Stereoscopic 3D liquid crystal display apparatus with structured light guide surface

A stereoscopic 3D liquid crystal display apparatus includes a liquid crystal display panel, a backlight positioned to provide light to the liquid crystal display panel, and a double sided prism film disposed between the liquid crystal display panel and the backlight. The backlight includes a light guide having a first side and a second side opposite the first side, and having a first surface extending between the first and second sides and a second surface opposite the first surface. The first surface substantially re-directs light and the second surface substantially transmits light. A plurality of first light sources is arranged along the first side of the light guide for transmitting light into the light guide from the first side. A plurality of second light sources is arranged along the second side of the light guide for transmitting light into the light guide from the second side. The second surface includes a regular array of linear prism or lenticular features. A double sided prism film is disposed between the liquid crystal display panel and the regular array of linear prism or lenticular features.

FIELD

The present disclosure relates to a stereoscopic 3D liquid crystal display apparatus and particularly to a stereoscopic 3D liquid crystal display apparatus including a structured light guide surface.

BACKGROUND

A stereoscopic 3D display usually presents an observer with images with parallax from individual right and left eye viewpoints. There are two methods of providing the two eyes of the observer with the parallax images in a time sequential manner. In one method, the observer utilizes a pair of shutter or 3D glasses which transmit or block light from the viewer's eyes in synchronization with alternating the left/right image display. Similarly, in another method, right eye and left eye viewpoints are alternatively displayed and presented to the respective eyes of the observer but without the use of 3D glasses. This second method is referred to as autostereoscopic and is sometimes desirable for stereo 3D viewing because separate glasses are not needed though there is limited permissible head motion.

A liquid crystal display (LCD) is a sample and hold display device such that the image at any point or pixel of the display is stable until that pixel is updated at the next image refresh time, typically 1/60 of a second or faster. In such a sample and hold system, displaying different images, specifically displaying alternating left and right images for an autostereoscopic display, requires careful timing sequencing of the light sources so that, for example, the left eye image light source is not on during the display of data for the right eye and vice versa.

BRIEF SUMMARY

The present disclosure relates to a stereoscopic 3D liquid crystal display apparatus and particularly to a stereoscopic 3D liquid crystal display apparatus including a structured light guide surface.

In a first embodiment, a stereoscopic 3D liquid crystal display apparatus includes a liquid crystal display panel, a backlight positioned to provide light to the liquid crystal display panel, and a double sided prism film disposed between the liquid crystal display panel and the backlight. The backlight includes a light guide having a first side and a second side opposite the first side, and having a first surface extending between the first and second sides and a second surface opposite the first surface. The first surface substantially re-directs light and the second surface substantially transmits light. A plurality of first light sources is arranged along the first side of the light guide for transmitting light into the light guide from the first side. A plurality of second light sources is arranged along the second side of the light guide for transmitting light into the light guide from the second side. The second surface includes a regular array of linear prism or lenticular features. A double sided prism film is disposed between the liquid crystal display panel and the regular array of linear prism or lenticular features.

In another embodiment, a stereoscopic 3D liquid crystal display apparatus includes a liquid crystal display panel, drive electronics configured to drive the liquid crystal display panel with alternating left eye and right eye images, and a backlight positioned to provide light to the liquid crystal display panel. The backlight includes a backlight positioned to provide light to the liquid crystal display panel. The backlight includes a light guide having a first side and a second side opposite the first side, and having a first surface extending between the first and second sides and a second surface opposite the first surface. The first surface substantially re-directs light and the second surface substantially transmits light. A plurality of first light sources is arranged along the first side of the light guide for transmitting light into the light guide from the first side. A plurality of second light sources is arranged along the second side of the light guide for transmitting light into the light guide from the second side. The second surface includes a regular array of linear prism or lenticular features that extend parallel to a light input propagation axis of the plurality of first and second light sources. A double sided prism film is disposed between the liquid crystal display panel and the regular array of linear prism or lenticular features.

DETAILED DESCRIPTION

The term “elongated” feature refers to a linear feature having substantially the same cross-section along a linear length of the feature.

The term “autostereoscopic” refers to displaying three-dimensional images that can be viewed without the use of special headgear or glasses on the part of the user or viewer. These methods produce depth perception for the viewer even though the image is produced by a flat device. The term stereoscopic 3D incorporates the field of autostereoscopic devices but also includes the stereoscopic 3D display case in which special headgear, typically shutter glasses, are need to see stereoscopic 3D from a flat device.

