of optional systems according to the present invention employing a liquid crystal array and a lens element for stereoscopic viewing, autostereoscopic viewing and/or normal (non-stereoscopic) viewing
  • FIG. 18 is a perspective view of optional systems according to the present invention employing a liquid crystal array and a rear light source characterized by homogeneous rather than heterogeneous and diffuse light rays for stereoscopic viewing, autostereoscopic viewing and/or normal (non-stereoscopic) viewing;
  • FIG. 19 is a top view of a system according to the present invention employing a color filter and a single projector to project an autostereoscopic view according to the present invention
  • FIG. 20 is a top view of a system according to the present invention employing a single filter layer for showing an autostereoscopic view, utilizing lateral filter motion for head-tracking according to the present invention
  • FIG. 21 is a top view of a system according to the present invention employing a rear projection display and small active elements
  • FIG. 22 is a top view of a system for electronic switching of a color filter used in an autostereoscopic display system with head-tracking according to the present invention.
  • FIG. 23 is a top view of an autostereoscopic display system with head- tracking using RGB quadruplets according to the present invention.
  • FIG. 24 is a top view of an autostereoscopic display system with head- tracking using a barrier with elements whose position can be changed electronically according to the present invention.
  • the present invention is of systems and methods which can be used for three-dimensional viewing, including three dimensional displays and projectors.
  • the present invention provides improvements over prior art designs for three-dimensional viewing, such as the designs described in U.S. Pat. No. 5,822,117 to Kleinberger et al. and PCT Publication W097/26577, as well as other prior art designs, as is specifically indicated below.
  • a classical parallax barrier system might inco ⁇ orate the movement- permissive system described in U.S. Patent No. 5,822,117 and PCT Publication W097/26577 to allow some freedom of head movement and/or variability in inte ⁇ upillary distances among viewers, yet it might show each of the left and right images in as little as e.g., 30 % of the display space. This would result in a very rough and low-resolution picture.
  • the problem of the inherently low resolution of parallax barrier systems is partly solved by the system described in U.S. Patent No. 5,822,117 in the discussion of Figures 14, 14b and 15 therein, which system is designed for time- multiplexing image elements, while using a parallax barrier.
  • each part of the surface of the display can be used to show image picture elements of both the left image and of the right image, each at different times.
  • the impression is created that both left and right images are continuous across the display.
  • Such systems can be integrated with the movement-permissive system either by adding opaque areas to the barrier layer (as is described in PCT Publication W097/26577, Figure 33a therein), or by leaving certain areas of the display surface dark at all times (as is described in U.S. Patent No. 5,822,117 and PCT Publication W097/26577, Figures 32 therein).
  • This combination allows for some freedom of movement of the head of the viewer, and would give less of an impression of low resolution than would the classical parallax barrier system.
  • the combined systems would still have two distinct disadvantages.
  • Figure la shows an arrangement similar to that described in Figure 33a of PCT Publication W097/26577.
  • Layers 50 and 90 are uniform polarizing filters, and layer 60 is a birefringent layer with individually switchable elements.
  • Layers 50, 60, and 90 together constitute layer 40, which is a parallax barrier layer.
  • Layer 40 is located at a certain distance from display 10, in a manner well known in the art.
  • control element 80 controls display 10, in that it chooses whether a left image picture element or a right image picture element will be displayed at a given time in each particular area of display 10.
  • the birefringent effect of the individual elements of layer 60 are switched on and off selectively in order to line up the transparent portions with layer 40 with the position of the viewer's eyes, using information provided by sensor 85 which can be a head-tracking sensor, a source of information about the position of the viewer. If, for example, viewer's eye 30 was to move to the right (towards the bottom of the Figure), sensor 85 will provide this information to control element 80 which will cause area 604 to switch its birefringence, causing that portion of layer 40 to become transparent, and will cause area 601 to switch its birefringence causing its portion of layer 40 to become opaque.
  • sensor 85 can be a head-tracking sensor, a source of information about the position of the viewer. If, for example, viewer's eye 30 was to move to the right (towards the bottom of the Figure), sensor 85 will provide this information to control element 80 which will cause area 604 to switch its birefringence, causing that portion of layer 40 to become transparent, and will cause area 601 to switch
  • Lines 510, 512, 514, and 516 here recall the lines similarly numbered in Figure 32 of PCT Publication W097/26577; they delimit the area within which the viewer's eyes may move without causing the eyes to see less light from their appropriate images, nor any light from their inappropriate images.
  • FIG. la Comparison of Figure la to Figure lb reveals yet another advantage of this arrangement.
  • the viewer's eyes 20 and 30 have identical positions and distances with respect to the display.
  • control element 80 has used its capacities for switching the transparent areas of display 40 and its capacity for determining the position of the left and right image picture elements on display 10 in such a manner as to change the opaque areas of 40 and the display areas of 10 without requiring movement on the part of the viewer.
  • the areas of layer 40 which include 601, 602, 603, and 61 1, 612, and 613 are transparent, and a left image picture element is displayed on areas 101,102, and 103 of display 10 while a right image picture element is displayed in areas 104, 105, and 106 of display 10.
  • the areas of layer 40 which include 603, 604, 605 and 613, 614 and 615 are transparent, and a left image picture element is displayed on areas 102,103, and 104 of display 10 while a right image picture element is displayed in areas 105, 106, and 107.
  • Figures la and lb demonstrate that the arrangement depicted is capable of altering the presentation of the autostereoscopic image, at electronic speeds, in such a manner that all areas of display 10 can be used both for left image picture elements and for right image picture elements, at different times, and further that while the arrangement provides for large opaque areas of layer 40, as required by the movement-permissive system, those areas may be shifted around layer 40 rather than be permanently fixed in any particular position.
  • control element 80 has chosen to create on layer 40 opaque areas which are approximately equal in width to the transparent areas it creates on layer 40 (as indicated by the shading, the shaded areas being the opaque areas), but control element 80 has also chosen to display a left image picture element in area 102 of display 10, and a right image in area 105 in display 10, but to leave areas 101, 103, 104, 106, 107, etc. dark, that is, those areas display neither the left image picture elements nor right image picture elements.
  • Figure 2b depicts the same apparatus as is depicted by Figure 2a, but at a different time. Comparison of Figures 2a and 2b serves to show that for a given position of the apparatus and of the viewer there exists a plurality of different combinations of transparent and opaque elements on layer 60, and of areas of display 10 displaying left image picture elements, right image picture elements, or not displaying anything, such that the principle described in the preceding paragraph is nevertheless observed.
  • the apparatus under the control of control element 80, can switch rapidly among two or more such alternative arrangements.
  • Figure 3 presents another method by which the configuration of a parallax- barrier system may be modified so as to adapt itself to changes in the position of the viewer.
  • the effect is achieved by modifying not the parallax barrier, but the displayed image.
  • the viewer's left eye (330 or 430) and right eye (320 or 420) see light from the images displayed on display 10 after that light passes through parallax barrier layer 40.
  • the Figure represents the classical parallax barrier system, with fixed transparent segments alternating with fixed opaque segments, but it is clear that the system described in the following will apply also to various adaptations of the parallax barrier system, including those described in U.S. Patent No. 5,822,1 17 and PCT Publication W097/26577, those described in Figures la-b and 2a-b above, those described in Figure 11 below, and others.
  • Head- tracking sensor 85 supplies information to the system about the position from which the viewer (or viewers) is/are viewing the display.
  • Positions 330 and 320 represent one possible position of the viewer with respect to the display, with left eye at 330 and right eye 320.
  • Positions 430 and 420 represent a second possible position of viewer with respect to the display, with left eye at 430 and right eye at 420.
  • These two positions represent two arbitrary positions of the viewer, at approximately equal distances from display 10. Note that for the sake of clarity of Figure 3, the size of the individual subdivisions (which may be permanent or individually addressable elements) of layer 40 and of the marked areas of display 10 have been exaggerated. In the preferred embodiment these would be relatively much smaller than the scale on which they are drawn in the Figure, and hence would be capable of much finer adjustments of position than their scale in the Figure would otherwise imply.
  • areas 354-356 and 360-362 of display 10 will display left image picture elements and areas 351-353 and 357-359 of display 10 will display right image picture elements, according to the classical parallax- barrier method. This will allow the viewer, when in that position, to view the autostereoscopic image, with each eye seeing its appropriate image and not seeing any part of the inappropriate image.
  • head-tracking sensor 85 detects that the viewer's left eye has moved, say, from position 330 to position 430, and his right eye has moved from position 320 to position 420, that information is transmitted to control element 80, which causes display 10 to change the manner in which the left and right images are displayed.
  • control element 80 controls a mechanical motor- driven device which simply moves the display a specified amount, or which moves the display until a feed-back device 83 indicates that the display is in the desired position.
  • display 10 is a display with discrete addressable display pixel elements (such as a standard LCD display) under control of control element 80.
  • control element 80 using information provided by head- tracking sensor 85, calculates which images should be made visible in which physical positions, and simply directs left and right image picture elements to the appropriate physical display pixels of display 10.
  • display 10 is a display such as a laser light display, in which individual picture elements may be directed to any part of the display surface, and they are simply directed as determined by control element 80.
  • control element 80 exercises just such control, controlling the horizontal positioning of the image in such a manner that the image elements appear in the appropriate physical areas of the display, as shown in Figure 3.
  • CRT displays may be somewhat unstable in that the size and position of the display may vary with changes in line voltages, temperature of the apparatus, and so on. This is one of the reasons for which analog controls of image size and position are typically provided. Consequently this embodiment may also include a feed-back device 83 which detects the display's actual position on the display device and modifies the input parameters of the display device appropriately so that the displayed image will appear, and remain, in the position determined for it by control element 80. It is clear that the technique described above and in Figure 3 is compatible with the movement-permissive systems and the head-tracking systems as described in PCT Publication W097/26577 and U.S. Patent No. 5,822,1 17, as well as the various systems specifically described herein, and various other autostereoscopic techniques, and that it can be used in a manner independent of these other systems, or in conjunction with them.
  • Figure 4 describes a system for adapting autostereoscopic displays to movement of a viewer towards and away from the display.
  • layer 40 is a parallax barrier based on a birefringent layer with individually switchable elements, as was described above in the discussion of Figures la-b and elsewhere.
  • Element 10 is a display on which areas have been marked; the meaning of these areas is the same as that of the areas marked on display 10 in Figure 3.
  • Images may be moved left and right on the display surface, as was discussed above in connection with Figure 3. It is also clear that the same various methods that can be used to shift the images left and right can also be used to expand and contract both the image as a whole, and the image picture elements of which it is composed.
  • the image picture elements (610, 620) displayed by display 10 are capable of being so expanded and contracted.
  • layer 40 is capable of being subdivided into opaque and transparent sections of approximately the desired size, and the left and right image picture elements on display 10 can be placed appropriately, then it is possible for the display apparatus to adapt itself to the viewer's position with respect to the display, and to maintain that adaptation while varying the configuration of the apparatus while the viewer moves both left and right and towards and away from the display.
  • Figures 4a and 4b graphically demonstrates this phenomenon.
  • the distance between the eyes is the same, their sideways position with respect to display 10 is the same, and the distance 202 separating barrier layer 40 from display 10 is identical.
  • Figures 4a and 4b differ only in that the distance 230 of eyes 30 and 20 from barrier 40 in Figure 4a is considerably greater than is the distance 240 of eyes 30 and 20 from barrier 40 in Figure 4b.
  • Figures 4a and 4b can represent the same apparatus at different times, the viewer having viewed the display from distance 230 at a first time Tl, and then moved closer to the display to view it at distance 240 at a later time T2.
  • the changes in the configuration of the apparatus from Tl to T2 constitute the adaptation of the apparatus to changes in the distance of the viewer to the display.
  • the device can easily adapt to this change in the viewer's position by creating appropriate transparent areas on layer 40, e.g., at areas 510, appropriate opaque areas on layer 40, e.g., at areas 520, and causing display 10 to display left image picture elements at areas 610 and right image picture elements at areas 620.
  • the apparatus as described can also adapt itself to changes in the position of the viewer's eyes when the viewer tilts his head sideways.
  • the net effect of his doing so, so far as the autostereoscopic device is concerned, is to reduce the angular distance between the eyes.
  • the system as described is capable of adapting its geometry to this change in angular distance between the eyes, just as it is capable of adjusting to variations in inte ⁇ upillary distance between one viewer and another.
  • Figures 5a-b show a similar implementation of this embodiment of the present invention, this time based, not on a parallax barrier, but, on a two polarizing layers system as described in U.S. Patent No. 5,822,1 17 and in PCT Publication W097/26577 (see, Figures 6, 18 and 19 therein).
  • 50 is a polarizing layer
  • 55 is a birefringent layer with individually switchable elements
  • 65 is yet another birefringent layer with individually switchable elements
  • 90 is a polarizing layer
  • 10 is a display.
  • 80 controls both the switching of the switchable elements of birefringent layers 55 and 65, and also coordinates the appearance of the left image and the right image in the appropriate areas of display 10.
  • the apparatus can adapt to his changing position by altering the size of areas marked as 510, 520, 610, and 620 on the Figures. If the position of the layers remains constant and the viewer approaches more closely, the overall geometry of the apparatus can be maintained if the size of areas 510 and 520 of layer 40 (or layer 55) grow smaller in proportion to areas 610 and 620 of display 10 (or of layer 65), and conversely as the viewer moves further away, elements 510 and 520 must grow somewhat larger in proportion to the size of the elements 610 and 620.
  • a novel construction of a pair of liquid crystal arrays for autostereoscopic viewing PCT Publication W097/26577 teaches the use of a pair of polarizing arrays without an intervening shutter layer in an autostereoscopic display system capable of head-tracking (aiming the left and right images at the user's left and right eyes).
  • This embodiment of the present invention improves on that construction, with advantages of cost and simplicity.
  • One of the more expensive aspects of creating the system as is described in Figure 11 of PCT Publication W097/26577 is that it requires a shutter layer (e.g., layer 80 in Figure 11) that switches at fast enough speed to avoid the impression of flickering to the viewer. Speeds such as 120 Hz are typical in this use.
