Video recording prevention system

A projector has at least four primary color components controlled to produce a metameric effect image which is not perceptible to the human optical system and is perceptible to a video recording device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application relates to U.S. application Ser. Nos. 12/448,338 filed on Jun. 17, 2009 which published as US 2010-0026910A1; 12/448,320 filed on Jun. 17, 2009 which published as US 2010-0014008A1; 12/312,998 filed on Jun. 3, 2009 which published as US 2010-0315596A1; 12/448,002 filed on Jun. 3, 2009 which published as US 2010-0026959A1; and 12/450,683 filed on Oct. 6, 2009 which published as US20110013143A1.

FIELD OF THE INVENTION

This application claims the benefit, under 35 U.S.C. §365 of International Application PCT/US2008/002,145, filed 25 Apr. 2007, which was published in accordance with PCT Article 21(2) on 31 Dec. 2008, in English, which claims the benefit of European patent application No. 07301147.0 filed 25 Jun. 2007.

The invention relates to a video recording prevention system. In particular, the invention relates to a metamerism based video recording prevention projector where metamer is defined as one of at least two different spectral combinations which result in the same perceived color.

BACKGROUND OF THE INVENTION

The advent of highly portable camcorders has enabled moviegoers to wrongfully and surreptitiously capture the video content of movies displayed in theaters. In an effort to combat such activities, some theaters have incorporated systems for preventing recording of movie content or degrading video captured by camcorders. The approaches have varied, but each has attempted to exploit the differences between the optical technology of camcorders and the human optical system. For example, some theaters have employed the use of ultraviolet or infrared light, both of which are invisible to the human optical system but detectable and recordable by typical camcorders. Unfortunately, the use of ultraviolet and/or infrared light to prevent or degrade recording video recording may be easily nullified when a moviegoer incorporates an appropriate spectral filter with his camcorder. Another attempt at preventing video recording is the use of frequency modulation which may deliver, for example, a copyright infringement warning detectable and recordable by typical camcorders as part of video degradation. Unfortunately, the frequency modulation method may introduce a flicker visible to the human optical system which results in an unpleasant viewing experience for the audience.

Where both a theater projection system and a camcorder operate based on the RGB color space, information of the pixel input ([RlGlBl]) to the RGB based projector which is processed by the projector mechanism (MP) may be shown as accurately transferable to the pixel output ([ROGOBO]) of the RGB based camcorder which is processed by the camcorder mechanism (MC). Accordingly, another attempt to prevent unauthorized video recording of movie content was made by introducing an extra primary color (which can involve the use of a second projector) so that different projected spectral combinations can be metamers and can be incompatible with typical camcorders. (In simplest terms, a “metamer” is a color that is different than another color, but yet appears to be the same color as the other to an observer and “metamerism” is the use of metamers such that two or more different colors (i.e. metamers) are perceived as the same color to the observer.) This technique takes advantage of the differing spectral sensitivity curves of the RGB camcorder and the typical human optical system. The addition of the fourth primary color allows the projectionist to display a movie with a spectral combination of four primary colors which are perceived by the moviegoer generally as originally intended by the movie producer because of the nature of metamerism (i.e. there is a plurality of spectral power distributions that will be perceived by the human eye as the same color, but will “result in different values in a video camera” as described in WO 2004/0408989 A2). The use of a second projector may result in synchronization problems with the primary projector. Further, the introduction of only a single extra primary color results in only one-dimensional metamerism which could be the easiest form of metamerism to circumvent through linear, single, or conventional equation solutions.

It is therefore desirable to develop an improved video recording prevention system.

SUMMARY OF THE INVENTION

The present invention is directed to a projector having at least four primary color components controlled to produce an image that a human eye and a camcorder perceive very differently.

DETAILED DESCRIPTION OF THE INVENTION

Referring now toFIG. 1Ain the drawings, a projector according to the present invention is illustrated. Projector100can comprise a light source101having a reflector103, a directional light transmission device105, an optional filter drum107(which is shown in greater detail inFIG. 1B), relay optics109, a six primary color prism111, and imager devices104,106,108,110,112,114, which are variously referred to as digital micromirror devices, micromirror devices, micromirror array devices, or microdisplay devices. The color division of the six primary color prism111can be accomplished by introducing dichroics113(which are also referred to as dichroic prisms or color splitters) and additional beam splitting components117which further split the different color light components, as shown inFIG. 1A. Each primary is then delivered to a corresponding micromirror device. The use of six primaries provides a wider color gamut and greater color control at a given refresh or frame rate. In an example arrangement, a cyan, blue, yellow, green, red, and orange color components are directed toward and reflected from respective micromirror devices. Particularly, micromirror device104reflects a red color component of light beam102, micromirror device106reflects a green color component of light beam102, micromirror device108reflects a blue color component of light beam102, micromirror device110reflects a yellow color component of light beam102, micromirror device112reflects an orange color component of light beam102, and micromirror device114reflects a cyan color component of light beam102. In operation, light source101emits a light beam102into directional light transmission device105which then directs the light through a filter drum107, which can have optional polarization optics for potential three dimensional (3D) capability. The light beam102then travels through relay optics109which direct the light beam102into prism111.FIG. 1Aalso shows the use of mirror118which can be use with the relay optics to steer the light beam into the prism111. As described above, the color components of light beam102are then subsequently directed out of prism111by micromirrors104,106,108,110,112, and114and eventually onto a display surface (not shown).

