WO2012152504A1

WO2012152504A1 - Synchronization of active 3d glasses on a displayed signal

Info

Publication number: WO2012152504A1
Application number: PCT/EP2012/055689
Authority: WO
Inventors: Ben Eitel; Dietmar Schill
Original assignee: Sony Corporation; Sony Deutschland Gmbh
Priority date: 2011-05-11
Filing date: 2012-03-29
Publication date: 2012-11-15

Abstract

The present invention relates to 3D motion picture display system comprising a display device having at least one playback component provided to playback 3D picture or motion picture content, wherein said display device is adapted to output a repetitive feature, and 3D shutter glasses comprising a control unit adapted to control the shutter function of the left and right glasses and a sensor element connected to the control unit and adapted to detect the repetitive feature, wherein said repetitive feature is generated by said playback component.

Description

Synchronization of active 3D glasses on a displayed signal

FIELD OF INVENTION

[0001] The present invention relates to a 3D motion picture display system comprising a display device having at least one playback component provided to playback 3D picture or motion picture content, wherein said display device is adapted to output a repetitive feature, and 3D shutter glasses comprising a control unit adapted to control the shutter function of the left and right glasses and a sensor element connected to the control unit and adapted to detect the repetitive feature. The invention also relates to 3D shutter glasses for a 3D picture or motion picture display device and a method for synchronizing 3D shutter glasses with a 3D display device. BACKGROUND OF THE INVENTION

[0002] 3D motion picture display systems are generally known and typically comprise a TV set and 3D shutter glasses. The TV set allows to playback alternately left and right eye images of, for example, a 3D video. The 3D shutter glasses are adapted to open and close the left and right glasses, such that the left eye image is only seen by the left eye of the viewer and the right image is only seen by the right eye. In order to synchronize the opening and closing of the left and right glasses, the TV set is provided with a signal transmitter transmitting a synchronization signal which is received by the shutter glasses for synchronization. The synchronization signal transmitters are dedicated circuits in the TV set and are used solely for generating and transmitting the synchronization signal.

[0003] Although this technique of synchronization properly works, there is still a demand to make such 3D motion picture display systems less complex and, hence, less expensive.

BRIEF SUMMARY OF INVENTION

[0004] Therefore, one of the objects of the present invention is to provide a 3D motion picture display system which fulfils this demand. Particularly, the 3D motion picture display system should be less complex and, as a result, less expensive.

[0005] This object is solved by the 3D motion picture display system as mentioned above, wherein said repetitive feature is generated by said playback component.

[0006] This means in other words that the repetitive feature is not generated by a dedicated synchronization signal transmitter but by a component which is designed and used for playing back the 3D picture or motion picture content (playback component). Hence, the advantage is that the 3D motion picture display system is less complex, meaning that one component can be omitted, so that the costs are reduced.

[0007] A further considerable advantage is that also display devices which are not equipped with a synchronization signal transmitter may be provided with this synchronization functionality by, for example, a software update, because the playback components used for generating said repetitive feature are already there.

[0008] In a preferred embodiment, the playback component is a display unit for outputting left and right images of the 3D picture or motion picture content.

[0009] Alternatively, the playback component is an audio unit for outputting the audio portion of the 3D picture or motion picture content.

[0010] That is in other words, that in the first case the repetitive feature is an optical signal generated by the display unit and in the second case an audio signal generated by e.g. loudspeakers of the display device.

[0011] In a further preferred embodiment, a light signal generated by said display unit comprises said repetitive feature. Preferably, said repetitive feature is an amplitude and/or phase and/or frequency change of said light signal. More preferably, said light signal is generated by a backlight element, preferably an LED or OLED backlight element, of said display unit.

[0012] That is in other words, that the repetitive feature is generated by the backlight element which is provided in many modern TV sets. The backlight element is continuously switched on and off in synchronization with outputting the left and right eye images. In particular, the backlight element is used to reduce the brightness of the image in a period (transition period) during which the left image changes to the right image and vice versa. [0013] The advantage of this embodiment is that an optical signal is used as the repetitive feature which is not generated for synchronization purposes but already has the proper synchronization timing. Hence, this embodiment allows for using the display device, preferably a TV set, as it is, without incorporating any components dedicated to generate a synchronization signal. Even a software update etc. is not required. It is only necessary to equip the 3D shutter glasses with a sensor being able to detect the repetitive feature, namely the light signal generated by the backlight element.

