WO2006033046A1

WO2006033046A1 - 2d / 3d switchable display device and method for driving

Info

Publication number: WO2006033046A1
Application number: PCT/IB2005/052998
Authority: WO
Inventors: Wilbert L. Ijzerman
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2004-09-22
Filing date: 2005-09-13
Publication date: 2006-03-30

Abstract

A method of driving a switchable display device (300) which is arranged to display first visual data on a first portion (102) of the display device (300), the first portion (102) being in a first display mode, and to display second visual data on a second portion (104) of the display device (300), the second portion (104) being in a second display mode which is different from the first display mode, is disclosed. The method comprises switching the display mode of the display device (300) to the first display mode or the second display mode when a signal is received indicating that the first visual data is to be displayed on a third portion (105) of the display device (300) being different from the first portion (102) of the display device (300).

Description

2D/3D SWITCHABLE DISPLAY DEVICE AND METHOD FOR DRIVING

The invention relates to a method of driving a switchable display device which is arranged to display first visual data on a first portion of the display device, the first portion being in a first display mode, and to display second visual data on a second portion of the display device, the second portion being in a second display mode which is different from the first display mode.

The invention further relates to a switchable display device which is arranged to display first visual data on a first portion of the display device, the first portion being in a first display mode and to display second visual data on a second portion of the display device, the second portion being in a second display mode which is different from the first display mode.

The invention further relates to a computer program product to be loaded by a computer arrangement, comprising instructions to drive a switchable display device which is arranged to display first visual data on a first portion of the display device, the first portion being in a first display mode, and to display second visual data on a second portion of the display device, the second portion being in a second display mode which is different from the first display mode.

Since the introduction of display devices, a realistic 3-D display device has been a dream for many. Many principles that should lead to such a display device have been investigated. Some principles try to create a realistic 3-D object in a certain volume. For instance, in the display device as disclosed in the article " Solid-state Multi-planar Volumetric Display", by A. Sullivan in proceedings of SID'03, 1531-1533, 2003, visual data is displaced at an array of planes by means of a fast projector. Each plane is a switchable diffuser. If the number of planes is sufficiently high the human brain integrates the picture and observes a realistic 3-D object. This principles allows a viewer to look around the object within some extend. In this display device all objects are (semi-)transparent.

Many others try to create a 3-D display device based on binocular disparity only. In these systems the left and right eye of the viewer perceives another image and consequently, the viewer perceives a 3-D image. An overview off these concepts can be found in the book "Stereo Computer Graphics and Other True 3-D Technologies", by D. F. McAllister (Ed.), Princeton University Press, 1993. A first principle uses shutter glasses in combination with for instance a CRT. If the odd frame is displayed, light is blocked for the left eye and if the even frame is displayed light is blocked for the right eye.

Display devices that show 3-D without the need for additional appliances are called auto-stereoscopic display devices.

A first glasses- free display device comprises a barrier to create cones of light aimed at the left and right eye of the viewer. The cones correspond for instance to the odd and even sub-pixel columns. By addressing these columns with the appropriate information, the viewer obtains different images in his left and right eye if he is positioned at the correct spot, and is able to perceive a 3-D picture.

A second glasses- free display device comprises an array of lenses to image the light of odd and even sub-pixel columns to the viewer's left and right eye. The disadvantage of the above mentioned glasses-free display devices is that the viewer has to remain at a fixed position. To guide the viewer, indicators have been proposed to show the viewer that he is at the right position. See for instance United States patent US5986804 where a barrier plate is combined with a red and green led. In case the viewer is well positioned he sees a green light, and a red light otherwise. To relieve the viewer of sitting at a fixed position, multi-view auto- stereoscopic display devices have been proposed. See for instance United States patents US60064424 and US20000912. In the display devices as disclosed in US60064424 and US20000912 a slanted lenticular is used, whereby the width of the lenticular is larger than two sub-pixels. In this way there are several images next to each other and the viewer has some freedom to move to the left and right.

A drawback of auto-stereoscopic display devices is the resolution loss incorporated with the generation of 3-D images. It is advantageous that those display devices are switchable between a 2-D and 3-D mode, i.e. a single- view mode and a multi-view mode. If a relatively high resolution is required, it is possible to switch to the single- view mode since that has higher resolution.

