WO1984004405A1 - Sytemes video stereoscopiques - Google Patents

Sytemes video stereoscopiques Download PDF

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Publication number
WO1984004405A1
WO1984004405A1 PCT/US1984/000626 US8400626W WO8404405A1 WO 1984004405 A1 WO1984004405 A1 WO 1984004405A1 US 8400626 W US8400626 W US 8400626W WO 8404405 A1 WO8404405 A1 WO 8404405A1
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WO
WIPO (PCT)
Prior art keywords
screen
filter element
images
observer
density
Prior art date
Application number
PCT/US1984/000626
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English (en)
Inventor
Lenny Lipton
Original Assignee
Lenny Lipton
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 Lenny Lipton filed Critical Lenny Lipton
Priority to AU28631/84A priority Critical patent/AU2863184A/en
Publication of WO1984004405A1 publication Critical patent/WO1984004405A1/fr

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B35/00—Stereoscopic photography
    • G03B35/18—Stereoscopic photography by simultaneous viewing
    • G03B35/24—Stereoscopic photography by simultaneous viewing using apertured or refractive resolving means on screens or between screen and eye
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/30—Image reproducers
    • H04N13/332—Displays for viewing with the aid of special glasses or head-mounted displays [HMD]
    • H04N13/334—Displays for viewing with the aid of special glasses or head-mounted displays [HMD] using spectral multiplexing