[0014] In further embodiments, the repetitive feature may be incorporated into the left and right eye images of said 3D video content, for example as a color and/or luminance change between the left and right eye images. For example, said repetitive feature could be generated within a predetermined portion of the images, for example within a margin of the images.

[0015] In a preferred embodiment, said repetitive feature is generated in synchronization with the left/right eye image alternation. That means in other words, that the left and right eye images are, for example, displayed with a frequency of 50 Hz, the repetitive feature is also generated with 50 Hz.

[0016] However, it is conceivable that the frequency of the repetitive feature is a multiple of the image alternation frequency, for example 100 Hz, 150 Hz, 200 Hz, etc., or an integer divisor, for example 25 Hz, 12.5 Hz, etc.

[0017] In any case, the repetitive feature is used by the control unit of the shutter glasses to generate the appropriate synchronization signal with the proper frequency. Preferably, the control unit of the shutter glasses comprises a clock element generating said synchronization signal. More preferably, the clock element comprises a phase locked loop circuit adapted to receive the detected repetitive feature and to generate said synchronization signal in response thereto. [0018] In a further preferred embodiment, the 3D shutter glasses comprise an image analyzing element adapted to extract said repetitive feature from the images received by the sensor element.

[0019] That is in other words, that the repetitive feature is incorporated into or is part of the displayed image. The repetitive feature should be detectable by the image analyzing element but should not be recognizable by the viewer.

[0020] In a further preferred embodiment, said shutter glasses comprise a reverse unit adapted to shift the synchronization signal by an image alternation cycle, so that the shutter function of the left and right glasses of the shutter glasses is reversed. Preferably, said reverse unit comprises a switch element adapted to manually shift the synchronization signal.

[0021] The repetitive feature is mainly used to generate a synchronization signal for opening/closing the left and right glasses of the 3D shutter glasses. However, the repetitive feature does not contain "information" whether the left glass or the right glass should be opened (referred to as "left/right synchronisation" in the following). Hence, it might be that the viewer sees the left eye image with the right eye and vice versa. The reverse unit now allows for shifting the synchronization signal. If the user sees the right eye image with the left eye, he can operate the reverse unit, e.g. the switch element, so that the viewer then sees the right eye image with the right eye.

[0022] In a further preferred embodiment, said reverse unit comprises a disparity and/or 3D ghost image estimation element adapted to estimate the optimum shutter timing and to shift the synchronization signal in response to the estimated result.

[0023] This means in other words, that switching to the proper left/right synchronization is achieved automatically and not by operating a switch as mentioned above. [0024] There are several possibilities to detect the proper left/right synchronization, some of which are defined in the dependent claims.

[0025] As already mentioned above, said display device preferably is a TV set. However, the display device may also be a beamer, a notebook/laptop, a desktop PC, a workstation, a game pad, a tablet computer, a remote control or a photo/video camera.

[0026] The object of the present invention is also solved by 3D shutter glasses for a 3D picture or motion picture display device, said 3D display device having a playback component provided to playback 3D picture or motion picture content, wherein said display device is adapted to output a repetitive feature, said 3D shutter glasses comprising a control unit adapted to control the shutter function of the left and right glasses, and a sensor element connected to the control unit and adapted to detect said repetitive feature output by said playback component, wherein said control unit comprises a synchronization signal generating element adapted to generate a synchronization signal on the basis of the repetitive feature.

[0027] Preferably, said control unit is adapted to detect said repetitive feature output by a display unit (the 3D display device). More preferably, said sensor element is a light sensitive element and/or an audio sensitive element. Preferably, said light sensitive element is a photodiode or a CCD sensor.

[0028] The advantages of these embodiments have already been explained above in connection with the 3D motion picture display system according to the present invention.

[0029] In particular, it is to be mentioned that the electronic design necessary for detecting the repetitive feature and for generating the synchronization signal for controlling the shutter function is relatively simple and, hence, very cost-effective. [0030] In a preferred embodiment, the 3D shutter glasses comprise an image analyzing element adapted to extract said repetitive feature from the images received by the sensor element.