  • PCT Publication W097/26577 describes the use of that system in the displaying of either whole images (the left image followed by the right image followed by the left image in a time-sharing sequence), or else the displaying of parts of both images, followed by the other parts of both images.
  • the following relates to the former case, the displaying of whole images, but can clearly be extended to the other alternative.
  • the overall result is that the image has switched through two full cycles (left image, right image, left image, right image), and each of the liquid crystal arrays has gone through only once cycle (initial configuration, opposite configuration, initial configuration).
  • an appropriate control element is used to coordinate the switching of the liquid crystal arrays and the presentation of the appropriate image on the display, that a high speed switching of the image (e.g., 120 Hz) can be accomplished by the coordinated switching of two slower-speed liquid crystal arrays (e.g. two arrays operating at 60 Hz).
  • This arrangement has the advantage of lower cost as is compared to the use of a high-speed shutter, and is also more practical than switching a single liquid crystal array to accomplish the pu ⁇ ose, as liquid crystal arrays capable of switching at high speeds (e.g., 120 Hz) are not generally available at this time.
  • One method of introducing movement-permissiveness into such a system is to arrange (according to the principle shown by Figure 32 of PCT Publication W097/26577) for appropriate regions of the display to not emit any light from either image, and for the display to be controlled by the same control element which controls the variable elements of the polarizing layers. Yet in some applications (particularly applications where the autostereoscopic apparatus is not manufactured together with the display but is an "add-on") it is convenient for the system allowing for autostereoscopic viewing to be self-contained and to be installable without requiring exact registration with the display equipment. In that case, areas on layers 55 and 65 need to be opaque according to the principles of the movement-permissive system as shown in figure 33a of PCT Publication W097/26577.
  • Control element 80 can then cause opaque areas to appear and to move in conjunction and coordination with the switching of the individual elements of the birefringent layer controlling the polarization elements, in such a manner as to obtain and to maintain over time the effect described in PCT Publication W097/26577 fig 32-33a.
  • FIG. 10 is a display.
  • Optional layer 100 is a fixed uniform polarizing layer.
  • Layer 110 may be either a fixed polarizing layer such as is described in U.S. Patent No. 5,822,117 (layer 56 of Figure 6 therein), or else a birefringent layer with individually switchable elements.
  • layer 100 is unnecessary, since layer 1 10 polarizes light passing through it.
  • layer 100 is included; it polarizes light from display 10, some of which may or not be turned by the switchable birefringent areas of layer 110.
  • 10 is a display generating polarized light, such as for example an LCD display as is popular in notebook computers, then in this case also, layer 100 would be unnecessary as the light from display 10 would already be polarized.
  • 120 is an optional birefringent layer without individually switchable elements: this layer can be used but is unnecessary if 110 is a birefringent layer with individually switchable elements, since the effect of reversing the birefringent status of layer 120 would be similar or identical to the effect of reversing the birefringent status of each of the switchable elements of layer 110.
  • 130 is a birefringent layer with individually switchable elements, and 140 is a uniform polarizing layer.
  • layers 150 and 160 adds the movement-permissive system to the apparatus.
  • 150 is a birefringent layer with individually switchable elements.
  • 160 is a uniform polarizing layer.
  • the combination of the uniform polarizing layers 140 and 160 with birefringent layer with individually switchable elements 150 constitutes a system well known in the art, and used to e.g. create opaque areas in the displays of most notebook computers and digital watches.
  • layers 140, 150, and 160 taken together can produce opaque areas wherever is desired along the width of the apparatus.
  • Layers 150, 130, 120 (if used), and 110 can all be connected to a common control element 80 which controls the placement of image picture elements on display 10 and the switching of birefringent elements of layers 150, 130, and (optionally) 1 10, and which in turn may respond to information provided by a head-tracking sensor 85.
  • the addition of layers 150 and 160 to systems such as that described above in reference to Figure 5, allows for opaque elements (required by the movement-permissive system) to be placed electronically at the points where those blocking elements would be appropriate as described in PCT Publication W097/26577 ( Figures 32 and 33a therein), yet allows it to continuously conform to the variable geometry, potentially undergoing rapid switching under electronic control, of the birefringent layers with individually switchable elements inco ⁇ orated in the system.
  • the system has the benefits of electronic head- tracking and also movement-permissiveness, is capable of adapting both to sideways movement of the viewer and to forward and back movement of the viewer, and even to a large extent to tilting of the head of the viewer, all at electronic speeds and with no moving parts.
  • Display layer 500 is a display surface displaying left and right images as described by Rehorn in his description of his "image B", and in the preceding paragraph.
  • the shaded portions 510 of layer 500 represent areas of the first set, as defined above, and the unshaded portions 520 represent areas of the second set.
  • Layer 130 is a birefringent layer with individually switchable elements, and layer 140 is a uniform polarizing layer.
  • Layers 150 and 160 are optional; their definition and function is the same in this Figure 7 as is described for Figure 6.
  • the orientation of layer 140 is such that it is transparent to light of orientation B and opaque to light of orientation A.
  • the birefringent effect of layer 130 is inactive, while shaded areas 610 of layer 130 turn light by 90 degrees.
  • right eye 20 sees each shaded area 510 of layer 500 through a shaded area 610 of layer 130, and sees each unshaded area 520 of layer 500 through an unshaded area 620 of layer 130.
  • light from the right image arriving from areas 510 comes from the first set of areas, consequently is in orientation B.
  • shaded areas 620 of layer 130 it is turned 90 degrees into orientation A.
  • Layer 140 is by assumption transparent to light of orientation A, so in areas 510 the right image is visible to the right eye.
  • the right image displayed in areas 520 is in orientation A, and passes through unshaded portions 610 of layer 130, which are inactive in birefringence and do not affect the orientation of light passing through them. Consequently light from the right image from areas 520 also reaches layer 140 in orientation A and pass through to eye 20.
  • right eye 20 can see the right image on all areas of display 500.
  • light from the left image was oriented orthogonal to light from the right image in each of those areas. Consequently, such light, passing through the same areas of layer 130, will arrive at layer 140 with Orientation B, and be blocked.
  • the right eye sees the right image everywhere on display 500, and does not see any light from the left image.
  • Element 130 is a birefringent layer with individually switchable elements and elements 80 and 85 are the same as was defined in previous Figures, consequently the apparatus includes the head-tracking system.
  • Optional layers 150 and 160 provide for a movement-permissive system. If display 500 is capable of altering the placement and size of areas 510 and 520, then the apparatus can use the technology described above in the context of Figure 4, and the apparatus is consequently capable of adapting to viewers' movements as they move closer to and further from the display as well, and to adapt also to their movement when they tilt their heads.
  • display 500 is not capable of altering the placement and size of areas 510 and 520, and also a static polarizing strip layer is substituted for polarizer 140 and active element 130, then the apparatus would not be capable of head-tracking, yet it would still present the advantages of a full-resolution non-flickering autostereoscopic display.
  • 10 and 15 are display sources such as CRT displays.
  • 90 and 95 are uniform polarizing filters, orthogonal to each other. That is, if light originating from display 10 and passing through filter 90 is polarized in Orientation A, then light originating in display 15 and passing through filter 95 will be polarized in Orientation B, 90 degrees from A.
  • 1 15 is a beam splitter, such as a partially transparent and partially reflective surface, e.g., a partially silvered mirror. It allows some of the light (typically approximately half the light) from display 10 to pass through it to layer 190, and it reflects some of the light (typically approximately half the light) from display 15 onto layer 190.
  • a beam splitter such as a partially transparent and partially reflective surface, e.g., a partially silvered mirror. It allows some of the light (typically approximately half the light) from display 10 to pass through it to layer 190, and it reflects some of the light (typically approximately half the light) from display 15 onto layer 190.
  • Surface 115 either preserves the polarization orientation of light passing through it and reflected from it, or else transforms the orientations of reflected and of transmitted light by an equal degree, or else there is a predictable relationship between the degree to which it turns transmitted light and the degree to which it turns reflected light, in which case the orientations of filters 90 and 95 can be adjusted so that light from display 10, after passing through surface 115, is in an orientation orthogonal to that of light from display 15 after being reflected from surface 115.
  • One of the two displays 10 and 15 displays a left image, the other a right image.
  • the image on display 15 will need to be reversed left-to-right, since the viewer sees a "mirror image" of that image, with the areas originally on the left side of the screen as would normally be seen by the viewer transposed to the apparent right side of the screen by the reflective process. Transposing the reflected image at the display source allows it to correspond appropriately with the non-reflected image from display 10.
  • layer 190 is a fixed layer alternating active in light rotation with areas inactive in light rotation.
  • layer 190 is a birefringent layer with individually switchable elements, under control of control element 80 which receives information from head-tracking sensor 85.
  • control element 80 which receives information from head-tracking sensor 85.
  • the birefringence of areas of layer 190 is switched is the same manner, and with the same function, as that described in the context of layer 65 of Figure 5.
  • layer 190 presents areas active in light rotation, marked as shaded areas 192, and areas inactive in light rotation, marked as unshaded areas 194.
  • the right image arrives at layer 190 in orientation A, orthogonal to orientation B. Passing through the same shaded areas 192, the right image is turned to orientation B. Passing through unshaded areas 194, the right image is unchanged and remains in orientation A. Note that the invention is essentially unchanged if light passing through the unshaded areas is rotated by some amount m degrees, and light passing through the shaded areas is rotated by m + 90 degrees. The result of this arrangement is that the image passing through layer 190 presents the characteristics described for Rehorn's "image B", and described above in the context of Figure 7. Layers 130, and 140, and optional layers 150 and 160, and elements 80 and 85 refer to the same elements as were depicted in Figure 7 and provide the same functionality and advantages.
  • the apparatus as a whole provides the advantages of the electronic head-tracking and movement- permissive systems, provides full resolution for both images, does not flicker, and in the case of the embodiment where layer 190 is a birefringent layer with individually switchable elements, can adapt to changes in the viewer's distance from the apparatus as well.
  • layer 190 is a birefringent layer with individually switchable elements
  • the resulting system would not be capable of full distance head-tracking (and if layer 190 were not a birefringent layer with individually switchable elements it would not be capable of head-tracking at all), yet the system would still have the advantages of full resolution and non-flickering autostereoscopic display.
  • Layer 190 could be placed parallel to surface 1 15 and contiguous to it, and polarizers 90 and 95 could have identical orientations rather than orthogonal orientations. Then light moving from display 10 towards the viewer would pass once through layer 190, and light from display 95 would pass twice through layer 190 (once while moving towards surface 1 15, once, after reflection, while moving from surface 1 15 towards the viewer).
  • a layer constructed like layer 190 could be placed near polarizer 90 and a second similar layer placed near polarizer 95. The net effect of these alternative constructions would be the same as that described above: an "image B" would be produced.
  • Autostereoscopic apparatus using two projectors in back projection Figure 9 presents another method for achieving the required configuration for the display on layer 500 of Figure 7, an "image B".
  • 310 and 320 are projectors, one projecting a left image and the other a right image.
  • 330 and 340 are uniform polarizing filters, oriented 90 degrees from each other. If light from projectors 310 and 320 is already polarized, as would be the case if 310 and 320 were LCD projectors, then 330 might be a light-retarding layer rather than a polarizer, and 340 might be unnecessary. Alternatively, 330 and 340 might both be light-retarding layers.
  • the required effect is that light passing through 330 be polarized in some orientation A, and light passing through 340 be polarized in some orientation B orthogonal to A. Consequently, light from the left and from the right images arrives at layer 190 with polarization orientations orthogonal to each other.
  • Filters 330 and 340 are referred to in the claims below as parts of the projectors, resulting in light polarizing projectors.
  • Layer 195 is a translucent screen on which an image can be projected, and which is capable of transmitting light while preserving its polarization orientation, or which transmits light in a manner which modifies that orientation in a systematic way, such that the differences between the orientation of the first image and that of the second image is preserved.
  • Layer 190 is the same as the layer 190 described for Figure 8.
  • the effect of layer 190 on light reaching it from the displays is identical to that described in the context of Figure 8, and will not be repeated here.
  • the resultant configuration corresponds to that defined by Rehorn as "image B" and described above.
  • Layers 130, 140, 150 and 160 and elements 80 and 85 are as defined for Figure 8. Consequently this arrangement as well constitutes an autostereoscopic system with full resolution and no flickering.
  • Layer 190 may be moved closer to the projectors than to the viewers, with an additional lens arrangement used to refocus the image on layer 195; this would allow layer 195 to be smaller and less expensive.
  • layer 195 might be placed between layer 190 and the projectors, rather than between layer 190 and the viewer.
  • Figure 9 also presents yet another embodiment.
  • 320 is a projector
  • 340 is a uniform polarizing filter.
  • Layers 195, 190, 130, 140, 150, and 160 and elements 80 and 85 are as described with respect to Figure 8.
  • projector 310 and filter 330 are not used.
  • uniform switchable birefringent element 350 is used, and is controlled by control element 80.
  • the pu ⁇ ose of this embodiment is to produce most of the functionality of the previous embodiment, while reducing its cost by requiring only one projector rather than two.
  • element 350 is inactive in turning light, and one of either the left or the right image is projected from projector 320. Light from this image behaves just as was described in the previous embodiment.
  • element 350 is activated by control element 80 and timed to coincide with the projection of the other image (left, if right was previously projected, or right, if left was previously projected). Since element 350 turns the polarized light by 90 degrees, the net effect is that the light of the other image arrives at layer 190 polarized just as light from projector 310 was in Figure 8, and undergoes the same processes as were previously described for that light in the context of Figure 8.
  • time Tl a first image is presented, it is entirely visible to its appropriate eye and not visible to the inappropriate eye.
  • time T2 the other image is presented and it is also entirely visible to its appropriate eye and not visible to its inappropriate eye. While this arrangement does have the disadvantage that it is based on time-sharing of the apparatus and hence has some potential for flickering, it does have the advantage of full resolution for both images, and of lower cost since only a single projector is required.
  • the switching birefringent element 350 since it can be placed near the projector, can be quite small and consequently inexpensive.
