Voltage control for adjusting the brightness of a screen display

• US 6,271,813 B1
• Filed: 08/30/1996
• Issued: 08/07/2001
• Est. Priority Date: 08/30/1996
• Status: Expired due to Fees

• Current Assignee: Lear Automotive Dearborn, Incorporated (Lear Corporation)
• Original Assignee: Lear Automotive Dearborn, Incorporated (Lear Corporation)
• Inventors: Palalau, Silviu
• Primary Examiner(s): Jankus, Almis R.
• Assistant Examiner(s): Tran, Henry N.
• Application Number:
  US08/705,613
• Time in Patent Office: 1,803 Days
• Field of Search: 345/20, 345/63, 345/77, 345/147, 345/205, 345/76-81, 345/90, 345/207, 345/214
• US Class Current: 345/77
• CPC Class Codes: H04N 5/58 in dependence upon ambient light

Abstract

A method of controlling the brightness level of a screen display having a matrix of pixels that each have a brightness level controlled by a first and second voltage includes maintaining the first voltage of each pixel at a preselected voltage level. The second voltage level is controlled and adjusted depending on the ambient light conditions. The second voltage is increased during daytime conditions to increase the brightness of the screen display and decreased during nighttime conditions to decrease the brightness of the display. The ambient light conditions are determined by using a light-sensitive sensor or a manually adjustable control.

Claims

1. A method of controlling the brightness level overall of a screen display having a matrix of screen pixels that each have an individual brightness level controlled by a first and second voltage value, comprising the steps of

(A) maintaining the first voltage applied to columns of all of the pixels at a preselected voltage value;

(B) determining a current screen display brightness level;

(C) determining which one of a plurality of discrete ambient light conditions is currently in effect, wherein each of the plurality of ambient light conditions has a single desired brightness level corresponding thereto;

(D) comparing the current brightness level from step (B) with the desired brightness level corresponding to the ambient light condition from step (C); and

(E) adjusting the second voltage applied to a row each of pixel to a value corresponding to the desired brightness level from step (D) when the current brightness level does not correspond to the desired brightness level from step (D) to thereby adjust the current brightness level of the screen display so that it corresponds to the desired brightness level.

2. The method of claim 1, wherein step (B) is performed by determining the current second voltage level of the screen pixels.

3. The method of claim 2, wherein step (D) is performed by comparing the current second voltage level of the screen pixels to a desired second voltage level associated with the desired brightness level.

4. The method of claim 3, wherein step (E) is performed by changing the current second voltage level to the desired second voltage level when the current second voltage level is not equal to the desired second voltage level.

5. The method of claim 1, wherein step (C) is performed by detecting ambient light intensity in an area near and exterior to the screen using a sensor that is responsive to ambient light intensity.

6. The method of claim 5, wherein the sensor produces a first signal that corresponds to a daytime desired second voltage when the ambient light condition corresponds to a daytime condition and a second signal that corresponds to a nighttime desired second voltage when the ambient light condition corresponds to a nighttime condition.

7. The method of claim 1, wherein step (C) is performed by a user manually manipulating a control to a condition corresponding to the ambient light condition as perceived by the user.

8. The method of claim 7, wherein the control produces a first signal that corresponds to a daytime desired second voltage when the ambient light condition corresponds to a daytime condition and a second signal that corresponds to a nighttime desired second voltage when the ambient light condition corresponds to a nighttime condition.

9. The method of claim 8, wherein step (B) is performed by determining a current second voltage level of the screen pixels and wherein step (D) is performed by comparing the current second voltage level of the screen pixels to the desired second voltage corresponding to the signal produced by the control.

10. The method of claim 9, wherein step (E) is performed by changing the current second voltage level to the desired second voltage when the current second voltage level is not equal to the desired second voltage level.

11. The method of claim 1, wherein the matrix of screen pixels are arranged in a plurality of columns and rows and wherein the first voltage of each pixel is a column voltage and the second voltage of each pixel is a row voltage.

12. The method of claim 1, wherein a difference between the first and second voltage levels defines a total voltage level for each pixel and wherein step (A) is performed by determining a range of second voltage levels within which the second voltage level varies depending on the desired brightness level and selecting the first voltage level such that the total voltage level for each pixel is greater than a threshold voltage level where the screen display has a minimum acceptable brightness level, using the determined range of second voltage levels.

13. The method of claim 1, wherein the plurality of discrete ambient light conditions includes an ambient light condition for daytime, an ambient light condition for twilight and an ambient light condition for nighttime.

14. The method of claim 1, wherein the plurality of discrete ambient light conditions includes only an ambient light condition for daytime, an ambient light condition for twilight and an ambient light condition for nighttime.