An example of such a switchable display device is described in the article "A lightweight compact 2-D/3-D autostereoscopic LCD backlight for games, monitor and notebook applications" by J. Eichenlaub in proceedings of SPIE 3295, 1998. It is disclosed that a switchable diffuser is used to switch between a 2-D and 3-D mode. Another example of a switchable auto-stereoscopic display device is described in WO2003015424 where LC based lenses are used to create a switchable lenticular.

In principle it is possible to switch the entire display device from 2-D to 3-D and vice versa. Alternatively, only a portion of the display device is switched. In many graphical user interfaces use is made of windows. Typically, a user is able to move the windows across the screen of the display device. Suppose that a graphical user interface comprises a background which is in single-view mode, i.e. 2-D mode and comprises a window which is in multi-view mode, i.e. 3-D mode. Moving the 3-D window from a first position to a second position means that the corresponding visual information is first displayed at a first portion of the display device and later on displayed at another portion of the display device. That means that before movement of the window only the first portion of the display device is in 3-D mode and after the movement only the other portion of the display device is in 3-D mode. During the actual movement of the 3-D window a number of switchings of portions of the display device are performed. Typically, at one side of the 3-D window switching from 2-D mode into 3-D mode is performed while at the opposite side of the 3-D window switching from 3-D mode into 2-D mode is performed. Unfortunately, the switching is performed relatively slowly. This results in visible artifacts. Consider that visual data which is provided to the light generating means of the display device and the actual status of the optical directing means are locally out of phase. For instance, single- view visual data is provided while the local optical directing means are still in multi-view mode.

It is an object of the invention to provide a method of the kind described in the opening paragraph resulting in less visible visual artifacts during movement of a window across the display device.

This object of the invention is achieved in that the method comprises switching the display mode of the display device to the first display mode or the second display mode when a signal is received indicating that the first visual data is to be displayed on a third portion of the display device being different from the first portion of the display device. That means that during the movement the display device is in one mode only which may be either the first display mode or the second display mode. No fast switching is needed during movement, because the portion of the display device adjacent to the window, initially adjacent to the first portion, is in the same display mode as the window itself. The first display mode and the second display mode differ in the number of views, i.e. the first display mode corresponds to a first number of views and the second display mode corresponds to a second number of views whereby the first number of views and the second number of views are mutually different. Typically, the first display mode and the second display mode are from a set of display modes comprising single- view mode and multi-view mode.

A number of cases can be distinguished: the first portion is in the single-view mode and the second portion is in the multi-view mode before the switching, and the display device is switched to the single- view mode when the signal is received. the first portion is in the single- view mode and the second portion is in the multi-view mode before the switching, and the display device is switched to the multi-view mode when the signal is received. the first portion is in the multi-view mode and the second portion is in the single- view mode before the switching, and the display device is switched to the single- view mode when the signal is received. the first portion is in the multi-view mode and the second portion is in the single- view mode before the switching, and the display device is switched to the multi-view mode when the signal is received. Preferably, the method according to the invention further comprises switching the display mode of the third portion to the first display mode and switching a further portion of the display device to the second display mode after a predetermined time after the reception of the signal. In other words, after the movement of the window has stopped different portions of the display device are put in different view-modes. It is a further object of the invention to provide a switchable display device of the kind described in the opening paragraph having relatively low visual artifacts during movement of a window across the display device.

This object of the invention is achieved in that the switchable display device is arranged to switch the display mode of the display device to the first display mode or the second display mode when a signal is received indicating that the first visual data is to be displayed on a third portion of the display device being different from the first portion of the display device. It is a further object of the invention to provide a computer program product of the kind described in the opening paragraph resulting in less visible visual artifacts during movement of a window across the display device.

This object of the invention is achieved in that the computer program product, after being loaded, provides said processing means with the capability to switch the display mode of the display device to the first display mode or the second display mode when a signal is received indicating that the first visual data is to be displayed on a third portion of the display device being different from the first portion of the display device.

Modifications of the image conversion unit and variations thereof may correspond to modifications and variations thereof of the image processing apparatus, the method and the computer program product, being described.

These and other aspects of the switchable display device, of the method and of the computer program product, according to the invention will become apparent from and will be elucidated with respect to the implementations and embodiments described hereinafter and with reference to the accompanying drawings, wherein:

Fig. 1 schematically shows the movement of a 3-D window across a 2-D background; Figs. 2A-2C schematically show the method according to the invention; and

Fig. 3 schematically shows an embodiment of the switchable display device according to the invention.