  • 350 might itself be a birefringent layer with individually switchable elements, and be used in such a manner that some areas are initially projected in one orientation and other areas are initially projected in the other orientation, and then in a second phase those orientations are switched. This would have the advantage of making some areas of each image visible to each eye in each phase, and consequently reduce the impression of flickering.
  • Control element 80 controls various aspects of a display apparatus 81.
  • display apparatus 81 is here represented as one of the embodiments presented hereinabove, specifically the embodiment described by Figures la-b and 2a-b, but this is intended merely as an example; for present pu ⁇ oses, apparatus 81 may be any display apparatus, including projection, which uses information about the position of the viewers' eyes to control some aspect of the functionality of a display apparatus or other apparatus.
  • 88 is a light source. It is positioned somewhere in the area of the display, and shines light in the direction of the viewer or viewers. Light from source 88 is reflected from left eye 30 and right eye 20 of the viewer, and detector 85 captures the reflection. For simplicity of the drawing, 88 and 85 are displaced to the bottom of the drawing, i.e., to the right of the display. In practice it would probably be most convenient to place these objects in some central position, such as just above and near the center of the display.
  • Detector 85 is a light detector capable of recognizing light reflected from the viewer's eyes, and reporting the position, or the direction, of the origin of that reflection (i.e., the relative position of the eyes) to control element 80.
  • source 88 to provide light to be reflected from the eyes, and for detector 85 to be sensitive to that light.
  • light from light source 88 will be of an intensity and frequency which makes it either invisible to the viewer or unobtrusive to him, and it will also be characterized by some pattern or quality which makes it easy to recognize and easy to distinguish from all other light which may be captured by detector 85.
  • light from source 88 might be characterized by some particular frequency not likely to be found in the area of the viewer's eyes, or it might be characterized by a particular pattern of frequencies varying over time, or by a particular pattern of intensities varying over time, or by a particular form or shape of the light- emitting source 88 which would be recognizable in the source's reflected image, or by any combination of the above, or by any other means which will make the image of source 88 reflected from eyes 30 and 20 easily recognizable.
  • detector 85 could be, for example, a video camera connected to digitizing hardware and to computing means capable of scanning the digitized image presented by the camera and recognizing that particular part of the picture which represents light with the recognizable characteristics of light from source 88. More simply, 85 might be such a digitizing video camera, sensitive to a particularly light frequency, combined with a light filter which passes only light of approximately that frequency. This combination would make the process of scanning the image to recognize the reflected light relatively easy, since such light, and only such light, would reach the camera. An additional method would be to modify the intensity or frequency of the light from source 88 during a period when the light emanating from the display itself is not changing substantially, or is changing in some predictable way.
  • detector 85 compares the image seen by detector 85 before the change to the image seen by detector 85 after the change (e.g. subtraction of one image from the other) would yield an image in which the reflection from the eyes would be easily detectable.
  • the essential characteristic of detector 85 is that it can recognize the light from image of source 88 reflected from the eyes of the viewer, and report to control element 80 the angular direction or apparent position of each of the eyes of each of the viewers of the apparatus. To the extent that light reflected from the eye can be distinguished from other ambient light, the fact that light originates from source 85 is unimportant. Thus, an adequate implementation of this invention would be constituted by a detector 85 capable of recognizing light reflected from the viewer's eyes, which light originated from the display itself, rather than from source 88.
  • the reader can easily verify the principle upon which this embodiment is based, by looking into a mirror above which stands a naked light bulb.
  • the image of the bulb reflected from his eyes will be more intense than other light reflected from his face, will more clearly reflect any variations in color or intensity of the light source, and will in fact be seen to consist, on close inspection, of an actual image of the originating light bulb.
  • the problem of "finding the eyes" within the image received by detector 85 is rendered considerably simpler than would be the case by any other means of inte ⁇ retation of the image of the viewer's face, or by any method of approximating the position of the eyes by detecting or approximating the position of the head.
  • An additional advantage of this embodiment is that it provides accurate real-time information about the position of both eyes independently, as distinguished from devices which track the position of the head, or which track the position of some object attached to the head. Since the position of each eye is tracked independently, the device as a whole is immediately responsive to differences in inte ⁇ upillary distance from one viewer to another, and it is also capable of responding to tilting of the head (which causes a shortening of the horizontal component of the inte ⁇ upillary distance, which is the component relevant to most of the uses of head-tracking sensors mentioned herein, and in, for example, U.S. Patent No. 5,822,117 and PCT Publication W097/26577.
  • the apparatus can also provide accurate information about the vertical position of each eye as well, to any apparatus for which that information is of use.
  • a minor modification of the detection procedure may be called for when the viewer is wearing glasses.
  • the viewer's glasses may also reflect a strong and recognizable image of light source 88.
  • the computing means used to analyze the image collected by detector 85 and report the eyes relative positions will in some cases need to take into account the fact that there may be several reflected images of source 88, including one set from the eyes, one set potentially reflected from the front surface of the eyeglasses, and yet another reflected from the back surface of the eyeglasses.
  • Reflections of those sources from the glasses will typically be relatively far apart or (depending on the glasses' positions and the positions of the multiple sources 88) not appear simultaneously at all.
  • light source 88 is far to the side of the display rather than close to it, it will tend to reflect from the eyes, which are relatively curved, and not from the eyeglasses, which are typically relatively flat when compared to the surface of the eye.
  • Figure 10 can also be used to describe another embodiment of this aspect of the present invention.
  • the reflected light detected by detector 85 is light reflected from the retina of the viewer's eye, rather than that reflected from the surface of the eye.
  • detector 85 recognizes light according to the characteristics of light reflected from the retina, and provides that information to control element 80. Since the exact point of vision of the viewer is by this fully identified, there is no need to distinguish between reflected light which originated from source 88 and reflected light which originated from any other source, including that of the display itself. System which helps viewers find the "sweet spot"
  • An additional aspect of this invention is an improvement on a system first described by M. P. Rehorn in U.S. Patent No 2,820,395.
  • Rehorn's system addresses the difficulty experienced by viewers of autostereoscopic systems which require the viewer to view the systems from particular positions ("sweet spots"). In practice, viewers viewing such systems often find it difficult to know whether they are in fact in the correct position.
  • Rehorn describes a system which provides the viewer with independent feedback (that is, feedback not dependent on the success or failure of the autostereoscopic viewing itself) on the correctness of his position.
  • Rehorn's method has, however, a disadvantage. Feedback from Rehorn's system is provided by color.
  • a system may be made that allows the viewer to see an easily recognizable geometric shape (instead of a color blend) when the viewer is in the sweet spot, and which displays a geometric form which is clearly altered or recognizably distorted when the viewer is outside the sweet spot.
  • An example of such a system is now presented.
  • the position pairs 320 and 330 of Figure 12 are sweet spot positions of an autostereoscopic system, for the left and right eye respectively, as are 340 and 350.
  • the pair 330 and 340 is not a sweet spot: if the left eye is at 340 and the right eye at 330, the viewer will see reverse stereoscopy, that is, his left eye will see the right image and his right eye the left image. Aside from that particular spot, if the viewer's left eye is positioned e.g., somewhere between 330 and 350, and the viewer's right eye positioned somewhere between 320 and 340, then each eye will see some light from its appropriate image and some light from its inappropriate image.
  • Layer 11 in Figure 12 is a layer in a plane parallel to the plane of the display; in the preferred implementation, it would be in the plane of the display, perhaps surrounding the display surface.
  • layer 11 is divided into areas, each of which displays an image, e.g., a geometric form. There are two such forms, alternating along the width of layer 11. When two of these forms are seen together they combine visually to produce an easily recognizable composite form.
  • the composite form constitutes the shape of an "X" 106. If form 14 is seen to the left and form 13 is seen to the right, then the composite form is in the shape of a diamond 104.
  • Layer 40 is a layer placed between layer 11 and the viewer. It is opaque through most of its width, but provides a number of viewing apertures such as aperture 18, through which the viewer can see the forms presented by layer 11.
  • the width of aperture 18 is such that if the viewer is in the sweet spot, the viewer is able to see, through that aperture, a portion of layer 11 equal in width to that of two of the forms of layer 11, which is to say, the width of one composite form.
  • the composite form visible from the sweet spot is chosen to be so as to suggest that the position is appropriate.
  • the viewer viewing the forms on layer 11 through aperture 18 will see a series of diamond shapes. Circular or elliptical shapes might be provided instead, as might any other shape which is easy to see and, preferably, would suggest completion or appropriateness to a viewer.
  • the viewer viewing the forms on layer 11 from, say, positions 330 and 340, on the other hand, will see an "X" shape, easily distinguished from a diamond or circular shape. Similarly, from any intermediate position between the positions mentioned, the viewer would also see an "X" shape, and a lopsided one. Consequently using this system the viewer can see at a glance whether the viewer is in a "sweet spot", or is not.
  • layer 10 may be in the plane of e.g., the display, and layer 40 may be in the plane of e.g., a parallax barrier, this is not a requirement: any arrangement which provides a clearly recognizable form when the viewer's position is correct, and is clearly invisible or distorted when the viewer's position is not correct, would suffice as well.
  • size of e.g., aperture 18 and the size of the areas on e.g., a parallax barrier creating the autostereoscopic system, except insofar as is required to make the points at which the viewer sees forms indicating that the viewer is in a sweet spot do in fact correspond to the positions of the sweet spot of the autostereoscopic system.
  • Figure 13 presents an alternative approach for constructing an apparatus which is similar in form and identical in pu ⁇ ose to that of Figure 5 in PCT Publication W097/26577.
  • a first image (either left or right image) is presented in subregions 31 of display 1, and a second image (either right or left image, correspondingly) is presented by subregions 32 of display 1.
  • Polarizing filter 20 polarizes all light from display 1 uniformly.
  • 30 is a "switcher" layer of switchable light rotating means.
  • 39 is a layer including areas 41 active in light rotation, and areas 42 inactive in light rotation. Areas 41 of layer 39 are placed so as to be near to subregions 31 of display 1 and to correspond to them in size and position, and areas 42 of layer 39 are similarly sized and placed with respect to subregions 32 of display 1.
  • eyepiece 23 is a set of eyeglasses where one eyepiece 24 consists of a polarizing filter in some orientation, and eyepiece 25 consists of a polarizing orientation orthogonal to that of eyepiece 24.
  • the orientations of the eyepieces are chosen in such a way that when switcher layer 30 is inactive in light rotation, light from subregions 31 passing polarized by layer 20, unaffected by switcher layer 30 and turned by areas 41 of layer 39 is visible only to a first eye and blocked from the second eye, while light from subareas 32, polarized by layer 20, unaffected by switcher 30 and not turned by areas 42 is visible only to the second eye and is blocked from the first eye.
  • time Tl then, light from the first image will be visible only to a first eye, and light from the second image will be visible only to the second eye.
  • switcher layer 39 is activated in light rotation, and the second image is presented in subregions 31 and the first image is presented in subregions 32. Since the polarization of the images is reversed by switcher 30, the first eye now sees light from subregions 32 instead of that from subregions 31, and the second eye sees light from subregions 31 instead of that from subregions 32.
  • the first eye sees light only from the first image
  • the second eye sees light only from the second image.
  • the first image is presented in subregions 31 and at time T2 it is presented in subregions 32
  • the second image is presented in regions 32 and at time T2 it is presented in regions 31.
  • each eye sees only its intended image at all times, yet the amount of light reaching a particular eye at time Tl is substantially similar to the amount reaching it at time T2.
  • This result substantially reduces the impression of flickering, as contrasted to a system such as the "stereo modulator" systems in which at any given time one eye sees the entire screen and the other eye sees nothing.
  • this system has an advantage over systems such as the uPol system, in that whereas at any given moment each eye sees only half the display surface (as is the case with the uPol system), yet over time each eye sees its appropriate image over substantially all the surface of the screen, which fact (due to persistence of vision) creates an impression of a more high-resolution, continuous image.
  • layers 30 and 39 may be combined: if layer 39 is e.g., an LCD element which has individually addressable areas whose activity/inactivity in light rotation can be individually switched, then the function of layers 30 and 39 are combined in a single layer.
  • a switcher layer 49 may be used in the place of switcher layer 30, to similar effect.
  • pixels but by use of the word “pixels” no limitation is implied regarding the size or nature of the subregions.
  • a subregion of the display may be further subdivided into individual color elements (as is the case, for example, in an RGB display).
  • Individual color elements e.g., red
  • pixels are also included in the definition of "pixel” as used in the descriptions of this embodiment of the invention.
  • Element 100 in Figure 14 is a display source capable of producing an image.
  • a CRT picture tube, a liquid crystal display, or any other source may supply the image of element 100.
  • an LCD display for example, element 100 is physically divided into subregions 145 (sometimes referred to hereinafter as "cells", or “pixels").
  • subregions 145 sometimes referred to hereinafter as "cells", or "pixels"
  • division into pixels may be a matter of areas of control as exercised by computing and control means 150, rather than a physical division of the display hardware itself.
  • an analog device such as a standard broadcast television receiver for example
  • element 100 is a CRT or other display hardware not physically divided into subregions 145, there may be a need for a mechanism which ensures that each subarea is indeed of known dimensions and position, so as to enable coordinating operation between subregions of element 100 and subregions of element 200 described below.
  • this may be accomplished, for example, using an electronic feedback system such as was described above in the discussion of Figure 3, discussing a feed-back device 83 feeding information to a control element 80, used to control and stabilize the position and size of the display.
  • Another example of a method for accomplishing this would be to use available information about predictable systematic changes in the display (for example, systematic changes in the size of the displayed image on some CRT displays as a function of the amount of light displayed in the image) to compensate in advance for expected changes in the display.
  • information about changes in the size or placement of picture elements on the display can be used to control the functioning not of display 100, but rather that of other elements of the apparatus, in particular that of subregions of element 200, whose function is described below.
  • Element 200 is an optical-element capable of rotating light, such as a birefringent layer with individually switchable elements.
  • Each local area 240 of element 200 is capable of rotating light in varying degrees under electronic control, or of switching on and off their rotating effect under electronic control, or both. Local areas 240 are also sometimes called “cells" in the following.
