SYSTEM AND METHOD FOR BACKLIGHT AND LCD ADJUSTMENT

• US 20100328537A1
• Filed: 06/28/2010
• Published: 12/30/2010
• Est. Priority Date: 06/29/2009
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Smith, Jared, Wan, Chun Chi, Patel, Saagar, Orlick, Christopher, Davies, Trevor, Giaretta, Giorgio
• Granted Patent: US 9,692,946 B2
• Time in Patent Office: Days
• US Class Current: 348/674
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2320/0673 for control of gamma adjustment, e.g. selecting another gamma curve
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: H04N 5/202 Gamma control circuits for controlling camera response irrespective of the scene brightness H04N23/82

Abstract

In one embodiment the present invention includes a display system for displaying video. The display system includes a backlight layer and an LCD layer. The display system controls the backlight layer and the LCD layer to emulate a cathode ray tube response. This emulation may be accomplished by applying a gamma function to a gamma corrected input signal. In this manner, the effects resulting from the “crushed blacks” phenomenon may be reduced.

Claims

1. An apparatus including a circuit for generating video signals for a video display device that includes a liquid crystal display (LCD) layer, the circuit comprising:

a backlight generation circuit that generates a backlight control signal based on an input video signal;

a transfer function circuit that converts the input video signal to a modified input video signal using a transfer function that corresponds to a cathode ray tube (CRT) response;

a LCD correction circuit that generates a LCD control signal based on the modified input video signal and the backlight control signal;

a LCD modification circuit that modifies the LCD control signal, using an inverse characterization of the LCD layer, to generate a modified LCD control signal; and

a controller circuit that controls the video display device according to the backlight control signal and the modified LCD control signal to display an output video signal, wherein the backlight control signal and the modified LCD control signal, in combination, control the video display device to emulate the CRT response.

2. The apparatus of claim 1, further comprising:

a light field simulation circuit, coupled between the backlight generation circuit and the LCD correction circuit, that simulates a light field of the LCD layer according to the backlight control signal, and that provides light field simulation information to the LCD correction circuit,

wherein the LCD correction circuit uses the light field simulation information as the backlight control signal.

3. The apparatus of claim 1, wherein the transfer function circuit implements a gamma function, wherein the gamma function operates on RGB components, and wherein the modified input video signal comprises a linear R, G, B signal.

4. The apparatus of claim 1, wherein the transfer function circuit implements a gamma function with a factor of between 2.2 and 3.0.

5. The apparatus of claim 1, wherein the transfer function circuit implements a gamma function with a factor that is selectable between 2.2 and 3.0.

6. The apparatus of claim 1, wherein the backlight generation circuit generates the backlight control signal to have a mean perceptual light level increased by a factor greater than 1.

7. The apparatus of claim 1, wherein the backlight generation circuit generates the backlight control signal to have a mean perceptual light level increased between 180% and 220%.

8. The apparatus of claim 1, wherein the backlight generation circuit generates the backlight control signal to have a mean perceptual light level increased between 150% and 250%.

9. A system for displaying video signals, comprising:

a backlight layer;

a liquid crystal display (LCD) layer; and

a dual control circuit that generates video signals for the backlight layer and the LCD layer, the dual control circuit including;

a backlight generation circuit that generates a backlight control signal based on an input video signal;

a transfer function circuit that converts the input video signal to a modified input video signal using a transfer function that corresponds to a cathode ray tube (CRT) response;

a LCD correction circuit that generates a LCD control signal based on the modified input video signal and the backlight control signal;

a LCD modification circuit that modifies the LCD control signal, using an inverse characterization of the LCD layer, to generate a modified LCD control signal; and

a controller circuit that controls the backlight layer according to the backlight control signal and that controls the LCD layer according to the modified LCD control signal to display an output video signal, wherein the backlight control signal and the modified LCD control signal, in combination, control the backlight layer and the LCD layer to emulate the CRT response.

10. A method of generating video signals for a video display device that includes a liquid crystal display (LCD) layer, comprising:

generating a backlight control signal based on an input video signal;

converting the input video signal to a modified input video signal using a transfer function that corresponds to a cathode ray tube (CRT) response;

generating a LCD control signal based on the modified input video signal and the backlight control signal;

modifying the LCD control signal, using an inverse characterization of the LCD layer, to generate a modified LCD control signal; and

controlling the video display device according to the backlight control signal and the modified LCD control signal to display an output video signal, wherein the backlight control signal and the modified LCD control signal, in combination, control the video display device to emulate the CRT response.

11. The method of claim 10, wherein the input video signal comprises an input gamma corrected video signal, further comprising:

converting the input gamma corrected video signal, using a gamma function operating on RGB components, to generate the modified input video signal, wherein the modified input video signal comprises a linear R, G, B signal.

12. The method of claim 10, wherein generating the backlight control signal includes:

calculating an average signal level of the input video signal; and

generating the backlight control signal based on the average signal level.

13. The method of claim 10, wherein generating the backlight control signal includes:

increasing a mean perceptual light level of the backlight control signal by a factor.

14. The method of claim 10, wherein generating the backlight control signal includes:

increasing a mean perceptual light level of the backlight control signal by a factor of between 1.8 and 2.2.

15. The method of claim 10, wherein generating the backlight control signal includes:

increasing a mean perceptual light level of the backlight control signal by a factor of between 1.5 and 2.5.

16. The method of claim 10, wherein the transfer function is a gamma function.

17. The method of claim 10, wherein the transfer function is a gamma function calculated using an equation.

18. The method of claim 10, wherein the transfer function is a gamma function calculated using a lookup table.