Same reference numerals are used to denote similar parts throughout the figures.

Fig. 1 schematically shows the movement of a 3-D window 102 across a 2-D background. Fig. 1 schematically shows a switchable display device 100 according to the prior art. E.g. as disclosed in US 6,137,456 or US 6,157,351 or US 6,285,368. On the switchable display device a background image 104 is displayed in 2-D mode and a window 102 in 3-D mode. Suppose that the switchable display device 100 according to the prior art comprises an optical directing unit for transferring the generated light in dependence of an actual view mode of a portion of the display device. Unfortunately, switching from a first state into a second state or reverse is relatively slow. In fact that is not a problem as long as the window 102 is stationary, i.e. the visual data corresponding to the window 102 is continuously displayed on the same portion of the display device. However, when repositioning of the window 102 is required visible artifacts may occur. Suppose that on basis of user input a new position of the window 102 is required, e.g. a shift to the right. As a result of that basically two things take place. New driving values for the light generating unit of the display device are computed in correspondence to the intermediate and eventually end position of the window 102. Besides that, the elements of the optical directing unit are controlled in correspondence to the intermediate and eventually end position of the window 102. The physical properties of the elements of the optical directing unit are such that actually switching from a first display mode to a required display mode may be out of phase related to the provided driving values. This means that for instance at a particular moment in time a first portion 106 of the display device 100 and a second portion 108 of the display device 100 clearly show artifacts. For the first portion 106 the provided driving values for the light generating unit correspond to 2-D mode while the local elements of the optical directing unit are still in 3-D mode. For the second portion 108 the provided driving values for the light generating unit correspond to 3-D mode while the local elements of the optical directing unit are still in 2-D mode.

Figs. 2A-2B schematically show the method according to the invention. Fig. 2 A schematically shows a switchable display device 300 according to the invention. The switchable display device is arranged to display first visual data 102 on a first portion of the display device, the first portion being in a multi-view mode, and to display second visual 104 data on a second portion of the display device, the second portion being in a single- view mode. That means that during a particular time interval the first portion 102 of the display device 300 is in another view mode than the second portion 104 of the display device 300, i.e. two different view modes simultaneously.

At a particular moment the display device 300 receives an update signal, indicating that the first visual data is to be displayed on a third portion of the display device being different from the first portion of the display device. As result of that update signal the entire display device 300 switches to the single-view mode. This is indicated in Fig. 2 B. Alternatively, the entire display device 300 switches to multi-view mode.

During movement of the window the entire display device 300 remains in that view mode. After the movement has stopped, e.g. because no user input related to movement of the window has been received for a predetermined time or a "movement stop event" has been received, the display device 300 switches back into different view modes. Fig. 2C schematically shows that a further portion 105 corresponding to the window is in multi-view mode while the rest of the display device 300 is still in single- view mode.

In the example above it is described that a 3-D window is moved across a background which is in single-view mode. Moving a 2 -D window across a 3-D background may be performed in a similar way.

In the example above it is described that a window is moved from a first position to a second position. It will be clear that for resizing a window the method according to the invention is also applicable. Since then also first visual data is to be displayed on a further portion of the display device being different from the first portion of the display device.

It will be clear that the method according to the invention is also applicable in the case of multiple windows.

It is preferred that during manipulation of the window the display device 300 is switched into single- view mode. Typically the spatial resolution in single-view mode is higher than in most view mode, giving more freedom in putting the window at intermediate positions during movement. During movement of the window a graphics border may be drawn around the window.

Fig. 3 schematically shows an embodiment of the switchable display device 300 according to the invention. The switchable display device 300 is arranged to switch between view modes. In the single- view mode, also called 2D view mode only one image is generated. In other words, in the single- view mode a single view is generated which can be viewed in a viewing cone with a relatively large viewing angle. In the multi-view mode, also called 3-D view mode, multiple images are generated. These images can be viewed in different viewing cones, each having a viewing angle which is substantially smaller than the said viewing cone. For example, the number of views in the multi-view mode is 9. Typically, the viewing cones are such that a viewer which is positioned appropriately relative to the display device 300 is presented with a first view to his left eye and a second view, which is correlated to the first view, to his right eye resulting in a 3-D impression.