  • the signals controlling cells 240 of element 200 are provided by control and computational means 250.
  • Figure 14 shows element 200 as being somewhat distanced from element 100, this is for clarity of the drawing only; in practice, element 200 will be close to, or contiguous to, element 100. Moreover each individual pixel 145 of element 100 is used in conjunction with a cell 240 of element 200; consequently they are to be of similar size and placement. In particular, the placement should be such that substantially most or all of the light emanating from a pixel 145 will pass through the corresponding cell 240 on its way towards the eyes of the viewer.
  • dimensions of the light emitting (or light transmitting) cells 145 may be made slightly smaller than the dimensions of the corresponding light-rotating cells 240, so as to ensure that substantially all the light from each cell 145 will enter the corresponding cells 240, even when the apparatus is viewed at an angle.
  • a left image and a right image are to be displayed by the apparatus, and it is assumed that the images can be expressed as an array of pixels whose dimensions correspond to the dimensions of the array of pixels 145 constituting element 100.
  • the pixels are being referred to here merely as a means of expressing the relationships of intensities of light from various sources in small local regions, and their disposition.
  • the intensity of light of the left image at (a,b) is referred to as L a ,b > and the intensity of light of the right image at that point as Ra,b-
  • the reader is reminded that the pixel 145 ,b y re f er to a single color element within an RGB triplet.
  • the left and right images are combined into what is referred to herein as a CI (Combined Intensities) image, and that image is displayed by element 100.
  • CI Combined Intensities
  • the CI image combines the intensities of the left image and of the right image. That is, the intensity of the light emanating from any particular pixel 145a,b is a function of the intensity La,b of the light from the corresponding pixel of the left image and the intensity Ra,b of the light from the corresponding pixel of the right image.
  • the mathematical function (“fl") that expresses the combined intensity may be the sum of the component intensities, the square root of the sum of the squares of the component intensities, or some other function.
  • an optional polarizing layer 190 is between element 100 and element 200.
  • layer 190 is unnecessary. If the light emanating from element 100 is not polarized (as would be the case for example if element 100 were a CRT display), then layer 190 polarizes that light uniformly. In either case the light that reaches element 200 is uniformly polarized. Layer 190, when required, is referred to in the claims as a part of the display itself.
  • Element 200 has the task of re-dividing the light from pixels 145 back into the original left and right images where the new left image is substantially similar to the original left image, and the new right image is substantially similar to the original right image.
  • Each cell of element 200 does this by partially rotating the light which passes through it, or by rotating the light during some portion of a time period T and not rotating the light during another portion of time period T (where time period T will typically be short enough to avoid producing an impression of flickering), or by rotating the light passing through some portion of the cell, or by a combination of these methods, or by some similar method.
  • Element 200 might, for example, be a standard LCD of the sort often used to produce notebook computer displays. Such an LCD is typically used in notebook computer displays together with a pair of polarizing filters, one before it and one after it, and the resulting configuration can display varying levels of light intensity (“grayscale”) by rotating light to a selected degree or for selected durations.
  • grayscale levels of light intensity
  • Element 200 in Figure 14 might be the same sort of LCD as is used in notebook computer displays and operate in similar manner with respect to its input signals, yet it is here used unaccompanied by the polarizing filters which usually accompany such an LCD in a notebook computer display. If, then, element 200 is provided with signals constituting an image, each cell 240 of element 200 can respond just as it does in the context of the notebook computer display responding to "grayscale" input, by rotating light to various degrees, between some minimum, and some maximum which is typically 90 degrees more than the minimum.
  • the amount of light rotated into a selected orientation, A can be proportional to La,b > and the amount of light unrotated, or rotated into a selected orientation, B, 90 degrees from A, can be proportional to Ra,b- Since what is herein described with respect to a particular pixel (a,b) can be true of all pixels, the overall effect is to construct a new left image in polarization orientation A, and a new right image in a polarization orientation B orthogonal to A.
  • each subregion 145 of element 100 displays a pixel whose intensity is a function (fi ) of the intensities of pixels in corresponding positions from the first image and from the second image.
  • Each cell 240a,b of element 200 receives a signal Ga,b which also depends on L ,b and Ra,b > and that signal determines the amount and the manner in which light is to be rotated by cell 240 a ,b-
  • element 200 under control of the DI image, separates the Combined Intentions image CI into reconstituted components which are similar to the original left image and original right image, where the new left image is emitted in a polarization orientation A and the new right image in a polarization orientation B, 90 degrees from A. If the viewer then wears polarizing eyeglasses 1000 which allow substantially only light of orientation A to reach his left eye and substantially only light of orientation B to reach his right eye, then each eye sees its appropriate image and stereoscopic viewing results.
  • the DI image can be modified so as to express the reconstituted image in the format of Rehorn's "image B", which can then be used to produce an autostereoscopic system, as is described below.
  • Figure 15 illustrates the methods of this embodiment in greater detail, by way of a specific example.
  • element 100 is exemplified as a liquid crystal computer display including of a light source 110, a uniform polarizing filter 120, a liquid crystal 130 which is a birefringent layer with individually switchable elements 145, and an additional uniform polarizing filter 170.
  • cells 240 of element 200 divide the light passing there through by the simple expedient of rotating that light 90 degrees during some portion of a time period T, and not rotating it during the remainder of the time period T. Note however that these assumptions are chosen for pu ⁇ oses of illustration only, and the scope of the invention should not be limited to these exemplary choices.
  • computing means 155 would calculate the CI image picture element as the sum (L a ,b + Ra,b) > that is, by adding the intensity of the corresponding left image picture element at point (a,b) of the image to the intensity of the right image picture element at point (a,b) of the image.
  • these values might be multiplied by some constant factor to avoid expressions of intensity greater than 100% of what the display hardware is equipped to display.
  • Computing means 250 which can also be the same physical computer as computing means 155, calculates the corresponding pixel of the DI image, which might be (L a ,b/Sa,b), that is the ratio of the intensity of the left image picture element at point (a,b) to intensity of the Combined Image picture element CI (a,b) at point (a,b), since under the assumptions the CI image picture element intensity is simply the sum of the left and right image picture elements' intensities at that point.
  • element 100 For each pixel 145, element 100 emits light corresponding in intensity to the CI image at that point. This light enters the corresponding cell 240 of element 200. Although for clarity of exposition Figure 15 has shown elements 100 and 200 as being somewhat separated, actual construction would place them contiguous or nearly contiguous to each other, so that substantially all of the light emanating from pixel 145 a ,b of element 100 would enter cell 240 a ,b of element 200.
  • the light from each cell 145 enters the corresponding cell 240 which, under control of computing and control element 250, rotates it during some portion of time period T, which portion depends on the relative intensities of the pixels from the left and right images at that point. For example if, say, 100% of the light of CI at position (a,b) comes from the left image, then cell 240 a ,b rotates the light 100% of period T, whereas if only 20% of the light of CI was due to the left image, then the cell 240 a ,b rotates light only 20% of time period T.
  • the directions could be reversed, so that a CI pixel 20% of whose intensity was due to the corresponding pixel from the left image might be rotated 80% of the time, and left unrotated 20% of the time.
  • each cell 240a,b is that an amount of light proportional to La,b, the pixel intensity of the left image, would be rotated into polarization orientation A, and an amount of light proportional to Ra,b, the pixel intensity of the right image, would be unrotated, and remain in polarization orientation B. Since for each pixel the intensity of the light which is divided is the sum of the intensities L a ,b and Ra,b > it is clear that the effect, over all the pixels of element 200, is that the left image now being created is substantially similar to the original left image, and is rotated into orientation A, and the right image now being created is substantially similar to the original right image, and is transmitted in orientation B.
  • the choice of which image is to be rotated is entirely arbitrary. If the rotated image is everywhere chosen to be the left image and the unrotated image is everywhere chosen to be a right image, and if a viewer uses polarizing eyeglasses 1000 with a filter 1020 in orientation A on his left eye and a filter 1010 in orientation B on his right eye, then stereoscopic vision of the images will result. Similarly, the right image might be rotated and the left image unrotated, and the eyeglass filters adjusted accordingly.
  • the intensity of the combined image picture element, Cla b would be the square root of ((L ,b) +(Ra,b) ) and the angle of rotation ⁇ for the pixel would be chosen with respect to the axes of orientation of the polarizers such that (CI a ,b(sin( ⁇ )) would equal L a ,b and (CIa,b( c °s(o:)) would equal Ra,b. (These formulae of course neglect incidental light losses, etc.
  • the essential feature is that the ratio (La,b/Ra,b) be equal to the ratio (sin( ⁇ )/cos ( ⁇ )).
  • the optimal means for sharing the light of a given pixel between two images might involve manipulating both the timing of the switching of the Kerr cell 240 ,b and also its voltage, and would further take into account such factors as the time delays involved in the switching operation itself, the behavior of the cell during the time of the switching, and so on.
  • the invention contemplates any method for dividing the light between the two images in such a manner that, when the transmitted light is viewed through polarizing filters such as 1010 and 1020, the pixel elements transmitted by the apparatus are similar to the pixel elements of the original left and right images and the new left and the new right images are displayed in differing polarization orientations.
  • computing means 155 and 250 referred to above need not be physically contiguous to the rest of the apparatus. It would be possible, for example, to have computing means 155 and 250 make the requisite calculations to transform a left and a right image into the CI and DI images at a remote site, and then broadcast or otherwise transmit the CI and DI images to an apparatus which would display them, an element 100 displaying the CI image as transmitted, and an element 200 'displaying' the DI image as transmitted, with effects as described above.
  • the arrangement described above can further be used to produce an autostereoscopic display. This can be done simply by modifying the choice of rotated and unrotated images across the face of element 200 in such a manner that Rehorn's "image B" results. As shown in Figure 15, one might, for example, alternate areas E and areas F across the face of element 200, where in areas E the left image is rotated and the right image unrotated, and in areas F the right image is rotated and the left image unrotated. Since the selection and placement of areas E and F is under electronic control of computing and control element 250, they may be placed on element 200, resized, and moved, in any manner convenient to the overall operation of the apparatus. In particular, their dimensions and positions can be modified in real time according to the distance and the position of the viewer or viewers, in order to conform to the requirements of the head-tracking systems described elsewhere in this document and in PCT Publication W097/26577.
  • the apparatus pictured in Figures 14 and 15 can be taken as a whole to be the display apparatus referred to as "display layer 500" in Figure 7 which is described hereinabove, where areas “E” and “F” of Figures 14 and 15 correspond to areas 510 and 520 of Figure 7 respectively.
  • An alternate arrangement for accomplishing stereoscopic display is to use the apparatus pictured in Figure 14 in the context of a projection system.
  • An arrangement such as that described in Figure 14 may be used in the place of the liquid crystal plus polarizers used in liquid crystal based projection systems.
  • the arrangement of Figure 14 could be used in the place of the liquid crystal "projection panels" sometimes used together with ordinary overhead projectors which normally project transparencies.
  • a combination of layers 100 and 200 as described in Figure 14 could be used in the place of the image-forming elements used in today's liquid-crystal-based projection systems. In both cases layers 100 and 200 are used as described above, layer 100 creating the CI image and layer 200 modifying it according to the DI image. The result would be projected, and the projected image would include the left and right images substantially recreated, and in different polarization orientations.
  • That projected image is projected onto a non-depolarizing projection screen, for example an aluminized screen, then a viewer using polarizing glasses can observe the projected stereoscopic image.
  • the projected image is divided as described above, with alternating areas E and F across the face of the image, and that image is projected onto the back face of a translucent material suitable for a back projection system, which material also has the ability to preserve the polarization orientation of the light projected on it, then the image visible on the front face of that material would constitute Rehorn's "image B".
  • Such a projected image would meet the definition of layer 500 of Figure 7.
  • the present embodiment when combined with the various methods described above and in PCT Publication W097/26577 for utilizing Rehorn's "image B" in autostereoscopic systems, will have all the advantages described above for the use of such systems (e.g., full resolution without flicker), plus the additional advantage that the apparatus itself will be relatively flat and relatively simple, and thus constitute an attractive and convenient autostereoscopic display system.
  • a single system can be able to present both the stereoscopic and the autostereoscopic displays in alternative use.
  • the same apparatus can be used to provide autostereoscopic display to a single user (or to several users, utilizing techniques described in PCT Publication W097/26577), yet when it was desired for multiple users to observe the display, the glasses- based stereoscopic mode might be used to advantage.
  • Two ways in which this can be accomplished are shown in Figure 16, which includes elements 80, 85, 130, 140, and optional 150 and 160 from Figure 7, and elements 100, optional 190, and 200 from Figure 14 which serve to fill the role of display 500 of Figure 7. That is, the arrangement described in context of Figure 14 and 15 produces an image with the characteristics described by Rehorn as "image B", and the discussion of Figure 7 explains how that image can then be viewed in autostereoscopic viewing, with the various advantages of the various systems described above.
  • Figure 16 shows alternative configurations which allow the system to be used for stereoscopic viewing with eyeglasses, for autostereoscopic viewing without glasses, or both.
  • the distribution of images on layer 200 is effected such that viewers with glasses 1000 can see the new (redivided) left image with the left eye and the new (redivided) right image with the right eye.
  • Layers 140 and optional 160 are polarizing layers, and would interfere with the process of viewing with glasses 1000. Consequently a system designed exclusively for viewing with glasses would use layers 100, possibly 190, use 200, use glasses 1000, and not require layers 130, 140, 150, nor 160. If it is desired to make a system which can function in both modes, one possible arrangement is to construct the apparatus in such a way that layer 140, and optional layers 150 and 160 if present, are removable.
  • layer 140 which is a unified polarizer with no electronic connections to the system, consequently an arrangement which contemplates frequently installing it and removing it is not impractical.
  • Layer 130 which is not required for glasses viewing, will nevertheless not hinder glasses viewing if it is inactivated in light rotation. In other words, while layer 140 must be removed, the light turning activity of layer 130 can simply be turned off. Nevertheless, it can be further advantageous to have a system which requires no gross physical change, such as physically removing layers, when converting from glasses viewing to autostereoscopic viewing.