Definitions

  • the subject invention is related to improved stereoscopic video systems. More particularly, improved stereoscopic projection and viewing systems are described for use in television, motion pictures or video games.
  • the Pulfrich illusion appears to be based upon the difference in time required to assimilate visual impressions of objects having different degrees of brightness. More particularly, the signal transmitted along the optic nerve is thought to be delayed when the image perceived is dimmed due to the filter. Where the object is stationary, the time lag will not affect the perception of the location of the object. However, when the object is moving, right and left eye images received in the brain will correspond to different locations and generate a retinal disparity. The brain interprets the retinal disparity by locating the object at a point either closer to or farther from the actual distance of observer. The effect is increased as the horizontal velocity component of the viewed object is increased.
  • the Pulfrich illusion can be utilized to generate pleasing and powerful stereographic images.
  • commercial use of the illusion has been limited due to a variety of shortcomings associated witn the systems in the prior art.
  • the subject disclosure is intended to provide solutions for overcoming a variety of these shortcomings.
  • some of the solutions presented herein may also be applicable to other stereoscopic systems.
  • Pulfrich. images are observed by placing a neutral density filter over one eye of the observer.
  • Dudley suggests that the filter should have a neutral density (ND) of .9 to 1.1.
  • ND neutral density
  • a neutral-density filter having a density of 1.0 transmits 10% of the light energy which it receives.
  • the filter is used to produce a visual time lag that induces the brain to impart a stereoscopic effect to the moving image.
  • One of the stronger visual cues is that of interposition. Stated simply, where an object appears to move in front of a second object, the object in the foreground should obscure the view of the background object. This type of visual cue can be used to enhance stereoscopic effects. For example, when moving objects are generated by computer for video display in a video game, the foreground objects can be made to electronically obscure the background objects.
  • Pulfrich illusion in commercial systems also appears to have been limited due to the .complexities of creating Pulfrich images.
  • stereoscopic images are prepared through an expensive and time- consuming cell animation technique. Therefore, it would be desirable to provide improved methods for generating Pulfrich images for use in television, movie and arcade game applications. Accordingly, it is an object of the subject invention to provide a new and improved means for viewing Pulfrich images.
  • the subject invention provides for a variety of improvements associated with the generation of stereoscopic images.
  • One group of improvements includes means for enhancing viewing of Pulfrich images.
  • spectacles are provided for covering both eyes of the observer.
  • the spectacles include a first filter element adapted to be aligned with one eye of the observer and a second filter element adapted to be aligned with the remaining eye of the observer.
  • One of the filter elements is provided with a density greater than the other filter element. The density difference functions to produce a time lag for inducing the retinal disparity necessary for viewing Pulfrich images.
  • use of two filter elements reduces eye strain and fatigue.
  • the subject invention also includes improved systems for reducing conflicting visual cues.
  • the first system includes a border or surround having a central opening aligned with the viewing area of a two-dimensional screen.
  • the border is mounted in front of and in spaced relationship to the screen in a manner such that objects which appear to an observer to be in front of the screen also appear behind the border.
  • the conflicting visual cue of interposition which can arise when an object crosses a vertical side edge of the screen, is substantially reduced.
  • the latter conflicting cue of interposition can also be attenuated by reducing the speed of an object as it approaches a vertical side edge of the screen.
  • the stereoscopic effect of an image is enhanced when its horizontal velocity component is increased. Accordingly, by reducing the object's speed as it approaches the vertical side edges of the screen, the object will appear to move towards the surface of the screen.
  • contrary cues such as interposition are attenuated enhancing the overall stereoscopic effects.
  • the subject application also discloses improved systems for creating Pulfrich effect images.
  • Pulfrich images are generated by rotating the image field relative to a camera. The plane of rotation of the field is perpendicular to the camera. As discussed below, this arrangement permits the generation of highly realistic stereoscopic effects.
  • the subject invention also includes a means for providing stereoscopic foreground and background images utilizing the Pulfrich illusion. This result isachieved by having one image move relative to the other images in a manner such that the background will appear to be behind the foreground image. In one embodiment of the subject invention, this arrangement is carried out using a chroma-key system with the moving image generated by computer or travelling matte. In another embodiment of this sytem, background images are formed on a rotating planar disc.
  • the rotating disk provides the horizontal velocity component necessary to create the Pulfrich illusion.
  • the subject application also discloses a system particularly adapted for use with video games capable of producing complex interactive stereoscopic images.
  • the complexity of the images portrayed on the screen are limited by computing speed and memory size. Accordingly, it is difficult to produce complex stereographic images utilizing known video projection techniques.
  • a system which includes a means for actively generating stereoscopic images on the screen. These images may utilize the Pulfrich effect or may rely on other stereoscopic techniques, such as image selection by polarized light.
  • a transparent overlay is mounted on the surface of the screen and includes passive stereoscopic images.
