Samsung Patent | Directional Backlight Unit, Three-Dimensional (3d) Image Display Apparatus, and 3d Image Displaying Method

Patent: Directional Backlight Unit, Three-Dimensional (3d) Image Display Apparatus, and 3d Image Displaying Method

Publication Number: 20190033609

Publication Date: 2019-01-31

Applicants: Samsung

Abstract

A directional backlight unit, a three-dimensional (3D) image display apparatus, and a 3D image displaying method are provided. The directional backlight unit includes a light guide plate having an emission surface on which a plurality of grating elements including first and second groups of grating elements are provided. The plurality of grating elements are arranged such that light beams emitted from the first and second groups of grating elements commonly propagate through a plurality of pixel points and respectively form first and second groups of view points of which corresponding regions do not overlap with each other.

Background

Three-dimensional (3D) image display apparatuses enable users to experience realistic and stereoscopic images. In general, 3D image display apparatuses provide a 3D effect by using a binocular parallax that appears when images at different view points are seen by the left and right eyes. In the conventional art, glasses-type 3D image displaying methods using red-green glasses, polarizing glasses, liquid crystal shutter type glasses, or the like were primarily developed. In recent years, autostereoscopic 3D image displaying methods removing the inconvenience of using glasses have been actively studied. Examples of autostereoscopic 3D image displaying methods include a method of displaying several images having different view points according to directions by using a lenticular lens, a parallax barrier, or the like; integrated image technology, which is a method of capturing images at several angles by using a plurality of cameras or lenses and displaying the images inversely; and a holography method. Among these autostereoscopic 3D image realizing technologies, a technology related with a method of constructing a 3D image by respectively transmitting light beams from pixels in desired directions by using a recent directional backlight unit is being developed.

Description

Provided are directional backlight units that provide a wide watching angle, three-dimensional (3D) image display apparatuses, and 3D image displaying methods.

Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented exemplary embodiments.

According to an aspect of one or more exemplary embodiments, a directional backlight unit includes a light guide plate; a light source configured to provide light to the light guide plate; and first and second groups of grating elements disposed on an emission surface of the light guide plate and configured to externally emit the light from the emission surface, wherein the first and second groups of grating elements are arranged such that light beams emitted from the first group of grating elements propagate through a plurality of pixel points spaced apart from the emission surface and form a first group of view points, that light beams emitted from the second group of grating elements propagate through the plurality of pixel points and form a second group of view points, and that a region within which the second group of view points are formed does not overlap with a region within which the first group of view points are formed. The plurality of pixel points indicate points where pixels of a spatial light modulator which will be described below are located. The plurality of pixel points may be two-dimensionally arranged on a plane or a curved surface.

The view points in the first group may be consecutively arranged, and the view points in second group may be consecutively arranged after the first group of view points.

A third group of grating elements may be further disposed on the light guide plate. In this case, the third group of grating elements is arranged such that light beams emitted from the third group of grating elements propagate through the plurality of pixel points and form a third group of view points and that a region within which the third group of view points is formed does not overlap with a region within which the first and second groups of view points are formed. For example, the view points in the third group of view points may be consecutively arranged after the second group of view points.

At least two light beams may propagate through each of the plurality of pixel points, and the at least two light beams may include a light beam emitted from one of the grating elements included in the first group and a light beam emitted from one of the grating elements included in the second group.

According to an exemplary embodiment, light beams emitted from two adjacent grating elements among the first and second groups of grating elements may be directed to different pixel points. According to another exemplary embodiment, some of the light beams emitted from two adjacent grating elements among the first and second groups of grating elements may be directed to the same pixel point.

The first and second groups of grating elements may include a plurality of patterned grooves that are substantially parallel to one another. The first and second groups of grating elements may be different from each other with respect to at least one of a grating length, a grating width, a grating depth, a grating orientation, a grating pitch, and a duty cycle. For example, the grating elements may have different grating orientations or different grating pitches so that light beams emitted from the grating elements may have different directions.

At least some of the first and second groups of grating elements may be different from each other in an arrangement interval.

Intervals between the first and second groups of grating elements and the plurality of pixel points may be substantially constant. A virtual pixel surface on which the pixel points are located, or the emission surface of the light guide plate may be a curved surface. If the virtual pixel surface on which the pixel points are located is a plane, the emission surface of the light guide plate is also a plane, and the virtual pixel surface on which the pixel points are located may be parallel to the emission surface of the light guide plate.

The number of grating elements in the first group may be substantially the same as the number of pixel points. In other words, the grating elements in the first group may match with the pixel points in a one-to-one correspondence.