[0031] This solution requires a bit more circuitry but is more flexible with respect to the possibilities to transmit a repetitive feature.

[0032] In a preferred embodiment, the 3D shutter glasses comprise a reverse unit adapted to shift the synchronization signal by an image alternation cycle, so that the shutter function of the left and right glasses of the shutter glasses is traversed. A last complex solution is to provide a switch element at the 3D shutter glasses, so as to manually shift the synchronization signal. However, other solutions are also conceivable, in particular solutions for automatically shifting the synchronization signal on the basis of information transmitted by the display device.

[0033] Such information could be transmitted by changing certain parameters of the light or audio signal used as repetitive feature.

[0034] The object of the present invention is also solved by a method for synchronizing 3D shutter glasses with a 3D display device, said 3D display device comprising a playback component provided to playback 3D picture or motion picture content, wherein said display device is adapted to output a repetitive feature, the method comprising the steps: detecting said repetitive feature output by the playback component, and generating a synchronization signal on the basis of the detected repetitive feature.

[0035] The advantage of such a method has already been explained in connection with the 3D motion picture display system, so that it is refrained from repeating these advantages. [0036] In a preferred embodiment, said repetitive feature is a light signal generated by said playback component, preferably a backlight element, more preferably an LED or OLED backlight element.

[0037] Additional information could be incorporated into the light signal and used to indicate whether the left or right eye glass has to be opened/closed. The information is hence a left/right synchronisation information.

[0038] Such additional information could be delivered by changing a color and/or luminance between the left and right eye images. Of course, this additional information could also be delivered by changing an amplitude and/or phase and/or frequency of a light signal or an audio signal.

[0039] Further preferred embodiments of the invention are defined in the dependent claims. It shall be understood that the claimed 3D shutter glasses, the method for synchronizing 3D shutter glasses, the claimed computer program and the claimed computer-readable medium have similar and/or identical preferred embodiments as the claimed system and as defined in the dependent system claims.

[0040] To sum up, the present invention is based on the idea to use a repetitive feature which is generated by a playback component, namely a component designed for playing back 3D picture or motion picture content. The use of a component which a display device already has, allows for omitting a dedicated transmitter for transmitting a synchronization signal. In a preferred embodiment, the idea is further enhanced by using a signal which is generated for the playback process and which already has the proper timing (light emitted by the backlight element of the display unit).

BRIEF DESCRIPTION OF DRAWINGS [0041] These and other aspects of the present invention will be apparent from and explained in more detail below with reference to the embodiments described hereinafter. In the following drawings

Fig. 1 shows a schematic block diagram of a 3D motion picture display system according to the present invention;

Fig. 2 shows a schematic block diagram of a control unit of 3D shutter glasses;

Fig. 3 shows a diagram for explaining the generation of synchronization signals; and

Fig. 4 shows a schematic diagram of the backlight timing of a display device.

DETAILED DESCRIPTION OF THE INVENTION

[0042] In Fig. 1 , a display system is schematically shown in form of a block diagram and is indicated with reference numeral 10. For clarity reasons, the block diagram shows only those components which are relevant for explaining the invention.

[0043] The display system 10 comprises a display device 12 which is in this embodiment a TV set 13. However, as already mentioned before, the display device 12 may also be a beamer or any other device being able to playback 3D picture or motion picture content.

[0044] Generally, the display device 12 comprises components which are directly or indirectly involved in producing pictures or motion pictures and the associated audio signal. Such components are indicated as playback components in the context of the present application. [0045] One of the playback components is a display unit 14, typically provided as an LCD panel 16 and a backlight panel 18. The functions of an LCD panel 16 and a backlight panel 18 are generally known, so that it is refrained from explaining the functions in detail.

[0046] The display device 12 further comprises a controller 20 which is adapted to control the LCD panel 16 and the backlight panel 18, for example. In particular, the controller 20 is, for example, used to switch on/off the backlight panel 18. It is to be noted here that the controller 20 may comprise a plurality of separate circuits and it is not necessarily one element, as shown in Fig. 1.

