Stereoscopic display device with two liquid crystal displays

A stereoscopic display device is provided for displaying a 3-dimensional image including a first slice, a second slice and a third slice arranged in the order written. The stereoscopic display device includes a first LCD, a second LCD adjacent to the first LCD and a distance adjusting member. The first LCD has a first display surface. The second LCD is spaced from the first LCD. The second liquid crystal display having a second display surface facing away from the first display surface. The distance adjusting member is arranged between the first and second LCDs. The distance adjusting member is configured for reciprocally moving the first LCD relative to the second LCD between a first position where the first LCD displaying a contour of the second slice and a second position where the first LCD displaying a contour of the third slice.

BACKGROUND

1. Technical Field

The present disclosure relates to a stereoscopic display device and a method for displaying a three-dimensional (3-D) image.

2. Description of Related Art

Objects are seen in three dimensions because light reflects from them and generates a light field in space. The two eyes of a viewer perceive this light field differently due to their positioning in space relative to the object, and the brain of the viewer processes the different perceptions of the light field by the two eyes to generate 3-D perception.

Stereoscopic imaging is one technique utilized to simulate 3-D images to viewers. Stereoscopic displays work by providing differing yet corresponding perspective images of the same object or scene to the left and right eye of the viewer. Accordingly, viewers' minds process these two images to produce a perception of three dimensions. The principles of stereoscopic imaging have been applied variously for years, including in the training of pilots and physicians, and in entertainment, 3-D movies and computer games. All stereoscopic systems rely on a legion of techniques to segregate images for the right and left eye. Typically, stereoscopic imaging systems utilize special parallax barrier screens: headgear, or eye wear to insure that the left eye sees only the left eye perspective and the right eye sees only the right eye perspective.

U.S. Pat. No. 5,745,197 issued to Leung et al, discloses a “volumetric” display intended to provide a type of 3-D images with real physical height, depth, and width by activating actual light sources at various depths within the volume of the viewer perceive various image elements at different depths within the volume of the display in perspective, thus creating a 3-D effect. The Leung et al. volumetric display utilizes a physical deconstruction of a 3-D object that entails “slicing” the object into pieces by planes oriented perpendicular to the view path of the viewer. Images corresponding to the resulting slices are then displayed superimposed on a stack of transmissive display screens (corresponding to the perpendicular slicing planes) layered at sequentially increasing distances from the viewer. The volumetric display thereby creates the appearance of a 3-D image by reproducing individual cross sections of a contoured object on a series of screens wherein images on the screens closer to the viewer are stacked on top of more distant image pieces. This essentially, is 3-D effect created in mechanical fashion. This type of volumetric display requires the layering of two or more transmissive imaging display panels to create the effect of depth, so the depth, number and distance between the various display screens on which the image slices appear limit its 3-D effect necessarily. However, the depth between each two various display screens is changeless such that the display cannot create a good 3-D effect. Additionally, large display screens mean higher associated cost.

Therefore, an stereoscopic display device which can overcome the above-mentioned problems is desired.

DETAILED DESCRIPTION

Various embodiments will now be described in detail below with reference to the drawings.

Referring toFIGS. 1 and 2, an stereoscopic display device10in accordance with a first exemplary embodiment includes a first LCD11, a second LCD12, a backlight module13, a polarization rotation plate14, and a distance adjusting member15. The backlight module13is arranged at an opposite side of the first LCD11relative to the second LCD12.

The backlight module13is configured for providing light to the first and second LCDs11and12. The backlight module13can include a plurality of cold cathode fluorescence lamp and various optical plates, or include a plurality of light emitting diodes and various optical plates. As shown inFIG. 2, light rays100emitted from the backlight module13transmit through the first LCD11, the polarization rotation plate14and the second LCD12in the described order.

It is known that, each of the first LCD11and second LCD12includes two polarizers and a liquid crystal layer between the two polarizers. The polarization rotation plate14is attached on a surface of the second LCD12. The polarization rotation plate14is configured for rotating a polarization direction of light output from the first LCD11to a polarization direction substantially parallel to a polarization axis of the polarizer associated with the second LCD12adjacent to the first LCD11, such that more light can transmit through the second LCD12.

It is to be understood that, the polarizer of the first LCD11adjacent to the second LCD12or the polarizer of the second LCD12adjacent to the first LCD11is omissible. Accordingly, the polarization rotation plate14is omissible. The polarizer of the first LCD11adjacent to the second LCD12can also have a polarization axis parallel to that of the polarizer of the second LCD12adjacent to the first LCD11. Accordingly, the polarization rotation plate14is omissible.