The number of grating elements in the first group may be substantially the same as the number of grating elements in the second group. In this case, the number of view points in the second group formed by the second group of grating elements may be equal to the number of view points in the first group formed by the first group of grating elements. In some cases, the number of grating elements in the second group may be less than or more than the number of grating elements in the first group. When the number of grating elements in the second group is less than the number of grating elements in the first group, a resolution at the second group of view points formed by the second group of grating elements may be lower than a resolution at the first group of view points formed by the first group of grating elements.

The light guide plate may include a single light guide plate. In this case, the first and second groups of grating elements may form a single grating array on the emission surface of the light guide plate. The light guide plate may be a flat panel having a flat emission surface or a plate having a curved emission surface. The emission surface of the light guide plate and the surface on which the plurality of pixel points are located may be apart by a predetermined distance from each other. As another example, one of the emission surface of the light guide plate and the surface on which the plurality of pixel points are located may be a curved surface, and the other may be a plane, and thus an interval between the light guide plate and the spatial light modulator may be variable.

The light guide plate may include a first light guide plate and a second light guide plate that are optically separated from each other, some of the grating elements in the first and second groups may be disposed on the first light guide plate, and the others may be disposed on the second light guide plate.

The number of grating elements provided on each of the first and second light guide plates may be substantially the same as the number of pixel points. In some cases, the number of grating elements provided on the first light guide plate may be less than or more than the number of grating elements provided on the second light guide plate. The first group of grating elements may be provided on the first light guide plate and the second group of grating elements may be provided on the second light guide plate.

The first and second light guide plates may be disposed side by side in a lateral direction. The lateral direction denotes a direction toward a left side, a right side, a top side, or a bottom side of a plate. In other words, the first and second light guide plates may be arranged two-dimensionally. The first and second light guide plates may be flat panels having flat emission surfaces or curved emission surfaces. The second light guide plate may be inclined with respect to the first light guide plate. Of course, the first and second light guide plates may be arranged on a plane.

A third light guide plate may be further included, and thus the second and third light guide plates may be stacked one on another or arranged side by side, with the first light guide plate therebetween. The second and third light guide plates may be inclined with respect to the first light guide plate so that the second and third light guide plates are symmetrical about the first light guide plate. Of course, the first through third light guide plates may be arranged on a plane.

The first light guide plate may be stacked over an upper surface of the second light guide plate. The upper surface of the second light guide plate may denote an emission surface of the second light guide plate. The first and second light guide plates may be stacked without spaces therebetween or with a slight space therebetween. Since the third light guide plate is further included, the first through third light guide plates may be stacked one on another.

According to an aspect of one or more exemplary embodiments, a directional backlight unit includes a light guide plate; a light source configured to provide light to the light guide plate; and k groups of grating elements disposed on an emission surface of the light guide plate and configured to externally emit the light from the emission surface, wherein the k groups of grating elements are arranged such that light beams emitted from an l-th group of grating elements pass through a plurality of pixel points spaced apart from the emission surface and form an l-th group of view points, that light beams emitted from an m-th group of grating elements pass through the plurality of pixel points and form an m-th group of view points, and that a region where the m-th group of view points is formed does not overlap with a region where the first group of view points is formed, and wherein k may be a natural number, l may be a natural number smaller than or equal to k, and m may be a natural number smaller than l.

According to an aspect of one or more exemplary embodiments, a directional backlight unit includes a light guide plate; a light source configured to provide light to the light guide plate; and a plurality of grating elements disposed on an emission surface of the light guide plate and configured to externally emit the light from the emission surface such that the light propagates through a plurality of pixel points spaced apart from the emission surface, wherein at least two of the plurality of grating elements match with each pixel point, two adjacent grating elements match with different pixel points, and light beams emitted from the at least two grating elements pass through one pixel point matched with the at least two grating elements and then are directed toward different view points. The overall number of grating elements may be an integer multiple of the number of pixel points. The plurality of grating elements may be arranged such that light beams emitted from the plurality of grating elements pass through the plurality of pixel points and form a plurality of groups of view points and that regions where different groups of view points are formed do not overlap with each other.