  • stereoscopic images may be formed from well known techniques, such as anaglyphs or vectographs.
  • a combination viewing means is provided which permits the observance of both the active and passive stereoscopic images.
  • video games may be provided wherein moving objects interact with the stereoscopic overlay to produce complex stereoscopiceffects while utilizing limited active display techniques.
  • Figure 1 is a perspective view of the dual density filter spectacles of the subject invention.
  • Figure 2 is a perspective view of alternate embodiment of the spectacles formed in accordance with the subject invention.
  • Figure 3 is a perspective view illustrating the use of a surround for reducing conflicting stereoscopic cues.
  • Figure 4 is a front elevational view of a combination system for generating Pulfrich effect images.
  • Figures 5A through 5C are illustrations of an alternate embodiment for generating stereoscopic images utilizing the Pulfrich effect.
  • Figure 6 is a perspective view of a combination system for generating complex stereoscopic images particularly adapted for video games.
  • FIGS. 1 and 2 there are illustrated two forms of viewing means for observing the Pulfrich illusion.
  • the Pulfrich illusion was viewed by covering one eye of the observer with a neutral filter having a density in the range .9 to 1.0.
  • the neutral density filter reduced the brightness of the object reaching the covered eye creating a time lag along the optic pathway.
  • the time lag creates a retinal disparity in the observed position of the object such that the brain assigns an apparent position different from the actual position.
  • This illusion can be successfully created with a single filter element.
  • this difficulty can be overcome by viewing Pulfrich images through a pair of filters having different densities.
  • This approach is illustrated in Figure 1 wherein a pair of neutral density filters 10 and 12 are mounted in a frame 14. Filters 10 and 12 are intended to be neutral density filters having a density difference sufficient to permit the stereoscopic viewing of
  • the density imbalance may be reduced to relieve eye strain while still permitting the perception of the illusion.
  • the density of the filters may be varied in accordance with the level of stereoscopic effect desired. However, the selection of the particular density levels should be governed by a few criteria. For example, since the brightness of the image reaching the eye is restricted by the filter, it would be desirable to use filters having the lowest effective density. More importantly, because of the undesirable effects of extreme density imbalance, it would be desirable to have the difference between the left and right filters 10 and 12 to be as small as possible.
  • the optimum density for the low density filter 10 was inthe range of .2 ND to .3 ND.
  • a .3 ND is equivalent to one photographic stop, or a reduction in light intensity by one-half.
  • the range in density values for the higher density filter 12 lies between .7 ND and 1.4 ND.
  • problems such as eye strain will be minimized.
  • the density difference is reduced, the stereoscopic effect is also reduced. It has been found that a good balance between these factors can be achieved when the density difference between the filters is less than .9 ND but greater than .4 ND. In this range, the large imbalances used in the prior art are avoided such that eye fatigue and headaches can be reduced.
  • filters 10 and 12 are neutral density filters.
  • a neutral density filter functions only to reduce light intensity and does not effect the color spectrum. It is to be understood, that similar effects can be achieved using colored .filters where the color filters also reduce light intensity to an equivalent degree.
  • the left filter 12 (as worn by the user) is shown having greater density than the right filter 10. This arrangement is consistent with standard conventions, adopted in most prior art references. However, it is to be understood that the subject invention is not to be limited thereby. For example, if the density of the lenses is reversed, an object which had appeared farther away than it actually was, would now appear to be closer. The apparent location of a moving object is also a function of the direction in which it travels. For the remainder of the application, objects which have a horizontal velocity component moving from left to right, when seen with the denser filter on the left eye, appear to be farther away than they actually are and thus have a positive effective parallax.
  • the dual filter spectacles illustrated in Figure 1 satisfy the requirements necessary for viewing the Pulfrich illusion by creating a difference in the illumination received in the eyes of the observer. While the spectacles illustrated in Figure 1 can be produced at relatively low cost, if it was desired to distribute them to a very large number of people, the overall cost could be significant. Accordingly, it is another object of the subject invention to provide an alternate viewing means for observing the Pulfrich illusion which may be manufactured at extremely low cost. The alternate viewing means is illustrated more particularly in Figure 2.
  • Figure 2 shows a pair of spectacles 20 having a first slit 22 and a second slit 24 formed therein.
  • slits 22 and 24 are elongated and rectangular in shape, with their longer dimension being in the horizontal orientation.
  • only slit 24 is intended to serve as a light attenuator, while slit 22 is provided for the comfort of the wearer.
  • the height "H" of slit 24 should be in the range of .3 mm to 1.0 mm. If the height is less than .3 mm, horizontal bands may be observed due to diffraction effects.
  • the slit height is greater than 1.0 mm, there is insufficient light attenuation to observe the Pulfrich illusion.
  • Optimal stereoscopic effects have been achieved with a slit height "H" of .5 mm, which provides sufficient light attenuation without distracting diffraction bands.
  • the surface of the spectacles facing towards the observer are darkened to reduce reflections.
  • the opening 24 should be defined to achieve a reduction in light intensity in the range of seventy-five to ninetyseven per cent. Optimum effects are achieved where light intensity is reduced approximately ninety percent.