The polarization rotation plate14can be comprised of Tb2O3-B2O3-Al2O3SiO2 having a magneto-optic effect. In use, a magnetic field perpendicular to the first and second LCDs11,12is applied to the polarization rotation plate14. When light is transmitted through the polarization rotation plate14, the plane of polarization can be rotated a rotation angle Ψ because of the Faraday Effect. Assuming that the magnetic field has a magnetic induction intensity B, and a thickness of the polarization rotation plate14is defined a distance L, the angle Ψ can be represented by the following formula: Ψ=VBL, wherein V is a verdet constant. The verdet constant V is determined by properties of the polarization rotation plate14and frequencies of the light transmitting through the polarization rotation plate14. Thus, the rotation angle Ψ can vary by changing the magnetic induction intensity B and/or the distance L.

The distance adjusting member15can be motors, such as step motors. In this exemplary embodiment, the distance adjusting member15includes four step motors150. The four step motors150are arranged adjacent to four corners of the first and second LCDs11and12. The distance adjusting member15is configured for reciprocally moving the first LCD11relative to the second LCD12. Each of the step motors150includes a stator151and a mover152. One end of the stator151is fixed to the first LCD11, and one end of the mover152is fixed to the second LCD12. The fixing between the stator151and the first LCD11or between the mover152and the second LCD12may be achieved, for example, with transparent adhesive. The mover152can be regulated toward or away from the second LCD12by electric power, which is provided to the step motor150. Thus the first LCD11is regulated toward or away from the second LCD12. In the present embodiment, the mover152is an actuating shaft partly received and slidable in the stator151. It is to be understood that the distance adjusting member15can also be another driving device, such as a servomotor, a voice coil motor etc.

Referring toFIG. 3, the first LCD11is moved to a first position close to the second LCD12by the distance adjusting member15. Referring toFIG. 4, the first LCD11is moved to a second position far from the second LCD12.

Referring also toFIGS. 5-7, stacking of LCDs11and12forms the stereoscopic display for viewing a 3-D image32. The image32is preferably imaged along image slices32a,32bthrough32clying orthogonal along a line of sight16as shown inFIG. 1, which is perpendicular to the first and second LCDs11and12. The second LCD12images a contour34acorresponding to the slice32a, and the first LCD11images contours34b,34ccorresponding to the slices32b,32c. The contour34bis displayed when the first LCD11is in the first position as shown inFIG. 3, and the contour34cis displayed when the first LCD11is in the second position as shown inFIG. 4. The first LCD11is driven by the distance adjusting member15to move from the first position to the second position back and forth at a predetermined frequency. When the predetermined frequency is larger than a certain value, persistence of vision generates in eyes of the viewer. Generally, the predetermined frequency is at least 60 Hertz. That is, the contours34band34ccan be seen at the same time by the viewer because of persistence of vision in eyes of the viewer. Therefore, the LCDs11and12display respectively representing slices32a,32b,32cof the 3-D image32. When viewed as a stack, as shown inFIG. 7, the contours34a,34bthrough34c, appear to a viewer as a solid 3-D contour image34comprising superimposed contour slices34a,34band34c.

The stereoscopic display device10has two working modes described as follows. One of the two working modes is called, page-flipping mode. In this mode, the second LCD12, the first LCD11at a first position, and the first LCD at a second position display by turns at a predetermined frequency. At a time, only one of the LCDs11and12displays its corresponding image. When the first LCD11displays an image, the second LCD12is in a light-pervious state. For utilizing persistence of vision in eyes of the viewer, the predetermined frequency is higher than a certain value, generally 60 hertz. Thus, the stereoscopic display device10can display a solid 3-D contour image comprising superimposed contour slices displayed by the second LCD12and the first LCD11.

The other one of the two working modes is that the second LCD12displays its corresponding contour image all along, and the first LCD11displays its corresponding contour images at different positions by turns at a predetermined frequency. A portion of the first LCD12aligned with the contour images displayed by the first LCD11is in a light-pervious state. Thus, the stereoscopic display device10can display a solid 3-D contour image comprising superimposed contour slices displayed by the second LCD12and the first LCD11.

It is to be understood that the 3-D image32can also be partitioned into more than three slices. Accordingly, the second LCD12displays the top slice, and the first LCD11displays the other slices. In that case, more positions are defined when the first LCD11is driven to move from a position close to the second LCD12to another position far away from the second LCD12. In this embodiment, a distance D1between first and second LCDs11and12can vary from 2 mm to 10 mm by virtue of the distance adjusting member15.

The stereoscopic display device20includes two LCDs11,12with a changeable distance therebetween. Thus, the stereoscopic display device20can display different depths of an image by changing the distance between the two LCDs11,12, thereby achieving better 3-D display effect. In addition, in the stereoscopic display device20of this embodiment, there is no need to arrange too many LCDs to display different depths.

