White LED Flash White-Balance Compensation
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Solution Overview
Problem
Current camera module control methods are inadequate for white LEDs used as flashes in portable electronic devices, as they deviate significantly from the blackbody curve and exhibit varying color spectra, leading to insufficient illumination and incorrect white-balancing.
Innovation Solution
The method involves transmitting a white-balance patch to redefine the reference white region on a chromaticity chart, allowing for alternate minimum and maximum values and instructions to accommodate the unique characteristics of white LEDs, enabling the camera module to adjust for their changing light levels and spectra.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional camera module control methods are used with white LEDs, then the device structure remains simple, but white-balancing accuracy deteriorates due to deviation from blackbody curve
Solution Approach 1:
The system performs preliminary characterization of the white LED's spectral properties and pre-calculates compensation parameters before actual photography. A reference white region is pre-defined on the chromaticity chart based on the specific LED's characteristics, allowing the camera module to directly apply these pre-computed values during image capture without real-time complex calculations.
Solution Approach 2:
The invention changes the reference white parameters (color coordinates and region boundaries) from standard blackbody curve values to LED-specific values. By adjusting the reference white region definition to match the actual LED emission spectrum, the system compensates for the LED's deviation from blackbody radiation characteristics, thereby improving white-balancing accuracy.
2Illumination intensity
If high power is applied to white LED to achieve sufficient illumination, then illumination intensity improves, but LED damage risk increases
Solution Approach 1:
The system uses periodic pulsing of the white LED rather than continuous high-power operation. By delivering illumination in controlled pulses with appropriate duty cycles, the LED receives sufficient total energy for adequate illumination while having periods of rest that prevent thermal accumulation and extend component life.
Solution Approach 2:
The system incorporates feedback mechanisms to monitor LED performance and adjust power delivery accordingly. By measuring actual illumination output and LED response, the control system can optimize power levels to achieve sufficient brightness while preventing excessive power application that would cause damage.
3Measurement precision
If standard blackbody curve assumptions are used, then algorithm simplicity is maintained, but exposure control accuracy deteriorates for LED flashes
Solution Approach 1:
The invention modifies the exposure control algorithm by changing the reference parameters from blackbody curve values to LED-specific chromaticity values. This involves updating the reference white color coordinates and region boundaries in the algorithm to match the actual LED emission characteristics, enabling accurate exposure control without requiring fundamentally different algorithmic approaches.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for effective white-balancing and exposure control when using white LEDs as flashes, ensuring accurate color representation and preventing damage from high power usage, while accommodating the variability in white LED output.
Implementation Method 1
white LED 207 serving as a flash for taking pictures
Implementation Method 2
white LEDs have a range of color coordinates specifying a range of points that fall substantially distant from the blackbody curve
Data Source
AI summary
A method and an apparatus enabling use of a light source emitting a light of changing intensity and changing spectrum as a flash with a camera module having a white-balance routine and an exposure routine, wherein an initial value representative of a color spectrum emitted by the light source is transmitted to the camera module, the light source is turned on, and the camera module is signaled to scan a plurality of images of the scene while the light source is turned on, allowing the white-balance and exposure algorithms to be employed with each image scanned to refine the first initial value to refine the degree of compensation employed in correcting a color and a light level in the last one of the images of the plurality of images scanned.