The patent's assignee is Sol-grid, Llc.
News editors obtained the following quote from the background information supplied by the inventors: "Stereoscopic projection is a growing area of particular interest for the entertainment industry. Presentation of three-dimensional (3D) images or perceived stereoscopic content affords the viewer an enhanced visual experience, in the home theater setting or in larger venues such as movie theaters. Stereoscopic systems have been implemented using film, in which two sets of films and projectors simultaneously project orthogonal polarizations, one for each eye, termed a 'left-eye image' and a 'right-eye image' in the present disclosure. With digital projection and display, more options for image presentation are available, so that even a single projector or display device can be used to provide separate left- and right-eye imaging paths. Audience members wear corresponding orthogonally polarized glasses that block one polarized light image for each eye while transmitting the orthogonal polarized light image.
"Polarized light can be represented as the sum of two orthogonal linear components. FIGS. 1A and 1B show how the phase relationship of these components affects light polarization for linear and circular polarization for light of wavelength .lamda., respectively. A phase delay .phi.=0 between x- and y-components, represented as vectors E.sub.x and E.sub.y, respectively, yields a resultant electric field vector E.sub.sum that oscillates about a line oriented at 45.degree., providing a linear polarization 200 as shown in FIG. 1A. If the phase delay .phi.=+/-.pi./2, then E.sub.sum maintains constant magnitude but rotates about the origin, providing a circular polarization 210, as shown in FIG. 1B. A phase delay .phi.=+.pi./2 provides right circular polarization; a phase delay .phi.=-.pi./2 provides left circular polarization, orthogonal to the right circular polarization at each instant. An arbitrary phase delay (for example, .phi.=0.352.pi.) yields a vector E.sub.sum with varying magnitude and position, resulting in elliptical polarization.
"Linear polarization was used for left- and right-eye image separation in some early 3D imaging systems. However, the use of linearly polarized light is generally disadvantageous for this purpose, since the viewer's head must remain at the same angle to avoid cross-talk, a condition in which some portion of light intended for the left-eye image goes to the right eye and light intended for the right-eye image goes to the left eye. To avoid this problem, most stereoscopic imaging apparatus that employ polarization to separate left- and right-eye image content use circular, rather than linear, polarization. With circular polarization, cross-talk can be significantly reduced, since there is no fixed polarization axis relative to the display surface. As shown from the viewer's perspective in FIG. 2, for a pair of viewing glasses 220, the circular polarization for the left-eye image, light directed through a lens L1, provides rotation in the opposite direction to the circular polarization for the right-eye image, directed through a lens R1.
"A circular polarizer can be formed by combining a linear polarizer with a retarder, such as a quarter wave plate (QWP). As shown in FIG. 3, a QWP, when its axis, or polarization azimuth, has the proper orientation with respect to the polarization axis of the polarizer, provides the needed .pi./2 phase delay of one component of the periodic light signal that transforms linearly polarized light 200 to circularly polarized light 210. To transform linearly polarized light 200 to right circular polarized light 210, the QWP transmission axis is 45 degrees in one direction from the polarized light axis. To transform linearly polarized light 200 to left circular polarized light 210, the QWP transmission axis is 45 degrees in the opposite direction from the polarized light axis.
"The polarizers that are most widely available are of the linear type that employ a type of form birefringence at the molecular level. Conventional polarizing material is formed of a thin sheet of polymer material (typically polyvinyl acetate, PVA) impregnated with iodine molecules. The sheet is stretched to align the iodine molecules in order to form a polarizing structure at the molecular level. Treatment with various dyes and lamination then form the stretched sheet into a single-axis polarizer. This type of polarizer has its polarization axis determined according to the direction in which it has been stretched. Due to their inherent tint, imperfections in fabrication, and other factors, polarizers of this type, although they may serve well in sunglasses and other optical devices, are generally not well suited for use in 3D imaging glasses. One problem in fabrication of this type of polarizer is in controlling the orientation of the polarization axis, when the polarized material is curved to form eyeglasses.