The switchable display device 300 is arranged to switch completely or only partially, i.e. the entire display device 300 is in the single-view mode or the multi-view mode, or alternatively a first portion of the display device 300 is in the single- view mode while a second portion is in the multi-view mode. For instance, most of the display device is in single- view mode, while a window is in multi-view mode or vice versa.

The display device 300 comprises: a receiving unit 302 for receiving an information signal which is provided at the input connector 306, the information signal comprising visual data; a light generating unit 308 for generating light on basis of the information signal; an optical directing unit 310 for transferring the generated light in dependence of an actual view mode of the display device or actual view mode of a portion of the display device; an image rendering unit 312 which is arranged to compute driving values to be provided to the light generating unit 308 on basis of the information signal as received by the receiving unit 302; and a detection unit 304 for detecting the actual view mode of a portion of the display device.

The information signal has a format comprising structured elements having respective luminance values and optionally corresponding distance indicators. For instance the information signal is a video signal with an RGBD format. It should be noted that luminance is represented by the RGB components. The D (depth) component corresponds to distance indicators. Alternatively the YUVD format is used to provide the display device 300 with input. The information signal may be a broadcast signal received via an antenna or cable but may also be a signal from a storage device like a VCR (Video Cassette Recorder) or Digital Versatile Disk (DVD).

The light generating unit 308 comprises a matrix of light generating elements which are modulated on basis of a driving signal which is based on luminance component of the visual data. Preferably the light generating unit 308 is based on an LCD.

The optical directing unit 310 may be based on controllable parallax barriers. With controllable is meant that the amount of light absorption is not fixed. For instance in a first state the parallax barriers are turned off, meaning that they do not absorb the generated light. In that first state the switchable display device 300 is in the single- view mode. In a second state the parallax barriers are turned on, meaning that they absorb the light in certain directions. In that second state the switchable is device 300 is in the multi-view mode. Optionally, the position of the parallax barriers is controllable, enabling directing light in response of eye tracking.

Preferably, the optical directing unit 310 is based on lenses. In order to switch between the single- view mode and the multi-view mode the optical directing unit 310 optionally comprises a diffuser. Alternatively, the optical directing unit 310 comprises switchable lenses or comprises means which are arranged to cooperate with the lenses arranged to compensate for the effect of the lenses.

The image rendering unit 312 is arranged to compute driving values to be provided to the light generating unit 308 on basis of the information signal as received by the receiving unit 302. The driving values may be directly based on luminance values of the information signal. That means that there is a one-to-one relation between luminance values as received and output values of image rendering unit 312. In that case the image rendering unit is simply passing values. However, there may be a difference in image resolution between the image data as received and the resolution of the image display device. In that case an image scaling is required.

It may also be that the image data as received comprises a single- view and corresponding depth values but a multi-view mode is required. In that case a number of additional views must be computed on basis of the single- view as received and the corresponding depth values, i.e. distance indicators. An example of this type of rendering are described in the article "Synthesis of multi viewpoint images at non-intermediate positions" by P. A. Redert, E. A. Hendriks, and J. Biemond, in Proceedings of International Conference on Acoustics, Speech, and Signal Processing, Vol. IV, ISBN 0-8186-7919-0, pages 2749- 2752, IEEE Computer Society, Los Alamitos, California, 1997. Alternatively, the rendering is as described in "High-quality images from 2.5D video", by R.P. Berretty and F.E. Ernst, in Proceedings Eurographics, Granada, 2003, Short Note 124.

The detection unit 304 is arranged to detect the actual view mode for each sub-' pixel, i.e. independently controllable light generating element of the light generating unit 308 on basis of the information signal as provided at the input connector 306. That means that the switchable display device according to the invention is arranged to receive view mode information and the visual data by means of the same input connector 306. Preferably the detection is based on the values of the corresponding distance indicators in the information signal. If the values are in a first predetermined range, then the corresponding sub pixels have to be rendered in single- view mode. If the values are in a second predetermined range, than the corresponding sub pixels have to be rendered in multi-view mode. Alternatively the detection unit 304 comprises a control interface 314 via which a view mode signal is provided independent of the information signal comprising the visual data.

The switchable display device according to the invention is arranged to switch the light generating unit 308 and the optical directing unit 310 such that they cooperate as required, i.e. in phase. That means that the image rendering unit 312 provides the light generating unit 308 with driving values corresponding to multi views if the optical directing unit 310 is actually in the multi- view mode and provides the light generating unit 308 with driving values corresponding to the single- view if the optical directing unit 310 is actually in the single- view mode. As said, the driving values may substantially corresponds to the values as directly available in the visual data of the information signal or may be computed by the image rendering unit 312.

