(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (19) World Intellectual Property Organization International Bureau (10) International Publication Number (43) International Publication Date WO 2013/158322 Al 24 October 2013 (24.10.2013) P O P C T (51) International Patent Classification: (74) Agent: STEIN, Michael, D.; Woodcock Washburn LLP, G06T 15/08 (201 1.01) Cira Centre, 2929 Arch Street, 12th Floor, Philadelphia, PA 19104-2891 (US). (21) International Application Number: PCT/US20 13/032821 (81) Designated States (unless otherwise indicated, for every kind of national protection available): AE, AG, AL, AM, (22) Date: International Filing AO, AT, AU, AZ, BA, BB, BG, BH, BN, BR, BW, BY, 18 March 2013 (18.03.2013) BZ, CA, CH, CL, CN, CO, CR, CU, CZ, DE, DK, DM, (25) Filing Language: English DO, DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, GT, HN, HR, HU, ID, IL, IN, IS, JP, KE, KG, KM, KN, KP, (26) Publication Language: English KR, KZ, LA, LC, LK, LR, LS, LT, LU, LY, MA, MD, (30) Priority Data: ME, MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI, 61/635,075 18 April 2012 (18.04.2012) US NO, NZ, OM, PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SC, SD, SE, SG, SK, SL, SM, ST, SV, SY, TH, TJ, (71) Applicant: THE REGENTS OF THE UNIVERSITY TM, TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, OF CALIFORNIA [US/US]; 1111 Franklin Street, ZM, ZW. Twelfth Floor, Oakland, CA 94607 (US). (84) Designated States (unless otherwise indicated, for every (72) Inventors: DAVIS, James E.; 1156 High Street: SOE3, kind of regional protection available): ARIPO (BW, GH, Santa Cruz, CA 95064 (US). SCHER, Steven; 543 Beacon GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, SZ, TZ, Place, Chula Vista, CA 91910 (US). LIU, Jing; 1200 Dale UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU, TJ, Avenue, Apartment 87, Mountain View, CA 94040 (US). TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK, VAISH, Rajan; 1200 Dale Avenue, Apartment 87, Moun EE, ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV, tain View, CA 94040 (US). GUNAWARDANE, Prabath; MC, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK, SM, 216 Mountain View, Apartment 3, Mountain View, CA TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ, GW, 9404 1 (US). ML, MR, NE, SN, TD, TG). [Continued on nextpage] (54) Title: SIMULTANEOUS 2D AND 3D IMAGES ON A DISPLAY (57) Abstract: Many 3D displays show 3D images to view ers wearing special eyeglasses, while showing a double im age to viewers without eyeglasses (13e). We demonstrate a method (15a-15h) that provides those with eyeglasses a 3D experience while viewers without eyeglasses see a 2D image without artifacts (Fig. 1, image lb). In addition to separate Left ("L") and Right ("R") images in each frame, we add a X third image ("N"), invisible to those with glasses. In the com bined view seen by those without glasses, this cancels the Right image, leaving only the Left. If the Left and Right im ages are of equal brightness, this approach results in low contrast to viewers without glasses. Allowing differential brightness between the Left and Right images improves 2D contrast. We determine that viewers with glasses maintain a strong 3D experience, even when one eye is significantly darker than the other. FIG. 15 w o 2013/158322 Al 111 111 II II I Hill 1 I ll l l III I II III II I II Published: SIMULTANEOUS 2D AND 3D IMAGES ON A DISPLAY CROSS REFERENCE [0001] This application claims the benefit of U.S. Provisional Application No. 61/635075, filed on April 18, 2012, the content of which is hereby incorporated by reference in its entirety. TECHNICAL FIELD [0002] The disclosed subject matter relates generally to three-dimensional television (3DTV) technology, and more particularly to a method and system that provide viewers with 3D glasses a 3D experience while viewers without glasses see a 2D image without artifacts such as ghosting. Our approach is applicable to displays using either active-shutter glasses or passive glasses. BACKGROUND [0003] With a 3DTV, depth perception is conveyed to the viewer by employing techniques such as stereoscopic display, multi-view display, 2D-plus-depth, or any other form of 3D display. Most modern 3D television sets use an active shutter 3D system or a polarized 3D system and some are autostereoscopic without the need of glasses. [0004] There are several techniques to produce and display 3D moving pictures. A basic requirement for display technologies is to display offset images that are filtered separately to the left and right eye. Two approached have been used to accomplish this: (1) have the viewer wear 3D eyeglasses to filter