  • aperture 24 can be configured in shapes other than rectangular, such as a circular opening. However, because the aperture has to be aligned directly with the eye, the rectangular configuration is preferred.
  • aperture 22 is provided for aesthetic and comfort reasons, the subject invention should be construed to include a shield covering only one eye of the observer and having a single aperture formed therein. Because of the extremely low cost of manufacture of the subject spectacles 20, they could be widely distributed for promotional purposes as, for example, an insert to a magazine for viewing television images.
  • a more desirable arrangement for generating depth is to speed up the foreground images in a manner to generate negative parallax.
  • the distant clouds will move more slowly than the nearer trees and houses.
  • the use of negative parallax has advantages in that the images of the objects conform to everyday expectations.
  • problems with conflicting visual cues, such as interposition can arise.
  • two systems are disclosed for attenuating the conflicting cue of interposition.
  • the first of those systems is illustrated in Figure 3 and consists of a border means or surround 30 which is mounted in front of the viewing screen 32.
  • the surround 30 has a central opening 34 which is aligned with the screen 32.
  • the surround is spaced from the front of the screen in an amount sufficient to create a false border, behind which all objects will appear.
  • objects having a negative effective parallax will appear to be in front of the screen 32 and behind the border means 30. Since the viewer will not expect the object to obscure the border means 30, the conflicting cue of interposition is eliminated and stereoscopic effects are enhanced.
  • the distance which the border means 30 is spaced in front of the screen 32 will vary based upon the size of the screen and the distance of the audience from the screen. In a typical television display, the border means may be spaced in front of the screen several inches. For motion picture or large screen displays, the distance from the border means to the screen will be measured in feet. The best distance can be determined empirically and will depend upon the effective parallax values created by the Pulfrich effect. Preferably, a fairly rigid, dark material is used to form the border means 30.
  • the border means 30 can be utilized not only with Pulfrich images but any other conventionally projected stereo pairs wherein objects are generated with negative effective parallax.
  • a border means which is continuous, as illustrated in Figure 3, may be preferred for a number of reasons including ease of mounting or aethestic considerations.
  • an effective border means can be defined by a pair of vertical border members 36 and 38 disposed adjacent the vertical side edges of the screen.
  • the vertical border members 36 and 38 are mounted in front of and in spaced relationship to the screen, an amount such that objects which would appear to an observer to be in front of the screen appear behind the border members.
  • the use of border means 30 represents one way of reducing conflicting stereoscopic cues.
  • conflicting cues arising in Pulfrich effect images can also be attenuated by controlling the motion of the moving objects on the screen.
  • the degree of retinal disparity or generated parallax is, in part, a function of the horizontal velocity component of the moving object.
  • conflicting visual cues can be overcome by reducing the horizontal velocity component of the object when it is adjacent a vertical side edge of the screen. By this arrangement, the generated parallax is reduced such that the observed location of the object will appear to move smoothly back towards the surface of the screen at the side edges thereof.
  • the speed of an object is accelerated after it enters the screen area and is reduced when it approaches the opposite border prior to exiting the screen.
  • This approach is particularly useful where the object has a negative parallax and appears in front of the screen. In this situation the observer will expect the object to obscure the vertical side edges of the screen. However, if the velocity of the object is reduced, it will appear to move smoothly back towards the screen surface such that the sharp contrary cue of interposition will be attenuated.
  • FIG. 4 there is illustrated one proposed arrangement for creating stereoscopic images utilizing the Pulfrich effect wherein an image field is rotated relative to a camera. More particularly, models 40 and 41 are supported by a turntable 42. Turntable 42 is rotatable about a vertical axis 44 in a direction as illustrated by arrows A. The plane of rotation of the turntable is intended to be substantially perpendicular to the image which will be projected on the screen. As discussed below, by rotating the models about the turntable, relatively true to life stereoscopic effects can be generated.
  • Model 40 is located such that the central axis 44 of rotation passes through the center of the model 40.
  • a point on the midline 44 at the front of the model will have a maximum horizontal velocity moving from right to the left.
  • its horizontal velocity component as viewed by the observer, will decrease to zero.
  • the point will then accelerate from left to right towards the midline (and maximum positive parallax).
  • the horizontal velocity component will then return to. zero as it approaches the right-hand side of the model.
  • the point will accelerate to maximum horizontal velocity (and maximum negative parallax), when it reaches the midline 44.
  • model 41 which is displaced from the center of rotation, will have a greater rotational velocity than model 40. This rotational velocity is maximized as it crosses midline 44. Because model 41 is displaced farther from the center than model 40, its horizontal velocity component as it passes the midline 44 will be greater than the velocity component of any points on the model 40. Thus, model 41 will appear to the observer to be either in front of or behind model 40, depending on the direction of the horizontal velocity component. Any objects which are placed on the turntable, in the field of the camera, will appear to assume their actual relative locations in the stereoscopic composite image. In the preferred embodiment, the most pleasing stereoscopic effects are obtained by rotating turntable 42 between 4 and 15 revolutions per minute.