  • layer 165 which is an additional liquid crystal layer, a birefringent layer with individually switchable elements, similar to layer 200.
  • layers 200, 130, and 150 are either inactive in light rotation, or activated in such a way as to transmit the CI image through to layer 165 substantially unchanged, or changed in a uniform manner which does not destroy the CI image.
  • Layer 165 is then used as described in the discussion of layer 200 above (that is, layer 165 is used as if it were layer 200), and the viewer can use glasses 1000 to view the stereoscopic image.
  • an apparatus which provides a glasses-based stereoscopic display with the advantages of full resolution, no flicker, and not requiring particularly fast switching liquid crystals, and which also provides an autostereoscopic display with the advantages of full resolution, no flickering, head-tracking both sideways and with respect to depth and which can compensate for some degree of head tilting and which can be constructed as a flat screen, and which further provides the advantage of converting between glasses-based viewing and autostereoscopic viewing by electronic switching and without moving parts, and which has the further advantage of being able to display normal non-stereoscopic images.
  • Another embodiment of this system is now described, having substantially the same functionality as that of the versions described above, but having the advantage of being in some respects easier to manufacture.
  • the system requires an array 200 of liquid crystal cells 240, each individually controllable, and each cell physically very close to, and exactly registered with, a physical pixel or with a picture element 145 from display 100.
  • Cells 240 must be close to pixels 145 because substantially most or all of the light from each pixel 145a,b must enter a cell 240 a ,b- If cells 145 and 240 are contiguous this is easily accomplished.
  • array 200 is contiguous to display 100
  • tooling up for such a manufacturing process might be expensive.
  • the requirement that the arrays be contiguous or immediately close to each other makes it difficult or impossible to manufacture the system using currently available off-the-shelf components.
  • Figure 17 describes such an implementation.
  • This embodiment essentially preserves the relationships described above between pixels 145a,b and cells 240a,b > but rather than requiring that display 100 and layer 200 be contiguous, it solves the problem by inte ⁇ osing an optical element such as a lens or a plurality of lenses between display 100 and layer 200 in such manner that the CI image created by display 100 is focused on the plane of layer 200 and a substantial proportion of the light generated by each pixel of display 100 reaches an appropriate cell 240 of layer 200.
  • an optical element such as a lens or a plurality of lenses
  • Figure 17 shows a single lens 800 (or its equivalent in the form of a compound lens, or of a Fresnel lens, or other equivalent optical element) inte ⁇ osed between display 100 and layer 200. If the focal length of lens 800 is appropriately chosen and display 100 and layer 200 are appropriately placed, the CI image created by display 100 will be focused on layer 200. The image will of course be inversed, but a one-to-one relationship is preserved between pixels 145 and cells 240. If arrays 100 and 200 were n cells wide and m cells high, then pixel 145 a ,b would be projected onto cell 240 (n-a),(m-b)- Other than that, however, the general operation of the system would be as described above in the context of Figures 14, 15, and 16.
  • a polarization-preserving dispersion layer may be placed near layer 200, so as to widen the angle from which the apparatus may be viewed.
  • FIG. 17 The configuration shown in Figure 17 and described above might be particularly useful in the context of a liquid-crystal-based projection system, where a light source sends light through a polarizer, a liquid crystal array and a second polarizer (the combination constituting a display 100), the resultant image being focused by a lens 800 onto a second liquid crystal array 'displaying' the DI image, and the resultant image then being refocused by another lens or set of lenses onto a polarization-preserving reflective screen such as an aluminized screen, where it could be viewed using polarizing glasses, or onto a polarization- preserving back-projection screen, where it could be viewed using either polarizing glasses or using the autostereoscopic methods discussed above.
  • a polarization-preserving reflective screen such as an aluminized screen
  • a modification of the idea shown in Figure 17 is to use techniques similar to those used in the manufacture of lenticular stereoscopic displays to provide a lens for each pixel 145a,b of display 100, which lens would focus the light from that pixel onto the appropriate cell 240 a ,b of layer 200.
  • elements 100 and 200 would no longer be required to be contiguous, most of the light from each pixel 145 would reach the appropriate cell 240 of layer 200, and the apparatus (in the various versions described above) would function as previously described.
  • a similar technique to accomplish the same pu ⁇ ose is to use an array of micro-lenses to concentrate the light from a back-lighting source through the central areas of each cell of a liquid crystal array.
  • This technique has been used in other contexts (e.g., to widen the angle from which an LCD can be viewed and increase the light efficiency). Concentrating the light in this manner would cause substantially most of the light passing through pixels of a first liquid crystal array to reach the corresponding pixels of a second array. Placing the micro-lenses before the first array rather than between the arrays might simplify construction, while accomplishing the same pu ⁇ ose.
  • the idea here is to provide a light source 110 such that the direction of the light rays emanating from it is homogeneous and organized rather than heterogeneous and diffuse, and to use this fact to cause the image (i.e., the shadow) of elements 145a,b to fall on the appropriate cells 240 a ,b, for the reasons and with the effects described above.
  • light source 110 is a relatively small and intense source of light approximating a point source.
  • the source might either emanate from a very small area approximating a point source, or else be focused in such a manner as to pass through a small area approximating a point source.
  • Light from source 110 is projected through polarizer 120, liquid crystal array 130, and polarizer 170, and reaches layer 200 in such manner that the light controlled by each pixel 145a,b of layer 130 arrives at the appropriate cell 240 a ,b of layer 200.
  • the array of cells of layer 200 must be somewhat higher and wider than the array of layer 130, as shown in the Figure.
  • Optional layers 175 and 205 are light defusing layers, one or another of which might be used (depending on the application) to break up the directionality of the light rays from source 110 and make the image visible from a variety of angles. If used, these layers must be selected so as to preserve the polarization orientation of the light while diffusing it. Thus, a material must be used which is similar to that required by the back-projection systems described above.
  • the second layer can also have an RGB color mask. Since it would be filtering the same colored light twice, the loss of correct light (e.g., red light from the first layer passing through the appropriate red-filtered cell of the second layer) would be minimal.
  • the advantage is that light from adjoining cells will (typically in the horizontal direction) be of a different color (the sub-pixel cell next to a red sub-pixel cell will typically be green on one side and blue on the other). So, the use of a color filter on the second layer as well as on the first layer will prevent leakage of light from adjoining cells, at least in one (typically the horizontal) direction.
  • Another method to avoid leakage is to polarize the light emanating from the first (display) layer in stripes (if used together with a color filter as above) or in a checkerboard pattern (if color filtering not used), and to filter the light in a similar pattern as it passes into the second layer. In this manner, light passing from a display cell to the appropriate cell of the second layer will have the same orientation, and will pass, whereas light from cells adjoining the appropriate source cell will have opposite orientations, and will not pass.
  • each cell 240 of layer 200 would need to be adjusted so that it will output light of the correct orientation (as described above) despite this possible modification of the orientation of the cell's input light.
  • Color barrier system for autostereoscopic viewing PCT Publication W097/26577 described (in Figures 40 and 41 and with respect to various other Figures) the use of a color filtration barrier in an autostereoscopic system.
  • a system similar to that described therein, but with certain additional advantages, is described in the following sections.
  • color filtration systems is used below as a general term to refer to the system described in PCT Publication W097/26577 with respect to Figures 40 and 41 therein, and to the systems described herein which use an optical construction which includes a composite color filter to create autostereoscopic systems, as described in particular with reference to Figure 11, and to similar systems.
  • composite color filter is also used to refer to such systems.
  • Figure 40 of PCT Publication W097/26577 shows a situation in which a plurality of RGB triplets (1020) display at least a part of a left image, and these alternate a plurality of RGB triplets (1030) displaying at least a part of a right image.
  • This arrangement is convenient to many types of displays, which display colors by showing combinations of primary colors combined in selected intensities.
  • many types of displays inco ⁇ orate display pixels which actually consist of several distinct primary-color components, such as RGB triplets.
  • Figure 11 provides an arrangement which avoids this disadvantage, and which is consequently superior for many applications. It is characterized by the fact that light from the two images is distributed over the display in such a way that small areas of the display surface present light from the left image in some color ranges, and also presenting light from the right image in some other color ranges. In this manner, light from both images is spread across the display in a more evenly distributed manner, thereby minimizing the size of, or eliminating entirely, the areas of the display which do not present some light from any given image.
  • the system described may be contrasted to the classical parallax barrier system in which transparent segments alternate with opaque blocking segments to form a barrier layer, and the blocking elements of the barrier layer line up in relation to the pixel elements of the display in such a way that the right eye sees pixels from the right image and the left eye sees pixels from the left image, in a manner well known in the art.
  • the arrangement described by Figure 11 uses a barrier technique in a novel way.
  • the barrier does not include transparent areas alternating with opaque areas, but rather a layer 40 which combines two or more color barriers, each of which has areas blocking light of a particular spectral range alternating with areas transparent to that spectral range.
  • the result is that the visibility, to each of the eyes, of light from each color range, is controlled by a parallax barrier arrangement, yet light from the appropriate image from at least some part of the color spectrum is visible to each eye throughout the entire surface of the display.
  • Figure 11 can be used to illustrate a number of embodiments of this idea.
  • the embodiments are described in terms of the example of three-color displays, such as RGB displays, yet it should be understood that the specific example is for illustrative pu ⁇ oses only and that the invention is not limited to those particular colors, nor indeed to systems of three colors in particular. Equivalent implementations might be made with two, four, five, or more color ranges.
  • elements which filter colors are discussed as if they were physically fixed.
  • Elements of variable optical characteristics with respect to color filtration could be used as well, on condition that at any given time their behavior approximates that described in the following with respect to fixed color filtration systems. For example, elements which block the passage of light of certain color ranges when the light is polarized and in a particular polarization orientation, yet pass light of that color range when the light is of a different polarization orientation, could be used.
  • the reader shall consider a case where display 10 is capable of displaying all colors from either image at all points. If then display 10 were to display light of a first color range (e.g., red) from part of a right image in areas 102-104 and 108-110, and light of that color range from part of a left image in areas 105-107 and 111-113, and if areas of 42- 44, 48-50, and 54-56 of layer 40 are transparent to light of that first color range, while areas 45-47 and 51-53 of layer 40 block light of that color from traversing them, then insofar as light of that first color range is concerned the arrangement constitutes the classic parallax barrier system for autostereoscopy.
  • a first color range e.g., red
  • red light from display 10 might be blocked by certain areas of layer 40
  • green light from display 10 might be blocked by certain areas of layer 40
  • the positions of the red-blocking areas and of the green- blocking areas would be different, in at least some areas of layer 40.
  • areas of the display which display red light from, say, the left image, and do not display, say, green light from that image, though they may display green light from the right image.
  • the arrangement would inco ⁇ orate the greatest possible differences in the placement of the various color ranges on display 10.
  • a three-color display if light from the first color range is displayed as stated above, then light from a second color range (e.g., green) from the right image might be displayed in areas 104-106 and 110-112 and light from that color range from the left image might be displayed in areas 101- 103, 107-109 and 113-115, while light from a third color range (e.g., blue) from the right image would be displayed in 106-108 and 112-114 and light of that color range from the left image would be displayed in 103-105 and 109-111.
  • a second color range e.g., green
  • a third color range e.g., blue
  • barrier layer 40 for each of the color ranges, areas which are transparent to that color range alternate with areas which block that color range, the pattern being repeated along the width of layer 40.
  • the placement of the specific areas with respect to each particular color range is such as to constitute the classical parallax barrier system with respect to that particular color range, as was illustrated above for the first color range.
  • areas 44-46, 50- 52 and 56-58 would be transparent to light of the second color range and areas 41-43, 47-49, and 53-55 would be opaque to that color range, and areas 46-48 and 52-54 would be transparent to light of the third color range, and areas 43-45, 49-51, and 55-57 would be opaque to that range.
  • filter arrangement A The placement of blocking areas on layer 40 specified in this and in the preceding paragraph will be referred to in the following as "filter arrangement A".
  • layer 40 presents a parallax barrier, yet the barrier elements of the various color ranges are placed differently on layer 40. Consequently, while each eye sees all the light from the image appropriate to it and does not see any light from the image inappropriate to it, yet there are no "holes" in the picture, no area of the display which fails to display at least some light from both left and right images. Such a display will be called a "dense" display in the following.
  • Figure 11 also illustrates this implementation.
  • the right image light of the first color range is displayed only in areas 103 and 109 (rather than in areas 102-104 and 108-110), while light of that color range from the left image is displayed only in areas 106 and 112 (rather than in areas 105-107 and 111-114).
  • right image light of the second color range is displayed at 105 and 111
  • left image light of the second color range is displayed at 102, 108, and 114
  • light of the third color range of the right image is displayed at 107 and 113 and that of the left image and the third color range is displayed at 104 and 110.
  • This arrangement of display colors is called "display arrangement B" in the following.
  • the color filter elements of layer 40 are as stated above with respect to the first embodiment, that is, layer 40 is constituted as described in "filter arrangement A.”
  • Figure 11 describes an autostereoscopic system which inherently results in a form of a movement-permissive system in which the display presents no large gaps (none as large, for example, as an entire RGB triplet) in the displaying of the right and left images.
  • the specific configuration presented above is merely an example of the way in which a color display and color filter system can provide an autostereoscopic view without large gaps in the display of light from both images, while allowing for some freedom of motion on the part of the viewer.
  • the arrangement might relate to two or four or five or more color ranges rather than three, and the display area displaying light from each color range might be either wider or narrower than that specified in the example.
  • the embodiment can be implemented by providing a layer 40 at appropriate distance with appropriately placed and sized blocking areas, and by displaying display pixels which mix the light from different color ranges from the left and right image picture elements in an appropriate manner.
  • the display might present (in order) red from the left image, green from the right image, blue from the left image, red from the right image, green from the left image, blue from the right image, then again red from the left image, and so on, the pattern repeating itself across the width of the display.
  • RGB triplets a first triplet would combine red from the left, green from the right, and blue from the left image, and the following triplet would combine red from the right, green from the left, and blue from the right image. Similar combinations could of course be made for systems based on two colors, four colors, or more. In contrast to some displays (RGB displays, for example) which always present particular colors in a set of particular positions, some other types of displays using other technologies are not limited to presenting particular colors in particular positions. Such a display is called a "full color display" in the following.