[0047] The display device 12 further comprises an audio unit 22 which is adapted to provide at least one loudspeaker 24, preferably two or more loudspeakers, e.g. of a surround system, with the appropriate audio signals. The audio unit 22, in turn, receives control signals from the controller 20.

[0048] All components mentioned above are directly involved in producing an image displayed via the LCD panel 16 or an audio signal via the at least one loudspeaker 24 and are therefore playback components.

[0049] The display system 10 further comprises so-called 3D shutter glasses 30 which are used to watch 3D picture or motion picture content. As it is generally known, one of the concepts of presenting 3D content is to alternately presenting left eye and right eye images on the LCD panel 16. The shutter glasses are now designed to inhibit that the viewer sees the left image also with his right eye and the right image also with his left eye. The shutter glasses 30 comprise controllable left and right glasses 32L, 32R. Both glasses 32L, 32R can be electrically toggled between a closed and an open state. In the open state, the glasses are transparent, whereas in the closed state the glasses block (polarized) light from passing through. [0050] In order to control the open/closed states of the glasses 32L, 23R, the 3D shutter glasses 30 comprise a control unit 34 which is adapted to generate a control signal L for the left glass 32L and a control signal R for the right glass 32R.

[0051] As it is known, the control unit 34 requires a signal from the display device 12 to synchronize the control of the glasses 32L, 32R with the display of the left and right eye images on the LCD panel 16. In prior art solutions, this synchronization was achieved by a dedicated transmitter in the display device 12 which transmitted synchronization signals to the 3D shutter glasses 30. The dedicated transmitter in the display device 12 was a separate component not involved in reproducing an image on the LCD panel 16 or an audio signal via the loudspeakers. Hence, in the terminology of the present application, such a dedicated transmitter would not be a playback component.

[0052] In Fig. 2, a control unit 34 being part of the 3D shutter glasses 30 is schematically shown. The control unit 34 comprises a sensor element 36, preferably a photodiode or a CCD sensor 37 and provided at the front side of the shutter glasses 30. In operation, the sensor element 36 must be directed to the display device 12, particularly to the LCD panel 16.

[0053] The sensor element 36 is coupled with a detecting element 42 which is adapted to evaluate and/or analyze the signal transmitted by the sensor element 36.

[0054] The detecting element 42 is, in turn, coupled to a synchronization signal generating element 44 which is adapted to generate a synchronization signal for controlling the left and right glasses 32L and 32R.

[0055] The synchronization signal produced by the synchronization signal generating element 44 is transmitted to a reverse unit 46, as shown in Fig. 2. The reverse unit 46 is adapted to open/close either the left glass 32L or the right glass 32R on the basis of the synchronization signal. [0056] For example and as shown schematically in Fig. 3, a first synchronization signal SI is used to open the right glass 32R, whereas the next synchronization signal S2 is used to open the left glass 32L (it is of course without saying that, if one of the glasses is in the open state, the other glass is in the closed state). The next synchronization signal S3 would then again open the right glass 32R, and so on.

[0057] It can be seen that the synchronization signal S does not contain any information whether the left or the right glass 32L, 32R should be opened. This necessary information is provided by the reverse unit 46 either manually by the user or automatically.

[0058] In order to provide this left/right synchronisation information, the control unit 34 comprises a switch 48 which is coupled to the reverse unit 46.

[0059] By using this switch 48, the user/viewer can generate a signal R, as shown in Fig. 3, which causes the reverse unit 46 to open the same glass as with the preceding synchronization signal. The result is, as clearly shown in Fig. 3, that the same glass, here the right glass 32R, is opened again. In other words, the alternating process of opening/closing the left and right glasses is interrupted by operating the switch 48 and is, thereby, shifted by one synchronization cycle (a period between following synchronization signals S).