  • Figure 4 also illustrates a means for generating a stereoscopic background image utilizing the Pulfrich effect.
  • the background image is made to appear to be stereoscopically behind the foreground image.
  • a means must be provided for supplying the background image with a horizontal velocity component relative to the horizontal velocity component of the foreground image in a manner to create this illusion.
  • one means for providing this effect is through the use of a rotatable disc 46, having the background images formed thereon.
  • the plane of disc 46 is parallel with the plane of the two-dimensional screen upon which the image will be projected.
  • the angle of inclination can be .adjusted to produce various stereoscopic effects.
  • the disc may be rotated about its central axis, as illustrated by arrows B.
  • the rotational speed of the images on the disc will be proportional to their distance from the rotational axis. Accordingly, in the illustrated example, the images formed on the disc, towards the outer periphery thereof, will have the highest velocity component and therefore appear to be farthest in the background behind the model 40.
  • the rotational axis of the disc 46 should be arranged relative to the field of the camera such that all the recorded images have a horizontal velocity component in the same direction.
  • the field of the camera is depicted by a rectangle 48. If the disc is rotated in a clockwise manner, all of the images within the field 48 will have a horizontal velocity component moving from left to right and a positive generated parallax.
  • FIG 5 an alternate arrangement is shown for providing stereoscopic background and foreground images which exhibit the Pulfrich effect.
  • the moving images defined by the rotatable disc in Figure 4 are replaced with means capable of generating moving images.
  • a subject 50 is photographed by a camera 52 in front of a screen 54.
  • an image of the subject 50 can be created.
  • Foreground or background images can then be generated separately.
  • Figure 5B illustrates one way of generating the moving background wherein images are formed on a scroll 56 that is moved relative to the camera.
  • the speed of movement of the scroll will affect the depth of the Pulfrich images formed thereon.
  • Moving background images can also be computer generated.
  • the image of the subject 50 in Figure 5A can then be superimposed on the images generated in Figure 5B to arrive at a composite picture illustrated in Figure 5C.
  • the composite stereoscopic image can be further enhanced if the foreground subject 50 were photographed on a turntable as illustrated in Figure 4.
  • subject 50 could be given a horizontal velocity component simply by moving the subject relative to the camera.
  • the above described techniques are equally applicable for generating stereoscopic foreground images.
  • images of fish on the scroll can be superimposed in front of subject 50.
  • the direction of the horizontal velocity component of the scroll is merely reversed.
  • a wide variety of effects can be achieved by properly controlling the relative horizontal velocity of the foreground and background images.
  • All of the above described techniques can be used in a variety of systems capable of generating stereoscopic images for projection on a two-dimensional screen such as movies and television. Another environment which is particularly suited for applying these techniques is in the field of video games.
  • a unique arrangement is provided to substantially enhance the stereoscopic effects associated with a video game, while utilizing limited display technology.
  • a television monitor 60 that includes a standard cathode ray tube screen 62 or other display device such. as a liquid crystal display.
  • the active display on the screen 62 is intended to include stereoscopic images.
  • stereoscopic images are generated utilizing the Pulfrich illusion.
  • the Pulfrich images may be computer generated or produced from live models as described earlier in conjunction with Figures 4 and 5.
  • a transparent overlay 64 is mounted on the front of the screen 62.
  • the transparent overlay 64 is provided with passive stereoscopic images.
  • Methods for forming passive stereoscopic images are known in the art and include anaglyphs and vectographs. Briefly, an anaglyph overlay is formed in two colors and can be observed stereoscopically with the use of coordinated color filters.
  • dichroic dyes are used to create a polarized stereo pair that can be printed as a single photograph transparency. A vectograph is viewed stereoscopically utilizing polarized lenses.
  • a viewing means for stereoscopically observing both the active and passive systems.
  • the exact nature of the viewing means will, of course, be dependent upon the particular active and passive stereoscopic techniques used.
  • spectacles 66 would be designed to permit the viewing of the illusion. More particularly, spectacles 66 are provided with a pair of filters wherein the left filter 68 is of a greater optical density than the right filter 70. As discussed above with regard to Figure 1, this density difference will allow the viewing of the Pulfrich illusion.
  • the spectacles 66 also include a means for simultaneously viewing the passive stereoscopic image formed on the overlay 64.
  • filters 68 and 70 can also be tinted with the appropriate colors.
  • the passive means is defined by a vectograph
  • lenses 68 and 70 will not only have a density difference but will also be polarized in opposite directions.
  • Each filter element 68 and 70 may be formed from a dual layered sheet defined by both a neutral density filter and a colored or polarizing filter. In the alternative, a composite filter of a single sheet can be used to create each lens.
  • the unique display of active and passive stereoscopic images in combination with a single composite viewing means permits relatively complex stereoscopic images to be formed using limited active display techniques.
  • the overlay may include a stereoscopic playing field through which moving objects of a video game will pass.
  • the interaction between the active images and the passive images can be designed to provide pleasing and commercially acceptable video game systems.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Testing, Inspecting, Measuring Of Stereoscopic Televisions And Televisions (AREA)
  • Stereoscopic And Panoramic Photography (AREA)