  • the embodiments described above can also be applied to a full-color display, however generated, if that display is first filtered to provide for regions of particular color ranges, as described in Figure 41 of PCT Publication W097/26577.
  • the techniques described above can be used in the context of any technique used to create an impression of continuous color ranges by combining elements of particular color in controlled amounts.
  • Many printing processes, for example, are of this nature. That is, the system is also applicable to contexts in which pigments are used to absorb color ranges from ambient light, and reflect back particular ranges of color.
  • the arrangement described above can be applied to contexts such as the printing of books and magazines, billboard- type advertising displays, and so on.
  • Printed pictures, having absorbed certain color ranges from the ambient light and reflected the unabsorbed color ranges, are seen by observers as having color in much the same manner as are displays which generate light, on condition of being well illuminated.
  • a printed image may display much the same color characteristics as a light-generating display source, and the method described above will work on it as well.
  • a light source which is both diffuse and sufficiently powerful will be required, but if such a light source is available the arrangement described will provide an autostereoscopic image as well.
  • a printed autostereoscopic image may be achieved by printing an image in two-layers, with a first layer corresponding to display 10 in Figure 11, with colors from the left and right images distributed across the printed page as described with respect to display 10, then a transparent overlay of appropriate thickness (corresponding to the appropriate distance of layer 40 to display 10, which depends in turn on the width of the areas into which display 10 is divided, as described in Figure 24 of U.S. Patent No. 5,822,117) placed on the image (display), and on that transparent layer, filter elements blocking particular colors, (described above as layer 40) are printed with transparent inks, or provided through any other printing or photographic or similar process.
  • the first layer might be produced as a transparency. Then both the image and the filter are tinted and transparent. The two-layers, positioned appropriately one with respect to the other, can then be backlit, creating a striking autostereoscopic printed display. In either case, front illumination as well as back illumination can be employed to autostereoscopically view the printed (displayed) image. In another embodiment, these principles can be applied also to the case of a stereoscopic projection system.
  • Figure 38 of PCT Publication W097/26577 demonstrates that it is possible to project a pair of full-color images through a color filter subdivided into areas filtering particular colors, and view an autostereoscopic image as a result, on condition that the projectors and the viewers are positioned appropriately.
  • the geometry of these arrangements creates "sweet spots", and projectors of left and right images may be placed at any left and right eye positions.
  • the light allowed to pass through filter arrangement B is everywhere a subset of the light allowed to pass through filter arrangement A. That is, there is no light allowed to pass by filter arrangement B which would be blocked by filter arrangement A.
  • a layer 410 substantially covers the projection screen (in a movie theater, for example), and to provide a layer 415 (another layer 40 in filter arrangement B) which filters light from the pair of projectors which are placed in positions comparable to eye positions 30 and 20, but which are substantially above or below the positions of the viewers.
  • Layer 415 could then be placed out of the line-of-sight of the viewers, and the light from the projectors after being filtered by layer 415 would then pass without hindrance or substantial alteration through layer 410, reach screen 12, and be reflected back to the viewer, passing again through layer 410 but not through layer 415.
  • screen 12 is a translucent back projection screen
  • the projectors are behind the screen
  • a layer 410 is behind screen 12
  • a layer 415 is between the screen and the viewers.
  • 114 will receive green light from the right image and red light from the left image, 113 will receive blue light from the right image and red light from the left, 112 has blue from the right and green from the left, 111 has red from the right and green from the left, etc.
  • This arrangement has some of the advantages of a movement permissive system. Since the area on the screen is only slightly wider than the area on the filter for any color, moving the user's eyes sideways does lose light from the correct image. However since at no point are the color segments of the same color from the two images contiguous to each other, moving the user's eyes sideways a moderate amount does not cause him to see light from the inappropriate image.
  • CMY cyan, magenta and yellow
  • CMYK black
  • L*a*b* LUV and XYZ.
  • a first method is simply to project narrow image picture elements through the wide filter areas.
  • the method mentioned above it contemplates projecting a full-color image through color filter strips to get individual color pixels projected onto particular parts of the screen.
  • the invention here is the idea of coordinating that projection with the position of the various color strips on the filter, so as to generate the desired situation, namely a situation producing autostereoscopic vision with a high level of movement permissiveness of the viewer.
  • Another method of accomplishing this is to project a full color picture onto a screen with colored stripes on the screen.
  • the idea is that if the screen is in color it will reflect only that color, so, e.g., if one projects red through a wide red filter onto a surface with red, green and blue strips, the red will reflect it and the green and blue should absorb it. Therefore, given a projection screen with relatively narrow colored strips, coordinated with a color filter layer with relatively wide color filter strips as described above, one can project colors through a filter area which is wider than the pixel size one desires to have on the screen, yet the pixels reflected from the screen will be of the desired size.
  • One application of this technique would be to project two full-color images from two projectors through a color filter as described above.
  • Using a normal projection screen this would produce a full-color autostereoscopic image (as described in PCT Publication W097/26577), yet would not create movement permissiveness, since the size of the projected color strips on the screen would be similar to the size of the filter areas through which they are viewed. If, however, one uses a projection screen with colored strips relatively narrow in size and appropriately placed with respect to the areas of the filter, then a permissive system as described above would be obtained.
  • layer 10 to be a reflective projection screen which itself has colored strips, each strip appropriate to reflect light of some color range and absorb (or otherwise not reflect) light of other color ranges.
  • Areas of color filtration on filter 40 can be made to overlap (as described above, for example with red-permissive filter areas at 52-54 and, say, green permissive areas at, say, 54-56. Similarly, areas that reflect particular colors and do not reflect other colors can also be combined in similar fashion.
  • FIG. 19 A single-projection autostereoscopic system is illustrated in Figure 19.
  • Figure 38 of PCT Publication W097/26577 and some of the discussion above, teaches a filter system (whether color or polarizing) at layer 40, projection of a left image from a left-eye position such as 30, and projection of a right-eye image from a right-eye position such as 20.
  • the discussion in PCT Publication W097/26577 demonstrates that for the filter systems under discussion there are multiple left eye and right eye positions, and that they are roughly equivalent with respect to projecting and viewing, so that if a left image is projected from a left- eye position then it is substantially visible from other left-eye positions and substantially not visible from other right-eye positions.
  • the present embodiment of the invention described herein contemplates projection of an image from a position which is neither the left-eye nor the right- eye position.
  • the point of projection is equidistant from the two, and at the same distance from the screen. In Figure 19 this is position 25.
  • the 'viewing window' that is the area within which the user can move to the left and to the right without seeing any of the inappropriate images, was unusually large. Nevertheless there exist, in those systems, areas which are not within the viewing window, because they are positions from which a viewer's eye might see light from both the left and the right image. This fact is now utilized, by projecting an image from such a position.
  • Figure 19 shows a projector at 25, equidistant from left eye position 30 and right-eye position 20.
  • 40 is an optical construction which is a composite color filter. Areas 52-54, 46-48, etc., on filter 40 permit the passage of red light. Areas 50-52, 44-46, etc., on filter 40 permit the passage of green light. Areas 54- 56, 48-50, 42-44, etc., permit the passage of blue light.
  • the number and selection and order of the particular colors in the example are chosen as examples of the general principle, and the invention is not limited to these particular examples.
  • a display system using filter 40 and presenting red light from a left image at 110 and 104, and red light from a right image at 107 and 113, and similarly green light from a left image at 114, 108, and 102, and green light from a right image at 111 and 105, and blue light from a left image at 112 and 106 and blue light from a right image at 109 and 103 would have the qualities discussed above, namely autostereoscopic viewing of a full-color image with a high degree of movement permissiveness of the viewer.
  • Lines 200, 210, 220, and 230 demonstrate how one produces that situation.
  • a projector at 25 projects a single image towards screen 10. The image is subdivided in such a way that, for a given color, pixels from the left image are projected alongside pixels from the right image, alternating across the screen. Using red as an example, one sees a red pixel from the left image projected between limits 200 and 210, and a red pixel from the right image projected between limits 220 and 230. The result is a red pixel from the left image on screen 10 in area 300, and a red pixel from the right image on screen 10 in position 400.
  • area 300 might be expanded to cover the right-hand side of area 111
  • area 400 might be expanded to cover the left-hand side of area 106. This might occur because of inaccuracy in the projection, or it might be done intentionally to increase the light intensity and color saturation of the projected image. In either case, the result would not be the destruction of the image and it's autostereoscopic features, but merely some reduction in the degree of permissiveness presented by the system.
  • red pixels were used for demonstration.
  • Clearly similar projection of appropriate green and blue pixels can be accomplished at the same time and in the same manner.
  • a green pixel from the left image would be visible to a left-eye position if it were projected through filter area 50 onto a part of screen area 108.
  • a green pixel from the right image would be visible to a right-eye position if it were projected through filter area 46 onto a part of screen area 105.
  • a blue pixel from the left image could be projected through filter area 54 onto screen area 112, etc.
  • Head-tracking aiming the apparatus at the eyes of the user in movement-permissive systems
  • U.S. Pat. No. 5,822,117 to Kleinberger et al. and PCT Publication W097/26577 describe various systems for head- tracking, systems which aim the 'sweet spot' (the area from which an eye can see the appropriate image and only the appropriate image) to adapt it to the changing position of the viewer in front of an autostereoscopic display.
  • movement permissive systems based on blocking light from a display, or on blocking light within a parallax barrier, and systems which achieve a large amount of movement permissiveness using a color filtration layer.
  • the viewing window of the color filter system as described above is extremely wide, on the order of 67 % of the inte ⁇ upillary distance ("LPD"), or more. This means that if a viewer's eye is exactly in the center of the viewing window (i.e., in the center of the "sweet spot"), the viewer can move about a 1/3 IPD to the left, and a 1/3 IPD to the right, without leaving that window, without diminishing the amount of light the viewer sees from the appropriate image, and without seeing any light from an inappropriate image. In the following this sweet spot is referred to as viewing window "region N". This is the area from which the viewer enjoys normal stereoscopic viewing.
  • region M a small region where the view is mixed: each eye can see some light from both images. If the viewer continues to move in the same direction the viewer enters a third region, "region R", where the parallax is reversed. In region R each eye again sees light from only one of the images, yet this time the light reaching each eye is from the inappropriate image.
  • region R the viewer's left eye is where his right eye should be, and his right eye is where his left eye should be.
  • the situation where each eye sees light from the inappropriate image is called "reversed parallax" in the following.
  • region M is relatively small, but region R is approximately the same size as region N. Since, in the color filter systems as described, regions N and R can be much wider than regions M, if the viewer's IPD is close to that for which the filter was designed, and if the viewer is at an appropriate distance from the display, then most of the positions from which the viewer views the display will not produce double images; rather, most positions will produce either a correct autostereoscopic image, or a reversed parallax image.
  • An extremely simple aiming system can consequently be achieved by (a) detecting when the viewer is at a position in a region R from which the viewer would see reverse parallax images, and when this situation is detected (b) switching the positioning of the left and right images on the display. That is, if the system detects that the viewer is in a region R from which the viewer sees inappropriate images, it modifies the display so that each pixel position which would normally have displayed imagery data from the left image will instead display imagery data from the right image, and vice versa. This has the effect of converting each region R into a region N, and vice versa, and is referred to as the "alternately positioned image" in the following.
  • the system having detected that the viewer entered a region R, displays the left image on the pixels or subpixels which had been showing the right image, and displays the right image on the pixels or subpixels that had been showing the left image.
  • the viewer without moving from his position in what had been a region R, finds himself in a region N from which the viewer can see the appropriate images of an autostereoscopic display.
  • stereoscopic display contexts interactive stereoscopic graphic games for example, may elicit frequent and very rapid (instinctive) movements of the viewer. It may be difficult for some head-tracking systems to rapidly accommodate in real time to such movements.
  • the following solution is presented: there are indications that during rapid or violent movement stereoscopic perception may be naturally interrupted in any case, by the behavior of the viewer and by the natural limitations of the human perceptual system (when one ducks to get away from a virtual monster, for example, one is likely to move and to turn one's head in a way that naturally interferes with stereoscopic vision. There also seems to be some relevant limitation in the ability to absorb such rapidly changing perceptual information at real-time speeds.
  • the display system discerning that rapid movement taking place, may briefly put itself into a non-stereoscopic mode, and transmit a monoscopic image to the viewer.
  • the advantage of this in the context of a barrier-based autostereoscopic system is clear: during display of the monoscopic image, there is no sweet spot: any pixels seen by any eye from any position will be appropriate. While in monoscopic mode the head-tracking system does not need to headtrack. Reversed parallax (which might destroy or interfere with the viewer's on-going 3D gestalt) is avoided because no parallax information is presented. When the viewer's movements become slower and more normal, stereoscopic display can be resumed and the head-tracking system used to discern the viewer's then- current position and movement, and adapt to it.
  • Head-tracking aiming the apparatus at the eyes of the user in a lenticular autostereoscopic system
  • a head-tracking system similar to that described above can also be implemented in the context of a lenticular autostereoscopic display.
  • Lenticular systems are one of the classic methods of stereoscopic display, and have been popularly available for many years. Lenticular systems typically do not require head-tracking because they produce a number of distinct views, and as the viewer moves in front of the display, the viewer's left and right eyes encounter a variety of compatible left and right views from various positions in front of the display. However, this effect is accomplished at the cost of low resolution, since many areas of the display are not being viewed by either eye of the viewer at any particular time.
  • a lenticular system is used not to present a large multiplicity of possible views, but rather to present a restricted number of views (at the limit, a pair of views only), then the resolution of the image it produces, while less than the maximum resolution possible to the display in non- stereoscopic viewing, is nevertheless much higher than that typically presented by classical lenticular displays.
  • the lenticular system's functionality is comparable in many respects to that of a parallax barrier system.