"FIG. 4A shows the conventional practice where polarizing glasses have a preferred polarization axis A1 that is generally horizontal. Thus, conventional 3D glasses have the QWP retardation axis A2 and A3, where A2 is at +45 degrees from the polarization axis A1 for one eye and axis A3 at -45 degrees from the polarization axis A1 for the other eye. (This assumes that right circular polarization goes to the right eye and left circular polarization to the left eye; the opposite arrangement of QWP axis would apply for the opposite polarization sense.) An alternate arrangement, as shown in FIG. 4B, is to orient the QWP retardation axis A2 along the horizontal and to orient polarization axes A5 and A6 at +/-45 degrees accordingly for each eye.
"These fabrication restrictions for polarization axes and conventional practices for QWP axis alignment complicate the manufacture of 3D polarization glasses and drive up the cost. Given the inherent difficulties and added steps that would be required for determining the polarization axis of the stretched materials that are conventionally used and changing axes appropriately for each pair of viewing glasses, there may be few options for mass-produced 3D viewing eyewear using conventional fabrication methods.
"With the growing popularity of stereoscopic or 3D imaging, there is growing interest in apparatus and methods that provide improved circular polarizers that reduce cross-talk, provide high light levels, and can be produced at low cost."
As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "It is an object of the present invention to address the need for viewing glasses for stereoscopic imaging applications. With this object in mind, the present invention provides an article of eyewear for viewing a 3D display having at least one lens, wherein the at least one lens comprises: a substrate lens material that is transparent to visible light and has a curved surface; and a circular polarizer formed on the substrate lens material, wherein the circular polarizer comprises: (i) a linear polarizer having a polarization axis; and (ii) a quarter wave plate having a retardation axis that is inclined at substantially 45 degrees from the polarization axis along the curved surface, wherein either or both of the linear polarizer and the quarter wave plate are formed as sub-wavelength elongated structure devices.
"It is a feature of the present invention that it uses a linear polarizer with added spatial polarization azimuth control to provide viewing glasses that allow improved differentiation of left- and right-eye imaging for stereoscopic viewing. Advantageously, embodiments of the present invention improve existing fabrication processes and provide viewing glasses that allow increased amounts of light and reduced cross-talk over existing solutions.
"These and other objects, features, and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there is shown and described an illustrative embodiment of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
"FIG. 1A is a schematic diagram that shows the phase relationship for linearly polarized light.
"FIG. 1B is a schematic diagram that shows the phase relationship for circularly polarized light.
"FIG. 2 is a schematic diagram that shows polarization properties of 3D viewing glasses that use circular polarization to separate left- and right-eye images.
"FIG. 3 is a schematic diagram that shows the function of a quarter wave plate for transforming linearly polarized to circularly polarized light.
"FIG. 4A is a schematic diagram showing conventional 3D viewing glasses with one orientation of polarization to retardation axes.
"FIG. 4B is a schematic diagram showing conventional 3D viewing glasses with an alternate orientation of polarization to retardation axes.
"FIG. 5A is a schematic diagram showing the parts of a pair of 3D viewing glasses.
"FIG. 5B is a schematic diagram that shows the light path through the parts of the 3D viewing glasses shown in FIG. 5A.
"FIG. 6 is a schematic diagram that shows basic principles of wire grid polarizer operation.
"FIG. 7A is a schematic diagram that shows 3D viewing glasses with a consistent polarization axis.
"FIG. 7B is a schematic diagram that shows 3D viewing glasses with a variable polarization axis, varying over different regions of the lens.
"FIG. 8A is a diagram showing distortion of polarization and retardation axes.
"FIG. 8B is a process diagram that shows how a circular polarizer can be formed from linear polarizer and quarter wave plate components.
"FIG. 8C is a perspective diagram that shows a quarter wave plate formed using sub-wavelength elongated structures.
"FIG. 9 is a perspective diagram showing cholesteric polarizer behavior.
"FIG. 10 is a cross-sectional diagram showing a circular polarizer on a non-corrected substrate surface.
"FIG. 11 is a cross-sectional diagram showing a circular polarizer on a corrected substrate surface.
"FIG. 12 is a cross-sectional diagram showing a circular polarizer on a corrected substrate surface.
"FIG. 13 is a cross-sectional diagram showing a circular polarizer with quarter wave plate and linear polarizer components formed on opposite surfaces of the substrate."
For additional information on this patent application, see: Kessler, David;
Keywords for this news article include: Sol-grid Llc.
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