[0060] Assuming, for example, that the display device 12 displays the left eye image when the synchronization signal SI is generated, causing the opening of the right glass 32R, there is wrong left/right synchronization between the display device 12 and the shutter glasses 30. This wrong left/right synchronization is maintained unless the user operates the switch 48. With the operation and the generation of signal R, the reverse unit 46 repeats the control signal of the preceding cycle, so that the same glass, here the right glass 32R, is opened. Then, the shutter glasses 30 are in left/right synchronization with the display device 12. [0061] As already mentioned briefly before, the sensor element 36 receives a signal from the display device 12 which is used for generating the synchronization signal S. This signal transmitted by the display device 12 is generated by a playback component in general. That is in other words, that this signal is not generated by a dedicated transmitter.

[0062] In a preferred embodiment which will be described below, the signal is generated in the process of playing back the 3D picture or motion picture content. When playing back 3D motion picture content, the display device 12, preferably a TV set 13, makes use of the backlight panel 18, preferably an LED or OLED backlight, in order to improve the picture quality. When it comes to 3D content transmission, the backlight panel 18 is periodically switched on and off to increase the light level during displaying of the left and right images and to reduce the light level during "transition" periods TP, as shown in Fig. 4.

[0063] In other words, the backlight panel 18 produces a light signal having a reduced light level during transition periods TP and a high or boost level during the other periods. The normal operation of the backlight panel 18, therefore, inherently contains a repetitive structure or feature which, on the one hand side, is detectable by the sensor element 36 of the shutter glasses 30 and, on the other hand side, is proportional to the left and right eye image alternation rate.

[0064] The sensor element 36, preferably a photodiode 37, is able to detect the light boosts generated by the backlight panel 18, so that the synchronization signal generating element 44 can derive a stable synchronization signal S therefrom. For example, as shown in Fig. 4, at time the sensor element 36 detects the light boost, resulting in the generation of the synchronization signal SI, as shown in Fig. 3. At time t₂, the sensor element 36 again detects a light boost, and the synchronization signal generating element 44 generates the synchronization signal S2. [0065] Since the light boost function is not changed during the playback of 3D motion picture content, this function with the repetitive feature of light boosts can be used for synchronization purposes without the necessity to provide dedicated circuits.

[0066] The use of the backlight panel 18 to gain synchronization information is one of the preferred embodiments. However, other approaches are also conceivable to use a playback component to produce a repetitive feature detectable by the sensor element 36, and in response thereto to generate the synchronization signal.

[0067] For example, the LCD panel 16 could also be used to generate/produce a feature in a repetitive and stable manner. Picture elements or patterns displayed by the LCD panel 16 at, for example, predetermined positions and not recognizable by the viewer, could be an approach.

[0068] Besides transmitting such a repetitive feature optically via the backlight panel 18 or the LCD panel 16, it would also be conceivable to transmit a repetitive feature via the loudspeakers 24. In this case, the signal should lie outside the audible range, so that this repetitive feature does not distract or impair the viewer.

[0069] In any case, the sensor element 36 is adapted accordingly. If the repetitive feature is transmitted optically, the sensor element 36 is a CCD sensor or a photodi- ode, and if the repetitive feature is transmitted acoustically, the sensor element 36 is a microphone. The detecting element 42 and the synchronization signal generating element 44 of the control unit 34 are also adapted to the respective signal. For example, if the repetitive feature is a picture element or pattern displayed on the LCD panel 16 at a predetermined position, the detecting element 42 and the synchronization signal generating element 44 have to be able to perform a picture analysis which is, of course, more complex than detecting a light boost, as explained above with respect to the preferred embodiment. Nevertheless, also these approaches allow for using just the playback components of the display device 12 and they do not require any dedicated transmitters just for generating and transmitting the respective signal received by the sensor element 36 of the 3D shutter glasses 30.

[0070] As also mentioned above, the user/viewer can shift the left/right synchronization by switching the switch 48. However, other possibilities are also conceivable which operate automatically.

[0071] Such an automatic operation requires that the display device 12, in particular the playback components, transmit respective left/right synchronization information. For example, as one possibility to avoid a misinterpretation between left and right eye control of the 3D shutter glasses 30, the backlight transmitted by the backlight panel 18 can be modulated for the left and right eye image, such that the images can be easily distinguished from each other. The modulation may, for example, be realized by a different shape, amplitude and/or duration of the light boosts or pulses transmitted by the backlight panel 18. These modifications might be only applied to the invisible spectrum (infrared, ultraviolet) of the backlight panel 18.