According to an aspect of one or more exemplary embodiments, a three-dimensional (3D) image display apparatus includes a directional backlight unit comprising a light guide plate, a light source configured to provide light to the light guide plate, and first and second groups of grating elements disposed on an emission surface of the light guide plate and configured to externally emit the light from the emission surface; a spatial light modulator comprising a plurality of pixels that modulate light beams emitted from the directional backlight unit; and a controller configured to control the directional backlight unit and the spatial light modulator, wherein the first and second groups of grating elements are arranged such that light beams emitted from the first group of grating elements pass through the plurality of pixels of the spatial light modulator and form a first group of view points, that light beams emitted from the second group of grating elements pass through the plurality of pixels of the spatial light modulator and form a second group of view points, and that a region where the second group of view points are formed does not overlap with a region where the first group of view points are formed. The spatial light modulator may include a plurality of pixels that are two-dimensionally arranged. The spatial light modulator may be a flat panel or a curved plate. In other words, the pixels of the spatial light modulator may be located on a flat panel or a curved plate.

The view points in the first group may be consecutively arranged, and the view points in second group may be consecutively arranged after the first group of view points.

At least two light beams may pass through each of the plurality of pixel points, and the at least two light beams may include a light beam emitted from one of the grating elements included in the first group and a light beam emitted from one of the grating elements included in the second group.

3D images shown at the first group of view points may be repeatedly shown at the second group of view points.

The spatial light modulator may include a plurality of sub-pixels for each pixel, and each of the sub-pixels of the spatial light modulator may transmit light beams emitted from at least two grating elements.

Each of the sub-pixels may have a rectangular shape that is longer in one direction or a shape similar to the rectangular shape. The plurality of sub-pixels in each pixel may be arranged side by side in a width direction thereof. In a lengthwise direction of the sub-pixels, the overall number of rows of the first and second groups of grating elements may be an integer multiple of the number of rows of the sub-pixels.

The 3D image display apparatus may further include an eye tracking device configured to track eyes of a viewer. The controller may control the spatial light modulator so that pixels corresponding to the eyes of the viewer tracked by the eye tracking device generate an image. If the viewer moves from the first group of view points to the second group of view points or moves from the second group of view points to the first group of view points, a reversal between the left and right sides occurs, and a stereoscopic effect may be destroyed. Occurrence of the reversal between the left and right sides may be prevented by moving the view points in advance.

According to an aspect of one or more exemplary embodiments, a three-dimensional (3D) image display apparatus includes a directional backlight unit; a spatial light modulator including a plurality of pixels that modulate light beams emitted from the directional backlight unit; and a controller configured to control the directional backlight unit and the spatial light modulator. The directional backlight unit may include a light guide plate, a light source configured to provide light to the light guide plate, and a plurality of grating elements disposed on an emission surface of the light guide plate and configured to externally emit the light from the emission surface such that the light propagates through the plurality of pixels of the spatial light modulator. At least two of the plurality of grating elements match with each pixel, two adjacent grating elements match with different pixels, and light beams emitted from the at least two grating elements pass through one pixel matched with the at least two grating elements and then are directed toward different view points.

According to an aspect of one or more exemplary embodiments, a 3D image displaying method includes providing light to a light guide plate; arranging a plurality of grating elements comprising first and second groups of grating elements on an emission surface of the light guide plate to externally emit the light from the emission surface; modulating emitted light beams by using a plurality of pixels of a spatial light modulator; and forming a first group of view points by allowing light beams emitted from the first group of grating elements to pass through the plurality of pixels of the spatial light modulator and forming a second group of view points by allowing light beams emitted from the second group of grating elements to pass through the plurality of pixels of the spatial light modulator, wherein a region within which the second group of view points is formed does not overlap with a region within which the first group of view points is formed.

The view points in the first group may be consecutively arranged, and the view points in the second group may be consecutively arranged after the first group of view points.

At least two light beams may pass through each of the plurality of pixel points, and the at least two light beams may include a light beam emitted from one of the grating elements included in the first group and a light beam emitted from one of the grating elements included in the second group.

Light beams emitted from two adjacent grating elements among the first and second groups of grating elements may be directed to different pixels.

3D images shown at the first group of view points may be repeatedly shown at the second group of view points.

The 3D image displaying method may further include tracking eyes of a viewer. The spatial light modulator may be controlled so that pixels corresponding to the tracked eyes of the viewer generate an image.

In the provided directional backlight units, two or more grating elements correspond to each pixel, and thus light beams transmitted by one pixel are simultaneously directed toward view points in several directions while having the same information, whereby the same image may be simultaneously viewed in several directions and thus an angle for viewing a 3D image may be widened.

The provided directional backlight units may be mounted on autostereoscopic 3D display apparatuses (for example, TVs, monitors, tablets, and mobile devices).

The provided directional backlight units may widen a watching angle of a 3D display apparatus.

The provided directional backlight units may easily apply an eye tracking method to 3D display apparatuses.

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