Method for adjusting brightness of an electronic visual display

1 . A method comprising:

identifying a luminance-indicating area in a field of view of an image sensor of an electronic device, the electronic device having an associated with electronic visual display;

capturing at least one first image of the field of view by the image sensor;

determining an ambient luminance value for the electronic visual display using the luminance-indicating area of the at least one first image;

adjusting the brightness of the electronic visual display according to the determined ambient luminance value,

wherein the step of identifying the luminance-indicating area in the field of view of the image sensor comprises:

capturing a plurality of second images of the field of view by the image sensor, each second image being taken at a different time of a day, the plurality of second images are captured during a calibration period prior to capturing the at least one first image,

calculating, for each of a plurality of candidate areas within the field of view, a luminance variation metric based on luminance values measured across the plurality of second images, and

analyzing the plurality of second images so as to identify an area of the field of view of the image sensor which has the most stable average luminance level by selecting a candidate area having a minimum luminance variation metric,

wherein the step of determining the ambient luminance value for the electronic visual display comprises:

obtaining a luminance value for each pixel of the luminance-indicating area of the at least one first image, and

obtaining the ambient luminance value by taking an average of the luminance values of all pixels of the luminance-indicating area of the at least one first image; and

storing positional information of the identified luminance-indicating area for subsequent use in determining the ambient luminance value from the at least one first image.

2 . The method as claimed in claim 1 , wherein the plurality of second images of the field of view are each taken at a predetermined time interval.

3 . The method as claimed in claim 2 , wherein the plurality of second images of the field of view are taken respectively at a plurality of predetermined times.

4 . The method as claimed in claim 1 , wherein the plurality of second images of the field of view are taken respectively at a plurality of predetermined times.

5 . The method as claimed in claim 1 , wherein the step of adjusting the brightness of the electronic visual display comprises comparing the ambient luminance value determined for the electronic visual display with a reference luminance value or a reference luminance table.

6 . The method as claimed in claim 5 , wherein the step of adjusting the brightness of the electronic visual display further comprises decreasing the brightness of the electronic visual display to a level corresponding to the ambient luminance value when the ambient luminance value is lower than the reference luminance value.

7 . The method as claimed in claim 6 , wherein the step of adjusting the brightness of the electronic visual display further comprises increasing the brightness of the electronic visual display to a level corresponding to the ambient luminance value when the ambient luminance value is higher than the reference luminance value.

8 . The method as claimed in claim 6 , wherein the step of adjusting the brightness of the electronic visual display further comprises maintaining the brightness of the electronic visual display when the ambient luminance value is equal to the reference luminance value.

9 . The method as claimed in claim 5 , wherein the step of adjusting the brightness of the electronic visual display further comprises increasing the brightness of the electronic visual display to a level corresponding to the ambient luminance value when the ambient luminance value is higher than the reference luminance value.

10 . The method as claimed in claim 9 , wherein the step of adjusting the brightness of the electronic visual display further comprises maintaining the brightness of the electronic visual display when the ambient luminance value is equal to the reference luminance value.

11 . The method as claimed in claim 5 , wherein the step of adjusting the brightness of the electronic visual display further comprises maintaining the brightness of the electronic visual display when the ambient luminance value is equal to the reference luminance value.

12 . The method as claimed in claim 5 , wherein the reference luminance value is a previous ambient luminance value determined based on one or more previously captured first images.

13 . The method as claimed in claim 5 , wherein the reference luminance table comprises a plurality of reference luminance ranges, each range corresponding to a specific brightness level; wherein the step of adjusting the brightness of the electronic visual display further comprises determining a target brightness by identifying which reference luminance range the ambient luminance value falls into; and wherein the step of adjusting the brightness of the electronic visual display further comprises adjusting the brightness of the display to the target brightness.

14 . An electronic device, comprising:

an image sensor having a field of view and configured to take images;

an electronic visual display;

a memory unit storing a computer program comprising program instructions for adjusting brightness of the electronic visual display; and

a processing unit;

wherein upon executing the computer program, the processing unit is to:

identify a luminance-indicating area in the field of view of the image sensor;

command the image sensor to capture at least one first image of the field of view;

determine an ambient luminance value for the electronic visual display using the luminance-indicating area of the at least a first image; and

adjust the brightness of the electronic visual display according to the determined ambient luminance value;

wherein at the step of identifying the luminance-indicating area in the field of view of the image sensor, the processing unit is further to:

command the image sensor to capture a plurality of second images of the field of view of the image sensor, each second image being taken at a different time of a day, the plurality of second images are captured during a calibration period prior to capturing the at least one first image,

calculate, for each of a plurality of candidate areas within the field of view, a luminance variation metric based on luminance values measured across the plurality of second images, and

analyze the plurality of second images of the field of view so as to identify an area of the field of view of the image sensor which has the most stable average luminance level by selecting a candidate area having a minimum luminance variation metric,

wherein the step of determining the ambient luminance value for the electronic visual display comprises:

obtaining a luminance value for each pixel of the luminance-indicating area of the at least one first image, and

obtaining the ambient luminance value by taking an average of the luminance values of all pixels of the luminance-indicating area of the at least one first image; and

store positional information of the identified luminance-indicating area for subsequent use in determining the ambient luminance value from the at least one first image.

15 . The electronic device as claimed in claim 14 , wherein the electronic visual display comprises one or both of:

a liquid crystal display;

a light-emitting diode display.

16 . The electronic device as claimed in claim 14 , wherein the electronic device is associated with a security system.

17 . A non-transitory computer-readable storage medium tangibly encoded with computer-executable instructions, that when executed by a processor, perform a method comprising:

identifying a luminance-indicating area in a field of view of an image sensor of an electronic device, the electronic device having an associated with electronic visual display;

capturing at least one first image of the field of view by the image sensor;

determining an ambient luminance value for the electronic visual display using the luminance-indicating area of the at least one first image;

adjusting the brightness of the electronic visual display according to the determined ambient luminance value;

wherein the step of identifying the luminance-indicating area in the field of view of the image sensor comprises:

capturing a plurality of second images of the field of view by the image sensor, each second image being taken at a different time of a day, the plurality of second images are captured during a calibration period prior to capturing the at least one first image,

calculating, for each of a plurality of candidate areas within the field of view, a luminance variation metric based on luminance values measured across the plurality of second images, and

analyzing the plurality of second images so as to identify an area of the field of view of the image sensor which has the most stable average luminance level by selecting a candidate area having a minimum luminance variation metric,

wherein the step of determining the ambient luminance value for the electronic visual display comprises:

obtaining a luminance value for each pixel of the luminance-indicating area of the at least one first image, and

obtaining the ambient luminance value by taking an average of the luminance values of all pixels of the luminance-indicating area of the at least one first image; and

storing positional information of the identified luminance-indicating area for subsequent use in determining the ambient luminance value from the at least one first image.