Abstract

Afin de permettre l'observation de l'effet Pulfrich dans des images projetées sur un écran bi-dimensionnel, des filtres (10, 12) sont placés devant les yeux de l'observateur. Le filtre placé devant un oeil est plus dense que le filtre placé devant l'autre oeil. Pour accroître l'impression de profondeur un bord foncé (30) peut entourer l'écran.
PCT/US1984/000626 1983-04-27 1984-04-25 Sytemes video stereoscopiques WO1984004405A1 (fr)

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Application Number Priority Date Filing Date Title
AU28631/84A AU2863184A (en) 1983-04-27 1984-04-25 Stereoscopic video systems

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Application Number Priority Date Filing Date Title
US48922883A 1983-04-27 1983-04-27

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WO1984004405A1 true WO1984004405A1 (fr) 1984-11-08

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0325019A1 (fr) * 1988-02-09 1989-07-26 BEARD, Terry D. Lunettes de vision 3D à faible différentiel et méthode

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2083313A (en) * 1934-06-25 1937-06-08 Wilton Bentley Stereoscope
US3317206A (en) * 1963-04-29 1967-05-02 James B Holt Illusory three-dimensional projection system
US3460882A (en) * 1965-10-23 1969-08-12 Ardell J Abrahamson Wide-angle single picture system for vision in depth
US4131342A (en) * 1975-08-22 1978-12-26 Dudley Leslie P Stereoscopic optical viewing system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2083313A (en) * 1934-06-25 1937-06-08 Wilton Bentley Stereoscope
US3317206A (en) * 1963-04-29 1967-05-02 James B Holt Illusory three-dimensional projection system
US3460882A (en) * 1965-10-23 1969-08-12 Ardell J Abrahamson Wide-angle single picture system for vision in depth
US4131342A (en) * 1975-08-22 1978-12-26 Dudley Leslie P Stereoscopic optical viewing system

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
"Magnitude of the Pulfrich Stereophenomenon as a Function of Target Thickness" Journal of the Optical Society of America, Vol. 50, Number 4, p.321-327, published April, 1960 Lit *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0325019A1 (fr) * 1988-02-09 1989-07-26 BEARD, Terry D. Lunettes de vision 3D à faible différentiel et méthode

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