Referring toFIG. 8, a stereoscopic display device20in accordance with a second exemplary embodiment includes a first LCD21, a second LCD22, a light source module23, a polarization rotation plate24, and a distance adjusting member25. The first and second LCDs21and22are identical to the first and second LCDs11and12. The light source module23, the polarization rotation plate24and the distance adjusting member25are arranged between the first and second LCDs21and22.

The light source module23includes a light guide plate230, a light source233and a reflective cover234. The light guide plate230includes a base plate231and a number of columnar protrusions232formed on a surface of the base plate231. The columnar protrusions232are integrally formed with the light guide plate230. That is, the light guide plate230is a single body of material comprising the base plate231and the columnar protrusions232. The columnar protrusions232are arranged adjacent to the first LCD21. In this embodiment, the light source233is a cold cathode fluorescence lamp, and positioned facing a side surface of the base plate231. The reflective cover234is arranged partly surrounding the light source233for reflecting light emitted from the light source233into the base plate231.

The reflective plate26is arranged on a surface of the first LCD21at an opposite side of the first LCD relative to the light guide plate230. The reflective plate26is configured for reflecting the light emitted from the light source module23back to the first LCD21. Alternatively, the reflective plate26can substitute a reflective film coating on a surface of the first LCD21.

Because the base plate231is very thin, most of the light emitted from the light source233transmits in the light guide plate231and less outputs because of total reflection, except the light striking on the side surface of the columnar protrusions232. The light striking on the side surface of the columnar protrusions232exits from the light guide plate231and transmits toward the reflective plate26. Afterwards, the reflective plate26reflects light to the first LCD21whereupon the transmission goes through the light guide plate231and the second LCD22. Arrows200inFIG. 8illustrate the light path.

The polarization rotation device24is identical to the polarization rotation device14and configured for rotating the polarization direction of light emitted from the first LCD21, thereby passing through the second LCD22. The polarization rotation device24is arranged sandwiched between the first LCD21and the light guide plate232. It is to be understood that the polarization rotation device24can also be arranged between the light source module23and the second LCD22.

The distance adjusting member25is identical to the distance adjusting member15and includes four step motors250. Each of the step motor250includes a stator251and a mover252. The adjusting device25is arranged between the second LCD22and the light guide plate230. The four step motors250are arranged at four corners of the second LCD22. One end of the stator251is fixed on the light guide plate230and one end of the mover252is fixed on a surface of the second LCD22. The distance adjusting member25is configured for driving the light guide plate230close to and away from the second LCD22, thereby driving the first LCD21close to and away from the second LCD22. In this embodiment, a distance D2between the light guide plate230and the second LCD22can vary from 2 mm to 10 mm.

It is to be understood that the number of step motors250of the distance adjusting member25can vary according to need, such as less than four or more than four. The motor(s)250can also be arranged at the center of the first LCD21or the second LCD22. The distance adjusting member15can also be selected from other driving devices such as a servomotor and a voice coil motor.

In addition, the number of LCDs11and12can be more than two. Accordingly, more distance adjusting members are arrangeable between two adjacent LCDs to achieve better 3-D display effect.

Referring toFIGS. 3-7a method for displaying 3-D images using the stereoscopic display device10is described as follows.

Firstly, the first LCD11and the second LCD are provided. The second LCD12is parallel with the first LCD11. The first and second LCD11and12are arranged facing a same direction.

The 3-D object32is partitioned into a number of slices with different depths, such as three slices32a,32b,32cas shown inFIG. 5. Then the image data of slices32a,32b,32cis converted into sliced contours34a,34b,34c, respectively. The contour34ais the top one of the sliced contours34a,34b,34c.

Secondly, The first LCD11is reciprocally moved relative to the second LCD12between a first position close to the second LCD12as shown inFIG. 3and a second position far from the second LCD12as shown inFIG. 4at a predetermined frequency. The second LCD12, which is close to the viewer, displays the contour34a. The first LCD11displays the contour34bwhen moved to the first position, and displays the contour34cwhen moved to the second. The predetermined frequency is preferably greater than 60 hertz such that persistence of vision generates viewers' eyes. Thus, the contours34a,34bthrough34c, when viewed as a stack, and as shown inFIG. 7, appear to a viewer as a solid 3-D contour image34comprising superimposed contour slices34a,34band34c. A distance between the first LCD11and the second LCD12can be changed from 2 mm to 10 mm.

Finally, it is to be understood that the above-described embodiments are intended to illustrate rather than limit the disclosure. Variations may be made to the embodiments without departing from the spirit of the disclosure. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.