Referring now toFIG. 1Bin the drawings, a filter device or drum107(also referred to as a polarization hollow cylinder) is illustrated. The filter device or drum107can be a rotatable drum-like structure formed of translucent materials. Although the filter device can have other geometries such as a planar wheel structure, a drum structure is presently preferred and as such, the expression “drum” will be consistently used in the following description. Drum107is shown as a flat band of material located in close proximity to a directional light transmission device (or light pipe)105for passing light through drum107by directing light generally orthogonal to an interior surface154of the drum107such that light passes through the translucent material and exits the drum107through an exterior surface156of the drum107, i.e. through a wall of the drum. As shown, the drum is divided into radially alternating P-polarization sections158and S-polarization sections160. Alternatively, for example, the drum107can be divided into radially alternating clockwise and counter-clockwise polarization sections. In operation, a two dimensional (2D) image can be converted to a 3D image by transmitting the 2D image through the directional light transmission device105and subsequently through the polarization drum107while drum107is rotated about its central axis. The drum107is rotated at a controlled speed so as to appropriately polarize each frame of images as either P-polarization or S-polarization by passing the image through sections158,160, respectively. The 3D image is perceived by a viewer of the projected image when the viewer wears polarized filter glasses (not shown) which allow only one of the P and S polarized portions of light through the glasses to each eye of the viewer. The projector should present approximately twice the number of frames per second in 3D mode as opposed to a normal 2D mode since each eye will only see every other frame. Different embodiments of the invention include all combinations of features disclosed which also have the filter device or drum107.

Referring now toFIG. 2, projector100can be incorporated into a theater projection system so that the six primary colors are used in combination to provide a projected image as shown.FIG. 2illustrates an image200comprising a humanFIG. 202standing next to a tree204.FIG. 2represents the projected image as the image would be perceived by a moviegoer with a typical human optical system, for example, with typical eyesight and no colorblindness. It will be appreciated thatFIG. 2is perceived by the moviegoer in substantially the form intended by the producer of the movie or image being projected.

Referring now toFIG. 3, the same light being emitted from prism100and used to create the image200as perceived by a moviegoer as illustrated inFIG. 2will be captured by a video recording device in a substantially degraded manner. It should be noted that the use of the expression “video recording device” is intended to include any type of color video recording devices such as portable camcorders. Specifically,FIG. 3illustrates an image300which comprises not only the humanFIG. 202standing next to a tree204but also the presence of substantially diagonal stripes302integrated into the image300. This duality of differing perceptions of different images from the same source, between the human moviegoer and the video recording device, is referred to as a metamerism effect and is related to the differing spectral sensitivity curves of those systems. In other words, the colors of some of the regions in the background inFIG. 3appear to have the same color to the human; however, the different regions are intentionally composed of different spectral power distributions, such that the video recording device will not see these regions as metamers. In other words, the video recording device will see different colors as shown inFIG. 3.

When preparing a movie for use with a projector having a prism100, the metamerism effects (such as diagonal stripes302) perceived by video recording devices but not moviegoers can be produced by controlling the digital micromirror devices104,106,108,110,112, and114so that any number of different images or varieties of degradation may be provided.

Referring now toFIG. 4in the drawings, it is shown that an image projected by a projector having a prism100may cause a moviegoer to see an image substantially similar to image200while a video recording device captures a different image. Specifically, the metamerism effect may be used to cause a video recording device to capture an image400comprising legible messages in the form of text402and/or graphics404. In image400, the text402is “FBI WARNING” and the graphic404is a copyright symbol. These types of degradations serve not only to lessen the quality of the captured image with respect to the way the producer of the movie intended for the movie to be viewed by a moviegoer, but are also capable of explicitly warning against illegal copying of the captured video. However, it will be appreciated that in alternative embodiments of the present invention, the metamerism effect can be utilized to produce an image captured by a video recording device that merely comprises unpleasant or different coloring from the image to be viewed by moviegoers.

Since the prism100of the present invention is incorporated into a single projector, there is no problem with aligning, synchronizing, or otherwise simultaneously operating two projectors to produce a single image. Operation of one projector rather than two or more projectors equates to less work for a projectionist and higher reliability in producing a high quality image. Further, it will be appreciated that whileFIGS. 1-4describe metamerism effects generated using a six primary color prism100in a single projector, the present invention more generally includes the use of four or more primary colors in a single projector. However, when a four primary color projector is compared to a six primary color projector having a six primary color prism100, it will be appreciated that the six primary color projector provides a wider color gamut. Further, the six primary color projector also offers an unlimited number of color combinations for providing relatively secure metamerism effects that are not easily circumvented by those who capture only the red, green, and blue components. More specifically, removing the metamerism effects from the captured image would require complex multi-dimensional equation analysis. In short, the use of the six primary color projector in combination with metamerism results in a low likelihood of success in illegal recording. Finally, while the present invention has been described with respect to using digital micromirror devices, the present invention applies equally to and may be incorporated with other technologies such as LCD, SXRD, D-ILA, and LCoS, regardless of the response times of the projection technologies.

Further, another aspect of the invention is to generate a look-up table from psychovisual experiments. The look-up table (which can be part of the projector) includes a substantial number of metamers from different spectral power distributions for some selected colors to be perceived by a human, by design. Having and using more than two metamers for some intended perceived colors will ensure that a video recording device will differently perceive the different spectral power distributions associated with the intended color to be perceived by the human eye. The projector can further have a processor that employs more than two different spectral power distributions. By using more than two metamers, it increases the chances that all video recording devices will be able to distinguish at least one pair of metamers.

The foregoing illustrates only some of the possibilities for practicing the invention. Many other embodiments are possible within the scope and spirit of the invention. For example, other devices or components which can serve as the functional equivalent of dichroics or color splitters in combination with other components of the projector are considered embodiments of the invention. Also, for example, the use of five primaries such as cyan, blue, yellow, green, and red color components is an embodiment of the invention. It is, therefore, intended that the foregoing description be regarded as illustrative rather than limiting, and that the scope of the invention is given by the appended claims together with their full range of equivalents.