  • Such a system would also have a disadvantage similar to that of parallax barrier displays, namely that from some positions (regions N) the viewer would see an appropriate 3D image, from other positions (regions M) the viewer might see mixed views, and from some positions (regions R), the viewer would see reversed parallax (each eye seeing an inappropriate image).
  • a head-tracking sensor can inform the system when the viewer's eyes approach or enter a region R where they will see elements of the inappropriate images, and at that time the control element can direct picture elements to alternative parts of the display, thereby restoring a situation in which the viewer will again see proper parallax view, each eye seeing the appropriate image.
  • the combination of this simple electronic head-tracking method with a lenticular autostereoscopic display constitutes an effective electronic head-tracking solution with no moving parts.
  • This solution is particularly interesting in the context of lenticular autostereoscopic systems, because in such systems the regions M where the viewer would tend to see a mixed image (each eye seeing both appropriate and inappropriate light) can be made relatively small.
  • the essential idea is that when the viewing window is very wide, whether through the use of the color filter described above, or through the use of the permissive system described in Figures 3 l-33a of PCT Publication W097/26577, or through the use of a lenticular system, or through any other means of producing an autostereoscopic system with a sufficiently large viewing window, it is then possible to switch to an alternately positioned image when necessary, thereby avoiding reverse parallax (i.e., turning regions R into regions N), and also to avoid positions where the viewer would be able to see both images rather than only the appropriate image, by flipping the filter position between two alternative positions when necessary, thereby turning regions M into regions N.
  • reverse parallax i.e., turning regions R into regions N
  • Figure 20 which is similar to Figure 11 which illustrated various aspects of the color filter systems of the present invention.
  • Figure 11 it is taught that if a viewer's left eye, say, were at position 30, a red subpixel from a left image were displayed at 1 10, and areas 52, 53, and 54 of layer 40 were filter elements passing red light, then lines 500 and 510 would delimit the borders of the viewing window within which the viewer's left eye could move without losing any of the light from pixel 1 10.
  • the viewing zones are wide enough so that there is an area (between line 510 and line 520), which is within the sweet spot before the change in filter position, and which is also within the sweet spot after the change of filter position.
  • This is very convenient: it means that as the viewer's left eye transits from position 20 towards position 30, there is a period of time (after the eye passes line 520 and until it reaches line 510) during which the filter can be in either position, or indeed in transition between one position and the other, and the left eye during that time will enjoy an uninterrupted view of its appropriate pixel.
  • Moving the filter layer mechanically One option for moving filter layer 40 (or its filtering elements) is to do so mechanically.
  • the requirements of such a system are simple: in contrast to a system which tracks the eyes position with great exactitude, requiring, say, a stepper motor or similar device, the requirements of the current system can be satisfied with an arrangement consisting of a few biasing springs and a couple of attracting/retracting electro-magnets. Note that the movement required is approximately only the width of half an RGB triplet, which in most applications is likely to be less than a millimeter.
  • the mechanical implementation is simple because there are only two possible positions for the filter, and the distance to be moved is small and always the same.
  • One possible utilization of the system described might be to not move the filter during rapid lateral movement of the viewer, but rather to move it only for adapting the apparatus to the viewer's position once that is relatively stable.
  • major movement if the alternately positioned image is displayed when appropriate, the preponderance of the time the viewer will be seeing the appropriate image only, and during only a small fraction of the time the viewer will be seeing a double image (with each eye).
  • the option of whether to adapt the apparatus to the viewer's eye positions while the viewer is moving rapidly might depend on the specific application, and indeed it might be left to the choice of the individual viewer, some viewers and some applications requiring a simpler or quieter operation, others requiring 100 % stereoscopy at all times.
  • polarization orientation sensitive color filter materials There exist materials (called “polarization orientation sensitive color filter materials” in the following) which have the characteristic of providing color filtration (being transparent to certain color range(s) and opaque to certain color range(s)), yet they have this characteristic only to components of light with a particular polarization orientation, while being substantially transparent to light components of another polarization, for all color ranges.
  • Stereojet Inc. of California uses such a material to produce and display 3D images
  • Tektronix Inc. some years ago used a similar material in the production of color CRT displays which did not use a shadow mask.
  • Figure 22 shows a way in which such material can be used in an autostereoscopic head-tracking system, producing the desired effect of effectively 'moving' the filter elements of a color filter layer, while not physically displacing any parts of the apparatus. Note, though, that whereas the following discussion is couched in terms of the color filter systems described hereinabove, the method here presented is also applicable to use in an appropriately movement permissive system without color filtration.
  • Figure 22 is similar to Figures 11 and 20.
  • pixel 410 may be thought of as displaying a red sub-pixel from a left image, and pixel 413 may be thought of as displaying a red sub-pixel of a right image. If the light emanating from display 10 is polarized (as would be the case if display 10 is, e.g., an LCD), then polarizer 70 is unnecessary. If the light from display 10 is not polarized then polarizer 70 polarizes it.
  • Layer 180 is an element of switchable light rotating means such as a PI cell, controlled by control element 80 which receives information from a head position sensor 85.
  • Layer 40 is a color filter layer such as that described above in the discussions of Figure 11 , yet made of polarization orientation sensitive color filter materials.
  • the color filtering capabilities of layer 40 are taken to be active with respect to light in a polarization orientation A, and inactive (i.e., the material is transparent to all colors) with respect to light in a polarization orientation B, which is orthogonal to A.
  • Layer 45 is similar to layer 40 with two differences: (a) the color-filtering capabilities of layer 45 are active with respect to light in orientation B, and inactive with respect to light in orientation A; and, (b) the specific pattern of colors filtered by layer 45 is identical to that of layer 40, but is transposed (as shown by the drawing), a distance to the right equal to one quarter of the length of the repeating color pattern.
  • the apparatus functions as if layer 40 were a standard color filter as described above with reference to Figure 11, and as if layer 45 were transparent or absent.
  • control element 80 in response to information about the user's position from head-tracking sensor 85, causes layer 180 to become active in light rotation, the effect is to cause layer 45 to act as a color filter, and layer 40 to act as if it were transparent or absent.
  • the apparatus In use, when the viewer's left eye is at 30, the apparatus creates a viewing window (sweet spot) extending from line 500 to line 510. As the user moves to the right, at some time between the moment his left eye passes line 520 and before it reaches line 510, control element 80 causes layer 180 to switch its activation state, layer 45 becomes active in color filtration, and the sweet spot comes to be between line 520 and line 530, permitting the user to continue his rightward movement without losing his view of the appropriate autostereoscopic images.
  • a viewing window (sweet spot) extending from line 500 to line 510.
  • 470 is an area on layer 40 which passes e.g., red light, and it is followed on the layer by an area 460 of equal length which blocks red light, and this pattern is repeated across layer 40
  • 465 is an area on layer 45 which passes red light, and it is followed on the layer by an area 455 of equal length which blocks red light
  • the left extremity of area 455 is, in the current embodiment, placed even with the extreme left of area 460.
  • the two layers 40 and 45 are contiguous, substantially in the same plane, or might be constructed as a single layer with the appropriate characteristics.
  • layer 180 is inactive in light rotation and a viewer is placed with respect to the display and filter layer 40 in such a position that the viewer sees an autostereoscopic display in a first time, with a left image displayed on a first set of pixels and a right image is displayed on a second set of pixels, and then in a second time layer 180 is switched to be active in light rotation and the left image displayed on the second set of pixels and the right image displayed on the first set of pixels, then in the second time the viewer will continue to see an autostereoscopic image without changing his position, yet each eye will be seeing an appropriate image during the second time which is displayed by areas of the display which were blocked from that eye's view during the first time.
  • the phenomenon of persistence of vision in the human perceptual system will create the illusion that each of the viewer's eyes is seeing its appropriate image at full resolution. That is, the left eye will seem to see the left image on both the first and the second set of pixels, and the right eye will also seem to see the right image on both the first and second set of pixels.
  • This system is then an autostereoscopic display with a large viewing window (high movement permissiveness) as is the case in general with the color filter systems previously described, yet in contrast to them has the advantage of providing full rather than half resolution of the displayed images.
  • Moving the image with respect to a filter on a sub-pixel basis can also be accomplished by moving the image with respect to a filter or barrier, rather than, or in addition to, moving a filter with respect to an image.
  • One difficulty in moving an image with respect to a filter or barrier is more conceptual than practical: many display devices being constructed on the "RGB" model, both for physical and for historical reasons images tend to be thought of, and handled, as arrays of discrete pixels, each pixel being an RGB triplet, a combination of a red, a green, and a blue element. Since much display hardware is built on this principle, there is a natural tendency to display images in such a manner that a three-color pixel element of the image is physically displayed by a three-color display element of the display hardware.
  • RGB display seen through a standard parallax barrier, a barrier which alternates opaque areas with transparent areas.
  • a barrier which alternates opaque areas with transparent areas.
  • such a system presents one pixel (e.g., an RGB triplet) from a left image, and then one pixel (another e.g., RGB triplet) from a right image, and the barrier is arranged to be of such a size and position and orientation that the left eye sees the left-image pixel and the right-eye the right image pixel.
  • the net effect is to move the image slightly sideways.
  • the portion of the display showing, e.g., a left-image pixel i.e., a triplet of colors taken from a left image
  • the sideways displacement would be approximately that of a third of a pixel each time.
  • This principle is of course not limited to the specific example of RGB triplets, and can be applied to any display system based on presentation of color images using sub-pixels of discrete colors, regardless of the particular colors used (i.e., not necessarily red, green and blue), and regardless of their number (i.e., not necessarily triplets).
  • the principle is now further expanded with respect to a specific example, with further advantages for head-tracking systems.
  • This example refers to a classical parallax barrier (i.e., one in which transparent areas alternate with opaque areas).
  • This example uses the principle described in the preceding paragraphs, and further provides some movement permissiveness, the combination producing a simple and efficient barrier-based head-tracking system with no moving parts.
  • An additional aspect of this example is that it uses a barrier whose transparent areas are of a size and placement such as to allow the viewer to see strips of approximately the width of an RGB triplet on the display, yet the method assigns one or more additional sub-pixel elements to the display of, e.g., a left-image pixel.
  • layer 100 is a triplet-based display screen.
  • an image pixel is made up of 3 sub-pixels, for example areas 15, 16, and 17 of layer 10, which constitute an RGB triplet.
  • Layer 40 is a parallax barrier, made of opaque strips that substantially block light from the display alternating with transparent strips that substantially permit the passage of light from the display.
  • pixel elements from each image are presented on more than three sub-pixels of the display, rather than on the traditional three sub-pixels. In the example presented in Figure 23, four sub- pixels are used.
  • the size and placement of transparent segments on barrier 40 are such as to allow the viewer's eyes (at 20 and 30 in Figure 23) to see a segment of the display substantially corresponding to the width of an RGB triplet on the display.
  • the width of the opaque areas on barrier 40 is larger than the width of the transparent areas, according the principles of the movement- permissive system.
  • the ratio of the width of the opaque areas to that of the transparent areas is 5/3, as shown. Note what happens if subpixels 14, 15, 16, and 17 are used to display information from a left image. The viewer's left eye 30 sees all of subpixels 15 and 16, and a portion of subpixels 14 and 17.
  • subpixel 15 presents red light from the left image
  • subpixel 16 presents green light from that image
  • both subpixel 14 and subpixel 17 present blue light from the left image. Since the width of the transparent area through which these pixels are viewed is selected so as to allow the viewing of an RGB triplet, the eye's total exposure to blue elements of the display in this area of the display (the eye's exposure to area 14 plus the eye's exposure to area 17) is substantially the same as that eye's exposure to area 15 and to area 16. As eye 30 moves to the right, it sees less and less of the rightmost sub- pixel 17, but it also sees more and more of the leftmost sub-pixel 14.
  • the eye always sees the two middle sub-pixels 15 and 16, and a constant amount of what amounts to a third sub-pixel, made up either of all of the right sub-pixel 17 and none of the leftmost one 14, or all of the leftmost sub-pixel 14 and none of the rightmost one 17, or else of a kind of composite sub-pixel made up of the parts of both 14 and 17 that are not hidden by the light blocking stripes of layer 40.
  • Eye 30 can move between lines 500 and 510 and not see any significant change in the coloring or brightness of the pixel. As long as the viewer's left eye moves within the window defined by lines 500 and 510, the eye will see an appropriate pixel from the left image.
  • providing transparent areas of a width appropriate for the viewer's eye to see the width of an RGB triplet on the display, while also utilizing four (or more) rather than three sub-pixels to display light from e.g., the left image, has the effect of enlarging the sweet spot of the parallax barrier, without causing a degradation of the image's color, and without affecting the image's quality except for a minor reduction in resolution.
  • Control element 80 receiving information about the position of the viewer from head-tracking sensor 85, can move the image sideways one sub-pixel at a time as described above, thus accommodating for the movement of the viewer. Consequently, in any position, through each transparent area of layer 40, each eye of the viewer sees a space, 3 sub-pixels wide, that contains information corresponding to a single pixel of the image appropriate to that eye.
  • the apparatus combines the movement permissive system with a system for moving the image on the display on a sub-pixel basis, to form a competent head-tracking system for autostereoscopic display.
  • control element 80 modifies the distribution of pixels on the display. Area 13, previously used to display green light from the right image, is made to display green light from the left image. Area 17, used until now to display blue light from the left image, is now used to display blue light from the right image. In corresponding fashion, the function of subpixels of display 10 is modified where appropriate, e.g., 17, 18, 19, and 20 display light from a right image, as do 9, 10, 11, and 12.
  • the eye can move continuously in the sideways direction. Movement permissiveness permits small movements with no degradation of the autostereoscopic image.
  • alternation in functionality of the subpixels of display 10 (the choice of which subpixels display light from the left image and which subpixels display light from the right image) allows the apparatus to adjust to the viewer's larger motion. The result is an apparatus which allows for head-tracking in an autostereoscopic display apparatus with no moving parts.
  • continuous or nearly continuous phosphor strips are used, which are similar to those used in the construction of, e.g., the Sony Trinitron screens, yet in those strips are arrayed not in the vertical direction, but in a non-vertical direction (in the preferred embodiment, they are horizontal).