[0072] Another idea of transmitting the left/right synchronization information is to use all or part of the displayed content on the LCD panel 16, either exclusively or non- exclusively, for the transmission of such information. One example is to define a frame around the motion picture (video) signal and to set a different color and/or luminance for the right eye image and the left eye image.

[0073] A further possibility is to use slightly different display duration for the left eye image and the right eye image, such that there is no visible video degradation for the viewer.

[0074] In all cases, the sensor element 36 and the control unit 34 with the detecting element 42 and the synchronization signal generating element 44 are adapted to evaluate or analyze such transmitted information. [0075] In Fig. 2, the reverse unit 46 comprises a disparity/3D ghost image estimation element 50 which is adapted to analyze the left and right eye images directly received from the sensor element 36 or the detecting element 42 (via a direct signal path between the detecting element 42 and the reverse unit 46, the path not being shown in Fig.2) and to evaluate the disparity contained in a pair of left and right eye images. In response to such an evaluation, the reverse unit 46 may shift the left/right synchronization. As an alternative to a direct signal path, it would also be possible that the image estimation element 50 receives the necessary signals from element 44 which may additionally forward the left/right synchronisation information (if available) to the reverse unit 46.

[0076] It is to be noted here that the described embodiments and approaches may be combined and used arbitrarily.

[0077] The invention has been illustrated and described in detail in the drawings and foregoing description, but such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0078] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0079] A computer program may be stored / distributed on a suitable non- transitory medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. [0080] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. 3D motion picture display system comprising

a display device having at least one playback component provided to playback 3D picture or motion picture content, wherein said display device is adapted to output a repetitive feature, and

3D shutter glasses comprising a control unit adapted to control the shutter function of the left and right glasses and a sensor element connected to the control unit and adapted to detect the repetitive feature,

wherein said repetitive feature is generated by said playback component.

2. The system of claim 1, wherein the playback component is a display unit for outputting right and left images of the 3D picture or motion picture content.

3. The system of claim 1, wherein the playback component is an audio unit for outputting the audio portion of the 3D picture or motion picture content.

4. The system of claim 2, wherein a light signal generated by said display unit comprises said repetitive feature.

5. The system of claim 4, wherein said repetitive feature is an amplitude and/or phase and/or frequency change of said light signal.

6. The system of claims 2, 4 or 5, wherein said light signal is generated by a backlight element, preferably an LED or OLED backlight element, of said display unit.

7. The system of claim 1, wherein said repetitive feature is incorporated into the left and right eye images of said 3D video content.

8. The system of claim 7, wherein said repetitive feature is a colour and/or luminance change between the left and right eye images.

9. The system of claim 8, wherein said repetitive feature is generated within a predetermined portion, preferably a margin of the images.

10. The system of any of the preceding claims, wherein said repetitive feature is a spread spectrum signal contained in the left and right eye images.

11. The system of any of the preceding claims, wherein said repetitive feature is generated in synchronisation with the left/right eye image alternation.

12. The system of any of claims 1 to 10, wherein said repetitive feature is generated with a frequency which is an integer multiple or an integer divisor of the left/right eye image alternation rate.

13. The system of any of the preceding claims, wherein said control unit of said shutter glasses comprises a clock element generating said synchronisation signal.

14. The system of claim 13, wherein said clock element comprises a phase-locked loop circuit adapted to receive the detected repetitive feature and to generate said synchronisation signal in response thereto.

15. The system of claim 1, wherein an audio signal generated by said audio unit comprises said repetitive feature.

16. The system of any of the preceding claims, wherein said sensor element of the shutter glasses is a light sensitive element, and/or an audio sensitive element.

17. The system of claim 16, wherein said light sensitive element is a photodiode or a CCD sensor.

18. The system of claim 16 or 17, wherein said 3D shutter glasses comprise an image analysing element adapted to extract said repetitive feature from the images received by the sensor element.

19. The system of any of the preceding claims, wherein said shutter glasses comprise a reverse unit adapted to shift the synchronisation signal by an image alternation cycle so that the shutter function of the left and right glasses of the shutter glasses is reversed.