The present disclosure relates to a stereoscopic 3D liquid crystal display apparatus and particularly to a stereoscopic 3D liquid crystal display apparatus including a structured light guide surface. This apparatus can provide a uniformly lit 3D image with increased light extraction efficiency relative to unstructured light guide. This disclosure presents a backlight for a stereoscopic 3D liquid crystal display that includes microreplicated structures that provides substantially uniform transmission of light emitted from the backlight and transmitted into a double-sided prism film. This configuration reduces or eliminates “headlighting” or imaging of discrete backlight light sources, such as light emitting diodes, improves overall light extraction efficiency of the backlight, while maintaining the angular distribution of the light out of the backlight. Maintaining the angular distribution of the light out of the backlight allows the stereoscopic 3D liquid crystal display apparatus to continue to provide a stereoscopic 3D image to a viewer.

One or more of these embodiments may be combined in a single display capable of providing a 3D visualization capability from a flat display either in a shutter glasses stereoscopic 3D display mode or in an autostereoscopic display mode. While the present invention is not so limited, an appreciation of various aspects of the invention will be gained through a discussion of the examples provided below.

A liquid crystal display is a sample and hold display device such that the image at any particular point is stable until that point or pixel is updated at the next image refresh time, typically within 1/60 of a second or faster. In such a sample and hold system, displaying different images, specifically alternating left and right images for a 3D display, during sequential refresh periods of the display requires careful sequencing of the backlight light sources so that, for example, the left eye light source is not on during the display of data for the right eye and vice versa.

FIG. 1is a schematic side view of an illustrative display apparatus10. The display apparatus includes a liquid crystal display panel20and a backlight30positioned to provide light to the liquid crystal display panel20. The backlight30includes a right eye image solid state light source32or plurality of first light sources32, and a left eye image solid state light source34or plurality of second light sources34, capable of being modulated between the right eye image solid state light source32and the left eye image solid state light source34at a rate of, in many embodiments, at least 90 Hertz. A double sided prism film40is disposed between the liquid crystal display panel20and the backlight30.

The liquid crystal display panel20and/or backlight30can have any useful shape or configuration. In many embodiments, the liquid crystal display panel20and backlight30has a square or rectangular shape. However, in some embodiments, the liquid crystal display panel20and/or backlight30has more than four sides or is a curved shape. While the present disclosure is directed to any stereoscopic 3D backlight including those requiring shutter glasses or more than a single lightguide and associated liquid crystal display panel, the present disclosure is particularly useful for autostereoscopic displays.

A synchronization driving element50is electrically connected to the backlight30plurality of first and second plurality of light sources32,34and the liquid crystal display panel20. The synchronization driving element50synchronizes activation and deactivation (i.e., modulation) of the right eye image solid state light source32and the left eye image solid state light source34as image frames are provided at a rate of, in many embodiments, 90 frames per second or greater to the liquid crystal display panel20to produce a flicker-free still image sequence, video stream or rendered computer graphics. An image (e.g., video or computer rendered graphics) source60is connected to the synchronization driving element50and provides the images frames (e.g., right eye images and left eye images) to the liquid crystal display panel20.

The liquid crystal display panel20can be any useful transmissive liquid crystal display panel. In many embodiments, liquid crystal display panel20has a frame response time of less than 16 milliseconds, or less than 10 milliseconds, or less than 5 milliseconds. Commercially available transmissive liquid crystal display panels having a frame response time of less than 10 milliseconds, or less than 5 milliseconds, or less than 3 milliseconds, are for example Toshiba Matsushita Display's (TMD) optically compensated bend (OCB) mode panel LTA090A220F (Toshiba Matsushita Display Technology Co., Ltd., Japan).

The backlight30can be any useful backlight that can be modulated between a right eye image solid state light source32and left eye image solid state light source34at a rate of, in many embodiments, at least 90 Hertz, or 100 Hertz, or 110 Hertz, or 120 Hertz, or greater than 120 Hertz.

The illustrated backlight30includes a first side31or first light input surface31adjacent to the plurality of first light sources32or right eye image solid state light source32and an opposing second side33or second light input surface33adjacent to the plurality of second light sources34or left eye image solid state light source34. A first surface36extends between the first side31and second side33and a second surface35, opposite the first surface36, extends between the first side31and second side33. The first surface36substantially re-directs (e.g., reflects, extracts, and the like) light and the second surface35substantially transmits light. In many embodiments, a highly reflective surface is on or adjacent to the first surface36to assist in re-directing light out through the second surface35.