Suppose that the information signal as received by the input connector 306 comprises first visual data corresponding to multiple views and second visual data corresponding to a single view, together forming the visual data for covering the entire screen of the display device 300. By means of the detection unit 304 the display device 300 according to the invention establishes that e.g. because of a user input, a movement of a window corresponding to the first visual data will take place. As a result, the display system 300 according to the invention switches entirely to single- view mode. The image rendering unit 312 generates the appropriate driving values corresponding to single view on basis of the received information signal which still may represent multiple views partly. After a while, that may be a predetermined time or after a detection by the detection unit 304 that the movement has stopped, the display device 300 switches back in a state having partly a single- view mode and partly a multi- view mode. The receiving unit 302, the image rendering unit 312 and the detection unit

304 may be implemented using one processor. Normally, these functions are performed under control of a software program product. During execution, normally the software program product is loaded into a memory, like a RAM, and executed from there. The program may be loaded from a background memory, like a ROM, hard disk, or magnetically and/or optical storage, or may be loaded via a network like Internet. Optionally an application specific integrated circuit provides the disclosed functionality.

The switchable display device 300 according to the invention might e.g. be a TV. Optionally the image processing apparatus 300 comprises storage means, like a hard- disk or means for storage on removable media, e.g. optical disks. It should be noted that the display device according to the invention might have more than two viewing modes. Optionally, the display device switching the display mode of the display device to a third first display mode when a signal is received indicating that the first visual data is to be displayed on a third portion of the display device being different from the first portion of the display device. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be constructed as limiting the claim. The word 'comprising' does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several distinct elements and by means of a suitable programmed computer. In the unit claims enumerating several means, several of these means can be embodied by one and the same item of hardware. The usage of the words first, second and third, etcetera do not indicate any ordering. These words are to be interpreted as names.

Claims

CLAIMS:

1. A method of driving a switchable display device (300) which is arranged to display first visual data on a first portion (102) of the display device (300), the first portion (102) being in a first display mode, and to display second visual data on a second portion

(104) of the display device (300), the second portion (104) being in a second display mode which is different from the first display mode, the method comprising switching the display mode of the display device (300) to the first display mode or the second display mode when a signal is received indicating that the first visual data is to be displayed on a third portion

(105) of the display device (300) being different from the first portion (102) of the display device (300).

2. A method as claimed in Claim 1, whereby the first display mode and the second display mode are from a set of display modes comprising single- view mode and multi-view mode.

3. A method as claimed in Claim 2, whereby the first portion (102) is in the single- view mode and the second portion (104) is in the multi-view mode before the switching.

4. A method as claimed in Claim 2, whereby the first portion (102) is in the ' multi-view mode and the second portion (104) is in the single- view mode before the switching.

5. A method as claimed in Claim 3 or 4, whereby the display device (300) is switched to the single- view mode when the signal is received.

6. A method as claimed in Claim 3 or 4, whereby the display device (300) is switched to the multi-view mode when the signal is received.

7. A method as claimed in any of the claims above, further comprising switching the display mode of the third portion to the first display mode and switching a further portion of the display device (300) to the second display mode after a predetermined time after the reception of the signal.

8. A switchable display device (300) which is arranged to display first visual data on a first portion (102) of the display device (300), the first portion (102) being in a first display mode and to display second visual data on a second portion (104) of the display device (300), the second portion (104) being in a second display mode which is different from the first display mode, the switchable display device (300) arranged to switch the display mode of the display device (300) to the first display mode or the second display mode when a signal is received indicating that the first visual data is to be displayed on a third portion of the display device (300) being different from the first portion (102) of the display device (300).

9. A computer program product to be loaded by a computer arrangement, comprising instructions to drive a switchable display device (300) which is arranged to display first visual data on a first portion (102) of the display device (300), the first portion (102) being in a first display mode, and to display second visual data on a second portion (104) of the display device (300), the second portion (104) being in a second display mode which is different from the first display mode, the computer arrangement comprising processing means and a memory, the computer program product, after being loaded, providing said processing means with the capability to switch the display mode of the display device (300) to the first display mode or the second display mode when a signal is received indicating that the first visual data is to be displayed on a third portion of the display device (300) being different from the first portion (102) of the display device (300).