DIRECTIONAL DISPLAY SYSTEM WITH EMBEDDED OBSERVER POSITION INFORMATION IN VIDEO FRAMES

Abstract

The present invention relates to a method for displaying an image in a direction towards an observer observing the image from a viewpoint. The method comprises providing a display system including a tracking system for tracking or detecting the position of the observer, a display screen having a plurality of image pixels for displaying the image, a controller for controlling the direction of light emitted from said display screen, and a processing unit for generating a buffer image from a data source. The method further comprises tracking the observer and generating tracking data to the processing unit, generating the buffer image and embedding the tracking data as embedded data in the buffer image, outputting the buffer image to the display screen and displaying the image on the display screen, and reading the embedded data by the controller and directing light from the display screen in a direction towards the viewpoint.

Claims

1. A method for displaying an image in a direction towards an observer, said observer observing said image from a viewpoint, said method comprising: providing a display system including: a tracking system for tracking or detecting the position of said observer or a part of said observer such as an eye of said observer, a display screen having a plurality of image pixels for displaying said image, a controller for controlling the direction of light emitted from said display screen such that said image being visible from said viewpoint, a processing unit for generating a buffer image from a data source comprising image data for said image, said method comprising: providing said data source, tracking said observer by means of said tracking system and generating tracking data to said processing unit, generating said buffer image and embedding said tracking data as embedded data in said buffer image by means of said processing unit, outputting said buffer image to said display screen and displaying said image by means of said display screen, and reading said embedded data by said controller and directing light from said display screen in a direction towards said viewpoint.

2. A method for displaying an image in a direction towards a first observer, said first observer observing said image from a first viewpoint, said method comprising: providing a display system including: a tracking system for tracking or detecting the position of said first observer or a part of said first observer such as an eye, a display screen having a plurality of image pixels for displaying said image, said display screen configured for displaying said image at a frame rate, a controller for controlling the direction of light emitted from said display screen such that said image being visible from said first viewpoint, a first memory for storing tracking data, said method comprising: tracking said first observer by means of said tracking system and writing tracking data into said memory, displaying said image by means of said display screen, said controller reading said tracking data from said memory while said image being displayed, and directing light from said display screen in a direction towards said first viewpoint, such that said image being visible by said first observer when said observer changing said viewpoint while said image being displayed.

3. The method according to any of the preceding claims, said display system including a processing unit for generating a buffer image from a data source comprising image data for said image.

4. The method according to any of the preceding claims, comprising: providing said data source, generating said buffer image by means of said processing unit, and generating a pointer to said first memory, and embedding said pointer as embedded data in said buffer image by means of said processing unit.

5. The method according to any of the preceding claims, comprising: outputting said buffer image to said display screen, and reading said embedded data by said controller such that said controller being pointed to read from said first memory.

6. The method according to any of the preceding claims, said embedding comprising substituting image data with said pointer in said buffer image such that a number of pixels comprise said pointer data instead of pixel data.

7. The method according to any of the preceding claims, said display system including a second memory for storing tracking data.

8. The method according to any of the preceding claims, comprising: tracking a second observer by means of said tracking system and writing tracking data of said second observer into said second memory, said second observer observing said image from a second viewpoint.

9. The method according to any of the preceding claims, comprising: reading said embedded data by said controller such that said controller being pointed to read from said first memory while said image being displayed to said first observer or said second memory while said image being displayed to said second observer.

10. The method according to any of the preceding claims, said first viewpoint corresponding to an observation angle defined as an angle between the line of sight between an eye of said first observer and a point at said display screen.

11. The method according to any of the preceding claims, said image being displayed in a time window corresponding to the inverse of said frame rate.

12. The method according to any of the preceding claims, said processing unit being a graphical processing unit.

13. The method according to any of the preceding claims, said display system including a plurality of subpixels or a backlight for directing light from said display screen in a direction towards said first viewpoint.

Description

[0015] The advantage of transmitting the information about observation position corresponding to an image as embedded information in the image itself is that this can ensure a high degree of time synchronization between displayed image and the direction the image is displayed in, in a time multiplexed system. Synchronisation of image and directional information is essential to avoid ghosting, as described above in the background section, and using embedded directional information in the image itself varying degrees of latency in the render-to-display pipeline and input/output pipelines of an operating system will not influence synchronization.

[0016] In a configuration of the invention, the image render system 4 may embed only a direction towards an observing object from a point which is fixed with reference to the display 2, for example with reference to the top center of the display. In this configuration, the display 2 may include a sensor for sensing the distance to an observing object in the direction towards an observing object and it may then calculate the position of the observing object in all three dimensions. The advantage of this configuration is that some directional displays may already include such a sensor and the amount of information to be embedded in the image is reduced.

[0017] FIG. 2 shows an example of an image with embedded information. In this example, information about the position of an observing object is encoded as a plurality 6 of clusters of pixels 1-16 in the top ten scan lines of a display, where each cluster 1-16 represents a bit of a 16-bit word position information which may be looked up in a pre-defined table of positions in the display. Hence, 2{circumflex over ( )}16 positions may be selected and they may be stored in a table in the display 2 and in a table in either the object detection system 3 or the image rendering system 4. A closest entry in the table to a detected position may be determined and the corresponding 16-bit word found and embedded. In the display, the 16-bit word may reversely be used to find a corresponding position in the table. The table in the display 2 may be a reverse table of the table used for embedding the 16-bit word.

[0018] The embedded 16-bit word may be retrieved electronically by sampling pixels in the clusters corresponding to the 16 bits. The image may be cropped electronically before it is displayed so the clusters are removed and do not disturb the experience of the image, or it may be mechanically cropped with a physical mask to achieve essentially the same result. Alternatively, the 16-bit word may be retrieved optically from the image, for example using photodiodes located closely to the screen. The photodiodes may be connected to electrical comparators, which may output a high or low voltage depending on if the cluster of pixels are below or above a brightness threshold and hence providing the 16-bit word in binary electrical form. The photodiodes may be mounted on an elongated bar, which simultaneously acts as a mechanical mask for cropping the image so the 16 pixel clusters are not visible. The elongated bar may have a clip on the backside so it can be attached to a display by clicking it on. The elongated bar may comprise a printed circuit board that may comprise the comparators and may further comprise additional circuitry, for example a microprocessor, for performing the above described lookup operation and/or interfacing to a controller of the emission direction of the display 2, for example a controller for a directional backlight, which may already be included in a commercially available automultiscopic display.

[0019] The advantage of this configuration is that an existing commercially available automultiscopic display, can be easily modified to operate with embedded position information in the received video frames as in the above described configurations.

[0020] FIG. 3 shows an alternative configuration of the disclosed invention, where the embedded information comprises references to the memory 7 and the display 2 may obtain data from the memory 7 and use this data for determining a direction of emitted light. The object detection system 3 may update the content of the memory 7, while an image frame is being displayed and the display 2 may obtain retrieved data from the memory 7, while an image frame is being displayed and may adjust the direction of emitted light according to said retrieved data, while an image frame is being displayed. For example, the object detection system may update the content of the memory 7 at a higher frequency than a frame rate of the image render system 4 and the display 2 may retrieve data from the memory 7 at a higher frequency than a frame rate of the display 2. An advantage of this configuration is that distracting observed variations in illumination intensity when the observer 1 is moving at a fast speed relative to the display 2 can be reduced or eliminated without increasing the frame rate.