The second surface35(i.e., light transmission surface35) includes a plurality of microreplicated features43. These features43are illustrated as v-shaped grooves, rectangular channels, elongated prism or lenticular features43(seeFIG. 3) that extend parallel to a light input propagation axis PAof the plurality of first light sources32and plurality of second light sources34. The light input propagation axis PAgenerally refers to a centerline axis of light propagating through the light guide. In many embodiments, the microreplicated features43are a regular array of linear prism or lenticular features. In many embodiments, the elongated features43extend orthogonal to the adjacent elongated prism features42or lenticular features41of the double prism film40. These features43are further described with reference toFIG. 3below.

In many embodiments, the first surface36includes a plurality of extraction elements such as, for example, linear prism or lenticular features as shown. In many embodiments, the linear prism or lenticular features can extend in a direction parallel to the first side31and second side33or parallel to the linear prism and lenticular features of the double sided prism film40.

The solid state light sources can be any useful solid state light source that can be modulated at a rate of, for example, at least 90 Hertz. In many embodiments, the solid state light source is a plurality of light emitting diodes such as, for example, Nichia NSSWO20B (Nichia Chemical Industries, Ltd., Japan). In other embodiments, the solid state light source is a plurality of laser diodes or organic light emitting diodes (i.e., OLEDs). The solid state light sources can emit any number of visible light wavelengths such as red, blue, and/or green, or range or combinations of wavelengths to produce, for example, white light. The backlight can be a single layer of optically clear material with light sources at both ends or two (or more) layers of optically clear material with a light source per layer which preferentially extract light in a desired direction for each layer.

The double sided prism film40can be any useful prism film having elongated lenticular features41structure on a first side or major surface and elongated prismatic features42on an opposing side. The double sided prism film40transmits light from the backlight to the liquid crystal display panel20at the proper angles such that a viewer perceives depth in the displayed image. Useful, double sided prism films are described in United States Patent Publication Nos. 2005/0052750 and 2005/0276071, which are incorporated herein to the extent they do not conflict with the present disclosure.

The image source60can be any useful image source capable of providing images frames (e.g., right eye images and left eye images) such as, for example, a video source or a computer rendered graphic source. In many embodiments, the video source can provide image frames from 50 to 60 Hertz or greater. In many embodiments, the computer rendered graphic source can provide image frames from 100 to 120 Hertz or greater.

The computer rendered graphic source can provide gaming content, medical imaging content, computer aided design content, and the like. The computer rendered graphic source can include a graphics processing unit such as, for example, an Nvidia FX5200 graphics card, a Nvidia GeForce 9750 GTX graphics card or, for mobile solutions such as laptop computers, an Nvidia GeForce GO 7900 GS graphics card. The computer rendered graphic source can also incorporate appropriate stereo driver software such as, for example, OpenGL, DirectX, or Nvidia proprietary 3D stereo drivers.

The video source can provide video content. The video source can include a graphics processing unit such as, for example, an Nvidia Quadro FX1400 graphics card. The video source can also incorporate appropriate stereo driver software such as, for example, OpenGL, DirectX, or Nvidia proprietary 3D stereo drivers.

The synchronization driving element50can include any useful driving element providing synchronizing activation and deactivation (i.e., modulation) of the right eye image solid state light source32and the left eye image solid state light source34with image frames provided at a rate of, for example, 90 frames per second or greater to the liquid crystal display panel20to produce a flicker-free video or rendered computer graphics. The synchronization driving element50can include a video interface such as, for example, a Westar VP-7 video adaptor (Westar Display Technologies, Inc., St. Charles, Mo.) coupled to custom solid state light source drive electronics.

FIG. 2AandFIG. 2Bare schematic side views of an illustrative display apparatus10in operation. InFIG. 2Athe left eye image solid state light source34(i.e., plurality of second light sources34) is illuminated and the right eye image solid state light source32(i.e., plurality of first light sources32) is not illuminated. In this state, the light emitted from the left eye image solid state light source34transmits through the backlight30microreplicated features43, through the double sided prism sheet40, and liquid crystal panel20providing a left eye image directed toward the left eye1aof an viewer or observer. InFIG. 2Bthe right eye image solid state light source32is illuminated and the left eye image solid state light source34is not illuminated. In this state, the light emitted from the right eye solid state light source32transmits through the backlight30microreplicated features43, through the double sided prism sheet40, and liquid crystal panel20providing a right eye image directed toward the right eye1bof an viewer or observer. It is understood that while the right eye solid state light source32is located on the right side of the light guide and the left eye image solid state light source34is located on the left side of the light guide, is some embodiments, the right eye solid state light source32is located on the left side of the light guide and the left eye image solid state light source34is located on the right side of the light guide.

