Patent Application
20080231754
The present invention relates generally to systems and methods for using brightness values to dynamically establish display driver offsets in rear projection TVs having microdisplays with dynamic iris control.
Many modern video displays such as the Sony Grand Wega™ television use three microdisplays, one each for the primary colors of red, green, and blue. Each microdisplay can be, e.g., a liquid crystal display (LCD). To display a picture on the screen, the LCDs are illuminated by a bright lamp and through a set of lenses and prisms the final image is expanded to fill relatively large screens.
As understood herein, it is difficult at best to manufacture LCDs to have precisely uniform thicknesses, and even very small variations in thickness cause non-uniformity in the screen display such that some areas of the screen might appear to be brighter than others or tinged with artificial color. This undesirable appearance is magnified when the output of the LCD is optically expanded as is done in microdisplay televisions.
Accordingly, the present invention recognizes that certain “offsets” must be applied to the drivers of microdisplays. Among the offsets are offsets for uniformity, white balance, and other parameters colloquially referred to as “SCON” and “SBRT”.
As further understood herein, dynamically variable irises have been provided at the input of the microdisplay LCDs to provide improved brightness and contrast expression especially in darker scenes. The present invention critically recognizes, however, that the introduction of dynamically variable irises implicates the need to adjust the driver offsets to optimize display performance during operation of the TV, particularly with an eye to improving what is referred to as “black level” of the display.
A rear projection microdisplay TV with dynamic iris control is disclosed in which brightness level is used to dynamically establish at least one microdisplay driver offset such as but not limited to an offset for uniformity and/or white balance. Average picture level (APL) may be used to dynamically establish the microdisplay driver offset. In non-limiting implementations the APL may be sensed from the DC component of an output of a TV processor.
In another aspect, a rear projection TV has plural microdisplays illuminating a screen, and a display driver controls the microdisplays. Means are provided for dynamically sensing a signal representative of display brightness and generating an output representative thereof. Also, means are provided for sending an offset correction signal to the display driver based at least in part on the output of the sensing means.
In yet another aspect, a signal representative of a demanded brightness of a TV is obtained and used in turn to obtain offset input. The offset input is applied to a display driver to optimize display performance for black level.
The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which:
Referring initially to
The images displayed on the screen 24 can come from one or more sources, including a TV signal source 26 such as a set-top box, cable or satellite head end, etc. as well as various Internet audio-video sources 28. The TV signal source 26 communicates with a TV tuner 30 while the Internet sources 28 may communicate with, e.g., an Internet adapter 32 that is connected to or housed within the housing 12. Audio-video programs are sent from both the TV tuner 30 and, when provided, the Internet adapter 32 to a TV processor 34 as shown.
The TV processor 34 can control the iris controller 20 and, thus, the iris 18 through a logic component 36 that may be an integrated circuit or other logic component for at least in part executing the logic below. As shown, the logic component 36 receives signals from the TV processor 34 and a feedback signal from the iris 18 to send control signals to the iris controller 20.
The TV processor 34 can also send pixel display information to a display driver 38 which in turn drives the microdisplays 14 in accordance with principles known in the art to render a demanded image on the TV screen 24. In the non-limiting embodiment shown, the TV processor 34 may include circuitry that provides viewer control for displaying clear, stable images, as well as circuitry that maintains the integrity of a converted signal by minimizing image loss in the scaling process. The TV processor 34 may also include so-called “reverse pulldown” circuitry, which allows optimum performance of film-based video source displays. As shown in
In accordance with present principles, a sensor of current and/or voltage and/or other parameter representing actual display brightness is provided for purposes to be shortly disclosed. In the embodiment shown in
While the non-limiting embodiment shown in
Now turning to
The offsets may be obtained using a table lookup in which the brightness level is used as entering argument to obtain table values corresponding to one or more offsets. The values may be used in subsequent algorithms to normalize the values. Or, no table per se need be used, but rather empirically-determined values that depend on brightness can be obtained and inserted into offset algorithms that are empirically tailored for the particular TV geometry. For instance, brightness-dependent offset correction values can be obtained from a data store in the TV and added to (or subtracted from) the core offset values for the parameters discussed above. In any case, the brightness-dependent offset corrections are empirically determined to optimize display performance, and specifically to improve black level for various iris positions.
While the particular SYSTEM AND METHOD FOR DYNAMICALLY ESTABLISHING MICRODISPLAY DRIVER OFFSETS USING BRIGHTNESS VALUE IN REAR PROJECTION TV HAVING DYNAMIC IRIS CONTROL is herein shown and described in detail, it is to be understood that the subject matter which is encompassed by the present invention is limited only by the claims.
