Method and apparatus for controlling a camera module to compensate for the light level of a white led

A method of taking a picture of a scene with an electronic device, the electronic device including a camera module and a flash source, the camera module having a pre-determined white-balance routine that includes an initial limit region of a chromaticity chart, the initial limit region of the chromaticity chart overlying a portion of a blackbody radiation curve, the flash source having an optical spectrum lying outside the initial limit region of the chromaticity chart, the method comprising:

• a) modifying the initial limit region of the white-balance routine in accordance with at least one input value to obtain a modified limit region, the modified limit region including at least a portion of the flash source optical spectrum;
• b) receiving, at the camera module, color coordinates of a point on the chromaticity chart, the point being outside the initial limit region and inside the modified limit region, the point to be used by the white-balance routine to define a reference white region, the reference white region excluding any portion of the black body radiation curve;
• c) energizing the flash source to illuminate the scene;
• d) scanning an image of the scene to obtain a scanned image;
• and
• e) white-balancing the scanned image in accordance with the reference white region, to obtain a white-balanced scanned image.

An electronic device capable of taking a picture of a scene, the electronic device comprising:

• a camera module having an image scanning element, the camera module being operable in an ambient light mode in which the image scanning element is controlled to capture and white balance a succession of images, and in a flash illumination mode in which the image scanning element is controlled to capture and white balance a single image, the camera module having a white balance routine and an exposure routine, the white-balance routine including an initial limit region of a chromaticity chart, the initial limit region of the chromaticity chart overlying a portion of a blackbody radiation curve;
• a flash source having an optical spectrum lying outside the initial limit region of the chromaticity chart;
• a processor operationally connected to the flash source and to the camera module;
• and
• a memory having stored thereon instructions for execution by the processor to carry out a method of taking a picture of a scene, the method comprising:
• a) detecting that the flash source will illuminate the scene;
• b) modifying the initial limit region as a function of the optical spectrum of the flash source, to obtain a modified limit region;
• c) defining a reference white region within the modified limit region, the reference white region excluding any portion of the black body radiation curve;
• and
• d) operating the camera module in the ambient light mode by:
• i) energizing the flash source to illuminate the scene;
• ii) scanning an image of the scene to obtain a scanned image;
• iii) white-balancing the scanned image in accordance with the reference white region, to obtain a white-balanced scanned image;
• iv) performing an analysis of the white-balance scanned image;
• v) modifying the reference white region in accordance with the analysis;
• and
• vi) iteratively repeating actions ii-v until a pre-determined stop criteria is met, one of the white-balanced scanned image being the picture of the scene.