20. The system of claim 19, wherein said reverse unit comprises a switch element adapted to manually shift the synchronisation signal.

21. The system of claim 19, wherein said reverse unit comprises a disparity and/or 3D ghost image estimation element adapted to estimate the optimum shutter timing and to shift the synchronisation signal in response to the estimation result.

22. The system of claim 19, wherein said reverse unit comprises an image analysing element adapted to detect a second feature indicating a shift of the synchronisation signal.

23. The system of claim 22, wherein said second feature is a light signal generated by the backlight element or a signal contained in the left and/or right eye images.

24. The system of any of the preceding claims, wherein said display device is one of a TV set, a beamer, a notebook/laptop, a desktop PC, a work station, a game pad, a tablet computer, a remote control, a photo/video camera.

25. 3D shutter glasses for a 3D picture or motion picture display device, said 3D display device having at least one playback component provided to playback 3D picture or motion picture content, wherein said display device is adapted to output a repetitive feature, said 3D shutter glasses comprising a control unit adapted to control the shutter function of the left and right glasses, and a sensor element connected to the control unit and adapted to detect said repetitive feature output by the playback component, wherein said control unit comprises a synchronisation signal generating element adapted to generate a synchronisation signal on the basis of the repetitive feature.

26. The 3D shutter glasses of claim 25, wherein said control unit is adapted to detect said repetitive feature output by a display unit.

27. The 3D shutter glasses of claim 25 or 26, wherein said sensor element is a light sensitive element and/or an audio sensitive element.

28. The 3D shutter glasses of claim 27, wherein said light sensitive element is a photo- diode or a CCD sensor.

29. The 3D shutter glasses of any of claims 25 to 28, comprising an image analysing element adapted to extract said repetitive feature from the images received by the sensor element.

30. The 3D shutter glasses of any of claims 25 to 29, comprising a reverse unit adapted to shift the synchronisation signal by an image alternation cycle, so that the shutter function of the left and right glasses of the shutter glasses is reversed.

31. 3D shutter glasses of claim 30, wherein said reverse unit comprises a switch element adapted to manually shift the synchronisation signal.

32. 3D shutter glasses of claim 30 wherein said reverse unit comprises a disparity estimation element adapted to estimate the optimum shutter timing and to shift the synchronisation signal in response to the estimation result.

33. 3D shutter glasses of claim 30, wherein said reverse unit comprises an image analysing element adapted to detect a second feature indicating the display of a right or left eye image.

34. Method for synchronising 3D shutter glasses with a 3D display device, said 3D display device comprising at least one playback component provided to playback 3D picture or motion picture content, wherein said display device is adapted to output a repetitive feature, the method comprising the steps:

detecting said repetitive feature output by the playback component, and

generating a synchronisation signal on the basis of the detected repetitive feature.

35. Method of claim 34, wherein said repetitive feature is a light signal generated by said playback component.

36. Method of claim 35, wherein said repetitive feature is generated by changing an amplitude and/or phase and/or frequency of said light signal.

37. Method of claim 35 or 36, wherein said light signal comprising said repetitive feature is generated by a backlight element, preferably an LED or OLED backlight element.

38. Method of claim 34, wherein said repetitive feature is incorporated into the left and right eye images.

Method of claim 38, wherein changing a colour and/or luminance between the left and right eye images generates said repetitive feature.

40. Method of claim 38 or 39, wherein said repetitive feature is generated in a predetermined portion, preferably a frame, of the left and right eye images.

41. Method of claim 34 or 35, wherein a spread spectrum signal is generated containing said repetitive feature.

42. Method of any of claims 34 to 41, wherein said repetitive feature is generated in synchronisation with the left/right eye image alternation.

43. Method of any of claims 34 to 42, comprising the steps of:

detecting the output of the display unit, and

extracting said repetitive feature from said detected output.

44. Computer program comprising program code means for causing a control unit of 3D shutter glasses to perform the steps of said method as claimed in any of claims 34 to 43 when said computer program is carried out on said control unit.

45. Computer readable non-transitory medium having instructions stored thereon which, when carried out on a control unit of 3D shutter glasses, cause the control unit to perform the steps of the method as claimed in any of claims 34 to 43.