the separately offset images to each eye, or (2) have the light source split the images directionally into the viewer's eyes, with no 3D glasses required. [0005] As explained in the detailed description below, many 3D displays show 3D images to viewers wearing the special 3D eyeglasses, but show an incomprehensible double image (called "ghosting") to viewers without glasses. A goal of the present invention is to devise a method and system for providing viewers with glasses a 3D experience while also providing viewers without glasses a 2D image without artifacts. SUMMARY [0006] Many 3D displays show 3D images to viewers wearing special eyeglasses, while showing an incomprehensible double image to viewers without glasses. We demonstrate a method that provides those with eyeglasses a 3D experience while viewers without glasses see a 2D image without artifacts. In addition to separate Left and Right images in each frame, we add a third image, invisible to those with glasses. In the combined view seen by those without glasses, this cancels the Right image, leaving only the Left. If the Left and Right images are of equal brightness, this approach results in low contrast to viewers without glasses. Allowing differential brightness between the Left and Right images improves 2D contrast. We determine that viewers with glasses maintain a strong 3D experience, even when one eye is significantly darker than the other. Since viewers with glasses see a darker image in one eye, they experience a small distortion of perceived depths due to the Pulfrich Effect. This produces illusions similar to those caused by a time delay in one eye. We find that a 40% brightness difference cancels an opposing distortion caused by the typical 8 millisecond delay between the Left and Right images of sequential active-shutter stereoscopic displays. Our technique is applicable to displays using either active-shutter glasses or passive glasses. [0007] Other aspects of the inventive method and system are described below. BRIEF DESCRIPTION OF THE DRAWINGS [0008] Figure 1, part (a), depicts how a typical glasses-based 3DTV shows a different image to each eye of viewers wearing stereo glasses. Part (b) depicts how an inventive 3D+ 2DTV shows a different image to each eye of viewers wearing stereo glasses, but shows only one of these images to those without glasses, removing the "ghosted" double- image. Part (c) illustrates that this is accomplished by cancelling out one image of the stereo pair. [0009] Figure 2 depicts a comparison of various displays that show a sequence of frames. [0010] Figure 3 illustrates how different amounts of wasted light result from different frame lengths for the L, R and inverse R frames. [0011] Figure 4 is a graph showing how max2D, the brightness of the composite image seen by viewers not wearing stereo glasses, improves when aR, the brightness of the image shown to the right eye of 3D viewers, is decreased. [0012] Figure 5 depicts two versions of an image: (left) the ghosted double-image that would be seen on a typical 3D display if the viewer did not wear stereo glasses, and (right) the lower-contrast image without ghosting that the viewer would see on a display in accordance with the present invention. [0013] Figure 6 is a graph of viewer preference data. [0014] Figure 7 depicts images used in an experiment to quantify viewers' ability to perceive depth in static images on a stereoscopic display when one eye is presented with a darker image than the other eye. [0015] Figure 8 is a graph of the results of the experiment of Figure 7, showing that as one eye's brightness decreases, viewers' ability to perceive depth is not affected until the brightness of the darker eye is below 20% of the brightness of the brighter eye. [0016] Figure 9 depicts images used in an experiment to measure viewers' ability to perceive depth when the images shown to one eye are darker than those shown to the other eye. [0017] Figure 10 is a graph of data from the experiment of Figure 9, showing that viewers' ability to perceive depth differences was undisturbed by one eye seeing a darker image than the other provided the dark image was at least 10% as bright as the brighter eye. [0018] Figure 11 depicts images used in an experiment to quantify the impact of the Pulfrich Effect on depth perception. [0019] Figure 12 is made up of two graphs of data showing that, when one eye is brighter than the other, the depth of moving objects is misperceived. [0020] Figure 13 depicts a prototype of the inventive system including two projectors and a polarization preserving screen. [0021] Figure 14 depicts several example images of the inventive prototype in use.