  • This might be implemented either modifying the construction of the display, or simply by using standard television or monitor hardware, and re-orientating the image displayed on that hardware by turning it sideways, so that the top of the image appears on what would normally be the side of the monitor, and the sides of the image appear on what would normally be the monitor's top and bottom.
  • Such a display system would now be capable of modifying the position of the image in a sideways direction continuously or nearly continuously, using digital and/or analog techniques similar to those which are currently used for adjusting the position of an image on a television screen or computer monitor. Given such a capability, it is an easy matter to place the mechanisms controlling the image position under the control of a control element which determines the appropriate position for the image, based on information supplied by a head- tracking system in a manner similar to that described with respect to various systems presented herinabove. Since the position of the image can be moved continuously or nearly continuously, this system does not need to be highly movement-permissive.
  • the preferred embodiment would be only slightly permissive, so as to maximize the amount of light transmitted, and would use only that degree of movement permissiveness as would be required to eliminate the need for extreme accuracy of the head-tracking system, and to allow for variations in inte ⁇ upillary distances among viewers.
  • Computer-driven projection systems based on simultaneous projection of three colored images through three independent liquid crystal arrays are also examples of such systems, as are computer-driven projection systems based on time-multiplexing of colors, that is projecting an image of one color on all of a display screen (or a large area of a display screen), then projecting an image of another color, then projecting an image of a third color, and alternating these images quickly enough so that the phenomenon of persistence of vision in the human perceptual system gives the impression of continuous viewing of all colors over all the screen.
  • full color displays can be utilized together with the techniques presented above, to produce autostereoscopic systems.
  • One method is simply to cause the display system, although it is capable of presenting all colors in all areas of the screen, to instead display distinct colors in distinct areas.
  • the display initially presents the red light from a pixel from, say, a left image in an area A of a display, and the green component of that pixel in an area B to the right of A, and the blue component in an area C to the right of B, then, say, the red light from a right- image pixel in an area D to the right of C, then whereas if one wanted to move those images over a classical RGB display, the smallest move that could be accomplished would be to move 5 the red light of the left image pixel from A to D. Yet in the case of a full-color display which can present light of any color in any area, it is possible to move the red element from A to B, the green element from B to C, and the blue element from C to D.
  • the mechanical solution might be used to shift back and forth one and one half area lengths (e.g., between P and Q, or Q and R, or R and S, or S and P), while the electronic solution might be used to shift 3 area lengths, e.g., back and forth between P and R, or between Q and S.
  • the apparatus would be, say, in position P.
  • shifting the mechanical system would put it into Q position, unshifting the mechanical but shifting the electronic would but it into R position, and shifting both systems would put it into S position.
  • a system as herein described provides several advantageous capabilities.
  • the technique of alternately positioned image can be used in this system for another pu ⁇ ose, namely that of providing for full- resolution viewing of the display.
  • the filter position from its position as defined by the requirements of the head-tracking function to its opposite position (e.g., from P to R, or from Q to S, or from R to P, or from S to Q), then one creates a situation in which the viewer who first sees the left image on a first set of areas of the display and the right image on a second set of areas, now sees the right image on the first set of areas of the display and the left image on the second set of areas.
  • the system rapidly alternates between the original position of the image and the alternately positioned image, while in a coordinated manner also switching between the position of the filter determined by the requirements of the head- tracking system, and the opposite position of the filter, then the result will be that the viewer will see a rapid alternation of image pixels such that (a) each eye sees only light from its appropriate images at all times; and (b) each eye will see light from its appropriate image from all or almost all areas of the display. If this switching operation is done sufficiently rapidly (e.g., at 50 Hz or faster per eye), then the phenomenon of persistence of vision in the human visual system will create the impression of a full-resolution image, even though at any given instant each eye is actually receiving light from only 50% or less of the display's subpixels.
  • the system herein described provides for full resolution, with a very minimal or no impression of flickering, and also provides for head-tracking, in an autostereoscopic display.
  • Full-resolution head-tracking system based on a color filter system, with no moving parts
  • Layer 40 is a color filter layer.
  • Polarization orientation sensitive color filter materials are used in its construction, as described above.
  • the color filter is represented here in simplified form: areas 460 may be taken to block e.g., red light when that light is in a particular orientation T, and not to block red light in the orthogonal orientation V. Areas 470 may be taken to block, e.g., red light when that light is in polarization orientation V, and to pass light in orientation T. It should be understood that this simplified representation of the color filter is intended to represent a filter capable of filtering substantially all the colors of the display, in the manner described above with reference to Figure 11.
  • Figure 22 can also be taken to describe an apparatus built around a parallax barrier: in this case areas 460 may be taken to block all light when that light is in orientation T, and not to block light in the orthogonal orientation V, while areas 470 may be taken to block all light which is in orientation V, and to pass light in orientation T.
  • Layer 45 is a color filter with the same characteristics as layer 40, with the difference only that areas 465 on layer 45 block color (e.g., red light) when the light is in orientation U, and areas 455 do so when the light is in orientation W, where U is 45 degrees from T, and W is orthogonal to U. Also, as shown in Figure 22, areas 465 and 455 of layer 45 are displaced sideways in comparison of those of areas 460 and 470 of layer 40, as detailed in the earlier discussion of Figure 22.
  • Light turning (light retarding) unit 180 is a unit capable of turning the orientation of the polarized light passing through it, so that the light reaching layer 40 is polarized in one of several orientations.
  • the light arriving at layer 40 will be in one of the four orientations T, U, V, and W.
  • This can be accomplished in various manners, such as by using twisted nematic liquid crystals under controlled voltage, so as to turn the incident light to a desired degree, or alternatively by using an arrangement of PI cells in appropriate orientations such that, by selective activation and inactivation of the PI cells, light of the desired orientations can be obtained under electronic control.
  • the following descriptions of the behavior of the system with respect to "light” may be taken as if they referred to light of a particular color range, e.g., red light, with the understanding that behaviors true of a single particular color (red, in the example) can be generalized to other colors or color ranges (e.g., green and blue), and that the structure of the filter (the spacing and relationship of filter areas of different colors along the filter) are as described above with respect to Figure 1 1.
  • Light reaching layer 40 in T orientation will be completely blocked by areas 470 and will pass substantially unhindered by areas 460.
  • Light reaching layer 40 in orientation V will be completely blocked by areas 460 and will pass substantially unhindered by areas 470.
  • Light in U or in W orientations reaching layer 40 is oriented at 45° with respect to the axis of orientation of both the areas 460 and 470, consequently, it will be somewhat diminished. (If incidental light losses are ignored, the theoretical amount of light to pass under those conditions is the original intensity I multiplied by sin(45°). The light will be diminished equally by areas 460 and 470. Light which successfully passes layer 40, then, will be in two different intensities: that which entered in T or V will have the original intensity, that which entered in U or W will have intensity (I sin(45°)).
  • Light arriving in the T orientation encounters a blocking barrier formed by areas 460.
  • Light arriving in the U orientation encounters a blocking barrier formed by areas 465.
  • Light arriving in the V orientation encounters a blocking barrier formed by areas 470.
  • Light arriving in the W orientation encounters a blocking barrier formed by areas 455.
  • the result is a standard diminution not dependent on the initial orientation.
  • the light (originating in display 100) acts as if it had encountered a color filter (or, under a slightly different construction, a parallax barrier) in one of four possible positions, the same positions P, Q, R, and S which were previously shown to enable both head-tracking and full-resolution displays in an autostereoscopic system.
  • pixels and/or subpixels color elements of pixels, i.e., sub-picture elements
  • the speed of the oscillator is set to correspond to the pixel density (e.g., the density of the dots on the CRT color mask, or the equivalent), then the result can be that each RGB triplet gets its information from a different image from that of its immediate neighbor.
  • the color signals are available independently, then control of the phase relationships between the oscillators controlling the source of the signals of each individual color will make it possible to create the pattern of colors appropriate for the color filter system described above, as well as that appropriate to the alternating-color filter described in the context of Figure 40 of PCT Publication W097/26577.
  • Figure 21 is an example of such a system. Shown in Figure 21 is a rear projection display for autostereoscopic vision.
  • the basic components of a rear projection system are projector 5010, a rear projection screen 5040, a static polarizing layer 5050, made of strips 5060 alternating with 5070, which have orthogonally oriented planes of polarization. Inte ⁇ osed between projector 5010 and the projection screen 5040, we will place two additional layers.
  • the first layer, placed closer to the projector is a uniform polarizer 5020.
  • the second additional layer, placed between polarizer 5020 and projection screen 5040, is an active LC element with individually addressable pixels 5030 (similar to layers 55 and 56 in Figure 5 and to layers 130 and 150 in Figures 6-9).
  • projector 5010 is an LCD projector, it inherently includes a polarizer, and there is no need to use polarizer 5020.
  • One last layer is a liquid crystal shutter 5200, which is placed between active layer 5030 and screen 5040, or between screen 5040 and static layer 5050.
  • elements 5030 and 5200 will be positioned relatively close to projector 5010, so that they can be of relatively small size and consequently relatively inexpensive.
  • Active layer 5030 is made of an addressable liquid crystal array and can be made into strips under software control.
  • An alternative is to have active layer 5030 made of addressable strips, without vertical addressability. For an example, say that pixels 5100, 5140, 5150, 5160, are turned off and pixels 5110, 5120, 5130, and 5170 turned on.
  • Light passing through polarizer 5020 is polarized uniformly in one plane. If it then passes through an active region of layer 5030 (e.g., pixels 51 10-5130), its plane of polarization is not changed, and will create a polarized light region on the rear projection screen 5040, of the same orientation. If, on the other hand, it passes through a section of layer 5030 that is not activated (e.g.
  • the planes of polarization of layers 5030 and 5050 are made to be of the same/orthogonal orientation, and the size of the strips on layers 5030, 5050 are set appropriately, one then obtains a system identical to the original system as described in the PCT Publication W097/26577, where the system can track the viewer's movement and adapt so that the viewer can still see the image correctly, despite the viewer's movement.
  • the shutter layer With the shutter layer, the system is able to switch which eye sees which part of the screen and this enables one to show the same parts of the screen to both eyes, in a sequential manner.
  • This system enables one (using information received from an external eye location device) to effect head-tracking by turning on a pixel on one side, and turning one off on the other. For example, one forms a 3 pixel strip by turning on pixel columns 5110, 5120, 5130, while leaving off pixels 5100 and 5140, 5150, 5160, etc. If the viewer moves to the left, one can turn pixel 5100, 5170 on and turn off pixel 5160. In effect, the strip was moved one pixel to the left, and the viewer is again in the right location. Note that layer 5030 can be placed very close to projector 5010, and thus can be very small. This reduces significantly the manufacturing cost.
  • This system can also be constructed without shutter element 5200.
  • This element has the effect of reversing the state of layer 5030 as described in detail in PCT Publication W097/26577. If one desires to have this element removed from the system, layer 5030 will need to reverse it's state itself (e.g., in the first state, pixels 5100, 5140, 5150, 5160 are on, and pixels 51 10, 5120, 5130, 5170 are off. In the second state, pixels 5100, 5140, 5150, 5160 are off, and pixels 5110, 5120, 5130, 5170 are on).
  • the effect of the two-layers is reversed (e.g., in the first state the left eye sees the whole screen and the right eye sees nothing, and in the second state the right eye sees the entire screen and the left eye sees nothing)).
  • the areas previously seen by the left eye are now seen by the right eye, and the areas previously seen by the right eye are now seen by the left eye.
  • the areas blocked from view by the left eye are now blocked from the view of the right eye, and the areas previously blocked by the right eye are now blocked from the view of the left eye.
  • layer 5030 is capable of switching fast enough, and it is switched in the same way as layer 5200 would be switched, (i.e., at the same speed and using the same source signal) both eyes would be able to see the whole screen in a sequential manner.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Testing, Inspecting, Measuring Of Stereoscopic Televisions And Televisions (AREA)

Abstract

L'invention concerne généralement des systèmes et procédés de vision tridimensionnelle d'affichages et projections. Dans un mode de réalisation, deux couches (50, 90) constituent des filtres uniformes polarisants, une couche biréfringente, dotée d'éléments pouvant être commutés individuellement (60), étant placée en sandwich entre ces deux couches (50, 90), lesquelles constituent une couche de parallaxe (40) située à une certaine distance d'un affichage (10). Ce positionnement ainsi que l'existence de zones opaques sur la couche de parallaxe (40) permettent à un spectateur de voir une image tridimensionnelle. Les éléments individuels (601-605) de la couche biréfringente (60) sont commandés par un module de commande (80) qui communique avec un capteur (85) de poursuite de position de la tête, ce qui permet à ces éléments individuels (601-605) de la couche biréfringente (60) d'être sélectivement activés ou désactivés, en fonction de la position de la tête du spectateur.
PCT/IL2000/000534 1996-01-22 2000-09-05 Systemes et procedes de vision tridimensionnelle WO2001018589A1 (fr)

Priority Applications (3)

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US10/070,355 US7190518B1 (en) 1996-01-22 2000-09-05 Systems for and methods of three dimensional viewing
EP00956767A EP1214620A1 (fr) 1999-09-07 2000-09-05 Systemes et procedes de vision tridimensionnelle
AU68628/00A AU6862800A (en) 1999-09-07 2000-09-05 Systems for and methods of three dimensional viewing

Applications Claiming Priority (12)

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US15213399P 1999-09-07 1999-09-07
US60/152,133 1999-09-07
US16835199P 1999-12-01 1999-12-01
US60/168,351 1999-12-01
US17502600P 2000-01-07 2000-01-07
US60/175,026 2000-01-07
US17839000P 2000-01-27 2000-01-27
US60/178,390 2000-01-27
US18576400P 2000-02-29 2000-02-29
US60/185,764 2000-02-29
US21838700P 2000-07-14 2000-07-14
US60/218,387 2000-07-14

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WO2002080579A2 (fr) * 2001-03-28 2002-10-10 Dimensional Developments Aps Affichage 3d a auto-alignement
WO2002080579A3 (fr) * 2001-03-28 2004-03-04 Dimensional Developments Aps Affichage 3d a auto-alignement
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