Liquid crystal display panels20have a refresh or image update rate that is variable, but for the purposes of this example, a 60 Hz refresh rate is presumed. This means that a new image is presented to the viewer every 1/60 second or 16.67 milliseconds (msec). In the 3D system this means that at time t=0 (zero) the right image of frame one is presented. At time t=16.67 msec the left image of frame one is presented. At time t=2*16.67 msec the right image of frame two is presented. At time t=3*16.67 msec the left image of frame two is presented, and this process is thus repeated. The effective frame rate is half that of a normal imaging system because for each image a left eye and right eye view of that image is presented.

In this example, turning the first plurality of light sources on to light the right (or left) image at time t=0 provides light to the right (or left) image, respectively. At time t=16.67 msec the second image left or right, starts to be put in place. This image replaces the “time t=0 image” from the top of the LCD panel to the bottom of the LCD, which takes 16.67 msec to complete in this example.

Providing at least 45 left eye images and at least 45 right eye images (alternating between right eye and left eye images and the images are possibly a repeat of the previous image pair) to a viewer per second provides a flicker-free 3D image to the viewer. Accordingly, displaying different right and left viewpoint image pairs from computer rendered images or images acquired from still image cameras or video image cameras, when displayed in synchronization with the switching of the light sources32and34, enables the viewer to visually fuse the two different images, creating the perception of depth from the flat panel display. A limitation of this visually flicker-free operation is that, as discussed above, the backlight should not be on until the new image that is being displayed on the liquid crystal display panel has stabilized; otherwise cross-talk and a poor stereoscopic image will be perceived.

FIG. 3is a schematic diagram front view of an illustrative backlight30for displaying alternating right and left images. The backlight30, as described above, includes a first side31or first light input surface31adjacent to the plurality of first light sources32or right eye image solid state light source32, and an opposing second side33or second light input surface33adjacent to the plurality of second light sources34or left eye image solid state light source34. A first surface36(shown inFIG. 1) extends between the first side31and second side33and a second surface35, opposite the first surface, extends between the first side31and second side33. The first surface36substantially re-directs (e.g., reflects, extracts, and the like) light and the second surface35substantially transmits light to the double sided prism film (through the features43) and LCD panel, as described inFIG. 1.

The microreplicated features43are elongated and in many embodiments, are disposed parallel to one another and also parallel to a light input propagation axis PAof the first plurality of light sources32and second plurality of light sources34. The microreplicated features43can extend in a side-by-side parallel manner between the first side31and the second side33. In many embodiments, the microreplicated features43or regular array of linear prism or lenticular features43have optical power in a vertical direction and negligible optical power in an orthogonal horizontal direction. These microreplicated features43reduce or eliminate “headlighting” or imaging of the discrete solid state light sources, improve overall light extraction efficiency of the backlight, while maintaining the angular distribution of the light out of the backlight.

FIG. 4andFIG. 5provide illustrative schematic side views of the light input side31of the disclosed backlight30. The backlight microreplicated features43are adjacent to the double sided prism film40having elongated lenticular features41on a first side or major surface and elongated prismatic features42on an opposing side. In many embodiments, the elongated lenticular features41structure on a first side or major surface and elongated prismatic features42on an opposing side extend orthogonal to the backlight microreplicated elongated features43.

FIG. 4is one embodiment illustrating lenticular features43that are elongated and disposed parallel to one another and also parallel to a light input propagation axis PAof the first plurality of light sources32. These lenticular features43have a radius of curvature r in a range from 1 to 250 micrometers or from 10 to 100 micrometers, or from 25 to 75 micrometers.FIG. 5is one embodiment illustrating prism features43that are elongated and disposed parallel to one another and also parallel to a light input propagation axis PAof the first plurality of light sources32. These prism features43have a height h in a range from 1 to 250 micrometers or from 1 to 75 micrometers, or from 5 to 50 micrometers. In many embodiments, the parallel elongated microreplicated features43described above have a period or pitch p (e.g., from apex to apex, or from feature to feature) in a range from 1 to 1000 micrometers, or from 1 to 500 micrometers, or from 1 to 250 micrometers, or from 1 to 100 micrometers, or from 10 to 75 micrometers.

The microreplicated features43can be placed or formed in the second surface35(light transmission surface of backlight30) by any useful method. In many embodiments, the microreplicated features43are molded or cut into the second surface35. In other embodiments, the microreplicated features43are provided on a separate layer or film that is adhered to the second surface35.

Thus, embodiments of the STEREOSCOPIC 3D LIQUID CRYSTAL DISPLAY APPARATUS WITH STRUCTURED LIGHT GUIDE SURFACE are disclosed. One skilled in the art will appreciate that the present invention can be practiced with embodiments other than those disclosed. The disclosed embodiments are presented for purposes of illustration and not limitation, and the present invention is limited only by the claims that follow.